• 전기전자학회논문지
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• 제23권1호
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• pp.143-150
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• 2019

Back-to Back HVDC 방식을 사용한 비동기 계통연계 기술은 고조파 발생, 높은 비용 및 낮은 확장성의 문제를 가지고 있으며, 이러한 문제를 해결하기 위하여 회전형 변압기를 이용한 비동기 계통 연계 기술에 대한 연구가 활발히 진행되고 있다. 그러나 회전형 변압기의 인덕턴스 성분으로 인한 무효전력이 발생되고 별도의 무효전력 보상설비의 추가 설치에 대한 문제가 필연적으로 발생된다. 따라서 본 논문에서는 회전형 변압기를 사용한 비동기 계통 연계 시스템의 필수요소인 정류용 AC-DC 컨버터를 유효전력 공급뿐만 아니라 무효전력을 보상할 수 있도록 설계함으로서 기존의 회전형 변압기의 무효전력 보상 문제를 해결하고자 하며, 제안된 방식은 시뮬레이션을 통해 성능을 검증하였다.

• 전력전자학회논문지
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• 제19권5호
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• pp.407-414
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• 2014

This study proposes a control design for the grid output current and for reducing the neutral-point voltage oscillation through the small-signal modeling of the three-phase grid connected with a three-level neutral-point-clamped (NPC) inverter with LCL filter. The three-level NPC inverter presents an inherent problem: the neutral-point voltage fluctuation caused by the neutral-point current flowing in or out from the neutral point. The small signal modeling consists of averaging, dq0 transformation, perturbing, and linearizing steps performed on a three-phase grid connected to a three-level NPC inverter with LCL filter. The proposed method controls both the grid output and neutral-point currents at every switching period and reduces the neutral-point voltage oscillation. The validity of the proposed method is verified through simulation and experiment.

• 전기전자학회논문지
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• 제24권3호
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• pp.877-882
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• 2020

본 논문에서는 계통연계형 인버터(Grid-connected inverter, GCI) 시스템을 위한 전류 제어 방법들의 성능 비교 연구를 제시한다. GCI 시스템을 위해 다양한 전류 제어 방법이 개발되었으며 각 제어기마다 장점과 한계를 가지고 있다. 본 논문에서는 GCI 전류 제어기들의 정상 상태 및 과도 상태에서의 동적 성능을 비교 분석한다. 제안한 전향보상기법(Command feedforward control, CFFC) 및 외란제거제어(Disturbance rejection control, DRC)가 모든 GCI 전류 제어기에 적용 전과 후의 성능을 비교 분석하였다. 제안된 CFFC와 DRC 제어 알고리즘을 주파수 영역에서 분석하고 성능 검증을 위해 각 GCI 전류 제어 방법들의 시뮬레이션 및 실험 모델을 개발하였다.

• Journal of Power Electronics
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• 제16권6호
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• pp.2306-2314
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• 2016

Design and implementation of a low cost grid-connected 5kVA solar photovoltaic (PV) system is proposed in this paper. Since the inverter is a major component of the PV system, the B4 inverter used in this paper reduces the total cost of the PV system. In order to eliminate the massive transformer, the PV system is connected to the grid through IGBT switches. In addition to injection of active power into the grid, the B4 inverter can compensate reactive power and reduce harmonics of the nonlinear loads. A TMS320F28335 DSP processor is used for effective control of the B4 inverter. Various features of this processor enable the implementation of the necessary control algorithms. As a first step, the PV system is simulated and evaluated in Matlab/Simulink. In the second step, hardware circuits are designed and implemented based on the simulation results. The operation of the PV system has been evaluated under balanced, unbalanced, linear and nonlinear loads which proves its accuracy and efficiency.

• 전기학회논문지
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• 제65권12호
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• pp.2251-2261
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• 2016

The use of renewable energy sources and energy storage systems is increasing due to new policies in the energy industries. However, the increase in distributed generation hinders the reliability of power systems. In order to stabilize power systems, a virtual power plant has been proposed as a novel power grid management system. The virtual power plant plays includes different distributed energy resources and energy storage systems. We define a core virtual power plant technology related to demand response and ancillary service for the cases of Korea, America, and Europe. We also suggest applications of the proposed virtual power plant to the vehicle-to-grid market for restructuring national power industries in Korea.

• 전력전자학회논문지
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• 제25권5호
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• pp.358-368
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• 2020

Grid-connected inverters (GCIs) based on renewable energy sources play an important role in enhancing the sustainability of a society. Harmonic standards, such as IEEE 519 and P1547, which require the total harmonic distortion (THD) of the output current to be less than 5%, should be satisfied when GCIs are connected to a grid. However, achieving a current THD of less than 5% is difficult for GCIs with an output filter under a distorted grid condition. In this study, a novel harmonic compensation method that uses a digital lock-in amplifier (DLA) is proposed to eliminate harmonics effectively at the output of GCIs. Accurate information regarding harmonics can be obtained due to the outstanding performance of DLA, and such information is used to eliminate harmonics with a simple proportional-integral controller in a feedforward manner. The validity of the proposed method is verified through experiments with a 5 kW single-phase GCI connected to a real grid.

• 조명전기설비학회논문지
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• 제28권6호
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• pp.45-51
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• 2014

Synchronous generators and induction generators are mainly used in hydroelectric power generation. Synchronous generator is mainly applied to large hydroelectric plants but induction generator is applied to the small hydro power plants. Stability of induction generator is slightly less than the synchronous generator. However, induction generator has many advantages rather than a synchronous generator in terms of price and maintenance. So Induction generator is used primarily in small hydroelectric power station less than 1,000kW recently. Squirrel cage induction generator generates a high inrush current at the grid-connection. This high inrush current causes a voltage drop on the grid. In order to reduce the voltage drop and to analyze the power flow, the analysis for operating characteristics of the induction generator should be reviewed in advance. In this study, we analyzed the voltage drop and power flow analysis when a 1500kW induction generator is connected to the grid. The voltage drop is slightly higher than the acceptable range of distributed power supply voltage and the power flow of the generator is performed well.

• International Journal of Computer Science & Network Security
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• 제22권4호
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• pp.1-12
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• 2022

In order to overcome the power fluctuation issues in photovoltaic (PV) smart grid-connected systems and the inverter nonlinearity model problem, an adaptive backstepping command-filter and a double second order generalized Integrators (DSOGI) controller are designed in order to tune the AC current and the DC-link voltage from the DC side. Firstly, we propose to present the filter mathematical model throughout the PV system, at that juncture the backstepping control law is applied in order to control it, Moreover the command filter is bounded to the controller aiming to exclude the backstepping controller differential increase. Additionally, The adaptive law uses Lyapunov stability criterion. Its task is to estimate the uncertain parameters in the smart grid-connected inverter. A DSOGI is added to stabilize the grid currents and eliminate undesirable harmonics meanwhile feeding maximum power generated from PV to the point of common coupling (PCC). Then, guaranteeing a dynamic effective response even under very unbalanced loads and/or intermittent climate changes. Finally, the simulation results will be established using MATLAB/SIMULINK proving that the presented approach can control surely the smart grid-connected system.

• Ocean Systems Engineering
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• 제14권1호
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• pp.17-52
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• 2024

In this paper, the authors explore the modeling and control of a point absorber wave energy converter, which is connected to the electric grid via a power converter that is based on a linear permanent magnet synchronous generator (LPMSG). The device utilizes a buoyant mechanism to convert the energy of ocean waves into electrical power, and the LPMSG-based power converter is utilized to change the variable frequency and voltage output from the wave energy converter to a fixed frequency and voltage suitable for the electric grid. The article concentrates on the creation of a predictive control system that regulates the speed, voltage, and current of the LPMSG, and the modeling of the system to simulate its behavior and optimize its design. The predictive model control is created to guarantee maximum energy output and stable grid connection, using Matlab Simulink to validate the proposed strategy, including control side generator and predictive current grid-side converter loops.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 춘계학술대회 논문집 전기설비전문위원
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• pp.140-147
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• 2004

등간격 접지Grid의 설계에서는 대부분의 전류가 외곽접지도체로 누설되어 Grid 구석 접촉전압이 중심 접촉전압 보다 높아지는 문제점이 있다. 비등간격 접지Grid의 설계는 이러한 문제점을 극복할 수 있으나 적절한 비등간격 접지Grid의 설계방법이나 간격결정 방법은 논의되고 있지 않다. 따라서, 본 논문에서는 비등간격 접지Grid의 장점, 수식, 최적의 간격비율을 제시한다.