Frequency Control Of Micro Energy Internet With Virtual Synchronous Generator

The rapid growth of renewable energy and distributed generation has promoted the integration of various industries.The demand for building safe and stable Energy Internet is also increasing and the important core of Energy Internet is power system.For an independent micro Energy Internet,the island operation micro grid has the characteristics of limited capacity and size,and micro sources have small inertia,etc.The frequency is easy influenced by load.Although the control method Virtual Synchronous Generator(VSG)overcomes the disadvantages of low inertia of micro grid and can achieve micro grid's primary frequency modulation,but it belongs to difference control which can not guarantee the quality of micro grid frequency when the load increases suddenly.This article designed a frequency control scheme based on control strategy of VSG.The effectiveness of frequency control is verified by simulation analysis which can provide theoretical support for the design and construction of micro Energy Internet.Firstly,this article summarized the concept,structure and research status of Energy Internet and micro grid,briefly analyzed the droop control of microgrid and introduced the VSG control technology.Secondly,this article designed frequency control scheme based on VSG Technology: when the system continuously go beyond frequency limit,the system automatically input an integral segment to form a PI controller with frequency modulation inverter's virtual damping,so the frequency modulation inverter can automatically track for load fluctuation and non-difference control to achieve micro grid's secondary frequency modulation,and small signal equivalent and root locus analysis is used to analyze the stability of the method.Finally,builded a micro Energy Internet simulation model including micro grid,electric vehicles and electric boiler and use the frequency control method in island operation mode to research frequency changes by putting into electric vehicle,electric boiler,etc.The simulation analysis can conclude that the VSG inverters' output by rated power ratio and go beyond frequency limit when the loads increased in island operation,then the frequency modulation inverter switched to secondary frequency modulation to increase output power and output power ratio changed,finally the frequency restored to normal range.The effectiveness of the frequency control is verified.