Research On Filtering And Phase-locked Technique For Power Electronics VAR Compensation System

The mine grid consumes plenty of reactive power,so the power factor is relatively low.The power electronics var compensation system can enhance the power factor and improves the voltage quality by inputting the reactive power into the grid.This paper studies the two key techniques of the static reactive power compensation system: the phase-locked technique and the filtering technique.This paper establishes the mathematical model of the static var generator(SVG)and develops a dual control strategy based on parallel Quasi-PR control to realize the zero steady-state error track of the command current.Voltage-oriented vector control strategy is employed to resolve the problem of the integration offset in the flux-oriented vector strategy.The simulation result shows that the developed dual loop control strategy's structure is easy to realize and it has good performance in dynamic response.A phase-locked loop(PLL)based on the second order generalized integrator is developed.Its structure is simple and clear and it has quick dynamic response and good ability to suppress the distorted grid voltage when compared with the traditional dual decoupled synchronous reference frame PLL.The simulation verified the performance of the designed PLL under various conditions.This paper employs a more stable and safer damping strategy—passive damping strategy to restrain the resonant peak in the LCL filter and designs the parameters of the filter based on the attenuation of the harmonics.The inverter-side current feedback is proved more stable and the passive damping strategy is proved to have good filtering effect and higher security coefficient through the comparison and analysis of different feedback parameters and filter types.Finally,a 100 kVA sample based on the controller named TMS320F28335 is developed.This paper completes the design of both the hardware and the software.Experiments are conducted based on the developed sample.The results demonstrate the good stability and dynamic characteristics of the SVG sample and validation of the designed DSOGI-PLL and the LCL filter.