Research On The Power Load Modeling Theory And Method Of Interactive Multiple Model

The power load is an important part of power system. And load model has a big influence on the quantitative analysis of the dynamic behavior of the power system, such as power flow calculation, safety analysis, and voltage stability and so on. In critical situations, it could fundamentally change qualitative conclusions of analysis. So, the power load modeling is an important basic research of electric power system, the accurately load model is very important to the safe and stable operation of power system. Power load is time-varying and has the characteristics of composition complexity, and these features make load modeling process difficult. The traditional load model has the fixed construction and parameters. Once the load composition changes, the model is hard to accurately describe the load characteristics.In order to solve the problem of accuracy and time-varying load modeling, this paper made a deep research on modeling theory and method of load model and Interacting Multiple Model algorithm, and the load modeling in this paper is proposed based on the Interactive Multiple Model algorithm. Through the analysis of load characteristic, the power load model set is constructed, which contains the classical load models of substation. And the Classical Load Model is used as the basic structure of the load model in models set. In model set, each model has a weight and a filter. Interaction mechanism of models is built in this paper. The probability transfer of models in Model Set is described by the Markov matrix and the interacting operation of this algorithm is based on it. When the characteristics of the substation is very complicated, if the model set cannot cover all of its features, then the model error will be larger; if the model set covers all of its features, the model number will be too much to increase the calculation, at the same time it may cause the competition of the models, which may lead to the bigger error. So, the model selection mechanism is built, which is based on comparing the normalized weighted sum of innovation squares of the model filters in model set. The Optimal Load Model Set is selected from the overall model set, and only the models in Optimal Load Model Set can be interacted with each other. Because the load model is a nonlinear model, the Extended Kalman Filter is constructed based on the dynamic equation of the model.The state variables of models are recursive acquired by operation of Extended Kalman Filter. Through the calculation of likelihood function, the weights of the model in the Optimal Load Model Set are adjusted. The overall output of model set is the power weighted summation of models in Optimal Load Model Set.As the structure of load model set is too complex, this paper established the fusion mechanism of load model based on the model CLM structure. By models fusion mechanism, multiple models of Optimal Load Model Set are fused into a time-varying load model to describe the overall load characteristics of substation. The structure of the model contains a static load and a number of dynamic loads, and some of the parameters can be adjusted accordingly.Finally, load simulation data is acquired by the PSCAD/EMTDC simulation platform. And the Interactive Dynamic Load Model is constructed in MATLAB. The simulation results verify that the validity of the proposed model.