Research On Issues Of Power System Load Modeling

Power system simulation results have guiding function for power research and operation. It is a key point in power research field that improve the validity and the practicality of the models so as to make the simulation results more scientific and reliable. As one of the power system components, importance of load model for simulation results has been generally acknowledged by the researchers and experts. A large amount of the reseach results of the power load fields has been got, and has been veritified in practice. But the results focus on the conventional load, researching load characteristics of the conventional load at the condition of the voltage disturbance. The studing of the special power load is less than the condition, such as the load of the micro power grid or island power grid that system frequency change largely than the inter-connected power grid. A large amount of the reseach results of the power load fields has been got, and has been veritified in practice. But the results focus on the conventional load, researching load characteristics of the conventional load at the condition of the voltage disturbance. The studing of the special power load is less than the condition, such as the load of the micro power grid or island power grid that system frequency change largely than the inter-connected power grid. With the rapid development of electronic information technology, the ratios of the soecial load increase thereupon too.Take the electrification railway traction load for example, not only its capacity is continuously increasing, but also its voltage level of access system is improving with it. Different from the conventional load, the study on the the electrification railway traction load is relatively less, even the the power grid based on the measurement-based data.According to the problems of the load model above, it are investigated step by step in this paper. In small sized isolated power systems or micro systems, when it appeared fault, or involved the special load like shock load etc., load modeling with considering the frequency and the voltage at the same time can better reflect the reality load dynamic characteristic. So an improved measured-based load modeling approach which involves voltage characteristic and frequency characteristic was presented in this paper. The time simulation of the real power system test evaluated that the model is effective and accurate. And the generalization capability of the improved measured-based load modeling was analyzed.By the steps above, taking the real and separated power grid as the research object, a new method which considers the frequency characteristic of load to identify load's parameters is proposed. Two curves of frequency dynamic are simulated using the static load model and the measured-based load modeling considering of frequency characteristic in the simulation system, and then two curves compare with measured-base frequency curve respectively. The results of comparing demonstrate it is reasonable that considering of the frequency characteristic of load to identify load's parameters. On the basis of the load model described above, using of the perturbation theory analyze impacts of the parameters of the measured-based load model on the frequency during the system dynamics. After that, the parameter adjustment is carried out on the above, and the frequency curve of system dynamic is simulated using the parameters after adjustment.With increasing of the electric railway's percentage in railway transport system and improving on the voltage class, the influencing of electric railway special load on grid is getting greater. To establishing accurate and effective of electric railway special load model and ensuring the power system security, based on the measured data and the load modeling strategies, the paper puts forward the criterion of start-up recording data using current activated criterion for the equipment of electrified railway special load characteristic. Furthermore, the research on filed data selection in load modeling was carried out combining the actual production of electrified railway special load. Research of the paper provides data support for electric railway load modeling practice based on the measurement-based data. Studyed on the generalization capability of the load mode from the power grid Perspective, the electrification railway traction load model is estiblishmented. New load model extend application range.In a word, specia load model and load model of the small sized isolated power systems or micro systems are study in the paper. Firstly, the papper discuss the load modek including the frequency characteristics, the annlysis the model parameters is how to influence the system frequency curve. In addition, a new load model that describe the generalization capability of electric railway special load was built innovatively. All the researches above advance the load model practicality and simulation reliability so as to enhance the reliability of the power system analysis.