1. CAPS FID Interface Board 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 green energy hub 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) Solid state power electronics Need a controller to bridge the gap of communication between these two systems 3 NCSU Controller CAPS Interface Board

4. Updates 4

5. Gantt Chart 5

6. Gantt Chart Substantiation 6 Strain Gauge Amplifier pushback Controller and mechanical team working on verifying correct operation of strain gauge Strain gauge comes assembled as a piece of the piezoelectric stack PCB Reorganized as own sub task Not required for testing of individual hardware components Voltage Probe addition Second method for piezoelectric state classification

7. Hardware Requirements and Design 7

8. Hardware Requirements Requirement NumberDescription HREQ-001Custom print PCB to house all hardware HREQ-002One digital input signal to trigger FMS HREQ-003Two digital output signals for FMS state HREQ-004Thermocouple to read chamber temperature HREQ-005Pressure gauge to read chamber pressure quality HREQ-006Strain gauge signal and voltage across piezoelectric element to determine state of switch HREQ-007Electrical connector to feed through to vacuum chamber HREQ-008Power amplifier to drive piezoelectric element HREQ-009DAC to provide waveform to power amplifier from DSP HREQ-010PSU to power interface board and DSP production board 8

9. Hardware Block Diagram 9

10. Hardware Performance Specifications Specification NumberDescription HPSPEC-001Communication between NCSU and CAPS interface boards must operate at no less than one read/write per ms HPSPEC-002Broadcast temperature and pressure reading update rate must be no less than one reading per five minutes HPSPEC-003Bit stream communication to DAC must operate at 9.375 MHz symbol rate (150 MHz bit rate) HPSPEC-004DAC precision of 16 bits per sample HPSPEC-005DAC sample rate capability of at least 9.375 MHz HPSPEC-006Piezo drive amplifier 0-150 V and 0-30 A capabilities HPSPEC-007Strain gauge sampling conducted at 30 MHz HPSPEC-008Strain gauge amplifier output of 0-3.3 V HPSPEC-009Thermocouple sampling conducted at 30 MHz HPSPEC-010Thermocouple output of 0-3.3 V 10

11. Digital to Analog Converter A 16 BIT DAC was chosen over an 8 or 12 BIT DAC in order to reduce noise levels and therefore oscillations in the piezoelectric element. A Parallel DAC was chosen instead of serial due to its ability to achieve the same data rate at a lower clock speed. The 16 BIT DAC and an adapter board was procured. This board allows for the DAC to easily be placed on a breadboard and tested. As a result, the DAC needed to be soldered to the adapter board. 11

12. Thermocouple 12

13. Pressure To read the pressure of the FMS chamber we decided to use the pressure reading from the pressure display. The pressure display outputs through RS485, however our DSP does not have a RS485 port. Therefore a RS485 to RS232 converter was procured. 13

14. Strain Gauge and Piezo Voltage The strain gauge conditioning board is to be determined at this time. In order to determine the state of the FMS the voltage level across the piezoelectric element is needed in addition to the strain gauge reading. While the strain gauge reading allows us to determine if the contacts have stopped moving, the voltage level across the piezo stack will correlate to the distance between contacts. The voltage may potentially be read from the amplifier or sensors placed inside the chamber. 14

15. PCB KiCAD was chosen to create the design for the PCB due to it having several help tutorials and the software being free. The PCB design is still in progress, and location of components may change depending on the corresponding GPIOs used. 15

16. Software Requirements and Design 16

17. Software Requirements Requirement NumberDescription SREQ-001Code library to translate input signal from NCSU into drivable signal output to DAC SREQ-002Code library to read serial data from the pressure gauge display and thermocouple, and analog signals from the strain gauge SREQ-003Code library to analyze strain gauge and piezoelectric voltage readings, determine state of switch, and feedback state to NCSU SREQ-004Code library to interpret and broadcast serial data from thermocouple and pressure gauge amplifiers 17

18. NCSU Signal Interface Signal from NCSU controller ( Input) MS_CTRL: High - Mechanical Switch to open. Low - Mechanical Switch to close. Signals Sent to NCSU’s controller MS_OPEN : High - Mechanical Switch is open Low -Mechanical Switch is closed MS_CLOSED : High - Mechanical Switch is closed Low -Mechanical Switch is open Over Temperature : High- Over Temperature (T > 35°C) Low - Normal Temperature Bad Vacuum : High - Bad Vacuum (p > 10 −5 mbar) Low - Normal Vacuum 18

19. SREQ-001 Drive Signal Using LTC1668 16-bit Digital to Analog converter DSP will communicate with the DAC to create the drive signal Digital Interface: The LTC1668 have parallel inputs and are latched on the rising edge of clock input. DSP will need to provide 16 output signals representing the data bits and a clock. Output is determined by the data bits sent to the DAC DAC formula: IOUT A = IOUTFS (DAC Code/65536) IOUT B = IOUTFS (65535 – DAC Code)/65536 19

20. SREQ-001 Drive Signal Pseudo code Turn DAC clock on vcount=0; Mask =1; While vcount <= DAC Value While data bits to set If ( mask & vcount = mask) Set LSB to high Else Set LSB to low Shift mask left by one bit Continue until all data bits checked Increment vcount Continue until vcount >= DAC value IF close switch signal is detected set DAC value to 0 Turn DAC clock off 20

21. SREQ-002 Pressure display model: TPG 361 Pressure readings will be read from the pressure display via RS232 port using SCI on board peripheral. This is a asynchronous serial communication. The data format will have 1 start bit, 8 data bits and 1 stop bit. Transmission rate: 9600 bps Temperature: MAX31855 Thermocouple Board Output a signed fixed point 14-bit, SPI-compatible, read- only format. Synchronous serial communication. 21

22. SREQ-003 The Switch state will be determined by the voltage level across the piezo and the strain gauge. An analysis will done based on readings from the strain gauge and the voltage level across the piezo. The strain gauge will output the oscillations across the piezo. The voltage level across the piezo can determine the distance between the contacts of the switch which overall determine if the switch is open. 22

23. SREQ-003 23 Strain Gauge Analysis 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 Piezo Voltage Analysis Input voltage Correlate voltage to value in LUT between voltage and contact displacement

24. SREQ-004 Broadcasting Pressure and Temperature The pressure and temperature readings will be sent from a serial data bus. This information will be sent based on our own serial data specification. Sent via serial interface (SPI) Send as two 32-bit IEEE-794 floating point values (binary format) Send as ASCII string More bits to transmit, but readable packets 24

25. Test Plan Revisited 25

26. TEST-001: Thermocouple Reading TEST-001Thermocouple Reading DescriptionThe thermocouple itself and the hardware interface to the DSP need to be tested. Proposed Plan Place an additional verification thermocouple in the chamber (read with a multimeter) Take a reading at ambient Heat the chamber with heater tape for 10 minutes Take another reading Compare the readings on the two thermocouples Pass with error of < 5 % 26

27. TEST-002: Pressure Reading TEST-002Pressure Reading DescriptionThe communication from the pressure gauge display to the DSP needs to be tested Proposed Plan Use the pressure gauge display as a control Take an initial reading Pump the chamber overnight for 12 hours Take another reading Compare the readings on the pressure gauge display and the DSP Pass with error of < 5 % 27

28. TEST-003: Switch Actuation TEST-003Switch Actuation DescriptionThe communication path of DSP -> DAC -> Power Amp -> Piezoelectric actuator needs to be tested Proposed Plan Conduct the test outside of the vacuum chamber (for visual confirmation) Trigger the DSP via a GPIO pin Actuate the switch Verify visually that the switch has moved to 0.5 mm contact displacement with calipers 28

29. TEST-004: Strain Gauge Steady State Classification TEST-004Strain Gauge Steady State Classification DescriptionThe state of the switch needs to be quantified with feedback input from the strain gauge Proposed Plan Actuate the switch Save the strain gauge output and analyze with MATLAB Constrain bound on output slope for when steady state has been reached 29

30. TEST-005: Piezo Linearity Test 30 TEST-005Piezo Linearity Test DescriptionThe relationship between the voltage across the piezoelectric element and the displacement of the contacts needs to be defined Proposed Plan Actuate the switch at 10 V Measure displacement between contacts Repeat the above two steps at 10 V intervals up to 150 V Plot the relationship between voltage and displacement

31. TEST-006: Strain Gauge Steady State Verification 31 TEST-006Strain Gauge Steady State Verification DescriptionThe work conducted in TEST-004,-005 needs to be verified Proposed Plan Actuate the switch Use the oscilloscope to measure the DSP digital pin switch state Verify that the pin is pulled high when the switch is visually finished actuating

32. Code Unit Tests 32 Code Unit Tests DescriptionAll functions in software that have input/output relationships need to be tested Proposed Plan Build function drivers for each written subroutine Use comprehensive test cases when possible (all input/output combinations tested) When comprehensive test is not possible, use either random sampling or equal distribution across possible input values

33. Conclusion 33

34. Goals 34 Design of final subsystem (piezo stack voltage measurement) by beginning of December 2015 Full testing of subsystems of controller by end of 2015 Full PCB integration of design by end of January 2016

35. Going Forward 35 Shift focus to testing strain gauge part of piezoelectric stack In parallel, work on method for measuring piezoelectric voltage Using high impedance voltage divider circuit in parallel with stack (must check that circuit can be built such that decay characteristics of capacitive piezo are left sufficiently unchanged) Using high impedance voltage probes (extra sensors)

36. Questions 36

37. Backup 37

38. FID Interface Board Block Design 38 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

39. Gantt Chart (Old) 39

40. Analysis Algorithm 40 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

41. Temperature at 100 A 41

42. Temperature at 500 A 42

43. Temperature at 1000 A 43

44. Previous Gen FID 44 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