Naturally commutated resonant circuit for soft-switched inverters

Abstract

This paper presents a soft-switched inverter with zero-voltage switching capability aided by a simple quasi-resonant circuit. The quasi-resonant circuit creates zero-voltage instants so that standard voltage-fed inverter can be switched at high frequency without switching loss. Unlike the resonant-link inverter which sets link voltage higher than the input dc voltage, the link voltage in the proposed scheme remains at 1 per unit. Due to the resonant nature of the circuit, the thyristor can be turned off naturally without the need of commutation circuits. The major advantages of the proposed circuit include low-cost and simplicity. The operating principle of the circuit is explained and the operation of the circuit has been verified by SPICE simulation.