Hysteresis Effect in Operation of Small Wind Power Generators
Mathematical models of operating of horizontal-axis and vertical-axis wind turbines (HAWTs and VAWTs) are considered describing both aerodynamic load and electric generator. This model allows describing steady regimes and transient processes. Using the model, the hysteresis phenomenon is described arising during change of the external resistance in the electric circuit. It is shown that the preferable working regimes of the devices belong to the range of external load where the hysteresis effect appears.
Parametrical Analysis of the behavior of an Aerodynamic Pendulum with Vertical Axis of Rotation
Parametric analysis of the behavior of an aerodynamic pendulum is carried out, motivated by the study of a small wind power generator with a vertical axis. A mathematical model for the free rotation of this pendulum is constructed, leading to a system of nonlinear ODEs and transcendental algebraic equations. A qualitative analysis of the phase portrait is carried out: all equilibrium solutions are found, their stability is studied, characteristics of a stable rotational regime are determined; and domains of attraction for equilibrium solutions and for the rotational regime are also found. The mathematical model is used to study the operational regimes of the system “wind turbine + generator”. Estimations of the trapped power as a function of the external load in the circuit are obtained; optimal values for the power and the load are found. A pitch angle control mechanism is proposed in order to increase this power.
Secoiridoids from Olea europaea
Abstract Three new secoiridoids have been isolated from the leaves of Olea europaea along with the previously reported. The compounds were identified by spectral means.