Search

Wind energy conversion systems (WECSs) require a suitable control to maximise the power generated by wind turbines independently on the wind conditions. Variable-speed fixed-pitch wind turbines with doubly-fed induction generators (DGIG) are used in WECSs for their higher reliability and efficiency compared to variable-pitch wind turbine systems. This study proposes an effective control algorithm to maximise the efficiency of fixed-pitch wind turbines with DFIGs using particle swarm optimisation control to compensate for the errors in the estimation of the circuit parameters of the generator. The proposed control algorithm generates an optimal speed reference to optimise the mechanical power extracted from the wind and the optimal d-axis rotor current through stator reactive power management to minimise the electrical losses of the doubly-fed generator. The optimal speed reference is provided by a maximum power point tracking control below the rated wind speed and a soft-stalling control above the rated wind speed, while the optimal d-axis rotor current is searched by a particle swarm optimisation algorithm. The proposed control system has been verified by numerical simulations and it has been demonstrated that the energy generated for typical wind speed profiles is greater than that of a traditional control based on a model-based loss minimisation.

This paper considers the method that measures the network-element values for the linear resistive network containing the inaccessible nodes and a network topology that is known and element values that are unknown. Measured data at the accessible nodes are used. Whether all of the element values can be determined from the measured data is dependent on network topology. A discussion of what type of configuration for which element values can be determined is presented. A perfect solution is not obtained when the inaccessible nodes number more than two. A new method of determining the element values is given for the circuits containing two inaccessible nodes. [ABSTRACT FROM AUTHOR]