Harmonic Currents Estimation and Compensation Method for Current Control System of IPMSM in Overmodulation Range

For high performance and wide speed range control of an IPMSM, using the overmodulation range of an inverter is one of the effective methods. However, to use this overmodulation range with the closed loop currents control system, there are many problems occur and the main problem is caused by the harmonic currents generated from harmonic voltages in the inverter output voltages. Therefore, in the ususal control methods of an IPMSM in the overmodulation range, these problems are avoided by not using the closed loop currents control or by using the closed loop currents control with the filters in the feedback part. With these methods, the problems from harmonic currents can be solved, but the other new problems also occur too. The method of harmonic currents compensation is also proposed and this method seems to be more effective than the others. However, in this method, the proposed harmonic currents estimation method is quite difficult in practical use, because the real value of the inverter output voltages are used, then the carrier frequency components will cause an aliasing problem in the estimation part and this problem will become more serious when the carrier frequency is high. To solve the above problem, in this paper, we propose the harmonic currents estimation and compensation method based on the inverter harmonic voltages model. In our proposed method, we use only the inverter commanded voltages in the harmonic voltages estimation, then this method is more easy for the practical use. Moreover, by using the inverter harmonic voltages model, the data of both amplitude and phase angle of harmonic voltages are available, then we can estimate the harmonic currents by using only simple phasor method compared with the complex dynamic model method in the former. The experimental results are shown to confirm our proposed estimation and compensation methods.