Project 1: Intelligent Electric Vehicle Charger

ECE-44X Senior project

Sponsor:
PGE

Mentor:
Weimin Tung

Group Members:


1 Project Overview

This project is a battery charger for the Nissan Leaf electric car. The charger runs from a 120V wall outlet, and since optimal battery charging for the Leaf is conducted at 220V, this charger will function as an "opportunity" charger, which means that it is intended to raise the charge on the Leaf's battery when the car is parked for a brief period of time, rather than serve as the primary battery charger.

The charger includes a screen that shows the current status of the charging process. The state of the current used is displayed on the screen, which shows the current draw harmonic values up the the 13th in terms of amps, current harmonics squared, percent of fundamental current, and overall distortion. The screen also shows the power, voltage, and current output level to the battery. Besides displaying information, the screen also allows the user to configure the charger. There are options to change the times when the charger will charge the battery and input to turn on or off the current charging process.

In addition to user input, the charger also charges the battery based on the current state of the power grid. When the grid power is stressed, the frequency will drop below its standard level of 60 Hz. In order to not add further stress to the grid, the charger will stop charging the battery when it senses that the grid frequency is not at an acceptable level. This function also overrides any time of day charging plan programmed by the user.

The description above was derived from the following requirements:

  • The device must have a display and depict the electrical power information during charging process.

The customer requires that the electric vehicle charger have a display of the live electrical output information of the charger. This information will be important in order to determine the stress on the batteries during the charge. The location of the display must be easy to read and be in a location that is easily accessible at all times.

  • Charger must have an accurate display of current harmonics.

All pertinent information about the current drawn must be displayed on the charger. The pertinent information desired are the rms current value, the harmonic current squared, the percent of current harmonic in relation to the fundamental, and the overall current harmonic distortion. The best way to display this information is to have numerical values in a easy to read table that is clearly defined. It would be most user friendly to have the harmonic information shown on the same display as the electrical power information.

  • The charger must be powered from a standard wall outlet.

In order to optimize potential usability, the customer requires the EV charger to be able to operate solely from a typical wall outlet.

  • The device must have an option to start charging at a specified time of day:

The customer requires an option to have the charger begin and end charging based off a certain time. The user should be able to input a time to begin charging and a time to end charging. Once the programmed time to begin charging is reached the EV charger will start automatically and begin charging the vehicle until the end charging time is reached, in which the charger will stop automatically.

  • The electric vehicle charger must be able to stop charging once the power grid is stressed.

The customer requires the charger to be able to read the frequency of the power grid and stop charging once the grid drops below what is considered a stressed grid value. The purpose of this is to minimized power drain on the power network during times in which it is already experiencing strain. While one EV charger does not drain enough power to significantly affect the system, the idea is that if many charging devices do not charge, while the grid is stressed, then it will alleviate strain on the grid and bring it back to an acceptable range. Also, the display will show that the grid frequency is stressed so that the user understands why the charger is not charging.

  • The charger will be designed specifically to charge the Nissan Leaf:

The vehicle chosen for this charger by the customer is the Nissan Leaf. The Leaf was chosen because it is one of the most popular electric vehicles on the market. The charger will have a specifically designed output so that it is capable of charging the Leaf to its specified requirements. It will not be the primary means of charging the Leaf, since optimization of battery charging for this vehicle is conducted at 220/240V, but will be able to operate as an opportunity charger. Meaning that while parked at a location for a brief period of time, this charger would be available to raise the battery state of charge.

  • The electric vehicle charger must be safe to use:

The device will be producing a large amount of high voltage and power so the customer requires that the charger is safe to use by any person. The charger must have easy to read indications to inform the user of high voltage cables, and all electrical wiring must not be readily accessible.

2 Background Research
3 System Requirements and Desired Features
4 Design Solutions
5 Top Level Block Design

5.1 Input Sensors
5.2 AC/AC Converter
5.3 Contactor
5.4 Circuit Breaker
5.5 Output Sensors
5.6 AC/DC Converter
5.7 Microcontroller
5.8 ZigBee Transmitter/Receiver
5.9 PC
5.10 J1772 Connector
5.11 Application Code
5.12 Microcontroller Code
5.13 Enclosure
5.14 Oscillator
5.15 Real Time Clock
5.16 Signal Converter

6 Testing
7 Project Timeline
8 Testing Results
9 Expo Materials

Presentation

References:
[1] Brekken, Professor Ted. "Power Electronics EV Charger." Personal interview. 13 Oct. 2010.
[2] "Nissan LEAF Electric Car." Nissan Cars, Hybrid, Trucks, Crossovers, SUVs | Year-End Sales Event | Nissan USA. Web. 21 Nov. 2010. <http://www.nissanusa.com/leaf-electric-car/index?dcp=ppn.39666654.&dcc=0.216878497#/leaf-electric-car/specs-features/index>.

This project is licensed under <License Name>.[1]

Attachments