Get the low voltage ride through graphs

I have been using a programmable voltage source to emulate my grid but now I need to follow a specific standards to test the grid codes compliance such as low voltage ride through and high voltage ride through. I was thinking about creating a Matlab function but I was wondering how to get the low and high voltage ride through curves

Answer 1

[Suraj Kumar]

Hi Ali,

To create a MATLAB function that simulates the LVRT and HVRT curves, you need to first define the voltage profiles based on the specific grid codes or standards you are following. Assign a time to each key point, indicating when the voltage changes occur and how long they last.

You can refer the following code for better understanding:

function [time, voltage] = simulateLVRT(duration, timestep) 
lvrt_start = 0.1; 
lvrt_end = 0.6; 
recovery_time = 1.0; 
nominal_voltage = 1.0; 
lvrt_voltage = 0.7; 
time = 0:timestep:duration; 
voltage = nominal_voltage * ones(size(time)); 

for i = 1:length(time) 
    if time(i) >= lvrt_start && time(i) < lvrt_end 
        voltage(i) = lvrt_voltage; 
    elseif time(i) >= lvrt_end && time(i) < recovery_time 
        slope = (nominal_voltage - lvrt_voltage) / (recovery_time - lvrt_end); 
        voltage(i) = lvrt_voltage + slope * (time(i) - lvrt_end); 
    end 
end 
end 

Then using the voltage levels, and timings, you can plot the voltage profile on a graph with time on the horizontal axis and voltage on the vertical axis. 

figure; 
plot( time, voltage); 
xlabel('Time (s)'); 
ylabel('Voltage (pu)'); 
title('LVRT Curve'); 
grid on; 

The attached image shows the LVRT curve plotted using the MATLAB function:

You can similarly create the HVRT curve.

For more information about “plot” function you can refer the following documentation:

1. https://www.mathworks.com/help/matlab/ref/plot.html

Hope this helps!

[Ali]

Thank you for the answer. I got an error simulating this code . the idea that I have a 3 phase programmbale voltage sourece connected to the load. From the voltage source i can should the voltage I need at a time. Then I connected a voltage relay connected to breaker so if the voltage goes less than the threshod the grid will disconnect. I tried to put this code in the function it gave me inputs duration and timestep and output voltage and time. I think the function should take the voltage and time from the programmable voltage source and then decide if the voltage is acceptable or not

[Suraj Kumar]

Can you tell me more about the error that you are getting while executing the code ?