Ling Zhao, Mohammed Nihar, Nabil Hasan
supervised by Dr. David Xu
The Small Wind Energy Converter for Smart Home consists of a three-phase rectifier circuit in conjunction with a grid-tied single-phase inverter, able to produce a rated output power of 500W with a total grid current THD of less than 5%. The converter system efficiency is rated at 92%. The front end of the overall system is a small wind turbine, which captures variable speed from the wind to generate the resulting power to the Permanent Magnet Synchronous Generator (PMSG). The three-phase PMSG with dual windings produces the input voltages for the converter, which possesses a unique control scheme that detects variable wind speed operation with Maximum Power Point Tracking (MPPT). This feature is able to optimize power capture from a wide range of wind velocities, which is fed into the PI Controller.
The selected rectifier topology has low cost, low power loss, and simple control that allows easy capturing of zero-crossing detection from three-phase input voltages and consequently generate gating signals with specified firing angle. The rectifier circuit consists of two sets of three-phase full bridge rectifiers and three thyristors. When the thyristors are turned off, the two rectifier bridges operate in parallel with each other. The output voltage is equal to the generator line-to-line voltage, VL-L and the output current, Io is the sum of all thyristors. When the thyristors are turned on, the rectifier bridges are cascaded and the output voltage, Vdc equals the sum of the line-to-line voltages, VL-L from the rectifier. With a built-in current sensor in the rectifier circuit, the resulting DC current and voltage are accurately regulated for a smooth PI controller operation. The grid-tied single- phase inverter, which receives the DC voltage and current through a high voltage DC-link capacitor, uses uni-polar pulse width modulation (PWM) scheme to correctly produce AC fixed voltage and frequency. Simulation of the overall small WECS was performed in MATLAB Simulink and the rectifier circuit board was successfully implemented. The converter is controlled using Texas Instruments (TI) DSP LF2407A Controller which is an economical, flexible and suitable one for our application.
Project targeted applications: Alternative energy source for Smart Home, Power source for public street lighting, Home appliances