A novel unified single-phase active rectifier topology with advanced operating modes for smart grids

Abstract

Active rectifiers are of paramount importance for guaranteeing power quality in smart grids, due to their characteristics of sinusoidal current consumption and unitary power factor operation. In this paper, a novel unified single-phase (USP) front-end converter is proposed for active rectifier applications in smart grids, offering additional advantages and a set of relevant features besides the conventional active rectification. With the proposed USP front-end converter, the following independent operation modes are available: (i) operation as a traditional active rectifier, ensuring sinusoidal AC grid current (with very low total harmonic distortion), unitary power factor, and controlled DC link voltage; (ii) operation as a shunt active power filter, producing a current with controlled harmonic content and phase angle at the fundamental frequency, in order to ensure almost sinusoidal current and a unitary power factor at the AC power grid; (iii) combined operation as an active rectifier and as a shunt active power filter, providing power to the DC load, while simultaneously producing a current waveform with reduced harmonic content and controlled power factor. By controlling these individual operation modes, electrical appliances in smart grids can operate dynamically and collaboratively, improving power quality. In addition, the proposed USP front end converter may operate as a single-phase diode rectifier in case of control system failure or damage of the controlled switching devices. This situation is particularly relevant since it allows to supply the DC load even under such unfortunate circumstances. Along with the paper, the topology of the proposed USP front end converter, its principle of operation, and the control strategies for each operation mode, are separately explained. A 3.6 kW, 230 V – 50 Hz laboratorial prototype of the proposed USP front end converter is presented, and the experimental validation is carried out for all operation modes.