부산대학교 도서관

The rotating high-frequency (RHF) signal injection method is widely adopted for the initial position estimation in sensorless permanent magnet-assisted synchronous reluctance motor (PMa-SynRM) drives due to its simple implementation. However, the position estimation accuracy of the conventional method may be seriously deteriorated by the dead-zone effects of the inverter and the cross-saturation effects of the machine. Thus, to improve initial position estimation accuracy, a strategy to apply dual RHF signals is proposed in this paper. Different from the traditional solution, the proposed method sequentially injects dual RHF carrier voltages with the same frequencies but different amplitudes into the machine. Objective equations that consider the dead-zone and cross-coupling effects can be extracted from high-frequency response currents in turn. After the simple calculation, the initial position can be obtained directly and accurately, which effectively minimizes the influences of machine cross-saturation and inverter nonlinearities. The influence of the system delay on the rotor position estimation is also analyzed and deduced in detail. Finally, experimental results on a 5.5-kW PMa-SynRM indicate that the proposed method can achieve precise initial position estimation under any rotation position.