Power management supervisory control algorithm for standalone wind energy systems

Being natural and renewable, the wind is a valuable energy resource. Standalone off-grid wind systems cannot simply extract the maximum power at all times due to energy storage limitations. As a result of the limited energy storage, wasted surplus wind power is directed to an energy `dump´ known as a `dummy load´ and the power is dissipated as heat. Therefore, the challenge for standalone wind systems is to efficiently extract the maximum power from the wind when necessary, and reduce the energy extraction - as dictated by the energy storage mechanism - to minimize surplus of energy. By regulating the power output as necessary, the amount of wasted energy and heat dissipation requirements of the energy dump mechanism will be reduced. This paper proposes a power management supervisory controller that autonomously switches between an adaptive MPPT mode and a power limit search (PLS) mode to regulate the wind energy extraction. MPPT is used when the wind speeds result in maximum power levels that are lower than the desired power level. The memory based adaptive MPPT uses the internally captured atmospheric information to detect wind speed change and extract an equivalent of the turbine´s tip speed ratio (TSR) parameter. The PLS is used whenever the power level exceeds the desired power and the MPPT is activated when the wind speed has decreased and no surplus power is detected. The functionality of the power management controller has been verified through simulation. The controller was able to successfully regulated the output power and exhibited smooth transitions between the MPPT and PLS.