Adaptive Control Schemes for Three-Phase Grid-Connected Inverters in Photovoltaic Power Generation Systems

Control of the three-phase photovoltaic (PV) inverters has drawn increasing attention in recent years for the development of solar energy technology. The fast development of signal processing techniques has made advanced control methods possible for the inverter control system. With the rapid growth of the usage of renewable energy, there have been more performance requirements proposed for PV inverter systems. This thesis studies the control problem for the three-phase PV grid-connected inverters. In particular, an adaptive control method is adopted to deal with system uncertainties in such a problem. In this research, the state-space model of the inverter system, which considers the uncertainties of system parameters, is established. Then two adaptive control designs to solve the control problem are developed: a state-feedback output-tracking adaptive control design and an output-feedback output-tracking adaptive control design. To eliminate the disturbance influence from the grid side, the adaptive controller is further designed to have the ability to compensate such effects to achieve desired adaptive and asymptotic disturbance rejection. Compared with a classical fixed-gain control method, the adaptive control method is capable of efficiently handling system uncertainties and dealing with some unknown disturbances. Analysis and simulation results have shown the effectiveness of the proposed adaptive control schemes.