K LYSTRON M ODULATORS C HARGERS FOR CLIC Sklavounou Eleni TE – EPC – FPC

K LYSTRON M ODULATORS R&D O BJECTIVES Propose design solution for the modulators charging sub-system minimizing the grid power fluctuation. Design the control strategy of capacitor chargers for minimum power fluctuation.  Problematic: Grid power fluctuation VS capacitors voltage droop + current and voltage regulation capabilities of the charger + cost + size

Example: If we consider a constant charging current: Charger Power Unacceptable power fluctuation!!!

But if we want a constant charger power: Charging Current Ideal charging current Very high bandwidth charger needed

If we model the capacitor charger as a 2 nd order transfer function: Power Consumption *Ideal case: infinite current bandwidth *Real case: 2kHz current bandwidth

Acceptable voltage fluctuation 5% Acceptable cosφ0.98 Acceptable power fluctuation Still waiting Calculations of fault currents Short circuit impedances of 400 kV transformers I N THE MEANTIME … Industrial survey about the charger (size, prize) Main capacitor bank (type, size as a function of the stored energy) Network specifications according to IEC and EDF

G ET INTO THE CHARGER TOPOLOGY Internal capacitor as a second “filter” to stabilize the voltage at the input of the DC/DC converter. Which are the compromises between the internal capacitance and the bandwidth?

1 ST RESULTS FOR THE GRID ACTIVE POWER For different C int and Bandwidth of the charger

G ET INTO THE DC/DC CONVERSION TOPOLOGY We choose a buck converter in order to profit from the linearity between the duty cycle and output voltage. Verify the accuracy of the created models by comparing the output of the transfer function modeling approach with the output of the equivalent power model, considering the same input. We aim to simplify our analyses, especially when considering several systems in parallel.

B UCK CONVERTER MODEL SIMULATIONS Three “sub-models” (setting Iref): A. Power system model with PI closing the loop (we model the power system as 1 st order transfer function – input: D, output: Ich – and we close the loop calculating the PI parameters for the imposed closed loop characteristics) B. Buck converter represented by1 st order transfer function and closing the loop with PI (no power blocks used) C. Charger as 2 nd order transfer function (which is the above 1 st order in closed loop with the PI)

Current research: Describe the closed loop system as a transfer function and put this transfer function in the simplified transfer function model in order to obtain faster models to simulate several systems in parallel. Status: We still have some difference between the power model and the transfer function based model > We are working on it! What’s next? Power Fluctuation VS Charging Voltage: How can I slow down/speed up the charging of C main in order to reach always the same V ch at the end of each pulse for all the 1638 chargers? PresentFuture

Merci pour votre attention. At your disposal for any questions.