Using Genetic Algorithm to Tune PI-Controllers for the Direct-Drive Synchronous Wind Generators Andrey C. Lopes, João P. A. Vieira, Marcus V. A. Nunes, Ubiratan H. Bezerra Faculty of Electrical Engineering Federal University of Pará Belém, Brazil andreylopes@ufpa.br, jpavieira@ufpa.br, mvan@ufpa.br, bira@ufpa.br André C. Nascimento Federal Institute of Education, Science and Technology of Pará Belém, Brazil borgonio@gmail.com Abstract—This paper presents a novel methodology for tuning proportional-integral (PI) controllers gains for the grid-side converter of direct-drive synchronous wind generator using a genetic algorithm (GA) approach. The control approach aims to improve the behavior of the direct-current (DC)-link voltage, by a more effective contribution of direct-drive wind generator controllers to the system controllability when an electrical fault occurs. The time-domain simulations are carried out using the single-machine infinite bus system model with one direct-drive synchronous generator. The performance of the wind generator with optimized controller parameters and with the parameters designed by the pole placement technique are compared to demonstrate that the control performance of the system with optimized controller parameters permits the improvement of the converter ride-through capability. Keywords-Direct-dive synchronous generator; wind turbine; genetic algorithm; PI-controllers; static power converter. I. INTRODUCTION The greater necessity of investments on renewable energy resources as an approach to contribute to the reduction of the green-house gases emission on the planet has been favoring the formation of new regulations and government incentives that aim to stimulate the exploration of these resources by independent producers, as well as by electrical public utilities. As effect, it has been verified during the last years a significant growth of wind parks all around the world, evolving, mainly, technologies with electronic interface of static converters, amongst these ones it is highlighted the direct-drive synchronous wind generator (DDSWG). The widespread integration of these wind generators on the electrical systems, taking into account its seasonal characteristics of operation, has promoted changes on the usual structure of the electrical grids so that the system operators have been defining procedures aiming, mainly, to guarantee the power system stability and protection. Currently, most of the grid requirements addresses low voltage ride- through (LVRT) and grid support capabilities of the wind turbines due to the short-circuits or other contingencies. In those specific cases, the machine must be connected to the grid, which means that its terminal voltage must remain with a voltage profile defined by the operator during the grid faults. Different voltage characteristic curves have been used in many European countries and worldwide in accordance to the rules of electrical system operation of each country [1]-[3]. Due to this fact, various control techniques that explore the electronic interface of the wind generators have been presented on the literature of this area. In [4], for example, the converter connected to the grid injects reactive power during the fault so that the voltage on the terminals of a doubly fed induction generator does not overcome the minimum limit imposed by the voltage curve established by the grid operator. Similar procedure is presented in [5], where the converter connected to the grid injects a certain current so that the reactive power increases, thus reducing the terminal voltage falls during the fault by this method. However, besides the control strategies that aim to attend the requisite of LVRT, there is the necessity to adopt a specific control to the direct current (DC)-link voltage, when this voltage suffers significant oscillations because of the imbalance of currents on the dc-link during the grid short- circuits or other faults. In the particular case of the DDSWG, this kind of control is even more essential because the converter connection is in the output of the generator that is on the stator of the machine and then suffers directly the impact caused by those faults on the grid. With an objective of reducing the DC-link voltage oscillations and consequently to avoid a possible out of service of the wind generator produced by the action of the protection of the electronic converters, the use of a chopper is discussed in [6], which is the control that allows to reduce the imbalance on the DC-link current. In this paper, the DC-link voltage control is accomplished by the converter connected to the grid, exploring a strategy of current control on coordinates d-q, which will be described in detail in topic II. On the basis of this methodology, the control loops are defined so that the controller’s PI gains can be obtained using the pole placement method [7]. An important contribution of this work is on the fact that these gains will be used as reference to the definition of the search space of the GA that aims to find the gains that optimize the DC-link voltage behavior during faults. Specifically, the system will be Modern Electric Power Systems 2010, Wroclaw, Poland MEPS'10 - paper P37