| New energy development, power quality management and green energy technology has important significance for the rapid development of modern economy. Within the widespread implements of modern power electronic devices, which can provide a broad development space for industrial process control and energy conversion, among them, the AC and DC converter speed control system plays an important role for power supply systems, but also can cause harmonic hazards. In this paper, the hot-rolling system is chosen as an example, to study the harmonic mechanism in power grid side from various aspects of AC drive system, and harmonic analysis mainly focus on the cycloconverter-fed of rolling main drive system, double back to back drive PWM control and AC-DC-AC inverter drive control of auxiliary drive system. Although there exists significant energy savings in these equipments, some disadvantages also begin to emerge, such as disturbance to control system and decrease on power quality, due to the variations on load and load rate in rolling process. For this reason, the study of such issues can provide the necessary foundation for the study of power quality control system.In order to theoretically analyze the influence on power grid by harmonics, this paper systematically studied the fast Fourier transform method. harmonic analysis, Since the width of the main lobe using the Hanning window function convolution equal participation of the main lobe width of the window function convolution, in multiples of the width of the main lobe, Hanning self-convolution sidelobe window function with an average of less than the width of the rectangular window function sidelobes, but has a faster decay rate.In this paper, the detail anaylsis is made for various types of converter side harmonics both in theoretical study and simluation discussion. The inlflunece factors on harmonics by transformers, converters, load, etc is introduced, the model on single-phase, three-phase, controllable and uncontrollable, AC-AC inverter, AC-DC-AC conversion, dual PWM back-frequency harmonic structures is given, and the harmonic effects on power grid by main drive and auxiliary drive system of hot tandem rolling mills. The shift-in distributed computing method for the calculation of means is illustraed, meanwhile the analysis results is obtained by those simulation study. The main innovation ideas of this paper is shown as follow:First. Through theoretical research and inductive analysis, the equivalent model of single-phase rectifier, three-phase control, not controlled rectifier and inverter system consisting of multiple rectifier harmonic is proposed, which can promote systematic theoretical research on a variety of converters generate current harmonics influence.Second. In order to overcome the defects on complexity and precision of theoretical calculations, the models on AC-AC, AC-DC-AC, dual PWM AC drive back to back as well as their MATLAB simulation models are given, making all kinds of converter current harmonic analysis of the network side to achieve high efficiency.THIRD. In order to save computing resources, ensure real-time computing, and improve computational efficiency, the distributed computing principles based on data shift is proposed. It will make phase difference to single set of data from its multi-phase form, and determine phase difference between multi sets of data for the following simulation analysis. According to the proposed method, the simulation duration as well as the hardware equipment investment is greatly reduced.The results of this dissertation will benefit large multi-group for AC drive applications in the industrial process, reducing the disturbance on the power grid by harmonics. Meanwhile, it provides a solutions for distributed computing and simulation on power grid by harmonics in hot rolling main drive system, and also has significant meanings for eletrical system desgin in metallurgical enterprises. |
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