Modeling, simulation, and analysis of permanent-magnet motor drives. II. The brushless DC motor drive

For pt.I see ibid., vol.25, no.2, p.265-73 (1989). The authors develop a phase variable model of the BDCM (brushless DC motor) and use it to examine the performance of a BDCM speed servo drive system when fed by hysteresis and pulsewidth-modulated (PWM) current controllers. Particular attention was paid to the motor large-signal and small-signal dynamics and motor torque pulsations. The simulation included the state-space model of the motor and speed controller and real-time model of the inverter switches. Every instance of a power device turning on or off was simulated to calculate the current oscillations and resulting torque pulsations. The results indicate that the small- and large-signal responses are very similar. This result is only true when the timing of the input phase currents with the back EMF (electromotive force) is correct. The large-signal and small-signal speed response is the same whether PWM or hysteresis current controllers are used. This is because, even though the torque pulsations may be different due to the use of different current controllers, the average value which determines the overall speed response is the same.<
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