Here, a highly efficient MOSFET neutral‐point‐clamped (M‐NPC) transformerless inverter is proposed for photovoltaic (PV) applications. By employing super‐junction metal–oxide–semiconductor field‐effect transistor (SJ‐MOSFET) as well as silicon carbide (SiC) diodes, high efficiency is achieved. Furthermore, the common‐mode voltage (CMV) is completely clamped at half of the input voltage with clamping branch. Therefore, leakage current is eliminated. The performances of different topologies, in terms of CMV, leakage current, total harmonic distortion (THD), losses, and efficiency, are compared with the proposed M‐NPC topology. The analyses are carried out theoretically via MATLAB/Simulink, and further validated with experimental tests. The experimental results show maximum efficiency of 98.5% and European efficiency of 97.65%.

In grid connected photovoltaic (PV) systems transformerless inverters are widely used due to reduced size, weight and cost. However, common mode voltage reduction is one of the most key issues for transformerless PV inverters. In addition, several attractive single-phase transformerless inverter topologies have been reported to eliminate the common mode voltage based on converter topology and modulation strategy. Moreover, in literature three-phase topologies with reduced common mode voltage are not well investigated. In this paper, a novel three phase eight switch inverter (H8) and a corresponding modulation technique is proposed to reduce the common mode voltage. It is derived from the standard three-phase (H6) inverter but has different operating principles. Theoretical and performance analyses are carried out via MATLAB/Simulink to validate the effectiveness of the proposed H8 topology.

The series-connected offshore wind energy conversion system (WECS) removes the need for bulky and costly offshore substations. In this system, a current-fed bidirectional isolated DC-DC converter such as the hybrid dual active bridge (HDAB), is essential to supply power from the onshore grid to the wind farm’s local load when there is no wind. However, the reverse-blocking bridge arms on the current-source (CS) side of the HDAB remain off if the auxiliary power supply (APS) is unavailable, preventing the WECS from starting when wind turbines are idle. Moreover, a clamp circuit is needed on the CS side to suppress voltage spikes. This paper presents an improved clamp circuit configuration for HDAB, integrating the CS-side APS with the clamp circuit to provide charging path from the CS-side bus to the APS input. Additionally, a CS-side start-up strategy for HDAB is proposed. The proposed method suppresses voltage spikes and make it possible to power up the APS by the CS-side bus, even without a power source on the voltage side. Simulation and experimental results verify the correctness of the proposed method.