Simulation of Unbalanced Loads in Simulink

https://www.mathworks.com/matlabcentral/answers/602365-three-phase-unbalanced-load#answer_1161445

I make reference to the above question but in particular, I will like to get a more detailed explanation from Sabin who has answered the question in two different occasions. Could you kindly give more insight on the exact use of Programmable Voltage Source (Three-Phase) or a Controlled

Voltage Source (Three-Phase). The attachment is what I have done with Programmable Voltage Source (Three-Phase). How do I use it to get external input connected as it could done with Dynamic Load (Three-Phase) which is used for balanced load?

Answer 1

[Shivam Gothi]

Hello @Uchenna Johnpaul,

As per my understanding, you are tring to implement a three phase unbalanced dynamic load. You want the external inputs “P” (Active power) and “Q” (reactive power) for controlling it.

As correctly pointed out by you, the “Dynamic Load (Three-Phase)” is used for balance three-phase dynamic load. In order to implement unbalanced dynamic load, you can go via any of methods as suggested by @Sabin in the MATLAB answer post:

https://www.mathworks.com/matlabcentral/answers/602365-three-phase-unbalanced-load#answer_1161445

Those methods are very good to simulate unbalanced three phase supply. But as per my understanding, if you want to simulate three-phase unbalance dynamic loads with “P” and “Q” as inputs, the below given workarounds will be good to start with.

1) Use “Dynamic Load” block

This block is found inside the library “Simscape / Electrical / Passive”. Refer to its documentation:

https://www.mathworks.com/help/sps/ref/dynamicload.html

It is used to simulate unbalanced dynamic load for single phase supply. However , you can use it with three phase by making the following changes:

1) Open the “block parameters” and change the “Load Type” property to “AC” as shown in below figure:

2) You can connect them in star or delta configuration for three phase as shown below:

As it is an unbalanced dynamic three-phase load, you have to provide the active power and reactive power inputs for all the three phases as seen in the above attached images.

I hope you find it useful !

[Uchenna Johnpaul]

Thank you @Shivam Gothi. I will look at it.

[Uchenna Johnpaul]

Thank you @Shivam Gothi for your suggestion. These phases get connected to a2, b2 and c2 of the V and I sensor. I believe it would work but this arrangement give very high measurement values for voltage and current (in powers of 10exp 8). Please what do you think could be the reason for this.

[Shivam Gothi]

Hello @Uchenna Johnpaul,

Can you please share the simulink model or its screen-shot?

It will be usefull in investigating how you have connected VI sensor and power supply to the load. It will also help to find the reason behind high measurement.

[Uchenna Johnpaul]

@Shivam Gothi, thank you for your willness to help. In the Unbalanced Dynamic Load subsystem is the image I pasted earlier today.

Code: https://drive.google.com/file/d/1M36J9M5Oluv2IJZqoimrTTreqUHRrOcr/view?usp=sharing