A Novel Scalar PWM Method to Reduce Leakage Current in Three-Phase Two-Level Transformerless Grid-Connected VSIs

Xu, Junzhong; Han, Jingwen; Wang, Yong; Habib, Salman; Tang, Houjun

doi:10.1109/tie.2019.2920597

Cited by 37 publications

(29 citation statements)

References 25 publications

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“…Therefore, the transformerless PV inverters are promising and attractive in industrial and academic fields [21]. However, due to the lack of galvanic isolation, high-frequency common-mode voltage (CMV) cause undesirable leakage current resulting in output-current distortion and safety trouble [22]. The leakage current depends mainly on the topology and the modulation strategy used.…”

Section: Dc/ac Convertermentioning

confidence: 99%

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

et al. 2020

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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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Section: Dc/ac Convertermentioning

confidence: 99%

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

et al. 2020

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“…Various topologies such as H7, CH7, H9 etc. for the grid-tied SECS array system are reported in the literature [14][15][16]. Various modulation techniques [16][17][18] are reported for the aforementioned topologies, which are compelled to compromise with the modulation index and thereby the performance of the system.…”

Section: Introductionmentioning

confidence: 99%

“…for the grid-tied SECS array system are reported in the literature [14][15][16]. Various modulation techniques [16][17][18] are reported for the aforementioned topologies, which are compelled to compromise with the modulation index and thereby the performance of the system. To attenuate the leakage current [16][17][18], the additional components are used to decouple the SECS from the distribution grid.…”

Section: Introductionmentioning

confidence: 99%

“…Various modulation techniques [16][17][18] are reported for the aforementioned topologies, which are compelled to compromise with the modulation index and thereby the performance of the system. To attenuate the leakage current [16][17][18], the additional components are used to decouple the SECS from the distribution grid. For the aforementioned SECS, the PQ of the grid is deteriorated with the existence of non-linear loads.…”

Section: Introductionmentioning

confidence: 99%

“…The H8 topology for SECS is presented in [20] to improve the PQ issues by providing reactive power at a CCP at the event of unbalancing grid voltages. However, the PQ amelioration in the presence of non-linear load is still unaddressed in the literature [14][15][16][17][18][19][20][21][22][23]. To address the harmonic compensation with the existence of non-linear loads, the multiple cascaded voltage control loops are incorporated in the algorithm to provide harmonic compensation in [24][25][26][27] to improve the PQ of the grid.…”

Section: Introductionmentioning

confidence: 99%

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This work presents a generalised integrator-based control algorithm for power quality (PQ) amelioration of the grid in the presence of non-linear load enabling leakage current suppression feature. Owing to the presence of stray capacitance between solar photovoltaic (PV) array and the ground, the variation in common-mode voltage across stray capacitance leads to potential safety issues, electromagnetic interference, and distortion into the injected grid currents. Furthermore, the PQ of the grid is highly deteriorated under the existence of non-linear loads. To solve the aforementioned issues, the harmonic compensation controller is presented herein to ensure the unity power factor operation, harmonic compensation, leakage current suppression using the grid-connected solar PV array system. Simulated results show the effectiveness of the control strategy under various operating scenario. In contrast to the state-of-the-art techniques, the grid currents are attained sinusoidal and balanced even in the presence of unbalanced non-linear load. Furthermore, the leakage current is suppressed within 300 mA as per the VDE-00126-01 standard. The comparative performance explicitly validates the effectiveness of the presented harmonic compensating strategy over the conventional schemes. Test results manifest the response of the solar PV array system for various operating conditions and follows the revised IEEE-519-2014 sand VDE-00126-01 standards.

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Summary The aim of the paper is to provide seamless transition between the grid connected to an islanded mode and vice versa by switching the control of the load connected VSC (LCVSC) ensuring uninterruptable power supply. In the grid connected mode, a TOQSG (third‐order quadrature signal Generator) based method is applied for power quality improvement at the grid. During synchronization, the LCVSC adapts the phase and frequency of the grid voltage for seamless transition. The paper presents a smart microgrid, which manages the mode of operations and generation of reference signals for the smooth operation. The proposed approach is validated through test results. The grid current and CCP voltage distortion are as per the IEEE‐519 and the IEEE‐1547 standards.

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A Novel Scalar PWM Method to Reduce Leakage Current in Three-Phase Two-Level Transformerless Grid-Connected VSIs

Cited by 37 publications

References 25 publications

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

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

Leakage current alleviation in solar energy conversion system enabling power quality improvement

Robust control for seamless operation of wind‐BES microgrid

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