• Title, Summary, Keyword: LCL-filter

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Modeling and Control of a Grid Connected VSI using a Delta Connected LCL Filter ($\Delta$-결선 LCL 필터를 사용하는 삼상 계통 연계 인버터의 모델링과 제어)

  • Lee, Sang-In;Lee, Kui-Jun;Hyun, Dong-Seok
    • The Transactions of the Korean Institute of Power Electronics
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    • v.14 no.1
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    • pp.1-7
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    • 2009
  • There are two ways to connect an LCL filter in a grid-connected VSI. A wye connected LCL filter is general way, and the other is a delta connected LCL filter. While a model of a system with a wye connected LCL filter is calculated, a model of a system with a delta connected LCL filter is not formulated. Thus, we propose a mathematical model of a system with a delta connected LCL filter. Also, a comparative study of capacitor current harmonics of a delta connected LCL filter and a wye connected LCL filter is included. Experimental results exhibit that it is advantageous to control grid currents for a system with a delta connected LCL filter.

Optimized LCL filter Design Method of Utility Interactive Inverter (계통연계형 인버터의 LCL필터 최적 설계기법)

  • Jung, Sang-Hyuk;Choi, Se-Wan
    • The Transactions of the Korean Institute of Power Electronics
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    • v.18 no.1
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    • pp.103-109
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    • 2013
  • The conventional LCL filter design method of the utility interactive inverter considers only harmonics attenuation of the current injected to the grid. However, in case of utility-interactive inverter with critical load the voltage quality of the critical load should also be considered for LCL filter design. Also, considering cost and volume of LCL filters. it is important to have minimum values of inductance and capacitance as far as the harmonic standards are satisfied. In this paper a LCL filter design method is proposed to satisfy not only the harmonic standards of the grid current during the grid-connected mode but the voltage quality of the critical load during grid-connected mode and stand-alone mode. With the proposed method optimized values of LCL filters could be obtained by applying weighting factor to voltage ripple across the critical load, inductor volume, amount of reactive current and system bandwidth.

Active Damping Characteristics on Virtual Series Resistances of LCL Filter for Three-phase Grid-connected Inverter (인덕터 내부저항을 고려한 LCL 필터의 능동댐핑 특성)

  • Kim, Yong-Jung;Kim, Hyosung
    • The Transactions of the Korean Institute of Power Electronics
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    • v.21 no.1
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    • pp.88-93
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    • 2016
  • LCL filters are widely used in high-order harmonics attenuation of output currents in grid-connected inverters. However, output currents of grid-connected inverters with LCL filters can become unstable because of the resonance of the filters. Given that the characteristics of output currents in inverters mostly depend on filter performance, the exact analysis of filters by considering parasitic components is necessary for both harmonics attenuation and current control. LCL filters have three or four parasitic components: the series and/or parallel resistance of the filter capacitor and the series resistance of the two filter inductors. Most studies on LCL filters have focused on the parasitic components of the filter capacitor. Although several studies have addressed the parasitic components of the filter inductor at the inverter side, no study has yet investigated the concurrent effects of series resistance in both filter inductors in detail. This paper analyzes LCL filters by considering series resistance in both filter inductors; it proposes an active damping method based on the virtual series resistance of LCL filters. The performance of the proposed active damping is then verified through both simulation and experiment using Hardware-in-the-Loop Simulator(HILS).

Design of an LCL Filter employing a Symmetric Geometry and its Control in Grid-connected Inverter Applications (계통연계형 인버터에서 대칭 구조를 갖는 LCL 필터 설계 및 제어)

  • Lee, Kui-Jun;Park, Nam-Ju;Hyun, Dong-Seok
    • Proceedings of the KIPE Conference
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    • pp.250-252
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    • 2008
  • An inductor-capacitor-inductor (LCL) filter are widely adapted in grid-connected inverter applications. In this paper, the harmonic attenuations of the LCL filter are quantitatively analyzed, and then the design optimization of two inductance values, which are related on a cost and a size, is illustrated. Based on the design optimization, the LCL filter employing a Symmetric Geometry is proposed. Through the equivalent circuit analysis of the proposed LCL filter, the operating characteristics and validity are presented in detail. In addition, simple proportional-integral (PI) current controller suitable for the LCL Filter is designed to mitigate the resonance problem. From simulation results, it is seen that the proposed LCL filter and control method have a sufficient attenuation and stability for the high frequency distortions and load variations.

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Design of Voltage Source PWM Converter with AC Input LCL Filter (교류 입력측 LCL 필터 구조 전압형 PWM 컨버터의 설계)

  • 노재석;최재호
    • The Transactions of the Korean Institute of Power Electronics
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    • v.7 no.5
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    • pp.490-498
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    • 2002
  • In this paper, a design method of LCL filter at the AC input side of a voltage source PWM converter is proposed. Effective method to prevent pollution of the utility caused by high frequency current ripple is to use a AC input LCL filter, The C elements in the filter provide a low impedance path for the high frequency component, preventing them from entering the utility. The resistors In series with the capacitors are used for damping the resonance in the filter The design examples are shown and the validity of the proposed design method is verified through the PSIM simulation.

Design of LCL-filter for Grid-Connected Three-Phase Inverters Using a Discontinuous PWM Method (DPWM 방식을 적용한 3상 계통 연계 인버터의 LCL-필터 설계)

  • Lee, Jung-Rok;Seo, Seung Gyu;Lee, Kyo-Beum
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.65 no.3
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    • pp.419-427
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    • 2016
  • This paper proposes a design method of LCL-filter for a grid-connected three-phase inverter using a discontinuous PWM (DPWM) method. When using a DPWM method, many harmonic voltages are generated in the inverter output compared to a continuous PWM (CPWM) method. Therefore, an optimized grid-connected filter design is required for a DPWM method. The proposed design method provides generalized formula to design accurate LCL-filter without trial and error procedures. An inverter side inductance is designed by analyzing the current ripple injected to the grid. The Optimized parameters of LCL-filter can be designed by analyzing the total harmonic distortion (THD) and the ripple attenuation factor of the output current. The proposed LCL filter design method is demonstrated by simulation and experimental results.

Design of an LCL-Filter for Space Vector PWM in a Grid-Connected System (3상 계통 연계 인버터의 SVPWM을 위한 LCL-필터 설계)

  • Seo, Seung Gyu;Cho, Yongsoo;Lee, Kyo-Beum
    • The Transactions of the Korean Institute of Power Electronics
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    • v.21 no.6
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    • pp.538-541
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    • 2016
  • This paper proposes an LCL-filter design for space vector pulse width modulation (SVM) in grid-connected three-phase inverter systems. Although there are a several studies in progress, the existing methods are erroneous because they do not focus on the other switching methods. This paper presents the design methodology for an LCL-filter that is optimized for SVM switching operations. The design procedure for the LCL-filter is presented step-by-step. The inverter-side inductor was determined by an analysis of the ripple components, mathematically. Based on the reactive power absorption ratio, the filter capacitor was determined. The grid-side inductor was determined by the ripple attenuation factor of the output current. Experimental results verify the validity of the design method for the LCL-filter.

Design of an LCL-Filter for Grid-Connected Three-Level Inverter System (계통 연계형 3-레벨 인버터 시스템을 위한 LCL-필터 설계 방법)

  • Park, Joon Young;Kim, Seok-Min;Seo, SeungGyu;Park, Seong-Soo;Lee, Kyo-Beum
    • Journal of IKEEE
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    • v.21 no.2
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    • pp.105-114
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    • 2017
  • This paper proposes a design method of an LCL-filter for grid-tied three-level inverter systems. The demand for three-phase PWM inverters in applications such as wind or solar power generation systems has been increase in recent years. To reduce harmonic components caused by switching operation, such inverters are connected to the grid via an LCL filter. Although there are research results for designing LCL-filter, the modulation method should be fully considered to make the filter perform desired cancellation ability with minimized size. This paper presents the design methodology for an LCL-filter that is optimized for SVM switching operations. The simulation and experimental results verify the validity of the LCL-filter designed with proposed method in this paper.

Enhanced Startup Diagnostics of LCL Filter for an Active Front-End Converter

  • Agrawal, Neeraj;John, Vinod
    • Journal of Power Electronics
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    • v.18 no.5
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    • pp.1567-1576
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    • 2018
  • The reliability of grid-connected inverters can be improved by algorithms capable of diagnosing faults in LCL filters. A fault diagnostic method during inverter startup is proposed. The proposed method can accurately generate and monitor information on the peak value and the location of the peak frequency component of the step response of a damped LCL filter. To identify faults, the proposed method compares the evaluated response with the response of a healthy higher-order damped LCL filter. The frequency components in the filter voltage response are first analytically obtained in closed form, which yields the expected trends for the filter faults. In the converter controller, the frequency components in the filter voltage response are computed using an appropriately designed fast Fourier transform and compared with healthy LCL response parameters using a finite state machine, which is used to sequence the proposed startup diagnostics. The performance of the proposed method is validated by comparing analytical results with the simulation and experimental results for a three-phase grid-connected inverter with a damped LCL filter.

Optimization of Parameters for LCL Filter of Least Square Method Based Three-phase PWM Converter

  • Zheng, Hong;Liang, Zheng-feng;Li, Meng-shu;Li, Kai
    • Journal of Electrical Engineering and Technology
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    • v.10 no.4
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    • pp.1626-1634
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    • 2015
  • LCL filters are widely used in three-phase PWM converter for its advantages of small volume, low cost and inhibition of high frequency current harmonic. However, it is difficult to optimize its design because its parameters are mutually influenced while the value of each parameter for LCL filter has impacts on the converter's cost and size. In this paper, the target of optimization is to minimize the parameter values of LCL filter, and an optimization method for parameters of LCL filter of three-phase PWM converter based on least square method is proposed. With this method, a quantitative calculation of the harmonic component of the converter’s side phase voltage is performed first, and then the quantitative relationship between phase voltage harmonics and grid phase current harmonics is analyzed. After that, the attenuation requirement of each harmonic is obtained by taking into account the requirements for each harmonic component of grid current. Then according to the optimization objective, the objective function with minimum harmonic attenuation deviation is established, and least squares method is adopted for three-dimensional global searching of parameters for LCL filter. Thus, the designed harmonic attenuation curve approximates the minimum attenuation requirements, and the optimized LCL filter parameters are obtained. Finally, the effectiveness of the method is verified by the experiments.