Research On Inverter Control Strategy Based On Virtual Synchronous Generator

With the rapid development of economy and society,China's annual total energy consumption grew faster and faster,which poses a serious energy shortage and environmental pollution problems.As a result,a large number of renewable energy power generation devices with an inverter as a grid interface are connected to the grid.However,due to the inherent low inertia and under-damping characteristics of the power electronic device,the gird-connected penetration rate of renewable energy generation is seriously affected.In this context,this paper takes the single-phase inverter as an example to study the virtual synchronous generator control strategy,and analyzes the small signal modeling and control parameter design of the virtual synchronous generator,and then puts forward an improved power decoupling control strategy of the virtual synchronous,and finally gives a set of active pre-synchronization control strategy.Based on the operation and control principle of synchronous generator,this paper analyzes the construction method of virtual synchronous generator control algorithm of inverter,and further demonstrates the significance of its moment of inertia for the stability of power system.Then,taking into account the digital control delay and PWM delay and the coupling of the output voltage and the inductor current,the parameter design method of the bottom dual-loop quasi proportional resonance controller is introduced.The establishment of the small signal model of the virtual synchronous generator is mainly discussed.Based on this model,the working characteristics when the virtual synchronous generator operates at standalone mode and gird-connected mode are analyzed.Finally,the design method of the power loop control parameters is given.Aiming at the proposed virtual synchronous generator control algorithm,when the virtual synchronous generator operates at the grid-connected mode,the coupling problem of active power and reactive power control is analyzed.An improved power decoupling virtual synchronous generator control algorithm is proposed to suppress the unnecessary power oscillation of the grid-connected inverter in the power dispatching operation.Finally,in order to reduce the inrush current at the time of grid connection and realize the smooth grid connection of the virtual synchronous generator,a set of virtual synchronous generator active pre-synchronization control strategy is designed based on the working principle of the basic closed-loop phase-locked loop,so that the virtual synchronous generator can actively adjust its own output voltage tracking grid voltage before connecting to the grid,and achieve a fast and effective smooth switching process.