Adaptive Impedance Reshaping Strategy for SPMSM Operating With Tight Speed Regulation

Ensuring the stability of cascaded systems with constant power loads (CPLs) remains a critical challenge due to their negative incremental input admittance at low frequencies, which induces instability—particularly at higher power levels. In tightly regulated SPMSM drives, the inverter–machine behaves as a CPL at the dc input; hence the source–dc-link–drive constitute a cascaded system. This paper presents a novel adaptive parallel virtual impedance control strategy to enhance the dc-link stability of Surface Permanent Magnet Synchronous Motors (SPMSMs) under tight speed regulation, where dc-link stability denotes a well-damped dc bus—i.e., absence of sustained low-frequency oscillations caused by source–load impedance interaction—maintained asVbusand load power change. The method achieves this by reshaping the input impedance across varying bus voltage and power. By employing the Middlebrook feedback theorem, the input impedance and sensitivity functions are derived to identify instability sources. A parallel virtual impedance with power and voltage adaptability is then formulated, alongside a compensation controller transfer function to realize the virtual impedance. To address implementation complexity, a simplified version of the controller is proposed, eliminating the reliance on circuit parameters or additional sensors while maintaining dynamic performance. A 160W SPMSM prototype system, validated experimentally with real-time deployment on a TI C2000 F28379D microcontroller, demonstrates the feasibility and robustness of the proposed approach across varying power and voltage levels.