Current clamped, modified series resonant DC-link power converter for a general purpose induction motor drive

A modified power converter topology, derived from the series resonant DC-link converter is proposed in which all switches operate in a resonant fashion to reduce switching losses. The scheme enables PWM control over individual current pulses whereby true PWM over a two pulse period can be achieved to a fair degree of accuracy. The scheme also implements current peak limiting by a simple diode clamp. Improved switch utilization factor, reduced cost burden on filter capacitors and better control over current pulses in the discrete pulse domain could be cited as the main advantages of the circuit over previous configurations. A control algorithm has been developed to achieve simultaneous control over both input power factor and smooth input-output line currents. The auxiliary switch performs PWM on each pulse by devising a simple dynamic solution for the switching instants. Digital simulation results for the developed method are presented. Also, open-loop PWM control at the output has been implemented on a three-phase laboratory prototype and experimental results are presented