Research On Oscillation Voltage Fluctuation Suppression Strategy Based On Sliding Mode Control In Microgrid

Microgrid can effectively reduce the fluctuation of distributed energy output power,and improving the reliability of power supply.DC Bus Voltage as an important index which can judge the stability of DC microgrid,and it will affect the normal operation of the load,even causing instability of the system when the the voltage is unstable.Therefore,it is important to study the suppression strategy of voltage fluctuations.This paper mainly studies the oscillatory voltage fluctuation,which caused by converter in cascade or parallel,and unbalanced load in system.By design reasonable control method to reduce the imfluence.Firstly,constant power load can cause the output voltage unstable of the front converter,and a sliding mode controller with multipower reaching law is introduced for the converter.Simulation results show that this control strategy can reduce voltage fluctuations and shorten response time.Secondly,on the basis of traditional droop method,adding virtual impedance link to accurate distribution of output power of each power supply,and ignoring the influence of different line impedance.At the same time,voltage feed-forward compensation is added to reduce voltage deviation.Single DC/DC converter using improved sliding mode control method to achieve stability control of output voltage.The effectiveness of this method is verified by simulation experiments.Finally,analyzing the impact of unbalanced load on microgrid.It is pointed out that the negative sequence component appears with unbalanced load well generate the secondary pulsating power on DC side of DC/AC.This pulsating component can spread everywhere in the system,and affect the control performance of converter,power efficiency and service life.The supercapacitor circuit is added for local compensation,by continuous switching of the charging and discharging to cancel the double frequency pulsating component in the bus voltage.Selecting Sliding mode controller to achieve fast tracking of variable reference current and reduce the influence of external disturbance.Theeffectiveness of this method is verified in MATLAB.