Collegiate Wind Competition 2020

Competition Purpose:

According to the U.S Department of Energy's (DOE) Wind Vision report, wind energy could supply 20% of the nation's electricity by 2030 and 35% by 2035. As more wind energy is incorporated into the U.S. power generation mix, qualified workers are needed to fill related jobs at all levels. The Collegiate Wind Competition (CWC) is organized yearly by the DOE as a challenge for students to design and build a micro-scale non-grid-connected wind turbine, and in the process, become curious innovators in this exciting field. Our team, Booster Pack, is tasked with building the DCDC converter system for the wind turbine.

Sponsors:

Dr. Venkata Yaramasu & Mr. David Willy

Mentor:

Jason Foster

Team Members:

Nigel Grey, Humoud Abdulmalek, & Mohammed Almutairi

Website last updated: 5/1/2020



Project

Description

In response to the DOE and National Renewable Energy Laboratory's (NREL) annual Collegiate Wind Competition, our Capstone project is to design a DCDC converter system within a micro-scale wind turbine. Specifically, we have decided to explore a synchronous boost converter topology for our system. Thus far, the project has manifested itself with four prototypes: A synchronous boost converter Simulink model, a boost converter with proportional-integral (PI) control Simulink model, and two boost converter breadboard circuits. Our final product will be a model of effective and reliable wind power generation (in a miniature form). Wind turbines have been converting the kinetic energy of the wind into electrical energy since 1887. Naturally, there is a long lineage of prior art leading up to our task of designing the power converter component of this year's micro-scale wind turbine. This project promotes an optimization of current wind energy turbine systems by reducing the overall voltage drop and subsequent power loss over the system as a whole. This is accomplished by utilizing the synchronous converter configuration, where two MOSFETs are used, rather than a MOSFET and a diode. In addition, our design includes two boost converters in series, to increase power generation at very low cut-in wind speed. Apart from NREL aiming to ensure the availability of reliable energy in the country, its aspiration is to guarantee a clean environment by promoting the adoption of renewable energy. Our Capstone project aligns with NREL's goal, with the potential of developing new optimization strategies to advance the technology one the most appealing renewable energy source--wind power.

Depiction

A wind turbine turns wind energy into electricity using the aerodynamic force from the rotor blades. When wind flows across the blade, the air pressure on one side of the blade decreases. The difference in air pressure across the two sides of the blade creates both lift and drag. The force of the lift is stronger than the drag and this causes the rotor to spin. The rotor connects to the generator, which ultimately translates aerodynamic force into electricity. As seen in the block diagram above, the generator output is in the form of a three-phase signal, which is rectified into direct current through the ACDC block. Next, a DCDC converter system is used to create a stable power output on the "load" (the resistor in the block diagram). In grid-connected wind energy systems the load is much more complex (a power grid rather than a single resistor), but for the scope of this project, this simple block diagram sums up the task at hand.

Key Tasks

Our work has manifested in a printed circuit board (PCB) that spans most of the block diagram above, from the generator output to the load. In parallel, we are working on programming all control state machines, and soldering our PCB in Dr. Yaramasu's lab. This semester marks a more collaborative phase of the project, where we work with the mechanical engineering teams as well as the other electrical team to begin integrating all of our sub-systems into one turbine. It has been an exciting (and challenging) journey so far, and today brings a new challenge as the COVID-19 pandemic has forced our team to have less in-person interaction for the remainder of the semester.

The key tasks we have accomplished so far are as follows:

  • Research DCDC converter theory and application
  • Study this year's CWC competition rules and requirements
  • Choose a DCDC converter topology for our design: multi-stage boost converter
  • Design and simulate our DCDC system
  • Design a PCB that integrates the ACDC system with our DCDC system

Milestones

Our project milestones from August 2019 until now:

  • Literature review: DCDC converters
  • Initial prototype findings for:
    • Simple boost converter breadboard circuit
    • Synchronous boost converter simulation
    • Proportional Integral (PI) control boost converter simulation
  • Our Feasibility Report covers the milestones above in greater detail
  • Finalized our system design as seen in this schematic
  • Purchased all necessary components (we are still well within our budget!)
  • Designed and printed the PCB (as seen in the figure above)
  • Successfully implemented a physical PI-controlled boost converter circuit
  • Presented our progress before spring break
  • Adapted to the competition and university adjustments due to the new coronavirus
  • Finished all technical documentation and prepared a final report for the competition
  • Presented at UGrads
  • Presented our final product

Tools

  • Hardware
    • Multimeter: for all circuit measurements
    • Oscilloscope: duty cycle verification
    • Arduino Uno and Mega microcontrollers: for voltage signal output/input, and control algorithms
    • Printed circuit board with a variety of MOSFETs, diodes, inductors, capacitors, resistors, LEDs, current sensor IC, and LM555 IC
  • Software
    • Simulink: block-level Arduino programming and circuit simulations
    • Altium Designer: PCB design and layout
    • Arduino IDE: C++ programming interface for the microcontroller

Design Decisions

So far we have designed this circuit with three design goals in mind: minimum voltage drop from three-phase in to DC out, low operating voltage, and stability at the point of common coupling (PCC). To accomplish these goals (and anticipate some degree of failure) we added in some modularity to our circuit. Please reference this schematic for context. First, we are using a synchronous boost converter (two MOSFETs instead of a MOSFET and a diode) to minimize the voltage drop across the second converter. If this causes any programming errors, we added in two contacts to bypass the second MOSFET with a diode if needed. Second, we used two DCDC converters in series to minimize the time it will take to power on the Arduino. The first converter is operated by a LM555 timer circuit (which will start operating at approximately 2V as opposed to the 6V needed for the Arduino Mega), which will quickly step up the initial voltage to power on the Arduino. If this first stage is unnecessary given the generator's efficiency, we added in a hard-wire bypass on the PCB. Lastly, we are incorporating PI control in the second stage boost converter operation to provide a constant voltage at the PCC across the load. This algorithm is currently working, so there is no need for a contingency plan built into our design.


Testing

Testing and power quality measurements of the PCB with all soldered components was to take place immediately after receiving of the PCB from the manufacturer if the project were able to continue. LEDs were integrated after each stage of conversion within the circuit to provide visual feedback to the tester, and an oscilloscope would be used to provide exact measurements per the CWC2020 rules and requirements. The design featured the ability to change the capacitance values to decrease noise and increase signal integrity. Due to the modular capacitance and closed-loop control, additional filtering techniques would not likely be needed. The generator output would be tracked with the use of a dynamometer throughout this testing.

Challenges

The main technical challenge we faced was in transition between simulated circuits to physical circuits. The real world is much less ideal than the simulated world, which provided many learning opportunities throughout this project. The PI controller was the main challenge in this regard, though once it was implemented successfully, the real-world data was surprisingly consistent with the simulated data. The final challenge would have likely been managing a consistent power supply for the Arduino when connected to the turbine.
Our design relied on one big Simulink module export. This allowed us to avoid writing a C program from scratch, that would run all of our modules in parallel--a very difficult and time-consuming task. Dr. Yaramasu recommended this method of leveraging the embedded coder feature in Simulink to directly flash a program to the Arduino. The main challenge with the Simulink export was learning the coding environment, though once we gained familiarity, we successfully flashed the Arduino.


Final Product

Our final product thus is a DCDC converter system that will work to remove challenges faced by the current turbines in place. We have made use of two MOSFETS unlike what is usually in place- one MOSFET and a diode. The converter is in form of a PCB which has two boost converters connected in series in order to utilize the synchronous converter configuration which will in the long run reduce the time taken to power the Arduino. The first converter is operated by a LM555 timer circuit which will start operating at approximately 2V as opposed to the 6V needed for the Arduino Mega. This will then quickly step up the initial voltage to power on the Arduino. If this first stage is unnecessary given the generator's efficiency, we have added in a hard-wire bypass on the PCB. Finally, we are incorporating Proportional Integration control in the second stage boost converter operation to provide a constant voltage at the PCC across the load. This algorithm is currently working, so there is no need for a contingency plan built into our design. The following is a picture of the completed PCB that is awaiting soldering. The main benefit of this design is that the converter reduces the overall voltage drop which subsequently leads to power loss across the whole plant. The reduction of voltage drop realizes an optimization of the wind energy as an alternative source of power. The converter is also beneficial in providing a stable power output to the resistor. Using wind energy is an advantage to the environment as there is huge reduction in pollution if not completely abolishing it. Unlike nuclear sources of energy, wind energy does not produce nuclear waste which is usually very hazardous to the environment and animals. This design is applicable in any micro-scale wind turbine that translates aerodynamic force into electricity. This electrical energy can then be connected to the grid for commercial use or otherwise personal use. The electricity can also be used to run motors used to pump water from boreholes to be used by small villages and homes. Towers can also install windmills to act as an alternative source of power after power generated from the turbines has been stored.


Design

simulink

Our Team

Nigel Grey

ng474@nau.edu

Mohammed Almutairi

mma559@nau.edu

Humoud Abdulmalek

ha434@nau.edu