A New Quasi Z-Source Dynamic Voltage Restorer

Abstract

Abstract –This paper deals with a new quasi Z-source Dynamic Voltage Restorer(DVR). The proposed system based on single-phase quasi Z-source AC-AC converter which has features such as the input voltage and output voltage are sharing ground, and the input current operates in continuous current mode. Also the proposed system is able to compensate voltages sags and swells. For the detection of voltage sag-swell, the fast detection of an instantaneous value detection algorithm is applied. The operating principles of the proposed quasi Z-source AC-AC converter are described and PSIM simulation is presented to verify the proposed concept and theoretical analysis. Keywords : Quasi Z-Source AC-AC Converter, Dynamic Voltage Restorer, Voltage Sag-Swell Compensator 1. Introduction Some decades, the power quality did not cause any problems, because it had no effect on most of the loads connected to the electric distribution system. In recent years, power quality issues have been received much attention. With the increased use of the sophisticated electronics, high efficiency variable speed drive, and power electronics controller, power quality has become an increasing concern to utilities and customers and huge economical losses due to the interruption of production processes[1]. Among these problems, voltages sag and swell are the most common type of power quality disturbance in the distribution system. In order to increase the reliability of a power distribution system, many methods of solving quality problems, especially voltage sag, have been suggested. Many voltage sag mitigation schemes are based on inverter systems consisting of energy storage and power switches. Also, the Dynamic Voltage Restorer (DVR) and Uninterrupted Power Supply (UPS) developed and they are able to compensate voltage sags and swells, harmonics maintaining a regulated voltage at critical load[2]. But some of them are based on energy storage devices such as large capacitors or batteries bank. If the power is increased, the size of these devices will increase and make them more expensive[3]. In this paper, we propose a new quasi Z-source dynamic voltage restorer. The proposed topology employs a single-phase quasi Z-source AC-AC Converter[4] along with an autotransformer. During the voltage sags or swells, the proposed system regulates the adding or missing voltage and maintaining the rated voltage at the terminals of the critical load. The proposed system is able to compensate up to over 50% voltage sag and it is able to compensate voltage swell. In addition, it is possible to use an AC-AC converter instead of a power inverter in the topology of a dynamic voltage restorer avoiding the energy storage devices[2]. This paper also proposes the control method of the fast detection of an instantaneous value detection algorithm. The operating principle, analysis, simulation results are presented.