Capacitive reactive power compensation to prevent voltage instabilities in distribution lines

Abstract

This article presents an efficient voltage regulation method using capacitive reactive power. Simultaneous operation of photovoltaic power systems with the local grids induces voltage instabilities in the distribution lines. These voltage fluctuations cross the allowable limits on several occasions and cause economic losses. In the proposed method, the reactive power is applied at the load and generated using a capacitor bank. The capacitors are arranged in a binary order of capacitances to enable the 2n equally dispersed combinations. Initially, a strict analytical solution is developed to study the outcome of capacitance connection at load. The capacitance is selected based on the analytical solution of non-linear equations describing voltage deviations in the distribution line connected with photovoltaic systems. The control system is developed for fast and appropriate capacitance selection and a smooth transient process. The experimental setup is developed to verify the theoretical analysis. The measured data shows good agreement with the calculated one, verifying the correctness and accuracy of the proposed method. It is recommended that the reactive power compensation can be applied for a shorter time because the source current enhances substantially as the capacitance is connected to the load. The proposed method can be applied together with the tap-changers functionality, and the capacitance should be disconnected as the tap-changer corrects the transformation ratio.