Search

The present work focuses on modelling of sensor-less Direct Power Control based on Virtual Flux (DPC-VF) for three levels AC/DC converter for wind power system in the case of grid abnormality. As a fact, when an unbalance appears in the grid, the negative sequence affects the quality of Dc-link at the output of the converter and makes deterioration in grid current. In order to improve the behaviour of the converter under grid abnormality, the grid currents and Virtual Flux are decomposed in separating positive and negative sequence using double second order generalized integrator Direct Power Control (DSOGIFLL) then compensating active and reactive powers are calculated according to the control objective and injected in the referencing one. The proposed controller ensures voltage balance in DC-link capacitors by using redundant vectors in a space vector modulation block without needing additional components. In order to test the effectiveness of the control scheme, a numerical simulation is performed using the Matlab-Simulink software. The results prove the validity of the proposed control algorithm.

The growth of wind energy is attributed to the development of turbine size and the increase in number of units in each wind farm. The current modern design of large wind turbines (WT) is directed towards producing efficient, sensitive and reliable units. To achieve this goal, modern turbines are equipped with several devices which are operated with highly advanced electronic circuits. Sensing instruments, measuring devices and control processes of major systems and subsystems are based on various types of electronic apparatus and boards. These boards are very sensitive to the voltage variations caused by abnormal conditions in both the turbine itself and the electric grid to which the wind farm is connected. This paper evaluates wind farm records and proposes a number of methods to overcome such obstacles associated with the design of large wind turbines. Several cases of grid abnormality such as sudden feeder interruption due to the short circuit, network disconnection, voltage variation and circuit breaker opening affecting wind turbines operation and availability are classified and presented. The weight of such impact is determined for each type of disturbances associated with electronic problems in the wind turbine. Wind turbine performance at Hofa wind farm scheme in Jordan is taken as a case study. [Copyright &y& Elsevier]