Effects of modulation techniques on leakage ground currents in a grid‐tied transformerless HB‐NPC inverter

Martinez-Garcia, Juan F.; Martinez‐Rodriguez, Panfilo R.; Escobar, G.; Vázquez-Guzmán, Gerardo; Sosa, José M.; Fernández, A.

doi:10.1049/iet-rpg.2018.5471

Cited by 25 publications

(10 citation statements)

References 23 publications

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“…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%

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

Shah

Singh

2020

IET Renewable Power Generation

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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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Section: Introductionmentioning

confidence: 99%

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

Shah

Singh

2020

IET Renewable Power Generation

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“…Furthermore, in multilevel inverters, the voltage across the switching devices is lower, which implies low electric stress on power semiconductors and a reduction of switching losses, keeping high efficiency. For instance, the five level HB-NPC topology has shown efficiency greater than 96% for photovoltaic applications [5].…”

Section: Introductionmentioning

confidence: 99%

Control Design and Experimental Validation of a HB-NPC as a Shunt Active Power Filter

et al. 2020

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This work presents the design of a control law based on the average model of a shunt active power filter considering an H-bridge neutral point clamped topology and its experimental validation. Therefore, the proposed controller is formed by three control loops, namely current (inner), regulation (outer), and balance control loops. The current loop aims to compensate both the displacement power factor and the harmonic distortion produced by nonlinear loads connected to the point of common coupling. To deal with harmonic current distortion, the current loop involves an adaptive mechanism based on a bank of resonant filters tuned at odd harmonics of the fundamental grid frequency. The regulation and balance loops are aimed to maintain the voltage of the capacitors forming the DC-link at a desired constant level. For this, proportional-integral controllers are designed. The design of all three loops considers the average model of the system. The performance of the proposed multi-loop control law is evaluated through numerical results and real-time experimental implementation, both considering a 2 kW academic benchmark with a constant switching frequency of 7 kHz. In order to provide harmonic distortion, a nonlinear load based on an uncontrolled diode bridge rectifier is considered. Additionally, step-load changes from 0.5 kW to 1 kW are considered for the nonlinear load. As a result, a suitable current tracking, voltage regulation, and balance are observed despite parametric uncertainties, load variations, and harmonic distortion. As a consequence, in steady state, simulation results indicate that the compensated grid current THD is 1.75%; meanwhile, the nonlinear load current THD is 52.5%. Experimental results indicate that the compensated grid current THD is 2.32%; meanwhile, the nonlinear load current THD is 53.8%.

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“…International standards like IEEE 1547, IEC 61727 CDV, German VDE-AR-N 4105, Australian AS4777.2, and so on, set limitations on the maximum allowable dc current injection into the grid [9,14,15]. The CM current can be avoided either by adding a passive component to dampen the resonant circuit or by making a constant CM voltage in inverter topology [11,12]. Addition of a damping element causes for the system complexity and additional losses.…”

Section: Introductionmentioning

confidence: 99%

Improvements to the H5 inverter topology for transformer‐less grid‐photovoltaic interface applications

Datta

Sarker

2020

IET Renewable Power Generation

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Incorporation of transformer in grid-photovoltaic (PV) interfaces makes the systems bulky and expensive, and reduces the system efficiency. Consequently, in recent years, researchers have proposed many transformers-less inverter topologies for grid-PV interface applications. Among them, the H5 topology is one with the simplest structure, least switches, and higher efficiency. However, its ground-leakage current repression property is unsatisfactory due to its asymmetry structure and switch-junction capacitance effects. From the aspect of single-phase transformer-less grid-PV interface applications, this study proposes an improved H5 topology, namely 2D-H5 topology, by incorporating a capacitor divider with a clamp branch consisting of two blocking diodes in the basic H5 structure in order to maintain constant common-mode (CM) voltage. The constant CM voltage will cause no CM (i.e. ground-leakage) current through the stray capacitance between the PV array and the ground. Besides, the proposed topology provides the same differential-mode characteristic as good as in a unipolar modulation full-bridge (H4) inverter for ensuring quality of grid injected power. The proposed topology has been analysed in detail, and verified with satisfactory simulation and experimental results in comparison to the existing transformer-less H5 topology. The proposed improvement enables a reduction in the ground-leakage current in conformity with PV interface standards.

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Effects of modulation techniques on leakage ground currents in a grid‐tied transformerless HB‐NPC inverter

Cited by 25 publications

References 23 publications

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

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

Control Design and Experimental Validation of a HB-NPC as a Shunt Active Power Filter

Improvements to the H5 inverter topology for transformer‐less grid‐photovoltaic interface applications

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