Research On Model Predictive Control Of Microgrid Inverter With Virtual Inertia

As the hub of energy exchange between large power grids and micro grids,inverters have received widespread attention.The traditional inverter control lacks inertia,and the response speed of the inverter from fault recovery to stable operation is slow.Considering that the Virtual Synchronous Generators(VSG)technology can imitate the operating characteristics of the traditional SG,it has the ability to improve the anti-interference ability of the microgrid,and the Finite Control Set Model Predictive Control(FCS-MPC)has the characteristics of fast dynamic response,this paper combines FCS-MPC and VSG technology to study the model predictive control method with virtual inertia.On this basis,this article improves the above-mentioned control method for the problems of circulating current of parallel inverters and unstable output of inverters under unbalanced grids.This article studies the basic principles and design methods of FCS-MPC,and establishes the predictive model and value function of the voltage-type predictive control three-phase inverter on this basis,and summarizes the advantages of predictive control algorithms.In addition,this paper introduces the basic composition of VSG control strategy,including stator electromagnetic equation,rotor motion equation,governor and excitation regulator,and establishes a mathematical model of VSG control.This paper considers the delay problem in the actual operation of the FCS-MPC algorithm and the defect of the value function,perfects the algorithm,and studies a basic method of model predictive control with virtual inertia.De lay compensation is performed by changing the logic sequence of the algorithm implementation,and the inductor current error is introduced into the value function for optimization,and the power quality of the inverter output is improved.Finally,this paper compares the basic method of model predictive control with virtual inertia and traditional VSG control.The simulation results show that the inverter output has obvious inertia,and the inverter has a faster dynamic response speed during the recovery fr om the fault state to the steady state.This article studies the improved predictive control method for the suppression of circulating currents in parallel inverters.And the condition for analyzing the parallel system to eliminate the circulating current i s that the excitation voltage is equal and the equivalent impedance is the same.In view of the large reactive power sharing error caused by the difference of line impedance,an adaptive virtual inductance is added to the control loop to improve the predic tive control method with virtual inertia.Finally,the RT Box platform verifies that the method can reduce the reactive power balance,improve the stability of the inverter output voltage,and reduce the impact on the system.Research on the improved method of predictive control of grid-connected inverters under unbalanced grid conditions.The three-phase inverter predictive model and value function of the current-type predictive control are established,and the mathematical model of the current-controlled VSG is established.This paper analyzes the reference current under the voltage balance condition of the power grid,and on this basis,studies the reference current command under the unbalanced condition,and improves the model predictive control method with virtual inertia for different reference current commands.Finally,the feasibility of the control method was verified through the RT Box platform.