Research On Hybrid Reactive Power Compensation Device

In the current power system,the universal application of asynchronous motor,distribution transformer,electric arc furnace and other equipment produces a lot of reactive power demand,reactive power has a lot of impact on the public network,so it is necessary to carry out reactive power compensation.TSC and SVG are two widely used reactive power compensation devices,which have their own advantages and disadvantages in compensation characteristics,dynamic characteristics and production costs.In this paper,aiming at the limitations of single reactive power compensation device,a hybrid reactive power compensation device with TSC and SVG is studied in order to realize reactive power compensation of low voltage distribution network with low cost,large capacity and dynamic continuity.The main contents of this paper are as follows:Firstly,the working principle of TSC and SVG is introduced in detail.Based on the analysis of the operating characteristics of TSC and SVG,the interaction between controllers of different reactive power compensation devices and the necessity of coordinated control are pointed out.Furthermore,a hierarchical coordinated control strategy of hybrid reactive power compensation device is proposed.the whole control system is divided into three levels:reactive power coordination layer,reactive power control layer and reactive power execution layer.The reactive power coordination layer distributes the detected reactive power demand to TSC and SVG according to the specific reactive power distribution principle,and gives the switching signal of TSC and the reactive power instruction signal of SVG;The reactive power control layer gives the TSC control strategy and SVG control strategy respectively.The reactive power execution layer is the main circuit of TSC and SVG.Aiming the influence of unbalanced grid voltage on the compensation performance of hybrid reactive power compensation device and its safe operation,SVG in hybrid reactive power compensation device is fully utilized,so that a certain degree of unbalance voltage can be suppressed,at the same time with dynamic reactive power compensation performance.Based on the analysis of SVG operating characteristics under unbalanced grid voltage,the positive and negative sequence double loop superposition control strategy under unbalanced grid voltage is studied.The positive sequence control loop is use for realizing reactive power compensation and stabilize the DC link Voltage,and the negative sequence control loop is used for improving the voltage unbalance degree of the PCC point.The simulation model of hybrid reactive power compensation device is built on MATLAB/Simulink platform,The hierarchical coordinated control strategy of hybrid reactive power compensation device under the condition of grid voltage balance and the compensation performance of hybrid reactive power compensation device under the condition of grid voltage imbalance are simulated and verified.At the same time,the experimental platform of the hybrid reactive power compensation device is built,and the parameter calculation and selection of the main circuit of the hybrid reactive power compensation device and the design of the hardware circuit of the corresponding control system are given.