On-load voltage distortion compensation method using disturbance observer for SPM machines with closed slot

This paper proposes an on-load voltage distortion compensation method, in which the voltage distortion is mainly produced in the surface-mounted permanent magnet machines having closed slot. Apart from the voltage distortions caused by the inverter, such as dead time and inverter non-linearity, the on-load voltage distortion has relatively large magnitude dependent of machine speed. As a result, it causes a significant distortion of current waveforms and deteriorates control performance. Hence, a voltage disturbance compensation method using a disturbance observer is proposed and implemented. Based on the machine model, the disturbance observer is chosen which helps to observe a voltage disturbance, while the error between measured and estimated currents is minimized. The disturbance observer only compensates the sixth-multiple harmonic components of the inverter voltage in synchronous reference frame. The harmonic compensator with multiple narrow-band pass based adaptive filter is proposed and implemented in the feedback loop with current controllers. The observed voltage disturbances are compensated to the reference voltages. In addition, robust performance of the proposed method is shown against the parameter uncertainties. The effectiveness of the proposed compensation scheme is validated by the experiments.