Recent advances in single‐phase transformerless photovoltaic inverters

Abstract

Photovoltaic (PV) power systems have been in the spotlight of scientific research for years. However, this technology is still undergoing developments, and several new architectures are proposed each year. This study describes the main challenges facing grid-connected PV systems without galvanic isolation, then carries out a review of the state-of-the-art of single-phase systems. The converter topology review is focused on the match between the different types of converters and the different PV panel technologies, determined by the common-mode voltage between the PV string terminals and the ground. The ground leakage current, due to time variations of this voltage, is a source of electric safety and electromagnetic interference (EMI)-related problems, and its amplitude is constrained by international standards. The basic principles of operation of the different solutions are described, along with their strengths and drawbacks. Conversion efficiency is evaluated qualitatively comparing the semiconductor power losses. Finally, the future trends regarding semiconductor devices, PV panels and international regulations for single-phase grid-connected equipment are discussed, and indications on how these might steer future research efforts in PV converters are inferred

A PV-Inspired Low-Common-Mode Dual-Active-Bridge Converter for Aerospace Applications

“…Differently from the simulations, where the devices performed ideal commutations and presented no parasitic elements, in the experiments a small common-mode voltage variation happens. This phenomenon is the same behavior of a bipolar H-bridge performing non-ideal commutations in a PV inverter: a small common-mode current flows [11]. This problem can be addressed via a careful optimization of the circuit layout and the equalization of the pulse times.…”

“…Hard-grounding of the power bus is one of the possibilities to reduce the common-mode noise at the user interface [10]. However, as a common power ground exists, common-mode currents can flow between the converters, in a similar fashion to what happens in the low-voltage grids with the Terra-Terra (TT, doubly grounded) distribution system, where each converter shares the same ground [11]. These currents must be minimised as well, calling for low-commonmode power converters.…”

“…To reduce the common-mode voltage of power converters, in the recent years, many modifications of the H-bridge topology were proposed for DC/AC photovoltaic (PV) converters [11], [18]. The basic idea is to decouple the DC input and the AC output during the converter zero state; this can be done with additional switches in the DC side (like the H5 or H6 solutions) or a bi-directional switch in the AC side (Highly Efficient and Reliable Inverter Concept, HERIC).…”

Investigation on Common-Mode Voltage Suppression in Smart Transformer-Fed Distributed Hybrid Grids

“…The CM voltage affects the load when the parasitic capacitor is non-negligible, such as PV panel connecting to the ST [27].…”

All SiC Grid-Connected PV Supply with HF Link MPPT Converter: System Design Methodology and Development of a 20 kHz, 25 kVA Prototype

“…Various grid-connected photovoltaic system concepts and topologies have been summarized previously [1][2][3][4]: (i) micro inverters [5,6]; (ii) residential systems supplied from a PV string [7,8]; (iii) commercial/residential systems supplied from multiple PV strings having their own maximum power point tracking (MPPT) converters and a central inverter [9,10]; and (iv) commercial/utility-scale PV plants supplied from a common DC link with a central inverter [11]. The central inverter in [11] performs direct conversion of PV power to AC from multiple PV strings.…”