单相非隔离型改进Y源光伏并网逆变器

In order to solve the problem of common mode current when a traditional Y-source photovoltaic (PV) inverter is connected to a grid, a line-frequency or high-frequency transformer is usually connected in series between the grid and PV system to ensure galvanic isolation. However, the line-frequency transformer is heavy and big, and the high-frequency transformer needs additional energy conversion circuits, which leads to complex control and low efficiency. Thus, a novel transformerless Y-source PV grid-connected inverter is proposed. This new topology connects the negative terminal of PV array to the neutral line of the grid directly, the virtual dc link is introduced, and the pulse width modulation (PWM) strategy is modified. Moreover, the voltage and current stresses are analyzed, and capacitances of capacitors are optimized to solve the voltage drop during the negative half cycle. Finally, a 200 W laboratory prototype based on TMS320F28335 is built to verify the performance of the proposed topology. Simulation and experimental results indicate that the new topology guarantees the quality of the grid-connected current while the loop of common mode current is bypassed and the common mode current is completely eliminated. The proposed transformerless Y-source inverter topology can reduce the volume and cost of inverter, and can provide support for the connection of PV to the grid.