Research On Load Modeling Of Electrolytic Aluminum And Its Influence On Voltage Stability

Digital simulation is the foundation for formulating planning and operating strategies of power grids.Load models have significant effects on simulation results,inaccurate load models may lead to serious discrepancies between calculated results and actual ones,causing potential risks or resource waste.Recently,with the rapid development of electrolytic aluminum industry driven by hydropower in Yunnan Province,the electricity consumption of electrolytic aluminum load have reached 20%of the total amount all over the province.As the sending end of asynchronous grid,the structure of Yunnan power grid is relatively complex,coupled with the large-scale centralized connection of electrolytic aluminum load,the issues of voltage stability are becoming increasingly prominent.It will lead to a significant reduction in safety and reliability of power grid if load models can’t describe the characteristics of electrolytic aluminum load accurately.In response to the issues above,researches are carried out from the following aspects:(1)In research of load characteristics and mathematical model of electrolytic aluminum,the functioning principles of each electrical equipment and control system in electrolytic aluminum plant are analyzed in order to build up the dynamic mathematical model of electrolytic aluminum.By simplifying and improving,a practical load model is proposed to adapt the simulation environment of PSD-BPA.(2)In research of identification of load model’s parameters,a dual objective optimization method based on NSGA-Ⅱ algorithm is proposed to obtain the parameters of active and reactive power model respectively.Facing the issues of parameter consistency caused by time-varying characteristic of power load and insufficiency of PMU data,two methods which based on the principle of multi-curve fitting are proposed.After preprocessing the measured data,parameters of the practical load model are identified.Thus,the model and parameters of the electrolytic aluminum power load used in power grid simulation are established.(3)In research of the influence of electrolytic aluminum load model on voltage stability,the effect mechanisms are discussed in both static and dynamic aspects.An IEEE-9 buses system model is used to validate the theory.Digital simulations based on Yunnan power grid are carried out in static and transient states with the use of PSD-BPA.By comparing and analyzing the differences between practical model and empirical model in the influence of voltage stability,the results indicate that the practical load model and its parameters of electrolytic aluminum load proposed in this paper are beneficial for improving the voltage stability margin of regional power grids and have much higher level of voltage stability during transient processes.