Enhanced DC-link voltage utilization for sliding mode controlled PMSM drives

Sliding mode control (SMC) can be considered for torque regulation of permanent magnet synchronous machines (PMSMs) when fast transient response and/or robustness under parameter uncertainties are required. In some particular applications, a voltage harmonic injection technique that enhances the dc-link voltage utilization should be incorporated into the controller to operate at high speeds. Although this is straightforward for pulsewidth modulated (PWM) drives, a convenient definition of the sliding surfaces and an appropriate injection procedure must be implemented when using SMC. In this work, a novel approach to generate zero-sequence voltage harmonic injection in surface-mounted (SM) PMSM drives controlled by a fixed switching frequency first-order SMC is proposed. A theoretical analysis is provided verifying the sliding mode existence and demonstrating the system stability when the sliding mode is reached. Finally, experimentation is carried out in an off-the-shelf PMSM drive, where two voltage injection patterns are tested. In both cases, the dc-link voltage utilization is extended by a 15%, confirming the validity of the proposal.