Design and control of a grid-connected three-phase 3-level NPC inverter for Building Integrated Photovoltaic systems

This paper presents the design and control of a grid-connected three-phase 3-level Neutral Point Clamped (NPC) inverter for Building Integrated Photovoltaic (BIPV) systems. The system consists of a PV array, boost DC/DC converter, 3-level NPC inverter, LC filter and the grid. The 3-level NPC inverter is designed without a galvanic isolation transformer and its current controller is developed to minimize leakage currents though common-mode voltage loops in the PV systems. A prototype 13kW NPC inverter with a LC filter was fabricated and tested, resulting in a low total harmonics distortion (THD) of less than 3% THD and 97.5% efficiency at the peak load. The detail simulation and test results are discussed.