New inverter control for balancing standalone micro-grid phase voltages: A review on MG power quality improvement

Standalone MicroGrid (MG) suffers from high voltage unbalancing due to both single phase and unbalanced loads. This paper presents a comprehensive survey about the available techniques and controllers for MG power quality improvement. Recent trends and schemes for the standalone MG power quality improvement are reported in detail. The techniques which concern with the MG voltage unbalancing issue are highlighted. In addition, this paper develops a simple scheme for balancing the MG phase voltages. The proposed scheme employs a new interfacing inverter topology and control. The three phase compact unit interfacing inverter of the Distributed Generators (DGs) has been rebuilt in form of three single phase inverter units. Each single phase inverter unit is controlled independently to achieve MG phase voltage balancing. At different load operating conditions, the three single phase inverter units run at different values and types (leading or lagging) power factors (PF). Employing the proposed inverter control achieves perfect phase voltages balancing at the most MG buses. Before employing the proposed inverter control, the voltage unbalancing ratio at some buses exceeds than 6%. This ratio approximately shrinks to zero after including the proposed inverter control. The performance of the proposed inverter control has been tested under different load conditions. In addition, the performance of the proposed inverter control is compared with both the old inverter control (unity power factor inverter) and the conventional inverter control (constant power factor inverter) performance. Only, a simple modification to the old inverter control is sufficient to implement the new inverter control. The proposed inverter control is very simple and highly economical attractive.