Sensorless Control of Electrically Excited Synchronous Motor Based on Pseudo Random High Frequency Signal Injection at Low-Speed Region

Nowadays, the cascaded H-bridge inverter-based high-voltage electrically excited synchronous motor (EESM) drive system has been widely used in the many industry fields. To reduce the hardware cost and improve the dynamic performance at the low-speed region, the field-oriented control (FOC)-based sensorless drive strategy is investigated in this work. At the low-speed region, a pseudo random high-frequency signal injection method is proposed to detect the rotor position and the speed for EESM drives. In details, a pre-designed pseudo high-frequency voltage is injected to the d-axis reference voltage. Then, a high-frequency mathematical model of EESM is established for the current response analysis. By using the dq-axis current response, the rotor position information can be extracted for low-speed operation. As compared to the conventional high-frequency signal injection, the noise pollution is mitigated by using random signal injection method. In simulation-based case studies, the effectiveness of noise mitigation and rotor position estimation for low-speed operation are verified.