Research On Control System Of Dual Three-phase Induction Motor Based On Speed-sensorless And A Dual Bridge Type Of Driver Topology

Compared with the traditional three-phase system,multi-phase system can stand high power load with devices which can stand low voltage,and have little torque fluctuations and a reliable system---namely,the redundancy of system.The dual three-phase asynchronous motor in the thesis belongs to a classical multi-phase system,so it owns the advantages of multi-phase system;however,its driving system is usually parallel style.That is to say,when the input power of the DC source is a constant,heavy current will be produced in the DC source to load high-power load.In the thesis,a control system of dual three-phase asynchronous motor with a series dual bridge type of driver topology is presented out.Inheriting the advantages of the traditional mutiphase system,the dual three-phase system will produce less current in the DC source of driving system,althouth it needs a higher voltage,comparing with that with that in the driving system of parallel bridge style.Consequently,the new style can be utilized in certain conditions which needs constrained current while unconditional voltage.A new control strategy on dual three-phase motor control system with a dual bridge type of driver topology is studied in the thesis.When comes to the way of producing Pulse-Width Modulation(PWM),a Novel SVPWM has been extended from the three-phase asynchronous machine control system to the dual three-phase machine control system through double CLARK transformations.Comparing with traditional SVPWM,the Novel SVPWM can realize nearly the same output waveform while it need less code in the program.Therefore,the Novel SVPWM is more convenient.Approximate stator flux-oriented is utilized in the open-loop control---namely,The fixed voltage of q axis in dq rotary coordinate system,Uq,is employed as the fixed voltage to control the open-loop system.Rotor flux orientation has been used in close-loop control.Invariable amplitude principle is rationally employed in the CLARK transformations and phase compensation is used to compensate.The new control strategy proves its feasibility through analysis,simulations and experiments with excellent control effect.In view of the fact that speed sensor is difficult to popularized in certain circumstances,the Model Reference Adaptive(MRAS)theory is employed to estimate the speed of the motor in real time which is used as the rate feedback in close-loop.Stator currents of dual three-phase machine should be measured for estimating the speed.A simulation model based on the new control strategy is established in Matlab/Simulink,which is used to examine the open-loop system,close-loop system and MRAS.A Digital Signal Processing(DSP)and Seven Field-Programmable Gate Array(FPGA)are programmed in the real hardware system to examine the open-loop system and close-loop system of the dual three-phase machine with the new structure and new control strategies in practice.In order to illustrate the effectiveness and feasibility of the new control strategy,another two control systems--i.e.three-phase asynchronous machine control system with Y style of stator winding and six-phase asynchronous machine control system with dual H bridge style driving system are also experimented with loads as comparisons.However,results show that three-phase asynchronous machine control system with Y style of stator winding and dual three-phase machine control system have a weak load capacity.After analysing the control strategy and structures of machines,the load capacity of two systems has been improved through modifying.