Research On Resonance Suppression Strategy Of Direct Drive Permanent Magnet Grid-Connected Wind Power Inverter

With the adjustment of energy structure and the upgrading of industrial structure,the distributed renewable energy power generation technology based on clean energy such as wind power and photovoltaic is developing rapidly.In the field of wind power generation,direct drive permanent magnet wind power generation system is widely used because of its simple structure,strong stability and high reliability.As the interface between wind power system and power grid,the control performance of wind power grid connected inverter directly affects the quality of wind power system grid-connected current.LCL filter is widely used in the connection between grid inverters and power grids because of its low cost and strong filtering ability,but the traditional control algorithm that relies on the precise model of the system is difficult to solve the resonance and coupling problems of LCL filter.Because the linear active disturbance rejection control technology(LADRC)is less dependent on the system model,it can simultaneously realize the decoupling and resonance suppression of the dq axis component of wind power LCL grid inverter.Therefore,based on LADRC control theory,this paper studies the current loop resonance strategy of direct drive permanent magnet wind power grid inverter.The main research contents are as follows:(1)The background and significance of this study are described,the resonance mechanism and suppression methods of grid inverters are summarized,and the research status of grid-connected control technology are analyzed.The mathematical model of wind power LCL grid inverters is established,and the filter parameter design,resonant characteristics and resonance suppression methods are analyzed in detail.(2)Aiming at the resonance and strong coupling problems of wind power grid inverters,an improved LADRC current loop control strategy combined with active damping is designed.By introducing correction links into the traditional linear extended state observer(LESO),its estimation ability of total disturbance is improved.After that,capacitive current feedback active damping is combined with the improved LADRC to promote the resonant suppression performance of the system.The tracking performance and disturbance rejection performance of the system are analyzed in detail by frequency domain analysis,and the stability of the system is tested by the Leonard-Chepat stability criterion.Finally,the simulation results verify the effectiveness and disturbance immunity of the proposed control strategy.(3)A novel active damping(FHPF-LADRC)control strategy based on fuzzy adaptive and LADRC is proposed to solve the problem that the impedance variation of power network affects the control effect of system.Firstly,the grid connected current feedback active damping method(GCFAD)and LADRC control combination of high pass filter(HPF)is introduced,and then the fuzzy adaptive controller is introduced into the active damping ring to enhance the ability of active damping to cope with the impedance changes of the grid and improve the robustness of the grid-connected system.The frequency domain analysis method can compare the new active damping control strategy with better tracking performance and disturbance rejection performance,and the closed-loop pole-zero distribution diagram of the system can compare the new active damping control strategy with better system stability.Finally,the simulation results verify the effectiveness and robustness of the proposed control strategy.