1. CAPS FID Interface Board Spring Midterm Presentation II Odai Ali James Owens Joshua Roybal

2. Overview Funded under the Future Renewable Electric Energy Delivery and Management Systems Center (FREEDM Center) FREEDM Center goal to develop a demonstration green energy hub on NCSU’s campus Need a fault isolation device (FID) in the green energy hub to act as switch for different parts of the network FID needs a controller 2

3. Problem Statement FID is split into two pieces Fast mechanical switch (FMS) (developed at CAPS) Solid state power electronics (developed at NCSU) Need a controller to bridge the gap of communication between these two systems 3 NCSU Controller CAPS Interface Board

4. FID Goals System Level Support 200 A nominal current, 15 kV ac Switch opening in < 1 ms On-state losses < 10 W Controller Level Support closed loop switch actuation in < 1 ms with verification via feedback measure Read temperature of chamber Read pressure of chamber Communicate state of mechanical switch to parent NCSU controller 4

5. System Updates Temperature and Pressure 5

6. Temperature Serial Interface 6 Simulations conducted in COMSOL for approximation of expected temperature transient times Max of 4 °C over time duration of 10 minutes Later verified to be acceptable update rate through experimental data at CAPS

7. Temperature Serial Interface 7 Update rate decided at one reading per five minutes Device selected as MAX31855 Simple three line serial communication interface to DSP controller Accurate to 0.25 °C

8. Temperature Serial Interface 8 Communication protocol programmed on DSP chip MAX31855 device mounted in breadboard setup to support testing Testing conducted to validate temperature readings as correct PCB layout complete

9. Pressure RS485 Interface 9 Using Pfeiffer Vacuum gauge and pressure display unit Need communication protocol between DSP and pressure display unit

10. Pressure RS485 Interface 10 RS485 chosen as communication Requires hardware conversion to RS232 (supported by DSP unit) Requires software adjustments (vs. standard rs232 input)

11. System Updates Communication 11

12. NCSU Interface 12 Operation Conditions Description Pin NumberNameFunctionStateMIN (V)TYP (V)MAX (V)Output Current 1, 10GND Power GND Power Ground, Connected with Pin 10 2MS_OPENInput High3.55 24mAHigh: MS is open Low 0.824mALow: MS is closed 35VPower 4.8555.151A Pin 3 and Pin 4 are connected. 45VPower 5C_MS_OPENOutput High4.75 24mA Used to open MS. High: Open MS on rising edge; Low: Do nothing. Low 0.4424mA 6OVER_TInput High3.55 24mA High: Over Temperature (T > 35°C) Low 0.824mALow: Normal Temperature 7BAD_VACUInput High3.55 24mA High: Bad Vacuum (p > 10 −5 mbar) Low 0.824mALow: Normal Vacuum 8C_MS_CLS Output High 4.75 24mA Used to close MS. High: Close MS on rising edge; Low: Do nothing. Low 0.44 24mA 9MS_CLSInput High3.55 24mAHigh: MS is closed Low 0.824mALow: MS is open

13. Logic Level Converter 13 NCSU parent board operates at +5V logic level Mechanical switch board operates at +3.3V logic level Requires converter to communicate Tested and integrated

14. System Updates Mechanical Switch Control Loop 14

15. Two Phase Design 15 Strain gauge built into piezo is not operational Conduct controller hardware in the loop (CHIL) setup using the real time digital simulator (RTDS) at CAPS Conduct closed loop CHIL Drive resistor-capacitor model of piezoelectric device Drive actual switch

16. Simulation Setup 16

17. Simulation Setup 17 Digital Interface Controller Board RTDS Analog Interface Simplified Amplifier Model Digital Interface (models NCSU’s Switch Action Interface) Piezo Drive Open Switch Analog Interface Piezo Tx-Function Model Simplified Strain Gauge Model DAC ADC Strain Gauge Feedback Controller Interrupt Ramp Symbol Stream Switch Open Trigger

18. Simulation Results 18 RTDS_Loop_Test Ramp_start75.02 ms Ramp_end76.06 ms Ramp_len1.04 ms Ramp_peak3.0 V Vramp_in Vref_amp Sg_fb

19. Simulation Results - Limit 19 RTDS_Loop_Test _Limit Ramp_start75.02 ms Ramp_end75.14 ms Ramp_len120 µs Ramp_peak3.28 V Vramp_in Vref_amp Sg_fb

20. Simulation Setup – Setbacks 20 DAC operation in test incorrect Output seemed to be non-deterministic Either receive correct output or no output First believed it to be a hardware issue (bad solder joint) No bad joints found in continuity test Through study of data sheet, a wrong assumption was made DAC powered up in incorrect mode and required an additional op-code to function properly Any valid data received from earlier tests was happenstance after the op-code was received randomly via serial input

21. Simulation Setup – Setbacks 21 Incorrect software programming Overflow in for loop counting due to non- singular increment Vramp_in Vref_amp Sg_fb

22. Physical Setup 22

23. Physical Setup – Feedback 23 Controller currently works as open-loop drive for piezoelectric mechanical switch Currently, the only feedback available is time duration for switch to open (1 ms) Two other feedback methods: Additional strain gauge mounted on piezo shell Voltage feedback from piezoelectric actuator

24. Physical Setup 24 Test setup uses open loop: DSP->Amplifier->Representative Piezo Circuit ->Verification Instrumentation First verify test setup using RTDS to generate drive signal in place of DSP Verify correct operation of controller by replacing RTDS with programmed DSP

25. DAC Output Voltage vs. Time 25 Mean voltage: 3.82 V Ramp time: < 2 ms

26. Capacitor Voltage vs. Time 26 Mean voltage: 150.8 V Ramp time: < 2 ms

27. Physical Setup – Lessons Learned 27 Full range output of DAC (3.3 V) did not produce necessary 150 V across piezo device Only produced 134 V Full range operation to 150 V requires DAC output up to 3.7 V Soldered DSP unit to support 5 V power mode Setup works to desired 150 V capability

28. Physical Setup – Lessons Learned 28 Oscilloscope only produced 2 samples during ramp up and ramp down time Hard to determine precise ramp rate using few samples Want to rerun test using smaller sampling time to determine ramp rate limitations of the DSP

29. Physical Setup – Lessons Learned 29 Harnessing to the physical setup was not ideal Devised new cabling strategy for robust connections using header pins on the DSP unit

30. Soldering Problem Board heats up when powered Pin 7 on P4 and pin 6 on P8 read as shorted to the +3.3V supply (at ~4 Ω resistance) Pin 7 on P4 and pin 6 on P8 are internally tied I 2 C I2C_ROM_WP and I2C_ROM_ADD read as shorted to +3.3 V supply (at ~4 Ω resistance) 30

31. Description of Problem 31 +3.3V Supply Pins (Pins 17 and 18) Shorted I 2 C pins (2 and 7) Shorted GPIO pins

32. Steps Taken Determine all intended connections to pin 7 on P4 and pin 6 on P8 using eZDSP manual Determine actual connections to pin 7 on P4 and pin 6 on P8 Extra short found to pullup resistor R9/R10 to +3.3V supply Check resistance value on resistors R9 and R10 Read as 4Ω Remove resistors R9 and R10 then recheck resistance between pads Still read as 4Ω 32

33. Findings Pin 7 on P4 and pin 6 on P8 are shorted to the pullup resistors R9 and R10 internally R9 pads on board are shorted internally R10 pads on board are shorted internally Continuous current drawn through R9 and R10 locations to I 2 C pins I2C_ROM_WP and I2C_ROM_ADD of ~1 A causing thermal shutoff of the voltage regulator (and thus the entire DSP board) 33

34. System Updates Bipolar Operation (Future Work) 34

35. Bipolarity Piezo Drive The piezoelectric actuator used has a full range of operation from -20 to 150 V When driven to a negative voltage Piezo contracts in x-direction, expands in y-direction When driven to a positive voltage Piezo expands in x-direction, contracts in y-direction 35 y x

36. Bipolarity Piezo Drive Negative voltage operation allows for electrical adjustment of contact pressure (and thus, contact resistance) DAC does not support bipolarity operation Drafted options Use digital switch to trigger switch of drive signal polarity sent to the amplifier (would require a voltage amplifier that accepts a negative drive signal) Use DSP to switch polarity at output of voltage amplifier 36

37. Final Demonstration April 14, 2016 37

38. Block Diagram [A] 38 Digital Interface Controller Board Analog Interface Amplifier (Techron) DC PSU +5V Piezo Control (0-5V in 1 ms) Open Switch Piezoelectric Actuator Strain Gauge Amplifier DAC ADC Strain Gauge Feedback Controller Interrupt Ramp Symbol Stream Switch Open Trigger Piezo Drive (0-150V in 1 ms) Shell mounted strain gauge signal

39. [A] Operational Description 1.DC PSU supplies +5V rising edge trigger to controller board 2.Controller board supplies 0-5V ramp to amplifier 3.Amplifier drives piezo open 4.Shell mounted strain gauge signal amplified through strain gauge amplifier to controller 5.Controller triggers switch open based on input strain gauge signal 6.Oscilloscope triggers to show controller output ‘switch open’ signal 39

40. Block Diagram [B] 40 Digital Interface Controller Board Analog Interface Amplifier (Techron) DC PSU +5V Piezo Control (0-5V in 1 ms) Open Switch Piezoelectric Actuator Voltage Divider DAC ADC Piezo Voltage Feedback Controller Interrupt Ramp Symbol Stream Switch Open Trigger Piezo Drive (0-150V in 1 ms) 0-150 V Piezo Voltage

41. [B] Operational Description 1.DC PSU supplies +5V rising edge trigger to controller board 2.Controller board supplies 0-5V ramp to amplifier 3.Amplifier drives piezo open 4.Feed piezo voltage to voltage divider circuit 5.Controller triggers switch open based on input attenuated piezo voltage signal 6.Oscilloscope triggers to show controller output ‘switch open’ signal 41

42. Block Diagram [C] 42 Digital Interface Controller Board Analog Interface Amplifier (Techron) DC PSU +5V Piezo Control (0-5V in 1 ms) Open Switch Piezoelectric Actuator DAC ADC Strain Gauge Feedback Controller Interrupt Ramp Symbol Stream Switch Open Trigger Piezo Drive (0-150V in 1 ms) Software Time Delay

43. [C] Operational Description 1.DC PSU supplies +5V rising edge trigger to controller board (emulating NCSU) 2.Controller board supplies 0-5V ramp to amplifier 3.Amplifier drives piezo open 4.Controller signals switch open after timed delay of 1 ms 5.Oscilloscope triggers to show controller output ‘switch open’ signal 43

44. Questions 44

45. Backup 45

46. Simulation Schematic 46

47. FID Interface Board Block Design 47 Power amplifier: AE Techron LVC 3622 Open Power supplyPower supply (208 V) Thermocouple amplifier Strain gauge bridge/amplifier RS 232 Serial 0-10 V analog Closed Temp Vacuum Spare Thermocouple Strain gauge Vacuum gauge Piezoelectric actuator DSP board (TI CCS for programming) TI DSP TMS320F28335 Display unit Analog Non evaporable getter

48. Gantt Chart (March 2016) 48

49. Gantt Chart Cont. (March 2016) 49

50. Gantt Chart (Nov 2015) 50

51. Gantt Chart (Sep 2015) 51

52. Analysis Algorithm 52 Input strain gauge samples at 30 MHz via ADC Calculate slope of curve at constant data point separation When slope under given threshold, switch is at steady state Using slope method to eliminate different bias levels May need to smooth input data via MA filter to eliminate false slopes

53. Temperature at 100 A (COMSOL) 53

54. Temperature at 500 A (COMSOL) 54

55. Temperature at 1000 A (COMSOL) 55

56. Previous Gen FID 56 There are four main parts in the hybrid FID: FMS: fast mechanical switch AB: auxiliary breaker MB: main breaker MOV: metal oxide varistor Opening procedure of the hybrid FID