Advisors: Renee Kohl Dr. Woonki Na Peter Burrmann Dr. Brian - PowerPoint PPT Presentation

Advisors: Renee Kohl Dr. Woonki Na Peter Burrmann Dr. Brian Huggins Matthew Daly 1

Why the electric car?  Reduce our foreign oil dependence  Reduce carbon emissions 2

Outline  Functional Description  Progression of Project  Implementation/Construction  Testing  Results 3

Project Summary  Convert 120 volt AC grid power to the required 51.8[V] DC value to efficiently charge an electric vehicle battery  Discharge battery via Bi-directional converter into a variable load Boost Converter 120V Diode Rectifier DC/DC AC AC/DC PFC Discharging Load PWM Bidirectional Discharging or 51.8V DSP PWM Converter Charging charging? Battery DC/DC 4

Project Goals  Create a PHEV charging system capable of outputting up to 1k[W] of power for the operation of a variable load.  Implement a control system using a DSP for the purpose of driving MOSFET gates  Efficiently Charge a Li-Ion battery using our power electronics system 5

Diode Rectifier Diode Boost 120V AC Rectifier Converter Discharging Load PWM Bidirectional Discharging or 51.8V DSP PWM Charging charging? Battery Converter 6

Functional Description Diode Rectifier  Rectifies 120[V rms ] AC grid power  Precedes Power Factor Correction 7

Functional Description Diode Rectifier 8

Power Factor Correction Boost Diode 120V Converter AC Rectifier PFC Discharging Load PWM Bidirectional Discharging or 51.8V DSP PWM Charging charging? Battery Converter 9

Power Factor Correction  Power Factor  Dimensionless number from 0-1  Ratio of real to apparent power  1 is in unity (ideal)  Passive power factor correction- Capacitor, Inductor  Active power factor correction- Boost Converter 10

Implementation Diode Rectifier / Power Factor Correction 11

Bi-Directional Converter Diode Boost 120V AC Rectifier Converter Discharging Load PWM Bidirectional Discharging or 51.8V DSP PWM Charging charging? Battery Converter 12

Functional Description Bi-directional Converter  To be used in place of the individual Buck and Boost converters’ architecture  Requires more detailed control system 13

Implementation Bi-Directional Converter 14

Functional Description Buck Converter  Drops input voltage based on MOSFET Duty cycle  Half of the Bi- Stage 1 directional Converter Stage 2 15

Functional Description Boost Converter  Boosts input voltage based on MOSFET duty cycle Stage 1  Part of Power Factor Correction  Half of Bi-directional Converter Stage 2 16

Implementation PFC and Bi-Directional Converter 17

Functional Description Interfacing & Protection Circuitry  To be used to sense voltage levels from various locations of the PHEV system, while providing isolation between the DSP and high voltage levels 18

Functional Description Gate Driver  Receives PWM input from DSP to control switching of MOSFETs  Provides enough power to drive the converter’s MOSFETs 19

Functional Description Gate Driver Bootstrap Capacitor Q g = Gate Charge f = Frequency of Operation I qbs(max) = Maximum V bs Quiescent Current Q ls = Level Shift Charge (5nC) I cbs(leak) = Leakage Current V cc = Logic Section Voltage Source V f = Forward Voltage Drop Q Across Bootstrap Diode g = I V LS = Voltage Drop Across Low- g T Side FET s V min = Minimum Voltage Between V = g V b and V s R g I g 20

Battery Boost Diode 120V Converter AC Rectifier PFC Discharging Load PWM Bidirectional Discharging or 51.8V DSP PWM Charging charging? Battery Converter 21

Functional Description Battery  Working Voltage=51.8[V]  14 Cell Polymer Li-Ion  Capacity = 10Ah (518Wh)  40[A] Continuous Discharge Rate 22

Functional Description Battery 23

Implementation Charging Method  Stage 1: Charge Rate: 0.8C  Constant Current Method  Stage 2: 58.8[V]  Constant Voltage Method  Terminate at 3% Rated Current  No Trickle Charge  Reduces battery life 24

Implementation Battery Resistance  Internal Resistance varies with State of Charge  Actively Measure State of Charge  Coulomb Counting  Requires Current Shunt 25

Implementation Measuring Battery Resistance  RC Battery Model  Allows for Matlab simulation  Resistance values are functions of SOC, T, and charge/discharge 26

Implementation Measuring Battery Resistance  Internal Resistance seen − − V V V V oc terminal 3 2 = = from pulse discharge R I I  R int = 108m[ Ω ] Vr 56.530 R 10.910 V1 57.850 V2 57.160 V3 57.720 I 5.181 Rint 0.108 27

Implementation Measuring Battery Resistance 28

Bi-Directional Converter Diode Boost 120V AC Rectifier Converter Discharging Load PWM Bidirectional Discharging or 51.8V DSP PWM Charging charging? Battery Converter 29

Schematics  Buck Converter 30

Calculating gains Fc=500Hz 15dB -150° 31

Psim output voltage 32

Buck Converter PI Control 100 0.1 C281x Constant2 Kp W1 PWM K Ts inverter 10 limit duty cycle PWM z-1 F2812 eZdsp1 Constant Discrete-Time Integrator C281x A .00073 6.12 ADC Gain4 voltage divider ADC1 33

PI Control 34

Schematics  Boost Converter 35

Boost Converter PI Control 100 0.1 C281x Constant2 Kp W1 PWM K Ts inverter 10 limit duty cycle PWM z-1 F2812 eZdsp1 Constant Discrete-Time Integrator C281x A .00073 6.12 ADC Gain4 voltage divider ADC1 36

PI Control 37

Power Factor Correction Boost Diode 120V Converter AC Rectifier PFC Discharging Load PWM Bidirectional Discharging or 51.8V DSP PWM Charging charging? Battery Converter 38

Power Factor Correction  How it works: 39

Schematics Power Factor Correction 40

PFC Testing  Open loop control, 50% duty cycle  80mV out of the op amp can be converted by multiplying by the 1.25 voltage divider, then multiply by 50/4 for the current sensor, and divide by 5 to factor in the 5 loops around the current sensor gives you 250mV which the current  Channel 1: output of current probe is showing. sensing circuitry and op amp input to the dsp  Channel 2: output of current probe 41

PFC Testing  Because the current being measured by the DSP is a rectified sign wave with an amplitude of approximately 80mV, I simulated this in Simulink as the reference current to match. 42

PFC Testing  1: constantly adjusting pwm  1: output of current sensing circuit opamp into DSP  2: current probe measuring current through inductor 43

PFC PI Control F2812 eZdsp1 -K- 100 C281x Kp2 Constant2 uint16 W1 C281x PWM inverter K Ts Data Type Conversion2 A4 In1 Out1 double .00073 -K- limit duty cycle PWM z-1 -K- iir filter1 Data Type Conversion Gain4 Discrete-Time voltage divider Integrator1 Kp1 K Ts A3 double .00073 6.7 z-1 Data Type Conversion1 Discrete-Time Gain1 voltage divider1 15 Integrator2 Constant1 Product A5 In1 Out1 double .00073 2 ADC iir filter2 Data Type Conversion3 Gain2 voltage divider3 ADC1 44

PFC PI Control  Circuit in discontinuous mode 45

Completed Work  Designed full scale system  Controls functioning  Full scale boost converter  Full scale buck converter  Small scale PFC 46

Future  Use system to charge battery  Acquire detailed parameters for battery  Discharge battery through inverter to run a variable load  Implement regenerative braking  Utilize ultra-capacitors for regenerative braking energy storage 47

Questions? 48

Converter Equations Capacitor and Inductor Calculation Equations for Boost Converter Voltage Divider PFC and Bi-Directional Converter Buck Converter 49

Controller Equations 50

MOSFET vs. IGBT 51