Mitigation of Power Quality Problems Using Custom Power Devices: A Review

Electrical power quality (EPQ) in distribution systems is a critical issue for commercial, industrial and residential applications. The new concept of advanced power electronic based Custom Power Devices (CPDs) mainly distributed static synchronous compensator (D-STATCOM), dynamic voltage restorer (DVR) and unified power quality conditioner (UPQC) have been developed due to lacking the performance of traditional compensating devices to minimize power quality disturbances. This paper presents a comprehensive review on D-STATCOM, DVR and UPQC to solve the electrical power quality problems of the distribution networks. This is intended to present a broad overview of the various possible DSTATCOM, DVR and UPQC configurations for single-phase (two wire) and three-phase (three-wire and four-wire) networks and control strategies for the compensation of various power quality disturbances. Apart from this, comprehensive explanation, comparison, and discussion on D-STATCOM, DVR, and UPQC are presented. This paper is aimed to explore a broad prospective on the status of D-STATCOMs, DVRs, and UPQCs to researchers, engineers and the community dealing with the power quality enhancement. A classified list of some latest research publications on the topic is also appended for a quick reference

Performance Evaluation of Three Different Inverter Configurations of DVR for Mitigation of Voltage Events

The voltage events namely voltage sags and voltage swells represent the most common, frequent and important power quality events in today’s power system. Dynamic voltage restorer (DVR) is one of the key components used to mitigate the supply voltage quality disturbances in terms of voltage sags and swells in the distribution system. It consists of an energy storage unit, a voltage source inverter, a filter, a coupling transformer and the control system. This paper presents three different inverter configurations of dynamic voltage restorer (DVR) for mitigation of voltage events such as voltage sags and swells with sudden addition or removal of the nonlinear load. These three configurations are voltage source inverter based DVR (VSI-DVR), current source inverter based DVR (CSI-DVR) and impedance or Z-source inverter based DVR (ZSI-DVR). The d-q control technique is used to control the operation of the DVR. The response of ZSI-DVR for mitigation of voltage sags and swells are investigated and compared with VSI-DVR and CSI-DVR using MATLAB/SIMULINK environment

Comparison of DSTATCOM Performance for Voltage Sag Alleviation

This paper describes the comparative analysis of three different control techniques of distributed flexible AC transmission system (DFACTS) controller called as distributed static synchronous compensator (DSTATCOM), aimed at power quality (PQ) enhancement in terms of voltage sag mitigation in a three-phase four-wire (3p4w) distribution system. A DSTATCOM is one of the major power quality improvement devices which consist of a DC energy source, a voltage source inverter (VSI), a filter, a coupling transformer and the control system. The control strategy based on synchronous reference frame (SRF) theory, instantaneous active and reactive current (IARC) theory and propositional-integral (PI) controller has been used for reference current generation of voltage source inverter (VSI) based DSTATCOM. The SRF, IARC and PI control based DSTATCOM is validated through dynamic simulation in a MATLAB\SIMULINK environment under linear as well as nonlinear loads

DNA methyltransferase Dnmt1 associates with histone deacetylase activity.

The DNA methyltransferase Dnmt1 is responsible for cytosine methylation in mammals and has a role in gene silencing. DNA methylation represses genes partly by recruitment of the methyl-CpG-binding protein MeCP2, which in turn recruits a histone deacetylase activity. Here we show that Dnmt1 is itself associated with histone deacetylase activity in vivo. Consistent with this association, we find that one of the known histone deacetylases, HDAC1, has the ability to bind Dnmt1 and can purify methyltransferase activity from nuclear extracts. We have identified a transcriptional repression domain in Dnmt1 that functions, at least partly, by recruiting histone deacetylase activity and shows homology to the repressor domain of the trithorax-related protein HRX (also known as MLL and ALL-1). Our data show a more direct connection between DNA methylation and histone deacetylation than was previously considered. We suggest that the process of DNA methylation, mediated by Dnmt1, may depend on or generate an altered chromatin state via histone deacetylase activity.Journal ArticleResearch Support, Non-U.S. Gov'tinfo:eu-repo/semantics/publishe