| Summary: | 碩士 === 高苑科技大學 === 電子工程研究所 === 101 === A wind turbine system, either of horizontal or vertical type, converts wind energy into electricity. Large-scale wind turbines usually have huge caption areas of wind power and therefore, run more economically than small-scale wind turbines. However, due to noise, safety, and space requirements in the residential and urban areas, large-scale wind turbines are not applicable but small-scale wind turbines. For the applications of small-scale wind turbines (< 1 kW) in urban areas, vertical axis wind turbine (VAWT) have some further merits over horizontal axis wind turbine (HAWT) since VAWT is simple in structure, insensitivity to wind direction, lower noise, and etc.
A wind turbine performance can be described by the power coefficient versus tip-speed-ratio (TSR). The optimal power coefficient usually occurs around TSR=2 to 4, which differs from turbine to turbine. However, without any controls, a wind turbine has little chance to run at the optimal point due to the wind speed and loads of the circuit may be varying. Therefore, a maximum peak power tracking (MPPT) strategy is deemed necessary to maximize the power output of a wind turbine at various operating conditions. From literature, different MPPT techniques can be found, including TSR control, optimal torque control, power mapping control, and perturbation and observation searching control.
In this study, the perturbation and observation searching algorithm was applied to a lab-made vertical axis wind turbine to enable the wind turbine performs at around its optimal point. The MPPT control algorithm was fulfilled by an ARM 7 (saying MCU). The wind turbine has been made with three twisted blades of NACA 0015 with a chord length of 15cm. The rotating diameter is 60cm. The maximum power output is about 200W.
A simple testing facility, namely an open-type blowing-down windtunnel, was built for evaluating the effectiveness of the MPPT algorithm. The windtunnel can provide a maximum wind speed of about 7m/s. Experimental results show that with the MPPT control, the wind turbine can maintain at its optimal state at each wind speed examined, no matter what the load (resistor) varies.
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