ABSTRACT
In this, Electrical and electronic devices, when exposed to one or more power quality problems, are prone to failure. This study aims to enhance the quality of power in three-phase pv sourced micro grid using unified power quality conditioner (UPQC). The proposed UPQC has an active filter on the shunt side and dynamic voltage restorer on the series side. A combination of a synchronous reference frame and instantaneous reactive power theories is utilised to generate reference signals of the UPQC. The obtained results proved that the proposed UPQC compensated power quality problems such as voltage sag, harmonics, voltage imbalance in the micro grid system. The comparison is made of various individual compensation devices such as shunt active filters , dvr and upqc. The proposed system is simulated in MATLAB/Simulink software.
INTRODUCTION
Modern society relies heavily on electricity. For instance, people need electricity to run household appliances, office equipment, electronic devices, manufacturing process, etc for daily activities and works. For this reason, electricity has become an important service and the quality of electricity directly impact on the operation of electrical equipment and subsequently affect to quality of life. Therefore, power quality of electric system have got more attention by either network operators or end users in recent decades. Power quality problems can be classified into two main categories: the first is steady-state problems such as voltage and current harmonics, the second is transient problems such as voltage disturbances, voltage sag/swell, and interrupts [1, 2]. In general, voltage and current harmonics are considered as the most severe problems due to the intensive and increasing growth of nonlinear loads such as rectifiers, adjustable speed motor drives, and switching power supplies in today’s networks. Nonlinear loads cause injections of current harmonics into distribution systems and subsequently degrade the quality of the network’s voltage. On the other hand, voltage disturbances such as voltage sags/swells and interrupts caused by grid faults are also considered as costly power quality problems. These disturbances regularly cause malfunctions or interruptions of electronic-based equipment, which cause huge economic losses due to damaged materials and lost production. Due to severe impacts of poor power quality, improvement of power quality for distribution power system has become a mandatory requirement. Power quality can be improved by using power filters and custom power devices. Common custom power devices can be considered as shunt active power filters (APFs) [3–19], dynamic voltage restorers (DVRs) [20–26], and unified power quality conditioners (UPQCs) [27–38]. The Shunt APFs are mainly used to mitigate current harmonics generated by nonlinear load. Meanwhile, the DVR is a series connected compensating device that protects sensitive loads from voltage disturbances such as voltage sag/swell, voltage unbalance, voltage distortion in the supply side. These compensating devices are effective solutions, but most of them can only deal with one or two power quality issues. In recent years, UPQC has been introduced as an advanced and powerful compensating device to simultaneously deal with current and voltage related problems. The UPQC is a combination of a shunt APF and a series APF connected back-to-back via a common DC-link capacitor. A UPQC can effectively compensate the power quality issues such as current and voltage harmonics, voltage sag/swell, and voltage unbalance to protect sensitive loads and improve the power quality of the distribution system. Due to the promising capability of the UPQC in power quality improvement, the utilization the UPQC to improve power quality in distribution level have been significantly increased in last decades and a number of studies on control of UPQC have been carried out. This thesis focuses on developing advanced control strategies to improve the compensation performance of the UPQC so that the UPQC can effectively deal with various power quality problems.

Block Diagram