An Improved Cascaded-SVG Reactive Current Detecting Method

Abstract

Static Var Generator (SVG) is a new generational dynamic reactive power compensation system and the detection of directive current generally uses ip-iq operation mode. However, the command value of output reactive current only depended on the reactive current detection of main circuit based on the ip-iq operation mode in the traditional SVG device. This method limits the realtime compensation and the accuracy of reactive power compensation is not guaranteed based on single detecting point. For solving this problem, an improved method for detecting the reactive current based on instantaneous power balance is proposed in this paper. The current information of detecting point and compensating point are introduced and the compensatory accuracy is improved. The improved method is applied in the Cascaded-SVG and the simulation results with matlab/Simulink verify the correctness and effectiveness of the proposed method. Introduction With the rapid development of power electronic technology, power electronic sets have been widely used, which affect the electric energy quality, the stability, safety and economy of the electric system [1]. Static Var Generator (SVG) is reactive compensatory device which is applied extremely widespread today [2]. Presently, the main approach called ip-iq operation mode is a kind of calculating approach based on the instantaneous reactive power principle [4-6]. Due to this approach is beneficial to the detection for reactive current, it also has well real-time. However, it can produce the direct current component, which affects the process of the reactive compensation[7]. Also, only to detect the information of reactive current before compensating reactive current and neglecting the existence of reactive power will make the Cascaded-SVG to lag a compensative season. Face to the problem, we present a method to detect the reactive power. The main process is detecting the output current and the current of main circuit by ip-iq method to obtain more precise reactive current command. The command drives the Cascaded-SVG inverter. Therefore, this process gives the Cascaded-SVG current a feedback control, which not only reduces the errors, but also improves the real-time compensation. Moreover, this approach is tested by Matlab/Simulink, the experimental results prove that it not only increases the accuracy of reactive compensation of Cascaded-SVG device, but also improves the real-time compensation. The Traditional Approach for Detecting Reactive Current of Cascaded-SVG The Basic Theory of Cascaded-SVG The basic theory of Cascaded-SVG through parallel connecting the circuits which composed by series connecting several H-bridges in the grid by electric reactor, due to the cascaded-SVG purposed to make dynamically reactive compensation come true. We can appropriately adjust the output voltage value and phase of bridge circuit alternating current, or directly control its alternating current which makes the circuit to absorb and to produce enough reactive current to reach our destination[8]. 2nd International Conference on Electrical and Electronic Engineering (EEE 2019) Copyright © 2019, the Authors. Published by Atlantis Press. This is an open access article under the CC BY-NC license (http://creativecommons.org/licenses/by-nc/4.0/). Advances in Engineering Research, volume 185