Reactive Power Control Strategy for Inverter-based Distributed Generation System with a Programmable Limit of the Voltage Variation at PCC

Ji-Hoon Im,San Kang,Seung-Ho Song(송승호),Seung-Ki Jung,Ju-Yeop Choi,Ick Choy 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5

In a grid connected distributed generator, the voltage variation problem at the point of common coupling(PCC) is investigated. This is one of the most frequent power quality issues for the grid connection of large amount of the input power into a weak grid. Through a simplified modeling of the distributed generator and the power network, the magnitude of PCC voltage variation is calculated using the equivalent circuit parameters and the output power of the distributed generator. In addition, the required amount of reactive power which can compensate the voltage variation is presented analytically using a vector diagram method. With the proposed compensation method in a power conditioning system(PCS) for a distributed generation, the PCC voltage variation can be minimized automatically even though the power fluctuation occurs due to the change of input power. The proposed method of the calculation and compensation of the PCC voltage variation is verified by computer simulation and experimental results.

DPLL을 이용한 능동적 단독운전방지를 위한 무효전력변동법

이기옥(Lee Ki-Ok),유병규(Yu Byung-Gu),유권종(Yu Gwon-Jong),최주엽(Choi Ju-Yeop),최익(Choy Ick) 한국태양에너지학회 2008 한국태양에너지학회 논문집 Vol.28 No.2

As the grid-connected photovoltaic power conditioning systems (PVPCS) are installed in many residential areas, these have raised potential problems of network protection on electrical power system. One of the numerous problems is an Islanding phenomenon. There has been an argument that it may be a non-issue in practice because the probability of islanding is extremely low. However, there are three counter-arguments: First, the low probability of islanding is based on the assumption of 100% power matching between the PVPCS and the islanded local loads. In fact, an islanding can be easily formed even without 100% power matching (the power mismatch could be up to 30% if only traditional protections are used, e.g. under/over voltage/frequency). The 30% power-mismatch condition will drastically increase the islanding probability. Second, even with a larger power mismatch, the time for voltage or frequency to deviate sufficiently to cause a trip, plus the time required to execute a trip (particularly if conventional switchgear is required to operate), can easily be greater than the typical re-close time on the distribution circuit. Third, the low-probability argument is based on the study of PVPCS. Especially, if the output power of PVPCS equals to power consumption of local loads, it is very difficult for the PVPCS to sustain the voltage and frequency in an islanding. Unintentional islanding of PVPCS may result in power-quality issues, interference to grid-protection devices, equipment damage, and even personnel safety hazards. Therefore the verification of anti-islanding performance is strongly needed. In this paper, improved RPV method is proposed through considering power quality and anti-islanding capacity of grid-connected single-phase PVPCS in IEEE Std 1547 ("Standard for Interconnecting Distributed Resources to Electric Power Systems"), And the simulation results are verified.

배전 선로에 연계된 다수대의 변동성 재생에너지 발전 시스템의 출력 유효전력 변동에 따른 무효전력 제어를 이용한 전압 변동 보상

이상훈,김수빈,송승호 한국풍력에너지학회 2018 풍력에너지저널 Vol.9 No.4

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.

단독운전방지를 위한 AFD 와 RPV 방식의 비교 분석

바이사(Bayasgalan),이영진(Young-Jin Lee),정병환(Byong-Hwan Jeong),김홍성(Hong-Sung Kim),최규하(Gyu-Ha Choe) 전력전자학회 2008 전력전자학술대회 논문집 Vol.- No.-

To detect islanding mode when the grid is being tripped is a major safety issue in the Utility Interactive Distributed Generation (UIDG) system. In this paper, analytical design method is suggested for AFD & RPV method under IEEE929-2000 recommended islanding test condition. We have discussed that there is a same point. we injected reactive component of the current by AFD & RPV methods, but the current reference generated is other waveform. Possible if amount of reactive components in this methods are same each method, there is happened same rates frequency variation. To verify the validity of the analytical comparison, this paper presents simulation and experimental results from single phase, 3[㎾] inverter for the transformerless UIDG system.

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

Ji-Hoon Im,Seung-Ho Song,San Kang 전력전자학회 2013 JOURNAL OF POWER ELECTRONICS Vol.13 No.5

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.

정궤환을 이용한 무효전력 변동기반의 단독운전 방지 성능 검증

조종민,신창훈,차한주 전력전자학회 2019 전력전자학회 논문지 Vol.23 No.2

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.

Performance of Reactive Power Variation using Positive Feedback for Detecting Unintentional Islanding Operation

Jongmin Jo,Woosik Sim,Hanju Cha 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5

This paper proposed reactive power variation (RPV) strategy using positive feedback (PF) to identify unintentional islanding condition of distributed generations (DGs) and cease the successive operation of them. The concept in this paper uses the relationship between the shift of point of common coupling (PCC) frequency and the injected reactive power after islanding occurrence. The structure of the proposed RPV method has a constant reactive power component and a certain reactive power term due to PF using the frequency deviation between the rated frequency and the measured frequency. When islanding occurs, PF increases continuously the positive or negative reactive power in order to deviate PCC frequency outside over/under threshold levels, where PF reduces significantly detection time. The proposed RPV strategy is verified in experiments through 1.7kW 3-level T-type inverter. Detection times of islanding are measured to 53ms and 150ms in over/under threshold levels, respectively.

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

Im, Ji-Hoon,Song, Seung-Ho,Kang, San The Korean Institute of Power Electronics 2013 JOURNAL OF POWER ELECTRONICS Vol.13 No.5

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.

A Study on Effective Enhancement of Load Power Factor Using the Load Power Factor Sensitivity of Generation Cost

Lee Byung Ha,Kim Jung-Hoon The Korean Institute of Electrical Engineers 2005 KIEE International Transactions on Power Engineeri Vol.a5 No.3

Various problems such as increase of power loss and voltage instability may often occur in the case of low load power factor. The demand of reactive power increases continuously with the growth of active power and restructuring of electric power companies makes the comprehensive management of reactive power a troublesome problem, so that the systematic control of load power factor is required. In this paper, the load power factor sensitivity of generation cost is derived and it is used for effectively determining the locations of reactive power compensation devices and for enhancing the load power factor appropriately. In addition, voltage variation penalty cost is introduced and integrated costs including voltage variation penalty cost are used for determining the value of load power factor from the point of view of economic investment and voltage regulation. It is shown through application to a large-scale power system that the load power factor can be enhanced effectively using the load power factor sensitivity and the integrated cost.

DVR을 이용한 전력품질 개선

김성환(Seong-Hwan Kim) 한국전기전자학회 2021 전기전자학회논문지 Vol.25 No.3

DVR은 배전선로의 전압 변동을 보상하는 장치로 일반적으로 계통의 무효전력 보상, 역률개선 문제를 해결하는 장치와 결합하여 사용된다. 이러한 결합보상기기는 상대적으로 제어가 어렵고 부피가 커지는 단점을 갖는다. 본 논문에서는 DVR의 전력위상제어(Power Angle Contorl)방법을 적용하여 부가적인 보상기기의 결합이 없이 DVR 단독으로 배전선로의 무효전력과 전압변동을 동시에 보상하기 위해 보상 전압의 최대 크기와, 위상, 보상 가능한 무효전력 및 유효전력에 대한 수학적 해석을 수행하였다. 유효전력을 배터리에 충전하고 전압 변동시 저장된 에너지를 공급하기 위한 제어알고리즘을 개발하고 Matlab 시뮬레이션을 통해 결과를 확인하였다. DVR is a device that compensates for voltage fluctuations in distribution lines and is generally used in combination with a device that compensates reactive power and improve power factor. Such a coupling compensator has the disadvantage of being relatively difficult to control and bulky. In this paper, mathematical analysis of the maximum magnitude of the compensation voltage, phase angle, compensable reactive power and active power was performed in order to simultaneously compensate the reactive power and voltage fluctuation of the distribution line by applying the power angle control method of the DVR. A control algorithm for charging active power to the battery and supplying stored energy when the voltage is changed was developed and the results were confirmed through Matlab simulation.