The Identification Method Research On Control Parameter And Transfer Function Of Photovoltaic Virtual Synchronous Generator

As the penetration rate of photovoltaic power generation continues to increase,the lack of inertia and damping characteristics of traditional photovoltaic power sources and the need to withdraw from operation in the face of low-voltage faults on the AC side have all caused increasingly serious threats to the safe and stable operation of the power grid.The virtual synchronous generator technology and low-voltage ride-through technology proposed to solve these problems have received a lot of research and a small number of applications.In many studies,scholars often care about the function implementation and optimization of technology,but few people care about the application of technology.Actual external characteristics.In view of this phenomenon,the research contents of this article are as follows:First of all,in view of the current state of research on parameter measurement of virtual synchronous generators,based on a typical second-order VSG control method,a non-linear least-squares curve fitting method is proposed in the inverter parallel and offgrid operation modes.The calculation formulas of core parameters are given.Based on off-grid load shedding experiment and grid-connected power step experiment,a comprehensive self-checking comprehensive experimental method is designed.Combining the above curve fitting method and parameter calculation formula can measure the moment of inertia of a typical second-order VSG control algorithm.The specific value of the damping coefficient provides a new method for inverter modeling and control parameter correction.Secondly,on the basis of the VSG control parameter measurement method,a control method for the VSG active-frequency control transfer function overall identification is proposed for the situation where the control strategy needs to be clarified first,and the actual control strategy may be unknown.This method starts from the frequency domain.By measuring the amplitude and phase response of the target object in a specific frequency band and combining a complex curve fitting method,the actual active power can be obtained when the measured object is a black box-The frequency transfer function has higher fault tolerance and universality than the parameter measurement.Finally,in the current research on identification of low-voltage ride-through control strategies,the existing literature is based on laboratory environment verification,and a method for modeling and verifying low-voltage ride-through control of photovoltaic power plants that takes into account DC resistance is proposed.This method is based on a typical low-voltage control strategy,and the least square estimation method is used to identify the control strategy.Aiming at the problem of verifying the identification results with ideal photovoltaic arrays in other people’s research,the equivalent modeling method of photovoltaic arrays was put forward,which accurately restored the characteristics of photovoltaic arrays during field experiments,and provided a more realistic mathematical model for the construction of actual photovoltaic power plants For the exact method.