H8 Inverter to Reduce Leakage Current in Transformerless Three-Phase Grid-Connected Photovoltaic systems

Rahimi, Ramin; Farhangi, Shahrokh; Farhangi, Babak; Moradi, Gholam Reza; Afshari, Ehsan; Blaabjerg, Frede

doi:10.1109/jestpe.2017.2743527

Cited by 115 publications

(99 citation statements)

References 27 publications

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“…Figure 2F) HERIC ( Figure 2E) H6 ( Figure 2G) inverters can be found in previous studies. 39,[42][43][44][45][46][47] This table can give us the total cost of the converters and the output power value that the maximum of the efficiency is obtained. It means, for example, the efficiency will change in lower or higher power values.…”

Section: Simulation Results and Discussionmentioning

confidence: 99%

“…Many of the topologies have been proposed for this case, but because of the high cost and low efficiency of the transformer, switching inverters are usually preferred in low-power applications. [39][40][41] Normally a DC-DC boost converter is applied to increase the DC voltage at the input side, and then by the inverter, the AC voltage for grid applications is generated. For this case, based on the galvanic connection among the DC and AC parts, a common-mode leakage current I CM is generated.…”

Section: Generation and Elimination Of I C Mmentioning

confidence: 99%

“…As the other approach for the transformer-less inverters that have been presented in the references herein 39,[45][46][47] and shown in Figure 2D-G, both of the inductors L A and L B are available and usually equal. According to Equations 3 and 4, for this state, V dm = 0.…”

Section: Generation and Elimination Of I C Mmentioning

confidence: 99%

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An FPGA‐based switching photovoltaic‐connected inverter topology for leakage current suppression in grid‐connected utilizations

Ghaderi

2020

Circuit Theory & Apps

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This study presents a symmetrical photovoltaic (PV)-connected inverter topology for eliminating the common-state leakage current in grid-connected inverters. A new inverter topology is introduced that minimizes the leakage current, increases efficiency, and is economically viable because it consists of six power switches and two power diodes that, compared with similar ones, consist of the same element numbers. In this inverter, power losses are lower than popular topologies such as H5, H6, and HERIC, and the voltage stresses of the switches are reduced. These features are due to the unique composition of the inverter branches and the location of the switches and diodes and the formation of a suitable freewheeling path for the current. The freewheeling path separates the alternating current (AC) side from the direct current side in the converter and cuts off the PV array leakage current to the AC grid. This will improve network reliability indices and maintain conservation standards. Finally, the content of this method is validated by comparing the proposed inverter with the existing conventional topologies. A prototype has been implemented for the performance analysis of the proposed inverter and results presented.

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Section: Simulation Results and Discussionmentioning

confidence: 99%

Section: Generation and Elimination Of I C Mmentioning

confidence: 99%

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An FPGA‐based switching photovoltaic‐connected inverter topology for leakage current suppression in grid‐connected utilizations

Ghaderi

2020

Circuit Theory & Apps

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“…The objective of such modulation techniques is to avoid the application of zero vectors, which are responsible for generating the highest CMV variations. However, when using such modulation techniques, the overall performance of the converter is degraded in terms of voltage linearity, DC-link current ripple, and THD [24,26,41].…”

Section: Conventional and CMV Mitigation Modulation Techniques For Twmentioning

confidence: 99%

“…(b) H8: The H8 topology ( Figure 5b) has its origin in the single-phase H6 topology. The difference from the traditional VSI is that incorporates two active DC-decoupling switches that are activated when the zero voltage vectors are applied [25,26,41,42]. This topology reduces the CMV to a greater extent than H7, but as it uses more devices, the power losses increase.…”

Section: H8d2 H6d2mentioning

confidence: 99%

Mitigation of Common Mode Voltage Issues in Electric Vehicle Drive Systems by Means of an Alternative AC-Decoupling Power Converter Topology

et al. 2019

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Electric vehicles (EV) are gaining popularity due to current environmental concerns. The electric drive, which is constituted by a power converter and an electric machine, is one of the main elements of the EV. Such machines suffer from common mode voltage (CMV) effects. The CMV introduces leakage currents through the bearings, leading to premature failures and reducing the propulsion system life cycles. As future EV power converters will rely on wide bandgap semiconductors with high switching frequency operation, CMV problems will become more prevalent, making the research on CMV mitigation strategies more relevant. A variety of CMV reduction methods can be found in the scientific literature, such as the inclusion of dedicated filters and the implementation of specific modulation techniques. However, alternative power converter topologies can also be introduced for CMV mitigation. The majority of such power converters for CMV mitigation are single-phase topologies intended for photovoltaic applications; thus, solutions in the form of three-phase topologies that could be applied to EVs are very limited. Considering all these, this paper proposes alternative three-phase topologies that could be exploited in EV applications. Their performance is compared with other existing proposals, providing a clear picture of the available alternatives, emphasizing their merits and drawbacks. From this comprehensive study, the benefits of a novel AC-decoupling topology is demonstrated. Moreover, an adequate modulation technique is also investigated in order to exploit the benefits of this topology while considering a trade-off between CMV mitigation, efficiency, and total harmonic distortion (THD). In order to extend the results of the study close to the real application, the performance of the proposed AC-decoupling topology is simulated using a complete and accurate EV model (including vehicle dynamics and a detailed propulsion system model) by means of state-of-the-art digital real-time simulation.Energies 2019, 12, 3349 2 of 27 the commutations of the power converter devices generate significant high-frequency CMV variations (Figure 1a). As a result, these voltage variations can produce not only high electromagnetic interferences (EMI) [6][7][8], but also shaft voltages (Figure 1b) in the electric machine [9][10][11], producing new capacitive paths [10]. These paths result in high-frequency leakage currents (Figure 1c) circulating through the motor bearings [12][13][14]. The most relevant capacitive paths are depicted in Figure 2, where the most significant bearing currents produced by CMV are the capacitive currents, electrostatic discharge currents, circulating currents, and rotor ground currents [9,13]. As bearings are critical components for the electric machine [10], a number of industrial companies are currently analyzing the degradation problems generated by such bearing currents [15][16][17].Regarding this issue, it is important to remark that although the majority of current industrial solutions rely on silicon-bas...

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An improved quasi Z‐source based H5 inverter with low leakage current for photovoltaic applications

Das

Kirubakaran

Tirumala

et al. 2021

Int Trans Electr Energ Syst

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Grid-connected Single-Stage Boost Inverters (SSBI) are extensively being researched in the area of photovoltaic energy conversion systems. Owing to their single-stage boosting capability, this class of power converters results in higher efficiency and reliability. This power circuit configuration is constituted by two mutually dependent sub-converters, in that a front-end quasi-Z-source (qZS) part is integrated to a back-end multilevel inverter (MLI). The MLI provides the shootthrough state to the qZS, while the qZS provides the pulsating DC input to the MLI. In general, solar photovoltaic inverters suffer from the disadvantage of leakage current that flows from solar panels to the grid/load. This paper introduces a dual quasi-Z-source based multilevel inverter, which achieves the following benefits: (a) five-level output voltage, (b) reactive power capability, (c) shoot-through immunity, (d) continuous input current, and (e) reduced leakage current based on VDE 0126-1-1 standards. In this paper, a modified modulation scheme, which is based on the employment of phase-disposed and level-shifted carrier signals, has been used to reduce the leakage current. To reduce the leakage current further, a passive filter is employed to eliminate high frequency variations across the parasitic capacitance. The working principle of the proposed power converter and the effectiveness of the modulation scheme have been validated with simulation studies in both standalone and the grid-connected mode. Finally, the simulation studies are verified through an experimental prototype of 500 W rating.common mode voltage, leakage current, multilevel inverter, quasi Z-source, shoot-though LIST OF SYMBOLS AND ABBREVIATIONS: V IN , input voltage; V DC , boosted DC link voltage; V O , output voltage; D S , shoot through duty cycle; m, modulation index; V C1 , voltage across capacitor 1; V C2 , voltage across capacitor 2; V CMV , common mode voltage; V CPAR , voltage across parasitic capacitance; i LEAK , leakage current; B, boost factor; i L1 , current through inductor 1; P O , output power; k C1 , ripple across capacitor 1; k C2 , ripple across capacitor 2; k L , ripple through inductor current; VDC , peak DC link voltage; L, inductor; C, capacitor; C f , filter capacitor; L f , filter inductor; CMV, common mode voltage;

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H8 Inverter to Reduce Leakage Current in Transformerless Three-Phase Grid-Connected Photovoltaic systems

Cited by 115 publications

References 27 publications

An FPGA‐based switching photovoltaic‐connected inverter topology for leakage current suppression in grid‐connected utilizations

An FPGA‐based switching photovoltaic‐connected inverter topology for leakage current suppression in grid‐connected utilizations

Mitigation of Common Mode Voltage Issues in Electric Vehicle Drive Systems by Means of an Alternative AC-Decoupling Power Converter Topology

An improved quasi Z‐source based H5 inverter with low leakage current for photovoltaic applications

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