Booster main magnet power supply, present operation and potential future upgrades Page: 4 of 5
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From Figure 2, power is fed directly to a 12 pulse full
wave bridge rectifier to charge a capacitor bank through a
one quadrant buck converter. IGBT's that have separate
control system are used to convert the capacitor bank
voltage into pulsed DC voltage across the magnets. Since
a total of two stations are required, the total energy stored
per capacitor bank will be 1.2MJ. The required
capacitance for the cap bank per station would be 0.15F at
4000VDC. If the switching frequencies of the IGBT's for
both stations are in phase, the overall ripple at the magnet
will be increased. This ripple can be reduced to a
minimum if the switching frequencies of both stations are
180 degrees out of phase. The peak input power will be
reduced since the magnet peak power is drawn from the
capacitor bank and no power will be re-circulated back to
the power distribution system, as it is done with the
present system. Grounding is only done at one station as
shown in Figure 2 above.
THE CONTROL SYSTEM
There are two separate control systems for the proposed
upgrade of the BMMPS. One is used to charge the
Capacitor bank while the input power is equal to the
magnet dissipated power and the other is used to control
the voltage across the magnet. See Figures 3 and 4.
station, which is equal to 0.15F. Im(t) is the magnet
current as a function of time and Io is the magnet current
during the time of the front porch which is equal to
approximately 200 A. The second control loop, shown in
Figure 4, is used to control the magnet voltage. This loop
uses the voltage reference (Volt Ref) and the actual
magnet voltage (MagVolt), to drive IGBT2 and IGBT3.
Since this is a current regulated power supply, an outer
current loop must also be used, but was not implemented
during the simulation.
After simulating the circuit in Figure 2 used for one
station, the following results were obtained.
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Figure 3. Control System used to Charge the Cap Bank.
Figure 4. Control System used to control magnet
Figure 3 shows the control loop that was used in the
simulation to charge the capacitor bank, while the input
power is equal to the magnet dissipated power. This loop
uses the input power, power reference (Pref), Capacitor
voltage (Vcap) and the Vcaprefnoacitve.
Vcapref noactive represents the capacitor bank C, voltage
reference when only reactive power is drawn for a given
magnet current cycle. An expression for Vcaprefnoactive
was derived and is shown below.
Vcapref _noactive(t) Vo _ [Im(t)2 -I02
V0 is the initial capacitor bank charge voltage, 4000 volts.
L is half of the Booster magnet inductance, which is equal
to 0.0725 H. C is the capacitance of the capacitor bank per
Figure 5. Magnet Current, Magnet voltage, Capacitor
In this simulation the Capacitor bank was charge initially
to 4000V. In this manner the magnet required voltage is
always less than the capacitor bank voltage, see Figure 5.
Figure 5 also, shows the magnet voltage magnet current,
and capacitor bank voltage for a typical Booster Super
Cycle. Note the super cycle length was 4 sec. Figure 6,
shows the power drawn from the capacitor bank, the
magnet power and the power drawn from the power line
for one station only.
Figure 6. Capacitor bank Power, Magnet Power and Input
It should be noted that in such a system the power drawn
from the AC line will be less, since the power that is not
used will be re-circulated in the system to charge the
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Bajon, E.; Bannon, M.; Marneris, I.; Danowski, G.; Sandberg, J. & Savatteri, S. Booster main magnet power supply, present operation and potential future upgrades, article, March 28, 2011; United States. (digital.library.unt.edu/ark:/67531/metadc831913/m1/4/: accessed January 20, 2019), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.