A new high-performance AC-to-AC conversion system

A new high-performance variable-voltage variable-frequency (VVVF) AC-to-AC conversion system is proposed. This system consists of an AC/DC SCR rectifier, an LC DC-link, and a three-phase DC/AC PWM inverter. The rectifier is operated under cosine-mode feedback which linearizes the closed-loop control characteristics. The PWM inverter receives gating signals from a ROM-based modulator with off-line computed PWM patterns. In this way, the inverter output frequency varies with the controlled clock frequency and the magnitude of the AC output voltage is regulated by the SCR rectifier. Without on-line microprocessor computations or discrete circuit implementation, this system features quick output response and low control complexity. Laboratory experiments have been performed to verify this idea and satisfactory results have been recorded