Optimization Design Of Multiple Virtual Synchronous Generators Control Parameters In Islanded Microgrid

As more and more distributed generators are connected to the power grid through power electronic inverters,the grid is more and more vulnerable to power fluctuations and system faults,and the stability of the power system is seriously challenged,especially for the islanded microgrids.Virtual Synchronous Generator(VSG)simulates the inertia,damping and droop characteristics of the synchronous generator,and can actively participate in the system frequency and voltage regulation when the frequency and voltage of the islanded microgrid is abnormal,which is one of the most important methods to improve the stability and dynamic performance of the islanded microgrid.VSG control parameters are flexible and adjustable,but multi-VSGs in the islanded microgrid interact with each other,thus the optimization design of multi-VSG control parameters is very critical to make the islanded microgrid with multi-VSGs have better dynamic response of frequency and voltage as well as small-signal stability.In this paper,the optimization design method of multi-VSG control parameters in the islanded microgrid is studied and the main contents are as follows:(1)The basic control strategy of VSG is studied.The basic control strategy of VSG is stated,and the small-signal transfer function model of VSG participating in frequency and voltage regulation of the islanded microgrid is established.Based on the transfer function model,the frequency and voltage regulation characteristics of VSG participating in the islanded microgrid are analyzed,then the ranges of control parameters in the power outer loop that meet the requirements of VSG small-signal stability as well as frequency and voltage dynamic performance can be obtained.(2)The optimization design method of multi-VSG control parameters in the islanded microgrid based on particle swarm optimization algorithm is proposed.The full-order mathematical model of the islanded microgrid with multi-VSGs is established and its accuracy is verified.Based on the full-order mathematical model of the islanded microgrid and considering the optimal dynamic response of the frequency and voltage of the islanded microgrid,the particle swarm optimization algorithm is used to optimize the multi-VSG control parameters in the islanded microgrid,which effectively improves the steady and dynamic performance of the frequency and voltage of the islanded microgrid when the load changes.(3)The optimization design method of multi-VSG control parameters in the islanded microgrid based on gradient descent method is proposed.The reduced-order small-signal model of the islanded microgrid with multi-VSGs is established and its effectiveness is verified.Based on the reduced-order small-signal model of the islanded microgrid and considering the optimal damping ratio of the system,the gradient descent method is used to optimize the multi-VSG control parameters in the islanded microgrid,which effectively improves the frequency and voltage dynamic response performance as well as the small-signal stability of the islanded microgrid.At the same time,the characteristics and application scenarios of the two parameter optimization design methods are compared and analyzed.