Highly Efficient Transformerless Inverter with Flying-Capacitor Buck–Boost for Single-Phase Grid-Connected PV Systems

Grid-connected inverters (GCI) are commonly used in PV system applications to generate a regulated AC current to feed into the grid. Transformerless inverters are the most advanced inverters that are used in industry, which provide efficiency with smaller size and lower cost. This paper proposes a grid-connected single-phase transformerless inverter with the technology of common ground and the virtual DC bus concept. In this topology, the grid neutral is connected directly to the PV ground, which generates a constant common mode voltage (CMV), thus leading to the elimination of the leakage current caused by the PV array’s parasitic capacitance. The proposed inverter has a buck–boost circuit with a flying capacitor to generate the DC bus for a negative power cycle, four switches, and two diodes. A unipolar sinusoidal pulse width modulation (SPWM) technique is used which reduces the output filter requirements. In addition, only one switch carries the load current during the active states of both the negative and positive power cycle, thus minimizing the conduction losses. One more advantage presented in the proposed inverter is its ability to charge the flying capacitor during all operation states due to the existence of the buck–boost circuit. Design and theoretical calculations were conducted in this paper to optimize the losses. Moreover, the PSIM simulation was used to validate the proposed topology inverter, verify the performance by showing leakage current elimination, and achieve unipolar voltage in the output bus. The simulation results show a peak efficiency of 98.57% for a 2 kW inverter, which agrees with the theoretical calculations.

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An Efficient H7 Single-Phase Photovoltaic Grid Connected Inverter for CMC Conceptualization and Mitigation Method

Electronics ◽

10.3390/electronics9091440 ◽

2020 ◽

Vol 9 (9) ◽

pp. 1440 ◽

Cited By ~ 2

Author(s):

Mehrdad Mahmoudian ◽

Eduardo M. G. Rodrigues ◽

Edris Pouresmaeil

Keyword(s):

Leakage Current ◽

Single Phase ◽

Pulse Width Modulation ◽

Reactive Power ◽

Negative Impact ◽

Harmonic Distortion ◽

Common Mode ◽

Safety Issues ◽

Common Mode Voltage ◽

Circuit Components

Transformerless inverters are the economic choice as power interfaces between photovoltaic (PV) renewable sources and the power grid. Without galvanic isolation and adequate power convert design, single-phase grid connected inverters may have limited performance due to the presence of a significant common mode ground current by creating safety issues and enhancing the negative impact of harmonics in the grid current. This paper proposes an extended H6 transformerless inverter that uses an additional power switch (H7) to improve common mode leakage current mitigation in a single-phase utility grid. The switch with a diode in series connection aims to make an effective clamp of common mode voltage at the DC link midpoint. The principles of operation of the proposed structure with bipolar sinusoidal pulse width modulation (SPWM) is presented and formulated. Laboratory tests’ performance is detailed and evaluated in comparison with well-known single-phase transformer-less topologies in terms of power conversion efficiency, total harmonic distortion (THD) level, and circuit components number. The studied topology performance evaluation is completed with the inclusion of reactive power compensation functionality verified by a low-power laboratory implementation with 98.02% efficiency and 30.3 mA for the leakage current.

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Current Source AC-Side Clamped Inverter for Leakage Current Reduction in Grid-Connected PV System

Electronics ◽

10.3390/electronics8111296 ◽

2019 ◽

Vol 8 (11) ◽

pp. 1296 ◽

Cited By ~ 4

Author(s):

Li ◽

Wang ◽

San ◽

Guo

Keyword(s):

Leakage Current ◽

Single Phase ◽

Current Source ◽

Electrolytic Capacitor ◽

Modulation Method ◽

Switching Frequency ◽

Pv System ◽

Common Mode ◽

Common Mode Voltage ◽

Single Phase Inverter

For the grid-connected photovoltaic inverters, the switching-frequency common-mode voltage brings the leakage current, which should be eliminated. So far, many kinds of single-phase inverters have been published for this purpose, but most of them are the conventional voltage-type ones, which have the disadvantages of poor reliability due to the DC-link electrolytic capacitor and the risk of short-through of the bridge switches. To solve this technical issue, a novel current source inverter with AC-side clamping is proposed to mitigate the switching-frequency common-mode voltage. Meanwhile, a novel modulation method is proposed for the new single-phase inverter to achieve low-frequency operation of the main switches, which reduces the switching losses. Finally, the proposed method is implemented on the TMS320F28335DSP + XC6SLX9FPGA digital hardware platform. Also, the performance comparisons are done with the traditional solution. The results prove the proposed solution.

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A Novel Inverter Topology for Single-Phase Transformerless PV System

Active and Passive Electronic Components ◽

10.1155/2016/1962438 ◽

2016 ◽

Vol 2016 ◽

pp. 1-6

Author(s):

Haiyan Cao

Keyword(s):

Leakage Current ◽

Single Phase ◽

High Efficiency ◽

Low Cost ◽

Experimental Tests ◽

Pv System ◽

Common Mode ◽

Common Mode Voltage ◽

The Common ◽

Inverter Topology

Transformerless photovoltaic (PV) power system is very promising due to its low cost, small size, and high efficiency. One of its most important issues is how to prevent the common mode leakage current. In order to solve the problem, a new inverter is proposed in this paper. The system common mode model is established, and the four operation modes of the inverter are analyzed. It reveals that the common mode voltage can be kept constant, and consequently the leakage current can be suppressed. Finally, the experimental tests are conducted. The experimental results verify the effectiveness of the proposed solution.

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New Pulse Width Modulation Technique to Reduce Losses for Three-Phase Photovoltaic Inverters

Active and Passive Electronic Components ◽

10.1155/2018/4157614 ◽

2018 ◽

Vol 2018 ◽

pp. 1-10 ◽

Cited By ~ 1

Author(s):

Mohannad Jabbar Mnati ◽

Dimitar V. Bozalakov ◽

Alex Van den Bossche

Keyword(s):

Control Strategy ◽

Pulse Width Modulation ◽

Photovoltaic System ◽

Pv System ◽

Total Cost ◽

Switching Losses ◽

Three Phase ◽

Operational Lifetime ◽

Term Energy ◽

Dc Bus

Nowadays, most three-phase, “off the shelf” inverters use electrolytic capacitors at the DC bus to provide short term energy storage. However, this has a direct impact on inverter lifetime and the total cost of the photovoltaic system. This article proposes a novel control strategy called a 120° bus clamped PWM (120BCM). The 120BCM modulates the DC bus and uses a smaller DC bus capacitor value, which is typical for film capacitors. Hence, the inverter lifetime can be increased up to the operational lifetime of the photovoltaic panels. Thus, the total cost of ownership of the PV system will decrease significantly. Furthermore, the proposed 120BCM control strategy modulates only one phase current at a time by using only one leg to perform the modulation. As a result, switching losses are significantly reduced. The full system setup is designed and presented in this paper with some practical results.

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Feed‐forward DC‐bus control loop applied to a single‐phase grid‐connected PV system operating with PSO‐based MPPT technique and active power‐line conditioning

IET Renewable Power Generation ◽

10.1049/iet-rpg.2016.0120 ◽

2016 ◽

Vol 11 (1) ◽

pp. 183-193 ◽

Cited By ~ 29

Author(s):

Sérgio Augusto OLiveira da Silva ◽

Leonardo Poltronieri Sampaio ◽

Fernando Marcos de Oliveira ◽

Fábio Renan Durand

Keyword(s):

Single Phase ◽

Power Line ◽

Active Power ◽

Control Loop ◽

Pv System ◽

Feed Forward ◽

Dc Bus ◽

System Operating

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A Topology Synthetization Method for Single-Phase, Full-Bridge, Transformerless Inverter with Leakage Current Suppression Part I

Energies ◽

10.3390/en13020434 ◽

2020 ◽

Vol 13 (2) ◽

pp. 434 ◽

Cited By ~ 1

Author(s):

Xiumei Yue ◽

Hongliang Wang ◽

Xiaonan Zhu ◽

Xinwei Wei ◽

Yan-Fei Liu

Keyword(s):

Leakage Current ◽

Pulse Width ◽

Single Phase ◽

Pulse Width Modulation ◽

Circuit Model ◽

Double Frequency ◽

Highly Efficient ◽

Sinusoidal Pulse Width Modulation ◽

Derivation Procedure ◽

Bridge Topologies

Single-phase full-bridge transformerless topologies, such as the H5, H6, or the highly efficient and reliable inverter concept (HERIC) topologies, are commonly used for leakage current suppression for photovoltaic (PV) applications. The main derivation methodology of full-bridge topologies has been used based on both a DC-based decoupling model and an AC-based decoupling model. However, this methodology is not suited to the search for all possible topologies, and cannot verify whether they are inclusive. Part I of this paper will propose a new topology derivation methodology based on unipolar sinusoidal pulse width modulation (USPWM) to search all possible full-bridge topologies for leakage current suppression. First of all, a unified circuit model is proposed, instead of the DC- and AC-based models. Secondly, a mathematic method called the MN principle is then proposed to search for all possible topologies, and a derivation procedure is provided. It was verified that all existing topologies could be found using the proposed method; furthermore, seven new topologies were derived. The proposed topology derivation methodology is extended to search topologies under Double-Frequency USPWM (DFUSPWM). Twenty topologies under USPWM and four topologies under DFUSPWM have been derived.

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Transformerless Quasi-Z-Source Inverter to Reduce Leakage Current for Single-Phase Grid-Tied Applications

Electronics ◽

10.3390/electronics8030312 ◽

2019 ◽

Vol 8 (3) ◽

pp. 312 ◽

Cited By ~ 4

Author(s):

Woo-Young Choi ◽

Min-Kwon Yang

Keyword(s):

Leakage Current ◽

Power Efficiency ◽

High Performance ◽

Single Phase ◽

Power Devices ◽

Common Mode Voltage ◽

Control Scheme ◽

Frequency Components ◽

The Common ◽

Current Reduction

The conventional single-phase quasi-Z-source (QZS) inverter has a high leakage current as it is connected to the grid. To address this problem, this paper proposes a transformerless QZS inverter, which can reduce the leakage current for single-phase grid-tied applications. The proposed inverter effectively alleviates the leakage current problem by removing high-frequency components for the common-mode voltage. The operation principle of the proposed inverter is described together with its control strategy. A control scheme is presented for regulating the DC-link voltage and the grid current. A 1.0 kW prototype inverter was designed and tested to verify the performance of the proposed inverter. Silicon carbide (SiC) power devices were applied to the proposed inverter to increase the power efficiency. The experimental results showed that the proposed inverter achieved high performance for leakage current reduction and power efficiency improvement.

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A Five-Level Converter in a Three-Level Mode for Common-Mode Leakage Current Suppression in PV-Generation Systems

10.20944/preprints202107.0304.v1 ◽

2021 ◽

Author(s):

Aleksey Vyacheslavovich Udovichenko ◽

Sergey Viktorovich Brovanov ◽

Evgeny Valerievich Grishanov ◽

Svetlana Mikhailovna Stennikova

Keyword(s):

Leakage Current ◽

Pulse Width ◽

Pulse Width Modulation ◽

Renewable Energy Sources ◽

Multilevel Converter ◽

Generation System ◽

Common Mode ◽

Common Mode Voltage ◽

Conducting Research ◽

Pv Generation

Power generation systems based on renewable energy sources are finding ever-widening applications and many researchers work on this problem. Many papers address the problem of transformerless structures, but few of them are aimed at conducting research on structures with multilevel converter topologies. In this paper a grid-tied transformerless PV-generation system based on a multilevel converter is discussed. There are common-mode leakage currents which act as a parasitic factor. It is also known that common-mode voltage is the main cause of the common-mode leakage current in grid-tied PV-generation systems. This paper considers the space vector pulse-width modulation (PWM) technique which is used to suppress or reduce common-mode leakage current. The proposed engineering solutions for a generation system based on the multilevel converter controlled with a pulse-width modulation technique are verified by experiment.

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