Optimization and Performance Evaluation of Transformerless HERIC and H5 PV Inverters: Minimizing Leakage Current, Enhancing Efficiency, and Waveform Control

Photovoltaic (PV) systems frequently use transformerless inverters because of their high efficiency, small size, and lower cost. These systems convert DC to AC voltage/current via inverters but face challenges in managing leakage currents without isolation transformers. This paper, titled "Optimization and Performance Evaluation of Transformerless HERIC and H5 PV Inverters: Minimizing Leakage Current, Enhancing Efficiency, and Waveform Control " compares HERIC (Highly Efficient and Reliable Inverter Concept) and H5 inverter topologies, focusing on their effectiveness in reducing leakage currents and maintaining system efficiency.The HERIC topology is renowned for its excellent efficiency, but the H5 topology incorporates an extra switch into the traditional full-bridge design. Both achieve over 95% efficiency and reduce total harmonic distortion. Infineon (CoolMOS C7 Technology) MOSFETs and AVR ATXmega128A1U microcontrollers generating center-aligned Pulse width Modulation (PWM) are used to minimize switching losses. Simulated results for the HERIC topology show power efficiency exceeding 98.5%, though cost remains a barrier for large-scale production. PSPICE simulation experiments assess these topologies' performance under various loading scenarios. Switch junction capacitances cause serious common-mode voltage (CMV) problems for the HERIC design, despite its maximum efficiency. On the other hand, the H5 topology outperforms the conventional H4 (full bridge) design with a significant reduction in leakage current.Due to its advantages in terms of cost, size, and weight, transformerless topologies are widely used in PV inverter technology. This improves power factor and overall power efficiency at light loads. However, eliminating the transformer introduces challenges such as the need for galvanic isolation and the risk of dangerous leakage currents The improved HERIC inverter with a quasi-diode clamp construction is discussed in this paper in order to reduce CMV variations during freewheeling times and direct current (DC) injection into the grid. This paper discusses an optimized version of the HERIC inverter along with a quasi-diode clamp structure to mitigate common-mode voltage (CMV) fluctuations during the free-wheeling periods. Simulation models demonstrate the effectiveness of this approach in reducing leakage currents.Overall, this review highlights the critical aspects of HERIC and H5 inverter topologies, offering insights into their operational principles, modulation strategies, and performance metrics, aiding in developing more efficient and reliable PV systems.