• Title/Summary/Keyword: reactive power variation method

Search Result 51, Processing Time 0.027 seconds

Performance Verification of Anti-Islanding of Reactive Power Variation Method using Positive Feedback (정궤환을 이용한 무효전력 변동기반의 단독운전 방지 성능 검증)

  • Jo, Jongmin;Shin, Chang-Hoon;Cha, Hanju
    • The Transactions of the Korean Institute of Power Electronics
    • /
    • v.24 no.2
    • /
    • pp.105-110
    • /
    • 2019
  • This study proposed a reactive power variation (RPV) method equipped with positive feedback (PF) for detecting the islanding operation of distributed generation systems. The proposed RPV consists of the constant reactive power component and a certain reactive power term and uses the frequency deviation between the rated and the measured frequencies. The constant reactive power is injected from distributed generation system and power factor is to 0.9975 in grid-connected operation. PF is activated from generation of the frequency deviation and the injected reactive power is continuously increased due to PF when islanding occurs. Consequently, the increasing reactive power causes the point of common coupling frequency to deviate from the maximum/minimum threshold level. Performance of the proposed RPV is verified in a 1.7 kW T-type inverter, and the detection times are 53 and 150 ms.

Improved Direct Power Control of Shunt Active Power Filter with Minimum Reactive Power Variation and Minimum Apparent Power Variation Approaches

  • Trivedi, Tapankumar;Jadeja, Rajendrasinh;Bhatt, Praghnesh
    • Journal of Electrical Engineering and Technology
    • /
    • v.12 no.3
    • /
    • pp.1124-1136
    • /
    • 2017
  • Direct Power Control technique has become popular in the grid connected Voltage Source Converter (VSC) applications due to its simplicity, direct voltage vector selection and improved dynamic performance. In this paper, a direct method to determine the effect of voltage vector on the instantaneous active and reactive power variations is developed. An alternative Look Up Table is proposed which minimizes the commutations in the converter and results in minimum reactive power variation. The application of suggested table is established for Shunt Active Power Filter (SAPF) application. The Predictive Direct Power Control method, which minimizes apparent power variation, is further investigated to reduce commutations in converters. Both the methods are validated using 2 kVA laboratory prototype of Shunt Active Power Filters (SAPF).

Compensation of Voltage Variation Using Active Power-Dependent Reactive Power Control with Multiple VRE Systems Connected in a Distribution Line (배전 선로에 연계된 다수대의 변동성 재생에너지 발전 시스템의 출력 유효전력 변동에 따른 무효전력 제어를 이용한 전압 변동 보상)

  • Lee, Sang-Hoon;Kim, Soo-Bin;Song, Seung-Ho
    • Journal of Wind Energy
    • /
    • v.9 no.4
    • /
    • pp.47-56
    • /
    • 2018
  • This paper introduces an active power dependent standard characteristic curve, Q(P) to compensate for voltage variations due to the output of distributed generation. This paper presents an efficient control method of grid-connected inverters by comparing and analyzing voltage variation magnitude and line loss according to the compensation method. Voltage variations are caused not only by active power, but also by the change of reactive power flowing in the line. In particular, the system is in a relatively remote place in a coastal area compared with existing power plants, so it is relatively weak and may not be suitable for voltage control. So, since it is very important to keep the voltage below the normal voltage limit within the specified inverter capacity and to minimize line loss due to the reactive power. we describe the active power dependent standard characteristic curve, Q(P) method and verify the magnitude of voltage variation by simulation. Finally, the characteristics of each control method and line loss are compared and analyzed.

Analysis and Compensation of PCC Voltage Variations caused by Wind Turbine Power Fluctuations

  • Im, Ji-Hoon;Song, Seung-Ho;Kang, San
    • Journal of Power Electronics
    • /
    • v.13 no.5
    • /
    • pp.854-860
    • /
    • 2013
  • The voltage variation problem at the point of common coupling (PCC) in a grid-connected wind turbine is investigated. The voltage variation problem is one of the most frequent power quality issues for the grid connection of large amounts of input power in a weak grid. Through the simplified modeling of the wind turbine and power network, the magnitude of PCC voltage variation is calculated by using the equivalent circuit parameters and output power of the wind turbine. The required amount of reactive power that can compensate the voltage variation is also presented analytically by using the vector diagram method. The proposed calculation and compensation method of the PCC voltage variation is verified by computer simulations and experiments.

Active Frequency Drift Method for Islanding Detection Applied to Micro-inverter with Uncontrollable Reactive Power

  • Kwak, Raeho;Lee, June-Hee;Lee, Kyo-Beum
    • Journal of Power Electronics
    • /
    • v.16 no.5
    • /
    • pp.1918-1927
    • /
    • 2016
  • This paper proposes active frequency drift (AFD) as an anti-islanding method applied to micro-inverters with uncontrollable reactive power. When using ordinary inverter topologies, such as full bridge inverters in photovoltaic systems, the islanding phenomenon can be detected with reactive power-based methods, such as reactive power variation. However, when the inverter topology cannot control the reactive power, conventional anti-islanding methods with reactive power cannot be utilized. In this work, the topology used in this paper cannot control the reactive power. Thus, an anti-islanding method that can be used in topologies that cannot control the reactive power is proposed. The conventional anti-islanding method of the topology that cannot control reactive power is introduced and analyzed. Unlike the conventional AFD method, the proposed method extends a zero current interval every predetermined cycle. The proposed method offers certain advantages over conventional AFD methods, such as total harmonic distortion. The proposed method is validated through simulation and experiment.

Realtime Compensation of PCC Voltage Variation by Injection of Required Reactive Power in a Grid Connected Variable Speed Wind Turbine (계통 연계형 가변속 풍력발전기의 무효전력 주입을 통한 PCC 전압 변동량 실시간 보상)

  • Im, Ji-Hoon;Song, Seung-Ho
    • The Transactions of the Korean Institute of Power Electronics
    • /
    • v.15 no.1
    • /
    • pp.69-74
    • /
    • 2010
  • In a grid connected variable speed wind turbine, the PCC voltage and the wind power fluctuate as the wind velocity changed. And this voltage variation is changed due to location of PCC. This paper calculate the value of PCC voltage variation which is proportional to the product of the line impedance from the ideal generator to the PCC and the wind turbine output current. And to reduce this PCC voltage variation, this paper calculate the required reactive power analytically using the vector diagram method. Output reactive current is changed, if the reactive current is limited by inverter capacity or grid code have the margin of voltage variation. If the grid connected inverter is controlled by proposed algorithm, the PCC voltage variation is minimized though the wind turbine output change at random. To verify calculated voltage variation and required reactive power, this paper utilized Matlab and PSCAD/EMTDC simulation and real small wind turbine and power system in Sapsido, island in the Yellow Sea.

Reactive Power P&O Islanding Detection Method using Positive Feedback (Positive Feedback을 이용한 무효전력 P&O 단독운전 검출기법)

  • Lee, Jong-Won;Park, Sung-Youl;Lee, Jae-Yeon;Choi, Se-Wan
    • The Transactions of the Korean Institute of Power Electronics
    • /
    • v.27 no.5
    • /
    • pp.410-416
    • /
    • 2022
  • A grid-connected inverter with critical loads uses mode transfer control to supply stable voltage to the load. An islanding detection method should also be used to quickly detect the grid fault and disconnect the inverter from the grid. However using the existing islanding detection method to detect islanding is difficult due to the small fluctuation of the voltage and frequency of the point of common coupling. This study proposes a reactive power P&O islanding detection method by using the positive feedback technique. The proposed method always injects a small variation of reactive power. When a grid fault occurs, the injected reactive power accelerates the reactive power injection reference. As a result, the reactive power reference value and the sensed reactive power become mismatched, and islanding is detected. Reducing the amount of real-time injected reactive power results in high efficiency and power factor. The simulation and experimental results of a 3 kW single-phase inverter are provided to verify the proposed islanding detection method.

Reactive Power Traceable System based Vulnerable Areas Detection for Reactive Power (무효전력 흐름 추적을 이용한 무효전력 취약지역 판단)

  • Choi, YunHyuk;Bae, MoonSung;Lee, Byongjun
    • The Transactions of The Korean Institute of Electrical Engineers
    • /
    • v.64 no.8
    • /
    • pp.1145-1153
    • /
    • 2015
  • The paper analyzes reactive power flow characteristic in power system by reactive power tracing. In addition, virtual buses are inserted in the algorithm to consider losses of transmission lines, and shunt capacitor treated as a reactive power generator. The results of simulation are analyzed by two points of view. The one is load’s point of view and another is generator’s point of view. Classic purpose of the reactive power tracing consists in the reactive power pricing. However, it is significantly used to select vulnerable area about line outage in this paper. To find the vulnerable area, reactive power tracing variations between pre-contingency and post-contingency are calculated at all load buses. In heavily load area, buses which has highest variation become the most vulnerable bus. This method is applied to the IEEE 39-bus system. It is compared with voltage variation result and VQ-margin to verify its effect.

Performance Improvement of an Anti-Islanding Algorithm using the Variation of Reactive Power with an Improved DFT Method (개선된 DFT을 이용한 무효전력변동 단독운전 검출기법의 성능 개선)

  • Kang, Duk-Hong;Choi, Dae-Keun;Lee, Kyo-Beum
    • The Transactions of the Korean Institute of Power Electronics
    • /
    • v.15 no.3
    • /
    • pp.179-187
    • /
    • 2010
  • This paper proposes a new anti-islanding method for single-phase grid-connected photovoltaic (PV) systems using Goertzel algorithm. The proposed scheme is based on inducing increases or decreases of frequencies of load voltage and current that is in the form of existences or periodical variations of the reactive power components. The frequency detection is needed to apply this power variation method to the grid-connected power converter. The proposed method is able to get a fast detection for anti-islanding without the effect of harmonics and noises. The simulation and experiment results validate the effectiveness of the proposed method.

Analysis of Islanding Detection with Reactive Power Variation Method (RPV 기법의 단독운전 검출에 대한 분석)

  • Park, Gwon-Sik;Seo, Byeong-Jun;Kim, Hak-Soo;Nho, Eui-Cheol
    • Proceedings of the KIPE Conference
    • /
    • 2017.11a
    • /
    • pp.171-172
    • /
    • 2017
  • 본 논문에서는 분산전원의 계통 연계형 시스템에서의 단독운전 검출 방식인 RPV(Reactive Power Variation)기법에 대한 고찰과 주파수 검출 방식을 분석한다. IEEE 929 - 2000에 근거하여 RPV 기법에서의 NDZ에 대하여 살펴보고, PLL(Phase Locked Loop) 기법을 이용한 주파수 검출에 대한 분석 및 설계와 이를 통한 단독운전 검출을 하고자 한다. 시뮬레이션을 통하여 타당성을 검증하였다.

  • PDF