Applied Mechanics and Materials Vols. 448-453

Abstract: Many large power grid accidents show that the tripped transmission line has great impact on system stability. The primary frequency regulation effects of generation units play key roles during a trip procedure. In this paper, a frequency stability dynamic mathematic model of regional power grid was built based on records of a practical trip accident of transmission line between regional grids. Key parameters of the model were identified. The identified parameters are within their reasonable regions. The simulation results show that the modeling method based on parameter identification can be used for modeling of transmission line trip accident procedure and relative frequency stability analyses on power grids.

Abstract: In the given mission environment, the reliability models of materiel system are mixed and made up of series, paralleling and by-pass, and usually dynamic in the mission profile with multi-task phases, with some uncertainty. The method must be combined with Conception Comprehensive Evaluating Model, Conception Optimizing and Improving Method, and formats closed loop process of conception optimization. The method applies to either basic reliability allocation or mission reliability allocation, considers the change of system environment to the effect on mission, and determines system reliability allocation conception oriented on mission, with relative optimization and better application.

Abstract: With the development of electric vehicles technology, especially the development of battery technology and strongly supported by some developed countries in terms of policy, electric vehicle has undergone a rapid expansion in recent years. A lot of electric vehicles are popularized and applied, which will have an impact on power system especially the distribution system. Therefore it is necessary to study the demand characteristics of electric charging and the treatment method and model of access to the network. With this understanding, this article studies the power output model of electric vehicle and analyzes the impact to the distribution network load, the network loss and voltage with different electric vehicles capacity.

Abstract: According to the input and out put of the marshalling stations operating work, the thesis establishes the evaluation index system of the operation efficiency of the marshalling station, then it use the fuzzy DEA model to evaluate the efficiency of marshalling stations operation. At last, the thesis chooses 3 kinds of marshalling stations to calculate their operation efficiency, then compare and analysis them to prove the reasonable method.

Abstract: This paper presents a new method to identify coherent generator groups in power system based on projection pursuit. Projection pursuit algorithm is introduced to model wide-area measured time series and analyses high-dimensional data in low-dimensional subspace. It could seek and extract key projection vectors reflecting generator coherent features and identify the coherency of generators according to projection directions of generators. The presented technique could realize real-time identification of coherent generators, in which grouping is based on measured data avoiding the impact of model parameters. It proves that the composition of principal components has corresponding relationship with system oscillation mode. Finally, China Southern Power Grid is used as testing system to verify the feasibility and effectiveness of the method.

Abstract: Middle-term and long-term load forecasting is important for planning of distribution network. With DG (distributed generation) integrated into network, the net load demand of HV/MV transformers become more complicated, load forecasting encounters greater challenge than ever. Uncertainty of wind and solar power has greatly influenced the load characteristics. A new load forecasting method for distribution network with DGs is proposed in this paper, which concerns time-varying characteristic of DG output power. Firstly, we get the conventional spatial load forecasting results. Then, using Monte Carlo simulation, we get the time-varying characteristic of DG. Lastly, superposing time-varying characteristics of conventional load and DGs, we can get the net-load forecasting result for distribution network.

Abstract: An interface model used in hybrid simulation of power system of transient stability program (TSP) and electro-magnetic transient program (EMTP) is proposed. In the hybrid simulation, the EMTP subsystem is modeled by time-variant real and reactive powers for the TSP simulation of the AC subsystem, and an active frequency depended three-phase Norton multi-port equivalent circuit model is used to represent TSP subsystem for the EMTP subsystem simulation. The interface model makes the hybrid simulation results more precise than those produced by traditional hybrid simulation method. Case studies on a modified IEEE 9-Bus and 3-generator and the 4-generator and 2-area AC/DC test systems demonstrate that the model can effectively improve the accuracy of system TSP-EMTP hybrid simulation both for symmetrical and unsymmetrical contingencies.

Abstract: Input features selection is the premise of transient stability assessment base on neural network method. This paper adopts sensitivity analysis method to calculate the sensitivity-matrix of input features. And on this basis it defines important indexes and impact factors. Based on the gap information of impact factors, it selects the optimal subset of input features, which helps to decrease the redundant information and reduce the dimension of input features. This approach can improve the efficiency and accuracy of transient stability assessment effectively. The results of New England test system demonstrate the validity of the approach.

Abstract: Research of stability of the power systems (PS) assumes the analysis of stability static or dynamic both generators, and engines. This article represents creations of the PS mathematical model is considered as sequence of two stages: creation of models of separate elements; creation of model of their interaction. The mathematical description of a site of distributive system on the example of the synchronous generator.

Abstract: Wind/Photovoltaic hybrid generating system can alleviate power fluctuations caused by the single source and improve the system power supply reliability. In the stage of planning, the grid-connected scheme and capacity limit calculation problem is needed to solve. Under different schemes, the capacity limit is different. This paper established an optimization model of capacity limit of wind/photovoltaic power station, introduced the tracking center trajectory interior point algorithm to solve capacity limit, and demonstrated the validity of the proposed method by a simulation of IEEE 30-node system considering the reserve capacity, and concluded that capacity limit is larger when Wind/Photovoltaic is parallel in heavy load nodes. This method can provide reference for practical system of calculating capacity limit of wind farm or photovoltaic power station and is feasible.