Integrated Approach to Design and Implementation of a Single-Phase Current Regulator With Antiwindup Mechanism

An ac-regulated single-phase inverter operating in the stationary frame is designed to accurately track a sinusoidal reference signal at a designated frequency. To achieve such a control objective, resonant controllers with a conjugate set of marginally stable poles are required. The explicit implementation of marginally stable dynamics is prone to wind up in the event of the control signal entering a nonlinear saturation condition, resulting in a degraded or even an unstable dynamic response. This article proposes an integrated approach to the design and implementation of a resonant controller for a single-phase current regulator with an intrinsic antiwindup mechanism. The proposed method utilizes a disturbance observer to embed a pair of complex poles into the controller, leading to accurate tracking of a sinusoidal reference signal. Simultaneously, by using the observer architecture with a set of desired closed-loop poles as the performance specification, the implementation form remains completely stable. Furthermore, the closed-loop performance of the proposed resonant control system is analyzed to assess the impact of unmodeled dynamics. Experimental results are presented to demonstrate the efficacy of the proposed approach.

I. Introduction

High-performance current regulation is an essential element of ac power conversion systems. Widespread applications for such devices include machine drives, grid-connected power conversion systems, and power conditioners [1], [2]. Precise control of the commanded current is fundamental to achieving high-performance outputs. By way of example, consider the increasingly subscribed grid-connected distributed generation power conversion system [3], [4]. Distributed power generation sources are covered by grid codes and must inject with minimal deviation from unity power factor [3]–[5]; hence, accurate regulation strategies are vital. In general, current regulators designed in the stationary reference frame must have high gains at the operating reference frequency or for rotating frame synchronous dq schemes, at dc (0 Hz), in order to achieve desired levels of reference tracking performance. Moreover, to ensure a rapid transient response, bandwidth maximization is desirable, for a given stability margin [6], [7].