Study Of The Parallel Operation Of High Frequency Link Three-phase Inverter Based On Virtual Synchronous Generator Control

Nowadays,distributed generation has been continuously improved in the power system,and some distributed generation has to be connected to the power grid through inverter due to its uncontrollability of the dc side power supply.High frequency link three-phase matrix inverter structure is composed of high frequency inverter,high frequency isolation transformer,matrix converter/frequency converter and the output filter,the topology structure can improve noise and volume,and to realize electrical isolation,energy bi-directional flow characteristics,it has a good research prospect.This topology is also widely used in related fields such as grid power generation and motor control.Due to a single application of high-power inverter can't meet some requirements,so it is particularly important that more than one inverter in parallel to increase the capacity of the system,inverter parallel system proved to be more mature,but is still in the study of general inverter in parallel,three-phase high frequency matrix inverter in parallel can improve the system of large capacity,light weight,small volume,low noise and security isolation performance and also can be used in low cost requirements,convenient for installation and debugging of occasions at the same time,so the three-phase high frequency matrix of inverters parallel study has profound practical significance.First of all,this thesis briefly describes the development process of the high frequency link matrix inverter topology,and introduces its research status and advantages and disadvantages,thus clarifying the significance of the project.Secondly,this thesis adopts the Decoupling integrated SPWM modulation strategy to modulate the parallel system of three-phase high frequency matrix inverter.By analyzing the integrated SPWM modulation strategy,the general mathematical model of three-phase inverter with high-frequency link three-phase matrix have a certain relationship,the mathematical model of the inverter based on high frequency three-phase matrix inverter system for mathematical modeling,and the voltage and current double closed loop were designed.Then,the thesis analyze the inverter parallel system research,and derived the expression of a paralleling system circulation through the circuit analysis and formula,thus it is more conducive to the analysis of experimental results.In using Virtual Synchronous Generator(Virtual Synchronous Generator,VSG)transient mathematical model based on second order system,we control the system though using the load of the system voltage and inductor current feedback,and Virtual Synchronous Generator strategy constitute power-voltage-current three loop.Among them,the load voltage loop is controlled by proportional integral adjuster,which guarantees the steady-state error of the system,and can make the control system have droop characteristics.In this thesis,the parallel study of high frequency link matrix inverter based on virtual synchronous generator is presented for the first time,it combines with improving the system capacity,reducing the volume and weight,lower noise,realizing the security isolation and synchronous generator of big inertia,high output impedance,and improving the frequency stability and improving the system circulation,it is verified by Matlab/Simulink software.Finally,aim at this research direction of the topic,we design and set up a chain of hardware circuit about three-phase high frequency matrix based on virtual synchronous generator control of inverter parallel system,and through the DSP chip with CPLD chip to control the whole system together,the experiment verified the correctness and feasibility of the proposed strategy.