Energy saving, efficiency increasing and emission reduction have become the theme of development of times. In the field of emission control of fume particulate pollutants, Electrostatic Precipitator（ESP）is widely used due to its unique advantages and occupies more than 80% market share in thermal power plant , while the traditional power frequency supply lacks in low dust-removal efficiency and high energy consumption etc.，because it works through several electric fields successively and consumes 3%~6% auxiliary power of thermal power plant. In this case, new-type ESP demands more in energy saving, efficiency increasing and control optimization. How to improve the efficiency of electrostatic precipitator, to reduce energy consumption and emission of dust pollution of electrostatic precipitator and to meet the requirement of higher environmental has become the research focus of electrostatic precipitation technology. The key part of the electrostatic precipitator is its high voltage power supply, so a higher requirement for the high voltage power supply scheme of the electrostatic precipitator is put forward.
This paper focuses on the study of high efficient and energy-saving high voltage high power medium frequency power supply of electrostatic precipitator. A whole electrostatic precipitator system consists of the high-power inverter, the high-voltage high-power medium frequency transformer and electrostatic precipitator controller system.
First of all, the paper puts a study on conversion technology of high-power circuit inversion. Based on the single-phase full-bridge PMW converter theory, the paper analyzes two working modes of hard switching and resonance of the inverter in electrostatic precipitator power supply. Then the circuit characteristics of the above working modes are obtained. Combined with the equivalent load of electrostatic precipitator, the simulation calculation of PWM hard switch mode is carried out by PSIM simulation software, and the correctness of the theoretical analysis is verified. Finally, the working mode of the high-power inverter studied in this paper is determined. Also a control algorithm of the energy feedback converter is studied in this paper.
The high voltage high power medium frequency transformer is different from power frequency transformer and switch power transformer. First, the equivalent circuit of medium frequency transformer is set up, and the calculation method of the distribution parameters of medium frequency transformer and its influence on the circuit are analyzed. The calculation method of magnetic core loss of different magnetic material is discussed and compared. According to the high frequency effects of medium frequency transformer operation, AC winding harmonic model combined skin effect and proximity effect is established and analyst. Based on AC winding harmonic model, the winding method using copper foil, rectangular wire, round wire are discussed. The trial production of a small power prototype verifies the correctness of the harmonic model of the AC winding, which provides a basis for the design of high voltage high power medium frequency transformer.
The high voltage high power medium frequency transformer was be designed based on the analysis of the key technology of above and verification of small power prototype. After determine the working frequency, the magnetic material and its structure and winding structure, the AP method was applied to preliminary design of the transformer and optimization design with the constraint conditions of AC loss and transformer cost. The basic data of the high voltage high power medium frequency transformer is,: input square wave AC 510V, output voltage 72kV, power 80kVA, output current 1.2A, work frequency 500Hz, the efficiency 88%. According to the prototype, the characteristic of amorphous magnetic material was tested, the transformer loss and distribution parameters were calculated .This paper also studies a new sensor for large transformer on-line fault detection.
Based on the electromagnetic simulation of transformer model, the paper analysis the transient characteristics of high voltage high power medium frequency transformer under core saturated and unsaturated conditions by using the finite element method coupled field and circuit. Those transient characteristics include voltage, current and winding force of transformer under starting, steady state and short-circuit condition. In considering magnetic core saturation characteristics and load characteristics of transformer, the voltage, current and winding force characteristic values of transformer are reduced compared with sine wave condition. And the simulation results of overcurrent and overvoltage of transient state under starting time verify the great negative effects to thermal and structure design of transformer.
A peak current control method is designed according to the actual operating conditions of high voltage high power medium frequency power supply of electrostatic precipitator. The paper introduced the realization method of flashover control and back corona control in medium frequency power supply. Combined the full text content, a high voltage high power medium frequency prototype power supply of electrostatic precipitator is developed, and the prototype is verified experimentally. High voltage high power medium frequency electrostatic precipitator system developed has been put into application, running a total of more than 3000 hours, 168 hours of continuous full load operation, the maximum output electric quantity: voltage 72kV, current 1200mA, 80kVA. The maximum temperature of transformer is 79℃, the dust removal efficiency is more than 99%.The object of the paper developed meets the design goals and successful realized the product. At present, there are more than 200 units in the operating.