Optimal Switching of Controlled Rectifiers

Abstract

This paper discusses a linear programming approach for designing switching signals for controlled rectifiers to achieve a low input current & output voltage total harmonic distortions. The focus here is on fully controlled rectifiers made with four-quadrant MOSFET based switches. This topology, unlike thyristor based rectifiers, can be turned ON or OFF anytime. Yet another assumption made here is that the current drawn by the load is constant. The basic idea for designing the waveform is to first timediscretize its one period. This discretization, along with Parseval's identity lead to a linear programming formulation for minimizing a weighted sum of total harmonic distortions of the input current and the output voltages. The LPs so obtained can be solved efficiently using standard solvers to obtain the switching instants. The method can be used for both single phase and three-phase rectifiers. Simulations are provided for corroboration.