Common-Ground Photovoltaic Inverters for Leakage Current Mitigation: Comparative Review

Abstract

In photovoltaic systems, parasitic capacitance is often formed between PV panels and the ground. Because of the switching nature of PV converters, a high-frequency voltage is usually generated over these parasitic capacitances; this, in turn, can result in a common-mode current known as leakage current. This current can badly reach a high value if a resonance circuit is excited through the PV’s parasitic capacitance and the converter’s inductive components. Transformers are usually used for leakage current mitigation. However, this decreases the efficiency and increases the cost, size, and weight of the PV systems. Number of strategies have been introduced to mitigate the leakage current in transformer-less converters. Among these strategies, using common-ground converters is considered the most effective solution as it offers a solid connection between the negative terminal of PV modules and the neutral of the grid side; thus, complete mitigation of the leakage current is achieved. Number of common-ground inverters have been recently presented. These inverters are different in their size, cost, boosting capability, the possibility of producing DC currents, and their capability to offer multilevel shaping of output voltage. This work introduces a comprehensive review and classification for various common-ground PV inverters. Therefore, a clear picture of the advantages and disadvantages of these inverters is clarified. This provides a useful indication for a trade-off between gaining some of the advantages and losing others in PV systems. In addition, the potentials for optimization based on different performance indicators are identified.

A Common Ground Four Quadrant Buck Converter for DC-AC Conversion

“…Therefore, improved DC-AC converter topologies are preferred over modulation techniques to eliminate leakage currents in non-isolated power conversion interface. [22] The half-bridge topology of the H-bridge family of inverters has reduced leakage current in comparison with the full-bridge topology but has only half the DC link voltage utilization. High efficient transformerless PV inverters with improved DC-link utilization are discussed in [23], [24].…”

“…A common-ground connection between the input and output terminals is most effective to bypass the parasitic capacitances, thereby eliminating leakage and circulating currents [32]. Accordingly, this concept has increasingly gained popularity [22], [33]. Common-ground multilevel transformerless inverters with improved DC bus utilization and no leakage current are presented in [34], [35].…”

Topology review of doubly grounded transformer‐less single‐phase inverters

“…Since grounds of the PV array and output terminal are shorted in the doubly grounded transformer-less single-phase inverters, the common mode leakage current can be eliminated thoroughly, shown in Figure 1. A comprehensive review and classification for various doubly grounded inverters were given in [56,57]. Topologies of doubly grounded inverters in [56,57] are classified into voltagesource inverters and current-source inverters.…”

“…A comprehensive review and classification for various doubly grounded inverters were given in [56,57]. Topologies of doubly grounded inverters in [56,57] are classified into voltagesource inverters and current-source inverters. However, detailed topology derivations for the doubly grounded transformer-less single-phase inverters are not explored.…”

A five‐level common‐ground inverter with step‐up/step‐down dual‐mode operation for transformerless grid‐connected PV application

“…In this type of inverters, the negative point of the PV stack is shared with the grid neutral terminal, hence a constant common-mode voltage results in null leakage current. [12][13][14][15][16] Several three-level (3L) common-ground inverters have been proposed in the literature. [17][18][19][20][21][22][23] They present less switch count at the cost of higher output voltage THD.…”