Investigation on Six Switch and Nine Switch Multi functional Power Converters for Power Quality Improvement in Grid Interactive PV System

Abstract

With the advancement in power electronics technology, sophisticated equipment such as switched-mode power supplies (SMPS), adjustable speed drives (ASDs), etc., has increased tremendously. The main benefit of these systems is that they are energy efficient. However, as they contain switching devices, they draw nonlinear currents, distorting the voltage at the point of common coupling. Moreover, these loads are highly sensitive to fluctuations in voltage at the point of common coupling (PCC). Therefore, custom power devices such as DVR, DSTATCOM, UPQC, etc., are required to protect voltage-sensitive loads and eliminate the effect of nonlinear current. Another major trend in recent years is the increasing focus on using renewable energy systems, particularly solar photovoltaic systems. The basic structure of shunt active filters, grid-connected PV systems, and the shunt side of UPQC are the same. The only difference is that the PV system creates an active energy source at the DC link, whereas the other uses a passive energy storage device. It is possible to replicate the functionality of shunt active filters in grid-connected PV systems and vice-versa. Such systems are termed as multifunctional systems. Hence, the major requirement of modern distribution systems is the deployment of multifunctional devices that integrate both distributed generation and power quality improvement features. Therefore, this research focuses on integrating the solar PV array with UPQC for use in modern singlephase and three-phase distribution systems. Conventionally, UPQC/PV-UPQC systems are formed using a Back-to-back (B2B) converter, with eight and tweleve active switches in a single and three-phase system respectively. This thesis in addition to the B2B converter topology proposes the use of a nine-switch converter (NSC) and a six-switch converter (SSC) converter for UPQC and PV UPQC applications.