通讯机构：
[Xiaoqiao Chen] C;Computing and Mathematical Science Department, California Institute of Technology, United States
关键词：
Demand side management;Electric power plant loads;Electric power utilization;Forecasting;Predictive analytics;Regression analysis;Sales;Adaptive decomposition;Bayesian optimization algorithms;Electrical energy;Electrical energy management;Electricity-consumption;Industrial customer;Load forecasting;Short term load forecasting;Electric load forecasting
关键词：
Distributed parameter control systems;Electric equipment protection;Electric fault currents;Electric generators;Electric grounding;Electric power system protection;Electromotive force;Stators;Winding;Electromotive force distribution;Powerformers;Protection schemes;Single line to ground faults;Zero sequences;Surge protection
关键词：
distributed generations;fuzzy clustering algorithms;Radial distribution systems;single-phase earth fault protection
摘要：
This paper presents a new method based on the relay agent for single-phase earth fault protection in radial distribution systems with distributed generators. In order to get the most informative fault features to discriminate fault for this system, traditional protection schemes based on different fault features are analyzed. The selection of fault features is discussed. Moreover, the cluster center of historical fault data is calculated to analyze the space distribution of fault data for each feeder by applying a fuzzy clustering algorithm. The space relative distance between the online sample data and the cluster center and the minimum value of the space relative distance among all of the relays at the relay agent are obtained. Finally, the coordination strategy of the relay agent is proposed to discriminate the faulty feeder. The proposed protection scheme is evaluated in a radial distribution network with distributed generations using PSCAD simulation.
作者机构：
[王媛媛; 殷惠; 黄路明; 唐夏菲; 林成] Hunan Provincial Engineering Research Center of Electric Transportation and Smart Distributed Network, Changsha University of Science and Technology, Changsha, 410114, China;The Eastern Operation and Maintenance Division, Maintenance Company, State Grid Hubei Electric Power Company, Wuhan, 430000, China;[陈豪威] Hunan Provincial Engineering Research Center of Electric Transportation and Smart Distributed Network, Changsha University of Science and Technology, Changsha, 410114, China, The Eastern Operation and Maintenance Division, Maintenance Company, State Grid Hubei Electric Power Company, Wuhan, 430000, China
通讯机构：
[Tang, X.] H;Hunan Provincial Engineering Research Center of Electric Transportation and Smart Distributed Network, China
关键词：
Distribution networks;FCM algorithm;neutral ineffectively earthed power systems;protection scheme without threshold setting
摘要：
The setting values of thresholds for fault feature parameters are critical in all kinds of protection schemes. When the detected feature parameter value exceeds the setting value, the protection will trip. However, the setting value based conventional protection schemes sometimes cannot satisfy the protection requirements of neutral ineffectively earthed power systems (NIEPS) due to wide variations in operating conditions and the complexities of fault cases. In this paper, a novel single phase grounding fault protection scheme without threshold setting is proposed. The fault detection is achieved based on operating states rather than setting values. A fuzzy c-means algorithm is used to divide the operating state of the protected feeder into non-fault states and fault states. The cluster center of each state is then obtained by classifying the historical feature samples of the protected feeder extracted under various operating conditions into their corresponding states in a constructed multi-dimensional fault feature space. The distances between the detected feature samples and the cluster centers of the non-fault and the fault states are calculated. If the distance to the fault state is shorter than that to the non-fault state, a fault is detected. Otherwise, the feeder is considered normal. A PSCAD/EMTDC simulator is used to simulate a 35 kV NIEPS under various operating conditions, non-linear loads, and complex fault cases. Results show that the proposed single phase grounding fault protection scheme without threshold setting can protect the system correctly under all kinds of faults.
关键词：
Distribution characteristics of data;Fisher discrimination;kernel principal component analysis (KPCA);Powerformer;stator single-line-to-ground fault
摘要：
Some traditional protection schemes cannot detect the faulted Powerformer when a stator single line-to-ground fault occurs in parallel Powerformers. A new discrimination method based on kernel principal component analysis (KPCA) and Fisher discrimination analysis considering the distribution characteristics of the data is proposed in this paper. First, algorithms of KPCA and Fisher discrimination are introduced. In order to increase correct rate of the fault recognition, the kernel function for distribution characteristics of the data is selected according to error rate under historical fault data, which is different from the existing applying validation methods. Then, the detected data in system model is processed to detect whether stator single line-to-ground fault occurred in Powerformer by KPCA and Fisher discrimination analysis based on the optimal kernel function. Finally, simulation results show that the proposed scheme can exactly detect the fault for Powerformer in different neutral grounding systems when stator single line-to-ground fault occurred.
摘要：
This paper presents a new approach for single phase-earth fault protection in distribution systems. Traditional protection schemes are analyzed and compared with one another for effective fault feature extraction. The maximum-likelihood method is also carried out on several copula functions to find the optimal copula to fit the fault feature data. Then, copula rank correlation is calculated by the optimal copula, and the principal component analysis technique is improved to preprocess and reduce the dimension of the fault data by decomposing the copula rank correlation matrix instead of computing the eigenvalues and their eigenvectors of the covariance matrix. Finally, the distance discriminant function is defined and operation criterion is proposed, and distance discriminant analysis is used to discriminate the faulty feeder. Simulation results of a practical 10-kV distribution system show that the proposed approach of fault protection is able to achieve better identification accuracy than the hierarchical clustering algorithm and Fuzzy c-means algorithms-based approaches.
摘要：
The thermal unit commitment (UC) problem is a large-scale mixed integer quadratic programming (MIQP), which is difficult to solve efficiently, especially for large-scale instances. This paper presents a projected reformulation for UC problem. After projecting the power output of unit onto [0,1], a novel MIQP reformulation, denoted as P-MIQP, can be formed. The obtained P-MIQP is tighter than traditional MIQP formulation of UC problem. And the reduced problem of P-MIQP, which is eventually solved by solvers such as CPLEX, is compacter than that of traditional MIQP. In addition, two mixed integer linear programming (MILP) formulations can be obtained from traditional MIQP and our P-MIQP of UC by replacing the quadratic terms in the objective functions with a sequence of piece-wise perspective-cuts. Projected MILP is also tighter and compacter than the traditional MILP due to the same reason of MIQP. The simulation results for realistic instances that range in size from 10 to 200 units over a scheduling period of 24 h show that the projected reformulation yields tight and compact mixed integer programming UC formulations, which are competitive with currently traditional ones.
作者机构：
[胡京莹; Zeng, Xiangjun; 王媛媛] Hunan Province Key Laboratory of Smart Grids Operation and Control, Changsha University of Science and Technology, Changsha 410114, Hunan Province, China;[熊婷婷] Zhuhai Power Supply Company, Zhuhai 519000, Guangdong Province, China
通讯机构：
Hunan Province Key Laboratory of Smart Grids Operation and Control, Changsha University of Science and Technology, China
