IPMSM Sensorless Control by Injecting Bidirectional Rotating HF Carrier Signals

Rotating high frequency (HF) carrier signal injection method is commonly used in interior permanent magnet synchronous machines' (IPMSMs) sensorless control due to its simple principle. However, the accuracy of the rotor position estimation will decrease because of some adverse impacts, such as system delays, stator resistance, cross coupling effect, and inverter nonlinearities. In order to solve these problems, a strategy to inject bidirectional rotating HF carrier signals into the machine is proposed in this paper. Differing from those conventional methods, the proposed method injects simultaneously two HF carrier voltages with different rotational frequencies and directions. Four independent equations are constructed and obtained by demodulating every frequency components in the response currents. By solving these four equations, the rotor position can be calculated directly, which effectively minimizes the effects of the stator resistance, system delays, and inverter nonlinearities. In addition, the compensation of the cross coupling effect on the rotor position estimation is analyzed and deduced in detail to improve the estimation accuracy. Finally, the experimental results on an IPMSM demonstrate that the rotor position with good steady-state and dynamic performance can be obtained accurately by using the proposed sensorless control strategy.