Interharmonic Analysis Model For Grid-connected PV System Considering The Control Strategies

For the power system,to achieve peaking carbon and carbon neutrality targets,the main problem and direction is to build a new type of power system with new energy as the main body.As an increasing proportion of photovoltaic in the power system,grid-connected PV system has brought many challenges to the operation of the power grid,such as power quality issues.The interharmonic generated by grid-connected PV systems is achieving growing concern.The cornerstone for related research is to establish interharmonic analysis model for grid-connected PV system.Therefore,this thesis focuses on the interharmonic analysis model for gridconnected PV system.The main work is as follows:1.By selecting appropriate fundamental frequency,dynamic phasor sequence components(DPSCs)can be extended and applied to the interharmonic analysis.With the transformation between dynamic phasors on dq coordinate and DPSCs,the interharmonic analysis model of grid-connected PV system considering the control strategies is deduced.2.Based on the flutuations of dynamic phasor of a signal consisting of interharmonics,dynamic phasor disturbances(DPDs)and dynamic phasor sequence component disturbances(DPSCDs)are defined.As the frequencies of interharmonics are known,the DPDs model is established with superposition principle,which is derived from the DPSCs model.The DPDs model is used to represent the interharmonic interaction of the converter.Comparing with the DPSCs model,the DPDs model’s order reduce a lot.3.The transformation between dynamic phasors on dq coordinates and DPSCs is derived with consideration of the phase-locked loop(PLL).The DPSCs model of PLL is obtained based on the transformation.Then,grid-connected PV system is divided into several modules and the principles of interharmonic interaction of PLL and each module is analyzed.Consequently,the interhamonic emission characteristics of grid-connected PV system can be obtain in detail.4.Based on the principle of interharmonic interaction,the main components of interharmonics are selected to establish the interharmonic analysis model of grid-connected PV system.The model can guarantee the accuracy and speeds up the calculation at the same time.This thesis establishes an interharmonic analysis model of grid-connected PV system that takes the detail control strategies into account and explores different order reduction and calculation acceleration methods.The research can provide theoretical and methodological supports for the interharmonic analysis of grid-connected PV system.