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The suitability of distributed power generation systems working at medium and high capacity as it is the case of wave power generation plants, requires a reliable Fault-RideThrough capability. When a grid fault occurs on the transmission system, the speed of the turbo-generator group increases uncontrolled, the induction generator injects large peak currents that can potentially damage the rotor converters and the plant tends to increase the reactive power consumption, so that it might intensify the voltage dip and contribute to the collapse of the power network. A simple solution would be the automatic disconnection of the plant from the grid in response to the power fault, but this policy could lead to a series of chain disconnections that would produce a massive power network failure. This is why new Grid Codes oblige the distributed power generation systems to remain connected to the power network, even in case of balanced voltage dips. In this paper, an Oscillating Water Column (OWC)-based wave power generation plant equipped with a Doubly Fed Induction Generator is modeled and controlled to overcome these balanced grid faults. The improvement relays on the implementation of a control scheme that suitably coordinates the air flow control, the crowbar, the rotor and the grid side converters to allow the plant to remain in service during the grid fault, and to contribute to its attenuation by supplying reactive power to the network. The simulated results show how it is obtained a great reduction in the rotor currents, improving the transient power stability and avoiding the rotor acceleration, complying with new Grid Codes requirements.

This paper focuses on the suboptimal regulation of controllers to supply information to each control station multivariable discrete-time bilinear systems consisting of from the remaining ones. This control technique is applied interconnected bilinear subsystems with respect to a linear to the optimization of classes of invariant discrete-time quadratic optimal regulation criterion which involves the use multivariable bilinear systems with interconnection of state weighting terms only. Three transformations are used . .in order to treat the scheme over an equivalent linear system. s ytems An su al solution of RicatiptypnsThis leads to the appearance of quadratic weighting terms found out as the suboptimal soluton by using manipulations related to both transformed input and state variables. In this on the input/state variables of the problem statement. The way, a Ricatti matrix-sequence allowing the synthesis of a importance of this strategy arises from problems where standard feedback control law is obtained. constrains on the input rather than input weights are introduced in the optimization criterion, what leads to a feedback-type control law. Therefore, the proposed technique allows to deal with multiple problems which are Dynamic bilinear systems have received important bilinear and involve interconnections. attention by researchers in the last decades, from [1] to the The paper is organized as follows. In the Section 2, the recent works of [2]. The importance of such systems is well problem statement for the class of the interconnected known in diverse areas as neural networks, population invariant discrete-time bilinear systems is given. Section 3 growth models, nuclear kinetics, etc. They form a transitive is devoted to the development of suboptimal strategies for class between the linear and the general non-linear systems. the regulation criterion, which involves quadratic terms of Well known works as [1] and [3] stated the controllability the state variables leading to a Ricatti-type suboptimal conditions for standard classes of discrete bilinear systems.solution. In Section 4, simulated examples are considered On the other hand, it is well known that the systems are and finally, conclusions end the paper in Section 5. In order often interconnected and, in many cases, several dynamic to maintain the paper extension constraints, mathematical subsystems can be distinguished for analysis purposes. This development and appendices have been minimized, but they sometimes takes place in computer communication, are available upon request to the authors. transportation networks, control, power stations, etc.This paper reports suboptimal optimization techniques, II. ON THE SYSTEM STRUCTURE AND CONTROLLABILITY which are applied to bilinear models. Such models can be PROPERTIES considered as extensions to the linear continuous interconnected systems stated by the classical work of A. Controllability ofa class ofbilinear systems Ramakrishna and Viswanadham [4]. First, the system is In [3], the following typical class ...