CLOSE LOOP INVERTER

Close loop inverter:

What is the difference between open loop and closed loop inverter?

* In Open loop inverter, the output is varying with respect to the input. Suppose, the source of the inverter is not the constant source and input of the inverter is not constant, its varying with respect to time. In this condition, if you have used an open loop inverter than the output of the inverter is also varying. This varying supply can damage the equipment. So, we need a constant output. In another word, the output voltage of inverter must remain constant when supply voltage varies.

* In close loop inverter, a controller is used to control the output voltage. In open loop inverter, the output voltage is not controlled. So, no need to use a controller. But in case of closed loop inverter, we need a controller which can control the output voltage at our reference voltage.

* Cost of open loop inverter is less compared to close loop inverter.

* Open loop inverter is easy to design. But close loop inverter is very difficult to design.

* Close loop inverter is used more in real life application.

How to make a closed loop inverter?

To make a closed loop inverter, we need an open loop inverter. Now we will apply control strategy to this inverter.

1) measure output voltage (Vact) of the inverter.

2) compare Vact to a reference voltage (Vref).

3) difference between output voltage and the reference voltage is called an error and this error is given to the controller (PI, PID)

4) the output of the controller is the modulation index.

5) The modulation index changes with respect to actual output. This modulation index is multiplied with sine wave signal.

6) this sine wave signal is compared with a triangular signal and according to that gate pulse for IGBT is generated. This method is known as the SPWM technique to control the output.

If you need this simulation, comment your mail ID.

For simulation of closed loop inverter:

https://youtu.be/oAAlrNxoGmE

For simulation of open loop inverter:

https://youtu.be/YOrpGGn4mbY