A GSA-Based Modified SVC Switching Scheme for Load Balancing and Source Power Factor Improvement

An improved switching scheme for static VAr compensators (SVCs) that have fixed capacitor-thyristor-controlled reactors (FC-TCRs) for load balancing and power factor improvement has been addressed in this paper. The proposed control scheme can eliminate negative-sequence current caused by unbalanced load while improving the source power factor simultaneously. Thus total current supplied by the source can be minimized along with improvement of the load voltage profile. As the switching of TCR can introduce additional harmonics in the line, an optimized switching function is adopted in the proposed scheme for minimum injected harmonics without using an external filter. The gravitational search algorithm has been used for obtaining the optimized switching angle. The proposed scheme has been verified through proper simulations backed by suitable experimental results on a practical system.

I. Introduction

The power distribution networks are facing various problems due to increased application of nonlinear loads. In addition to poor voltage profile, power factor correction, unbalance load compensation, and harmonic injection [1] have become major issues for the utility system. The unbalance voltage at the utility terminal [2] will increase system losses and can also be harmful on industrial machines and generators. The voltage source inverter (VSI) based compensators [3]–[5] have been used to solve the problem of load compensation and power factor correction in power distribution system. However, thyristor-controlled SVCs are also commonly used for the same purpose in modern supply system. Since, the traditional methods of load compensation using SVC [6] cannot dynamically and effectively balance the system load. Therefore SVC based suitable compensators [7], [8] for negative-sequence component of load current to transfer the unbalance system to a balance system have been studied. The different passive and active harmonic filters [9]–[12] topology combined with SVCs are also widely used for load compensation, power factor correction and harmonic minimization at the cost of additional investment, larger space requirement etc.