Novel Digital Control Method with Pulse Width Modulation for Half-wave Rectified Brushless Synchronous Motors

Abstract

We propose a novel digital current control method for half-wave rectified brushless synchronous motors (HWRB-SM) with a pulse width modulation (PWM) at a fixed switching frequency. For HWRB-SMs, the field magnetic flux must be excited by high-frequency stator currents. Due to the nonlinear dynamics of the diode short-circuiting the field winding, an appropriate mathematical model is required for controlling the high-frequency excitation current. In this study, we developed equivalent models for both the excitation current control and the fundamental one. The proposed method employs a synchronous PWM and resonant controllers to realize high-frequency excitation current control that is robust against the nonlinearity of the diode. The proposed method was validated using an experimental synchronous motor and a digital control system.