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Zhou G.,South China University of Technology | Li X.,South China University of Technology | Cai Z.,South China University of Technology | Zhang Y.,South China University of Technology | Qiu L.,Shenzhen Power Supply Bureau
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2010

A same tower multi-parallel line model of phase-splitting parameter is built with EMTDC, which aims to the serious unbalanced current on a Shenzhen 220 kV modernized four-parallel line on the same tower replacing a double-parallel transmission line. Based on study on influenced factors of unbalanced current such as: phase sequence arrangement, line power flow and operation in loop network, suggestions for limiting unbalance current are proposed. Simulation result shows that the strong electromagnetic coupling among each circuits is the primary reason to cause the unbalanced current, and the unbalance of concerned line in the loop network is an important factor as well. Increasing space among lines, reducing the difference of line power flows, adopting negative phase sequence array and loop network open operation under certain conditions are effective measures to limit the unbalance current on a multi-parallel line on the same tower. © 2010 State Grid Electric Power Research Institute Press. Source

Shi Q.,Zhejiang University | Xu X.,Zhejiang University | Zhao Y.,Shenzhen Power Supply Bureau
Dianwang Jishu/Power System Technology | Year: 2016

Different from traditional AC distribution network, DC distribution network is mainly made up of a lot of power electronic devices. To assess reliability of MV DC distribution, reliability models of VSC converter, DC transformer and DC circuit breaker were established to analyzedevice and equipment level redundancy effects on DC distribution system reliability and difference between effects of function failure and insulation failure on DC distribution system reliability. Taking double side power supply DC distribution system for example, influencing factors are quantitatively analyzed and calculated. Comparison results show that equipment level redundancy is better than device level redundancy in improving system reliability, anddifference between function failure and insulation failure mainly influences on reliability calculation of DC distribution system equipped with less DC circuit breakers. © 2016, Power System Technology Press. All right reserved. Source

Zhang H.-B.,North China Electrical Power University | Zhang X.-Y.,North China Electrical Power University | Tao W.-W.,Shenzhen Power Supply Bureau
Dianwang Jishu/Power System Technology | Year: 2010

Taking active load as the fundamental to draw up initial service restoration scheme, by means of judging the relation between total reserve capacity of bus-tie circuit breakers and total load in power interruption region whether the load connected to the second supporting feeders should be shifted in advance is determined to enlarge the range of service restoration. Using breadth-first search algorithm that adopts the restoration of active load as the fundament for the design of initial restoration scheme, the power supply for the non-faulty interrupted region can be restored uniformly while the power supply path will not be too long. Leading in the concept of reserve capacity correction factor, the service restoration scheme can be automatically modified according to the overload condition of voltage or current. Analysis of case study verifies the feasibility of the proposed algorithm. Source

Li Z.,Shenzhen Power Supply Bureau | Wen X.,University of Sichuan
Dianli Zidonghua Shebei/Electric Power Automation Equipment | Year: 2011

Phase-c closing failure of a circuit breaker is found during the regular inspection for a 220 kV line protection, which is caused by the poor connection of circuit breaker's closing winding. A protective circuit is designed to add delayed-trip function to the closing circuit, which effectively prevents the burning of closing winding and intermediate relay when closing failure of circuit breaker occurs. The countermeasures are proposed: quickly switch off the operating power; measure the resistance of closing circuit; inspect regularly. Source

Hong H.,Zhejiang University | Jiang Q.,Zhejiang University | Yan Y.,Shenzhen Power Supply Bureau
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2013

This paper presents a novel model predictive control (MPC) based coordinated control algorithm for the battery energy storage system (BESS) in smoothing out wind power fluctuations. The goal of the method is to minimize the power output of BESS in the next prediction horizon. The variety of constraints is considered, such as the 1-minute and 30-minute fluctuation mitigation requirements (FMR), the BESS maximum power limitation and energy constraint. When the synthetic power output fails to satisfy the proposed FMR, the constraint softening adjustment technology is adopted while taking into account the expected goals to obtain satisfactory optimization results. What is more, the state-of-charge (SOC) feed back control strategy is proposed to regulate the SOC of the BESS within its proper range. Furthermore, an adaptive penalty function of roughness is developed to further smooth the combined output, lower the storage capacity and improve the economy of system operation. Simulation studies demonstrate that, compared with the low-pass-filter-based algorithms, the proposed MPC-based algorithm needs lower power rating and storage capacity. Also, it facilitates engineering realization for its simple algorithm and small computation workload. © 2013 State Grid Electric Power Research Institute Press. Source

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