| With the development of society,various non-linear users have been continuously connected to the power grid,which has caused various power quality problems to become increasingly prominent,which has had a serious impact on the safe operation of the power grid and the safe use of electricity by users.In the low-voltage distribution network,because there are single-phase loads and multi-phase loads at the same time,the three-phase asymmetry problem becomes increasingly prominent,and it is particularly important to manage the unbalanced operation of the power grid.The use of power electronics to manage three-phase imbalances is one of the effective measures.The main research contents of this article are as follows:The principle of three-phase load imbalance management based on instantaneous power theory was analyzed,the main topology of the adjustment device for three-phase unbalanced control of low-voltage distribution network was analyzed and compared,and the three-phase four-leg converter is determined as the main topology of the tuning device characterized by simple control and strong capability of zero-sequence current compensation.A positive sequence,negative sequence and zero sequence current detection algorithm based on instantaneous power theory is designed.The mathematical model of the converter in different coordinate systems is analyzed.Based on the mathematical model in the dq0 coordinate system,a positive and negative sequence current control system based on a PI controller is designed,and a zero-sequence current control system based on an quasi-PR controller is designed.In the simulink environment,a simulation model for adjusting the imbalance of the three-phase load was established by analyzing the unbalanced degree of the negative sequence and the zero sequence.The negative sequence imbalance and the zero-sequence uneven balance before and after system governance are compared and analyzed.The simulation results show that the three-phase load imbalance control scheme based on the instantaneous power theory is feasible,and the three-phase load imbalance control effect is good.According to the design principle,the hardware and software system of three-phase load imbalance adjustment device was designed. |
