Research On Inverter Active Damping Based On Fractional Notch Filter

As an important interface for the distributed power generation unit to connect to the power grid or load,its performance has an important effect on the stability of the system and the quality of output power.The LC or LCL filter can improve the attenuation of the pulse width modulation switching harmonics,but it is necessary to use appropriate damping methods to eliminate resonance peak.In this paper,independent inverter and grid-tied inverter are used as research objects,and zero-phase notch active damping methods are used to suppress resonance peaks.When the power grid is disturbed or the parameters are changed,it is easy to cause the notch frequency point to change,resulting in failure to accurately align the resonance peaks.This paper proposes a fractional-order zero-phase notch filter method,which can set the notch frequency at any frequency.First,the passive damping method and the active damping method of resonance peak damping are introduced.From the mechanism analysis of active damping,the active damping method based on filters is introduced in detail.Among them,the active damping method based on the zero-phase notch has the advantages of zero phase and does not require a high-precision sensor.However,due to the influence of system disturbance or parameter changes,the center frequency point of the notch and the resonance frequency point of the LC or LCL filter may appear to be misaligned.Then,in view of this problem,the application principle and implementation method of fractional zero-phase notch are proposed.In the independent inverter model,the stability of the RC controller based on the zero-phase notch method and the harmonic suppression performance formula are derived.Because RC has the disadvantage of poor dynamic response,the PIMR control algorithm is used in the grid-tied inverter model,and the performance analysis of the PIMR controller based on the zero-phasenotch method is given.In this paper,two models of independent inverter and grid-connected inverter are applied respectively.The fractional-order zero-phase notch method with finite impulse response FIR filter isused to implement active damping,which can extend the order of the notch filter from an integer to fraction.In the independent inverter system,detailed parameter design of the RC controller is given,and experiments are performed under no-load,linear load and non-linear load.In the grid-connected inverter system,the principle and parameter design of PIMR controller are given,and the comparative experimental diagrams of integer-order and fractional-order zero-phase notch are given.Simulations and experiments prove that the proposed fractional-order zero-phase notch method can achieve widerstability margin,smaller tracking error,and lower total harmonic distortion.