This paper presents a comprehensive review on the unified power quality conditioner (UPQC) to enhance the electric power quality at distribution levels. This is intended to present a broad overview on the different possible UPQC system configurations for single-phase (two-wire) and three-phase (three-wire and four-wire) networks, different compensation approaches, and recent developments in the field. It is noticed that several researchers have used different names for the UPQC based on the unique function, task, application, or topology under consideration. Therefore, an acronymic list is developed and presented to highlight the distinguishing feature offered by a particular UPQC. In all 12 acronyms are listed, namely, UPQC-D, UPQC-DG, UPQC-I, UPQC-L, UPQC-MC, UPQC-MD, UPQC-ML, UPQC-P, UPQC-Q, UPQC-R, UPQC-S, and UPQC-VA. More than 150 papers on the topic are rigorously studied and meticulously classified to form these acronyms and are discussed in the paper.

Enhancing Electric Power Quality Using UPQC: A Comprehensive Overview

This paper introduces a new concept of optimal utilization of a unified power quality conditioner (UPQC). The series inverter of UPQC is controlled to perform simultaneous 1) voltage sag/swell compensation and 2) load reactive power sharing with the shunt inverter. The active power control approach is used to compensate voltage sag/swell and is integrated with theory of power angle control (PAC) of UPQC to coordinate the load reactive power between the two inverters. Since the series inverter simultaneously delivers active and reactive powers, this concept is named as UPQC-S (S for complex power). A detailed mathematical analysis, to extend the PAC approach for UPQC-S, is presented in this paper. MATLAB/SIMULINK-based simulation results are discussed to support the developed concept. Finally, the proposed concept is validated with a digital signal processor-based experimental study.

UPQC-S: A Novel Concept of Simultaneous Voltage Sag/Swell and Load Reactive Power Compensations Utilizing Series Inverter of UPQC

This paper proposes a novel reference signal generation method for the unified power quality conditioner (UPQC) adopted to compensate current and voltage-quality problems of sensitive loads. The UPQC consists of a shunt and series converter having a common dc link. The shunt converter eliminates current harmonics originating from the nonlinear load side and the series converter mitigates voltage sag/swell originating from the supply side. The developed controllers for shunt and series converters are based on an enhanced phase-locked loop and nonlinear adaptive filter. The dc link control strategy is based on the fuzzy-logic controller. A fast sag/swell detection method is also presented. The efficacy of the proposed system is tested through simulation studies using the Power System Computer Aided Design/Electromagnetic Transients dc analysis program. The proposed UPQC achieves superior capability of mitigating the effects of voltage sag/swell and suppressing the load current harmonics under distorted supply conditions.

A Novel Reference Signal Generation Method for Power-Quality Improvement of Unified Power-Quality Conditioner

Recently utilities are continuously seeking cost-effective and accurate power quality (PQ) improvement techniques in order to achieve customer satisfaction. This paper intends to provide a comprehensive review on the status of topological aspects of techniques used to improve the power quality in distribution network for the researchers, designers and engineers working in this area. This review helps to select a PQ improvement technique that suits a specific application in terms of technical and economical aspects. More than 300 research publications on the state of the art of PQ improvement techniques have been rigorously analyzed, classified and listed for quick reference.

Topological aspects of power quality improvement techniques: A comprehensive overview

With the deregulation of the electric power energy market, providing quality power has become an important concern of both power suppliers and customers. Efforts have been made to improve the power quality using passive filters, active power filters, hybrid filters and the new concept of custom power. This paper presents a comprehensive review of compensating custom power devices mainly DSTATCOM (distribution static compensator), DVR (dynamic voltage restorer) and UPQC (unified power quality compensator). It is aimed at providing a broad perspective on the status of compensating devices in electric power distribution system to researchers and application engineers dealing with power quality problems. Classified references presented in this paper would serve quick and useful applications.

A Review of Compensating Type Custom Power Devices for Power Quality Improvement

The paper deals with an optimized unified power-quality conditioner (UPQC), which aims at the integration of series active and shunt active power filters with minimum volt-ampere (VA) loading of the UPQC. The series active filter is a dynamic voltage restorer (DVR), which regulates the voltage at the load end with minimum VA loading of the overall UPQC by injecting the voltage at an optimum angle. The proposed scheme is validated by an experimental prototype in the laboratory. Selected experimental results are reported along with analytical findings, which show the effectiveness of the proposed UPQC

Experimental Investigation of a Single-Phase UPQC With Minimum VA Loading

The paper deals with an optimized unified power quality conditioner (UPQC), which aims at the integration of series active and shunt active power filters with minimum VA loading of the UPQC. The series active filter is a dynamic voltage restorer (DVR), which is operated in twofold functioning mode. During the unbalanced voltage sag, the DVR compensates the unbalance in the voltage sag. It also regulates the voltage at the load end with minimum VA loading of the overall UPQC by voltage injection at optimum angle. Sliding mode controller with constant frequency is employed to ensure the exact tracking of the reference voltage by DVR. Validity of the proposed scheme is proved through extensive simulation results.

A sliding mode controller based optimum UPQC with minimum VA loading

Voltage sags and swells are vital power quality problems and the dynamic voltage restorer (DVR) is known as an effective device to mitigate voltage sags and swells. The paper deals with the sliding mode control of single phase DVR for voltage sag/swell correction. A sliding mode controller is designed and developed for a single phase DVR. Using sliding mode control to the DVR, additional sag/swell detection method is eliminated. This improves the dynamic response of the DVR and also DVR is able to compensate for any variation in source voltage. Usage of sliding mode control to DVR, makes it multifunctional, such as compensation for voltage sag, swell, voltage flicker and voltage harmonics as well. Validity of the proposed control is verified through extensive simulation and experimental results.

Experimental investigation of DVR with sliding mode control

The paper deals with the sliding mode control of inverter and its applications to custom power devices. Sliding mode control is used to control the voltage source inverter in voltage and current control mode. The sliding mode control strategies provide robustness to custom power device modeling with external disturbances. The proposed controller design is tested on a single phase dynamic voltage restorer (DVR) and a distribution static compensator (DSTATCOM). Use of sliding mode control with DVR enhances the dynamic response for compensation of voltage sag, swell, voltage flicker and voltage harmonics. A laboratory prototype is built and the control is implemented using dSPACE based DSP platform. Validity of the proposed control is verified through experimental results.

Experimental investigation of sliding mode control of inverter for custom power applications

The paper deals with an optimized Unified Power Quality Conditioner (UPQC), which aims at the integration of series active and shunt active power filters with minimum VA loading of the UPQC. The series active filter is a Dynamic Voltage Restorer (DVR), which is operated in twofold functioning mode. During the unbalanced voltage sag, the DVR compensates the unbalance in the voltage sag. It also regulates the voltage at the load end with minimum VA loading of the overall UPQC by optimum angle voltage injection. Validity of the proposed scheme is proved through extensive simulation results.

Y.Y. Kolhatkar

Papers

Experimental Investigation of a Single-Phase UPQC With Minimum VA Loading

A sliding mode controller based optimum UPQC with minimum VA loading

Experimental investigation of DVR with sliding mode control

Experimental investigation of sliding mode control of inverter for custom power applications

An Optimum UPQC with Minimum VA Requirement and Mitigation of Unbalanced Voltage Sag