Research On Control Technology For Unblanced Reactive Power Of Three-Phase System

In modern power system, a variety of single-phase loads can lead to unbalanced three-phase reactive power. TSC var compensation technology has some advantages such as low cost, rapid response, no mechanical consumption, also can effectively raise the system power factor, and balance reactive power of three-phase system. Therefore, to solve the problem of unblanced reactive power, it's significant to do research on split-phase control technology of TSC var compensation device.By research on the split-phase control technology of TSC system, TSC var compensation controller based on the chip of TMS320F2812 is designed and its operation principle is explained in detail. The hardware platforms, including control system, HMI, are designed. The functions of software such as parameter calculation, capacitor switching control, LCD display, are realized, so that software resources can be fully used and integration and reliability of the control system can be improved. For the Thyristor zero-voltage switching problem of TSC main circuit, zero-flux current sensors are used to measure DC and AC voltage of Thyristor, and the zero-voltage testing circuit and trigger circuit are designed.To overcome the shortcomings of traditional TSC controller, some existed control methods are improved. (1) Step-switching usually caused over-compensation or under-compensation, so all the needed capacitors are switched in one time. (2) To satisfy various applications, the power factor and voltage priority control strategy are proposed based on the traditional improved nine-zone strategy. (3) Capacitor cycle switching software mode is realized for the equal capacitor, avoiding the capacitors'overheat explosion caused by long working time. This feature ensures all equivalent capacitors running in turn, and the total compensation is equal. (4) Two solutions are proposed, including the switching delay time and discharge resistor, which can solve the problem of switching instruction oscillation that may occur during the operation of TSC split-phase var compensation device.To test the above control methods, a low-voltage experimental platform is built. Simulation analysis and experimental results indicate that the device can compensate the reactive power accurately, improve the power factor, supply better real-time feature and effectively balance reactive power of three-phase system. The control algorithm and design proposal in this paper are feasible.