Dynamic Stability Enhancement in a Multimachine Power System using SVC along with a Controller

Author Name(s): Thumma Saritha Kumari
Author Email: tmsaritha@gmail.com

Abstract

This paper presents a mathematical analysis namely linearization technique for small signal stability enhancement in multi machine power system using a FACTS device SVC. Using eigen values and participation matrix the small signal dynamic behavior of the multimachine power system is investigated. Secondly with a FACTS device SVC the same system enhanced dynamic behavior using eigen values and participation matrix is also studied. Finally, with SVC along with a controller the same system effective dynamic stability using linearization technique is seen. Local stabilizing signals such as bus voltage deviations and bus angle perturbations are used as control inputs for the damping controller in FACTS device. Proposed technique is implemented on the standard WSCC 3 Machine 9 Bus system. The system is simulated in PSAT software and the computations are carried out using MATLAB.

Introduction

Considering today’s scenario, power demand is increasing and necessary too. Stability is an important factor in the area of power system, power system oscillates accordingly electromechanical oscillations. Because of these there will be more oscillations towards the generating units as well as transmission unit too, which ultimately makes the entire system inadequate and weak as the load increased. To a single generator or a generator plant these oscillations may be local (local oscillations, 0.8 – 2 Hz), or widely separated geographically different groups of generators these are interarea (interarea oscillations, 0.2 – 0.8 Hz). These electromechanical oscillations lead to power interruption [1]. The approach to solve the problem, FACTS is introduced [2]. The main objectives of FACTS, to increase transmission capacity and control of power flow. Although PSS’S provide supplementary feedback stabilizing signals, but still variations in voltage profile and they may result in leading power factor operation under severe disturbances.

Because of above factor, power system must be retuned accordingly with operating state. Since power system is highly non-linear, the controllers and converters operating condition cannot cope with changes in operating conditions for security loads, power flow control and voltage control in transmission system [3]. Now controllers provided with stabilizing loops are found to be effective for damping out power system oscillations. Static Var Compensator (SVC) control strategies for enhancing the dynamic and transient stabilities in a simple two machine system was discussed in[4]. The modeling and interfacing techniques of SVC and TCSC for a long term dynamic simulation in[5]. Optimal tuning of FACTS based stabilizers for Dynamic Stability enhancement in Multimachine power systems was analyzed in [6]. From the above review of references, the present paper using a mathematical analysis namely linearization technique. Linearizing the system performance equations and using them in standard form of state space model, the small signal dynamic behavior enhancement of a multi machine power system with FACTS device SVC simulations along with computations is further discussed.

Conclusion

This paper has presented using linearization technique the small signal dynamic behavior enhancement of a multi machine power system with FACTS device SVC controller. The improved dynamic stability using FACTS device controller when compared to without controller have proved. The proposed mathematical technique can used directly for small signal stability investigations which would make programming task simpler. It should be noted that this paper makes use of local feedbacks as stabilizing signals for the FACTS based damping controller SVC. The results are shown both with simulation and computation. This work can be implemented or can be further implemented with different other techniques which resolve issues more prominently by avoiding complicity by avoiding programming task.

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