Research And Application Of Space Vector PWM Rectification Technology In The Heavy Ion Accelerator Power Supply

The power supply subsystem is an important part of an accelerator system,the output indexes of power supplies directly affect the quality of the beam.Although in recent years,the digitization of the accelerator power supply greatly improves its output performance and makes it more easy-using,now the accelerator power supply still has many problems such as low input power factor,high current harmonics,unidirectional power flow,which are produced by the diode rectifier or multi-phase thyristor rectifier used in it.Because of low power factor and high current harmonics,special compensation devices should be added to the general incoming line of the accelerator power supply system to meet the requirement of access to the power grid,but this scenario can’t solve problems from the root at the user side.With the gradual improvement of energy and efficiency requirements of an accelerator,the current falling speed of the power supply is usually higher in the pulse mode,and enormous energy should be transfered out from the magnet load during current falling section,and accompanied by the further application of superconducting magnet,methods,such as increasing the DC capacitor and adding energy discharge units,will be difficult to implement.The PWM rectifier has the characteristics such as sinusoidal current in the grid side,low current harmonics,controllable input power factor and ability of bidirectional energy flow,which provides a feasible solution for the problems above.In this doctorial thesis,the voltage source PWM rectifier is selected as the breakthrough point to start the study on application of PWM rectification technology in the accelerator power supply.On the basis of introducing the common topology of the accelerator switching power supply,the voltage source PWM rectifier is introduced into the accelerator power supply,not only a complete mathematical model is established,but also the control strategy and space vector PWM modulation strategy are introduced,and the process of bidirectional energy flow is analyzed too.After the completion of the theoretical analysis,the parameters of the main circuit of the power supply prototype are designed,and a complete simulation model of the accelerator power supply based on voltage source PWM rectification technology is set up to validate its correctness using the simulation software Simplorer.Finally,the medium power accelerator power supply prototype based on the voltage source PWM rectification technology is constructed,as the hardware of control circuit,the software of the main control device TMS320C28346 DSP and the control interface are developed,which provide a good reference for the application of voltage source PWM rectifier in the field of accelerator power supply.The simulation and test results show that application of voltage source PWM rectifier technology in the accelerator power supply can make it achieve approximate unit power factor operation and sinusoidal current in the grid side,and it can greatly reduce the current harmonics.All the output parameters of the power supply meet the design requirements,and it can solve the energy feedback problem of the power supply during the current falling section in the pulse mode well.The results of this study show that application of PWM rectification technology in the accelerator power supply system is feasible.