A high efficiency static VAr compensation scheme using modified magnetic energy recovery switch (MERS) with parameters selection of passive elements for low harmonic injection

Abstract

In this paper, a minimum switch count modified magnetic energy recovery switch (MERS) topology has been proposed as a shunt static VAr compensator (SVC-MERS). Whereas, the existing scheme uses four active switches for the same purpose. Thus, conduction loss of the switch is reduced in the proposed scheme due to the minimum switch count and thus promises a high-efficiency compensator. Moreover, a coupling inductor (L) and a capacitor (C) are used in the proposed scheme for reactive energy storing and exchanging. Improper selection of L and C may instigate harmonic resonance. To examine its impact on modified MERS performance, an equivalent harmonic model using mathematical equations has been developed by introducing switching functions. The characteristics analysis of the proposed modified MERS has been done by using this harmonic model. Based on the above analysis a suitable ratio (S) of resonant angular frequency to line angular frequency and corresponding optimum L, C parameters have been selected for low harmonic injection. The key features of this proposed scheme are low current total harmonic distortion (THD), lesser switching losses, reduced cost, and low voltage rating of the switch as compared to the existing MERS scheme. To verify the proposed concept simulation has been carried out using a 6 kVA rating inductive load in MATLAB Simulink environment. The both analytical and simulation results confirm that the proposed reduced switch count compensator model with optimum L=30mH and C=150μF can be used efficiently for power quality improvement in a low voltage grid. \\