Adaptive Trapezoidal Current Control for HERIC-Based Single-Phase Grid-Connected Inverters

This paper proposes an adaptive trapezoidal current control for Highly Efficient and Reliable Inverter Concept (HERIC)-based single-phase grid-connected inverters. By integrating trapezoidal current control within the HERIC topology, the common mode voltage is stabilized via the bidirectional branch, effectively suppressing leakage current below the 300-mA standard. This addresses the leakage current issue when applying trapezoidal current control to traditional Hbridge inverters and expands its applicability in transformerless photovoltaic inverter systems. Furthermore, the limitation of short control duration in trapezoidal current control is identified and mitigated through load-dependent adaptive adjustment of the reverse boundary current. This strategy extends the control duration by up to six times, greatly enhancing the practical implementation. Compared to conventional triangular current control, the proposed method also reduces peak current, current ripple, and switching frequency, resulting in up to a 1.3% improvement in efficiency. A comprehensive analysis is provided, covering operating principles, parameter selection, digital control implementation, and soft-switching verification. Experimental results from a 2 kW SiC-based prototype validate the effectiveness and performance advantages of the proposed approach.