ECE 445 Wind Turbine Generator System Design and Characterization Contact: Prof. James Allison (jtalliso@illinois.edu), Tonghui Cui (tcui3@illinois.edu) ISE department, ESDL: systemdesign.Illinois.edu

Affiliated Research Project: Improvements to Low-Power Wind Energy Systems Large utility-scale wind turbines are cost effective Increases in size tend to reduce levelized cost of energy (LCOE) In some situations, utility-scale turbines are not practical Small-scale turbines (e.g., 1-10 kW Bergey turbines) have high LCOE. Multi-Year Research Project: Investigate new design and control strategies that could improve LCOE for small turbines, make IP openly available

Strategy: Reduce Tower Cost Through Integrated Structural and Control System Design Structural tower typically comprises ~40% of overall turbine capital cost Must be designed for long life: resistant to fatigue and other failure modes We can control the force exerted at the tower tip (generator torque, pitch, yaw) Tradeoff between energy production and structural health How much can we reduce tower cost through new control strategies that balance energy production and structural load mitigation? What generator torque control capabilities can be made available through candidate low-cost generator systems?

Background: Wind Turbine Components

Project Assumptions We want to capitalize on design synergies between physical and control system elements to reduce LCOE for small-scale horizontal-axis wind turbines (HAWTs) These HAWTs will be used for charging batteries, and will not be grid-connected We assume that a more controllable generator can help mitigate structural loads while maintaining effective power production We would like to design, implement, and characterize a promising generator system architecture (~1 kW) Data from test results will then be used by graduate students to determine impact of generator control capabilities on HAWT LCOE reduction via co-design If needed, a student with mechanical design training may be found to assist with mechanical elements of HIL testbed

Strategy: Generator Field Control Blade pitch control is impractical for small-scale wind turbines (higher rotational speeds, reduced volume available for mechanical components) Permanent magnet generators: Low cost, but limited torque control authority (via charger), and limited range of efficient operating states Generators with a controllable field can better help compensate for the wind speed variation and other factors relevant to power production and structural reliability.

Example HIL Architecture 1: Separately Excited DC Generator Field Control RPM/Torque Charger Separately excited DC generator Battery DC motor Mechanical Coupler

Example HIL Architecture 2: Automotive Alternator Mechanical Coupler DC motor Simulate Rotor + Transmission Excitation field current Field Control DC charging current Charger Battery Rectifier

Project Objective and Expected Deliverables Design a controllable electrical generator system for small-scale (1-10 kW) wind turbine power generation, and test system characteristics in the context of balancing energy production performance and structural loads. Expected Deliverables Specify HIL system architecture details (based on either an alternator or separately-excited DC generator) Select devices for purchase (if commercially available); if any devices needed are not commercially available (e.g., custom field controller, charger, etc.), design them Design the field controller for the reference tracking problem needed for HIL testing (appropriate input trajectories will be provided) Verify overall system design via simulation Lab-scale physical implementation, testing, and characterization of this architecture. Recommendations for possible improvements to system design