Development Of Mine Static Var Generator(SVG) Based On DSP

The electricity load of coal mining enterprises has been growing in recent years. In a large mine, an efficiency face load will be over 10000kW. The consumption of electricity into mechanical energy is through the asynchronous motor. However, the power of a single motor is up to more than kilowatts, which will consume a large amount of reactive power. Furthermore, in order to enhance the reliability of the equipment, we tend to use a high-power motor to drive a low-power devices underground, which makes the power factor of the system much lower and resulting in line losses increase and power supply efficiency low and seriously affecting the safe operation of the power supply system. Therefore, reactive power compensation is imperative for the coal mine. At present, a static var compensator (SVC) is used to compensate for reactive power in the coal supply system. However, SVC is controlled by thyristors, which will bring the harmonic pollution to the grid simultaneously. Besides, there exist problems such as the large size of SVC, the explosion, fire prevention, compression of the capacitor, over-compensation and the slow dynamic response, etc. In this paper, for the shortage of both power supply system and the reactive power compensation device at this stage, a static var generator (SVG) experimental prototype used to compensate reactive power is developed, striving to compensate the reactive power in the coal supply system and make it safer and more efficient. The main content of this paper is as follows:The significance of the reactive power compensation in mine is expounded on the basis of consulting a large number of domestic and overseas relevant literatures. The status of coal-powered electricity load in the domestic is discussed. Combined with special electrical environment of the mine, a control strategy for reactive power compensation device is adopted and a system of control programs is established.Accurate and fast current detection is a necessary condition for the system. In this paper, the ip-iq detection method based on instantaneous reactive power theory is adopted to detect active current and reactive current in circuit instantaneously in real-time. The tracking command voltage direct current control method is adopted after comparing the advantages and disadvantages of indirect control and direct control. To generate the required PWM waveform, this paper develops space voltage vector pulse width modulation (SVPWM) achievement rule and keeps track of the command voltage vector by using space voltage vector.The voltage SVG mathematical model is built. The feedforward decoupling control of voltage and current double closed loop control strategy are analyzed and the calculation method of the important parameters in the main circuit is explored. The simulation results, which are obtained by the simulation model in MATLAB, show that the system used in the detection method and control strategy is feasible and effective.On the basis of theoretical studies and simulation, the TMS320LF2407A produced by the Texas Instruments (TI) is used as the core of the control of the entire system. The developed hardware system includes the sampling conditioning circuit of AC signal and DC signal, synchronization and phase locking circuit, driving circuit of the power switch module, various protection circuits as well as man-machine interface circuit. The debug result shows that the stable and reliable hardware circuit can achieve the design requirements.Also, the system software is developed, principally including the initialization procedure, the main program, protect the subroutine, the rms voltage calculation subroutine, the grid frequency calculation subroutine, subroutine of PI regulator and SVPWM generated subprogram. Program written in assembly language will be able to achieve functional quickly and efficiently. The debug results show that the software design is reasonable, portability, and can achieve a given function.The test platform of the entire system is built and joint debugging according to the overall plan of the system. Above all is the fitting of the voltage and current which are necessary for the system control, in order to keep sample and actual values consistent and observe the actual value of each parameter of the circuit in real-time on LCD display. Then in the low-pressure conditions the effect of reactive power compensation is verified. Debugging results showed that the circuits are reliable and the procedures are reasonable. The right modulated waves can be output and substantive results are achieved. All of these work laid a solid foundation for further debugging and optimization of the future system.