A new robust and simple three phase resonant converter

The three-phase parallel resonant power converter has a resonant link working at a relative high frequency typically from 40 kHz and above. Advantages are zero voltage switching, low dv/dt and random modulation strategy, things absent in the PWM-VSI. Disadvantages are resonant voltage peak fluctuations due to load changes and stability of the converter. The problem with link voltage fluctuations is considered solved, this paper highlights the problem of converter stability. Known methods maintain the link resonance by a link current and link voltage feedback where complex high bandwidth measurement equipment is needed. As a consequence there are noise problems and the DC link voltage is often limited to a few hundred volts. A new simple method that maintains the link resonance without the mentioned problems is presented. A robust 5 kW three phase converter is realized; the converter test setup was able to load the converter with 3.8 kW, and an efficiency of 97% was measured.