A Single Phase AC/DC/AC Converter with Unified Ripple Power Decoupling

Abstract

In single phase AC/DC/AC converters, the low frequency ripple powers exist both at the source and load sides. Usually, large DC-link filter components are used to buffer the ripple powers, which increases volume and weight. To overcome the drawback, this paper presents a single phase AC/DC/AC current source converter with unified ripple power decoupling. The converter only consists of three bridge arms and a decoupling circuit. The three bridge arms play the role of rectification and inversion with sharing a bridge arm. And the decoupling circuit is in series with the DC-link energy storage unit to buffer the ripple powers. The circuit configuration and operation principles are introduced firstly. Then, a modulation strategy based on Cartesian space is developed to achieve sinusoidal input and output currents. The control idea that the DC-link current is regulated by the decoupling circuit and the averaged decoupling capacitor voltage is maintained by the rectifier is adopted. The ripple power buffer is automatically achieved.

Existing System

Three-Leg-Type Converter.

Proposed System

This paper firstly introduces the proposed circuit structure and its operation principles. Then the power difference between the source and load are analyzed under different operation conditions. It reveals that the decoupling capacitor voltage can be much different under various operation conditions, which brings a challenge for controller design. In this paper the decoupling circuit is taken as a controlled voltage source to keep the voltage-second balance of the DC-link inductor. Then, the DC-link current can be smooth and the ripple power buffer is automatically achieved. Finally, the simulations and experimental tests were conducted to verify the effectiveness of the proposed converter and control method.

Architecture

Proposed single-phase AC/DC/AC CSC