Current stiff converters with resonant snubbers

摘要

A current stiff power conversion system, such as a rectifier, inverter, or AC-to-AC converter is provided wherein power converter switching devices in the power conversion system may be switched at or near zero voltage conditions to minimize or eliminate switching losses and increase switching frequencies. Zero voltage switching conditions are achieved by providing a snubber capacitor across each switching device in the power conversion system, and connecting an active commutation unit, including an inductor and an active commutation unit switching device connected in series across DC bus lines in parallel with the bridge of power conversion switching devices. Zero voltage switching conditions for the power conversion switching devices are achieved by controlling the power conversion switching devices and the active commutation unit to establish a resonance between the snubber capacitors and the active commutation unit to drive the voltage across incoming switching devices in the power conversion system to at or near zero. Zero current switching of the active commutation unit switching device, and reduced switching device stress in the power conversion system, is achieved by controlling the power conversion switching devices to establish zero current switching conditions and a desired snubber driving voltage for the active commutation unit before the active commutation unit is turned on to establish the resonance condition. Since zero voltage switching conditions for the power conversion switching devices is achieved each switching cycle, the power conversion system may be controlled using a PWM control scheme.