DC-AC series-resonant converter system with high internal frequency generating multiphase AC-waveforms for multikilowatt power levels

A new method of power pulse modulation with internal frequencies of tens of kHz which is also suitable for multikilowatt power levels is applied to a series-resonant converter system for generating synthesized multiphase bipolar waveforms with reversible power flow. The power circuitry of the converter is provided with one single high-frequency resonant link in the direct energy path. Natural current commutation of the thyristors is obtained by the use of a series-resonant circuit for power transfer and control. Consequently, switching losses can be reduced to a minimum without compromising the reliability of the solid-state components. The high pulse frequency allows the principle of modulation and demodulation to be applied for fast system response and output waveforms with reversible power flow with low distortion. Test results of a converter system generating three phases, sinusoidal waveforms independent of the load characteristics, demonstrate the significant aspects of this class of power conversion. The material presented indicates the possibilities for fast-acting polyphase dc-to-ac and ac-to-ac converter systems.