Research On Control Technology For Parallel Operation Of Three Phase Inverters

Under the dual pressure of environmental pollution and the depletion of traditional energy sources, the demand of new energy and clean energy is increasing, and the application of wind power, photovoltaic, tidal current power generation and other new energy sources,inverter as the need to achieve high power and grid, in the power generation system plays an important role. But in the growing power demand of power, the single power supply capacity is limited, and the parallel redundant operation of multi module inverters can not only increase the power of the power system, but also enhance the stability and reliability of the system.Research on three phase inverter, as the main part of the parallel, the mathematical model of three-phase inverter is established with the circuit topology structure, and the transformation is carried out in three phase static coordinate system and synchronous coordinate system; the double closed-loop control strategy of inverter sampling voltage and current is used to calculate the double loop decoupling of the mathematical model, and design a double loop controller based on the synchronous coordinate system. Meanwhile, the space vector modulation technique is studied and the parameters of LC filter are calculated.According to the above calculation, the inverter simulation model is built in Simulink, and the stability and dynamic characteristics are simulated. The results show that the designed inverter meets the expected target.Based on the analysis of several parallel modes, the theory of distributed parallel operation mode is studied. Firstly, the operating condition of the parallel operation is analyzed,and the parallel system structure is studied with the main reference of the two inverters, the system can bring the circulation problem because of the output voltage phase or the different device parameters, and after the analysis of the current control strategy, the control strategy is adopted. Based on the transfer function of the inverter, the design method of H controller is presented. The circulation in the system is given as a compensation to the voltage loop of the controller, and the output current of the inverter can be suppressed by the flow of the inverter.At the same time, the control strategy of the phase locked loop and preemptive synchronization is studied. The inverter output in the system has no phase and frequency difference, which further reduces the factors of the circulation of the system. According to the above contents,the simulation of the parallel system in Simulink is carried out. The results show that the H loop controller can compensate the controller well, so that the output current of each inverter will be the same and the circulation will be reduced.In the end, the hardware circuit is designed, and the software part is written in the main program and control subroutine. On the basis of this,a system test bench is built. Experiments were carried out under the condition of independent and parallel operation. The results show that the effectiveness of the design scheme can achieve the desired results.