Enhanced Automatic-Power-Decoupling Control Method for Single-Phase AC-to-DC Converters

Abstract

Existing control schemes for single-phase ac-to-dc converters with active power-decoupling function typically involve a dedicated power-decoupling controller. However, due to the highly coupled and nonlinear nature of the single-phase system, the design of the power-decoupling controller (typically based on the linear control techniques) is cumbersome, and the control structure is complicated. Additionally, with the exiting power-decoupling control, it is hard to achieve satisfied dynamic responses and robust circuit operation which are required for a reliable system operation. Following a recently proposed automatic-power- decoupling control scheme, this paper proposes a nonlinear control method that can achieve enhanced dynamic responses with strong disturbance rejection capability without the need for a dedicated power-decoupling controller. The proposed controller has a simple structure, of which the design is straightforward. The control method can be easily extended to other single-phase ac-to-dc systems with active power-decoupling function.

Existing System

Power Decoupling Techniques.

Proposed System

In this paper, an enhanced automatic-power-decoupling control is proposed. The proposed controller is easy to apply with simple design methodology. More importantly, the proposed control method substantially improves the dynamic responses of the overall system, rendering strong disturbance-rejection performance. This paper firstly presents a systematic overview of the existing control methods for a single-phase ac-to-dc power converter with active power decoupling function. It is shown that the recently proposed APD control possesses a simpler control structure and improved robustness of the closed-loop system toward disturbance as compared to that with the conventional DPD control. However, it is found that both APD and DPD control suffers from high control/computational complexity and that they give poor dynamic control performances and robustness against load and input variations. An enhanced APD (E-APD) control is then proposed in this paper and applied to a recently proposed two-switch buck-boost PFC rectifier for illustration. The central idea of the approach is to algebraically transform the nonlinear and coupled single-phase system dynamics into a fully linear one, so that classical linear control analysis and design techniques can be applied. The method differs completely from conventional control analysis and design methods used in DPD and APD that are based on standard small-signal linear approximation where the state intercoupling is often neglected.

Architecture

A generic three-port model for a single-phase system with active power-decoupling function