Study On Nonlinear Control Of Brushless Doubly-fed Machines

The Brushless Doubly-Fed Machine (BDFM) is a single-frame, self-cascaded induction machine capable of operating in both the induction and the asynchronous mode. BDFM has the robust mechanical characteristics together with controllable power factor, good speed characteristics, a low power converter and diversiform run mode. Therefore it is especially suitable for the AC drive system and generating system of wind power and water power.According to the basic theory and methods of AC motors,studied the structure of BDFM, the operation mode and the steady-state equation,first brief description the basic structure and operating principle of BDFM,analyzes the BDFM current frequency and speed,slip the relationship, indicates that by changing the frequency of the control winding can regulated the motor speed.Introduced four operating mode of BDFM such as Single-fed induction,double-fed synchronous,double-fed super-synchronous and double-fed sub-synchronous.Basis on the steady-state equations,analysis the power flows of the motor,for the BDFM do deeper research foundation.Brief description about the advantages and disadvantages of the three main BDFM mathematical models, by derivation BDFM rotor speed d-q axis mathematical model,established BDFM open loop running simulation model of Matlab/Simulink.For BDFM four operating modes and power operating mode simulation study,the open-loop experiments verification the run open loop characteristics of BDFM,thus revealing the BDFM dynamic and static operating characteristics in different operation modes,verified that changing the control winding power frequency of BDFM can stability adjust motor speed theory.Lay the foundation of the study the control method of BDFM.Analysis the passivity of motor electrical subsystems and mechanical subsystems from the view of energy,design the torque and speed controllers of motor.In order to improve the system dynamic response,reducing its sensitivity to parameter variations,by adding nonlinear damping in the controller,to achieve fast convergence system.Based on Matlab/Simulink to build a simulation model of BDFM passivity control,simulation results show that passive control strategy can fast-track a given speed,good dynamic performance,global stability,and good robustness.According the equations of the voltage, flux and torque of BDFM in rotary coordinate system at synchronous speed,the component of the rotor flux in the control winding was observed with model reference adaptive method. The flux and current of the control winding and rotor speed were respectively controlled by four ADRC. The BDFM could be accurately decoupling controlled by estimating the state variables and their corresponding generalized derivatives with a extended state observer. The simulation model of BDFM was built in Matlab/Simulink environment with ADRC strategy. The simulation results show that the given speed can be tracked fast with ADRC strategy, and be little influenced by vary system parameters. The dynamic response performance of the speed and load torque of BDFM are better. The ADRC strategy is global stability with good robustness.