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I am evaluting fault in one of my project..but got stuck whether inverters do have reactances or not..if so ( my inverter has an ac capacity of 40kVA and 400 volt)..from this i calculated impedance V^2/P considering unity PF. Is it correct way to find the inverter impedance??. And to obtain PU reactance should i divide by its own base impedance and later change to common base.... OR only divide the obtained impedance by common base impedance????
Looking for answer eagerly..
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Hi Prabesh
I think this page can give you the answers you need.....
Good Luck!
BR Ruud
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I am using spwm and i am not using a low pass filter at the output, so my output consists of multiple harmonics. I am thinking of reducing the voltage to 115V rms(of the complete output not just the fundamental component) by reducing the duty cycle of the pulses. I am able to achieve voltage close to 115V rms in this way. But everyone else is suggesting to use a dc-dc converter first to reduce the input dc voltage and then feed it to the inverter. Why my solution is not good and is it compulsory to use a dc-dc converter first in this situation?
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There are two main ways for reducing the output voltage of an inverter.
1- Changing in modulation index (between 0 to 1)
2- Using a step-down DC-DC converter.
The first solution, imposes maximum voltage stress on inverter switches and can not offer an isolation between input and output ports of the inverter (such as full and half bridge inverters), while, on the flip side, using  an isolated step-down DC-DC converter in conjunction with the inverter not only provides isolation capability and reduction in switch voltage stress but also can drives continous current with low curret ripple from the DC source.
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I'm designing a multilevel inverter using a cascade of two full bridge inverters and when simulating my nonideal model with a dead time seen but switches on my inverter legs do not switch as required with the dead time Id like to know if there is some explanation to what I am experiencing I'm going to attach images of the one leg of my inverter to show the switching sequence Vds_3b and Vds_3A (drain to source of MOSFET) , 3A and 3B (gating signals) Vgs_3A and Vgs_3B (gate to source)
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1. An ideal voltmeter has infinite resistance and no current flows through it.
2. You have the following starting conditions: Q5 is turned off; Q6 is turned on.
Result:
At the moment Q6 turns off, the input capacitance of this transistor is recharged from 15 V to 0, but its output capacitance cannot be recharged, since the output capacitance of Q5 is already charged to the voltage of Vd (voltage source) and the current cannot flow through the output capacitance of Q6. As a consequence, at the moment Q5 turns on, the capacitances of both transistors are recharged and you have an overlap.
But it’s not clear to me the current of -1A at the time of start-up.
I would like to suggest that you connect a resistor with not too much resistance to the output of the inverter (in parallel with the voltmeter) and run the simulation again.
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Dear All,
I am working on hysteresis current controller with the inputs are the reference sinusoidal currents for the three phases and the actual three phase currents. the output of the controller is the gate signal for inverter. when I change the switch on and switch off values in relay block parameters in Simulink, there was no change in the controller performance and gate signals!!! and this against the logic expectations of the change in switching pattern of inverter and then the controller performance. Does anyone help me to know the reasons for this issue and how to solve.
I am grateful in advance.
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I would suggest you check the hysteresis controller rules and the best way is by testing it when it is disconnected from the system. First, apply any value for the sensed current greater than the upper band, then another value less than the lower band. The expected output will be ON or OFF.
Once the hysteresis controller is giving you the desired output, then connect it back to the system for a closed-loop test. Please ensure the band size is correct (try 10% or the rated current) and make sure the sampling time is reasonable, i.e., try different sampling period settings.
Good luck!
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I would like to determine the performance of an installed PV power plant. What is the way foward to do that?
I have measured values of each secondes, minutes of the plant.(batt, PV,Load,weather,ect)
Thanks
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Dear Erika Carmen:
You can benefit from this valuable articles about your topic:
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Also this valuable online calculator:
Also these valuable attached pdf files...
Best wishes...
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I try to regulate in a single phase inverter with different loads, so I get the result that attached, but my question is there any way by changing a PWM technique or by using another method to get pure current signal or can reduce or eliminate the DC component from it..... With great thanks
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You can use adaptive filtering techniques
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We are working on a three phase grid tied inverter(10kW, 415V line, 16A) according to selected switching frequency (50kHz), the calculated inductance and capacitance value for LCL filter to be 340uH, 10uF, 34uH. we tested in hardware this removes the switching frequency ripples. But to link with power grid, whether this inductance value is good enough for power transfer.
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Try modeling in LTspice with different loads. An example is shown in the chart.
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We have 240 V series connected 20 Solar Panels, Each 12 V. Which is connected to grid tied inverter. Is it possible to charge a Solar battery without taking line from grid tied inverter? If yes then how??
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A lead acid battery has a maximum voltage - Vbat, of about 13.7V.
What is the maximum output voltage - Voc, of your solar panel in an unloaded state ?
If Voc >= Vbat then You can use single panel to charge battery (with voltage limitter relay).
If Voc < Vbat You need to use simple Step-Up DC-DC inverter. Try searching on Aliexpress Step-Up DC-DC
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Hi everyone, I am writing my master thesis in grid forming controllers and I am analyzing Power Synchronization Control as one of the Grid forming control methods. I am dealing with some problems when connecting the current limitation so I wanted to as if there is someone here that simulated the same control method and can help me to clarify some questions.
Thank you !
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in islanded mode, if I consider two inverters connected in parallel both working in grid forming mode connected through line impedance what is the procedure of connecting both of them. (How the reference can be created so as to connect them )there may be a phase difference between the two connecting inverters.
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Hello
To connect two inverters in parallel, you need to ensure that the impedance at the output of each inverter is the same (either a resistor or an inductance) to be able to control the active and reactive power simultaneously (because the inverter control can use both), if the impedances are chosen differently, the power sharing between the inverters will be incorrect. (the droop controller parameters change)
To make the impedances equal at the output of the inverters, you can use a virtual impedance (Droop control with Virtual impedance) this is done by adding a control loop to ensure that the output of both inverters is the same.
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While working on SC study on solar plant, I would like to know negative impedance impedance of PV inverters.
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Perhaps you would like to read the following papers:
1-Electrical Fault Calculation | Positive Negative Zero Sequence Impedance. https://www.electrical4u.com/electrical-fault-calculation-positive-negative-zero.
2- What is meant by Sequence Impedance? Positive, …
3-Sequence Impedance of Power System | Elements of Sequence …
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I am trying to measure the losses in the output LC filter inductor of my inverter, This is the method I am using so far; I multiply voltage across the inductor and current through the inductor and take the average over one time period of 1/50. The weird thing i observed is that the loss I calculate with this method comes larger than even the total losses of the inverter. Please see the attached picture for my captured voltage across the inductor and current through it.
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Dean Stewart Thank you for answering my question.
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Hello
Dear researchers
In recent years self-balanced switched capacitor boost Multilevel inverters become a more trending research area. In which the capacitor is connected across the DC source to charge in a short period. But in the practical application how far this is feasible without the current limiting inductor.
1) Maybe in most cases, researchers are assuming the initial capacitor voltage is charged at its rated position. otherwise, it would draw a very high surge current from the input source in starting. In real-time there will be a voltage deterioration when it is not in operation. so if it is switched it will damage the IGBT?
2) I have observed in the MATLAB/ simulation. The switch resistance is considered as 1m.ohms(Ron). Even in normal conditions also the capacitor draws impulses current is nearly 100 times of rated load current. but that impulse is not observed in DSO(oscilloscope) while measuring the capacitor voltage in real-time experimentation may be due to IGBT resistance(it is approximately 14m.ohms).
4) what is the impact of this impulse current on the switch (IGBT) and input DC source during starting and normal conditions? how far this is a problem for the SCMLI.
Thank you for your valuable comments
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hi,
A multilevel inverter is a power electronic device that is used for high voltage and high power application because of its characteristics of generating a sinusoidal voltage based on several DC voltage levels.
A switched capacitor (SC) is an electronic circuit element implementing a filter. It works by moving charges into and out of capacitors when switches are opened and closed. Usually, non-overlapping signals are used to control the switches, so that not all switches are closed simultaneously.
for more info:
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Hi all,
I am modeling a hydrogen-renewable microgrid and want to use average models of converters and inverters to reduce simulation time (my current microgrid model with IGBT and PWM converter and inverter took 2 hours to simulate 24seconds in Simulink, which is too long). Currently, I have successfully modeled the DC DC boost converter and buck converter, however, for the bidirectional DC DC converter, I have not been able to simulate that. So I wondering if someone had done it in the past and be able to send me the simulation file or any document related to this. Thank you guys so much.
Best regards,
Phan Văn Long
P/S: Below is the simulation file with an average model of DC DC boost converter, buck converter and a average model of bidirectional dc dc converter (connect with a pv panel - mppt boost converter)
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Hi,
I hope you are using a non isolated half bridge(Since I can't see the Simulink file I am assuming this). You can do the average modelling of the bidirectional DC-DC converter either considering the boost operation as reference or buck operation as reference depending on your setup and objectives. If you need the technical details you may refer to the following sources:
1. S. Bacha, I. Munteanu, A. I. Bratcu, “Power Electronic Converters Modelling and Control: with case studies”, Springer, vol. 454, 2014.
2. Fulwani, D. K., & Singh, S., "Mitigation of Negative Impedance Instabilities in DC Distribution Systems", Springer Briefs in Applied Sciences and Technology, 2017.
3. M. Mehdi, S. Z. Jamali, M. O. Khan, S. Baloch, and C. H. Kim, "Robust control of a DC microgrid under parametric uncertainty and disturbances," Electric Power Systems Research, vol. 179,p. 106074, 2020.
4. F. Li and Z. Lin, "Novel Passive Controller Design for Enhancing Boost Converter Stability in DC Microgrid Applications," IEEE Journal of Emerging and Selected Topics in Power Electronics, 2021.
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Factors to note: roof position; shadow; arrangement of panels; number of panels.
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Il est plus efficace en général quand il est installé avec un micro onduleur mais le projet peut imposer l'utilisation d'un onduleur
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Dear researchers, Hi everyone.
I am looking for serious and practical collaboration in designing Model Predictive Control (MPC) based Energy Management (MPC-EMS) of a DC Multi-Microgrid system. The system is already operating in Matlab Simulink software and is ready to update.
Add to this, the control should optimize the battery usage (SOC %), and DG fuel consumption (Liters), besides maintaining Bus voltage regulation for both DC Loads and DC-AC inverter (AC load).
I will be happy to meet the interested researchers to schedule the working plan.
Thank you.
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Dear Mohamed,
I really wonder if your optimization could be executed in real-world hardware? Especially when this involves the battery usage and DG fuel consumption.
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I want to design a 30MW Solar Plant connected to grid at 230kV can anyone help me with any article or MATLAB file having its design calculation for inverter, Boost converter and MPPT code, and PWM generator control.
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Dear Ms:
Also you can benefit from this article:
"MATLAB/Simulink-Based Grid Power Inverter for Renewable Energy Sources Integration"
Abstract:
The main objective of the chapter is the development of technological knowledge, based on Matlab/Simulink programming language, related to grid connected power systems for energy production by using Renewable Energy Sources (RES), as clean and efficient sources for meeting both the environment requirements and the technical necessities of the grid connected power inverters. Another objective is to promote the knowledge regarding RES; consequently, it is necessary to bring contribution to the development of some technologies that allow the integration of RES in a power inverter with high energy quality and security. By using these energetic systems, the user is not only a consumer, but also a producer of energy. This fact will have a direct impact from technical, economic and social point of view, and it will contribute to the increasing of life quality.
The chapter intends to integrate itself into the general frame of the EU energy policies by imposing the global objectives of reducing the impact upon the environment, and promoting the RES for the energy production. At the same time, the chapter is strategically oriented towards the compatibility with the priority requirements from some European programmes: the wide-spread implementation of the distributed energy sources, of the energy storage technologies and of the grid connected systems.
The chapter strategy follows two directions: the first, is thedevelopment of knowledge (a study and implementation of a high performance grid-power inverter; the fuel cells technology as RES; the control methods; specific modelling and simulation methods); the second focuses upon the applicative research (a real time implementation with dSPACE platform is provided).
The interdisciplinarity of the chapter consists of using specific knowledge from the fields of: energy conversion, power converters, Matlab/Simulink simulation software, real time implementation based on dSPACE platform, electrotechnics, and advanced control techniques.
Best wishes...
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I am trying to simulate a micro grid and I need an inverter for a DC source. In my method, this inverter must set Id and Iq values as input references and delivers Active and Reactive power of the source to suitable values according to that references. Can someone help me? thanks so much.
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Product of voltage with direct axis component of current are in normal inverter considered ( unity power factor ) but same inverter could be used to supply reactive power using current Iq lead (via capecitance) or Iq lag ( via inductor)with same voltage reference…….
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If i want to build a system with an off-grid inverter for backup reasons, which will only work when a utility loss occurs, and with an on-grid inverter to work normally during grid presence, can i parallel the same PV strings on their PV inputs?
On that case, when there is sun the PV has energy, therefore, it will inject to the grid and at the same time it will charge the batteries through the off-grid inverter.
The AC circuits of both inverters are separated, the only thing in parallel and connected with each inverter are the PV strings.
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Dear Gustavo Gushiken:
It's about Hybrid solar systems:
Hybrid solar systems combine the best from grid-tied and off-grid solar systems. These systems can either be described as off-grid solar with utility backup power, or grid-tied solar with extra battery storage.
If you own a grid-tied solar system and drive a vehicle that runs on electricity, you already kind of have a hybrid setup. The electrical vehicle is really just a battery with wheels.
-- Advantages of hybrid solar systems:
1. Less expensive than off-grid solar systems
Hybrid solar systems are less expensive than off-grid solar systems. You don’t really need a backup generator, and the capacity of your battery bank can be downsized. Off-peak electricity from the utility company is cheaper than diesel.
2. Smart solar holds a lot of promise
The introduction of hybrid solar systems has opened up many interesting innovations. New inverters let homeowners take advantage of changes in the utility electricity rates throughout the day.
Solar panels happen to output the most electrical power at noon – not long before the price of electricity peaks. Your home and electrical vehicle can be programmed to consume power during off-peak hours (or from your solar panels).
Consequently, you can temporarily store whatever excess electricity your solar panels in batteries, and put it on the utility grid when you are paid the most for every kWh.
Smart solar holds a lot of promise. The concept will become increasingly important as we transition towards the smart grid in the coming years.
-- Equipment for hybrid solar systems:
Typical hybrid solar systems are based on the following additional components:
--Charge Controller
--Battery Bank
--DC Disconnect (additional)
--Battery-Based Grid-Tie Inverter
--Power Meter
Battery-based grid-tie inverter:
Hybrid solar systems utilize battery-based grid-tie inverters. These devices combine can draw electrical power to and from battery banks, as well as synchronize with the utility grid.
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Also Equipment for off-grid solar systems
Typical off-grid solar systems require the following extra components:
--Solar Charge Controller
--Battery Bank
--DC Disconnect (additional)
--Off-Grid Inverter
--Backup Generator (optional)
--Solar charge controller
--Solar charge controllers: or charge regulators or just battery regulators. The last term is probably the best to describe what this device actually does: Solar battery chargers limit the rate of current being delivered to the battery bank and protect the batteries from overcharging.
Good charge controllers are crucial for keeping the batteries healthy, which ensures the lifetime of a battery bank is maximized. If you have a battery-based inverter, chances are that the charge controller is integrated.
--DC disconnect switch:
AC and DC safety disconnects are required for all solar systems. For off-grid solar systems, one additional DC disconnect is installed between the battery bank and the off-grid inverter. It is used to switch off the current flowing between these components. This is important for maintenance, troubleshooting, and protection against electrical fires.
--Off-grid inverter:
There’s no need for an inverter if you`re only setting up solar panels for your boat, your RV, or something else that runs on DC current. You will need an inverter to convert DC to AC for all other electrical appliances.
Off-grid inverters do not have to match phase with the utility sine wave as opposed to grid-tie inverters. Electrical current flows from the solar panels through the solar charge controller and the bank battery bank before it is finally converted into AC by the off-grid-inverter.
I hope it will be helpful...
Best wishes...
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Dear researchers,
I am implementing a model for a grid-connected PV-inverter. In the current controller part (see the photo) there are two PI controllers that have an essential effect in calculating the final inverter output. From my trails until now limitations for the PI controllers output are necessary. Has anyone an idea how these limits can be calculated?
Many thanks in advance
Mansour Alramlawi
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The PID controller affects more the dynamics of the inverter when the output current changes from one value to an other value. It affects the rise time, the overshoot and the steady sate error. So, It will not affect much the output current except with the steady sate error value. You choose the different parameters of the PID controllers to shape the dynamic response of the controller while minimizing the steady state error. As for the steady sate value it will be controlled by the reference value.
I would like that you follow the papers in the links:
Best wishes
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Hi,
I am working on a model predictive control of inverter using a Microlabbox or DSpace 1102. Recently, I found that working with Microlabbox beyond 2e-5 us is a tough task. I came to know that, for dSPACE1104, there are slave PWM blocks to working with low sampling rates. But unfortunately, there are no such options in Microlabbox. I am aware of the s-functions based model but looking for an alternative to that. I request you to guide me in working with more complex models such as sample-based controllers at low sampling rates. please share some useful information in this regard.
Thanks in advance.
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These are the ways.
1. Get the supporting software for FPGA programming. Then you can operate a very low sampling rate.
2. Check for the turnaround time in a control desk. So that you can identify and fix the high computations.
3. If you still want any additional details, you can mail me at
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Hi,
SITUATION:
I am trying to recreate something similar to the inverter model contained in:
There is a Droop Controller that feeds a Voltage Regulator that feeds a Current Regulator that powers a LCL filter.
MY PROBLEM:
1. When combining the Voltage and Current state models. A and C is 3x3, B and D are 2x8. I pad them out with redundant zeros to make them all 8x8, unsure if this correct? When I multiply them out as listed in the link below, I lose all the controller information from the Current Regulator, such as the integrator and proportional controller coefficients and the decoupling terms.
2. The Voltage and Current state models share the same inputs as the Droop controllers, so they are not perfectly in series. Is there a strategy to combine state space models that share inputs?
Thanks
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In relation to you query, I would like to suggest you to follow any standard Book of Systems of Control Theory, with focus on linearization, which will enable you how to integrate, combine state space models and how to discretize them etc.,. For good such concepts you may need to follow some book on Matrix Analysis with Applications. A simple computing example: https://kevinkotze.github.io/ts-4-tut/
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Hi,
I am designing a CMOS inverter in the cadence tool, can anyone please tell me how to measure its voltage gain?
Thanks
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In order to operate the inverter as an amplifier you have to bias at the intermediate point of the transfer curve of the inverter where Vi=Vo.
The one can measure the gain by applying a small signal at the input and measure the signal output voltage. Av= vo/vi
As you measure the gain of any amplifier where one input a small sinusoidal input and measure its output.
To bias the transistor you need only to connect a high resistance between the input and the output.
Best wishes
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I was modeling STATCOM in MATLAB/SIMULINK for my research.the overall HVDC research network was performed on DIgSILENT. how can I attach the STATCOM to the AC system bus of the Inverter side of the network system
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If a better way is present you can select that. But I know to model FACTS device in DIGSILENT using user define(UD) model and you can mode as you want. UPC already existed in DIGSILENT you can change some components and use them as you want.
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I have read papers on multilevel inverter feeding BLDC motor drives. My question is BLDC motor having trapezoidal back-emf, is it possible to drive the BLDC motor using an l inverter that gives a perfectly sinusoidal voltage output? Also, I would like to get clarified about the stability of such a drive and torque ripple. I will be grateful to you if you could kindly let me know the significance of such an inverter application to BLDC motor drives.
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Dear Madam
Yes, it is possible, but in that case You have to change control of Your motor.
You have to treat the BLDC as an synchronuous motor and apply frequency control, remebrering of U/f fomula on the output of Your MLI.
You start Your drive with a low frequency and voltage and then You control the speed by changing frequency of supply, adjusting the voltage accordingly.
With such drive You forget the electronic commutator and control the drive directly by the output ferquency of Your MLI.
Best wishes - Piotr Wach, Opole, Poland
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I make a design for a grid-connected LCL filter to be used to connect a single phase inverter to the grid to suppress the injected current harmonics. I would like to know what is the suitable core type to be used for the inductor? Ferrite Cores, powder cores or Tape Wound Cores?
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I also do not consider ferrites' high current power applications. Required air-gap becomes a few cm (considering relatively normal core areas). Then fringing losses becomes considerable. Moreover, for large power applications, the ferrite material is brittle, it has disadvantages in terms of mechanical performance. (Especially if you are considering liquid cooling options.)
I prefer powder cores (as the motivation for distributed air-gap exactly this applications -high currents-). The only downside is that as their relative permeability is low, the turn number for required inductance can be high, increasing winding losses. Copper mass can be a limiting factor. Moreover, most powder cores are pre-determined in shape, so it can be challenging to find the optimum or required shape (considering the ferrite option).
Although you can find some other alternatives like amorphous core [1], [2] but those are suitable for much larger power ratings.
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Dear experts,
I am elaborating on the impact of flicker shading from wind turbines on solar inverters.
Racing shadows from wind turbine blade shadows across a solar field impact the current flow at the DC terminals of an inverter. Depending on configuration - just few or multiple strings per MPP tracker - the inverter would want to follow that fluctuating signal.
  • What is the follow rate of MPP trackers and conversion electronics on such steep change ramps?
  • What is the impact on the inverter life time?
  • What is the recommended design?
(Note: the question is NOT about the impact on the plant performance due to shading losses.)
Many thanks for hints or papers.
Best regards
Ralf
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Dear Ralf:
First of all,as you know the top five things that cause inverter failure:
1- Ultrasonic vibrations:
The first reason for inverter failure is one that contributes to the mechanical stress placed on an inverter. Ultrasonic vibrations originating in the cores of inductive components cause friction, adding to the unwanted heat generated by the device and further damaging components in the inverter.
2- Capacitor wear:
The second reason for inverter failure is electro-mechanical wear on capacitors. Inverters rely on capacitors to provide a smooth power output at varying levels of current; however electrolytic capacitors have a limited lifespan and age faster than dry components. This in itself can be a cause of inverter failure.
Capacitors are also extremely temperature sensitive. Temperatures over the stated operating temperature, often caused by high current, can reduce the life of the component. However, as the electrolytes evaporate faster at higher temperatures, capacitor life increases when they are run at lower than operating temperature.
Happily, keeping a consistent maintenance regime and regularly replacing capacitors avoids most problems that failed capacitors can cause.
3- Overuse:
Using inverters beyond their operating limit, either by choice or due to oversight or lack of knowledge, can contribute to inverter bridge failure. Using any component at a rating higher than its operating limit will decrease its lifespan and lead to failure, so avoiding this issue simply comes down to checking that all inverters are being run correctly.
4- Over- and under-voltage
The next two issues that can cause inverter failure are over-current and over-voltage. If either current or voltage increases to a level that the inverter is not rated for, it can cause damage to components in the device, most frequently the inverter bridge. Often this damage will be caused by the excess heat generated by the spike in voltage or current.
Over-current can be avoided with fuses or circuit breakers but avoiding over-voltage can be tricky. Sometimes voltage spikes are man-made, but they can also be caused by lightning or solar flares which are difficult to avoid if, like us, you live on planet Earth.
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Shading Analysis:
Shading analysis is one of the most essential steps in phase of solar energy system design or analysis. In photovoltaics it is important to analyse shading caused by surrounding objects and/or vegetation. In special cases like analysis or design of BIPV systems, exact analysis of shadow-voltaic systems (overhangs, vertical shading fins, awnings etc.) is also very important. Similar analysis is also part of passive house or solar house design - overhangs must also be planned very carefully in such case. Basic calculations can be done by some simple equations - formulas for some typical simple cases you may find below. Some graphical tools like solar path calculator (pilkington) are also available. For analysis of complex objects several computer tools are available. Some of them offer even 3D simulation. Shading is especially important in photovoltaics. It should be eliminated as much as possible. Even small obstacles like chimneys, telephone poles etc. shouldn't be neglected. To minimise influence of photovoltaic array shading (if shading can not be avoided) different system optimisation techniques can be used.
For more information you can see this Link:
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You may benefit from this article about cloud impact on PV:
"Impact of rapid PV fluctuations on power quality in the low-voltage grid and mitigation strategies using electric vehicles"
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Also you may benefit from these Links:
I hope it will be helpful....
Best wishes....
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Hi,
I am trying to create a full system state space model for an inverter.
References:
Both papers have modelled individual controllers and then combined them to create a full system model.
Both have used the same technique, does anyone have any literature on how they came up with a complete system model, that combines all the state space models into one big one?
Regards,
Sandford
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Dear Sandford:
You may benefit from these articles about your topic:
1- "System Modeling and Reliability Assessment of Microgrids: A Review"
2- "Control Strategy of Microgrid Inverter Based on H∞ State Feedback Repeated Deadbeat Control"
3- "State Space Modelling and Control of the Modular Multilevel Converter".
.. The pdf file.
I hope it will be helpful...
Best wishes...
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why frequency of inverter decreases(while frequency of inverter decided by modulating signal frequency) with increase in load demand ???
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Thanku Sir
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What could be the reason for this distortion and the unsymmetrical nature of the waveform measured on the filter capacitor of LCL filter of grid connected inverter? The voltage at the inverter output is normal. DC input was set at 1.08 pu. Could the problem be from the control as well or limited DC input?
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Lutz von Wangenheim and Ehtisham Lodhi thank you for the response
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Assume we have a microgrid consisting of two inverters
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Dear Shamsher Ansari you are not wrong and I agree that the inverter needs a controllable input. However, this can also be represented by transferfunctions having said that, for example, BESS is considered as an input with sufficient stored energy, only the response characteristics are taken into the account.
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Dear researchers,
I'm trying to implement a two-level three phase inverter.., when I use a three phase resistive load, the output voltage VAN is accurate and it looks like the simulation. However, when I add three inductors to the load (inductive load), the output voltage is distorted and the load current is not sinusoidal (please see the attached images for illustration). I'm using six IGBT transistors IRF G4PC40FD, I think the problem comes from the freewheeling diode of the IGBT transistors. Should I use an antiparallel external diode to eliminate the internal diode of the IGBT ? If yes, please suggest us a practical schematic to get a sinusoidal shape current.
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Due to the inductive load, there is an instant that the voltage polarity becomes positive and in the same time the current polarity is negative. Therefore, the current tries to go back to the DC source. Keep in mind that the IGBT can block small amont of the current, but your IGBT can be damged if the load inductive current increases
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I have two subsystems for a solid state transformer. when the subsystems are not interconnected, they produce the desired results(voltage and current outputs). When the dual active bridge is interconnected with the inverter, unexpected results are achieved. I suspect an issue with the sampling rates of the subsystems. Please help me solve the problem.
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I am trying to use the advanced PID controller(auto-tuning) to control the speed of induction motor drive with FOC. I would like to ask how to get the transfer function for the induction motor and inverter by system identification method. anyone can give me useful information.
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1. Instead of calculating transfer function or transfer function matrix better is to go with the state-space model........
With this type of modeling, then you can use the Kalman filter for identification purposes....
2. If you want to stick with the transfer function model...... it is better to first add a decoupling block to decouple the d-axis and q-axis circuits.....
Then depending on the type of control i.e FOC in your case.....you can easily relate rotor speed with q-xis voltage......for simplification you can make TL=0.....Also, as FOC is implemented so id=constat, meaning d-axis dynamics (or d-axis circuit dynamics) are totally ignored.....meaning as if there is no d-axis circuit.......but mind, it is valid only while decoupling block is used.......
Thus, you will finally have a plant with q-axis voltage as input and q-axis current as output with a cascade block whose input is q-axis current and output is torque developed with cascade block whose input is torque developed and output is rotor speed.....Finally, you can easily close two loops q-axis current and speed loops with two PI controllers to tune......here identification can easily be done by a Neural Network block......
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Voltage state inverter microgrids are used to produce active and reactive power with renewable energy sources. This system is efficient or enough to replace the conventional generation system.
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Hello dear,
Referring to your question, I would say it could replace conventional large-scale power plants with the concept of grid-forming inverters due to most of nowadays renewables are connected to the grid through phase-locked loop (PLL) for synchronization. However, there are various promising scheme to address inertia problem by simply adapting to the new power system paradigm or through adjustment in power electronic-based generators capability to remain connected to the grid even after disturbances to avoid complete shutdown.
There are innovative solutions, but in order to implement any solution, a precise analysis for the total system's inertia should be estimated.
Regards,
Mohammed
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If a photovoltaic power generation system is to be added to the microgrid. The DG will inject active power of 150KW and reactive power of 30KVA into the grid in normal operating conditions. The inverter output voltage is 10KVac and the input voltage is 500Vdc. Use a three-phase inverter. suggest
a)grid-connected inverter for the project
b)control scheme for inverter(VSI)
c)control scheme for islanded necessary conditions
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You can get a lot of published research on this topic.
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If a UPS is feeding a 30KVA data centre. Recommend or suggest
a)Inverter and its control scheme
b)Control scheme for the inverter
c)If another load of 10KVA is added and new UPS is added in parallel with the previous UPS for the new load. What will be the control scheme for the inverter? in this case.
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I am also working on distributive model predictive control for secondary control
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I have three 1-ph inverters and they are needed to be connected to a 3-ph grid. For such, all the three inverter's output voltage must have equal frequencies and 120 degree phase shifted. In other words, they all must be in synchronization. I'm developing a model using Simulink.
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Zawar Khan sure, please share.
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I have completed the simulation of grid tied inverter and got voltage, current, harmonics distortion at PCC but i don't know how to extract features and process the simulation outputs for SVM training and classification in MATLAB
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Also you may take a look at this article:
"A novel Multi-LSTM based deep learning method for islanding detection in the microgrid".
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In most of the research papers SVPWM techniques are used for PMSM and other motors after inverter transformation, instead of the PWM technique can I use Sine PWM techniques for motors?
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Dear Sir,
Thank you for sharing your knowledge...
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I have designed a control law based on sliding mode control for a grid-tied inverter, the controlled variable follows the positive reference values well, but when it comes to negative reference values it doesn't work.
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Thank you to devote your time to address the problem, and discuss it with me. Till next time.
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The DC Voltage is 400 V. The required three phase voltage is 230V, 50Hz.
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Sorry, I did not make myself clear. Duty cycle of motors or equipment is not something you calculate; too many variables; and unique to each piece of equipment. One reads the insulation temperature of the motor or other equipment while running in the warmest location until it gets to the maximum temperature allowed of the wire insulation. As listed in the National Electrical Code; wire insulation max temperatures are generally 90 deg C or 110 deg C and other temperatures I do not remember. The equipment manufacturer generally supplies the max cycle time of the equipment; when it reaches the max
wire insulation temperature; generally between 50% of the operating time to 90% of the operating time; and usually specifies the amount of cool down time before motor restart. Motors and equipment are regularly oversized to allow continuous operation. The equipment manual almost always specifies the the max allowed cycle time. If it does not, the equipment manufacturer is probably not reputable and not reliable; or they do not know what they are doing. Or, it is a one time, one use piece of equipment; dying at the end of its cycle; and needing wiring repair. Large electric motors are commonly rewound after several thousand hours of operation. Motor frames last nearly forever; wiring does not.
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inverter state space model
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Thank you sir
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I am working on a multi-level DC link inverter. I have verified the simulation part in MATLAB/Simulink for R and RL load. when it comes to hardware for R load results are satisfactory, for RL load there is a small voltage dip or surge when the load current crosses zero instant.
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As is not load, it is inherent circuit inductance …….
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I am designing an inverter in Matlab, for desired performance I need to design a close loop model with a PI/PID controller but I am unable to tune the controller gains. Can anybody help me in this regard?
Thanks in advance
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If you are still working with model, you can analyze the characteristic of the model and change the pole location by using PID (Pole location have correlation with transient behaviour [%overshoot, risetime, settling time]). Second way is by using Ziegler-Nichols (ZN) method (open loop or closed loop), you can use simulink to obtain the response and follow the ZN procedure to derive the initial PID parameters (Kp, Ti, Td). Noted that ZN just gives initial parameters, after that you have too tune based on the tuning rule, for example to decrease the overshoot you have to decrease Kp, . increase Td & Ti.
Another alternative way is by using PID tuning rule in Matlab, if you are using this becarefull with PID structure, in Matlab they put filter in derivative part so if you bring this to hardware you have to put filter in error before differentiated.
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Hello,
I am working on a project and we need to use an DC to AC inverter for the battery power supply. I am searching for devices that conver the current and also are capable of controlling the motor. I know that this kind of inverters can regulate the speed. But what about the torque? Does it need to be regulated with a variable resistor? How does it normally work?
Thank you a lot
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I'm reaching out because I wanted to know what are some possible pitfalls if a user wants to create two separate strings to drive a grid-tie inverter as an alternative use of the solar water pumping system? Please note that the user wants this kind of mechanical switching to utilize the solar panels while the water pumping will not be necessary.
I'm working on my project for Solar Water Pumping System and my team and I are looking for whatever information you have.
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welcome,
I revised the connections in the top circuit diagram. You feed the inverter of the water pump by two strings in series. While you feed the two grid inverters by a separate string.
I see that the connections and switching arrangements are okay.
It remains the sizing of the different components and the their protection.
I have one advise that you in switching you have to adjust the switching to affect brake before make in order to grantee isolation of the two systems and consequently their interactions.
Wish you success.
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For example, if the inverter is fed with a 100 kW DC battery and the inverter has to run with 0.9 power factor, it will produce 90 kW of AC power, and the rest 10 kVAr (assuming 100% efficiency of the inverter) will be the reactive power. Here the 10 KVAr is getting generated from the 100 kW DC power. Did I understand correctly?
Is it possible that the inverter will convert all the DC power to real power (100 kW DC to 100 kW AC power) and the necessary reactive power (10 kVAr) can be provided from the auxiliary power supply of the inverter?
Your answer will be highly appreciated. Thank you
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Dear Shaikat:
At the first, and as you know that an inverter is a power electronic device or circuitry that changes Direct Current (DC) electricity from sources such as batteries or fuel cells to Alternating Current (AC).
The input voltage, output voltage, frequency, and overall power handling depend on the design of the specific device or circuitry. The inverter does not produce any power; the power is provided by the DC source.
Power inverters are primarily used in electrical power applications where high currents and voltages are present.
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As for Reactive power is the power needed to keep the electric current flowing, and helps maintain voltage levels that are needed for system stability.
In the same way that we can think of real energy being stored in a battery, it is useful to think of reactive power as being stored within the electric field of a capacitor or the magnetic field of an inductor. To the degree that any circuit shifts the phase of the current to the voltage (and this can only apply to AC circuits), its impedance is said to have a reactive component. So, any circuit, including an inverter, that has an inductive or capacitive component to its impedance is temporarily storing reactive power in one or more of its components. An inverter often has a transformer as part of the circuit that attaches to an AC input and so is often an inductive load from the view of the power company.
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There is also another point to take into consideration which is the Renewable energy sources, such as solar power, provide not only electricity but can also be used to generate reactive power. To prevent blackouts, renewable energy systems also need smart inverters to control the energy flux and manage the passive power of electrical grids.
Reactive power does not do the work of electricity we all know, like lighting a lamp or heating water. Instead, the AC system consumes reactive power to keep electricity flowing.
As the amount of electricity flowing on a line increases, so does the amount of reactive power needed to move the additional electricity and maintain the proper voltage. The longer the distance power moves on a line, the more reactive power is consumed. When reactive power is insufficient, voltage drops. If it continues to drop, protective equipment will shut down affected power plants and lines to protect them from damage.
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As for the main point of your issue:
"How Power Inverter Generates Reactive Power" ... we can say the following:
We can use an inverter for reactive power generation. To deliver reactive power only, the voltage source connected to the main grid through a reactance has to generate a voltage in phase with the grid voltage but with higher amplitude. To absorb reactive power, it will generate a voltage still in phase with the grid voltage but with a lower amplitude.
Inverters generate reactive power by use of the freewheeling diodes on each of the power switches. The inductive nature of the load makes it want to draw current even after the power switch has been turned OFF. The load is shown as an induction motor but maybe the primary of a three-phase transformer or any other AC load. For an inverter to handle reactive power it must have the ability to run backward and absorb the reactive energy. This technology is called four-quadrant operation. The inverter can provide reactive power based on a function of the entire size of the inverter, not just on the level of generation. So, if cloudy skies drop solar generation from 100 percent to 10%, the inverter can use the other 90% of its remaining capacity to supply reactive power support and enhance utility grid power quality.
Reactive power control can be implemented in several ways – inverters can either be set to supply a specific ratio of active to reactive power, or set to dynamically match the reactive power requirements of the load as these change over time.
Inverter apparent power capacity is measured in Volt-Amps (VA). Historically, when inverters operated at unity power factor, the apparent power rating of an inverter (VA) was equal in value to the active power rating (W). So these terms were often used interchangeably. In the world of reactive power control, however, this is no longer the case, so the relationship between inverter capacity and active power needs to be clearly understood. Fortunately, it is a relatively simple relationship as shown in the following formula:
Inverter capacity x Power Factor = Active Power
Traditionally, PV Inverters were intentionally designed to feed as much active power (kW) as was available at unity power factor into the point of common coupling (PCC). More recently, utilities and independent power providers have shown tremendous interest in the three-phase inverter’s capability to also absorb and provide reactive power Q (kVAR) from and to the grid.
Over 95% of the time a PV inverter is running below its rated output current when converting DC solar power to AC active power. The unused capacity of the inverter can then be put to use to produce reactive power. The output of a smart PV inverter has both reactive and active AC currents that add geometrically to the apparent power, which will be limited by the current rating of the inverter.
There are many modern companies working on the production of such technology, such as GZ Industrial Supplies.
I hope it will be helpful...
With my best regards...
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Grid Inertia is an impending problem if the traditional power systems are decommissioned and replaced with inverter based generation according to some literature. Please, can't this problems be solved by appropriate control active and reactive power ?
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Sudden change in active power demand(change in torque angle) which is reduced due to backup provided by batteries storage of solar farms and domestic solar plans would reduced the amplitude of oscillations or the needed reactive power for stability or the inertia….
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can i use firing pulse generator for the battery inverter
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Yes, but it depends on the current supply capability of the pulse generator. For example, if a power electronics switch needs more power than a pulse generator supply to conduct. It will not work.
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I am simulating a power converter circuit on Simulink platform. This also include a 400 V AC grid. I am not sure about a generic thumb rule to define the impedance of the cables for this 3ph 400V Grid system. Any suggestions?
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As an alternative, you can measure the grid impedance for the 400 V AC system directly. Please check our below publications for in-circuit impedance measurement:
[1] Z. Zhao, "Measurement setup consideration and implementation for inductively coupled online impedance extraction," Ph.D. thesis, Nanyang Technological University, advised by Prof. Kye Yak See, Mar. 2021.
[2] Z. Zhao, K. Y. See, E. K. Chua, A. S. Narayanan, W. Chen, and A. Weerasinghe, "Time-variant in-circuit impedance monitoring based on the inductive coupling method," IEEE Transactions on Instrumentation and Measurement., vol. 68, no. 1, pp. 169-176, Jan. 2019.
[3] Z. Zhao, K. Y. See, W. Wang, E. K. Chua, A. Weerasinghe, Z. Yang, and W. Chen, "Voltage-dependent capacitance extraction of SiC power MOSFETs using inductively coupled in-circuit impedance measurement technique," IEEE Transactions on Instrumentation and Measurement, vol. 61, no. 4, pp. 1322-1328, Aug. 2019.
[4] Z. Zhao, A. Weerasinghe, Q. Sun, F. Fan, K. Y. See, "Improved calibration technique for two-probe setup to enhance its in-circuit impedance measurement accuracy," Measurement, 2021, vol. 185, Art no. 110007.
[5] A. Weerasinghe, Z. Zhao, N. Narampanawe, Z. Yang, T. Svimonishvili, K. Y. See, "Single-probe inductively coupled in-circuit impedance measurement," IEEE Transactions on Electromagnetic Compatibility, 2021, doi: 10.1109/TEMC.2021.3091761.
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Inverter generation is increasing significantly. The traditional protection schemes in distribution circuits are not well suited to locating faults where there is no overcurrent. What approaches have been tried and what are their success rates.
In a MicroGrid, a fault does not increase the inverter output but the output voltage is reduced and this is the only indication of a fault but the entire network sees essentially the same voltage. The fuses and other overcurrent devices likely are challenged to be able to isolate the faults so it seems that a trial and error approach of circuit isolation and restoration is the best method at this time.
Comments on approaches that have been tried with their effectiveness is most appreciated.
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Ehtisham, Thanks for these papers. More specifically, I am looking for techniques where the fault current does not rise because of the output current limitation of the inverters. Overcurrent based techniques are well established but undervoltage while maintaining prefault current levels in not a normal protection relay function in Distribution circuits of 38kV and below. It would be most appreciated if such techniquies are available.
Regards, Joe
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single phase h bridge inverter
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Pls. find the LCL filter equation herewith
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I am designing a control system for Hybrid renewable energy systems using Matlab/simulink/simscape, but currently having a problem. Whenever I run the simulation, I get the error shown below.
"The following block is not supported in Phasor simulation method: Block : FLC_HRES_Controller/Inverter (Three-Phase)/Detailed/Detailed Type : Universal Bridge "
What is the way around this?
Who will help?
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Dear Taofeek,
The concept of phasor mode is that the frequency is constant. In this case, the inverter will work as if it were a transformer. However, as your goal is to create a control algorithm, I think it is better to use the continuous/discrete mode.
Best Regards.
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I) How do I measure common mode voltage in matlab simulation?
II) After knowing the value of the common mode voltage, how do I see the behavior of this voltage together with the stray capacitance generating the leakage current?
III) For example, with this circuit (a), where would I have to measure to get these graphs of common mode voltage and leakage current (b)?
Figures: M. N. H. Khan, M. Forouzesh, Y. P. Siwakoti, L. Li, T. Kerekes and F. Blaabjerg, "Transformerless Inverter Topologies for Single-Phase Photovoltaic Systems: A Comparative Review," in IEEE Journal of Emerging and Selected Topics in Power Electronics, vol. 8, no. 1, pp. 805-835, March 2020, doi: 10.1109/JESTPE.2019.2908672.
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In simulation take the average of the pole voltages.
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Aoa. I hope you all are fine. I want to know which topolgy/technique of ZSI is more efficient and how we calculate power flow in qZS inverter?
Which PWM technique is better for qZSI and why?
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Dear Taimoor Hassan :
Plz have a look at these links.
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LCL filter are used for grid connected three phase inverters. The design of LCL filter is tricky as it can effect the stability of the system. During the design of LCL filter, to calculate converter side inductor, first maximum current ripple is calculated as
∆i_max=V_dc/(6L_i f_sw )
In above equation both ∆i_max and Li are unkown, so some authors[1] suggest to use 10% of Imax for this ripple current. On the other hand, other paper for example [2] and [3] use a relatively complex method to calculate the value of ∆i_max.
My first question is how accurate is use of 10%*Imax approximation? Are there any other quick way or approximations according to standards to find ∆i_max.
My second question is how to find the right attenuation factor δ for particular value of THD?
[1]M. Dursun and M. K. DÖŞOĞLU, "LCL Filter Design for Grid Connected Three-Phase Inverter," 2018 2nd International Symposium on Multidisciplinary Studies and Innovative Technologies (ISMSIT), 2018, pp. 1-4, doi: 10.1109/ISMSIT.2018.8567054.
[2]Said-Romdhane, M.B.; Naouar, M.W.; Belkhodja, I.S.; Monmasson, E. An Improved LCL Filter Design in Order to Ensure Stability without Damping and Despite Large Grid Impedance Variations. Energies 2017, 10, 336. https://doi.org/10.3390/en1003033
M. Ben Saïd-Romdhane, M.W. Naouar, I. Slama. Belkhodja, E. Monmasson,
[3]Simple and systematic LCL filter design for three-phase grid-connected power converters,
Mathematics and Computers in Simulation, Volume 130,2016,Pages 181-193,ISSN 0378-4754,
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Indeed you could benefit from this valuable article about your topic:
"Design Space Optimization of a Three-Phase LCL Filter for Electric Vehicle Ultra-Fast Battery Charging" .. September 2020.
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I'm working on an induction motor drive with a scalar controller. As inverter modulation, I utilized both SVM and SPWM. I discovered that if the frequency and output fundamental voltage from SVM and SPWM are the same, the THD is about the same. The result can be seen in the image attached herewith. Can anybody explain why the THD is the same? Is THD only determined by the amount of fundamental voltage generated? Any literary references would be much appreciated.
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Yes, I have already worked on improving the power quality of three-phase inverters by comparing 3 methods (SPWM, SVPWM and SHE PWM).
the best method was the SHE PWM which eliminates harmonics and gives a very low THD
Concerning your question, in another work, I made a comparative study between the vector and sinusoidal PWM, I found almost the same value of distortion (THD) for different switching frequency, but in the SVPWM, the switching losses decreases which increases the value of the fondalmental (I made a simulation under MATLAB and I validated the results experimentally by the FPGA tool (RT-Lab).
Kind regards
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I am working on a Three-phase Two-stage Grid-connected PV Solar based on boost converter& Inverter with P&O Algorithm, but the pv array is producing a negative current,
I can't tell why, My first reaction was to go over the schematic and each component multiple times, I pretty much checked every component, I tested it before and it worked just fine.
here's my simulink model:
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Does anyone have the PSO-based MATLAB code for calculating the PDP of the inverter and Full Adder circuit?
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Kindly check on this link: https://www.mathworks.com/matlabcentral/fileexchange/52857-particle-swarm-optimization-pso
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Hello everyone.
I am working on fault diagnosis on inverter and I don't know how to pass from signature matrix to proper fault classification. Should I use mathematical modeling of the system?
Thank you.
Lucresse Francelle Towa
phD student
University of Yaounde I
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Thank you Qamar and Muhammad for these papers. Most of them solve fault diagnosis in three phase inverters.
But I am working on a single phase inverter and need to understand more clearly about fault diagnosis in this case.
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If we design Single phase inverter or Three phase inverter with Induction motor as Load,
What do you think about DC Link ?
Shall DC Link be a storage Capacitor or simply Harmonic Elimination Capacitor ?
How Capacitor Should be selected ? Based on voltage or Capacitance and type of capacitor ?
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In a VSI, the DC link capacitor has two main responsibilities –
· Provide low impedance path for high frequency currents (ripple current)
· Stiffen the DC bus (ripple voltage)
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I am using PSCAD, kindly help me ASAP to find solution
There are 2 big issues, while doing our research
1. During implementation of our circuit, we are facing problem regarding the connection of Capacitor module into inverter side. How can we overcome this?
2. During implementation, we have to integrate the control section of Capacitor module as well. But, we don't much about the modules used in control. How can we overcome it?
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Dear Saad,
I have been involved in design of such an LCC thyristor inverter control system ca 25 years ago. This should use phase control. If you could share the circuit diagram, it might be possible to say why the capacitors are needed and how to control them.
Best regards,
Jüri
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I am looking for new interesting fields to do research on power electronics.
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Control and optimization of soft-commutated converters
Diagnostics of power electronic converters
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To obtain dq components of the inverter voltage for unity power factor correction of a 3 phase induction motor
What is the modulation index (ma ) which is mentioned in the 2.2 equation?
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Modulation index ma is the ratio of DC-link voltage and output voltage amplitude.
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In both Grid connected and stand alone Solar PV system an inverter is used.  Please clarify if we can use a same inverter for both grid connected and stand alone operation of solar PV systems?
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Yes, this is posible. But, I recommend to use a real time PV voltage checker and disconnect the inverter from the grid, if the PV couldn’t generate enough voltage. This is to avoid the inverter acts as a load for the grid power system when its output voltage is equal/less than the the grid voltage. Also, you meed zero crossing detector for safe connecting and disconnecting the inverter to the grid.
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Iam not getting how to give dead time in single phase inverter operation via TL494 IC. I tried giving some voltage on DTC pin(4) but not getting dead time between complementary signals. So, please if anyone used TL494 for the same purpose, please help me.
Here iam attaching connection diagram of TL494 and complementary outputs(pin 8, 10).
switching freq= 200kHz
output has taken from pin 8,10 in single ended mode(parallel mode)
DTC pin is initially grounded to get 3% dead time (150 ns). Later i tried giving some voltage on the DTC pin. Still, the dead time is not coming.
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By inspecting your waveform I could see that they are not equal in width. The lower one has smaller pulse width than the upper one. There is delay between the fall edge of the top pulse and the rise edge of the bottom one. The dead time is normally a very small time compared with the cycle time. It is just to avoid that the two transistors becomes on at the same time. So it satisfies the condition break before make. If you want to be sure from the break before make just measure the collector current. It must not contain glitches.
Best wishes
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I am a mechanical student with no background in BLDC motor modelling. Can anyone help me with this? I need it to find the heat generated in the inverter. I have created the vehicle model for the simulation which uses NEDC drive cycle. I got angular velocity and load torque from that. I don't know how to proceed further when it comes to BLDC motor.
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I've calculated the power losses of the MOSFET for each pulse. But i need it for the entire driving cycle. So need the motor model.