Simple Technique Reducing Leakage Current for H-Bridge Converter in Transformerless Photovoltaic Generation

Abstract

Given their structural arrangement, photovoltaic (PV) modules exhibit parasitic capacitance, which creates a path for high-frequency current during zero-state switching of the converter in transformerless systems. This current has to be limited to ensure safety and electromagnetic compatibility. Many solutions that can minimize or completely avoid this phenomenon, are available. However, most of these solutions are patented because they rely on specific and often complex converter topologies. This study aims to solve this problem by introducing a solution based on a classic converter topology with an appropriate modulation technique and passive filtering. A 5.5 kW single-phase residential PV system that consists of DC-DC boost stage and DC-AC H-bridge converter is considered. Control schemes for both converter stages are presented. An overview of existing modulation techniques for H-bridge converter is provided, and a modification of hybrid modulation is proposed. A system prototype is built for the experimental verification. As shown in the study, with simple filtering and proper selection of switching states, achieving low leakage current level is possible while maintaining high converter efficiency and required energy quality.

Design and Implementation of Single-Phase Grid-Connected Low-Voltage Battery Inverter for Residential Applications

“…The positive half of m(t) is used as the duty ratio reference for switches S 9 and S 10 , and the positive half of −m(t) for switches S 11 and S 12 . This PWM technique has a lower commonmode voltage and switching loss than the unipolar PWM [27]. Meanwhile, the VSC current i 1 (t) maintains a small ripple due to the three-level voltage output at the VSC terminal.…”

“…The discrete-time PI controller G CB (z) regulates the battery current i B (k) at instant k with the reference phase angle δ * (k) as the output. The reference angles δ * 1 (k), δ 4 (k), δ * 5 (k), and δ * 8 (k) are obtained from (27). The reference angles δ * 1 (k) and δ * 8 (k) are translated to the values of the CMPA3, CMPB3, CMPA6, and CMPB6 registers as depicted in Figure 11.…”

Comparison of Energy Storage Management Techniques for a Grid-Connected PV- and Battery-Supplied Residential System

“…The PV system controller is responsible for the generation of maximum available power. Therefore, a Maximum Power Point Tracking (MPPT) method sets the reference voltage v * pv at which the output power is maximum [35]. Then, the reference PV voltage v * pv is sent to an outer PI controller to set the reference current i * u , for the inner PI controller.…”