Power Systems Modelling

Power Systems Modelling

  • Cliff Chidzikwe asked a question:
    How do you initialize a user defined excitation system (PID and first order exciter ) in DigSilent ?

    I am getting an error "initial conditions not valid" in DigSilent. I defined my own PID and first order exciter for a synchronous generator. When I run calculate initial conditions I am getting the above error. I am wondering how one can fix this. 

    In have included the following initial conditions in the under Excitation system block diagram definition/Equations. 

    inc(x) =  0 
    inc(x1)= 0
    inc(x2)= 0

    -where x, x1 and x3 are state variables for the integrator, derivative and exciter blocks respectively. 

  • Oussama Bouzid added an answer:
    How can i measure the beam waist with high precision?

    Hello dear researchers, i need to know how i can measure exactly the beam waist W, i know that it's a 1/e2 of the whole output power but i cannot find a way to measure it experimentally !! 


    Oussama Bouzid

    Thank you very much dear Shigeo for your detailed answer.

  • Debasish Mondal added an answer:
    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



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

    In H-infinity case




     How will I decide  the variables z and y?

    Debasish Mondal

    The choice of Z depends upon the designer which variable of the plant to be measured. 

    The variable y is also to be decided by the designer, which state of the plat to be taken as feedback.

  • Yasaman Majd added an answer:
    Does anybody know what is the effect of increasing the stages of ring oscillator on power consumption and frequency?

    does anybody know what is the effect of increasing the stages of ring oscillator on power consumption and frequency?if we increase the stages power must be increased or not?and also about frequency

    please do me a favor and help me  

    Yasaman Majd

    Thank  you very much

  • Adnene Haj Hamida added an answer:
    How to model a 220kV, 42km long transmission line?

    For Voltage Drop and power loss calculations.Can it be modelled as 'T' or 'Pie'?

    The Total Inductance of the Line is measured as 0.04H and Capacitance as 0.4 microFarad.

    Adnene Haj Hamida

    for the very long transmission lines we use T model but for the normale lines length we use "Pi" model. (R,X and C)

    for your question you must use "pi" model for this line to determine the voltage drop and power losses.

  • Debasish Mondal added an answer:
    Any advice on optimal location of facts and DG?

    if i have solve optimal power flow problem for following function
    1. fuel cost
    2. active power loss minimization
    3. reactive power loss
    4. voltage deviation minimization
    5.Lmax improvement

    how to find out where optimal location of DG-TCSC-SVC-UPFC-IPFC-STATCOM-DSTATCOM

    and which case improvement when find its optimal location

    Debasish Mondal

    you can for optiumization of any one of the said objective or may solve for multiobjective optimization problem

  • Ngoc-Tuan Vu added an answer:
    How can I prove the principle of dispatching active and reactive power from Electric vehicles? (V2G)?


    I need to prove the bidirectional power flow of EVs (V2G and G2V). What will be the control variables that need to be determined to do the same? I am working on the context of EV planning in smart distribution network.

    Ngoc-Tuan Vu

    Let's imagine, it simply depends on the direction of the torque applied on the motor / generator axis (such as when accelerating or braking). I think you can find it in some fundamental books for the electric machine

  • Bala Dabhade added an answer:
    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

    Bala Dabhade

    Hello Aripriharta Sir,

    I am simulating c program compiled for alpha (A6) architecture using gcc cross compiler.

    My goal is to generate thermal profile of c program(any c application). I am able to get power statistics from wattch but I need ptrace file which I can use as input for HotSpot to get thermal profile along with floor plan. I have floor plan ready for alpha-A6.

    I found may places we need to change the code of wattch simulator to get the ptrace file, however I am not able to figure out where to do exact changes so that i can get power trace file in wattch code.

  • Jeremy Lin added an answer:
    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.


    Jeremy Lin

     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:
    How do I determine a mono-machine equivalent model of real power system?


    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

    Mohamed Abd Elwahab Ali

    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.

  • M.G. Rabbani added an answer:
    Simple Newton-Raphson Matlab 4-bus Voltage equation from power?


    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.


    M.G. Rabbani

    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:
    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,

    Thanks in advance

    Yasser E Abueldahab

    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:
    When the single line outage in a power system make the system insecure?


    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?


    Lionel R Orama

    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.

  • Gerro Prinsloo added an answer:
    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.

    Gerro Prinsloo

    Dear Mahendra

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



  • Varun Chitransh added an answer:
    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?

    Varun Chitransh

    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

  • Srete Nikolovski added an answer:
    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

    Srete Nikolovski

    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.


  • Pouyan Asgharian added an answer:
    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?

    Pouyan Asgharian

    Hi ,

    i have this problem too!if you find your answer , please help me.

    thanks alot

  • Francisco Arrau added an answer:
    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!

    Francisco Arrau

    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.

  • Inno Davidson added an answer:
    Do you have any good book/research article related to smart grid planning?

    Demand Side Response and integration of renewable.

    Inno Davidson

    You are most welcome.

  • Morteza Seddighighachkanloo added an answer:
    How the insufficient damping of low frequency oscillations limits power transfer capability in power system?

    Can someone please give me an example?

    Morteza Seddighighachkanloo


  • Morteza Seddighighachkanloo added an answer:
    Is it possible to model the line outage in MATPOWER ?

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

    Morteza Seddighighachkanloo


  • Kishore Bhaurao Khiradkar added an answer:
    Can anyone recommend a PMU simulator to randomly generate data?


      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.

    Kishore B. Khiradkar

    Kishore Bhaurao Khiradkar

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

  • Pisupati Sadasiva Subramanyam added an answer:
    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?

    Pisupati Sadasiva Subramanyam

    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.


  • Mostafa Eidiani added an answer:
    Which is the best power systems analysis software for small systems, ergum industrial systems?
    Mostafa Eidiani

    You can see also this link


  • Meera Karamta added an answer:
    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?

    Meera Karamta

    Thank you Parekh Sir.. Will take into consideration.

  • Sivanantham S added an answer:
    How can we estimate power (RTL level) in RTL Compiler before performing actual synthesis?

    Building RTL Power Models in RTL Compiler

    Sivanantham S

    It is always good to build power model before performing synthesis

  • Muharem Mehmedovic added an answer:
    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

    Muharem Mehmedovic

    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:
    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?
    Sándor F. Tóth

    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.

About Power Systems Modelling

Simulation of Power Systems as a whole and of each separate component

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