Development of Digital Controlled Corrector Magnet Power Converter with a Shunt as a Current Sensing Component

In Taiwan light source (TLS), Bira’s MCOR30 power converter modules are adopted as the corrector magnet power converters, the output is regulated by analog PWM IC that caused nonlinear behavior at zero cross and the adjustment of compensator for different kind of magnet load is inconvenient. To fulfill digital regulation control, the analog regulation IC of Bira’s MCOR30 is replaced by a fully digital regulation control circuit. With plugging the homemade fully digital regulation control card into MCOR30 that the current sensing component is a shunt that save cost of the power converter, the switching losses and output current ripple were reduced and stability of output current is improved. With the fully digital regulation control circuit, the parameters of the compensator for different magnet load are very easy to adjust. In addition, the feasibility and validity of MOSFET switching algorism is simulated with Matlab simulink and the performance of this power converter is verified, the output current ripple of this power converter could be within 10ppm, which is beyond the requirement of current TLS corrector power converter and qualified to be used in the future TPS facility. INTRODUCTION In TLS the corrector magnet power converters under operation are Bira’s MCOR30As, the output current be haves nonlinearly at zero cross with analog regulation control loop inside. The original PWM regulation circuit of MOSFET is replaced by the fully digital regulation control card. The PWM regulation of DSP adopted flexibly control method for better performance of output current and the switching power loss of MOSFET is reduced. The development of this DSP-based digital regulation control card of TLS’s storage corrector magnet power converters is based on the framework of Bira’s MCOR30A converter with a shunt as a current sensing component that could reduce the cost to fulfill the fully digital regulation control. [1,2] Matlab simulink is used to simulate the characteristic of the full bridge construction, the function of compensator and the PWM regulation algorism, and the accuracy of the control policy is confirmed. With the full bridge power stage construction of MCOR30A as the platform, the original analog regulation control loop circuit is replaced with a homemade digital regulation control circuit board, includes Texas Instruments DSP, ADC and gate drives of MOSFETs, the digital regulation control is implemented and the output current ripple is well controlled within ±10ppm that satisfies the specification requirement of TPS corrector magnet power supply. THE STRUCTURE OF CORRECTOR MAGNET POWER CONVERTER The corrector magnet power converter could be roughly divided into five functional sections: Power regulation and L-C filter / high resolution ADS8382 18bitsanalogytodigital converter / high performance DSP TMS320F28335 controller, USB, JTAG, RS232, and Ethernet transmission interface, as shown at figure 1. Figure 1: The structure of corrector magnet power converter. PWM REGULATION METHOD The PWM switching regulation method was programmed inside of DSP controller and DSP could output two kinds of switching pattern, the first one is one arm switching pattern, reduces switching power loss and with a better efficiency; the second one is the pair arms switching pattern, which improves the nonlinear behaviour of power converter at zero cross. Both figure 2(a) and figure 2(b) are operation positive current modes, figure 2(a) is one arm switching pattern and figure 2(b) is the pair arms switching pattern. The switching pattern of positive output current PWM regulation is shown in table1, which Dπ is delay angle of duty cycle regulation. Proceedings of IPAC2012, New Orleans, Louisiana, USA THPPD062 07 Accelerator Technology and Main Systems T11 Power Supplies ISBN 978-3-95450-115-1 3653 C op yr ig ht c ○ 20 12 by IE E E – cc C re at iv e C om m on sA tt ri bu tio n 3. 0 (C C B Y 3. 0) — cc C re at iv e C om m on sA tt ri bu tio n 3. 0 (C C B Y 3. 0)