Adaptive Current Observer Design for Single Current Sensor Control in PMSM Drives

A 3-phase permanent magnet synchronous machine (PMSM) drive system usually requires at least two current sensors for phase current measurements to achieve high performance control. When there is only one current sensor working in the drive system, accurate current observers are critical to ensure the control performance. In this article, a novel adaptive current observer-based single current sensor (SCS) control strategy is proposed. In the proposed approach, an augmented current state observer is built based on the PMSM dynamic equations with the consideration of machine parameter variation and system uncertainties. To ensure a good SCS control performance in the time-varying speed condition, a new computationally efficient methodology toward a desired pole placement for the adaptive observer gain design is also proposed. More specifically, the proposed observer gains can be calculated analytically for the desired dynamic performance. Compared with the existing methods, the proposed current observer has a straightforward gain design, and it further reduces current estimation errors and improves the robustness against machine parameter variation and system uncertainty. The proposed SCS control approach is validated with extensive experimental tests on a laboratory interior PMSM under both steady-state and transient conditions.