I am currently working on a project aiming to control the amount of current flowing through a resistance from 0 to nominal in a continuous manner. The catch is that the power is 230 VAC 50 Hz. My first iteration at it was through phase angle control. However, the current look is horrible (many harmonics).
Thus, I am trying to lessen the amount of harmonics in order to comply with IEC 61000-3-2 (EU norm on current harmonics).
My first thought was to use a full bridge rectifier with a high frequency PWM controlled MOSFET. As the load is only resistive, it creates an in phase, very sinusoidal looking current. Here is the circuit (with 1/10 of input voltage to not overdrive the only MOSFET I knew in the library of the simulation software):
Here is the look of the current:
Thus I thought about filtering those high frequency harmonics by putting a filter in place. However even with a good cutting frequency, I don't find good values for LC filter cause with a smaller cutting frequency comes a bigger current / voltage phase and thus reducing power factor.
Next thing I thought about is to place an active PFC between the full bridge rectifier and the resistive load. I think I would work but is to my mind quite overkill (and quite expensive for high power: it’s around 2 kW).