l4t bending power converters: ‘ implications of monitoring the current to 5% and 0.5%’ l4 bcc -...

L4T Bending Power Converters: ‘Implications of monitoring the current to 5% and 0.5%’

L4 BCC - 10 Nov 2011David Nisbet

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Porteuse

cmd

GAIN

Mesure_IL_HF

GAIN

I

Kp_I

Kp_Taux_IGAIN

Mesure_Imagnet

LIMITYt

Iref

GAIN

Amortissement_fi l tre_Kv

GAIN

Porteuse1

cmd1Mesure_IL_HF1

GAIN

Kc

GAIN

Mesure_Vmagnet

GAIN

I

Kp_U

Kp_Taux_U

GAIN

GAIN

Amortissement_fi l tre_Ki

Amortissement_fi l tre_Ku

LIMIT

GAIN

Kc1

GAIN

I

Kp_U1

Kp_Taux_U1

Bending Power Converter

• The power electronics and control architecture:

10/11/2011 TE-EPC - David Nisbet 2

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Y

Y

Magnet

DC Inductance

Diodesrectifier

Transformer50Hz-Y

BrakeChopper Capacitors bank

IGBT Hbridge

HF Filter

400V

Output voltage ±450V

Output current ±900 A

Pulse repetition rate 1.11 Hz

Flat-top precision ~100 ppm

From the workpackage:

The same parameters are valid for all the bending converters• (L4T: BHZ, BVT) • (LT: BHZ20, BHZ30, BHZ40)

Controlling the magnet current

• FGC3 in the PSB (Nov 2011)

• For L4 bending: control of arbitrary current function to 100ppm accuracy


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An example of ‘state of the art’

• The current of the LHC main quads and dipoles (50Hz samples):

• Measurements are always subject to sources of noise and perturbations


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756.906 A

756.911 A

30mA

Imeas of

RB (A56, A67)

RQF (A56, A67)

RQD (A56, A67)

The converter interlock architecture


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The converter interlock architecture


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Analog comparison for ‘lower’ performance but highly reliable

Digitise for high performance, but requires software, etc

Converter ON/OFF

The converter BIC interface

• Simple AND of up to 3 conditions to generate a BEAM PERMIT :1. ‘Reliable and robust’ analog threshold validation: ±5% of nominal2. ‘Hi resolution but software’ threshold validation: ±0.5% of nominal3. Power converter state (‘ON’ and ‘NO FAULT’)

• Up to 4 separate PERMITS for each power converter:– For example, allows evaluation of destinations and energy levels


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Only w

hen

need

ed

Monitoring the magnet current

• Example of a scenario for the L4T Horizontal Bending (L4T and L4Z destinations)


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~150ms

Monitoring the magnet current

Typical scenario of information available in the Control Room

• FGC will publish warnings if deviation from a pre-determined performance level is detected (eg 100ppm , 10-4)

– Data can be viewed through CCC alarm monitors– Operator (or control room software) may take appropriate action – Experts will be automatically informed

• Maximum deviation from reference value can be made available to SIS– SIS may inhibit subsequent pulses based on a pre-determined threshold (eg between 10 -3 and 10-4 )

• BEAM PERMIT will be given to BIS if measured value is within ±0.5%– If for any reason a software bug is present, the analog channel will guarantee the BEAM PERMIT is given only if real

measured current value is also within ±5%


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Conclusion

• In an operational environment, we are wary of very tight thresholds affecting equipment availability

– Electromagnetic compatibility, network perturbation

• Signals for the BEAM PERMIT cannot be heavily filtered as fast dynamic response is required

• The power group considers that a ‘Keep It Simple’ approach is the most appropriate method to ensure a reliable and robust BEAM PERMIT interface

– A redundant signal architecture will be maintained for coherence with the BIS architecture– The signal is made available for subsequent treatment by the BIS

• The proposed approach is a compromise to achieve the tight tolerances requested – Analog comparison to obtain a robust permit signal path, but the tolerances must be consequently relaxed (±5%)– Digital comparison to obtain a precise interlock, but this also requires software

• The extensive reporting and diagnostics available from the FGC3 generation of power systems allows a phased approach if deviation from the reference currents is detected

– Intelligent and complementary use of experts, warnings, SIS and BIS


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l4t bending power converters: ‘ implications of monitoring the current to 5% and 0.5%’ l4 bcc -...

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