| Due to the rapid development of power system engineering technology and the constant expansion of power grid scale in recent years, building a strong unified smart grid makes new and higher requirements on intelligent dispatching of power network. On-line and real-time simulation results are the main decision-making bases of power grid operation scheduling and security stability control. It is the inevitable development trend of the power grid dispatching under the conditions of smart grid construction. And the real-time and accurate power grid simulation calculation must be dependent on the real-time and accurate load model. But the current power grid simulation generally adopted a set of existing load model and parameters, which can not fundamentally meet the requirements of the load model in accurate real-time simulation calculation.This paper is based on the actual situation of the current power system load modeling work. Aiming at the random time-varying problem of load characteristics, the paper establishes a complete set of the substation comprehensive load online-modeling theoretical method and implementation technology after in-depth study of power system load modeling method. Firstly, by using the component-based approach and the measurement-based approach, the load model is obtained. And then the load model parameters are modified online or predicted on the basis of the composition analysis of the typical electricity industries, in order to obtain the real-time or future-time parameters of the load model. Based on statistical principle, the component-based approach starts the load modeling from the bottom of the electrical equipment, and gradually weighted, to the industries, and then to the substation. Based on system identification theory, the measurement-based approach uses the field measured data and identification algorithm to determine the model structure and model parameters which can make the model response best fitted to the observed data. The composition analysis method of the typical electricity industries is based on the user and substation daily load power curves respectively acquired by Load control system and SCADA system, which are stored in the Massive data storage platform. Through the classification and synthesis of all the users belonged to the substation, the equivalent daily load power curves of several typical electricity industries are obtained. Then according to the mapping relationship established between the equivalent daily load power curves and the substation daily load power curve, the composition proportion of typical electricity industries can be analyzed by using the least square method. On the basis of this method, using the real-time and the load forecast daily load power curves to analyze the real-time and day-forecasted composition proportion of typical electricity industries. Combined with the load model parameters of typical electricity industries, the real-time and day-forecasted parameters of the comprehensive load model can be obtained. Finally, the on-line correction and prediction of the model parameters are realized.According to the needs of different modeling methods, four kinds of data are used for comprehensive load modeling in this paper:user data (including survey data and load control data), SCADA/EMS data, recorded fault data and WAMS/PMU data. The paper elaborates on the integration method of wide area information from several aspects such as the source and characteristics of wide area information, downloading and preprocessing method, database design and storage process, which forms a wide area information database to provide data for load modeling system.With the comprehensive load modeling method and wide area information, based on the Windows operating system and structured design ideas, this paper uses the object-oriented visualization software Visual Studio 2005 as the programming environment, using C++as the programming language and the relational database SQL Server 2000 as the local data management server. To achieve the operation of wide area information database, the paper uses ADO (ActiveX data object) data interface technology. Based on the above technology, a complete set of the substation comprehensive load online-modeling system has be constructed. This system mainly consists of six modules, the data source download and preprocessing module, wide area information database management module, load model identification module, load model parameters on-line correction module and load model parameter library management module. The system calls these modules through WinExec function and dynamic link library (DLL). The main functions of the system are to download, preprocessing, query and modify wide area information data, to form the historical or real-time wide area information database, to achieve load model identification and on-line correction based on the wide area information database, and to form a complete historical and real-time load model parameter library for simulative calculation of Power Network.The substation comprehensive load online-modeling system developed in this paper has been used in a provincial power dispatch and control center. It is stable in operation. Compared with the previous load modeling system, the operation is more simple and flexible, and the function is more perfect. |
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