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

Electronics ◽  
2020 ◽  
Vol 9 (9) ◽  
pp. 1440 ◽  
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.

scholarly journals A New Approach to the PWM Modulation for the Multiphase Matrix Converters Supplying Loads with Open-End Winding

Energies ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 466
Author(s):  
Pawel Szczepankowski ◽  
Natalia Strzelecka ◽  
Enrique Romero-Cadaval
Keyword(s):  
Pulse Width Modulation ◽  
Harmonic Distortion ◽  
Simulation Software ◽  
Common Mode ◽  
New Approach ◽  
Matrix Converters ◽  
Load Voltage ◽  
Common Mode Voltage ◽  
The Common ◽  
Open End Winding

This article presents three variants of the Pulse Width Modulation (PWM) for the Double Square Multiphase type Conventional Matrix Converters (DSM-CMC) supplying loads with the open-end winding. The first variant of PWM offers the ability to obtain zero value of the common-mode voltage at the load’s terminals and applies only six switches within the modulation period. The second proposal archives for less Total Harmonic Distortion (THD) of the generated load voltage. The third variant of modulation concerns maximizing the voltage transfer ratio, minimizing the number of switching, and the common-mode voltage cancellation. The discussed modulations are based on the concept of sinusoidal voltage quadrature signals, which can be an effective alternative to the classic space-vector approach. In the proposed approach, the geometrical arrangement of basic vectors needed to synthesize output voltages is built from the less number of vectors, which is equal to the number of the matrix converter’s terminals. The PWM duty cycle computation is performed using only a second-order determinant of the voltages coordinate matrix without using trigonometric functions. A new approach to the PWM duty cycles computing and the load voltage synthesis by 5 × 5 and 12 × 12 topologies has been verified using the PSIM simulation software.

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

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.

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

Electronics ◽  
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.

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

2020 ◽  
Vol 10 (7) ◽  
pp. 2384 ◽  
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.

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

Electronics ◽  
2019 ◽  
Vol 8 (11) ◽  
pp. 1296 ◽  
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.

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

2021 ◽  
Vol 11 (22) ◽  
pp. 10841
Author(s):  
Ali Salem ◽  
Khaled Sedraoui
Keyword(s):  
Leakage Current ◽  
Single Phase ◽  
Common Ground ◽  
Pulse Width Modulation ◽  
Theoretical Calculations ◽  
Pv System ◽  
Negative Power ◽  
Power Cycle ◽  
Common Mode Voltage ◽  
Dc Bus

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.

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

2021 ◽  
Vol 23 (2) ◽  
pp. 123-130
Author(s):  
Baoge Zhang ◽  
Deyu Hong
Keyword(s):  
Leakage Current ◽  
Single Phase ◽  
Current Problem ◽  
Input Voltage ◽  
Common Mode ◽  
Common Mode Voltage ◽  
Voltage Clamping ◽  
The Common ◽  
Simulation Results ◽  
Inverter Topology

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.

Analytical study and simulation of a transformer-less photovoltaic grid-connected inverter with a delta-type tri-direction clamping cell for leakage current elimination

2018 ◽  
Vol 37 (2) ◽  
pp. 814-831 ◽  
Author(s):  
Tohid Jalilzadeh ◽  
Mehrdad Tarafdar Hagh ◽  
Mehran Sabahi
Keyword(s):  
Power Systems ◽  
Leakage Current ◽  
Control Method ◽  
Harmonic Distortion ◽  
Common Mode ◽  
Content Type ◽  
Low Leakage ◽  
Common Mode Voltage ◽  
Power Switches ◽  
The Common

PurposeThis paper aims to propose a new transformer-less inverter structure to reduce the common-mode leakage current in grid-connected photovoltaic (PV) systems. Design/methodology/approachThe proposed circuit structure is the same as the conventional full-bridge inverter with three additional power switches in a triangular structure. These three power switches are between the bridge and the output filter, and they mitigate the common-mode leakage current flowing toward the PV panels’ capacitors. The common-mode leakage current mitigation is done through the three-direction clamping cell (TDCC) concept. By clamping the common-mode voltage to the middle voltage of the DC-link capacitors, the leakage current and the total harmonic distortion (THD) of the injected current to the grid is effectively reduced. Therefore, the efficiency is improved. FindingsThe switching modes and the control method are introduced. A comparison is carried out between the proposed structure and other solutions in the literature. The proposed topology and its respective control method are simulated by PSCAD/EMTDC software. The simulation results validate the advantages of the presented structure such as clamping the common-mode voltage and reducing leakage current and THD of injected current to the grid. Originality/valuePresenting a single phase-improved inverter structure with low-leakage current for grid-connected PV power systems represents a significant original contribution to this work. The proposed structure can inject a sinusoidal current with low THD to the AC grid, and the power factor is unity on the AC side. In the half positive cycle, one of the switches in the TDCC is turned off under zero current. Besides, one of the other switches in TDCC is turned on with zero voltage and, therefore, its turn-on switching losses are zero. The efficiency of the proposed topology is high because of the reduction of leakage current and power losses. Accordingly, the presented topology can be a good solution to the leakage current elimination.

scholarly journals A Novel Inverter Topology for Single-Phase Transformerless PV System

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.

scholarly journals Common-Mode Voltage Harmonic Reduction in Variable Speed Drives Applying a Variable-Angle Carrier Phase-Displacement PWM Method

Energies ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2929
Author(s):  
Abraham Marquez Alcaide ◽  
Vito Giuseppe Monopoli ◽  
Xuchen Wang ◽  
Jose I. Leon ◽  
Giampaolo Buticchi ◽  
...  
Keyword(s):  
Carrier Phase ◽  
Harmonic Distortion ◽  
Harmonic Spectrum ◽  
Hydraulic Systems ◽  
Variable Speed ◽  
Common Mode ◽  
Variable Speed Drives ◽  
Phase Displacement ◽  
Common Mode Voltage ◽  
External Component

Electric variable speed drives (VSD) have been replacing mechanic and hydraulic systems in many sectors of industry and transportation because of their better performance and reduced cost. However, the electric systems still face the issue of being considered less reliable than the mechanical ones. For this reason, researchers have been actively investigating effective ways to increase the reliability of such systems. This paper is focused on the analysis of the common-mode voltage (CMV) generated by the operation of the VSDs which directly affects to the lifetime and reliability of the complete system. The method is based on the mathematical description of the harmonic spectrum of the CMV depending on the PWM method implementation. A generalized PWM method where the carriers present a variable phase-displacement is developed. As a result of the presented analysis, the CMV reduction is achieved by applying the PWM method with optimal carrier phase-displacement angles without any external component and/or passive filtering technique. The optimal values of the carrier phase-displacement angles are obtained considering the minimization of the CMV total harmonic distortion. The resulting method is easily implementable on mostly off-the-shelf mid-range micro-controller control platforms. The strategy has been evaluated in a scaled-down experimental setup proving its good performance.

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