Research On Unbalance Compensation Control Strategy For Three-phase Inverte

With the development of the times,the large consumption of petroleum fuels and the continuous emergence of environmental problems have caused countries to jointly solve the nature of renewable energy.The renewable energy grid-connected power generation technology has now become the focus of domestic and foreign research.The rapid integration of renewable energy sources to reduce voltage sags and imbalances in voltage and voltage in actual operation of low-voltage distribution network systems.Among them,short-circuit faults,large-capacity equipment startup,and other causes of high-voltage voltage The balance problem is because the load in the switching network cannot be fully balanced,including single-phase loads,voltage unbalanced loads,and so on.How to control the inverter to solve the problems of voltage rise,sag and imbalance at the grid connection point is the focus of this article.This paper first analyzes and introduces the current situation of power quality problems in low-voltage distribution networks and common strategies adopted in different power quality problems.Secondly,a three-wire winding LCL grid-connected inverter topology is established,and the inverter is established under unbalanced grid voltage.The mathematical model under the grid connection of the inverter.By analyzing the mathematical model under the grid connection of the inverter,it is found that the grid-connected current will be affected by the grid voltage,which will cause the grid-connected current distortion,so as to suppress the grid-connected current distortion.The grid voltage is added here.Feedforward control.Because a three-wire series LCL-type grid-connected inverter is used here and the LCL filter has resonance spikes,it is suppressed by using a capacitive current feedback inductive damping control strategy,and mathematical modeling is used to derive the grid-connected inverter The transfer function of the transmitter system is obtained by using Matlab to obtain the Bode plot of the transfer function,and the effect of the capacitor current active bias control strategy on the suppression of resonance spikes is verified.At the same time,in order to improve the grid voltage and frequency fluctuations,current quasi-PR control is used to implement and Network and deriving quasi-PR parameters.The relationship between the negative sequence voltage and the grid current,load current and line resistance under the voltage imbalance of the grid connection point is analyzed.Reconfiguring the virtual admittance on the inverter side changes the output characteristics of the inverter and improves the ability of the inverter side to absorb negative sequence current on the load.Secondly,it analyzes the relationship between the voltage change and the power flowing through the grid and the line resistance when it is balanced with the grid voltage,and performs power compensation according to the line resistance ratio R/X,and references the parameters k₁ and k₂ to distribute the inverter output power.Finally,an LCL-type grid-connected inverter experimental system based on DSP TMS320F28335 was constructed,and the unbalanced voltage compensation and voltage sag compensation control strategies proposed in this paper were experimentally verified.The experimental results verify that the strategy here can effectively improve the voltage imbalance of the grid-tied point and stabilize the grid-tied point voltage.