International Conference on Renewable Energies and Power Quality (ICREPQ’15) La Coruña (Spain), 25 th to 27 th March, 2015 Renewable Energy and Power Quality Journal (RE&PQJ) ISSN 2172-038 X, No.13, April 2015 A fault detection method for pitch actuators faults in wind turbines C. Tutiv´ en, Y. Vidal, L. Acho and J. Rodellar Universitat Polit` ecnica de Catalunya, Applied Mathematics III Department, CoDAlab, Comte d’Urgell, 187, 08036, Barcelona, Spain. Phone number:+0034934137309, e-mail: christian.tutiven@upc.edu, yolanda.vidal@upc.edu leonardo.acho@upc.edu, jose.rodellar@upc.edu Abstract. The paper presents a model-based fault detection method for pitch actuators faults using the normalized gradient method to estimate the parameters of the pitch actuator. One major difficulty is that the input signal to the parametric estimation method must be a persistent excitation. To circumvent this, a chattering term is added to the pitch control law and the usual low-pass filters are not used for the parametrization in the normalized gradient method (thus acceleration information is used). In order to verify the proposed method, simulations are conducted within a Hardware in the Loop (HiL) platform using the wind turbine simulation software FAST (Fatigue, Aerodynamics, Structures, and Turbulence). Key words Parameter estimation, fault detection, wind turbine, FAST, Hardware in the Loop. 1. Introduction Wind energy is rapidly emerging as a cost-effective sustainable technology. The demand of higher power production installation and the continuous increase of the size of wind turbines (WT) have led to new challenges in the WT systems. Fault detection and isolation (FDI) techniques are fundamental to detect and locate degradations and failures in the operation of WT components as early as possible. In consequence to this, the FDI research has witnessed a steady increase in interest in this application area. Publications can be named, among others, such as an H-infinity based technique to detect and estimate the magnitude of blade bending moment and pitch actuators faults [1], an unknown input observer designed for the detection of sensor faults around the wind turbine drive train [2], a model-based system identification technique for pitch actuator faults [3], FDI and fault tolerant control (FTC) for a wind turbine generator and converter system [4] and doubly fed induction generator sensor fault diagnosis [5]. The FDI and FTC systems use fault detection (FD) techniques to achieve their goals. A FD technique detects faults by means of a residual signal produced by available measurements. It must be a signal that is close to zero in the absence of a fault, and significantly affected in the presence of faults [6], [7], [8]. The main components of a fault detection system are the following [6], [7]: a residual generator signal, residual evaluation method, and a prescribed threshold to decide whether a fault occurs or not [6], [7], [9]. This paper proposes a model-based fault detection method that detects a fault whenever a change occurs in the dynamics of the pitch actuator [10]. The normalized gradient method [11] is used to estimate the parameters of the pitch actuator and a residual signal is obtained. A 5MW wind turbine based on FAST will be used in the simulations. Moreover, tests will be conducted in a HiL platform using the Arduino microcontroller [17]. The paper is organized as follows. In Section 2, the Na- tional Renewable Energy Laboratory (NREL) wind turbine simulator FAST [12] code, the pitch actuator model and the generator and converter model are given. Section 3 states the control strategies. The FD method is conceived in Section 4. Finally, in Section 5 the Hardware in the Loop platform, and the simulations are presented. 2. Wind Turbine Model A. FAST The FAST code [12] is an aerolastic simulator capable of predicting the extreme and fatigue loads of two and three bladed Horizontal Axis Wind Turbines (HAWTs). This simulator was developed by the National Renewable Energy Laboratory (NREL) and has been accepted by the scientific community and is used by many researchers in the development of new control systems for wind turbines. We select this simulator for validation due to the fact that in 2005 the Germanischer Lloyd WindEnergie evaluated FAST and found it suitable for the calculation of onshore wind turbine loads for design and certification [13]. Numerical validation with FAST were performed with the NREL 5MW on-shore wind turbine. The wind turbine characteristics are summarized in Table I, see [16].