Camosun College - EV Drive Team

Electric Vehicle Drive System

Table of Contents

Safety Notice .................................................................................................................. i

1 Introduction ................................................................................................................. ii

2 System Block Diagram ............................................................................................... iii

3 Setup of Hardware

3.1 Gate Driver Board Assembly & Testing ………………………………..... 1

3.2 Inverter Assembly ...................................................................................... 4

3.3 Making Motor and Control Board Connections …..................................... 6

3.4 Cooling System Setup ................................................................................ 7

4 Controller Interface

4.1 CANBUS Interface ................................................................................... 8

4.2 PID Motor Tuning Parameters ................................................................. 10

4.3 Regenerative Braking .............................................................................. 11

5 Troubleshooting

5.1 System Diagnostics ................................................................................ 12

Appendices

Appendix A: Board Diagrams

Appendix B: Measurements for Sample Configuration

Appendix C: Datasheet Information

Safety Notice

The following safety notices and operating instructions provided should be adhered to, in order to avoid safety hazards.

WARNING - This system must be earthed (grounded) at all times.

CAUTION - The system should not be installed, operated, serviced or modified

except by qualified personnel who understand the danger of electric shock

hazards and have read and understood the operating theory and instructions.

CAUTION - If a motor is connected to the output of this unit, the frame should be

connected to the output protective ground terminal provided. Particular care

should be taken to mechanically guard such a motor, bearing in mind that

unexpected behavior is likely to result from the process of code development.

CAUTION - Since this is an open-source project, it is always under development.

Developers must understand the risks associated with operation and modification of a high-voltage system and its components.

1. Introduction

The EV Drive Team 3-Phase High Voltage Motor Control Module provides power interface, recovery and control of a 3-Phase AC Induction Motor (ACIM).

The system relies on the principles of Space Vector Modulation (SVM) PWM algorithms, controlled by a dsPIC30F6010A-based control board, to manipulate the electric field generated by the high-voltage inverter. The main components of the system are shown in Figure 1-1.

The main control board is running a version of the software supplied by Microchip to control the motor. The original version is available from the Microchip website (www.microchip.com) under the name AN908. The EV Drive Team has made significant alterations to this software in order to make the controller more specifically suited to controlling an electric car. The software has also been altered to accommodate PID tuning in a more user-friendly manner. For information on PID tuning please read Section 5.1 “PID Tuning”. It is important that the user be familiar with dsPIC assembly language in order to make changes to the motor control software, but expertise is not necessary. The SVM portion of the software is basically handled as a “black box”. This means that the user does not really need to know exactly how it works. For users who do wish to alter the “black box” there is further documentation available from Microchip under AN908. The main motor control scheme is executed at a higher level in `PIC C' language in a file called ACIM.c. From ACIM.c the user can manipulate almost every aspect of the motor behavior. ACIM.c contains a function called DoControl() which is executed on a time-based interrupt vector. This function is where the user would make alterations to the code to get the motor to perform differently.

The rated continuous output current from the inverter is 200A (RMS). This allows up to approximately 96kW output when running from a 230 to 480VDC voltage in a maximum 30°C (85F) ambient temperature environment. Thus, the system is capable of running a standard 3-Phase ACIM of up to 96kW which is generally enough to accelerate any common car up to highway speeds. The power module is capable of driving other types of motors and electrical loads that do not exceed the maximum power limit and are predominantly inductive. The system has been designed for interoperability amongst different motors. Furthermore, single-phase loads can be driven using 1 or 2 of the inverter outputs. The rated power output level of the inverter is very high and can deliver a fatal shock so safety is very important. The user should read Section 4.1 “First Run Requirements” carefully before using the system.

The Motor Control Module is an integral part of the Electric Vehicle Drive System; however, it is only a part. A proper understanding of the accompanying components (charging system, regenerative system) is required for successful installation and operation of the system. The sections of this manual describe the setup, operation and diagnostics of the Motor Control Module with appropriate references to the other systems and their documentation. There are many parts to the EV project and the system as a whole is very complex, but when the system is broken down into smaller more manageable parts it becomes much easier to understand.

2. System Block Diagram

As seen below in Figure 2-1, the operation of the electric drive system relies on four component blocks. “Block 1” is the dsPIC30F6010a microcontroller, which operates the SVM software to control the optically isolated gate-drive circuit seen in “Block 2.” The gate-drive circuit forwards the control signals to the 3-phase inverter. The inverter is seen in “Block 3,” and provides the 3-phase AC voltage and current by converting its' input DC voltage to AC and driving the motor. “Block 4” is the diagnostics and communications block. This block uses CANBUS communications to provide information to the user about the operation of the inverter and motor. Also, this block is used for initial setup and tuning of the drive system.

Figure 2-1

Block 3

Block 1

Block 2

Block 4

3. SETUP OF HARDWARE

3.1 - Gate Driver Board Assembly & Testing

**CAUTION! IGBT MODULES ARE STATIC SENSITIVE. WEAR A STATIC STRAP WHEN HANDLING.

To control the IGBT half bridges we have chosen to go with a off the self solution, mainly gate driver board assemblies from Powerex. The BG2B-5015 gate driver assembly seen in figure 3-1 provides the control voltages to turn on and off the IGBT switches. All that is needed to control these driver boards is 5 volt TTL for control signaling and a DC supply in the ranges of 12 - 18 volts. With the single DC supply the DC -DC converter provides +15.8 volts to turn on IGBTs and -8.2 volts to turn them off. Boards come bare so assemble with parts from list on the right. When soldering on components ensure that the wire and ring connector at CN2 are soldered on before mounting assembly to the IGBT. Figure 3-1 Slide assembly on to the IGBT module as seen in figure 3-2 and then solder the gate and emitter connections. Attach ring connector from gate driver board to Collector 1 of IGBT module. Figure 3-2

Component List D1, D2, D3, D4 .5 A 1000V Detection diode PN: MUR1100E DZ1, DZ2, DZ4, DZ5 16V 1W Gate Voltage Surge Protection PN: 1N4745 DZ3, DZ6 30V 1W Surge voltage protection PN: 1N4751 C1, C2, C5, C6 82μF 35V Power supply filter PN: FC1V820 C4, C8 150uF 35V Control power filter PN: FC1V151 C3, C7 0-200 pF Adj. Trip time PN: B37979 R1, R2 4.7kΩ, 0.25W Fault sink current limiting resistor R3 4.7KΩ, 0.25W Fault feedback pull-up resistor OP1, OP2 Opto-coupler for fault signal isolation PN: NEC PS2501 CN1 MTA .100” PN: 640457-6 CN2 ¼” Ring Lug Collector Voltage sensing connection PN: 34151 RG1,RG2 3-10 ohm .5 W *PN = Part Number

Gate Driver Testing:

Referring to figure 3-3, make the following connections on CN1. Connect + 15 VDC to pin 1 “VS” Ground to pin 6 “GND” + 5 VDC to pin 5. “VL” Connect pin 4 to a volt meter “FO” Input 1 and 2 are TTL Logic, gate drivers are logic low, meaning gates will be fired when a logic low are applied to IN1 or IN2 Figure 3-3

Make the following measurements referring to figure 3-3. Pull IN1 low and tie IN2 high. In this configuration measure between G1-E1 and G2-E2 expect to see ~15.8 and -8.2 VDC respectfully. FO on pin 4 should read VL + 5 VDC. Pull IN2 low and tie IN1 high. In this configuration measure between G2-E2,G1-E1, expect to see ~ 15.8 VDC and -8.2 VDC Follow this procedure for all IGBT modules and gate driver assemblies.

H-Bridge Testing

Figure 3-4

Testing the modules in this configuration ensures IGBTs and driver assemblies are functioning correctly. Construct circuit in figure 3-4. Connect power sources to gate driver assemblies as in previous test. Set DC Bus voltage to 30 volts Connect LEDs and a 4K7 ohm resistor between emitter 1 and emitter 3. Power up circuit. Operation of circuit: Using IN1 and IN2 from driver assemblies switch on IGBT 1 and IGBT 4. One of the LEDs should come on while the other stays off. Switch 1 and 4 off, Turn on 3 and 2. The opposite LED should be on and the first LED should be off. Follow these steps and test all three IGBT modules in this H bridge configuration. With testing complete we can now move on to building up the inverter module on the coldplate.

The high-voltage inverter module is assembled with the following components and hardware:
Components (3) CM400DY-12F Dual-IGBT Modules (Powerex) (3) BG2B Gate Driver Boards (Powerex) (2) Bus-bar mounted hall-effect current sensors (LEM) (1) Liquid cooled IGBT coldplate (D6 Industries) *ALL SCREWS REQUIRE LOCTITE*	Hardware (16) 6-32 X 3/4” screws (4) 6-32 X 1” screws (6) 6-32 X 1-1/2” screws (8) M6 X 20mm bolts (8) M6 spring-collar lockwashers (8) 6-32 nylon locknuts (16) #6 metal washers (8) #6 metal internal-tooth lockwashers (6) #6 nylon insulating washers (6) 1/2” X 1/4” OD unthreaded metal standoffs (30”) 1/4” X 1/2” copper bus bar Loctite blue (or similar medium-strength threadlocker) Arctic Silver 5 thermal transfer compound Dow-Corning or generic thermal grease
Figure 3-5

3.2 - Inverter Assembly

Seen in Figure 3-5 is the recommended configuration of the inverter. Assembly of this configuration is achieved by following these steps:

Obtain the D6 Industries IGBT Coldplate *NOTE: Lapping the coldplate with 1000-1500 grit wet/dry sandpaper or emery cloth is recommended for the smoothest possible mating surface. With a punch, mark the mounting hole locations for the three Dual-IGBT modules and gate-drive board support bar, ensuring that the mounting holes will not damage the copper tube passes of the coldplate when drilled and tapped. All mounting measurements for example configuration are available in Appendix B. Using a 7/64” drill bit, and #5 tap, drill and tap all mounting holes on coldplate. Using a xx” drill bit, drill all mounting holes in the gate-driver board support bar. *NOTE: The gate-driver support bar can be constructed from stainless-steel or aluminum in any configuration that properly supports the gate-driver boards. With an unused piece of cling-wrap, “tint” the base of the IGBT modules and mounting area on coldplate by applying a small amount of Arctic Silver 5 to each surface and rubbing it in with the cling-wrap using a circular motion. Then apply a modest layer of generic thermal grease on the coldplate mounting surface. Now, place the IGBT modules on their respected mounting locations and fasten them with the 6-32 x 3/4” screws and #6 metal washers. Remember to apply Loctite to the screw threads.

Using the 6-32 x 3/4” screws, washers and lockwashers, mount the gate-driver board support bar on the coldplate. Tighten the screws to the point that the support bar can be adjusted slightly. Mount the gate-driver boards on the IGBTs, making a reliable solder connection on each terminal. The gate-driver boards can now be fastened to the support bar with the 6-32 1-1/2” screws, metal standoffs, washers and nylon locknuts. Once this is complete, the support bar hardware may be tightened (from step 7). *NOTE: This hardware does not apply if using a different gate-driver board support method. Now that the IGBT modules and gate-driver boards are mounted, it is time to drill and mount the copper bus bar, using a xx” drill bit at locations defined in appendix B. The bus bar is fastened using the M6 x 20mm screws and lockwashers. Using 14AWG stranded-core wire and ring terminals connect up each gate driver board CN2 connection to terminal C2E1 of its respective IGBT module. We can now mount our LEM current sensors on the C2E1 sections of bus bar for current sensing on phases 1 and 2 of the inverter (IGBT modules 1 & 2). Note the orientation of the current sensors from Figure 3-5. Finished inverter assembly

3.3 - Making Motor & Control Board Connections

Figure 3-6

The following connections need to be made from the inverter module to the motor control board: Gate driver boards to phase-control header pins on control board. Use the supplied cables, and refer to circuit diagrams for control board header pinout. Bus-bar current sensors on inverter phases 1 and 2 to Hall-Effect header pins. Use the supplied cables, and refer to circuit diagrams for control board header pinout.

Figure 3-7

The following connections need to be made from the inverter module to the motor: Phases 1, 2 and 3 on inverter to phases 1, 2 and 3 on motor. *Be sure to use sufficient gauge cable to support motor current ratings. Depending on the motor being used, recommended wiring configuration may vary. Pay close attention to the manufacturer's recommendations as seen on an example motor nameplate in Figure 3-7.

3.4 - Setting Up the Cooling System

A typical cooling system is comprised of a heat-exchange unit (coldplate), fluid pump, and heat-dissipation unit (radiator). Since the cooling system pump and radiator are application-dependent, it is left up to the user to choose components. This requires calculations for necessary coolant flow and head rate, heat dissipation capabilities of radiator, etc.

4. Controller Interface

4.1- CANBUS Interface

LABVIEW/ CANBUS Motor Control Interface

Human Machine Interface

This module provides an interface from the engine to a Graphical User Interface, GUI, for the user to get and provide information from and to the engine control. The module is complete with a CANBUS transceiver, the MCP2551, a CANBUS controller, a PIC18F4620 microcontroller, and an FTDI USB module to send and receive information from and to the user.

The GUI

The GUI consists of separate pages or tabs that are used to scroll through the displays and input screens. The pages are as follows:

• The Status Page

• The Motor Instrumentation Page

• The Motor Status Page

• The Tuning Page

The “Status Page” shows the status of the connection. This page should be referred to upon USB connection to the main motor controller to ensure proper connection. This page informs the user if the connection is good, or if a reset action should be taken to connect.

The “Motor Instrumentation Page” displays the status of the motor. It contains a shaft speed, RPM, and all the warning and alarm conditions from the motor.

The “The Motor Status Page” contains real time graphs of signals from the motor, flux and torque.

The “Tuning Page” is used in the installation of the electric motor to tune the control of the motor. The installer will use this page to enter the tuning parameters that will affect the motor performance.

USB Connection

1. Open the GUI by double clicking on the icon on your computer desktop.(screen shot)

2. The display will appear with the connection status page open.

Figure 4-1

3. This page allows the user to set the communications protocol parameters. The Baud Rate default value is 115,200kbps, the word length is 8 bits, stop bits is 1, no parity, and no flow control. The device index informs the user which device the serial over USB connection is accessing; this should 0 and does not need to be set.

4. Connect the computer to the module with an A to B USB cable.

5. Click on the RUN button in the top left have corner of LABVIEW to initiate the USB connection and start the GUI.

Figure 4-2

6. When a connection has been established the USB Connection Status indicator will turn green and the device description will be given.

PID Tuning

Figure 4-3

This page allows the user to graphically tune the motor. Refer to section 4.2 for the theory and instructions on how to tune the motor.

Motor Instrumentation

Figure 4.4

4.2- PID Motor Tuning Parameters

Each motor is distinctly different and will require unique tuning parameters. The electrical time constant of the rotor in the motor must be entered into UserParams.h in the ACIM software.

Theory The tuning of a motor response is covered in great detail in many textbooks. In this document we will just cover the specifics for this system. This system uses Proportional, Integral and Derivative (PID) control loops for the torque, flux and speed of the motor. The speed control loop is only used for regenerative braking. The response of a motor is critical to the overall operation of the EV system. When a new motor or a different motor is connected to the Motor Controller circuit board the parameters must be tuned. If the motor does not seem to respond very well to an input, like stepping on the accelerator, then there needs to be alterations to the PID control loops. The proportional gain of the controller determines the maximum output level of the control loop. If the proportional gain is too low then the output of the control loop will never reach the set value of the input. If the proportional gain is too high then the output will begin to oscillate and may become unstable. An ideal output from the proportional stage is to closely follow the set value without any oscillations or ringing when it reaches steady state. The integral stage is meant to reduce the steady state error, but integral gain can introduce ringing and overshoot. The derivative stage is meant to reduce the ringing and overshoot, but derivative gain can introduce steady state error. There is an ideal balance between integral and derivative gain that can be achieved through trial and tuning that will give optimal response.

Tuning Procedure Open the LABVIEW tuning interface and ensure that the controller is properly connected. The interface will prove if it is connected as in Figure 4-2 shown above. Go to the “Tuning” page as shown in Figure 4-3 below. On each slider the value 10000 represents the maximum gain. Begin by increasing the proportional gains of the “Torque” and “Flux” control loops. At this stage the “Torque” and “Flux” control loops can be set to have the same values. Test the motor response for varying levels of gain and view the response on output charts shown in Figure 4-4. When you have found level of proportional gain that causes the torque response to be effective and smooth begin increasing the integral gain of the “Torque” and “Flux” control loops. When you have found level of integral gain that causes the torque response to overshoot and ring begin increasing the derivative gain of the “Torque” and “Flux” control loops. Once you have achieved optimal response you should save your values to a file. An optimal acceleration response can be seen in Figure 4-4 below. The speed control can be tuned to get optimal regenerative braking. It is not likely that integral or derivative gain is required for optimal response; only proportional gain.

4.3 Regenerative Braking

The electric vehicle drive system incorporates the capability to regain energy dissipated by the motor by using a method called Regenerative Braking. This consists of feeding back spent energy through a voltage converting system into the vehicles' battery packs.

1. System Diagnostics

During the stages of motor tuning and troubleshooting, the following areas are available to aid the user in obtaining smooth operation of the electric vehicle drive system: LABVIEW diagnostics (for information on LABVIEW tuning and diagnostics please see section 4.1). Figure 5-1 Space Vector Modulation (SVM) software system variable tuning. Control board header pin test points. Figure 5-2

LABVIEW Diagnostics As previously mentioned, full information about using the LABVIEW system diagnostics is discussed in section 4.1 SVM System Variable Tuning For each application, the motor tuning process will involve modification of SVM code variables (performed by the LABVIEW interface as discussed in section 4.2 of this manual). For more detailed information on modifying code variables, the user should consult application note 908 (AN908) from www.microchip.com. Control Board Test Points In the event there are problems with the motor operation that cannot be resolved with the LABVIEW tuning interface or code modification, there are test points available directly on the system control board (see appendix A, CPU connection pins). Viewing the status of these pins while operating the system may help to diagnose a faulty or improperly configured component. Since these pins represent the pins of the dsPIC30F6010a MCU, the user should also refer to the MCU datasheet for information about these pins (see appendix C for datasheet information).

Appendix A. Board Diagrams

1. Control Board Diagram

2. Control Board Pinout

Position Hall Interface (PHI)

1

V_CC

2

GND

3

Capture/Compare #1

4

Capture/Compare #2

5

Capture/Compare #3

IGBT Driver Connectors (Ph 1-3)

1

V_CC

2

Low Side Fire

3

High Side Fire

4

Fault (Active Low)

5

12 - 15 Volt IGBT Driver Power

6

GND

Quad Encoder Interface (QEI) 1 VCC 2 GND 3 QEI_A (AN4) 4 QEI_B (AN5) 5 QEI Index (AN3) CANBUS Socket 1 VCC 2 CANBUS High 3 CANBUS Low 4 GND CANBUS D9 Connector 1 N/C 2 CANBUS Low 3 GND 4 Fire Enable (Active Low) 5 GND 6 GND 7 CANBUS High 8 N/C 9 N/C ICD 1 Master Clear (Active Low) 2 VCC 3 GND 4 Programmer Data 5 Programmer Clock 6 N/C

Hall Effect Sensors 1 N/C 2 Sensor Voltage Output 3 VCC 4 GND Brake / Acceleration Connector 1 GND 2 AN7 (Brake) 3 AN6 (Acceleration) 4 VCC PFC / Brake Fire 1 Fire 2 GND LCD 1 GND 2 VCC 3 Contrast 4 LCD Data / !Instruction 5 LCD Read / !Write 6 LCD Enable 7 - 10 N/C (Pulled low) 11 DATA 0 12 DATA 1 13 DATA 2 14 DATA 3

3. CANBUS Daughter Board

4. CANBUS Daughter Board Pinout

CANBUS Socket
1	VCC
2	CANBUS High
3	CANBUS Low
4	GND

ICD
1	Master Clear (Active Low)
2	VCC
3	GND
4	Programmer Data
5	Programmer Clock
6	Selectable RB3, RB4, N/C

Serial D9
1	N/C
2	RX
3	TX
4	N/C
5	GND
6	N/C
7	RTS
8	CTS
9	N/C

Appendix B. Sample Configuration Measurements

Appendix C. Datasheet Information

Datasheets

Component Datasheets

Component	Manufacturer	Datasheet
CM400DY-12F IGBT Module	Powerex	cm400du-12f.pdf
BG2B Gate Drive Board	Powerex	bg2b_application_note.pdf
Bus-Bar Current Sensors	GMW Ass.	AN_121KIT.pdf
dsPIC30F6010a MCU	Microchip	dsPIC30F6010a.pdf
Inverter Control Board	EV Drive Team	EV Drive Team Inverter Manual
CANBUS Daughter Board	EV Drive Team	EV Drive Team Inverter Manual

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