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

Abstract

This paper proposes an observer-based volts-perhertz (V/Hz) control method for synchronous motors. The method is applicable to any synchronous motor type, from permanentmagnet (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.

Design Framework for Sensorless Control of Synchronous Machine Drives

“…With positive design parameters α τ and α f , the mechanical impedance is passive in the feasible operating region where τ δ0 > 0. Consequently, the V/Hz control configuration is locally stable for any passive mechanics, as expected based on [22]. 4) Numerical Analysis of the Closed-Loop System: The closed-loop torque control is illustrated with a frequency response graph.…”

“…It can be shown that passivity condition for (22) with positive design parameters α τ , k p , and k i is…”

“…However, analytical stability results and general design rules for a wide range of machines are not available for the compensation-loop based methods. In contrast, observer-based V/Hz control uses a passivity-based design, incorporating a sensorless flux observer and a state-feedback law to achieve stability in the whole feasible operating region [22].…”

Observer-Based Power-Synchronization Control for Grid-Forming Converters

“…It can be seen to have the same inputs as the other PSC-based methods, despite the internal structure being different. It is based on a previously developed observer-based V/Hz control method and purposefully resembles it closely [6]. This is why terms such as virtual flux linkage and virtual torque are used even though they are not commonly used in the context of grid-connected converters, as explained in Chapter 2.4.…”

“…This control method is named observer-based power-synchronization control (OPSC). OPSC is inspired by a previously developed observer-based V/Hz control method for synchronous machines [6]. The validity and performance of OPSC is assessed by means of linear analysis and simulations where OPSC will be compared to two other state-of-the-art PSC-based methods.…”