• 제목/요약/키워드: Grid-connected inverter

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Design of LCL Filter through Inductor Optimization Method in Grid-Connected Inverter (계통연계 인버터의 인덕터 최적화 기법을 통한 LCL 필터 설계)

  • Jang, Jae-Ha;Kim, Kyeong-Hwa
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.28 no.11
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    • pp.58-67
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    • 2014
  • A grid-connected inverter used for renewable energy resources produces harmonic components in the switching frequency. To effectively reduce switching harmonic components, several types of filter are generally used in the output stage of the grid-connected inverter. Many research works on LCL filter design have been done to maintain the performance with low cost. However, it is not easy to make the filter design be economical and optimal due to the varying characteristic of magnetic core and redundancy design by experience. In this paper, a design method for a LCL filter is presented through the inductor optimization scheme in view of the size and cost when the inductor is manufactured using the magnetic core. The effectiveness is verified through tests using a 3kW grid-connected inverter by simulations and experiments.

A Seamless and Autonomous Mode Transfer Method of Grid-connected Inverter in Microgrid (마이크로그리드에서 계통연계 인버터의 자율적이며 끊김없는 모드전환 기법)

  • Park, Sung-Youl;Kwon, Min-Ho;Choi, Se-Wan
    • The Transactions of the Korean Institute of Power Electronics
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    • v.24 no.5
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    • pp.349-355
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    • 2019
  • A grid-connected inverter with critical loads should be able to supply a stable voltage to critical loads at mode change and during clearing time while detecting unintentional islanding. This study proposes a mode transfer method for a grid-connected inverter with critical loads. The proposed method, which integrates the grid-connected and islanded mode control loops into one control block, provides an autonomous and seamless mode transfer from the current control to the voltage control. Therefore, the proposed scheme can supply a stable voltage to critical loads at mode change and during clearing time. Experimental results are provided to validate the proposed method.

Grid Voltage Estimation Scheme without Phase Delay in Voltage-sensorless Control of a Grid-connected Inverter (전압센서를 사용하지 않는 계통연계 인버터의 제어 및 위상지연을 개선한 계통전압 추정 기법)

  • Kim, Hyun-Sou;Kim, Kyeong-Hwa
    • The Transactions of the Korean Institute of Power Electronics
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    • v.22 no.1
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    • pp.89-93
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    • 2017
  • This study proposes a grid voltage estimation scheme without a phase delay in the voltage-sensorless control of a grid-connected inverter to enhance its economic feasibility, such as manufacturing cost and system complexity. The proposed scheme estimates grid voltages using a disturbance observer (DOB)-based current controller to control the grid-connected inverter without grid-side voltage sensors. The proposed voltage-sensorless control scheme can be applied successfully to grid-connected inverters, which should be operated with synchronization to the grid, considering the phase angle of the grid can be effectively detected through estimating the grid voltages by DOB. However, a problem associated with the phase delay in estimated grid voltages remains because the DOB has dynamic behavior similar to low-pass filter. Hence, the estimated grid voltages are compensated by a phase lead compensator to overcome the limitation. The effectiveness of the proposed control and estimation schemes is proven through simulations and experiments using a 2 kVA prototype inverter.

Dual Current Control Scheme of a Grid-connected Inverter for Power Quality Improvement in Distributed Generation Systems (분산 전원 시스템의 전력품질 향상을 위한 계통연계 인버터의 이중 전류제어 기법)

  • Kim, Kyeong-Hwa
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.29 no.9
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    • pp.33-41
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    • 2015
  • To improve the power quality of distributed generation (DG) systems even in the presence of distorted grid condition, dual current control scheme of a grid-connected inverter is proposed. The proposed current control scheme is achieved by decomposing the inverter state equations into the fundamental and harmonic components. The derived models are employed to design dual current controllers. The conventional PI decoupling current controller is used in the fundamental model to control the main power flow in DG systems. At the same time, the predictive control is applied in the harmonic model to suppress undesired harmonic currents to zero quickly. To decompose the voltage inputs and state variables into the fundamental and harmonic components, the fourth order band pass filter (BPF) is designed in the discrete-time domain for a digital implementation. For experimental verification, 2kVA prototype of a grid-connected inverter has been constructed using digital signal processor (DSP) TMS320F28335. The effectiveness of the proposed strategy is demonstrated through comparative simulation and experimental results.

The MPPT Control of a Small Wind Power Generation System by Adjusting the DC-Link Voltage of a Grid-connected Inverter (계통 연계형 인버터의 DC-Link 전압 가변을 통한 소형 풍력발전 시스템의 MPPT 제어)

  • Park, Min-Gi;Lee, Joon-Min;Hong, Ju-Hoon;Kim, Young-Seok
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.63 no.10
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    • pp.1402-1411
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    • 2014
  • In this paper, the Maximum Power Point Tracking(MPPT) control of the small scale wind power generation system with a three-phase diode rectifier and the grid-connected inverter is studied. Without the need for the converter circuits to control speed of the generator, it is economical and the structure is simple. Compared with existing systems, it can be to reduce the power semiconductor switches and passive elements, and to implement the MPPT control with only DC-Link voltage control of the grid-connected inverter. In order to allow MPPT control without the characteristic information of the wind turbine, the P&O algorithm is applied, and these are verified by the simulation and experiment.

A Dual Buck Three-Level PV Grid-Connected Inverter

  • Ji, Baojian;Hong, Feng;Wang, Jianhua;Huang, Shengming
    • Journal of Power Electronics
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    • v.15 no.4
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    • pp.910-919
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    • 2015
  • The use of a PV grid-connected inverter with non-isolated topology and without a transformer is good for improving conversion efficiency; however, this inverter has become increasingly complicated for eliminating leakage current. To simplify the complicated architecture of traditional three-level dual buck inverters, a new dual Buck three-level PV grid-connected inverter topology is proposed. In the proposed topology, the voltage on the grounding stray capacitor is clamped by large input capacitors and is equal to half of the bus voltage; thus, leakage current can be eliminated. Unlike in the traditional topology, the current in the proposed topology passes through few elements and does not flow through the body diodes of MOSFET switches, resulting in increased efficiency. Additionally, a multi-loop control method that includes voltage-balancing control is proposed and analyzed. Both simulation and experimental results are demonstrated to verify the proposed structure and control method.

Dead time Compensation of Single-phase Grid-connected Inverter Using SOGI (SOGI를 이용한 단상 계통연계형 인버터의 데드타임 보상)

  • Seong, Ui-Seok;Lee, Jae-Suk;Hwang, Seon-Hwan;Kim, Jang-Mok
    • The Transactions of the Korean Institute of Power Electronics
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    • v.22 no.2
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    • pp.166-174
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    • 2017
  • This study proposes a compensation method for the dead-time effects on a single-phase grid-connected inverter. Dead time should be considered in the pulse-width modulation gating signals to prevent the simultaneous conduction of switching devices, considering that a switching device has a finite switching time. Consequently, the output current of the grid-connected inverter contains odd-numbered harmonics because of the dead time and the nonlinear characteristics of the switching devices. The effects of dead time on output voltage and current are analyzed in this study. A new compensation algorithm based on second-order generalized integrator is also proposed to reduce the dead-time effect. Simulation and experimental results validate the effectiveness of the proposed compensation algorithm.

Novel Control and Design Method for Wide Stability Range of Grid Connected Inverter with LCL Filter (LCL 필터를 사용하는 계통 연계형 인버터의 넓은 안정 영역을 갖는 새로운 제어 및 설계 기법)

  • Park, Kwon-Sik;Seo, Byung-Jun;Kim, Hak-Soo;Nho, Eui-Cheol
    • The Transactions of the Korean Institute of Power Electronics
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    • v.23 no.6
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    • pp.440-445
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    • 2018
  • This study proposes a novel control and design method for a grid-connected inverter with an LCL filter without damping. The current resonance phenomenon must be considered when designing the grid-connected inverter system with an LCL filter. Passive or active damping is used in the inverter system to reduce the resonant current. However, passive damping reduces the efficiency of the system, and active damping methods are complex. If the resonant frequency is in a specific region, then the system will be unstable. This study examines the process of stabilizing the entire region without resonant damping. The validity of the proposed method is verified through simulation and experimentation.

Grid Current Control Scheme at Thee-Phase Grid-Connected Inverter Under Unbalanced and Distorted Grid Voltage Conditions (계통전압 왜곡 및 불평형시 3상 계통연계인버터의 계통전류제어 기법)

  • Tran, Thanh-Vu;Chun, Tae-Won
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.62 no.11
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    • pp.1560-1565
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    • 2013
  • This paper proposes the control method for compensating for unbalanced grid current and reducing a total harmonic distortion (THD) of the grid current at the three-phase grid-connected inverter systems under unbalancd and distorted grid voltage conditions. The THD of the grid current caused by grid voltage harmonics is derived by considering the phase delay and magnitude attenuation due to the hardware low-pass filter (LPF). The Cauchy-Schwarz inequality theory is used in order to search more easily for a minimum point of THD. Both the gain and angle of a compensation voltage at the minimum point of THD of the grid current are derived. The negative-sequence components in the three-phase unbalanced grid voltage are cancelled in order to achieve the balanced grid current. The simulation and experimental results show the validity of the proposed control methods.

The Stack Design Considering The Reactive Power Supply of Grid-Connected Inverter (계통 연계형 인버터의 무효전력 공급을 고려한 Stack 설계)

  • Koh, Kwang-Soo;Oh, Pil-Kyoung;Kim, Hee-Jung;Kim, Young-Min
    • Proceedings of the KIPE Conference
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    • pp.453-454
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    • 2016
  • The ESS(Energy Storage System) connected with distributed generation is drawing attention due to improving the quality load leveling, peak shaving for enhancing reliability of the power grid. The grid-connected inverter makes frequency adjustment to the active power's charge discharge according to the load variation. In addition, the inverter is possible to act as a reactive power compensation device to eliminate harmonic operates as power factor change inhibiting, anti-transient voltage fluctuation, active filter. In this paper, we propose a design method of igbt stack considering the reactive power supply capacity to improve the quality and reliability of the inverter. Moreover, the grid-connected inverter considering the four-quadrant rated operation designed stack and verified the feasibility of the design through a thermal analysis.

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