Research On Harmonic Interaction Of Multi Direct Drive Wind Turbines Based On RGA

With the rapid development of the economy and society,the growing energy demand and the increasingly serious energy crisis,the development and utilization of renewable energy has become an inevitable trend in today’s world.Wind energy has become one of the most promising renewable energy sources with its advantages of good environmental benefits and low power generation costs.Among the various wind power generation technologies,the variable-speed constant-frequency wind turbines represented by permanent magnet synchronous generator(PMSG)have become the main model of wind farms in recent years due to their advantages of fast adjustment speed,active and reactive power decoupling,etc.Direct-drive wind turbines are connected to the power grid through converters.Due to the presence of the grid impedance among multiple units in the wind farm,harmonic interactions will occur between their converter control systems,deteriorating the power quality of the system and affecting the safety of the wind farm.Therefore,based on the research status of PMSG converter control,damping control and analysis of interaction between units,this paper aims at the negative impact of harmonic interaction between wind turbines on power quality to study on the harmonic interaction between wind turbines in wind farm.First of all,the appropriate control of the PMSG grid connection system in different coordinate systems is analyzed,and the system Norton equivalent model in the αβtwo-phase static coordinate system is selected as the basis for subsequent analysis.In the αβ coordinate system,considering the digital delay of the PMSG converter,suppressing the LCL resonance via active damping from the feedback of additional capacitor current,based on the Quasi-Proportional Resonance(QPR)controller to track the fan input reference current,combined with the wind farm topology,the Norton equivalent model of grid-connected multiple PMSGs is established,the harmonic interaction mechanism between multiple PMSGs in the wind farm is analyzed,and multi-input multi-output transfer function matrix model of PMSG farm is established.Secondly,based on the Norton equivalent circuit of multiple PMSGs,relative gain array(RGA)is introduced to quantitatively analyze the influence law of different control parameters,equivalent grid inductance and number of PMSGs on the harmonic interaction between units in the wind farm.The analysis shows that the degree of interaction between the current control loops of the PMSG converters at different frequencies is different;the harmonic interaction characteristic between the PMSGconverters also changes when the system parameters change.Finally,the Matlab / Simulink simulation platform is used to verify the harmonic interaction between the units and the simulation results are in accordance with the theoretical analysis of the aforementioned RGA principle for the harmonic interaction between units in the wind farm.The multiple PMSG converter control model is built on the Starsim + PXI hardware-in-the-loop experiment platform to verify the harmonic interaction characteristics between the control loops by experiments.The research results provide a theoretical basis and experimental verification for the analysis of harmonic interaction characteristics between units in the direct-drive wind farm using the QPR controller in the αβ coordinate system,at the same time provide guidance for optimizing the power quality of grid-connected wind power and provide theoretical support for further research on the harmonic interaction characteristics between different types of wind turbines in the hybrid wind farm,and between the wind farm and the DC system.