Research On Three-phase Rectifier Control Strategy Of Low-voltage And High-current Dc Generation System

Low voltage and high current DC power supply is widely used in ship,energy and industry.The traditional high current DC power supply mainly contains controllable rectifier power supply and high-frequency switching power supply.The controllable rectifier power devices have large power consumption and low system efficiency,while low-voltage and high-current power supply with high-frequency synchronous rectification technology rely mainly on imports and the price is particularly expensive.With the increasing integration of motor technology and power electronics technology,the integrated system of synchronous power generation is developing rapidly in the direction of high-power density,high reliability and high fault tolerance,which provides a more convenient and efficient way for the realization of low-voltage and high current DC output system.This paper presents a new structure of multi-phase permanent magnet synchronous generator with only half turn coil in each phase.It is mainl y composed of a 12-pole and 54-slot synchronous generator and two confluence plates.The surface of the confluence plate is equipped with heat sinks,on which rectifier modules are installed in parallel.Every three stator windings and three-phase rectifier bridge constitute an independent module with integrated process High degree.First,for the modular three-phase rectifier output system,designing the AC-side inductor and DC-side capacitor parameters to meet the dynamic and steady-state performance requirements of the three-phase rectifier system.In order to achieve high power output in parallel with multiple rectifier modules,the system uses layer management to transmit the current sharing information through the CAN bus,and achieve the output current balance of each module.Secondly,the PWM rectifier topology used in the rectifier module of the low-voltage high current DC power generation system is analyzed.A mathematical model described by a switching function in a three-phase stationary coordinate system is established.The relationship between the switch function and the output voltage is obtained by analyzing the models in different switch modes.The mathematical model is transformed into two-phase rotating coordinate system by coordinate transformation.Thirdly,in order to improve the efficiency,performance and reliability of the low-voltage DC power supply,the main focus is on the control strategy.The traditional strategy is to use a linear method to control the non-linear system model.Based on the intensive study of the principle of Lyapunov nonlinear algorithm,this paper optimizes the application of Lyapunov's direct method t o synchronous rectification control.It adds current sharing loop control,forming voltage and bus current sharing double closed loop control,so the output voltage is stable and the current of each rectifier module is same.Because the two control variables solved by Lyapunov's stability theorem are coupled with each other,which cannot guarantee the negative determination of Lyapunov derivative function.This paper proposes a simple decoupling method,which decouples the control variables to ensure the negative determination of Lyapunov derivative function.And the low-voltage and high-current system is stable at the balance point.Finally,in order to verify the validity of the proposed Lyapunov optimization algorithm in rectification control strategy,a simulation model is built in Matlab / Simulink software.The simulation results show that each rectifier module controlled by Lyapunov algorithm has good dynamic performance.When the load changes suddenly,the system can restore the steady state with only 0.02 s,and the output voltage and current overshoot are low in the transient state.With the method of bus current sharing,the current of each rectifier module is basically balanced.In the experiment,a 1/6-winding 360-degree angle synchronous generator integrated DC output system platform is built,and taking the single module dynamic performance and multi modu le parallel disturbance experiment.The experimental results are basically consistent with the simulation,which verifies the feasibility of the proposed control strategy.