Research On Dynamic Compensation Method For Three-phase Unblanced Reactive Power Sysytem Based On TSC

With the rapid development of national economy, the network load capacityincreases rapidly, especially the growing number and capacity of non-linear andimpacting loads, such as the industrial electric arc furnace and electriclocomotive. Such unbalanced loads will cause the current asymmetry, add the extraloss of energy and power, cause the voltage imbalance, worsenthe quality of electrical energy and lead to a large number of line losses. 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 th e 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.The compensative ability of TSC depends on the reasonable and effectivecompensation control method. The concept and formula of three-phase unbalance isgiven first in the paper, and then the split-phase reactive power compensationscheme based on symmetrical component method is proposed by comparing andaborting the existing compensation strategy, and the accurate mathematicalexpression of the scheme is given also. By using the method, the compensationcapacity can be determined from the premise that we just need to know thethree-phase system current before the compensation.To achieve the above-mentioned reactive compensation scheme, adynamic reactive power compensation device for low-voltage TSC is designed inthis paper. The main circuit is built in closed delta connection, which can avoid theneutral current because there is no neutral line. And the current flowing through thethyrisor will be small that can simplify the thermal design. This device choose DSPTMS320F28335as the controller, and the hardware platform centers on the DSP isbuilt, which includes the circuit modules of the signal modulation, capacitorswitching control, thyristor trigger and man-machine interface. The software designincludes 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 the condition of grid with three-phase power imbalance efficiently and compensate thereactive power fast and accurately.