Research On Dynamic Compensation Control For Three-phase Unblanced Reactive Power System

With the rapid development of national economy, various large-capacitynon-linear and impacting loads have increased rapidly in the network, such as theindustrial electric arc furnace and electric locomotive, resulting in a three-phasepower system load imbalance. Such unbalanced loads not only affect the normaloperation of the client device but also cause flicker and volatility of the supplyvoltage, increasing line losses, seriously affecting the power quality. In order tosolve the above-mentioned problems, it is necessary to research the compensationtechnique for three-phase unbalanced reactive power systems.In this paper, a comparative analysis about several common reactive powercompensation equipments is given, and then the research on unbalanced reactivepower compensation technology based on TSC is made considering from the degreeof control difficulty and technology maturity to the angle of economy. TSC hasadvantages of low cost, fast response and simple control, with that it can effectivelyimprove the power factor, compensate the reactive power in phase and balance thethree-phase current.In order to make a better compensationg for the three-phase unbalanced loadwith TSC, the control method of balance component compensation for unbalancedload is in-depth study in this paper. The balance component compensation method isproposed based on Steinmetz theory by comparing and aborting the existingcompensation strategy, in this method the three-phase unbalanced load is equivalentto a group of three-phase balanced load and single line load, and the accuratemathematical expression of the scheme is given also. By using the method, thecompensation capacity can be determined from the premise that we just need toknow the three-phase system current before the compensation.To achieve the above-mentioned reactive power compensation scheme, adynamic reactive power compensation device for low-voltage TSC is designed inthis paper. The main circuit is built in closed delta connection, This device chooseARM LPC1766as the controller, and the hardware platform centers on the ARM isbuilt, which includes the grid signal acquisition and processing module, capacitorswitching control, thyristor trigger, man-machine interface; while the softwaredesign includes the functions of the parameter collection and calculation,capacitor grouping and switching, fault protection and Interface display. Finally, thefeasibility of the TSC compensation strategy is verified by the simulation andplatform experiment. The experimental results show that the device can improve thecondition of grid with three-phase power imbalance efficiently and compensate the reactive power fast and accurately.