Virtual Reduced-Order Plant-Based Speed Sensorless Control for AC Motor Drives With Output LC Filter

The installment of the LC filter is essential for the AC motor drive system, especially for those having a long cable transmission or wide bandgap inverters with high switching frequency operation. These scenarios often encounter a high dv/dt problem, which can be mitigated by implementing the LC filter. However, introducing the LC filter transforms the drive system into a high-order system and adds more state variables. Despite this, achieving speed sensorless control remains essential for enhanced reliability and saved costs. However, rare papers have developed the speed sensorless control for the drive occasion incorporating the LC filter. To fill this important research gap, this work develops a novel back-electromotive force (EMF) modeling based on the weighted current between the filter inductor current and motor stator current. In this case, this new approach converts the three-order LCL modeling to the first-order L modeling case, allowing existing strategies for EMF observation to be directly employed. In this study, the Kalman-filter-based observer is designed and the phase lock loop (PLL) is adopted to estimate the speed and position information. Experimental results validate the efficacy of our new approach for achieving speed sensorless control in AC motor drives with the incorporation of the LC filter.