R.D. Fernández

Contribution of wind farms to the network stability

This paper presents how wind farms, adequately controlled, can improve the stability properties of a power system. Considerations of modeling of wind farms are presented. Then, the wind farm control laws under normal conditions are presented. Next, other wind farm control laws are added to the first ones looking for damping the system electromechanical oscillations after a network disturbance. These laws are based in the capability of the double fed induction generators of feeding active and reactive powers. Finally, some simulations are shown to support the theoretical considerations

Wind farm control for stabilisation of electrical networks based on passivity

This article presents a control strategy for wind farms equipped with doubly fed induction generators (DFIG) operating in a network with a complex load. As is known from vector control theory, DFIG are able to generate active and reactive powers in an independent way. Therefore, taking into account a unitary power factor, a wind farm control law based on the passivity theory is proposed looking for damping frequency oscillations after a network disturbance. Then, different practical considerations allow to simplify the obtained expression in order to achieve a feasible control law. The last one is added to the normal operating power reference of the wind farm established by a Supervisory Control. Finally, some simulations are shown to support the theoretical considerations.

Wind farm control based on passivity

This paper presents a non linear control strategy for wind farms equipped with doubly-fed induction generators (DFIG) operating in a network with a complex load. First, taking into account an unitary power factor, droop (proportional) and inertial (derivative) classical controls are incorporated by considering a negative load behavior of the wind farm. Then, a wind farm control law based on the Passivity Theory is proposed. As a consequence, the passivity technique proves the proportional and derivative laws plus the passive control as a whole control law which takes into account the non linear nature of the electrical system. The whole control is added to the normal operating power reference of the wind farm established by a Supervisory Control. Finally, some simulations are shown to support the theoretical considerations.

Passivity-based control of energy storage units in Distributed Generation Systems

Distributed generation systems (DGS) has become a promising alternative to meet the growing demand for electricity. The requirements for DGS systems justify the use of new control techniques that ensure stability and can handle the performance of the system. In this sense, passivity based control is a technique that takes advantage of the structure of the system by providing a better understanding of the control law. The main objective of this paper is to evaluate Power Shaping control to regulate active and reactive powers of an energy storage system in order to improve the performance of the electrical grid.

Power-based control with integral action for wind turbines connected to the grid

In this paper, a power shaping control with integral action is employed to control active and reactive powers of wind turbines connected to the grid. As it is well known, power shaping allows finding a Lyapunov function which ensures stability. In contrast to other passivity-based control theories, the power shaping controller design allows to use easily measurable variables, such as voltages and currents which simplify the physical interpretation and, therefore, the controller synthesis. The strategy proposed is evaluated in the context of severe operating conditions, such as abrupt changes in the wind speed and voltage drops.