Investigation on Switching Function Algorithm of Matrix Rectifier under Abnormal Power Supply Conditions

Based on the switching function algorithm of the traditional matrix converter, that of matrix rectifier (MR) is derived in positive and negative phase sequence with four-quadrant capability. Afterward that of MR under unbalanced input voltage conditions is also derived by detecting and using instantaneous values of input voltages. But the gained algorithm in the case is not fully suitable for the unbalanced conditions without any modification, such as amplitude unbalance, initial phase angle unbalance and waveform distortion. This is mainly because the constraints of switching function algorithm would be destroyed, even worse at high desired DC output voltage. The constraints include two aspects: the sum of relative switching functions for an output phase is always zero and the value of each switching function is within [0, 1]. At this point, a simple process method is proposed to meet the constraints to a large extent by means of regulating each switching function according to the actual unbalance before use. Eventually thorough simulations are performed with Simulink6.0 under balanced and unbalanced conditions, inclusive of input voltage and input current waveforms, output DC voltage waveforms, etc. The simulation results prove the theoretical analysis.