고조파 왜곡 환경에서 향상된 역률 계측 알고리즘 개발

이현우,박영균,이진한,정상현,박철우 대한전자공학회 2016 전자공학회논문지 Vol.53 No.7

We propose a algorithm to calculate power factor of fundamental waveform in an environment where the voltage and current have been distorted by harmonics. In the proposed power factor computation algorithm, voltage and current are converted to rotating DQ reference frame, and power factor is calculated from active power and reactive power. We compare the proposed method with the conventional power factor measurement method as mathematically. In a condition that voltage and current are distorted by harmonics, the proposed method accurately measure the power factor of fundamental wave, and it is confirmed by simulation using MATLAB. If the proposed power factor measurement method is applied to an automatic power factor control system, a power factor compensation performance can be maximized in harmonic distortion environment. As a result, it is possible to reduce electricity prices, reduce line loss, increase load capacity, ensure the transmission margin capacity, and reduce the amount of power generation. 본 논문에서는 고조파로 전압과 전류가 왜곡된 상황에서 정확하게 기본파의 역률을 측정할 수 있는 방법을 제안한다. 제안한 역률 계측 방법에서는 전압과 전류를 DQ회전좌표계로 변환한 후 유효전력과 무효전력을 계산하여 역률값을 구하게 된다. 기존의 역률 계측방법과 제안한 방법을 수식적으로 비교하여 제시하고, 제안한 방법은 전압과 전류 모두 고조파 왜곡된 상황에서도 기본파의 역률을 정확하게 계측할 수 있는 것을 MATLAB을 이용한 모의실험에서 확인한다. 제안한 역률 계측방법을 자동역률제어장치에 적용할 경우 고조파 왜곡 환경에서 역률 보상 성능을 최대화 할 수 있다. 그 결과 수용가에서는 역률 개선을 통한 전기료 감소, 선로손실 감소, 부하 용량 증대 효과가 기대된다. 특히 발전 사업가 측에서는 역률 보상 성능의 향상으로 송전 여유 용량 확보와 발전량 절감이 가능하다.

출력변동에 대응한 유도발전기의 역률 보상 제어

이동주 한국조명.전기설비학회 2023 조명·전기설비학회논문지 Vol.37 No.2

Induction generators are widely used in micro hydroelectric power plants. When the flow rate and the head change in the power plants, it becomes a parameter that changes the output of the induction generator. Induction generator has a low power factor even when operated at rated output with an inductive load. Also, if the induction generator is operated lower than the rated value or its output power is fluctuated, the change in the power factor becomes larger at a lower power factor. Therefore, a power factor compensation device such as a single capacitor or STATCOM is applied for power factor compensation. When the generator output is fluctuated, the converter voltage of STATCOM has the characteristic of fluctuating in conjunction with it. In this study, we propose the constant voltage source control method in STATCOM for power factor correction of induction generator and its feasibility is verified by the simulation in which the performance of power factor compensation by the capacitor, STATCOM without constant voltage control and STATCOM with constant voltage control are simulated and quantitatively compared. As a results, we confirmed that the STATCOM with constant voltage control can improve the power factor of induction generators a little comparing to the single capacitor or STATCOM without constant voltage control even if the generator output is fluctuated.

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.

학술논문 : 통일 후 적정 군사력 규모 산정에 미치는 영향요인 도출 및 중요도에 관한 연구

이기덕 ( Gi Deuk Lee ),이선규 한국군사학회 2015 군사논단 Vol.84 No.-

We know that Unified Korea should maintain optimal size of military force power after two Koreas`` unification. This study addresses "What factors are influencing when we decide the optimal size of military force power after unification in Korean Peninsula?" This paper aims to ‘provide judgement grounds for optimal size of military power’ through researching ‘factors which influence choosing the size of military powers.’ First, the unification processes of separated countries which had similar division history were studied. Second, military integration process was researched in detail. Third, factors considered in history on judging or building military force were examined through existing studies and researches by military scholars. Fourth, "expected factors need to be considered for judging proper military force power of unified Korea" were selected through the courses mentioned above, and as a result, final factors were chosen by experts`` discussion and questionnaire with Delphi technique. Lastly, every single factor was verified and measured by importance through AHP technique. The result is that the importance of five areas in first hierarchy was analyzed as follow: ① international relations/order(30.0%), ② military(25.0%), ③ economic(18.0%), ④ political(14.0%), ⑤ social (13.0%). The result of importance analysis on all the areas and factors from the first and second hierarchy is as follows. The major factors from the top 5 list indicates that ① ROK-US alliance was analyzed the most influential one. Next, ② military policy/strategy, ③ security environment around the Korean Peninsula, ④ S. and N. Korea relations, ⑤ the level of national economic power follow. In conclusion, this study is meaningful because "the factors we should consider deciding the optimal size of military power after two Koreas`` unification" hasn``t been researched. It also categorized 29 factors into five areas to measure the importance of all influential factors and suggest priority. I expect that this study would be helpful for judging the optimal size of military power after two Koreas are unified, and also provide ideas for further research.

유도발전기의 출력 변동시 역률 보상 커패시터의 자기여자에 관한 연구

김종겸,박영진 대한전기학회 2023 전기학회논문지 Vol.72 No.3

Induction generators are widely used in mini- or micro-scale hydroelectric power plants. In the case of hydroelectric power generation in which changes in flow rate and head are large, the operation of the induction generator is often lower than the rated output. An induction generator is an inductive load and has a lagging power factor, and when operated at rated output, the power factor is around 0.8. The utility recommends that the customer compensate for the low power factor. The power factor compensation is planned so that the power factor of the induction generator will be about 0.95 under the condition of operating at the rated capacity. When the output of the induction generator decreases, the reactive power required for magnetization has a low change, but the active power decreases and the power factor is further lowered. At this time, a self-excitation phenomenon in which the reactive power for power factor compensation becomes higher than the reactive power required for magnetization may occur. When the self-excitation phenomenon occurs, electrical stress is provided to the induction generator, so in order to reduce the occurrence probability, the extent to which the generator's output can be operated was analyzed. As a result of the analysis, it was confirmed that the possibility of self-excitation can be reduced if the output of the induction generator is operated not to be less than 60% of the rated value.

A Steady-state Analysis for an Inverter-based DG to Determine the Optimal Capacity of an Inverter and Harmonic Filters

Kim, Young-Jin,Hwang, Pyeong-Ik,Moon, Seung-Il The Korean Institute of Electrical Engineers 2011 The Journal of International Council on Electrical Vol.1 No.1

Electric power quality in power transmission/distribution systems has deteriorated considerably with the increase in the number and the capacity of inverter-based distributed generators (DGs). This is caused by inverters, connecting DGs to conventional power grids, tend to generate harmonic currents and voltages due to the switching operations of their transistors and diodes. Therefore, this paper presents new methods to adopt harmonic filters to an inverter-based DG, considering a system consisting of both an inverter-based DG and harmonic filters. In order to prove that the system proposed in this paper can be used generally, this paper describes the simulation results obtained by using PSCAD/EMTDC: the relationship between the total harmonic distortion (THD) of the output current and the output power of a DG, and the harmonic mitigation ability of passive and active filters. Furthermore, the system is obliged to satisfy the regulations made by Korea Electric Power Corporation (KEPCO). In the regulations, DG power factor needs to be maintained between 0.9 and 1 in a grid-connected mode. Thus, this paper suggests two methods for the system to control its power factor. First, the power factor should be controlled by the DG inverter rather than an active filter because this brings a dramatic decrease in the capacity of the active filter. Second, the DG should absorb reactive power only in the low output power range in order to prevent a useless increase in the inverter capacity. This method is expected to result in a variable power factor of the system according to its output power. With these control methods, the proposed DG system can successfully operate in a grid-connected mode with an optimally-reduced capacity of active harmonic filters and DG inverters while satisfying the regulations in terms of voltage variation, power factor, and THD.

주파수 변화에 강인한 역률 계측 알고리즘 개발 시스템

이현우(Hyun-Woo Lee),이인수(In-Soo Lee),이진한(Jinhan Lee),박영균(Young-Kyun Park),정상현(Sanghyun Joung),박철우(Chul-Woo Park) 한국정보기술학회 2016 한국정보기술학회논문지 Vol.14 No.7

We propose a algorithm to calculate power factor of waveform in an environment where the line frequency has been varied. In the proposed power factor computation algorithm, voltage and current are converted to synchronous DQ reference frame, and power factor is calculated from active power and reactive power. We compare the proposed method with the conventional power factor measurement method as mathematically. If the proposed power factor measurement method is applied to an automatic power factor control system, a power factor compensation performance can be maximized in the line frequency variation environment. Also it is possible to implement a power factor measuring device with low-cost MCU because the proposed method is robust to period calculation error due to limited sampling frequency. As a result, it is possible to reduce of electricity prices, reduce of line loss, increase of load capacity, ensure the transmission margin capacity, and reduce the amount of power generation.

고조파 왜곡 환경에서 향상된 역률 계측 알고리즘 개발

이현우(Hyun-woo Lee),박영균(Young-kyun Park),이진한(Jinhan Lee),정상현(Sanghyun Joung),박철우(Chul-woo Park) 대한전자공학회 2016 전자공학회논문지 Vol.53 No.7

본 논문에서는 고조파로 전압과 전류가 왜곡된 상황에서 정확하게 기본파의 역률을 측정할 수 있는 방법을 제안한다. 제안한 역률 계측 방법에서는 전압과 전류를 DQ회전좌표계로 변환한 후 유효전력과 무효전력을 계산하여 역률값을 구하게 된다. 기존의 역률 계측방법과 제안한 방법을 수식적으로 비교하여 제시하고, 제안한 방법은 전압과 전류 모두 고조파 왜곡된 상황에서도 기본파의 역률을 정확하게 계측할 수 있는 것을 MATLAB을 이용한 모의실험에서 확인한다. 제안한 역률 계측방법을 자동역률제어장치에 적용할 경우 고조파 왜곡 환경에서 역률 보상 성능을 최대화 할 수 있다. 그 결과 수용가에서는 역률 개선을 통한 전기료 감소, 선로손실 감소, 부하 용량 증대 효과가 기대된다. 특히 발전 사업가 측에서는 역률 보상 성능의 향상으로 송전 여유 용량 확보와 발전량 절감이 가능하다. We propose a algorithm to calculate power factor of fundamental waveform in an environment where the voltage and current have been distorted by harmonics. In the proposed power factor computation algorithm, voltage and current are converted to rotating DQ reference frame, and power factor is calculated from active power and reactive power. We compare the proposed method with the conventional power factor measurement method as mathematically. In a condition that voltage and current are distorted by harmonics, the proposed method accurately measure the power factor of fundamental wave, and it is confirmed by simulation using MATLAB. If the proposed power factor measurement method is applied to an automatic power factor control system, a power factor compensation performance can be maximized in harmonic distortion environment. As a result, it is possible to reduce electricity prices, reduce line loss, increase load capacity, ensure the transmission margin capacity, and reduce the amount of power generation.

무효전력 민감도와 부하지속곡선을 활용한 적정 부하역률의 효과적인 산정 기법에 관한 연구

이병하(Byung Ha Lee),황승호(Sung-Ho Hwang) 대한전기학회 2012 전기학회논문지 Vol.61 No.12

In this paper, a methodology to use load duration curve and the reactive power factor sensitivity of generation cost is proposed for analyzing the effects of load power factor effectively. A great deal of cases of power systems are classified into several patterns according to the characteristics using load duration curve, and the overall effects of load power factor are assessed by integrating the analysis results of load power factor in all the patterns. The reactive power sensitivity of generation cost and the integrated costs such as generation cost, investment cost, voltage variation penalty cost and CO2 emission cost are used for determining an appropriate load power factor. A systematic procedure for effective analysis of load power factor is presented. It is shown through the application to the practical power system of KEPCO(Korea Electric Power Corporation)that the effects of load power factor can be analyzed effectively using load duration curve and reactive power factor sensitivity.

정현파 주입 방안 적용에 따른 HAPF용 패시브 필터 설계 방안의 역률 보상 정확성 개선

손진근,박경종,김재철,이현재 대한전기학회 2022 전기학회논문지 P Vol.71 No.4

This paper proposes a method to compensate for the power factor error existing in the passive filter design method for HAPF by applying the sinusoidal wave injection method to the LC design method of the passive filter for HAPF. As the LC design method of the passive filter for HAPF assumes that is 1[p.u], it is necessary to completely compensate the harmonics included in the system to accurately compensate the power factor. This is a result of assuming an ideal case, and in practical terms, harmonics cannot be completely eliminated. Therefore, since is not 1[p.u], an error may occur in reactive power compensation. Accordingly, in this paper, we propose a method to reduce the power factor error by applying the sinusoidal injection method based on the default value used in the LC design method of the passive filter for HAPF for MI. The power factor error that appears when the sinusoidal wave injection method is applied to the LC design method of the passive filter for HAPF was precisely compared and analyzed, and the error and effect were analyzed through simulation. As a result, it was possible to see the result of reducing the error from 0.296 [%], which is the power factor error of the passive design method for HAPF, to about 0.04 [%] by applying the sinusoidal injection method.