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Wang C.,University of Hong Kong | Hou Y.,University of Hong Kong | Qin Z.,University of Hong Kong | Peng C.,University of Hong Kong | Zhou H.,Zhejiang Power Grid Corporation
IEEE Transactions on Power Delivery | Year: 2015

This paper proposes a method to establish an optimal dynamic coordinated condition-based maintenance strategy that considers harsh external conditions, for example, harsh weather conditions. Component deterioration is modeled as a Markov process based on physical characteristics, with the effects of harsh external conditions represented as probabilistic models. The proposed model involves interactions between different maintenance strategies on various components, as well as influences on the operation of the entire system. The optimal maintenance strategies are obtained by optimizing the proposed model with the cost to go, including system reliability cost and maintenance cost. This proposed model is solved using a backward induction algorithm associated with a search space reduction approach developed to reduce the simulation time. Two IEEE systems and one actual system validate the proposed model. The results show that this optimal maintenance strategy model that considers harsh external conditions provides insight for scheduling appropriate maintenance activities. © 1986-2012 IEEE.

Bian X.,Shanghai University of Electric Power | Hong L.,Jinhua Electrical Power Supply Company | Wang Y.,Shanghai Donghai Wind Power Co. | Hong J.,Zhejiang Power Grid Company | Fu Y.,Shanghai University of Electric Power
Taiyangneng Xuebao/Acta Energiae Solaris Sinica | Year: 2014

The reactive and active power variation of grid- connected wind farms leads to voltage and frequency fluctuations and instability of power grid. The voltage and frequency control model of Voltage Source Converter HVDC (VSC- HVDC) was proposed to overcome this problem. The mathematical model of wind farm integration system was systematically built. The control link of VSC-HVDC converter WFVSC and GSVSC was well designed. The frequency link was also added to the traditional control model of voltage and power outer loop control and current inner loop control to solve the problem that double fed variable speed wind turbine could not response to frequency variation when the grid frequency changed. The test system of wind farm integration by VSC-HVDC to grid was established, the corresponding HVAC integration was applied for comparison, and wind speed fluctuations and fault were simulated. The simulation results verify that the proposed control model of VSC-HVDC is correct and valid based on test system.

Feng S.,Chongqing University | Wang Z.,Chongqing University | Zhou J.,Zhejiang Power Grid Company | Zhang D.,Zhejiang Power Grid Company | Sun F.,Zhejiang Power Grid Company
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2013

The close coordination between the number of line segments and the grid configuration, as one of the means of improving distribution network reliability, can significantly reduce the power outage time of users. Based on the research on reliability and economy parameters, a kind of high reliability segment rule is proposed with the grid economy and reliability considered together, and then a connection mode of short segments is presented. The result shows that, compared with domestic habitual segments (3 to 5), the number of segments has a substantial increase, so that the optimal segment number of an 10 kV line of 3~15 km is increased to 4 to 18 and the system's average interruption duration index with a tie-connection decreases from 3.53~17.63 h with no segments to 0.67~2.19 h with optimal segments, greatly improving the power supply reliability with the economic benefit guaranteed. Finally, a sensitivity analysis for the segment related parameters is performed. The outcome shows that the optimal segment number of a medium-voltage distribution line is greatly related to the price of a breaker/switch, the average planned outage rate, the energy loss cost and load distribution mode along the feeder. © 2013 State Grid Electric Power Research Institute Press.

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