High quality model predictive control for single phase grid-connected photovoltaic inverters

Abstract

Single phase grid-connected inverters with LCL filter are widely used to connect the photovoltaic systems to the utility grid. Among the presented control schemes, predictive control methods are faster and more accurate but are more complex to implement. Recently, the model-predictive control algorithm for single-phase inverter has been presented, where the algorithm implementation is straightforward. In the proposed approach, all switching states are tested in each switching period to achieve the control objectives. However, since the number of the switching states in single-phase inverter is low, the inverter output current has a high total harmonic distortions. In order to reduce the total harmonic distortions of the injected current, this paper presents a high-quality model-predictive control for one of the newest structure of the grid connected photovoltaic inverter, i.e., HERIC inverter with LCL filter. In the proposed approach, the switching algorithm is changed and the number of the switching states is increased by some virtual vectors. Simulation results show that the proposed approach lead to a lower total harmonic distortions in the injected current along with a fast dynamic response. The proposed predictive control has been simulated and implemented in a 1kW single-phase HERIC inverter with LCL filter at the output.