Stable and Passive Observer-Based V/Hz Control for Synchronous Motors

This paper proposes an observer-based volts-per-hertz (V/Hz) control method for synchronous motors. The method is applicable to any synchronous motor type, from permanent-magnet (PM) motors to synchronous reluctance motors (SyRMs). The method consists of a state-feedback control law and a state observer, both of which are designed to be inherently sensorless. The gains can be selected using simple closed-form expressions, resulting in a locally stable and passive system in the whole feasible operating range. Unstable regions and heuristic tuning of conventional V/Hz control are thus avoided. Compared to sensorless field-oriented control, neither speed controller nor separate field-weakening method is needed, the full inverter voltage can be utilized, and the sensitivity to parameter errors is reduced. For the majority of industrial drive applications, the dynamic performance of the proposed method is adequate.