An isolated DC-DC boost converter using two cascade control loops

This paper presents an isolated DC-DC power converter designed to operate as the primary stage of an on-board DC-AC power supply for diesel-electric engines. The DC-AC power supply must provide a sinusoidal waveform of 127 V RMS from the 72 V DC bus of the engine. The DC-DC push-pull current-fed power converter has been used to obtain an isolated 200 V DC output voltage from the available 72 V DC bus engine. This power converter operates as a boost converter with constant frequency and duty cycle greater than 50%. Two control loops operating in cascade mode were used. A fast inner current loop regulates the boost inductor current, whereas an external control loop keeps a constant output voltage. Experimental results have been obtained for a 300 W laboratory prototype operating at 50 kHz. The power converter efficiency was 93% at full load, and the output voltage regulation was less than 1% for 10% to 100% load changes.