technical and performance aspects of a dynamic …paginas.fe.up.pt/~ee04109/documentos e...

Technical and Performance Aspects of a Dynamic Voltage Restorer

Author:

Keywords: Voltage sags mitigation, DVR, IGCT, Real-time simulator, Computer simulation

K. Chan, ABB High Voltage Technologies Ltd., System Engineering Division, Switzerland

Abstract

One of the major issues in improving power quality in distribution networks is the mitigation of voltage sags. Voltage sags in distribution networks caused by system faults can adversely affect sensitive electrical equipment in industrial production processes, such as in semiconductor fabrication, resulting in substantial financial losses. A safe, reliable and clean power supply to these industries is therefore a prerequisite to their profitable operation.

A Dynamic Voltage Restorer (DVR), with its excellent dynamic capabilities, when installed between the supply and a critical load feeder, can compensate for voltage sags, restoring line voltage to its nominal value within a few milliseconds and hence avoiding any power disruption to that load.

This paper presents the technical aspects of designing an Integrated Gate Commutated Thyristor (IGCT) based DVR shown in Figure 1 , a new device capable of meeting the stringent requirements of voltage sags mitigation. Furthermore, performance assessments of the DVR using a real-time hardware simulator model and computer simulations are discussed.

The first section of the paper provides a functional description of the DVR. In order to provide for the capabilities demanded by voltage sag mitigation, the DVR requires functions such as rapid control response, an energy source and a mechanism for coupling the boosting voltages compensating the sag. The major components, their related functions and operating characteristics are presented.

Customer’s requirements dictate the design and performance of the DVR. This section details the considerations that must be taken into account for the design of the DVR in order to fulfil the required specifications. Design considerations that influence the rating and performance of the DVR such as protected load MVA and power factor, magnitudes of single and three phase voltage sags and fault duration, three phase fault level at the incoming bus, etc. are discussed. To ensure that the designed DVR is capable of meeting the specified requirements, its dynamic performance and the control system functions must be verified. Verification procedures using a real-time analogue simulator and computer simulations are discussed. The control system functions are described and results from the verification procedures are then presented.

Newly developed Integrated Gate Commutated Thyristors have been selected for the converter used in DVR installations. The IGCT merges the attractive features of Gate Turn- Off (GTO) thyristors with the strengths of Insulated Bipolar Gate Transistors (IGBT) for converters with a wide power range and providing the DVR with high converter reliability, high converter efficiency at steady state operation and inherent safety even under worst case conditions.

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