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Now the measurement means of access capacity at all levels of distribution network are insufficient and it is difficult to calculate effectively based on limited data. This paper proposes a hierarchical evaluation method of access capacity of distribution network with multiple prosumer group load forecasting. Firstly, a load dynamic prediction model is constructed. According to the typical load model of historical data mining, a unit prediction model of typical users is established by using the conjugate gradient RBF neural network learning algorithm. Then, according to the charge-discharge dynamic model of the energy storage power station and the load dynamic prediction results, an assessment model of access capacity at the 10kV side was constructed. By analyzing the known load type, load type ratio and transformer capacity on the low-voltage side, the conversion coefficient of 10kV side load to 0.4kV side transformer capacity is obtained by weighting different types of loads proportionally. Then, access distribution capacity of different prosumer group can be obtained based on conversion coefficient. It can ensure the effective measurement of access capacity at all levels of distribution network under the premise of meeting N-1 safety criteria. Finally, an example is given to demonstrate the effectiveness of the proposed method.

In order to meet the demand of prosumer for power quality and new load in distribution network, an open capacity expansion model of distribution network with mobile energy storage system (MESS) is proposed in this paper. The model gives priority to the problem of voltage violation of prosumer group on feeders. Combined with the mobile energy storage path model, the open capacity of distribution network is calculated. Firstly, the actual distribution network geographic information and traffic routes are combined to establish the distribution network model based on mesh generation. Secondly, the traffic route model of the mobile energy storage system is established on the distribution network model based on mesh generation. Then, the optimal power flow of distribution network is calculated with the optimal network loss, and the mobile energy storage system is scheduled according to the situation of voltage violation. And the specific vehicle model and its scheduling are determined, which can better deal with the problem of distributed energy consumption and make prosumer operate safely and economically. Finally, according to the proposed N-1 security check constraint of distribution network with mobile energy storage system, the maximum open capacity of distribution network is calculated after the voltage regulation is completed. The example shows the practicability and correctness of the model in this paper. This paper formulates a mobile energy storage operation strategy to improve the open capacity of distribution network. The strategy not only fully meets users’ needs, but also better guides the operation of power grid. It is conducive to releasing more potential power supply space of distribution network and improving asset utilization.

This paper proposes the data mining method of voltage sag severity based on DHP algorithm and replaceable coefficient to assess the risk of voltage sag. The DHP (Direct Hashing and Pruning) is served to mine the relationship between voltage sag characteristic attribute (VSCA) in the fault scenario and the voltage sag severity (VSS) of node. Using direct hash pruning technology, frequent item sets can be found quickly and mining efficiency can be improved. The association rules are matched with the actual fault scenarios through replaceable coefficients to get the VSS of actual fault scenarios. Finally, the effectiveness and accuracy of this method are verified by simulation and examples.

With the increasing of electric vehicles (EVs) users, a large amount of reserve charging infrastructure have to be deployed in distribution systems to the uncertain charging demand, which may lead to redundant investment. In order to reduce unnecessary investment and optimize the plan of charging station and distribution network, a multi-objective planning model is proposed. The objectives of planning model include the benefits of both distribution network and EV user. The proposed method has been verified on a modified 54-bus distribution and 19-node road system. The results shows that the proposed model can give collaborative plan, and ensure the benefits of both the distribution side and user side.

After Xiamen VSC-HVDC Project is put into operation, it can improve the power supply capacity and reliability of Xiamen Power Grid.But at the same time,it also brings new problems to the operation of the power grid, among which the short-circuit current problem is particularly prominent.In the preliminary analysis of power grid operation, using the short- circuit current program (PSD-SCCP) commonly used in domestic power grid simulation analysis to calculate to be found that:VSC-HVDC will provide a large short-circuit current when the AC grid is short-circuited, causing the short-circuit current levels of multiple 220kV busbars of the Xiamen Power Grid to approach or exceed 50kA, which brings greater pressure on the adjustment and arrangement of the grid operation mode.Therefore, it is necessary to study the true level of the impact of Xiamen VSC-HVDC on the short-circuit current of the AC grid based on the actual control logic of the Xiamen VSC-HVDC project, in order to propose more accurate short-circuit current suppression measures to achieve bipolar operation of Xiamen VSC-HVDC.

In order to accurately evaluate the impact of voltage sag on both utility and customer, a data mining analysis method based on improved FP-growth algorithm and AHP algorithm is proposed. The proposed method selects and classifies voltage sag characteristics and combines voltage sag severity level to construct a data mining analysis framework. The improved FP-growth algorithm is used for data mining on voltage sag events to improve the efficiency of mining. The association rule matching model is constructed by AHP algorithm for evaluating the voltage sag severity level, which improves the accuracy of the evaluation results. Finally, a practical example verifies the practicability of the proposed method.

VSC-HVDC has been widely used at home and abroad, but there is no clear conclusion about the characteristics and calculation method of the short-circuit current contributed by VSC-HVDC during the AC Short-Circuit Fault near the converter station. The calculation methods in the field of short-circuit current engineering have not been unified, and the adaptability and error of different methods have not been analyzed in detail. Through electromagnetic transient simulation, this paper analyzes the transient characteristics of VSC-HVDC contribution short-circuit current, and combs the key influencing factors of VSC-HVDC contribution short-circuit current. Finally, taking a VSC-HVDC system in China as an example, the adaptability of the commonly used short-circuit current algorithm is analyzed. It is verified that the existing engineering algorithms have made great progress compared with the original. However, compared with the electromagnetic transient refined simulation, there is still a large error in the calculation results of individual nodes under some control modes / fixed values.