DC-to-AC Series-Resonant Converter System with High Internal Frequency Generating Synthesized Waveforms for Multikilowatt Power Levels

A new method of power pulse modulation with internal frequencies of tens of kHz and suited for multikilowatt power levels is applied to a series-resonant converter system for generating synthesized unipolar and bipolar waveforms. The high pulse frequency allows the principle of modulation and demodulation to be applied for fast system response and output waveforms with low distortion and prevents excessive stresses on components. Natural current commutation of the thyristors is obtained by the use of a series-resonant circuit for power transfer and control. Test results of a 4-kW thyristor converter system generating sinusoidal and nonsinusoidal waveforms independently of the load characteristics demonstrate the significant aspects for this class of power conversion. The material presented indicates the capability of the system to avoid excessive component stresses as well as the possibilities for fast-acting four-quadrant dc-to-dc, single-phase or polyphase dc-to-ac and ac-to-ac converter systems.