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Kil To Chong - One of the best experts on this subject based on the ideXlab platform.

  • Coordination optimization control of Dc Component and harmonics for grid-connected PV inverters.
    ISA transactions, 2019
    Co-Authors: Bo Long, Wenting Fang, Cheng Zhao, Kil To Chong
    Abstract:

    Abstract Grid-connected inverters (GCIs) have been extensively adopted in distributed renewable energy systems. However, due to the asymmetrical gate-driving signals, imparities of the power semiconductors, and unbalanced grid voltage, etc., the grid current contains Dc Components which are detrimental to the grid. Furthermore, due to the nonlinear loads in the grid, the grid current may also contain harmonics. As a result, power quality of the grid current is degraded. IEEE 1547-2003 has specified the maximum Dc Component and harmonics contents of the grid current. In this paper, a repetitive controller (RC) for Dc Component compensation is put forward at first, then, a Discrete-Fourier-Transformation (DFT)-RC controller is presented for harmonic elimination. Considering Dc Components and harmonics may coexist in GCIs in utility, a coordination optimization control scheme utilizing Weight Factor Distribution Optimization Method (WFDOM) is introduced. The proposed method is realized by adaptively allocating the weight factors for Dc suppression controller and harmonic elimination controller according to their relative deviations. Simulation and experimental results show the feasibility and correctness of the proposed method. The proposed method can applied to high power quality PV power generation system.

  • An Overview of Dc Component Generation, Detection and Suppression for Grid-Connected Converter Systems
    IEEE Access, 2019
    Co-Authors: Bo Long, Lijun Huang, Muheng Zhang, Yong Liao, Kil To Chong
    Abstract:

    Transformerless grid-connected distributed photovoltaic (PV) systems (TGCDPVs) has the merits of high efficiency, small size, and low cost, draws great interest in recent years. However, Direct Current (Dc) injection is a serious issue in TGCDPVS, which degrade its power quality. Some publications have discussed Dc Component generation and suppression methods; however, there are very few systematic reviews on the generation, detection, and suppression of Dc Component in TGCDPVS. For young researchers and designers working in photovoltaic power generation systems, the Dc injection suppression is of great importance. This paper first reviews a number of issues related with Dc Component in TGCDPVs, the Dc current generation and its detriments to the grid are reviewed at first, then, a comprehensive review on the latest Dc detection method are performed, finally, various Dc suppression solutions are given. Comparisons between various Dc Component detection and suppression methods are discussed. In the end, some future suggestions are given. This review shall provide a useful guideline and a clearer vision for researchers to determine the best solution for Dc suppression in their PV product.

  • Mitigation of Dc Components Using Adaptive BP-PID Control in Transformless Three-Phase Grid-Connected Inverters
    Energies, 2018
    Co-Authors: Lijun Huang, Yufei Dai, Kil To Chong
    Abstract:

    Transformerless grid-connected inverters, due to their advantages of high efficiency, small volume and light weight, have been the subject of more research and interest in recent years. Due to the asymmetrical driving signal in pulse width modulation (PWM) caused by time-delay, zero-drift of the current sensors and imparities of the power transistors, output of the grid current contains Dc Component. As a result, power quality of the grid is degraded. In this paper, a Dc (direct current) Component suppression scheme with adaptive back-propagation (BP) neural network proportional-integral-differential (PID) control is proposed for Dc Component minimization. Moreover, sliding-window-double-iteration-method (SWDIM) is utilized for fast Dc Component extraction. Compared with the conventional method, the proposed scheme shows better performance, and the Dc Component can be attenuated to be within 0.5% of the rated current.

Bo Long - One of the best experts on this subject based on the ideXlab platform.

  • Coordination optimization control of Dc Component and harmonics for grid-connected PV inverters.
    ISA transactions, 2019
    Co-Authors: Bo Long, Wenting Fang, Cheng Zhao, Kil To Chong
    Abstract:

    Abstract Grid-connected inverters (GCIs) have been extensively adopted in distributed renewable energy systems. However, due to the asymmetrical gate-driving signals, imparities of the power semiconductors, and unbalanced grid voltage, etc., the grid current contains Dc Components which are detrimental to the grid. Furthermore, due to the nonlinear loads in the grid, the grid current may also contain harmonics. As a result, power quality of the grid current is degraded. IEEE 1547-2003 has specified the maximum Dc Component and harmonics contents of the grid current. In this paper, a repetitive controller (RC) for Dc Component compensation is put forward at first, then, a Discrete-Fourier-Transformation (DFT)-RC controller is presented for harmonic elimination. Considering Dc Components and harmonics may coexist in GCIs in utility, a coordination optimization control scheme utilizing Weight Factor Distribution Optimization Method (WFDOM) is introduced. The proposed method is realized by adaptively allocating the weight factors for Dc suppression controller and harmonic elimination controller according to their relative deviations. Simulation and experimental results show the feasibility and correctness of the proposed method. The proposed method can applied to high power quality PV power generation system.

  • Dc Component Minimization of Transformerless LCL-Type Grid-Connected Inverter with Virtual Capacitors
    2019 Chinese Control Conference (CCC), 2019
    Co-Authors: Wenting Fang, Lijun Huang, Bo Long, Yong Chen
    Abstract:

    Integration of renewable energy (RE) sources, such as wind energy and photovoltaic (PV) energy, to a power network (grid) is usually achieved through an intermediate power electronic inverter. Ideally, the grid connected inverter (GCI) is not expected to inject any form of Dc Components into the grid. However, it may have Dc Component problems in utility, which will impact the overall power quality of the power system and even cause serious problems. To mitigate this problem, the International Grid Certification (such as IEEE Standard 929-2000) stipulates the maximum allowable extent of Dc Component that can be injected into the grid. Thus, various techniques have been proposed to maintain the Dc Component within the stipulated limit, but with different levels of success. This paper proposes a virtual capacitor based Dc current suppression control technique for a three-phase transformerless grid-connected inverter, which has the merits of no-additional power losses, no needs for auxiliary current compensation or detection circuit, and fast implementation speed. In the proposed scheme, the current controller design are performed with the active damping as well as Dc Component mitigation. Furthermore, simulation results are presented to demonstrate the effectiveness of the proposed scheme.

  • An Overview of Dc Component Generation, Detection and Suppression for Grid-Connected Converter Systems
    IEEE Access, 2019
    Co-Authors: Bo Long, Lijun Huang, Muheng Zhang, Yong Liao, Kil To Chong
    Abstract:

    Transformerless grid-connected distributed photovoltaic (PV) systems (TGCDPVs) has the merits of high efficiency, small size, and low cost, draws great interest in recent years. However, Direct Current (Dc) injection is a serious issue in TGCDPVS, which degrade its power quality. Some publications have discussed Dc Component generation and suppression methods; however, there are very few systematic reviews on the generation, detection, and suppression of Dc Component in TGCDPVS. For young researchers and designers working in photovoltaic power generation systems, the Dc injection suppression is of great importance. This paper first reviews a number of issues related with Dc Component in TGCDPVs, the Dc current generation and its detriments to the grid are reviewed at first, then, a comprehensive review on the latest Dc detection method are performed, finally, various Dc suppression solutions are given. Comparisons between various Dc Component detection and suppression methods are discussed. In the end, some future suggestions are given. This review shall provide a useful guideline and a clearer vision for researchers to determine the best solution for Dc suppression in their PV product.

  • A Dc Component Suppression Technique Based on Virtual Capacitors
    2019 IEEE Energy Conversion Congress and Exposition (ECCE), 2019
    Co-Authors: Bo Long, Wenting Fang, Udaya K. Madawala
    Abstract:

    This paper proposes a virtual capacitor based Dc suppression strategy that can be employed by grid converters to mitigate the adverse effect, which caused by Dc Component injected by grid converts. The proposed control concept is described in detail and a model is presented. Both theoretical and experimental results are presented to demonstrate the validity of the proposed concept.

Zheng I - One of the best experts on this subject based on the ideXlab platform.

  • a study on time constant of Dc Component of short circuit current and current zero offset in uhv systems
    Power system technology, 2006
    Co-Authors: Zheng I
    Abstract:

    The authors investigate the transient requirements of AC 1100 kV circuit breakers mainly for the UHV pilot project and future UHV power grid being planned in China. It includes two parts: (A) the transient recovery voltages after circuit breakers interrupt the short-circuit currents or the current is out of phase condition;(B) the time constant of Dc Component of short-circuit currents and current-zero offset. As the second part of the study that focuses on the time constant of Dc Component of short-circuit currents and current-zero offset in UHV systems, based on these results, the suggestions on transient requirements of AC 1100kV circuit breakers such as the time constant of Dc Component in short-circuit currents for UHV circuit breaker testing and so on are presented.

Udaya K. Madawala - One of the best experts on this subject based on the ideXlab platform.

  • A Dc Component Suppression Technique Based on Virtual Capacitors
    2019 IEEE Energy Conversion Congress and Exposition (ECCE), 2019
    Co-Authors: Bo Long, Wenting Fang, Udaya K. Madawala
    Abstract:

    This paper proposes a virtual capacitor based Dc suppression strategy that can be employed by grid converters to mitigate the adverse effect, which caused by Dc Component injected by grid converts. The proposed control concept is described in detail and a model is presented. Both theoretical and experimental results are presented to demonstrate the validity of the proposed concept.

Liu Bei - One of the best experts on this subject based on the ideXlab platform.

  • Analysis on Dc Component in Short-Circuit Current of Power Grid and Its Influence on Breaking Ability of Circuit Breakers
    Power system technology, 2012
    Co-Authors: Liu Bei
    Abstract:

    There are two main Components in short-circuit current of power system,i.e.,the periodical Component and direct current(Dc) Component,however in engineering application there is no special attention paid to the latter.The attenuation of Dc Component of short-circuit current in EHV power transmission network is presented in two aspects,namely simulation and actual recorded fault data,and the influence of Dc Component on breaking ability of circuit breakers being operated.Finally,the breaking ability and making capability of circuit breakers being operated are synthetically evaluated,and following conclusion are obtained: if the breaking ability of circuit breaker is checked by periodical Component in short-circuit current,it is necessary to keep out the margin of breaking ability in the range from 10% to 30% to take possibly existing Dc Component in the fault current to be switched off;as for the circuit breaker being operated in limited operation mode,the breaking ability of circuit breaker to be considered is its rated breaking capacity,but not the making capability.