Research On Optimal Control Strategy Of Power Quality Hybrid Compensation Under Typical Impact Load

The steel and power system industries have always been the aorta and energy pillar of a country’s national economy.In recent years,as the government attaches great importance to the environmental pollution control,traditional steelmaking processes such as the medium-frequency furnaces with more serious pollutants are being accelerated to be eliminated,which has promoted the rapid development of the electric arc furnace steelmaking process with high-efficiency and clean electric energy as the main heat source to a certain degree.However,as a typical high-power shock load with three-phase asymmetry,non-linear characteristics and large fluctuations,the electric arc furnace will cause serious power quality problems after it is put into operation in the power grid.Therefore,it is urgent to analyze and study the power quality problems caused by the electric arc furnace,and to optimize the treatment of the power quality problems such as the harmonic and reactive power,and to improve the power quality of the power grid and the operating efficiency of the electric arc furnace load.In this paper,based on the analysis of the working principle and smelting characteristics of the electric arc furnace steel smelting process,the AC arc mathematical model is established based on the principle of the energy conservation,and the electric arc mathematical model is applied to the electric arc furnace electrical system model to analyze the power quality.At the same time,a fuzzy-PI compound controller of the shunt active power filter is constructed,and a control strategy with hybrid compensation and optimized collaborative configuration is designed to improve and control the power quality problems.Mainly complete the following work:(I).The mathematical model of the arc is established.The relevant parameters of the model are estimated and the simulation verifies the validity of the model.Then taking the melting period where the electric arc furnace has the most serious impact on the power quality as an example,the established arc model is applied to the electrical system model.And based on a 100 t electric arc furnace of an iron and steel metallurgy enterprise,the power quality problems such as harmonic distortion of the power grid and unbalance of the three-phase system are analyzed.(II).Synthesizing the advantages of fuzzy control and traditional PI control,a fuzzy-PI compound controller of the shunt active power filter is constructed,and the improvement effect of this compound controller on the power quality is simulated and analyzed.(III).Comprehensively applying the advantages of the shunt active power filter and the static reactive power generator,a control strategy of hybrid compensation optimization coordination configuration is designed.Then simulating,analyzing and comparing the advantages of this control strategy in improving the harmonic reactive power problems in the power grid.The simulation results show that the arc mathematical model that established in this paper is an effective model.And the designed hybrid compensation optimization collaborative control strategy has a better ability to improve the power quality.