Harmonic Stability Analysis And Impedance Adaptation Technology Of Renewable Energy Power System Based On Equivalent RLC Circuit

The large-scale application of power electronic converters in renewable energy power system forms a complex multi-scale high-order nonlinear network,which would easily cause harmonic instability in a wide frequency range,distorting the stability and power quality.Large-scale grid-connected power electronic devices cause new challenges to the stable operation of modern power grids.For this reason,academia has carried out extensive discussions and in-depth researches,and proposed the active damper technology which performs as a specific impedance at the PCC to improve the damping of the system.However,the active damper technology lacks the quantitative design specifications,and can only give an approximate range through stability criteria.Based on existed researches,this paper proposes a one-port impedance model built on the location of the harmonic source to reflect the resonance mechanism of the system.And this paper proposes an approach to quantify the extent of resonance by equivalent a power plant impedance model as RLC circuits model on the resonance frequency.At the same time,to improve harmonic stability,a power electronic device called active damper has been developed.This paper proposed quantitative design rules of active damper based on previous analysis by a detailed mathematical derivation.The main research work of this paper is contained in the following aspects.In order to analyze the resonance problem of the renewable energy power system,the model of the renewable energy power system is built since considering the time delay and frequency coupling,and the model is simplified to extract the key parameters.A oneport impedance model and equivalent RLC circuit model are proposed,the resonance mechanism of the renewable energy power system is discussed in detail,and proposed a quantitative description indicator of the resonance extent.The quantitative design rules of the virtual impedance parameters of the active adapter are proposed to solve the problem that these existing researches can only ensure the stability of the system without determining whether the damping is sufficient,redundant,or deficient.RTLAB HIL simulation platform and laboratory hardware experiment platform was built to reproduce the system instability resonance and harmonic amplification phenomenon,and the proposed methods were verified through simulation and experiment.