Research On The Control Of Three Phase Unbalance Based On Intelligent Switching-phase Switch

Under the three-phase four-wire system of China's low-voltage distribution network,most of the power loads are in sngle-phase.These loads have the uncertainty of power consumption time and regularity,which results in long-term three-phase unbalance in China's low-voltage distribution network,and seriously affects the security and stability of the power grid and its economic operation.The intelligent switching-phase switch is an automatic device for improving the unbalance of three-phase load in a low-voltage distribution network,which is mainly composed of a switching-phase control device and a switching-phase execution terminal.Without interrupting the power supply of the users,the power loads are evenly distributed among the phases by adjusting the users' s side access phase sequence,to achieve the three-phase balance.According to the need to improve the three-phase unbalance of the low-voltage distribution network,this paper researches on and designs the intelligent switching-phase switch.The main tasks are as follows:1.Based on the analysis of basic principle of the three-phase unbalanced,Matlab/Simulink software was used for simulated analysis of the three-phase load unbalance of the low-voltage distribution network;according to the task requirements,the overall design of the intelligent switching-phase switch was carried out.2.A multi-objective mathematical model was established based on the adjustment requirements of the smart phase-change to the side access phase sequence of users,so that the optimization of the multi-objective function was solved by an accelerated particle swarm algorithm.According to the actual operation requirements of the switch,a weight function was introduced into the algorithm as the optimal constraint condition for phase changing.Finally,Matlab software was used to verify the method.3.The intelligent switching-phase switch hardware and software were designed.DSP TMS320F2812 was used as the main controller to complete the circuit design of signal conditioning circuit,analog-to-digital conversion circuit,wireless communication module,and man-machine interaction module.Based on the requirements for the phase-to-phase switching time,a relay with permanent magnet and an IGBT combination were used as the action components of the switch,and the phase-to-phase switching time was analyzed in principle.In addition,the software of the phase-change control device and execution terminal were designed according to the modular programming idea.4.The intelligent switching-phase switch was simulated and debugged under laboratory conditions,and the hanging net experiment of the entire system was arried out.Multisim and Psim softwares were used to simulate the phase-to-phase switching time between the device's signal conditioning circuit and its phase-change execution terminal.According to the simulation results,in order to prevent the intelligent switching-phase switch from causing interphase disconnectiona during the actual work,5ms delay was added to the commutation execution terminal controller programe when detecting the zero-crossing point of the cut-in phase voltage;and the communication function of the device was tested;then,the model device was tested as a whole under laboratory conditions according to the pure resistive load and inductive load states;and finally,the entire system was linked to the network for the trial operation experiment.From the results,the device meets the requirements for the control of the three-phase unbalanced of low-voltage distribution networks.