Single Phase Active Rectifier

To use the rectifier, we have two different types. One is a regular rectifier and the second is an active rectifier. Typical rectifiers use thyristors. The thyristor blocks one current and allows the current to flow in only one direction. But by Using Thyristor, the rectifier have such high harmonics current and have low power factor caused by high harmonics. That means, it has really low efficiency. So we can use active rectifier which use IGBT or MOSFET and control the signal with PWM generator. For generating PWM signal, we can use PLL / PI controller and PWM generator.  

 

First, we need to get a voltage measurement data for generating beta signal. And then we can generate alpha signal by using two low pass filters with time constant 1/(2*pi*50Hz). So we can create a 90-degree phase shift signal with a half amplitude. So we have to double the amplitude. That signal will be an alpha signal. With that signal we can create sin wt, and cos wt.

This signal allows you to create a reference voltage to supply to the PWM generator. Controller have PI Controller and PR Controller. For PI Controller, we supply error of Voltage that made by comparing between V_DC and V_DC_ref. The signal will be a constant value of current. And then we can multiply a cos wt signal with the current signal that pass the PI Controller. So we can create I_ref. Comparing I_ref and I_inv we can make an error signal and using PR controller we can make V_ref. That reference Voltage is used on PWM generator