Rotating Restart Method for TPFS Inverter-Fed Sensorless PMSM Drive System Based on Dual Effective Voltage Vectors Injection

This article proposes a solution to the challenge of achieving a reliable restart in sensorless permanent magnet synchronous motors transitioning from a three-phase six-switch inverter to a three-phase four-switch (TPFS) inverter due to faults. The proposed rotating restart method employs the injection of dual effective voltage vectors to synthesize the equivalent zero-voltage vector, under unbalanced capacitor voltage conditions in the TPFS inverter. This synthesis is achieved by incorporating the capacitor voltage offset into the duration calculation of the dual effective voltage vectors. Once the main power supply is restored, the dual effective voltage vectors are injected into the motor windings through the TPFS inverter, producing the short-circuit current influenced by the back electromotive force. The method utilizes the accumulated short-circuit current values to estimate the initial rotor position and speed, enabling a smooth and efficient rotating restart. This innovative method enhances the accuracy of rotor position and speed detection, reduces impulse current, and ensures the fault-tolerant operation of the system. The theoretical analysis is validated through experimental results, demonstrating the effectiveness and reliability of the proposed method.