Investigation of Novel Control Strategies for Grid-Connected Photovoltaic Inverters

Abstract

With the increasing installation of grid-connected photovoltaic (PV) systems, advanced control strategies are needed for the PV inverters to ensure stable and high-performance operation. This paper investigates novel control techniques for three-phase grid-connected PV inverters to enhance the power quality and stability of the grid. First, a repetitive current controller is implemented to eliminate low-order grid current harmonics effectively. Second, a hybrid control strategy combining the benefits of deadbeat and repetitive controllers is proposed to achieve fast dynamic response and high power quality. Additionally, virtual impedance is added to strengthen the system stability through active damping. The third technique explored is a model predictive control with direct current control, providing fast tracking of the current reference and grid synchronisation. To validate the performance of the proposed methods, a three-phase 2.2 kW PV inverter is modelled in MATLAB/Simulink. Extensive simulations are performed under normal and abnormal grid conditions. The results demonstrate the effectiveness of the investigated techniques in terms of power quality enhancement, accurate current control and stability improvement compared to conventional control methods. The proposed strategies provide flexible and high-performance solutions for grid-connected PV systems to facilitate renewable integration. Further work involves experimental verification on a prototype to evaluate the practicality.