Fluctuating Current Control Method for a PMSM Along Constant Torque Contours

The dc-link voltage fluctuation problem is more serious for an inverter system which utilizes a single phase ac source. As an effort to reduce the dc-link capacitance, there is a tendency to make torque oscillate in synchronism with the input power. Then, the fluctuating motor power matches the converter power. The key idea is to enforce current oscillation along a constant torque line which only affects the reactive power of the motor. In other words, the proposed method uses the motor as inductive energy storage by controlling the motor flux by the reactive current component. Analytic method for obtaining the current bounds was derived. Also, a practical recursive algorithm was proposed. Simulation and experimental results support the effectiveness of the proposed method.