Research on an Improved Single-Phase Unisolated Grid-Connected Photovoltaic Inverter

An improved single-phase unisolated grid-connected photovoltaic inverter topology is proposed to solve the common mode leakage current problem of unisolated grid-connected photovoltaic inverters. By analyzing the topology structure and voltage clamping principle of the improved inverter, the topology can maintain the same low input voltage as the full-bridge inverter, and ensure that the common-mode voltage in the continuation mode is clamped to the midpoint voltage of the bus, so as to effectively reduce the common-mode leakage current caused by the common-mode voltage suspension in the continuation mode. Moreover, the common-mode leakage current of the improved topology is smaller than that of the traditional H6-2D topology at similar conversion efficiency. The simulation results on MATLAB /Simulink platform show that the topology is feasible and effective.

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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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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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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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Carrier-Based PWM Method to Reduce Common-Mode Voltage of Three-to-Five-Phase Indirect Matrix Converter

Mathematical Problems in Engineering ◽

10.1155/2016/6086497 ◽

2016 ◽

Vol 2016 ◽

pp. 1-10 ◽

Cited By ~ 3

Author(s):

Rutian Wang ◽

Xingjun Mu ◽

Zhiqiang Wu ◽

Lihui Zhu ◽

Qiufeng Chen ◽

...

Keyword(s):

Simulation Model ◽

Matrix Converter ◽

Common Mode ◽

Matlab Simulink ◽

Absolute Value ◽

Common Mode Voltage ◽

Simulink Simulation ◽

The Common ◽

Simulation Results ◽

Input Phase

In order to reduce the common-mode voltage (CMV) for three-to-five-phase indirect matrix converter (IMC), the CMV with the conventional modulation strategy is analyzed. A novel carrier-based PWM (CBPWM) method is proposed in this paper. The zero vectors in the inverter stage are assigned to the rectifier stage, equivalently, which are not considered in the inverter stage. The zero vectors are selected appropriately to ensure that the dc-link is connected to an input phase with the minimum absolute value, so that the larger CMV can be avoided. Then, the modulation signals are derived by the duty ratios, which are used to compare with the only one carrier signal and generate the gate pulses of switches. With the proposed method, the CMV is reduced effectively compared with the conventional modulation strategy. This method is analyzed and researched with a simulation model established by Matlab/Simulink. Simulation results are provided in detail to verify the feasibility and validity of the proposed method.

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

Electronics ◽

10.3390/electronics10192382 ◽

2021 ◽

Vol 10 (19) ◽

pp. 2382

Author(s):

Aleksey V. Udovichenko ◽

Sergey V. Brovanov ◽

Evgeny V. Grishanov ◽

Svetlana M. Stennikova

Keyword(s):

Leakage Current ◽

Pulse Width Modulation ◽

Renewable Energy Sources ◽

Multilevel Converter ◽

Generation System ◽

Common Mode ◽

Common Mode Voltage ◽

Modulation Mode ◽

The Common ◽

Pv Generation

Power generation systems (PGSs) based on renewable energy sources are finding ever-widening applications, and many researchers work on this problem. Many papers address the problem of transformerless PGSs, but few of them aimed at conducting research on structures with multilevel converter topologies as part of a PGS. In this paper a grid-tied transformerless PV-generation system based on a multilevel converter is discussed. There are common-mode leakage currents (CMLCs), 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 PWM technique with the reduction of common-mode leakage current for a generation system based on the multilevel converter controlled with a PWM technique was verified experimentally. The experimental results accurately confirmed the mathematical model and the compensation achieved without errors. In the experiment, there was an approximately six-fold decrease in the common-mode leakage current (10.3 mA in rejection mode and 61 mA in non-rejection current). This can lead to the elimination of CMLC in a multilevel semiconductor converter only by changing the modulation mode. This suggests the possibility of using these devices as part of transformerless generation systems. Suppression of CMLC can only be carried out by changing the PWM algorithm. Both considered topologies can implement this mode of operation. The proposed converter has a higher efficiency up to a frequency multiplicity of 2000.

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Leakage Current Reduction in Single-Phase Grid-Connected Inverters—A Review

Applied Sciences ◽

10.3390/app10072384 ◽

2020 ◽

Vol 10 (7) ◽

pp. 2384 ◽

Cited By ~ 1

Author(s):

Adyr A. Estévez-Bén ◽

Alfredo Alvarez-Diazcomas ◽

Gonzalo Macias-Bobadilla ◽

Juvenal Rodríguez-Reséndiz

Keyword(s):

Leakage Current ◽

Harmonic Distortion ◽

Clean Energy ◽

Photovoltaic Module ◽

Common Mode ◽

Advantages And Disadvantages ◽

Common Mode Voltage ◽

The Common ◽

Ac Converters ◽

Current Reduction

The rise in renewable energy has increased the use of DC/AC converters, which transform the direct current to alternating current. These devices, generally called inverters, are mainly used as an interface between clean energy and the grid. It is estimated that 21% of the global electricity generation capacity from renewable sources is supplied by photovoltaic systems. In these systems, a transformer to ensure grid isolation is used. Nevertheless, the transformer makes the system expensive, heavy, bulky and reduces its efficiency. Therefore, transformerless schemes are used to eliminate the mentioned disadvantages. One of the main drawbacks of transformerless topologies is the presence of a leakage current between the physical earth of the grid and the parasitic capacitances of the photovoltaic module terminals. The leakage current depends on the value of the parasitic capacitances of the panel and the common-mode voltage. At the same time, the common-mode voltage depends on the modulation strategy used. Therefore, by the manipulation of the modulation technique, is accomplished a decrease in the leakage current. However, the connection standards for photovoltaic inverters establish a maximum total harmonic distortion of 5%. In this paper an analysis of the common-mode voltage and its influence on the value of the leakage current is described. The main topologies and strategies used to reduce the leakage current in transformerless schemes are summarized, highlighting advantages and disadvantages and establishing points of comparison with similar topologies. A comparative table with the most important aspects of each converter is shown based on number of components, modes of operation, type of modulation strategy used, and the leakage current value obtained. It is important to mention that analyzed topologies present a variation of the leakage current between 0 to 180 mA. Finally, the trends, problems, and researches on transformerless grid-connected PV systems are discussed.

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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 Power Electronic Inverter Circuit for Transformerless Photovoltaic Systems

Active and Passive Electronic Components ◽

10.1155/2014/329043 ◽

2014 ◽

Vol 2014 ◽

pp. 1-5 ◽

Cited By ~ 1

Author(s):

Cao Hai-Yan

Keyword(s):

Leakage Current ◽

Photovoltaic Systems ◽

Power Electronic ◽

Test Results ◽

Common Mode ◽

Common Mode Voltage ◽

Evaluation Test ◽

Mode Characteristic ◽

The Common ◽

Inverter Circuit

Capacitive leakage current is one of the most important issues for transformerless photovoltaic systems. In order to deal with the capacitive leakage current, a new power electronic inverter circuit is proposed in this paper. The inverter circuit consists of six switches and operates with constant common mode voltage. Theoretical analysis is conducted to clarify the circuit operation principle and the common mode characteristic. The performance evaluation test is carried out, and test results demonstrate that the capacitive leakage current can be significantly minimized with the proposed power electronic inverter circuit.

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A Limited Common-Mode Current Switched-Capacitor Multilevel Inverter Topology and Its Performance and Lifetime Evaluation in Grid-Connected Photovoltaic Applications

Energies ◽

10.3390/en14071915 ◽

2021 ◽

Vol 14 (7) ◽

pp. 1915

Author(s):

Hossein Khoun Jahan ◽

Reyhaneh Eskandari ◽

Tohid Rahimi ◽

Rasoul Shalchi Alishah ◽

Lei Ding ◽

...

Keyword(s):

Lifetime Distribution ◽

Multilevel Inverter ◽

Switched Capacitor ◽

Common Mode ◽

Common Mode Voltage ◽

Photovoltaic Applications ◽

Simulation Results ◽

Current Reduction ◽

Inverter Topology ◽

Mission Profile

In this paper, a switched-capacitor multilevel inverter with voltage boosting and common-mode-voltage reduction capabilities is put forth. The proposed inverter is synthesized with one-half bridge and several switched-capacitor cells. Due to the voltage boosting and common-mode current reduction features, the proposed multilevel inverter is suitable for grid-connected PV applications. In addition, an analytical lifetime evaluation based on mission profile of the proposed inverter has been presented to derive lifetime distribution of semiconductors. Whereas in the proposed inverter, any components failure can bring the whole system to a shutdown. The series reliability model is used to estimate the lifetime of the overall system. The performance of the suggested multilevel inverter in grid-connected applications is verified through the simulation results using the grid-tied model in Matlab/Simulink. Moreover, the viability and feasibility of the presented inverter are proven by using a one kW lab-scaled prototype.

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Investigation of common-mode voltage and ground leakage current of grid-connected transformerless PV inverter topology

Journal of Energy in Southern Africa ◽

10.17159/2413-3051/2015/v26i1a2217 ◽

2015 ◽

Vol 26 (1) ◽

pp. 20-24

Author(s):

Atanda K. Raji ◽

Mohamed T. E. Kahn

Keyword(s):

Solar Energy ◽

Leakage Current ◽

Energy System ◽

Common Mode ◽

System Cost ◽

Pv Inverter ◽

Common Mode Voltage ◽

The Cost ◽

Isolation Transformer ◽

Inverter Topology

The problems of increasing electricity demand by the unabated population and economy growth can be solved by employing sustainable distributed generation technologies. Convectional primary energy sources such as coal, liquid hydrocarbons’ and natural gasses create environmental degradation and energy security problems. Even though the cost of solar energy is zero, the same cannot be said of a solar energy system. The system cost especially the initial capital investment has been hindering the rapid deployment of solar energy systems. One way of reducing the system cost of a solar energy system is to look into the constituent components and see where cost can be reduced without compromising the system efficiency and human safety. Eliminating the isolation transformer reduces the cost and increases the system overall efficiency. However, the galvanic connection between the PV array and the utility grid creates a safety problem for people and system equipment. We present a simplified model for the investigation of the common mode voltage and ground leakage current that can lead to electromagnetic interference. The leakage current level is used for the determination of the suitability of the investigated PV inverter topology for grid connection without isolation transformer.

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