A Novel DC-link Voltage Observer with Time Delay Compensation for Small DC-link Capacitor-based IPMSM with EEMF Based Sensorless Control

DC-link voltage sensor is very important for permanent magnet synchronous machines (PMSMs) control system, especially for small dc-link capacitors-based PMSMs control system where dc-link voltage is always fluctuating. However, the voltage sensor is expensive and may suffer measurement errors and failures in the harsh environment. Therefore, this paper proposes a quasi-proportional integral resonant type of voltage observer to estimate the dc-link voltage accurately based on inverter power balance. The proposed voltage observer could lower the cost and increasing the system reliability. In addition, the estimation delay in the proposed observer due to low pass filter (LPF) will cause the large voltage observation error since the dc-link voltage is fluctuating. To eliminate the effect of estimation delay on the system, this paper predicts and reconstructs the estimated voltage based on the periodicity of fluctuating dc-link voltage. The accuracy of the dc-link voltage observer and the efficiency of the delay compensation strategy have been demonstrated by the experiments.