Reasearch On The Power Quality Impacts Of Typical Disturbance Loads In Power System

In modern industrial enterprises and transport sectors, there is a lot of impact, nonlinear and asymmetric load. Along with industrial development and the increase of load, the power quality problems these disturbance loads have caused for the power system are becoming increasingly serious, such as harmonics, voltage fluctuations, as well as three-phase imbalance. Power quality problems not only affect the safe operation of the utility grid, but also bring direct or indirect harm to various electricity usersIn order to analyze and to pertinently reduce the influence of the disturbance load on the utility grid, so as to improve the power quality of modern power grid, detailed load model and clear evaluation system must be established, which enable accurate, reliable comprehensive assessment of the impact of load to power quality.Firstly, indexes of the influence of typical disturbance load to power quality are analyzed in the paper. Three subjective weighting methods including AHP, mandatory marking method and expert-consulting are applied in multi-index comprehensive assessment problem, as well as two objective weighting methods including entropy weight method and variation coefficient method. A combination assigning method based on moment estimation is used to weight different indexes, by which the shortcomings of single weighting methods are overcome. The basic processes of the comprehensive assessment method are introduced in detail, while this method is applied in the comprehensive assessment of typical disturbance load influence.Secondly, in order to study the impact of the electric arc furnace load power quality, a new electric arc furnace modeling method is introduced, and a three-phase electric arc furnace integrated model is established. The model on the basis of the principle of the arc thermal superimposed load fluctuation components to reflect the electric arc furnace grid harmonics, voltage fluctuations and three-phase imbalance. On this basis, PSO applied to the measured current and voltage data, the model parameters were identified, and the identification results with the measured data can be fit well. Load power quality impact assessment method is used in the assessment of the arc furnace load.Finally, to study the influence of traction power supply load on power quality, details of the composition of the traction power supply load are introduced, and the structures and characteristics of various traction power supply system are analyzed. The basic construction of the SS-type AC-DC electric locomotive and the drive principle of the CRH-type AC-DC-AC Multiple Units are researched in the paper. The simulation model of CRH-380A and CRH-380AB are established in Matlab/Simulink, and compared with experimental data, by which the rationality of the models is proven. The concept of the traction power supply quality is introduced. And comprehensive assessment methods are used to analyze the actual data of the power supply system.