# Power Systems Modelling

New
How to generate ptrace file from wattch power simulator which is used as input to hotspot?

I want to to generate the power trace input file for HotSpot.

I am using Wattch power simulator. Wattch doesn't generate the power trace for directly.

can any one help me what changes required in wattch source code to generate ptrace file

4
Any advice on an infeasible solution for reduced gradient less than tolerance?

Dear all ;

Am working on MINLP to minimize the total power losses of the network.

All the used equations were typed correctly.But when i run the GAMS code it gives this error : Infeasible solution. Reduced gradient less than tolerance?

I need assistance in that error ?

Best Regards.

Amna

Yes, it is not easy to solve MINLP problem. One has to be very familiar with solution method. If MINLP does not work, consider linearizing the non-linear part and solve it with LP algorithm, where the solution is global optimum. With MINLP, the optimal solution may not be global optimum.

Sorry for replying so late......

• Mohamed Abd Elwahab Ali added an answer:
3
How do I determine a mono-machine equivalent model of real power system?

Hi

I am working on load frequency control,I want to determine a single machine equivalent model of real power system(Governer -Turbine-Generator) by transfert function. PLZ provide best suggestion to solve this problem

if you need a simple linear model "Power System Analysis " by Haddi Sadat will be sufficient. If you need and exact non-linear model you can contact me for further cooperation.

5
Simple Newton-Raphson Matlab 4-bus Voltage equation from power?

Hi,

So since apparent power S = |V|2 / |Z| does that imply that P + Q = V2 / Z for complex voltage and impedances?

The reason I ask is I'm trying to run a simple 4-bus NR analysis of bus voltages, however I'm not getting a converging result and I'm concerned that I'm not using the right function and Jacobian (using the aformentioned power equation above).

Since I have a 4x1 matrix for the compelx bus powers and a 4x4 maxtrix for the complex admittances ('Y_mat'), I was concidering the 4x1 voltage matrix the variable, and using the NR relation y = f(x), I took the power matrix as the constant 'y', 'x' as the 'volts' matrix and the functon was: volts^2*Y_mat

so the prime of the function is 2*volts*Y_mat.

Hence, the itterative NR equation is:

volts = last_guess + (power - volts^2*Y_mat)/ (2*volts*Y_mat)

But I think there is a flaw, I'll attach the code if anyone could please take a look. I've tried all mannor of things such as conjugates, abosolutes and negatives, with no success.

I'm not confident in the prime of the function being correct, or using this power equation.

Thanks!

I have made generalized MATLAB program using N-R method for load flow study.

Tell me clearly what do you want? my e-mail is: mgrabbani@easternuni.edu.bd

• Yasser E Abueldahab added an answer:
4
Can anyone help with problems in sample time simulation of mppt control using Simulink?

I have an issue with the simulation of a PV system. I'm using simulink for the PV panel, the buck converter and the algorithm (inside a matlab function block).

I had to use discrete simulation as i was having problems with continuous mode. I got the best results with control sample time of 10us and power sample time of 0.1us but i've been told this control velocity is really fast and that it requires a powerful processor.

I don't have a lot of knowledge of field implementation so i would like to know if indeed this is too fast or what other options i might have,

I would like to let you know that, there are a differance between the real time simulation and the one of the simulink. Simulink checks a long the system stats and outputs every sample time for the time of simulation specified. for example , regarding your data the simulink checks the outputs and stats every 10 micro sec. for control and 0.1 for the power model. that has no correlation to the real time. However, you need to choose the suitable Ts in order to not diverging the stats of your model or get the simulation takes too long time. as per the implementation you design to track the MPP so that does not need a very high speed.

• Lionel R Orama added an answer:
16
When the single line outage in a power system make the system insecure?

Hi

I am not really familiar with the power systems and I need some help for working with MatPower to generate different operating conditions around10,000 scenarios for the  IEEE118 Bus system by varying the load and generation from 50% to 200% of their  system base case values. I have to make 4 class categories (Secure, Critically secure, Insecure and Highly Insecure) base on static security index. I have some questions about it:

1- Should I change the load of each bus randomly in each case? or should I change all the loads by one random number in each case?

2- When the single outage make the system unsecure?

3- I need to find Sflow  (the MVA power flow in branch connecting ith to jth buses. How can I make it by real and reactive power injected into \from" end of branch and real and reactive power injected into \to" end of branch?

Thanks

May I add some details.  Security, from the standpoint of system protection is that the protection will not operate when there is no fault.  So an unsecure system is that no fault causes the protection to operate.  From the system stability standpoint, the issue is that if a fault actually occurs, then the system remain stable if the power transfer can swings to a point in which it can recover without the operation of the protection system.  A Short Line Fault (even if it is a single fault) for example, may cause system instability because it is difficult for the circuit breaker to handled the high frequency oscillations that the Transient Recovery Voltage (TRV) imposes on the interrupter before the peak of the system TRV.  Not been able to interrupt the fault, the oscillations between generation and load may cause chain reaction of faults.  You may check if the simulation software you are using have the capability to handle travelling waves, because that is what creates the high frequency oscillations in the TRV.

3
How can I design a battery capacity model?

design battery model but want to optimize the results using optimization techniques.

plz suggest how to solve it.

how to model capacity model on simulink.

Dear Mahendra

you can look at the Matlab Simulink model described in this link

http://www.mathworks.com/help/physmod/elec/ref/variablecapacitor.html;jsessionid=31690f2c0ce7a698d55fa53de6ae

Gerro

3
What are the factors which decide the amount of current drawn by a dc-dc converter ?

I am designing a dc- dc high power converter with fixed input voltage and I want to know, what are the factors which decides the amount of current drawn from the source by a dc-dc converter ? , how can I improve the current drawn from the source so that maximum energy could be transferred through the the power converter?

I am looking to modify the topology of basic modular multilevel dc dc converter attached here, my objective is to draw maximum power from fixed input dc supply for this should I connect more number of sub-modules in series or in parallel or any other suggestions? Please help me.

+ 1 more attachment

5
Is there any practical data or literature where the accelerating time from zero to nominal speed for turbo generators can be found?

Generators are rated power from 3-50 MW. In attachment is one test diagram for 5 MW generator

Dear Gabriel. Thank you

That is it. I have found answers on Fig 11 in the first and Fig 12 in the second paper which confirm our measurements for 5 MW steam generator which time was 40 min.

Srete

4
How to make an interface between matlab and pscad?

Hello, everyone I'm working on optimization of coordinating overcurrent relay I wrote allocation codes and optimization code in matlab but I need to recall mfiles in PSCAD. I want o know is that possible to link between matlab and pscad wich I able to use matlab codes in Pscad?

Hi ,

thanks alot

• Ravi Bhushan asked a question:
Open
How can I design h-infinity controller through state-space approach for the DFIG system?

I have already designed the LQR controller for DFIG system.

In LQR case

x_dot=Ax+Bu

y=Cx+Du

Here, I have already A, B, C and D matrices

In H-infinity case

x_dot=Ax+B1*w+B2*u

z=C1*x+D11*w+D12*u

y=C2*x+D21*w+D22*u

How will I decide  the variables z and y?

3
What is the best winding configuration for a PMSG?

I'm designing a 5 kW and 115 rpm permanent magnet synchronous generator for a direct drive tidal turbine. I'm going to use concentrated winding.
I have seen that many authors prefer symmetrical configurations (like 10 poles and 12 slots) but by other side many commercial in-wheel motors (low speed applications) use 46 poles and 51 slots.
The disadvantage I already know is a lower torque compared to a machine with q=0.4 (the 10/12), but on the other hand the LCM is very high so the ripple torque is very low, and the THD is not so severe, so I think it could be a very good option to avoid vibrations problems and ensure a very long useful life that is something very important on this project.
I'm waiting for your comments, thanks a lot!

Mr. Yannis, the 46-poles/51-slots machine have a q=0.37.

My question is more about why I haven't seen any publication about this kind of motor used as a generator, and I only see advantages. I think the main problem is harmonic distortion, but I have no proves to discard it.

15
Do you have any good book/research article related to smart grid planning?

Demand Side Response and integration of renewable.

You are most welcome.

5
How the insufficient damping of low frequency oscillations limits power transfer capability in power system?

Can someone please give me an example?

13
Is it possible to model the line outage in MATPOWER ?

Specially when the network will be separated islands after line outage (radial distribution networks) .

11
Can anyone recommend a PMU simulator to randomly generate data?

Hello!

Please suggest software to randomly generate PMU data.
The data obtained should be as per IEEE format.
Even though it's not in the prescribed format(s) then also any PMU
generator which might be solving the purpose will do.

Thanks in anticipation.

Regards,

Dear Manas,
Thank YOU!
The paper is really helpful.

16
I have monthly load how can I extract daily or hourly load from it?

Hi all, I have monthly load how can I extract daily or hourly load from it?

You may also take a set of  daily or hourly data and see whether this curve you have chosen fits fairly well with this data. If so you may use that curve for interpolation from your monthly data.

you can try curves with polynomials of a different degree.

This is a cumbersome Procedure and still we are not 100% confident of the Results we gt. It is a Rough Approximation.

P.S.

2
Which is the best power systems analysis software for small systems, ergum industrial systems?

7
For a dynamic simualtion of a multi-m/c system with TCSC, what could be the ideal value of initial firing angle?

Dear all,

I want to perform EMTP based dynamic simulation of a multi-machine system having TCSC. One of the reference paper suggests using initial firing angle 8 degrees more than the TCSC's resonant point. The authors have justify this as based on engineering judgement..

Is there any specific limit?

Thank you Parekh Sir.. Will take into consideration.

6
How can we estimate power (RTL level) in RTL Compiler before performing actual synthesis?

Building RTL Power Models in RTL Compiler

It is always good to build power model before performing synthesis

3
In a synchronous machine modelling how do you derive the flux linkage equation in dq coordinate for a synchronous machine modelling?

For mutually coupled windings along d-axis and q-axis

The question could be more precise because there is no mutual couplings between d and q axis. The equations for flux linkages in d and q axis starts from their form in the stand still frame. After transformation from this to the rotor frame (this must be done for all quantities: inductances, resistances, voltages, currents and flux linkages) the final equations for flux linkages shall be derived. Also, the systematic approach can be found in: P. C. Krause, Analysis of Electric Machinery!

• Sándor F. Tóth added an answer:
42
How to measure the difficulty of a Mixed-Linear Integer Programming (MILP) problem?
The intuitive answer is the number of binary variables, when solving the MILP through the branch-and-cut algorithm. But, is the number of binary variables really the main characteristic that increases the computational burden of an MILP?

In the case of the Unit Commitment problem (UC), it has been proven that including the startup and shutdown binary variables decreases its computational burden in comparison with a UC using only commitment binary variables (without the startup and shutdown ones).

So if the quantity of binary variables does not directly influence the computational burden of a UC, how to measure the computational burden of an MILP problem?

I think it is common in MIP optimization to have a few global constraints (e.g., enterprise-wide smooth workflows) whose number doesn't change with the size of operation (the number of decision variables) but at the same time it gets easier to satisfy them when more items are available. The number of "local" constraints can still explode in response to the higher number of variables but this will likely not have any impact on difficulty if the local regions are independent.

2
Inverter for Solar Power System
hi , I am searching on "Inverters used in PV systems". I will be really grateful if someone can help me to get more details on the advancements in the fields.Also what are the project possiblities in this area which can be completed in maximum of 4 months. ?

Hi sir. For solar inverter research, I suggest you could login homepage of some solar inverter manufacturers, then download the datasheet and installation diagram.

Hope it can help for your work.

8
What is the cause of oscillatory instability of power system?

I examine a simple two-machine model of the electrical system, which takes into account field circuit dynamics and  excitation system (Kundur P. Power system stability and control, McGraw-Hill, New York, 1961).

When power generation reaches 1.3 p.u. appears a pair of complex eigenvalues ​​with positive real part. This mode has a frequency of 1.4 Hz.  Analysis of the participation matrix showed that this mode is related to the flux linkage of field winding and excitation system.  I checked the voltage stability using the network dV/dQ curve (using the Jacobian). But the network dV/dQ curve change sign much later.
What is the cause of oscillatory instability of power system model?

You can see the angle-power curves for my model in attach. Green corresponds to the stability, blue - oscillatory instability, red - monotonic instability.

In my case, oscillatory instability is directly related to the action of ARV, coefficient K5 (see Kundur Power Systems Stability and Control p.759)  changes its sign. Should be noted that the model was not included PSS.

• Bala Murugan s added an answer:
3
What software will help me accurately measure dynamic power dissipation of a circuit that is coded in verilog hdl?

I have worked in Cadence NCLaunch tool to measure power dissipation. However, presently I am unable to access Cadence and as there is no freeware available on the net, I am out of options. Please suggest me some other tool for my research purpose

You have to have either Cadence RTL compiler or Synopsys DC, without this if you are run the code to measure the dynamic power, you will receive many questions from the reviewer and at the end you are frustrated about your work. So, better use any one of the tool mentioned above and generate either VCD file or TCF file and calculate the dynamic power. Make sure that your VCD or TCF file covered 100% switching activity while tool read it.

4
How can find data of a real microgrid for designing an MPC-based controller?

I want to design a EMS systems for a MicroGrid that determines real and reactive power set points for components of a real world MG, e.g. DGs, Compensators, Loads etc.

I need all of the information/data about this MicroGrid for design a MPC-based controller.

I prefer that this system includes a PV, a wind turbine, a diesel generator, and a battery storage device.

Let me help you on the way:

9
How do you model the synchronous condenser in DIgSILENT?

Hi,

I want to model the synchronous condenser in DIgSILENT. How can it be done?

Synchronous condenser consume little active power. Moreover, DigSILENT gives error in very low power factors (Simulation not converge). My network is IEEE 14 bus test system.

In DigSILENT, the setting of power flow tap  is only applied to the power flow analysis and synchronous machine exchanges the active power with network in the time domain simulation even in the P=0 condition.