Hi, my name is Carmen Ngo. I am a senior majoring in Electrical Engineering and minoring in Math at Union College. This site will be updated with my progress throughout my senior capstone design project.
My senior capstone design project is a Three-phase Pulse Width Modulated AC/DC Rectifier and DC/AC Inverter. My advisor is Professor Luke Dosiek.
Introduction and Background
The burning of fossil fuels has been an issue for the environment for hundreds of years now. Harmful emissions have continued to pollute the air as a result of using oil, coal, and gas as sources of energy. Electric vehicles, which will also be referred to as electric cars or EVs, have become more popular as people are becoming increasingly aware of the long-term effects of the use of fossil fuels. They are an alternative to vehicles that run with an Internal Combustion Engine (ICE), which will also be referred to as gasoline cars. There are advantages and disadvantages to both types of vehicles, but the long-term effects of gasoline cars are far worse than those of electric cars. Electric cars can use electricity generated by solar and wind energy, which do not release dangerous emissions into the atmosphere.
Electric cars have batteries that run on direct current (DC) power, while the motors can run on either alternating current (AC) or DC power. DC motors need a DC to DC converter to step up and step down voltage from the batteries. AC motors need an inverter to convert the DC power to AC. Many internal and external devices such as the radio, windshield wipers, and USB adapters run on DC power, so a rectifier is also needed to convert the AC power back to DC.
The goal of this project is to successfully replicate and understand the power flow in an electric vehicle. This final device will mimic driving and regenerative braking in an electric vehicle.
Design Specifications
The final design of this project will consist of two separate systems. An Arduino microcontroller will control the circuits in both systems. The first system will replicate driving an electric vehicle. Below in Figure 1 is a block diagram of the first system, which uses an inverter circuit.
A 40VDC power supply will be set to an appropriate level based on component ratings. The inverter circuit will convert the DC voltage to three-phase AC voltage. It will be built with six of the same type of transistor. The MOSFETs control voltage. Voltage, current, and power into the MOSFETs should not exceed 60V, 70A, and 230W, respectively. Sinusoidal pulse width modulation (SPWM) will be used to control the three-phase AC voltage output through Arduino code. The input to the AC/induction motor should not be greater than 15VAC, 2A, and 30W. A 12mH inductor and 110uF capacitor will be used to create an LC filter at the output of the inverter circuit to filter out noise and reduce harmonic components. The AC/induction motor should start spinning as soon as power is provided and run continuously without interruption. The DC motor will be controlled by the Sciamble hardware from the University of Minnesota and computer to simulate the mechanical load in an EV.
The second system will replicate braking in an electric vehicle. Below in Figure 2 is a block diagram of the second system, which uses a rectifier circuit.
A computer will control the speed of the DC motor. The DC motor will be coupled to the AC motor/permanent magnet. The rectifier circuit will convert the three-phase AC voltage to DC voltage. It will again be built with six of the same type of transistor. Again, voltage, current, and power into the MOSFETs should not exceed 60V, 70A, and 230W, respectively. MATLAB calculations will determine the PWM to control the output of the rectifier circuit through Arduino code. The input to the DC motor should not be greater than 36VDC, 4A, and 144W. The input to the AC/permanent magnet motor, which operates as a generator, should not be greater than 28VAC, 7A, and 196W. The input to the power resistor should not be greater than 500VDC, 120A, and 140W. A 1000uF capacitor will be used to filter the output of the rectifier circuit due to the larger output voltage. The power resistor acts like a battery that is charging in an EV, so the DC power should be measurable as soon as power is provided to the system, which should continue without interruption.
If there is time, bidirectional power flow will be implemented in both systems.