• Title/Summary/Keyword: Power smoothing

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Smoothing Output Power Variations of Isolated Utility Connected Multiple PV Systems by Coordinated Control

  • Datta, Manoj;Senjyu, Tomonobu;Yona, Atsushi;Sekine, Hideomi;Funabashi, Toshihisa
    • Journal of Power Electronics
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    • v.9 no.2
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    • pp.320-333
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    • 2009
  • A Photovoltaic (PV) system's power output varies with the change of climate. Frequency deviations, tie line voltage swings are caused by the varying PV power when large PV power from several PV systems is fed in the utility. In this paper, to overcome these problems, a simple coordinated control method for smoothing the variations of combined PV power from multiple PV systems is proposed. Here, output power command is formed in two steps: central and local. Fuzzy control is used to produce the central smoothing output power command considering insolation, variance of insolation and absolute average of frequency deviation. In local step, a simple coordination is kept between the central power command and the local power commands by producing a common tuning factor. Power converters are used to achieve the same output power as local command power employing PI control law for each of the PV generation systems. The proposed method is compared with the method where conventional Maximum Power Point Tracking (MPPT) control is used for each of the PV systems. Simulation results show that the proposed method is effective for smoothing the output power variations and feasible to reduce the frequency deviations of the power utility.

An Edge-Based Algorithm for Discontinuity Adaptive Image Smoothing (에지기반의 불연속 경계적응 영상 평활화 알고리즘)

  • 강동중;권인소
    • 제어로봇시스템학회:학술대회논문집
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    • 2000.10a
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    • pp.273-273
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    • 2000
  • We present a new scheme to increase the performance of edge-preserving image smoothing from the parameter tuning of a Markov random field (MRF) function. The method is based on automatic control of the image smoothing-strength in MRF model ing in which an introduced parameter function is based on control of enforcing power of a discontinuity-adaptive Markov function and edge magnitude resulted from discontinuities of image intensity. Without any binary decision for the edge magnitude, adaptive control of the enforcing power with the full edge magnitude could improve the performance of discontinuity-preserving image smoothing.

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Improved Frequency Mitigation of a Variable-Speed Wind Turbine (개선된 가변속 풍력발전기의 주파수 평활화)

  • Li, Mingguang;Yang, Dejian;Kang, Yong Cheol;Hong, Junhee
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.67 no.6
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    • pp.695-701
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    • 2018
  • For a power grid that has a high wind penetration level, when wind speeds are continuously fluctuating, the maximum power point tracking (MPPT) operation of a variable-speed wind turbine (VSWT) causes the significant output power fluctuation of a VSWT, thereby significantly fluctuating the system frequency. In this paper, an improved power-smoothing scheme of a VSWT is presented that significantly mitigates the frequency fluctuation caused by varying wind speeds. The proposed scheme employs an additional control loop based on the frequency deviation that operates in combination with the MPPT control loop. To improve the power-smoothing capability of a VSWT in the over-frequency section (OFS), the control gain of the additional loop, which is set to be inversely proportional to the rotor speed, is proposed. In contrast, the control gain in the under-frequency section is set to be proportional to the rotor speed to improve the power-smoothing capability while avoiding over-deceleration of the rotor speed of a VSWT. The proposed scheme significantly improves the performance of the power-smoothing capability in the OFS, thereby smoothing the frequency fluctuation. The results clearly demonstrate that the proposed scheme significantly mitigates the frequency fluctuation by employing the different control gain for the OFS under various wind penetration scenarios.

Power Smoothing of a Variable-Speed Wind Turbine Generator Based on the Rotor Speed-Dependent Gain (회전자 속도에 따라 변하는 게인에 기반한 가변속 풍력발전기 출력 평활화)

  • Kim, Yeonhee;Kang, Yong Cheol
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.65 no.4
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    • pp.533-538
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    • 2016
  • In a power grid that has a high penetration of wind power, the highly-fluctuating output power of wind turbine generators (WTGs) adversely impacts the power quality in terms of the system frequency. This paper proposes a power smoothing scheme of a variable-speed WTG that can smooth its fluctuating output power caused by varying wind speeds, thereby improving system frequency regulation. To achieve this, an additional loop relying on the frequency deviation that operates in association with the maximum power point tracking control loop, is proposed; its control gain is modified with the rotor speed. For a low rotor speed, to ensure the stable operation of a WTG, the gain is set to be proportional to the square of the rotor speed. For a high rotor speed, to improve the power smoothing capability, the control gain is set to be proportional to the cube of the rotor speed. The performance of the proposed scheme is investigated under varying wind speeds for the IEEE 14-bus system using an EMTP-RV simulator. The simulation results indicate that the proposed scheme can mitigate the output power fluctuation of WTGs caused by varying wind speeds by adjusting the control gain depending on the rotor speed, thereby supporting system frequency regulation.

Active and Reactive Power Control of ESS in Distribution System for Improvement of Power Smoothing Control

  • Shin, Seong-Su;Oh, Joon-Seok;Jang, Su-Hyeong;Cha, Jae-Hun;Kim, Jae-Eon
    • Journal of Electrical Engineering and Technology
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    • v.12 no.3
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    • pp.1007-1015
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    • 2017
  • This paper proposes a new control technique of energy storage system (ESS) for smoothing the active power of renewable energy sources (RES) such as photovoltaic and wind turbine generation. As the penetration of RES into grid increases, it is difficult to maintain the permissible level of power quality, that is, voltage and frequency fluctuation in power systems. To solve this problem, ESS control methods using low pass filter (LPF) have been proposed for mitigating the fluctuation of RES output. However, those have a lot of drawbacks which need to be supplemented. Hence, this paper presents the improved active power control with additional reactive power control for maintaining power quality properly. The proposed method minimizes the capacity of ESS to be required for smoothing RES output fluctuation through mitigation of phase delay problem in LPF. In addition, the voltage regulation improves by using additional reactive power control. The proposed method was verified through simulation analysis using PSCAD/EMTDC.

The Forecasting Power Energy Demand by Applying Time Dependent Sensitivity between Temperature and Power Consumption (시간대별 기온과 전력 사용량의 민감도를 적용한 전력 에너지 수요 예측)

  • Kim, Jinho;Lee, Chang-Yong
    • Journal of Korean Society of Industrial and Systems Engineering
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    • v.42 no.1
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    • pp.129-136
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    • 2019
  • In this study, we proposed a model for forecasting power energy demand by investigating how outside temperature at a given time affected power consumption and. To this end, we analyzed the time series of power consumption in terms of the power spectrum and found the periodicities of one day and one week. With these periodicities, we investigated two time series of temperature and power consumption, and found, for a given hour, an approximate linear relation between temperature and power consumption. We adopted an exponential smoothing model to examine the effect of the linearity in forecasting the power demand. In particular, we adjusted the exponential smoothing model by using the variation of power consumption due to temperature change. In this way, the proposed model became a mixture of a time series model and a regression model. We demonstrated that the adjusted model outperformed the exponential smoothing model alone in terms of the mean relative percentage error and the root mean square error in the range of 3%~8% and 4kWh~27kWh, respectively. The results of this study can be used to the energy management system in terms of the effective control of the cross usage of the electric energy together with the outside temperature.

Optimal Coefficient Selection of Exponential Smoothing Model in Short Term Load Forecasting on Weekdays (평일 단기전력수요 예측을 위한 최적의 지수평활화 모델 계수 선정)

  • Song, Kyung-Bin;Kwon, Oh-Sung;Park, Jeong-Do
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.62 no.2
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    • pp.149-154
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    • 2013
  • Short term load forecasting for electric power demand is essential for stable power system operation and efficient power market operation. High accuracy of the short term load forecasting can keep the power system more stable and save the power market operation cost. We propose an optimal coefficient selection method for exponential smoothing model in short term load forecasting on weekdays. In order to find the optimal coefficient of exponential smoothing model, load forecasting errors are minimized for actual electric load demand data of last three years. The proposed method are verified by case studies for last three years from 2009 to 2011. The results of case studies show that the average percentage errors of the proposed load forecasting method are improved comparing with errors of the previous methods.

Design of Battery System for Smoothing Wind Power Variations in Power System based on Frequency Response Analysis

  • Nakajima, Kyouhei;Umemura, Atsushi;Takahashi, Rion;Tamura, Junji
    • Journal of international Conference on Electrical Machines and Systems
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    • v.2 no.3
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    • pp.342-348
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    • 2013
  • As a number of wind power generation systems have been installed in power systems in the world, frequency fluctuations due to output power variations from wind farms have become a serious problem. Battery systems have been studied for smoothing the output variations and decreasing the resulting frequency fluctuations. Among these studies, efficient design of battery systems is one of the most important subjects from a point of view of cost. This paper presents a comparative analysis of the smoothing effect between the conventional moving average method and a new method based on frequency response analysis.

Smoothing Filter Design Applying a Parameter of a Homo-polar Generator (단극발전기의 내부 인자를 적용한 평활필터 설계)

  • Kim, In-Soo;Seong, Se-Jin
    • The Transactions of the Korean Institute of Power Electronics
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    • v.12 no.5
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    • pp.409-415
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    • 2007
  • For satisfying a recommended value of the quality factor which is one of the important elements in a filter design, a new design method of smoothing filter using an internal parameter of a homopolar generator is proposed. The method increases the efficiency and minimizes the size of the smoothing filter by removing the damping resistor. By considering the resonant frequency as well as the quality factor, the new method can improve the stability of the system which has high boosting converters with negative resistance characteristics.

A Development of Ethernet-Based Remote Diagnosis System for DC Voltage Smoothing Capacitor using DSP (DSP를 적용한 전력용 DC 평활 커패시터의 이더넷 원격 고장진단시스템 개발)

  • Shon, Jin-Geun
    • The Transactions of the Korean Institute of Electrical Engineers P
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    • v.60 no.2
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    • pp.94-98
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    • 2011
  • Electrolytic power capacitors today form essential components for virtually any power electronic system such as DC/DC converter or UPS. Frequently, electrolytic capacitors for DC link voltage smoothing are the key components which determine the life cycle of the whole unit and often are responsible for converter breakdown failures. In this paper, ethernet-based remote diagnosis system for DC voltage smoothing capacitor using DSP control board is developed. To estimate the status of the capacitor, the equivalent series resistor(ESR) of the component has to be determined. The ESR detection scheme is based on the determination of the capacitor ripple power losses calculated from DC link voltage/current measurement. Experimental results show the veridity and reliability of the proposed ethernet-based remote on-line capacitor diagnosis system.