Research On Control Method Of Voltage-grid-connevted Inverter Current

In recent years,the large-scale,uncontrolled development and utilization of fossil fuels has accelerated the depletion of energy.The rapid growth of global energy consumption has not only caused serious environmental pollution,but also has a great negative impact on the economy and society.At the same time,the cost of environmental pollution control is high.Therefore,vigorously developing new energy sources such as solar energy,nuclear energy and tidal energy is an inevitable choice for ensuring energy supply and sustainable development.As a key part of the new energy generation process,the grid-connected inverter system can convert the electric energy in the form of DC into the electric energy in the form of AC.The state of control and operation will directly affect the quality of the power that is incorporated into the grid.The control technology of the transformer is particularly important.For the control of the inverter,it is necessary to meet the same voltage and current in phase with the same frequency,and also ensure that the total harmonic distortion rate of the incoming current is within the national standard.In this paper,the three-phase LCL grid-connected inverter is taken as the analysis object.In view of the shortcoming of the dynamic response of the traditional active damping control method,the composite damping of the traditional active damping combined with the new resonant suppressor is proposed based on the capacitive current feedback method.The controller improves current quality and system response speed.Then,in order to solve the problem that the single proportional complex integral(PCI)control has poor adjustment effect after the change of external reference command,the three-phase LLCL type grid-connected inverter with switching frequency notch function is taken as the research object,and the proportional complex integral is proposed.(PCI)combined with quasi-proportional resonance(QPR)composite control method,in which PCI control can realize AC error-free tracking,QPR control can ensure the system has a certain bandwidth,and the composite control method reduces the harmonic distortion rate of the steady-state network current while ensuring the dynamic adjustment effect after the change of the external reference command.Based on the above research,in order to verify the accuracy of the proposed method,a three-phase LCL grid-connected inverter model and a three-phase LLCL grid-connected inverter model were built and simulated in Matlab/Simulink simulation software.The simulation results show that the proposed method has better effect in reducing the harmonic distortion rate of grid-connected current,improving the current quality and system response speed,and ensuring that the grid voltage and the incoming current are in phase with the same frequency.Finally,the RT-LAB hardware-in-the-loop simulation platform is built to verify the correctness and feasibility of the proposed control method.