DEVELOPMENT OF A MULTI-FUNCTIONAL SINGLE STAGE CAPACITIVE -COUPLING GRID-CONNECTED INVERTER FOR PHOTOVOLTAIC INTEGRATION by Tao Ye Thesis Supervisor: Dr. Ning-Yi Dai Electrical and Computer Engineering Building integrated Photovoltaics (PVs) system is one of the most promising and elegant ways of producing on-site electricity. A single stage converter is a simple and cost-effective solution for converting the PV modules’ DC output to AC compatible with the utility grid. In this study, a single stage capacitive-coupling grid-connected inverter (CGCI) for photovoltaic integration is applied to achieve PV integration and power quality conditioning simultaneously. The multi-functional CGCI could not only injects active power to the grid, but also provides ancillary service such as reactive power control and harmonics compensation. This inverter could operate with a low DC link voltage so that less PV modules are required to connect in series. The design and control of a single stage CGCI with PV integration has been studied. Following research work has been focused on:  The maximum power point tracking (MPPT) was implemented for improving the efficiency of the PV integration. The DC voltage regulation under different PV operation modes were developed for the CGCI with PV integration.  A quasi proportional resonant (quasi-PR) controller has been developed for the CGCI to reduce steady state current tracking error. A comprehensive design method for the quasi-PR controller was proposed. Comparison with conventional PI controller was also provided.  The capacitive coupling impedance design is optimized by selecting its resonant frequency to improve harmonic compensation and to attenuate high frequency current ripples. As a result, there is no need to use multiple proportional resonant controllers for harmonic compensation and there is no need to use LCL filter and damping method. Simulation verifications were provided and comparison with a conventional single stage grid-connected inverter using LCL filter has been done. Finally, a 1.5 kW/110V prototype was built and tested to validate the effectiveness of the proposed multifunctional single stage CGCI for PV integration.