Research And Implementation Of Mine Static Var Generator Based On DSP

In recent years, with the development of coal enterprises, the safety and efficiency of the mine arouse people’s attention gradually. As a result of the existence of three phase asynchronous motor and other reactive load, the power factor of the coal mine power system runs for a long time in between0.4～0.7, voltage loss and power loss are serious, and the normal start of the equipment is affected, thereby reducing the quality of the power supply. In fact, the rationality of mine power system determines the safety, economy and reliability in coal mine’s operation to a great extent. To solve above problems, this paper developes a set of static var generator (SVG) device used in the coal mine power system, using the reactive power compensation technology to improve the power factor and the voltage stability. The energy conservation and the guarantee of production are of great significance for the coal enterprises. This article’s main research content is as follows:On the basis of analysing present situation at home and abroad and reviewing related reference literatures, the principle of reactive power compensation devices is studied. Combined with the coal mine power system and the actual situation of the power load, this paper expounds the necessity of reactive power compensation, analyses the various advantages of SVG and explains the rationality and superiority of its application in underground.The structure of the common main circuit of SVG is introduced. Through the analysis of the SVG main circuit phasor diagram, the working principle of SVG is illustrated. The mathematical model of SVG is established, and the three-phase static coordinate system (a, b, c) and two phase rotating coordinate system (d, q) mathematical model are reduced. The characteristics of the mathematical model under two different coordinate systems are analyzed. In the establishment process of the mathematical model, this paper illustrates the principle of coordinate transformation. The implementation process of coordinate transformation is illustrated. Depending on the setting of the compensation capacity and voltage grade, as well as the engineering practice, the selection of main circuit parameters is finished.The method of detecting reactive current is discussed, and instantaneous reactive power theory in three-phase circuit is introduced. Then it uses ip-iq method to detecting reactive current, does creative changes to αβ-dq coordinate transformation matrix in the period. The method of indirect and direct current control for SVG is analyzed, PWM control of hysteresis and that of fixed switching frequency in direct current control is importantly introduced, whose advantages or disadvantages and different application occasions are compared. In order to solve the coupling problem of active current ip and reactive current iq in rotation coordinate system, the method of feed forward decoupling is adopted, which realizes independent control.The principle and implementation rules of space vector SVPWM modulation technology is studied, then the control strategy of the system is established as SVPWM direct current control,which is based on fixed switching frequency of tracking instruction voltage.The hardware circuits of the SVG based on the TMS320LF2407A DSP chip are designed, which is the core controller of the whole system.The whole hardware system is divided into signal detection circuit, the minimum system control circuit, power device driver circuit and system protection circuit, etc.The parameters of the circuits are selected, and the PCB board is drawn on the basis of principle diagram.In the software development environment CCS3.1of DSP, the program with assembly language is wroted. The software programs include the DSP initialization configuration program, the main program of sending data, protection subroutine,power grid frequency calculation subroutine,AC voltage amplitude calculation subroutine,PI regulation subprogram and SVPWM pulse generation subroutine,etc.The system data will be real-time displayed on the screen.The man-machine interface is designed and the communication program between DSP and the touch screen is wroted, which implementing the information exchange between operating personnel and control system. According to the design scheme of the software and hardware, the experimental platform of SVG is set. The SVG debugging of hardware system and software system is completed, and the problems appeared in the process of debugging are solved. The experimental results of SVG show that the hardware circuits are stable and reliable, the structure of software program is reasonable and the execution speed is fast, which lay a foundation for further improvement and majorization of the system.