Instantaneous Reactive Power Compensation Based on Neutral Line Current Separating and Combining Method.

Abstract

Instantaneous compensation theory of reactive power is conventionally based on coordinate transformation method. That is, three phase voltages and currents on three dimensional coordinate are transformed into αβcoordinate or rotating coordinate quantities. Therefore, it is unavoidable for the control system to be complicated and also it is difficult to understand physical meanings of voltages and currents on the original three dimensional coordinate.The authors have been proposed the instantaneous reactive power compensation theory using a three dimensional cross vector. The proposed theory does not use any coordinate transformations, such as a rotating coordinate transformation or a three-phase to two-phase coordinate transformation. Hence, the instantaneous reactive power compensation system based on the proposed theory is essentially simpler than any conventional reactive power compensation system based on such coordinate transformations.In this paper, we apply the Cross vector theory to three-phase four-wire system. Since there is a neutral line in three-phase four-wire system, simplification of a reactive power compensation system is very difficult. Here, the authors develop a new method, that is, neutral line current separating and combining method. Applying the neutral line current separating and combining method to the Cross vector theory, control system of the instantaneous reactive power compensator for the three-phase four-wire system can be simplified.