| The load change of AC electric arc furnace was non-linear,fluctuating and random.Access to the power grid would cause deterioration of regional power quality,cause economic losses and affect the safe and stable operation of the power system.This paper established an improved AC arc nonlinear time-varying resistance model in MATLAB/Simulink,simulated and analyzed the power quality problems of AC arc furnaces,and established a variable fuzzy cloud model for comprehensive evaluation of power quality quantification levels.On this basis,the design and selection of governance plans were carried out.The main research work was as follows:First,based on the AC arc nonlinear time-varying resistance model,this article used arc current to calculate the arc diameter according to the energy balance of the arc.At the same time,a given range of random numbers was used to represent the arc length change.Compared with the existing models,the model was more in line with the actual working characteristics of the electric arc furnace.On this basis,equivalent modeling was carried out for the actual AC arc furnace,the model parameters were determined by parameter estimate according to the arc output volt-ampere characteristic curve,and the three-phase electrical system equivalent model of the AC arc furnace was formed in combination with the system structure.Through calculation and quantitative analysis of its influence on the power quality indicators of the power grid under different working conditions.Secondly,this article used the FAHP method and the coefficient of variation method to carry out subjective weighting and objective weighting respectively,and used the least square method to calculate the subjective and objective comprehensive weights.Improved the calculation method of inverse cloud expectations based on the variable fuzzy set idea,and adjusted the relative membership degree of each sample data to different grade intervals as the weight to form a variable fuzzy cloud comprehensive evaluation algorithm,which was more effective than traditional methods.On this basis,combined with the model simulation,the variable fuzzy cloud model was used to comprehensively evaluate the power quality of the AC electric arc furnace,and to quantify the impact level of the power quality of the power grid under different working conditions.Finally,according to the load characteristics of the AC electric arc furnace,this paper designed two power quality management schemes,TCR+FC SVC based on instantaneous reactive power theory and phase compensation principle,and STATCOM with direct current control.The variable fuzzy cloud model was used to quantitatively evaluate the impact of the AC electric arc furnace power quality after the two treatments,and used this as a basis for the selection of treatment schemes in different situations in combination with economy. |
