PV Array output fluctuation with static inputs.

Hi community,

I'm experimenting with the PV Array block in Simulink (Specialised Power Systems) as part of a university project.

I have observed that when all parameters are static (Irradiance, Temperature, Load Resistance), the output voltage & current fluctuate. I am struggling to understand how this fluctuation is occuring with static inputs.

The model and outputs are as seen:

For context, the simulation requirement of my project involves finding the maximum power output of an array in half-hour blocks using historic temperature and irradiance data, across a 24hr period. As such the simulation time is 48 (24hrs in 30min blocks), and the model is configured as fixed-step 1s.

Any guidance would be greatly appreciated.

Answer 1

[Aishwarya]

Hi Luke,

As per my understanding, the Simulink model generates unexpected oscillating voltage and current outputs when “PV array” block is given constant irradiance and temperature.

After reviewing the attached Simulink model, seems like the “PV array” block is used in discrete system. The “PV array” block has an algebraic loop in it. By default, the algebraic loop in the internal model of the “PV array” block is cut using a one-simulation-step time delay for discrete systems. This approach can cause numerical oscillations if the sample time of the simulation is too large.

In the “PV array” block, by default the "Break algebraic loop in internal model" parameter is selected. Deselecting this parameter, will in removing the oscillations observed in voltage and current. Here are the steps for the same:

1. Right-click on “PV Array”
2. Go to “Advanced” Tab
3. Uncheck “Break the algebraic loop in internal model” parameter.

Please refer to the “Advanced” section of the below documentation for more details on “PV array” block: https://www.mathworks.com/help/sps/powersys/ref/pvarray.html

Also, refer to the following MATLAB Answer for more information:

https://www.mathworks.com/matlabcentral/answers/466337-why-do-i-get-algebraic-loop-error-when-using-pv-array-block

I hope this help.

Best Regard,

Aishwarya Palli