A Voltage Source PWM Rectifier-Inverter with Feed-Forward Control of Instantaneous Power.

In general, diode rectifiers with electrolytic capacitors on the DC side have been used as DC power supplies for voltage source inverters. This type of rectifiers, however, causes many problems such as poor power factor and harmonics. Recently, voltage source PWM rectifier-inverters have been studied to provide the following advantages; (1) harmonic-free on both AC sides; ( 2) unity power factor on the input AC side; (3) power flow of either direction or power regeneration; (4) reduction of the DC capacitor. It is, however, difficult for a conventional one to regulate the capacitor voltage on transient states because of having only a voltage feed-back loop.This paper describes a voltage source PWM rectifier-inverter with feed-forward control of instantaneous power. Based on the pq theory, the instantaneous power which is calculated in the control circuit of the inverter is fed forward to the control circuit of the rectifier. The feed-forward control of instantaneous power makes a great contribution to sufficiently suppress voltage fluctuation of the DC capacitor on transient states. Transient characteristics are discussed and some interesting experimental results of a laboratory model are shown.