Research And Design Of Soft-switching Device For Three-phase Balanced Distribution

Nowadays, the structure of electric power system is more and more complicated, so that the power rate of system is becoming larger and larger. While the loads carried in a power grid are not all three-phase load, each phase has different number or power rate single-phase loads. It is uncertain whether the load with different power will be operated, and thus inevitably lead to the three-phase imbalance.Aiming at this problem, the existing domestic and foreign technology are set their sights on side of power supply,which design compensator to adjust the power supply system. And manual switching phase will impact load current or need power outage operation directly, causing inconvenience to the people. A new scheme is proposed for local low pressure electricity grid of three-phase in this paper. Firstly, divide all the loads into groups, and then redistribute three-phase load by adjusting each load of power grid phase to achieve the three-phase balance. It achieves the goal of three-phase equilibrium distribution ultimately. The single-phase grid inverter as ancillary equipment during the switching processes. Load switch to device first, and then change the power supply phase. Because device will track grid phase to achieve complete synchronization before parallel operation, so there won’t any impulse current generated in switching. It belongs to the flexible switching process.Through the analysis of all kinds of load switching process, put forward that there is no impulse current generated when the electric equipments are switched on the zero-crossing point of load voltage. This method can avoid the impulse current. The causes of circulation current and its suppression methods are analyzed in this article. It focuses on the comparative analysis of the Grid-connected control strategies of device, and implements the voltage control mode for the soft switching system.Finally, using the DSP control board and IGBT inverter module set up the experimental platform, the physical verification of long-term repeated on the system. Soft- switching device with load switch found in time, to achieve a better load switch tasks, and can ensure the safety of the device itself. Thus, the soft switching system is feasible, and has good practicability and application prospects.