Modelling and control of a high power pulse width modulated synchronous rectifier

The authors present a detailed analysis of a high-power pulse-width-modulated (PWM) synchronous rectifier, operated at low switching frequency. A low-frequency PWM technique is used to control the high power rectifier. Synchronous pulse width modulation based on precalculated and stored optimized pulse patterns is used. The proposed configuration provides DC voltage equal to that of a conventional rectifier. This eliminates the use of a transformer at the input of the rectifier. A general model for the overall system is obtained. The derived low-frequency model presents a time-variant and nonlinear system. Using transformation of the reference frame and small-signal linearization around the steady-state operating point, a linear system is obtained. Various transfer functions are derived from the resultant linear, time-invariant system. The transfer functions derived are utilized in the design of the feedback regulators. Using the proposed model, a phase and amplitude control strategy is used to control the input power factor and DC link voltage. Predicted results are verified by computer simulation and PECAN.<<ETX>>