Predictive-Integral Current Controller for Active- and Reactive-Power Control of Wind Generators PedroRoncero-S´anchez 1 , Vicente Feliu 1 and Aurelio Garc´ ıa-Cerrada 2 1 Department of Electrical, Electronics, Control Engineering and Communications E.T.S. Ingenieros Industriales, Universidad de Castilla-La Mancha Avda. Camilo Jos´ e Cela S/N, 13071, Ciudad Real, (Spain) Phone:+34 926 29 53 00. e-mail: Pedro.Roncero@uclm.es, Vicente.Feliu@uclm.es 2 Department of Electronics and Control Engineering E.T.S. de Ingenier´ ıa ICAI, Universidad Pontificia Comillas C/ Alberto Aguilera 23, 28015, Madrid, (Spain) Phone:+34 91 542 28 00. e-mail: aurelio@iit.upcomillas.es Abstract This paper deals with the design of a predictive-integral current controller for wind generators connected to the grid. The goal is to achieve a decoupled control of d- and q-axes current components at the connection point, which results in a decoupled control of the active and the reac- tive power exchanged between the generator and the grid. Furthermore, the control system is designed in order to achieve a deadbeat closed-loop system. The robustness of the closed-loop dynamic response and the active and reactive-power coupling when system-modelling errors ex- ist are studied. Simulation and experimental results will be presented to validate the main contributions of this work. Key words Wind generator, voltage-source converter, deadbeat system, predictive control, robust control 1 Introduction Electricity generation making use of renewable energy sources has experienced a great growth in the last few years [1]. Wind generators are, probably, the clearest examples of this upgrowth. These systems must trans- fer the energy efficiently to the utility or to the load while supplying the necessary reactive power. For this purpose, current-controlled voltage-source electronic converters are normally used. Current-control schemes can be classified into two main groups (see [2] and [3] for more details): 1. Linear control schemes with conventional pulse- width modulators that split current-control and modulation parts. This group comprises the PI average-mode controllers and also predictive and deadbeat control schemes. 2. Non-linear control schemes, including hysteresis- based controllers, pulse density modulation and also neural-network-based and fuzzy-logic con- trollers. Predictive current controllers are recently being pro- posed very often in the literature: in this kind of con- trollers, the converter-output voltage is calculated in order to make the measured current to track the refer- ence based on a predictive model [4]. The implementa- tion of these current controllers is not ideal due to fac- tors such as modelling errors or dead-time effects [5], which may substantially affect the dynamic perfor- mance or even cause instability problems. These is- sues have motivated this work. Predictive current controllers applied to power- electronic converters can be found in [6–9]: in [6] a robust current controller is designed to obtain a dead- beat system for active filters and PWM rectifiers and a study of the robustness when there are modelling errors in the inverter-output inductance is included. Reference [7] deals with a predictive-current regulator applied to an induction-motor control. It also stud- ies the effects of errors in some parameters on the dynamic performance. In [8] a dead-beat current con- troller for converters with both, variable or fix output frequency is developed. It uses an error law for the measured current which improves the stability when there are modelling errors in the load inductance. Fi- nally, in [9], a predictive-current controller design for single-phase voltage-source converters connected to the grid is presented. A study of the robustness to the connection-inductance mismatch is included. The present work deals with the design of a predictive- integral current controller to implement active- and reactive-power control in a wind generator, obtaining a decoupled dead-beat closed-loop system. Unlike the previous predictive-current controllers, an integral ac-