2012 Second International Conference on Advanced Computing & Communication Technologies
Simulation of D-STATCOM for Voltage Fluctuation Rupal Singh
Dushyant Kumar Singh
[email protected]
[email protected]
Vadodara Institute of Engineering Vadodara (Gujrat)
IET Alwar, Alwar (Rajasthan)
the power system transmission lines load ability, all these devices were controlled and switched mechanically and therefore, relatively slow. The best equipment to solve this problem at distribution systems at minimum cost is by using Custom Power family of D-STATCOM [1].
Abstract This paper deals with control strategies for DSTATCOM (Distribution Static Compensator) for power quality improvement for a three-phase, three-wire distribution system. A three-leg voltage source inverter (VSI) configuration with a dc bus capacitor is employed as DSTATCOM. The PWM current controllers are designed analyzed and compare for PI controller. The capability of the DSTATCOM is demonstrated through results obtained using PSIM. The performance of the DSTATCOM acting as a shunt compensator is found satisfactory under varied load perturbations.
2 Basic Configurations and Operation of D- STATCOM D-STATCOM is a three-phase and shunt connected power electronics based device. It is connected near the load at the distribution systems. The major components of a DSTATCOM are shown in Fig. 1. It consists of a dc capacitor, three-phase inverter, ac filter, coupling transformer and a control strategy. The basic electronics block of the D STATCOM is the voltage-sourced inverter that converts an input dc voltage into a threephase output voltage at fundamental frequency [2].
Keywords- FACTS, Static Synchronous Compensator (STATCOM), VSC, Voltage dip, Shunt Compensation
1 Introduction Power system is a complex network & it’s made of thousands of buses and hundreds of generators. Available power generation does not situated near a growing of load center, to meet the demand, utilities have an interest in better utilization of available power system capacities, existing generation and existing power transmission network, instead of building new transmission lines and expanding substations. On the other hand, power flows in some of the transmission lines are overloaded, which has as an overall effect of deteriorating voltage profiles and decreasing system stability and security. Series capacitor, shunt capacitor, and phase shifter are different approaches to increase 978-0-7695-4640-7/12 $26.00 © 2012 IEEE DOI 10.1109/ACCT.2012.105
Fig. 1 STATCOM based on voltage-sourced converter.
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2.1 Voltage Source Converters (VSC)
3.1
Three-phase VSC is the core component of the STATCOM, which generate a sinusoidal voltage with any required magnitude, frequency and phase angle.
If the amplitudes of the STATCOM output voltage and the ac system voltage are equal, the reactive current is zero and the STATCOM does not generate or absorb reactive power.
A basic schematic diagram of VSC is shown in Fig.2. It is a six-pulse forceed-commutated converter, which contains six power semiconductor switching devices with antiparallel connected diode together with heat sinks and auxiliary components for trigger, monitoring and grading.
No load mode (Ui=Us)
Fig.4 No Load mode
3.2 Capacitive mode (Ui>Us) When the converter voltage is greater than the system voltage, the system sees the STATCOM as a capacitive reactance and the STATCOM is operating in a capacitive mode. The current fl f ows from the STATCOM to the ac system, and the device generates reactive power. In this case, the system draws capacitive current that leads by and angle of 90 degree the system voltage.
Fig.2 Scheme of three-phase VSC
3 Operating Principle of STATCOM Fig.3 shows the active and reactive power transfer between a power system and a VSC. If the magnitude of supply voltage Us is less than the magnitude of inverter voltage Ui, reactive power Q is flowing from power system to VSC. If Us is greater than Ui, Q is flowing from VSC to power system [3].
Fig.5 Capacitive mode
3.3 Inductive mode (Ui
