• Journal of Electrical Engineering and Technology
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• 제8권3호
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• pp.472-477
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• 2013

An internet-based, real-time GPS synchronized wide-area power system frequency monitoring network(FNET) has been monitoring wide-area power system frequency in continuous time in the United States. This paper analyzes the FNET measurement to the verified disturbances in the US eastern interconnected power system and simulates it using the dynamic system model. By comparing the frequency measurements with its simulation results to the same disturbances in detail, this paper finds that the sequence of monitoring points to detect the frequency fluctuation caused by the disturbances is matched well in the measured data and the simulation results. The similarity comparison index is also proposed to quantify the similarity of the compared cases. The dynamic model based simulation result is expected to compensate for the lack of FNET measurement in its applications.

• 전기학회논문지
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• 제58권7호
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• pp.1255-1262
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• 2009

The present study explained the phenomenon that low frequency oscillation is synchronized with discrete data obtained from a wide area system, and a sync search method. When a disturbance occurs in an power system, various controllers operate in order to maintain synchronization. If the system's damping is poor, low frequency oscillations continue for a long time and the oscillations are synchronized with one another at specific frequency. The present study estimated dominant modes, magnitude and phase of signals by applying parameter estimation methods to discrete signals obtained from an power system, and performed sync search among wide area signals by comparing the estimated data. Sync search was performed by selecting those with the same frequency and damping constant from dominant oscillation modes included in a large number of signals, and comparing their magnitude and phase. In addition, we defined sync indexes in order to indicate the degree of sync between areas in a wide area system. Furthermore, we proposed a wide area sync search method by normalizing mode magnitude in discrete data obtained from critical generator of the wide area. By applying the sync search method and sync indexes proposed in this study to two area systems, we demonstrated that sync scanning can be performed for discrete signals obtained from power systems.

• Journal of Electrical Engineering and Technology
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• 제6권6호
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• pp.776-785
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• 2011

Since the Internet-based real-time Global Positioning System(GPS) synchronized widearea power system frequency monitoring network (FNET) was proposed in 2001, it has been monitoring the power system frequency in interconnected United States power systems and numerous interesting behaviors have been observed, including frequency excursion propagation. We address the consistency of a frequency excursion detection order of frequency disturbance recorders in FNET in relation to the same generation trip, as well as the ability to recreate by power systems dynamic simulation. We also propose a new method, as an application of FNET measurement, to locate a tripped generator using power systems dynamic simulation and wide-area frequency measurement. The simulation database of all the possible trips of generators in the interconnected power systems is created using the off-line power systems dynamic simulation. When FNET detects a sudden drop in the monitoring frequency, which is most likely due to a generation trip in power systems, the proposed algorithm locates a tripped generator by finding the best matching case of the measured frequency excursion in the simulation database in terms of the frequency drop detection order and the time of monitoring points.

• 전기학회논문지P
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• 제61권4호
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• pp.174-179
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• 2012

The social and economic level of damages might be highly increased in the case of wide-area black-outages, because of heavy dependence of electricity. Therefore, the development of a wide-area protection relay intelligence techniques is required to prevent massive power outages and minimize the impact strength at failure. The frequency monitoring and prediction for wide-area protection relaying intelligence has been considered as an important technology. In this paper, a network-based frequency monitoring system developed for wide-area protection relay intelligence is presented. In addition, conventional techniques for frequency estimation are compared, and a method for advanced frequency estimation and measurement to improve the precision is proposed. Finally, an integrated monitoring system called K-FNET(Korea-Frequency Monitoring Network) is implemented based on the GPS and various energy monitoring cases are studied.

• Journal of Electrical Engineering and Technology
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• 제9권1호
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• pp.27-36
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• 2014

This paper presents an adaptive wide-area damping controller (WADC) based on generalized predictive control (GPC) and model identification for damping the inter-area low frequency oscillations in large-scale inter-connected power system. A recursive least-squares algorithm (RLSA) with a varying forgetting factor is applied to identify online the reduced-order linearlized model which contains dominant inter-area low frequency oscillations. Based on this linearlized model, the generalized predictive control scheme considering control output constraints is employed to obtain the optimal control signal in each sampling interval. Case studies are undertaken on a two-area four-machine power system and the New England 10-machine 39-bus power system, respectively. Simulation results show that the proposed adaptive WADC not only can damp the inter-area oscillations effectively under a wide range of operation conditions and different disturbances, but also has better robustness against to the time delay existing in the remote signals. The comparison studies with the conventional lead-lag WADC are also provided.

• 한국산학기술학회논문지
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• 제10권8호
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• pp.1824-1831
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• 2009

본 논문은 대규모 전력 송전망에서 발전기가 사고로 인해 순간적으로 전력공급을 중단하게 되었을 때 과도기간 동안 나타나는 전력계통 주파수의 급강하가 탈락된 발전기의 위치로부터 전력 송전망 전체로 파급되어 가는 전파속도를 분석한다. 이러한 전력계통 주파수 동요의 전파속도는 전력계통 고유의 특성에 따라 다르게 나타나기 때문에 광역적 측면에서 전력 수송망의 특성을 이해하는데 중요한 파라미터이며, 최근 미국의 전력 송전망을 대상으로 운영중인 광역 전력계통 주파수 감시스템(FNET)을 활용한 전력 IT 적용연구에서 중요한 파라미터로 활용되고 있다. 본 논문에서는 방대한 규모를 가진 미 동부의 전력송전 연계계통에 대해 최근의 동적모델을 사용하여 다양한 위치에서의 발전기 탈락을 모의한 후 이에 따른 전력계통주파수 동요의 전파 특성을 분석하고 그 전파속도를 제시한다.

• 전기학회논문지P
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• 제63권4호
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• pp.295-300
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• 2014

The frequency is an important operating parameter of a power system. There is an increasing importance of constant monitoring of frequency to achieve stable power supply by WAMS(wide area monitoring system) and FNET(Frequency Monitoring Network). This paper is part of development of a network-based frequency monitoring and failure prediction system for wide-area intelligent protection relaying. In this paper, analysis of propagation speed of power frequency by generation drop using the PSS/E was carried out. For dynamic analysis, the 11 metropolitan areas offices of KEPCO divided into five groups of Seoul, Gangwon, Chungcheong, Honam, and Yeongnam group, study was performed.

• 전기학회논문지P
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• 제61권2호
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• pp.87-92
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• 2012

Voltage and current phasor estimation has been executed by GPS-based synchronized PMU, which has become an important way of wide-area blackout protection for the prevention of expending faults in a power system. The PMU technique can not easily get the field data and it is impossible to share information, so that there has been used a FNET(Frequency Monitoring Network) method for the wide-area intelligent protection in USA. It consists of FDR(Fault Disturbance Recorder) and IMS(Information Management System). Therefore, FDR must provide an optimal frequency estimation method that is robust to noise and failure. In this paper, we present comparative studies for the frequency estimation method using IRDWT(Improved Recursive Discrete Wavelet Transform), FRDWT(Fast Recursive Discrete Wavelet Transform), and DFT(Discrete Fourier Transform). The Republic of Korea345[kV] power system modeling data by EMTP-RV are used to evaluate the performance of the proposed two kinds of RDWT(Recursive Discrete Wavelet Transform) and DFT. The simulation results show that the proposed frequency estimation technique using FRDWT could be the optimal frequency measurement method, and thus be applied to FDR.

• 전기학회논문지
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• 제60권8호
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• pp.1492-1501
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• 2011

A wide-area protection intelligent technique has been used to improve a reliability in power systems and to prevent a blackout. Nowadays, voltage and current phasor estimation has been executed by GPS-based synchronized PMU, which has become an important way of wide-area blackout protection for the prevention of expending faults in power systems. As this technique has the difficulties in collecting and sharing of information, there have been used a FNET method for the wide-area intelligent protection. This technique is very useful for the prediction of the inception fault and for the prevention of fault propagation with accurate monitoring frequency and frequency deviation. It consists of FDRs and IMS. It is well known that FNET can detect the dynamic behavior of system and obtain the real-time frequency information. Therefore, FDRs must adopt a optimal frequency estimation method that is robust to noise and fault. In this paper, we present comparative studies for the frequency estimation method using IRDWT(improved recursive discrete wavelet transform), for the frequency estimation method using FRDWT(fast recursive discrete wavelet transform). we used the Republic of Korea 345kV power system modeling data by EMTP-RV. The user-defined arbitrary waveforms were used in order to evaluate the performance of the proposed two kinds of RDWT. Also, the frequency variation data in various range, both large range and small range, were used for simulation. The simulation results showed that the proposed frequency estimation technique using FRDWT can be the optimal frequency measurement method applied to FDRs.

• 전기학회논문지P
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• 제59권3호
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• pp.253-257
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• 2010

The frequency is an important operation parameter for the control, protection, and stability of a power system. The frequency as a key index of power quality can be indicative of system abnormal conditions and disturbances. Due to the sudden change in generation and loads or faults in power system, the frequency is supposed to deviate from its nominal value. It is essential that the frequency must be maintained very close to its nominal frequency. An accurate monitoring of the power frequency is essential to optimal operation and prevention for wide area blackout. As most conventional frequency estimation schemes are based on DFT filter, it has been pointed out that the gain error could cause defects when the frequency is deviated from nominal value. This paper presents an advanced frequency estimation technique using gain compensation to improve the performance of DFT filter based techniques. To evaluate performance of the proposed algorithm, the 765kV T/L system in Korea is simulated by EMTP-RV software. The proposed technique can reduce the gain error caused when the power system frequency deviates from nominal value.