A Single Sampling Double Update Modulation Method to Enhance Low-Carrier Ratio Operation

To solve problems of low-accuracy synthetic voltage vector, large current ripple, and poor stability in sensor/sensorless control of permanent-magnet synchronous motors (PMSMs) under low-carrier ratio operations, a single sampling double update space vector pulsewidth modulation (SSDU-SVPWM) is proposed. In this method, the phase current is sampled only once, however the target voltage vector is calculated once but update twice in one PWM period. Each PWM period is divided into the first half and the second half. Two voltage vectors with the same amplitude and different delay angles are executed in the first and the second half, respectively. In comparison with the traditional method of compensating an average delay angle of 1.5 T _s , the proposed SSDU-SVPWM compensates 1.25 T _s and 1.75 T _s for the first half and the second half sequentially. It reduces the synthetic error of the target voltage vector, lowers the phase-current ripple, and improves the efficiency and stability of the system. Finally, the effectiveness of the proposed scheme was verified both on sensor and sensorless control of PMSMs.