A SVPWM algorithm based on four-switch three-phase inverter for PMSM under the imbalance of bus capacitor voltage

In a four-switch three-phase inverter-powered permanent magnet synchronous motor system, the capacitor voltage fluctuates due to the unequal capacitance and the charging and discharging of the bus capacitor. As such, the accuracy of motor vector control becomes significantly affected and even causes the shutdown of the motor drive system. Therefore, this study proposed a space vector PWM (SVPWM) algorithm that considers capacitor voltage imbalance. In the case of voltage basic vector offset, this algorithm first constructs a new orthogonal voltage basic vector and takes the offset modulation range as the constraint condition to synthesize a new target voltage vector. Compared with the traditional SVPWM algorithm, the proposed SVPWM algorithm controls the capacitor voltage fluctuation range in a reasonable range, simplifies the calculation, improves the three-phase stator current asymmetry, and reduces the current harmonic content. Simulation and experimental results demonstrate the effectiveness and feasibility of the proposed SVPWM algorithm.