Research On VSG Control Strategy For High Permeability Distributed Power Supply

Since the 21 st century,energy crisis,environmental pollution and other issues have occurred frequently.In order to implement the concept of sustainable development,microgrid technology based on renewable energy has received extensive attention.Micro-grid is an effective way to comprehensively use distributed power,not only to achieve local consumption of new energy,but also to fully exploit the economic benefits of distributed generation.But as distributed power penetration increases,a series of problems are gradually exposed.The biggest problem is the lack of rotational inertia and damping components,which are precisely the characteristics of Synchronous Generators(SG)in large power grids,and can participate in the regulation of grid voltage and frequency.If the characteristics of the synchronous generator can be simulated during the grid connection of the inverter to have the corresponding inertia and damping characteristics,the problems faced by the distributed power supply can be solved.To this end,relevant scholars have proposed Virtual Synchronous Generator(VSG)technology.This paper takes the micro-grid inverter based on virtual synchronous generator as the research object,and the research contents are as follows:(1)The concept,structure and research status of microgrid are studied.The traditional microgrid inverter control strategies—PQ control,Vf control and Droop control are compared and analyzed,and the virtual synchronous generator is derived.The concept of the VSG research is briefly introduced.(2)Explain the basic principle and implementation algorithm of virtual synchronous generator,introduce the second-order model of synchronous generator as the mathematical model of VSG algorithm,the control structure of the virtual synchronous generator is analyzed,and the virtual governor,virtual excitation controller and VSG ontology model are designed according to the synchronous generator.(3)Modeling the three-phase voltage source inverter,establishing voltage and current double closed loop control and designing the active loop and reactive loop,and analyzing the parameters in the model through the root locus method.Provide a theoretical basis for parameter design.The corresponding simulation model is built in MATLAB.The effectiveness of the proposed control strategy and the correctness of the parameter design are verified by a series of simulations.(4)The fixed moment of inertia and damping coefficient have certain defects for the frequency and power of the stabilized system.To further improve the system performance,this paper proposes a common adaptive inertia parameter and damping coefficient based on frequency deviation and its rate of change.Control strategy can effectively shorten the system transient process.In this paper,the corresponding simulation model is built in MATLAB,which verifies the accuracy of the virtual synchronous generator control strategy and the effectiveness of the proposed adaptive control strategy.