A multikilowatt polyphase AC/DC converter with reversible power flow and without passive low frequency filters

An efficient ac to dc converter with reversible power flow, which embodies an active, low frequen­cy filter, is presented. A non-dissipatively controlled, nonlinear resonant oscillator is used to extract electric energy directly from the phase pairs of the polyphase supply line and to generate a mixed amplitude and frequency modulated carrier. The demodulated carrier and the therefrom resulting 20 kHz pulse train produces, after being pro­cessed by a high frequency filter, an active, low frequency filtering effect for attenuation of the 360 Hz ripple of the apparently "rectified" three phase supply line.The system is governed by means of a pulse area control mechanism with a verified response time of one 10 kHz cycle, or 100 micro­-seconds. The customary dc link between the three phase line and the converter's 20 kHz pulse processing mechanism in the form of a common rectifier­-filter is completely eliminated. Data obtained from the test of a 3 kW feasibility model are ana­lyzed in support of presentation of the significant aspects of design and technology.