1. Modeling a power converter using PSpice
Emmanuele Ravaioli
LHC-CM

2. Modeling a power converter using PSpice
Sources of information about the power converter
Simple power converter (RPHH in RQ4)
Power converter with filter (RPTE in RB)
Modular power converter (RPHE in RQD/RQF)
Voltage-controlled power converter (RPLB in RCBY)
PSpice tips & tricks about power converters
Emmanuele Ravaioli LHC-CM

3. Sources of information about the power converter
General presentation about the PCs installed in the circuits, useful documents, simplified schematic of the circuits
Numeric information about the PC parameters in the LHC equipment catalogue (nominal values) and in the LHC layout database (as-built values)
(range of V and I, R_crowbar, modules)
(example)
(example)
Contact the persons responsible for the PC
Yves Thurel
Hugues Thiesen
Valerie Montabonnet
…etc
Electrical drawing of the PC (further details about the components, types of diodes and thyristors, paths to ground, modules, …)
Datasheets of the installed diodes, thyristors, etc
Emmanuele Ravaioli LHC-CM

4. Simple power converter (RPHH in RQ4) -1
20x free-wheel Diodes
Grounding point
Power converter by-passed by 20 free-wheel diodes which allow the flow of the current after the shut-down of the PC
Emmanuele Ravaioli LHC-CM

5. Simple power converter (RPHH in RQ4) -2
PC modeled by a current source
In Pspice, use an istm component: the current is ruled by an input file which can be modified using Stimulus Editor (within the Cadence suite) or manually editing the .stl (or .ctl) file with NotePad (preferred).
Such a file can be found in the folder of the PSpice project.
Example: \\cern.ch\dfs\Services\cdsusers\eravaiol\RB_A12_PROJECT\worklib\rb_a12_design\psp_sim_1\profiles\transient
.STIMULUS RAMP_2K_0AS PWL
+ TIME_SCALE_FACTOR = 1
+ VALUE_SCALE_FACTOR = 1
+ ( , 0)
+ ( , 0)
+ ( , 2000)
+ ( , 2000)
+ ( , 0)
+ ( 1K, 0)
Emmanuele Ravaioli LHC-CM

6. Simple power converter (RPHH in RQ4) -3
Model of the diode 245NQ015(R)
The PSpice parameters depend on the type of diode/thyristor, on the type of junction, on the operating temperature and on the key parameters present in the datasheet.
Example
Note: Not all the PSpice parameters are mandatory for a good modeling.
Useful links:
Name
Min
Max
Default
Value IS
1.00E-20
0.1
1.00E-14 N
0.2 5 1 2 RS
1.00E-06
100
0.001
IKF
1000
XTI
-100 3 EG
5.51
1.11
0.69
CJO
1.00E-12
6.00E-09 M 10
0.3333
0.48 VJ
0.3905
0.75
0.6 FC
0.5
ISR
1.00E-10 NR BV
150
IBV
1.00E-09
0.0001
0.006 TT
1.00E-16
5.00E-09
5E-09
Emmanuele Ravaioli LHC-CM

7. Power converter with output filter (RPTE in RB)
+ 2 Thyristors
Grounding point
Filter Inductors
6x Crowbars
with Thyristors
Filter Capacitors
Power Converter
+ 2 Thyristors
Grounding point
PC composed of two parallel units
6x Crowbars to allow by-pass of the PC at the shut-down (Thyristor model needed)
Filter at the output of the PC
PC grounded in the positive and negative branches through capacitors
Resistance and inductance of PC cables taken into account (rule of thumb for L: 1 μH  1 μ)
Emmanuele Ravaioli LHC-CM

8. Modular power converter (RPHE in RQD/RQF) -1
5 // 3 // 4 = 60 PC modules in parallel (see next slide) + 5 // 3 = 15 output filters
3 paths for the current after the shut-down
64 Schottky diodes (90% of the current) (model needed)
120 Schottky diodes (10% of the current) (model needed)
3 disc diodes (no current, redundant) (model needed)
Emmanuele Ravaioli LHC-CM

9. Modular power converter (RPHE in RQD/RQF) -2
Each PC module is modeled by an ABM (Analog Behavior Modeling) current source
t <= t_shut-down: I_circuit = I_input
t > t_shut-down: I_circuit = V(D1-D0)/10μ  The PC becomes a short-circuit
Emmanuele Ravaioli LHC-CM

10. Voltage-controlled power converter (RPLB in RCBY)
Input current
(continuous curve)
Calculated reference current
(updated every 80 ms)
Imposed voltage
Calculated reference voltage
Real PC
Fake PC
In order to simulate the discrete behavior of the electronics controlling the voltage across the PC, a new approach is followed. The PC is simulated by a voltage-controlled voltage source, whose reference value is updated discretely (in the example, every 80 ms).
The reference values of the voltage and current of the real PC are calculated by ABM components ruled by functions similar to those used by the PC electronics.
every Dt: I_ref = I_input
V_ref = L_circuit * ( I_ref – I_meas ) / Dt + R_circuit * I_ref )
Emmanuele Ravaioli LHC-CM

11. PSpice tips & tricks about power converters
Pay attention: a current source is very powerful!
If you put a current source in your model, the current in this branch WILL be the one you set.
Example: If you set a PC input current which doesn’t go to zero before the opening of an extraction resistor, you build up a huge voltage across the PC, because the current source will force the current through the resistor!
You cannot put two current source in series: PSpice would try to force two different currents in the same branch.
If you need to put them in series anyway, you can put a fake 1 GOhm resistor in parallel to one of them. This is formally allowed, and won’t change the results.
You cannot put two capacitors in series, or a capacitor in a branch which goes directly to the ground of the circuit.
Again, you’ll need to use fake 1 GOhm resistors in parallel to the capacitors.
Use your fantasy: The same PC can be modeled by means of a current source, a voltage-controlled voltage source, a current source which becomes a short-circuit, etc… With the ABM components you can model anything you need!
Emmanuele Ravaioli LHC-CM