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Power System Stability - Science topic

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Do you think that the following online course covers all types of power system stability studies?
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Thank you for answer, but there are several stability issues associated with converter based technologies even if they are embeded in micrigrids or distribution level. These are referred to converter-driven stability as you know.
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Most damping issues seem to arise from positive real parts, so I wanted to check:
1- Do these minimal positive real parts indicate any concerns?
2- Are they essentially negligible in terms of impact on system stability?
I appreciate any guidance you can provide to improve my understanding of their significance in the analysis.
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If it only arises from numerical errors, ignore it. If you have the impression that it may due to the behavior of the system, it indicates a tendency to instability.
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Mostly FACTS devices are used to inject the reactive power into weak power system and improve the stability. Nowadays, we include more number of DG in power system. In this condition, does any instability condition occur? What type of instability occurs? Will using facts devices become possible or not?
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Hello! The answer (positive and negative) to your question depends on some factors and conditions, namely, the power of the system, the importance (category) of consumers fed by this system, the availability of other sources of reactive power, and so on.
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hello all,
I want to design a Static Synchronous Compensator ( statcom ) in order to investigate its impact on power system stability but I found some difficulties in calculating some values like (the rating of statcom, DC-link capacitance, L, the voltage of tow winding of the transformer .... ext )
Any reference? Please,
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Thank you very much Samundra Gurung Samundra Gurung
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It is well-understood that depends on the power system strength or system inertia in addition to the speed protection system settings.
I just would like to see some typical values for such imbalance either normalized or in MW.
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Dear Omar,
As it is rightly answered by the eminent experts of the field. I just want to add some frequency security parameters followed by interconnections.
The conventional frequency response requirement range prescribed by the ENTSO-E for dead band, droop and response delivery time is 0-500 mHz, 2-12% and 2 s-30 s, respectively. The standard technical requirements for new fast frequency reserve services by the ENTSO-E comply with the reserve activation instant at zero seconds immediately after an imbalance. The maximum time required for a complete response activation is 0.70 s for a 0.5 Hz frequency deviation from the nominal value, 1 s for a 0.4 Hz frequency deviation, and 1.30 s for 0.3 Hz frequency deviation. The minimum response for the short duration of support is 5 s and 30 s for the long duration of support.
North American Electric Reliability Corporation (NERC) and Federal Energy Regulatory Commission NERC BAL-003-1, FERC Order 842 specifies the criterion for dead band 36 mHz, for droop 5%, and the delivery should be without any delay and sustain for at least 30 s.
Newly admitted fast-responding frequency response services in the global power grids such as Synchronous Inertial Response (SIR), Fast Frequency Response (FFR), Enhanced Frequency Response (EFR) and Dynamic Regulation Signal (RegD). The SIR service is provided instantly as compared to the FFR, EFR and RegD services, which are provided within 0-2 s. The deadband for the SIR, FFR, and EFR services is 17-36$ mHz, 15- 200 mHz, 15- 50 mHz, respectively. The droop for SIR service is 3-5 % and EFR service is provided through two envelopes.
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Many countries have plans to deploy electric vehicle charging stations (EVCS ). As researchers, how do we start with that?, What about the expected issues that will occur in the power system and ways to solve them?.
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EVs charge their batteries from the power grid and may cause severe effects if not managed properly. On the other hand, they can provide many benefits to the power grid and get revenues for EV owners if managed properly. A good overview of potential negative impacts of EVs charging on electric power systems mainly due to uncontrolled charging and how through controlled charging and discharging those impacts can be reduced and become even positive impacts is provided in the following paper.
Nour, M.; Chaves-Ávila, J.P.; Magdy, G.; Sánchez-Miralles, Á. Review of Positive and Negative Impacts of Electric Vehicles Charging on Electric Power Systems. Energies 2020, 13, 4675. https://doi.org/10.3390/en13184675
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I need to simulate it using MATLAB
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There are lots of models available in Math Works. You can check the model build by Srikanth dakoju to understand the fundamental of series compensators. The link is below:
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I need research papers on the title power system stability enhancement using SSSC with full documentation and simulation. I am beginner
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Do you think a virtual synchronous generator (VSG) can be used in a large power system?
Please explain your ideas.
Thank you for your participation.
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Have a look at this article:
An advanced virtual synchronous generator control technique for frequency regulation of grid-connected PV system, International Journal of Electrical Power & Energy Systems Volume 125, February 2021, 106440.
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What are the various techniques to predict missing data in power systems?
Mostly referring to the measurement data coming in from sensors or smart meters.
References are welcome.
Thanks in advance!
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PMU data can go missing due to several factors - faulty PMU or PDC or communication channel, cyber attack, etc.
Bad data can be also caused due to some of the above reasons or maybe due to some valid reasons such as faults occurring in the power system.
But be the reason valid or invalid, the signal processing algorithm will consider the data to be missing irrespective of the cause and could treat it as a fault and can opt for control strategies accordingly.
My question is directed at gaining insights about how to identify whether the missing/bad data occurred due to a valid (fault, etc) or invalid reason (cyberattack, device failure, etc) by monitoring any other data from any other device or using any algorithm.
If you can share any references, it will also be quite useful.
Thanks a lot in advance.
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It may be by suitably extrapolating from exact neighboring element data (bus or line depending upon the system) at that very point of time. It is some sort of estimation to be applied.
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Why power system stability studies are initialized using load flow rather than optimal power flow?
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First of all, we need to understand the difference between them to answer your question.
In case of the Optimal power flow (OPF), let us take 3 generators connected to a bus to supply to a certain load source, they are all identical in specifications, generation abilities, and the fuel. But they are in different distances from the main load source. So, here the transmission cost (economic) cost will be different, so in that case optimal power flow dictate us to chose the generator closer to the load supply in distance to account for economic cost (transmission cost). So, optimal power flow accounts for decision making of power flow in terms of economics, security context, etc.
On the other hand, normal load flow, compute precise steady state voltages and phase angles and compute real and reactive power flowing in every line & transformer which helps us in determining and conducting the stability studies in power systems. Hope this answers your question.
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Does anyone have experience or ideas about the hardware design of power system stabilizers in a power system?
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I can think of 2 types of PSS implementations, namely, standalone and integrated.
For the stand-alone PSS, there will be a dedicated industrial processor, which most likely will have enough computing capacity for any practical PSS strategy.
A PSS integrated into an excitation system is a bit more complicated case, since one must make sure that the processor is really able to take an extra computational load for PSS calculations.
At ABB we use the PEC80 or AC800PEC for the PSS. Both perform very well.
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For more details about the converter interfaced generation and their impacts on power system stability, you may read
What are the available and recommended software tools for simulating these newly added dynamics?
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PSCAD/EMTDC would be suitable.
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Generator can be modelled using the Classical Swing Equation model as well as higher order models. What are the advantages (and disadvantages) when the order of the model is increased?
Is there any norm of which model we can choose for any certain application or studies?
Citing references can help.
Thanks!
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The selection of an appropriate modeling details is based on the target. If you would like to capture more details electromechanical/electromagnatic dynamics, then more details are preferable. It is a matter of compromise between simplicity and accuracy. In many transient stability studies, only the 2nd order dynamic model of the machine is used for simulating the electromechanical dynamics. If the field circuit dynamics are of interest, then the 3rd order dynamics is used.
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My Greetings,
I have done research on Power System frequency control and stability specifically on microgrids. My inquiry is about Texas A&M University. If anyone know which faculty member works in the mentioned area. here is the link of the faculty members at Texas A&M University.
Introducing other US universities faculties will also be a plus and informative.
Your answer would be truly appreciated.
Mohsen
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Solar power plants have almost solved the stability problems due to excessive battery reserves .....
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I want to simulate nonlinear state space equations, I need it for stability analysis.
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See these articles:
1-Nonlinear dynamic analysis of a single-machine infinite-bus power system
Article Nonlinear dynamic analysis of a single-machine infinite-bus ... 2- PSDAT: Power System Dynamic Analysis Toolbox
Code PSDAT: Power System Dynamic Analysis Toolbox
Best regards
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In addition to Simpower.
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See these articles:
1-Nonlinear dynamic analysis of a single-machine infinite-bus power system
2- PSDAT: Power System Dynamic Analysis Toolbox
Best regards
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So I have MVAsc rating given of an 132 KV grid which is connected to bus. The cable impedances are also given. The total load consumed is also given. How can I model 132 KV grid in PSSE? Can I do it with an equivalent generator? If yes how to estimate its capacity
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I am an expert using PSS/E but I did not understand your question well.
If you mean how to make an equivalent for a 132kV grid, this done by using an equivalent load and generator as well!
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Mostly, PLL is mostly employed to generate the phase angle of PCC voltage in grid-following controlled converter. However, the phase angle can also be directly computed from abc voltage (first do the clark transformation to alpha-beta than calculate the anti-trigonometric). The fluctuations of the result caused by harmonics can be filtered someway, i suppose. Isn't it an easier and more reliable way than PLL?
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Hi Zhaoshun Deng,
The method of Clarke transformation can be used for grid synchronization assuming sinusoidal grid voltages. As you mentioned, low pass filters can be used for taking out the harmonics. The method can give the correct phase information in steady-state operation. However, this method as you can see is an open-loop technique with no feedback signal about the accuracy of the calculated angles.
For a converter operating in the grid following mode, it is very essential that the phase angle of the grid is precisely tracked at all times in spite of any harmonics and in the presence of transient disturbances. The Clarke transformation method suffers from a poor transient response during grid disturbances, mainly due to the use of low pass filters in the forward path without negative feedback.
The PLL essentially does a similar job, but it uses a closed loop technique. The loop filter in the forward path of the PLL performs the job of eliminating the effect of unwanted harmonics. At the same time, the feedback from the output VCO in the PLL makes sure that dynamic response is not compromised.
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I am doing my Master Thesis about the Effect of STATCOM on the power system Stability using PowerFactory Software, Could you help me in the Software? as i want to simulate the Effect of the STATCOM in both Steady state and Dynamics cases.
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I advise you to work on PSIM software. Very useful tool.
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Hello. I am working on the voltage stability issues of an actual large-scale wind power connected power system and am trying to simulate the occurences of three-phase short circuit faults at different parts of my extensively modelled grid mainly in places of high wind penetration. The problem is that whenever I am simulating 3-ph faults at some busbar that should bring down the voltage to almost 0.15-0.25 p.u. at it, the system is becoming unstable right at after the voltage drop or at the instant of the clearance of the fault with the RMS simulations throwing up errors like 'System Matrix Inversion Failed' or 'Equation System could not be solved. Check control conditions.' This problem is disappearing at relatively less voltage dips at the concerned buses (at around 0.3-0.4 pu and above). So I wanted to know if this is an issue with how the grid has been modelled in actual such that at severe voltage dips it becomes unstable, or is it because of an underlying issue in my modelling of the grid which I may have overlooked in the process. I have followed quite efficient dynamic modelling procedures of the wind turbines as per IEC standards and the conventional generators as per the usual standards. Any help regarding this would be much appreciated.
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Soudipan Maity : Were you able to troubleshoot the problem ? As, I am also facing the similar problem in PowerfFctory. Kindly let me know.
Regards,
Deepak
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Can anyone help me to learn about designing WAMS based POD control for SVC or TCSC or VSC based HVDC?
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I think I have a useful book for your requirements. Send me your contact information.
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I want to study the stability of a single machine infinite bus system with MATLAB. My problem is not in simpower systems, but in simulink.
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https://SimPowerSystems User's Guide
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why power system stability studies are initialized using load flow rather than optimal power flow?
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Omar Mohamed Thanks for enlightening the concepts so lucidly.
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I am working on Power system modles in MATLAB with some adaptive controllers. The simulation run for different time duration like 8,10, and 15 sec. Now i need to get the computational time taken by the computer to solve the iteration behind theses simulations. I found tic and toc command but need more detailed explanation to use it. Thanks
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% For Simulink model
tic, sim('Simmulink_model_Name'), toc
% It is strongly recommended that you run the model at least min once before
% this test because it compiled before start.
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For example, if I want to find the stochastic OPF of a system, shift factors can provide a way to find shifted power for different scenarios. Therefore, OPF for each scenario is not required but only for base case. This will reduce simulation time. Please share relevant code if possible. Thanks.
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Thanks for your kind response.
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The question arises mainly because traditionally the rotor-angle stability is defined for power systems with large rotating machines. But in LV system with large distributed generation, what we have is inverter coupled PV units, storage (also say inverter coupled), EVs etc.
So I want to understand how rotor-angle stability (and transient stability which is also coming from rotor-angle stability) is defined in such a situation. Can someone shed some light on this topic?
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Rotor angle stability literally refers to the stability of conventional synchronous generators no matter it is large-disturbance/transient stability due to lack of synchronizing torque or small-disturbance stability due to lack of damping. If there is no SG in the system, technically there should not be any rotor angle stability problem or it should not be called rotor angle stability. But in this case, does the synchronism/damping problem still exist? The answer is Yes. You must have seen a lot of papers talking about PLL stability right? (if you would like to name it rotor angle stability, you can define youself!) The 'new' synchronism/damping problem for power electronic converter-interfaced equipment mostly manifest in the form of undamped oscillations due to poor tuning of controller parameters in the lower voltage systems. When a grid has both SG and new power electronic converter-connected generation, the dynamics might be much more complex considering their interactions across a range of frequency.
Recently, there is a paper entitled 'Microgrid Stability Defintions, Analysis and Examples' provided by IEEE PES Task Force on Microgrid Stability, which might help you understand this issue better.
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Why is a DC link capacitor required in a grid integrated renewable energy system?
Suppose we consider a single stage system with solar PV array  feeding the grid than why do we require a DC link capacitor? A MPPT technique will ensure that maximum power and required reference voltage is made available at inverter terminals.Why is an energy saving device required at the inverter input  terminals? Is it working as a filter? Is it that the PV array will transfer its entire energy to DC link capacitor which will further transfer it to the grid? If yes, why can't it be done without capacitor?
In steady state do we need to use DC link capacitor or is it just required for dynamic conditions?
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Maulik,
welcome,
The function of the capacitor is energy storage as potential energy. So, it can supply the the load when the source is reduced and it will store the surplus power when in case of Generator excess. So it serves as regulator and stabilizer between the source and the load. As it increases, it will store more energy and can fix the voltage for longer time.
Best wishes
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Hi everyone,
I am doing research on small signal stability/ dynamic stability in a microgrid. As you know, it's the droop parameters of power controller which are mainly responsible for the dynamic stability of a microgrid. I am thus, considering research on optimization of these parameters. I have however few questions regarding it.
1) The load modeling plays a vital role in small signal stability of a large grid. However, I have seen most microgrid loads are represented as only impedance (R-L load). Can I expect a much different behavior if I model the load also as constant power or constant current type?
2) The dc side voltage is considered constant in most microgrid analysis. If I model the PV or some source, the dc reference changes. Do you think this may effect the dynamic stability?
3) Thirdly, are there any specific suggestions in dynamic stability domain of a microgrid which I can use in my research?
Thank you in advance
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1-Constant loads decrease microgrid damping and so decrease the system stability.
2- DC side dynamics are very slow in comparison to the AC side dynamics. So it can be neglected for stability studies.
3- The droop coefficients are very important stability factors if you use grid-support grid forming strategy for most of ec-ders.
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As we know, coherent groups of synchronous generators can be identified and converted to an equivalent dynamic model to simplify a given power system and still maintain the dynamics of the system. However, the Type-3 and Type-4 wind farms do not possess much inertia and hence cannot replicate the behaviour of synchronous generators. What approaches can still be made to aggregate the wind farms present in a region and connect it to a single transmission bus, such that the dynamics of the system is still maintained? Any help on this would be much appreciated.
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Modern generators - using any source, wind, solar, fossil - are all themselves increasingly complex and use algorithms and computers to 'optimise' their performance. So I don't think you can aggregate them and 'simplify' the result - if you try to do this your results will be deceptive, and will not closely (or at all) match the behaviour of such systems in the real world. Seek instead to define the transfer functions of each farm and come up with specifications of their control algorithms that ensure that this transfer function is maintained across all likely operating conditions. Best of luck!
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Hi,
I am trying to model a system in PSS/e for transient stability studies. The network I am trying to model has a total demand of 1300 MW during peak season and it is interconnected to two other countries which have total capacity of 10 GW and 2 GW. I've short circuit MVA for the two interconnections, using which I've calculated the Zsource of the machines.
I've two questions:
1. Would I be using the short circuit MVA to represent the machine base or total capacity of the each machine for the studies?
2. Which generator and governor model to use to represent the inter-connection? Also, what would be the inertia (H) of the machine for transient stability studies?
Thanks for the help.
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Nitish
1. It's an infinite bus, so frequency changes don't come into it. Hence I don't think you need to model the infinite bus source with governor droop (sorry Arun).
2. I'm with M. Lima: a GENCLS synch machine model with H=0 is the best & simplest representation to an InfBus source.
3. A useful equivalent system model for the scenario you describe connects the InfBus source to the test network via 2 (or more) circuits with impedance chosen to reflect the pre- and post-fault infeed MVA. Then a fault on one, cleared by tripping it, simulates the change in post-fault conditions.
4. It doesn't matter what base MVA you choose (except to change the numeric values). Pu on test network base is OK, just so long as you make the connecting circuit X pu on the same base
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which one is the most worst harmonics for power system from the following harmonics
(3rd, 5th, 7th and 9th)
and why?
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In three-phase three-wire systems, the effect of the third-harmonic current is not serious, because most of the current is zero-sequence current. However, if many single-phase rectifier loads are unevenly installed in three-phase grids, the third-harmonic currents may become serious. Specially, in three-phase four-wire systems the third harmonic currents add up in the neutral wire creating overheating of the conductors. As already pointed out, as the harmonic frequency increases, the amplitude decreases so their effects are less harmful. Here is a nice paper on this subject.
Third-Harmonic Current Suppression for Power Distribution Systems Under Unbalanced Installation of DG Units
Hidehito Yoshida; Keiji Wada
IEEE Transactions on Industrial Electronics
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Im trying to model a SVC in Etap to replace normal capacitor bank. But when I run load flow simulation, no MVAR is injected from the SVC, as how a normal capbank would do. Can anyone advise me on this?
Thank you in advance
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I managed to find the solution for my case and it is related to the voltage at SVC bus.
I revised the Vref value in my SVC setting and it works. I believe that the SVC VAR injection depends on the differences between SVC bus voltage and the Vref setting.
Thank you for your advice.
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what is the technique by means of which we can inject harmonics in a system?
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May I ask you why do you want to inject harmonics to a system?
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Hello everyone,
I am working on analysis of PV Solar penetration on power system stability. I want to know about what probability distribution function does the Solar forecast error follow? The time interval of interest for me is 1 hour.
Cheers
Sam
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It is a great question. You want to know the energy intensity, since it is changing during the day by the exposure. First I suggest to understand the main processes:
- sunrise, increasing energy level, sundown. When the electricity production starts and finishes.
- demand curve,
- price curve,
- export/import during the day,
- base production and base load.
In that way you will know better what the hourly forecast error means in energy and money term (the significance is different hour by hour. For instance, there is zero error at night, it is constant).
After that, you can use the probability distribution of the daily forecasts since your short term energy intensity forecast error distribution won't differ, even you consider the hourly energy intensity forecast since they are the same natural phenomena.
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Dear all,
Generally, when we talk about the large scale of PV penetration in power grid, we associate the term stability. But, in case of  roof top PV system to be connected extensively in the LOW VOLTAGE radial feeder, what are the factors to be focused on? Voltage Parameter violation, energy loss tracking, etc being the ones i pointed out. Others? We don't have to watch out for transient stability issues, do we?
Thanks in Advance.
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PV solar generator connection should be analyzed for all typical parameters which are common in DG analysis, such as voltage variations, power loss, short circuit, bidirectional flow, protection, power quality, intermittence etc. When it comes to transient stability analysis, which has traditionally been reserved for transmission systems, PV solar generators in LV network are usually not scrutinized in this sense. The broader picture is mainly concerned with the increase in the popularity of microgrids and the capability of an LV network to operate in both standalone and grid connected mode. In this sense, transient stability and small signal analysis are becoming important and are required in order to ensure safe and effective operation of the microgrid. This is mainly because of an interaction of control systems of DGs, switching operations required for transition from standalone to grid connected mode (and vice versa) and low inertia inherent to small DG
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Hi
i know this question is basic but it confusing me
can someone explain to me the example 12.9 from the book of power system stability and control of prof KUNDUR.
1-I did not understand how he found the critical modes of interarea oscillation, after he calculated the frequency there is more then mode how he chose the critical one ?
2-when we have some modes (eigenvalue) has frequencies in the range of 0.7 to 2 HZ ,it means local interaction how we can eliminate this local interaction (i found in the book of prof Kundur talking about using the right eigenvector) how we can use it
to delete this local oscillation
i really need your help
thank you
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Dear Taib,
In study of small signal stability problem, it is more relevant to investigate first swing modes of the power system and then identify critical swing mode among all the swing modes. In order to improve small signal stability, damping ratio of those critical swing modes to be improved applying power system stabilizer or FACTS devices.
You can follow this reference for the above:
Power System Small Signal Stability Analysis and Control
Author(s): Debasish Mondal, Abhijit Chakrabarti and Aparajita Sengupta
 
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I have a problem in my simulation in MATLAB. There is a error in compensation block. Can anybody to help me?
I've attached my simulation (simulink file) and Circuit topology (Word file) In the following. Please check it.
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I will try to solve your problem
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Why do some use alpha-beta transformation while others use dq0 transformation? Can anyone explain (if its because of my lack of understanding of both transformation applications)?
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There are 3 reasons that we may prefer d-q transform on alpha-beta :
First is what Hansheng che said. Tracking non-DC quantities with PID controllers is erroneous. However, cross coupling between variables degrades control actions in dq framework.
Second, from the view point of communications, transmission of DC parameters needs lower bandwidth in comparison with ac quantities. So in secondary or tertiary level of hierarchical and centralized control platforms, we prefer to use dq framework.
Third , when we are going to control more than one generator or DG by a single controller, it is better to use a common frame work , which can be settle down easier  within dq framework by choosing nominal frequency of grid as synchronous frame for all of them.
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I am working to implement an Extended Kalman Filter to estimate the dynamic state of a synchronous generator connected to a Power System. I am using Power World Software to generate simulation data to use it as input to the estimator, and I am adding gaussian white noise to the data as "measurement noise".
Can someone tell me how can I add "process noise" to this simulation data?
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Hello. You don't usually add process noise to the simulated data. The assumption is that the dynamical process obeys some physical laws that can be described by a system of ordinary differential equations. The process noise is introduced in the filter to obtain a least-squares type problem for which the Kalman filter is the optimal estimator (under certain conditions). The process noise covariance Q is usually adjusted as a tuning parameter to trade of the state estimation performance. The rule of thumb is: higher Q, better tracking of the data (and the noise); lower Q - better rejection of the noise (and ignoring the data) - hence smoother estimates.
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I have two Power Quality meters (UniPower UP-2210 and CT Labs Vector II) on a 8.5 MVA 66kV 50 Hz network, connected at the same points on the same Instrument Transformers BUT don't give out the same measurements (Powers and Power Factor).
These instruments were installed by their manufacturers and are all well calibrated.
 What should I probably look to solve the issue??
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Hello Theophilus,
First identify what is the real problem. As you have already stated and I also believe that the instruments must be working fine.
So, first try to connect one instrument at a time and then take the measurement. Then connect the other instrument and confirm the measurements.
I believe something to do with the loading or imappropriate impedance matching, with the instrument transformers as you are connecting two different instruments simultaneously.
Best luck!
-Prasanna Waichal
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I need hardware model
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We want Hardware model not software simulation!
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Hi everyone,
I am trying to create some simple user defined models (UDM) in psat. I am using psat 2.1.9 and tried to create UDM from component browser in PSAT GUI. However, I am unable to define anything like buse or state variable on a new model. I then tried to modify the existing examples and still was unable to do it. 
Can anyone help me with it?
Cheers
Sam
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Hello Sam
You can go through this material, may b it will help to modify the state variables...
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This paper includes area detection, sector selection, voltage vector selection of NPC inverter to limit hysteresis current.
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Please send me the model using LabvIEW or etap.
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For a system
                                                    dp/dt=Ap+f(p,t),                                    (1)
where f(p,t)<=0 for any p in the domain and t. If dp/dt=Ap is asymptotically stable of zero solution, is the system (1) same with dp/dt=Ap near the zero solution?
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With proper manipulation the given equation may be rewritten as
dp/dt = Aaug p .
Then  Lyapunov stability studies may be carried out
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Hi everyone,
I am analyzing the effect of PV penetration in small signal stability. My test system is the two area system from Kundur book shown in file 1. The PV controller is as shown in the file 2. It only has an ac voltage regulating loop which consists of a PI controller. 
I then tested the system. For a fixed PV generation (700MW in this case), when I change the integral gain (Ki), I found out that the inter area damping decreases! The initial gain of Ki is 50 where the corresponding inter area damping was 2% but when I reduce it to around 15, it reduces to around 0.8% as can be seen from file 3.
I am a little bit confused. Does this result mean that he PV integral controller can affect the interarea electro-mechanical mode of oscillation?
Cheers
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Good then that means point 2 that I made in my answer is valid for your case. 
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Hi,
I am looking to design a robust power oscillation damper for a large power system network. As you know, I will have to obtain the information like eigen values etc for which I could use a software . My question is their any software which allows to design my own robust controller and later on implement  with the test system and still obtain the crucial information like eigen values and time domain simulations?
Thank you in advance
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There are many software that can help you but unfortunately all are commercial. You have to spend much money in purchasing them. E.g. DSAT tools, PSSE, DigSILENT, ETAP ..... they have some programming interface by which you can extract eigenvalues and all other and code your algorithms in matlab or python, and interact with the system developed in these software.......
The power system research group from imperial college london is very famous for this type of work. You can google their group and papers to get some idea of how they are doing it.....
best regards,
Jagadeesh
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What are the conditions, we should check, while selecting exciter and/or power system stabilizer for different type of generators (like GENROU) for transient analysis.
Can anyone please tell me which exciter and power system stabilizer is more suitable for generator like GENROU and/or GENSAL.
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Hi everyone,
I plan to modify some renewable energy converter structure (say PV and wind) and study their effect on low frequency oscillations in the grid. Once, I modify, I want to connect it to a grid or a large number of buses. My queries are:
1) I'm aware that most commercial and free software have their own built in models and can give information about eigen values. Is their some way so that I can similar information for my modified model?
2) How does our fellow authors test say a new robust controller that they built in a large IEEE bus system?  
Thank you in advance
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Hi Samundra,
If you are working with PSCAD/EMTDC, then there should be absolutely no problem ! It is a great one for incorporation of user defined models at all levels.
Just make sure that the installation of the package that you have access to must have adequate node capability that the intended user defined model requires - whatever it may be - a power electronic circuit, a machine, a control algo, or anything else ! The maximum number of nodes allowed is the only thing you need to watch for.
With best wishes.
-Sanjay
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The placing of DG units in IEEE RTS - 96 System will improve the reliability?
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You can integrate  DG units in IEEE RTS-96 test System for purpose of improving the reliability of the system. Secondly, you have have study the impacts of DG units on the following  reliability indices, i.e LOLP,LOLE, EENS, EIR, SAIDI, SAIDI,SAIDI,SAIFI,CAIFI, ECOST, etc. 
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Am trying to refine my Finite Element Analysis to take into account of the small gaps that must exist between the magnets and the rotor slots that host them, in order to be phisically able to insert the PMs in the slot.
These small gaps will provide for some marginal reduction of the magneto-motive-force produced by the magnets.
I want to capture this effect without being forced to have a very fine mesh in such gaps, so I'd like to model the PMs as completely filling the slot while properly modifying their properties (coercitivity and permeability) in MagNet, obviously achieving the same result of flux distribution in the machine as achieved with the real, "gapped" structure yet in a more computationally efficient way.
Has anyone developed a method to do this?
Thanks a lot,
Francesco
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Guillaume, Abdoulkadri, Anees,
thank you very much for your feedback.
Maybe I did not explain myself well enough: I actually can model such clearance gap through the Finite Element software and get results with it, the drawback is that such clearance gap is usually very thin thus requiring a fine meshing (in order to avoid excessively distorted elements) and ultimately an increase in solving time.
From a pure computationally efficient point of view, I would like to model the magnet as filling the entire thickness of the "pocket" that will host it, while modifying its properties (remanence and permeability) to be lower than the actual values through some function of the respective lengths of actual PM and actual clearance gap. Something like what I sketched in the picture below, with the gap purposely exaggerated for clarity reasons...
Of course, the modified magnet properties will lead to the same results in terms of flux distribution in the airgap, the rotor and the stator core, needles to say.
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the bode plot response of a power system stabilizer, the phase is always above the 0 degree, how to calculate the gain margin?
Regards
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Dear Zeyad,
Here is an attached file in subject.
Best regards
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Utilities normally charge a penalty to customers who have a power factor below certain limit, which is typically between 0.90 and 0.95. Power factor limits applied in some countries are for instance: Venezuela 0.90; Chile 0.93; Colombia 0.90; Uruguay 0.92; Argentina 0.85; Spain 0.95; Ecuador 0.92; etc. The penalization scheme also varies from one country to other, ore from one utility to other. I would really appreciate your comments on how this limit should be defined, why one country use 0.90 and other 0.93? which aspects must one have into account for defining this limit and the penalization scheme?
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Hello dear friend,
Your question might not have a clear answer, but I guess reading the following pdf may help you to get your answer.
Good luck,
Sajjad
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Hi all,
I am trying to analyze a rural microgrid. The microgrid is powered by Microhydro. This microgrid contains 7 synchronous generators which are interconnected through transmission lines. As far as I know, they have diode based excitation system. The size of the generators is very small (maximum=16kVA). My question is:
1) Can there exist local and inter area mode of oscillation between the generators as in the large grid?
These Microhydro generators uses a fast power electronic based component called as Load controller which is responsible for the frequency regulation.  As the standard software doesn't have this load controller,
2) Can I approximate this load controller with a governor of large gain for the simulation?
Thanks in advance
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that size of synchronous generator seems too small. You can increase your peak load a bit more so that your assumption about the size of synchronous generators seem more reasonable. 
After quick search, I can find the smallest synchronous generators can be from 150 KVA to 5000 KVA. But, don't forget, "synchronous" really means the generator(s) are connected to the grid all the time. If they are not connected to the grid, or in your isolated microgrid case, the word synchronous does not mean anything and you may not have SSR kind of problem. 
I hope that is clear to you.
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Basically, I want to find out the generator coherency employing the slow inter-area modes information available to us.
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this book may be helpful to you
Power System Coherency and Model Reduction by J.H.Chow
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How can we correct the power factor of two switch non-inverting buck-boost converter? because in boost mode it is easily corrected but in buck mode input current is discontinuous ?
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If you want a very continous DC supply current, I would use an LC filter in the DC supply.
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the parameters of PSS application in automatic voltage regulator are adjusted by conventional trial and error method. is there any other accurate scheme to achieve the gains for optimum performance.
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Trial and error? I really hope you are kidding, nobody can make a PSS (or for that matter any closed-loop control) work based on trial and error.
In practice, the PSS is commissioned based on a frequency response test and the PSS phase compensation is adjust to compensate the phase lag of the GEP(s) transfer function. 
The foundations are still the de Mello and Concordia 1969 paper and the E. Larsen 1981 papers (3 parts) published in the IEEE Trans. on PAS.
The PSS needs to be robust, as the actual requirements for the PSS compensation change with system loading and also with system configuration (outages, etc.). If you intend to use optimization, how would you define the objective function?
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I recently came across the seminal work on "Negative-sequence current injection for fast islanding detection of a distributed resource unit". The paper says "The RLC load tank draws the rated, positive-sequence fundamental current component supplied by VSC at unity power factor. If a 60 Hz negative-sequence current component is also injected by the converter current controller, it flows into the grid through the low-impedance path provided by the stiff utility grid".
Why does the grid have a relatively larger positive sequence impedance than the negative sequence impedance? (Since the load draws positive sequence current and not the negative sequence current, even though the positive and negative sequence impedances are the same for the static RLC load)
Thanks,
Mayank
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Grid operates with positive phase sequence (ABC). The generated voltages are of positive sequence only. If grid is balanced there will be no negative sequence  currents ( which are due to negative phase sequence) and zero sequence currents.If there is unbalance, then only negative sequence and zero sequence currents flow. Further zero sequence currents flow only if a path exists for their flow as their phase difference is zero.Under normal operation, positive sequence components play the major role.For small unbalances, magnitude of negative sequence voltage components will be less so does the currents.  
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factors that could cause power system failure,  system failure probability caused by uncertainty in component reliability parameters
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 I think your desired question is to find a methodology to predict failure of a power by system by using probabilistic method of equipment failure rate under reliability evaluation. If what I say is true,  I think this is a good point to discuss about even the philosophy of reliability evaluation cannot be served such purposes.
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Which factor is most severe for power system collapse? Whether it is under frequency or under voltage?
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Frequency plays a vital role in the system stability. all the generators in the system are synchronised at one frequency but voltage has acceptable range. If the frequency deviates from desired generators start to go out of synchronism which triggers events in the power system causing voltage, frequency, power imbalance due to which a power system will collapse. 
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I am highly interested in powers system protection and stability can anyone help me with a researchable topic for masters degree theses.And how tips on how to get started?
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In my opinion some suggestable topics are
1) Mal-operation of 3rd Zone of relay during critical conditions(e.g- load encroachment and  power swings etc.)
2) Different kinds of  fault location algorithms
3) PMU performance during Transient conditions ( including special cases . e.g- communication link failures )
4) Power Quality issues
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could anyone please tell me as to why there is distortion in the supply before a bridge rectifier circuit with no load connected at its terminals?
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In simulation case, there is no any distoration during the no load. However, in hardware the distoration in no load  is originaly from the grid not from the bridge.
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i have worked on design of PSS for SMIB and multimachine system.
At present my task, design hardware of PSS in power plants.
plz provide best suggestion to solve above problem.
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You can follow this book:
Power System Small Signal Stability Analysis and Control 
by Debasish Mondal (Author), Abhijit Chakrabarti (Author), Aparajita Sengupta (Author)
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For example: type of the load, regulation of GOV, AVR, PSS and ..... .
What is important to a long term voltage stability in  a 30 bus IEEE?
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For long term voltage stability you have to worsen the system permanently. This means you should not only simulate a three phase fault with clearing after 150ms because after that the system will either be transiently instable and collapse or it will return to stable point. Hence, you need to additionally outage a line or any reactive power source (capacitor, generator).
Then the most important thing is the load model because you can almost never experience a voltage collapse with a impedance load, because the load adapts to the voltage. What you need is a load, that recovers over time. Therefore you can use automatic tap-changers or other load recovery mechanisms at load side. When load recovers in a highly loaded system, the need for reactive power increases with I². This will automatically bring your system to the 'edge'.
Also you need to make sure, generator exciters are limited.
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From the basic engineering itself this question has posed me lot of trouble. The main reason is that there is lot of explanation available and few contradict each other. For example, one explanation was it is the medium through active power is transferred, if that is the case then what about DC power transfer? 
So here i would like to know your opinion on the concept of reactive power and would like to discuss each and every view so that i can have a clear cut understanding of 'real REACTIVE POWER'. 
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I want to make you understand about reactive power by using simple circuit knowledge. Most of the load you see are inductive. But they are not purely inductive, but a mix of resistive and inductive. Similarly a very few load are capacitive, which is also not a pure capacitive load, but a mixing of capacitive and resistive part. We know power taken by a load is called apparent power. apparent power is composed of active and reactive power. The power consumed by the resistive part of a load is known as active power and it is, active power=VIcos(theta) and unit of this power is watt(W). where V is the voltage across the load, I is the current through the load and theta is the angle between current and voltage. The power consumed by the reactive (capacitive or inductive) part of a load is known as reactive power and it is, reactive power=VIsin(theta) and unit of this power is var (volt amp reactive). the difference between both of the equation is only on sine and cosine. So apparent power=sqrt(active power2+reactive power2)=VI and its unit is volt ampere. For your kind convenience I uploaded two photo. reactive power means lost of power. Hope you understand
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Does anybody know how can I get WSCC system disturbance data on August 10, 1996? I have tried to access this ( ftp.bpa.gov/pub/WAMS%20Information/ ) , but it seems does not work as well.
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read attached files and if any problem then reply
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Rotor angle stability and voltage ratings are somewhat interlinked but rotor angle is purely on the generation side, so what effects can it cause on voltage stability limits?
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The main factor causing instability is the ability of the power system inability of the power system to meet the demand of reactive power.When you talk about the angle stability it is a balance between reactive active power that is mechanical input of the turbine or mechanical  input from the turbine must be equal to electrical output from the generator it is a real power balance there in voltage stability we require the balance between the reactive power that is reactive power generated and the reactive power consumed in a system and  if in case the system is unable to maintain this balance then the problem of voltage instability occurs.
The heart of the problem is usually the voltage drop that occurs when active power and reactive power flow through inductive reactances associated with the transmission network. When you again look what are  the main causes of voltage drop the the voltage drop takes place in transmission system in transformers or any part of the ah system due to the flow of real and reactive power and the system has its impedance resistance and reactance and because of this there is a voltage drop in the system and this drop is the primary cause of voltage instability.
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I understand that when the current reaches zero,the voltage across phase to earth capacitance is maximum which tends to restrike the arc.After that I was unable to follow.I attached the document I read from.Thanks in advance
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Without much analysis, it may behave lake an open conductor, because there is no return, so the voltage in that phase may jump to almost twice nominal.  If it is intermittent, then the phenomena would repeat itself, and a voltage escalation may result.  An EMTP model of the situation will show the details.
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just a short question. As I am working with Power Factory 14.1/ DIgSILENT i have to write a small skript to get my program doing, what i want it to do.
The language used by Power Factory is called DPL. I want to create a new Matrix, in witch i will write the results of a load flow analysis later on. To create such a matrix the manual gives the following example:
M1.Init(x,y);
With x and y defining the rows and collums of that Matrix, and M1 beeing the name of it. If i want to create a Matrix like that, i get the messange, that M1 is not known and thus the program stops.
How can i tell Power Factory, that i would like to create a new matrix?
Thanks for every answer.
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I think you should define your variable in your script or create a matrix manually in your DPL folder.
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Hello,
Dear RG researchers, as I am working on a paper I need a PSCAD-model of the IEEE 39-bus system. I would be really grateful if anybody can help me with this.
Regards,
Akbar Amirian.
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Hi Mr. Akbar
i have request like another! can u tell me how was your solved? i need simulation a standard 39 bus IEEE .
thanks
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For damping of oscillations using PSS4B which parameters are most preferable as it contains 33 parameters if we observe the block diagram of PSS4B.
As PSS2B contains Kst(gain) and Time constants T1,T2,T3 and T4.
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If I understood the question is going about tuning PSS2B via above mentioned parameters.
Yes, those parameters are of main influence regarding the dynamic stability of a machine (system). Also, the parameters Ks2, T10, T11 must be added to the set of tunable parameters. The frequency properties achieved by  PSS4B  stabilizers can't be implemented via PSS2B stabilizer, because PSS4B is three (frequency) band stabilizer. Typical parameter settings for both stabilizer types are available in IEEE Std 421.5 - 2005.
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I want to tune a power system stabilizer for power system stability in single machine and multi-machine power system, i need to an idea that how can I use RL in this process,
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look at Damien Ernst publications too. 
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My research area is handling optimal reactive power dispatch problem with voltage stability in transmission/distribution/microgrid. Is it good? Can you suggest?
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Now I am narrowing my problem.......i.e., investigations of Voltage Stability in distribution system with effect of PV type Distribution Generators...., indirectly I mean how reactive power compensation can be provided in a system with more influence of PV type DG's.......