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Zhang W.,Nanjing Pengtu Power Supply Co., Ltd | Wang Z.,Xuzhou Power Supply Company
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2017

The voltage control technique has become one of the most important functions of distribution management system. Effective voltage control measures can reduce the line loss, improve the voltage quality and enhance system security. The influence on the voltage quality of distribution system with the introduction of DG is discussed first; then the voltage control techniques are summarized, indicating that the hierarchical voltage control is more widely used than the other voltage control methods, in which the zonal-voltage control layer is the backbone of improving the voltage quality, voltage control speed and the system security. Overview of the voltage control of microgrid and active distribution network is presented and evaluated. At last, the development tendency of voltage control techniques is appraised. © 2017 Power System Protection and Control Press.

Xu X.,Shanghai JiaoTong University | Chen K.,Nanjing Pengtu Power Supply Co., Ltd | Long Y.,Nanjing Pengtu Power Supply Co., Ltd | Cheng H.,Shanghai JiaoTong University | And 3 more authors.
Dianwang Jishu/Power System Technology | Year: 2013

Based on timing characteristics of differnet types of loads and distributed generations (DG) as well as environmental perfomances of different types of DG, a planning model for optimal site selection and capacity determination of DG in microgrid, in which environemental cost is taken into account, is built. In the built planning model, the minimization of annual cost of microgrid, including the investment cost for DG, the fuel cost, the cost of network loss and the environment compensation cost, is taken as objective function, and the stochastic power flow based on Monte Carlo simulation is adopted to judge whether the built planning model can meet power flow constraint or not and to calculate the network loss. Finally, the built planning model is solved by genetic algorithm. The reasonableness of the built model is verified by planning results of a 34-bus microgrid system.

Chen X.,Hohai University | Chen K.,Nanjing Pengtu Power Supply Co., Ltd | Liu J.,Shaanxi Electrical Power Research Institute | Ding X.,China Electric Power Research Institute | Yu K.,Hohai University
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2012

The energy balance mode in the distribution network is changed after the distributed generation, microgrid, energy storing device and charge-discharge device of electric vehicles are inserted in the grid. To promote the development of the smart grid, the objectives and devices for the intelligent dispatch of the distribution network are presented following an analysis of the characteristic of the distribution network and its dispatching and control. A multi-dimensional and multi-stage progressive intelligent dispatching mode for the distribution network based on the interaction between the network, power supply and loads are proposed to achieve the goal of efficient operation of the distribution network. And the functional structure of intelligent dispatching of the distribution network is provided. The key techniques to be solved are presented to complete the intelligent dispatching system of the distribution network. The developing tendency for the intelligent dispatching of the distribution network is explored and the research direction summed up. © 2012 State Grid Electric Power Research Institute Press.

Wang Y.,Nanjing Southeast University | Li F.,University of Tennessee at Knoxville | Wan Q.,Nanjing Southeast University | Chen H.,Nanjing Pengtu Power Supply Co., Ltd
IEEE Transactions on Power Systems | Year: 2011

Voltage stability constrained reactive power planning (RPP) or VAr planning is a very challenging issue in power systems. This paper proposes a new approach for modeling and solving VAr planning problem taking into account the static voltage stability constraint. First, the fuzzy clustering method is employed to select new candidate VAr source locations. Then, modified Gray code is proposed and used to represent a series of non-uniform VAr capacity intervals at different candidate buses. Under the new ordering of the VAr capacity intervals, a simplified piecewise linear function between the total transfer capability (TTC) and new VAr capacity is derived and applied as static voltage stability constraint in RPP. Finally, the RPP optimization model is solved by an enhanced simulated annealing (SA) algorithm taking advantage of the modified Gray code. In the SA algorithm, a modified definition of the neighborhood selection and a novel approach to generate new random solutions are proposed. In the case study, fuzzy clustering method, the modified Gray code, and the improved SA are applied to the IEEE 30-bus system. Test results conclude that the proposed method is a simplified and effective approach for voltage stability constrained VAr planning with contingency considered. © 2006 IEEE.

Liu B.,Nanjing Southeast University | Huang X.,Nanjing Southeast University | Li J.,Nanjing Institute of Technology | Qian X.,Nanjing Pengtu Power Supply Co., Ltd | Cheng J.,Nanjing Southeast University
Dianwang Jishu/Power System Technology | Year: 2015

Since the location and the capacity of electric vehicle (EV) charging station impact on both distribution network and transportation network, so the location and the capacity of electric vehicle charging station in distribution network should be taken into account during the planning of distributed generation (DG). For this purpose, a path selection model and an assessment model of urban traffic satisfaction are established, and the timing sequence characteristics of DG as well as the complementarity among them are researched. Considering the fact that DGs have to supply power to distribution network and EV charging stations simultaneously, a model to determine the site and capacity of DGs and EV charging stations, in which the minimum total cost, the lowest network loss and the highest traffic satisfaction are taken as the objectives, is built and solved by new multi-objective free-search algorithm, and then a Pareto solution set is achieved. Taking IEEE 33-bus distribution network as the example, the simulation is carried out and simulation results are analyzed by interactive fuzzy decision. Analysis results show that reasonable grid-connected positions of DGs and EV charging stations and their capacity configuration can be obtained by above-mentioned method, therefore, the proposed model and algorithm are feasible and effective. ©, 2015, Power System Technology Press. All right reserved.

Cao P.,Zhejiang University | Wang M.,Shanghai Municipal Electric Power Company | Guo C.,Zhejiang University | Bai Y.,Zhejiang University | Zhou H.,Nanjing Pengtu Power Supply Co., Ltd
Dianwang Jishu/Power System Technology | Year: 2012

Beginning with local renewable energy source situation and load demand at consumer side, the installed capacities of generating units in smart microgrid were planned; considering economic effect and low-carbon effect the benefit formation mechanism of smart microgrid operation was analyzed, and then through integrating the benefits from the two aspects by low-carbon economic elements a concept of low-carbon integrative benefit was proposed. Combining with construction cost of smart microgrid, an analysis model of low-carbon integrative benefit from smart microgrid operation was built and the principle for day-ahead dispatching of smart microgrid, in which the minimum low-carbon integrated cost was taken as objective, was expounded, and based on typical design case of smart microgrid the income from investments of smart microgrid was analyzed by the proposed model. Analysis results show that comparing with operation modes of traditional power grid, the operation modes of smart microgrid possesses evident superiority in low-carbon integrative benefit; smart microgrid participating the interaction with traditional power grid can play its role in cost adjustment and flexible operation; the operational economy and the low-carbon effect of smart microgrid can be highly unified by means of decreasing the generation cost of distributed energy resources, optimizing pricing system in electricity market and quickening the development of low-carbon economy in the future.

Xu Q.,Nanjing Pengtu Power Supply Co., Ltd
Dianli Zidonghua Shebei/Electric Power Automation Equipment | Year: 2011

A fast ATC(Available Transfer Capability) algorithm with steady-state voltage stability constraint for N-1 contingency is presented, which, based on the continuation power flow method and the curve fitting technique, takes the operating point of N-1 system contingency and the predicted point by sensitivity technique as the curve fitting points to find the approximate nose point for N-1 contingency and then to determine the system ATC. Simulative results of IEEE 30-bus test system validate its feasibility and correctness. Compared with the results of continuation power flow method, it has smaller error and faster speed.

Xue Y.,Zhejiang University | Xu Z.,Zhejiang University | Wang F.,Nanjing Pengtu Power Supply Co., Ltd
Diangong Jishu Xuebao/Transactions of China Electrotechnical Society | Year: 2013

The topology and operation mechanism of a new alternate-arm multilevel converter (AAMC) are described. This topology has two key parts, i. e., director switches made of insulated gate bipolar transistors(IGBTs) in series and wave shaping circuits containing stacks of full bridge sub-modules(SMs). It offers some attractive features such as small amount of SMs, without circulating current, and DC blocking capacity, etc. However, voltage balancing among the SM capacitors is one of crucial problems in the AAMC. To solve it, a voltage balancing strategy based on third harmonic injection is proposed in this paper. The specific process is devided into two steps. Frstly, an energy feedback path is created between the star-point of the converter transformer and the mid-point of the DC-link spilt capacitors; then, an open-loop controller is designed to control the injection current to make sure the whole energy of the wave shaping circuits keep balance. Secondly, a modified phase-shifted carrier-based PWM is poposed to redistribute the energy within SMs. In this method, the switching amount is calculated according to the modulation wave and reference wave, and then the trigger pulses for specified modules are generated based on the polarity of the arm current and the sort results of capacitor voltages. The model of the AAMC with 10 SMs per arm is realized by PSCAD/EMTDC, and simulation results verify the effectiveness of the proposed strategy.

Wu N.,Nanjing Pengtu Power Supply Co., Ltd
2010 China International Conference on Electricity Distribution, CICED 2010 | Year: 2010

The connection of DG makes distribution network topology changed from single-power radial network to complicated network with multi-power. Under such condition, traditional fault location algorithm is no longer applicable. To solve this problem, this paper proposes a new fault location algorithm based on fault current. Firstly, on the basis of the search tree structure of distribution network with DG, the fault channel is determined. Then by using the nodes which are strongly correlated to fault to build fault information matrix and carrying out corresponding matrix calculation according to Kirchhoff's current law and principle of phase comparison, the fault section is accurately located. This algorithm is adaptive to the initial structure of network and DG's switching. Besides, its sensitivity is improved by taking compositive current of weighted summation of sequence current as fault current criterion. Additionally, the validity of this algorithm is verified with example analysis. © 2010 Chinese Soc for Elec Eng.

Tang L.,Nanjing Pengtu Power Supply Co., Ltd | Wu J.,Nanjing University of Science and Technology
Dianwang Jishu/Power System Technology | Year: 2012

At present the phasor measurement unit (PMU) based on clock synchronization technology becomes an important technical means to observe dynamic behavior of power system directly. When power system is in the N-1 failure state, traditional configuration of PMU cannot meet the demand of "whole system observable". If the condition of N-1 failure state is taken into account during the configuration of PMU, more PMUs should be configured than traditional configuration and the cost for the configuration will evidently increase. In allusion to it, a new optimal scheme for PMU configuration is proposed. Firstly, the vulnerability of power system and its branches is analyzed by generalized Tellegen's theorem; then the PMU configuration of the whole system and the PMU configuration considering N-1 failure state are performed; finally through the sorting of vulnerability and analyzing economic index and robustness, the configuration of PMU is determined. The feasibility of the proposed method is verified by simulation results of IEEE 14-bus system.

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