A transformerless Z-source photovoltaic grid-connected inverter with coupled inductor coil

Abstract

The quasi-Z-source H-bridge grid-connected inverter (QHGCI) is well known for its advantages of the void of the shoot-through problem and the high DC-voltage utilization. But the existence of the common-mode leakage current in the power frequency cycle, lower power density, and higher thermal stress make it hard applicable to the grid-penetrating application. Thus with the purpose to conquer the problem relating to the QHGCI, an innovative transformerless Z-source photovoltaic grid-connected inverter with a coupled inductor coil (TZPGCI-CIC) is proposed. The circuitry topology and an unipolar sine pulse width modulation strategy are first introduced in short. Thereafter, the common-mode voltage in the whole working process is derived and evaluated through the detailed operating mode analysis, in which a constant value of it has been theoretically revealed. Lastly, a prototype platform of TZPGCI-CIC is set up and its good performance on leakage current suppression, and lower thermal stress are validated with the experimental results.