Development Of Fast Corrector Magnet Power Supply For HALF

Hefei Advanced Light Facility(HALF)is the fourth-generation diffraction-limited storage ring light source project under pre-research in China.The ultra-low beam emittance puts higher requirements on the performance of each accelerator system including the magnet power supply(MPS)system.The quality of the final synchrotron radiation will be affected because the beam orbit may deviate at any time.The electron beam is constrained by the magnetic field determined by the power supply of the magnet.Thus,a fast-response power supply can assist the magnet to correct the beam orbit in real time.However,the performance of the common corrector magnet power supply is not excellent enough to solve the contradiction between stability and response speed.Based on the lattice design and beam simulation of HALF,this thesis is devoting to developing magnet power supply prototypes with fast response and high stability.The advantages of low ripple noise in linear power supplies are irreplaceable.A 300 W bipolar linear power supply prototype using metal-oxide-semiconductor field effect transistor(MOSFET)was presented.The H-bridge structure composed of MOSFETs was designed as the main power topology,but unlike the conventional switching power supply,two MOSFETs were used to change the direction of the output current,while the other two MOSFETs operate in linear amplification state.The high-precision DAC AD5791 was selected to achieve a current setting resolution of 20 ppm.According to the design,the actual prototype was made and the high-precision multimeter Fluke8508A was used to test the performance.The frequency response of the designed power supply can reach 10 kHz and the long-term stability can reach 5 ppm.In addition,the ±10 A rated output power supply can resolve current changes of 0.1 mA.Due to the method to reduce the voltage difference,the heat generation of MOSFETs is reduced,and the efficiency of the power supply is increased to nearly 80%.High-precision switching power supply based on DSP and FPGA with full digital control is popular in current research.However,due to the contradiction between output current ripple control and response speed,the application of switching power supply to fast corrector magnets has limitations.Here a fast response power supply based on Buck cascaded multi-level topology has been designed for HALF.This topology uses three Buck modules in cascade and the 1200 carrier phase shift method.The equivalent switching frequency was increased by 3 times,thereby reducing current ripple.Compared with the topology of three H-bridge cascades,this structure uses fewer high-frequency MOSFETs.The Simulink results and the prototype test results shows that the Buck cascade topology has lower ripple and faster response speed than the conventional H-bridge.Two test platforms based on 8.5-digit digital multimeter and NI-PXI are built for power supply test.Both test methods require an external DCCT and I/V conversion module.The difference is that the digital multimeter has higher accuracy,and the PXI platform has better scalability.The digital control card of the fast corrector power supply is a key factor affecting the overall performance of the power supply.A set of digital control cards that can be applied to both linear power supply and switching power supply is presented.The control card is based on FPGA and ARM core microcontroller.It has the functions of high-resolution PWM generation,high-precision current setting and acquisition.At the same time,the control card is equipped with a 100 Mbps optical fiber interface and a Gigabit Ethernet interface,which meets the real-time communication of the power supply system and the orbit system.The design of the power supplies in the thesis improves the performance of the fast corrector magnet power supply and the test platforms will improve the efficiency and accuracy of power supply testing.The high-performance corrector magnet power supplies will better serve the orbit feedback system and lay the technical foundation for the stable operation of HALF.