Modeling And Control System Design Of Permanent Magnet Direct-drive Type Tide Power System

In recent decades,with harsh environmental and energy problems,renewable energy grid connected power generation shocks the world,and relevant technologies are flourishing.But since renewable energy is intermittent and uncontrollable,large scale new energy integration brings about significant challenges to the stability of grid,power quality and electricity demand side management.The wind power generation has become a hot spot in the world,and relevant books and articles are also prevalent.However,a systematic,comprehensive and in-depth study on the modeling and control of converter has not been presented,and few accurate and practical design methods are proposed.This paper mainly studies the modeling and control of back-to-back direct drive permanent magnet generating system.Firstly,this paper introduces the principle of tidal current energy conversion and the corresponding hydraulic characteristics of hydraulic turbine.And a practical model of hydraulic turbine is established.Then,in order to simplify the design of control system,the DQ model of permanent magnet motor in rotating coordinate system is derived.Based on this model,the control strategy and the controller design of the double closed loop permanent magnet motor with rotor flux oriented outer loop current loop are analyzed.Besides,on the basis of continuous model of PMSM,the paper further studied the control problems under the discrete domain.By introducing the closed-loop full order state observer,the method of state feedback of modern control design was applied to the stator flux vector control.Second,the paper introduces the process of establishing the AC small signal model of three-phase PWM rectifier in discrete domain.And the SISO model of the control system is derived.Based on this model,the control strategy of double closed loop three phase PWM rectifier based on voltage vector oriented DC is established.In order to observe the influence of control delay on the dynamic and static performance of the system,the root locus of each control loop is studied under different control delays to find the better performance of the dominant poles and the critical frequency.Additionally,by comparing the relationship between the basic vector effective duty cycle of the seven segment SVM switching waveform and the duty cycle of each phase,this paper derives the expressions of space vector modulation(SVM)three-phase duty cycle and three-phase reference voltage.And a simplified algorithm is derived for SVM based on static coordinates without partition and coordinate transformation.Finally,based on maximum power point tracking,the correctness of the proposed method is verified by the united simulation of the converter and the grid side converter.