Dtcm Case

ANALYSIS OF DSTATCOM FOR VOLTAGE SAG AND UNDER VOLTAGE

1A.Sherly,2 P.Arul, 3G.Susithra

1PG Scholar Department of Electrical and Electronics Engineering, Trichy-621 014

2 Associate professor Department of Electrical and Electronics Engineering, Trichy-621 014

3 Assistant professor Department of Electrical and Electronics Engineering, Trichy-621 014 E-mail : [e-mail]

Abstract— The power systems are designed to operate effectively and efficiently. Now a day the present loads are mostly based on power electronic devices. These loads are very sensitive to power quality problem such as voltage sag. Hence these devices are needed to be protected by suitable compensating devices. DSTATCOM is one such a compensating device which is based on voltage source converter. It is one of the Flexible AC Transmission System and it is controlled using the PI controller. This paper proposes the analysis of voltage sag and under voltage. By selecting the proper gain value of the PI

This is achieved by varying the PI controller gain. The second case is based on the load compensation, this is achieved due to, i) the dc source as constant and controller gain are variable. ii) the dc source value are variable and controller gain as constant.

II. Basic Principle of DSTATCOM

The figure 1 shows the basic structure of DSTATCOM. It consists of voltage source converter, dc energy storage and a coupling transformer which is connected in shunt to the distribution network. The voltage source converter is a power electronic device which is used to convert direct current to alternating current. The DSTATCOM is used to generate or absorb the reactive power. There are three modes of operation in DSTATCOM [4, 11]. They are,

a) No load mode (Vsa = Vi)

b) Capacitive mode (Vi > Vsa)

c) Inductive mode (Vi <