A voltage‐source PWM rectifier‐inverter with feedforward 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. Rectifiers of this type, however, cause 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. However, it is difficult for a conventional voltage‐source PWM rectifier‐inverter to regulate the capacitor voltage on transient states because it has only a voltage feedback loop. This paper describes a voltage‐source PWM rectifier‐inverter with feedforward 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 feedforward control of instantaneous power contributes greatly 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.