Abstract: An apparatus and method is disclosed for an improved AC--AC series-resonant converters incorporating power pulse modulation with internal frequencies of tens of kHz is applied to a series-resonant converter system for generating synthesized multiphase bipolar waveforms with reversible power flow and low distortion. The high pulse frequency allows the application of the principle of modulation and demodulation for fast system response. Switches are required which have bidirectional current conduction and voltage blocking ability. The conventional series-resonant AC--AC converter applies a total of 24 anti-parallel thyristors. The circuit configuration of the present invention is a series-resonant AC--AC converter with only 12 thyristors. Use of the converter results in a higher efficiency and lower costs.

Abstract: An improved control circuits is disclosed for use with a resonant converter having a resonant circuit and a first and a second plurality of switches for transferring electrical power between first and second terminals. The improved control circuit comprises a power transfer control or an outer control loop and a resonant circuit control or an inner control loop with the resonant circuit control having a predictor circuit. The power transfer control regulates the electrical power transferred between the first and second terminals through selective conduction of the first and second plurality of switches for selectively initiating oscillation of the resonant circuit to provide resonant pulses of the resonant circuit.