Improved power controller for enhancement of voltage quality in microgrid

Abstract

In microgrid, non-linear or unbalanced loads will degrade the voltage quality at the output of the inverters, and the voltage of the load will be distorted or unbalanced. On the other hand, the inverters in microgrid are connected in parallel to improve efficiency, increase transmission capacity, and are easy to repair and maintain. When the microgrid is operating in standalone mode, inverters must be controlled to share power according to their rated power; this is to stabilize frequency and voltage in the microgrid. However, since non-linear or unbalanced loads will produce load currents containing harmonics, it will make the voltage of load unbalanced, which will affect the control of power-sharing for the inverters, and it also degrades the voltage quality at the output of the inverters. This paper has proposed an improved power-sharing control method combined with the sliding mode control (SMC) technique to improve the voltage quality and improve the accuracy of power-sharing for the inverters in the microgrid. The proposed method will ensure accurate power-sharing even if the communication is interrupted. If the load changes while the communication is interrupted, the accuracy of power-sharing is reduced but the proposed method is better than the conventional power-sharing method. In addition, the accuracy of the proposed power-sharing method is not affected by the time delay in the communication channel and local loads at the output of the inverters. Simulation and experimental results will prove the effectiveness of the proposed method.