Study On Control Strategy Of Parallel Inverter System

With the rapid development of social economy,traditional fossil energy is decreasing day by day.To force people to find new energy structure,distributed generation should come into being.Parallel inverter control is an important means to improve the redundancy and reliability of power generation system.However,distributed generation has the characteristics of dispersion,which makes it difficult to realize interconnection communication because the inverters are far away from each other in space when operating in parallel.Therefore,the parallel control technology of inverter power without interconnection has become a research hotspot,and the problems of power equalization and circulation suppression need to be further improved.In this paper,the topology and mathematical model of the main circuit of a single inverter are analyzed.This paper introduces the pulse modulation technique used in inverter and designs the filter based on it.The voltage-current double-loop system is established and controlled by decoupling.The frequency domain analysis of the whole inverter is carried out to facilitate the design of control parameters.Then,based on the parallel system of two inverters,the corresponding output power expression and droop control equation are derived.The circulation of the system with different circuit properties is analyzed.Taking the inductive circuit as an example,the virtual impedance branch is designed,and the conventional inductive droop control is analyzed.An adaptive droop control strategy based on angular velocity deviation and rate of change is proposed and compared with conventional droop control.Furthermore,in order to introduce inertia into the inverter control system,virtual synchronous generator technology is introduced into the inverter unit.The virtual synchronous generator model is established based on the synchronous generator structure,voltage equation and rotor motion equation,and the performance of P/f control loop is analyzed.An adaptive virtual rotary inertia control strategy is proposed and compared with the traditional control strategy.