| |
The correction magnets in the Advanced Photon Source's storage ring are powered by PWM-controlled bipolar switching-mode converters. These converters are designed to operate at up to ± 150 A. The original current regulator used a polarity detection circuit, with a hysteresis, to determine which IGBT was needed to regulate the current with a given polarity. Only the required IGBT was switched while others were held on or off continuously. The overall IGBT switching losses were minimized by the design. The shortcoming of the design is that the converter's output is unstable near zero current because of the hysteresis. To improve the stability, a new current regulator, using a different PWM method, has been designed to eliminate the requirement of the polarity detection. With the new design, converters can operate smoothly in the full range of ±150 A. The new design also meets tighter specs in terms of the ripple current and dynamic response. This paper describes the design of the new regulator and the test results.
|
|