Analysis and Control of a Hybrid-clamped Four-level π-type Converter

This paper introduces a hybrid-clamped four-level π-type converter for low-voltage (e.g. 380V) motor drive and other applications. It is based on a four-level π-type converter, with two additional switching devices as well as one flying capacitor (FC) to address the dc-link neutral point balancing issue. This converter has more redundant switching states to be selected in each phase-leg, and consequently, can operate under high modulation indices and high power factors with balanced dc-link capacitors voltages. The switching states with their associated output voltage levels have been analyzed. A carrier-based modulation method with an optimized switching state selection has been devised to modulate the converter and regulate the dc-link neutral points' voltages and the FC voltage. The voltages of the three dc-link capacitors and the FCs can be well controlled with a single-ended configuration (inverter or rectifier). Simulation and experimental results have validated the topology, modulation and control strategy.