1 Open Circuit Fault Diagnosis of PMSG Wind Turbine Power Converters Kai Huang 1 , Yingning Qiu 1* , Wei Qin 1 , Yanhui Feng 1 ,Wenxian Yang 2 1 School of Energy and Power Engineering, Nanjing University of Science and Technology, Nanjing, China, * corresponding author E-mail:yingning.qiu@njust.edu.cn; 2 School of Engineering, University of Newcastle, United Kingdom Keywords: wind turbine, power converter, fault detection and diagnosis, topology. Abstract With the rapid development of wind power generation, permanent magnet synchronous wind power generation system has become the mainstream model of wind power system. The reliability of a converter system in a wind power system has important impacts on the power conversion process in the entire wind power system. Open-circuit failure of converter’s IGBT as the key failure mode of converter system should be realized real-time detection and localization. This paper studies the open-circuit fault of converter in permanent-magnet direct-drive wind power generation system. The wind power generation system is simulated by Matlab / Simulink simulation. A real-time fault detection algorithm is proposed based on generator operating characteristics and modified Park transformation. The method is suitable for the fault diagnosis of wind power generation with variable wind speed and multiple-noise interference without any additional hardware facilities. 1 Introduction Permanent magnet synchronous wind power generation system is an important configuration of wind power generation system. Direct-drive transmission systems provide improved flexibility by using permanent magnet synchronous generators instead of gearbox [1]. In order to ensure maximum wind energy conversion efficiency over the entire operating range, synchronous generator wind power systems are usually controlled by full-power converters. With the help of full-power converters, the direct-drive system can satisfty different grid-connected requirement without additional devices [2]. The full-power converters used in PMSG wind power systems are two-level voltage source converters. Onshore or offshore wind power systems require high reliability while open-circuit or short-circuit faults often occur in the IGBT of the converter due to various reasons, which results in failure of the converter. Many scholars have studied the IGBT open-circuit fault diagnosis algorithm of the converter. A novel fast-diagnostic method for open-switch faults in inverters without sensors is proposed, based on switching function model.The switch voltage and signal are used to identify the fault, which lead to extra hardware increases [3]. A rectifier fault diagnosis algorithm is proposed by using a current normalization algorithm. The relationship between wind speed and current is fitted and normalized, and the normalized currents are identified and rearranged by Park transform to achieve the purpose of fault diagnosis and positioning [4]. Another approach of detecting the occurrence of the open circuit fault of the power switch by using the derivative of the phase angle of the current Park transformed, and implementing the fault- tolerant control through a three-phase four-switch circuit [5]. A new multiple open-switch fault diagnosis method and faulty switch localization algorithm in three-phase AC/DC PWM converter. To verify that the proposed methods are effective to detect faults and to identify the faulty switches position, the simulation results under twenty-one cases of open-switch faults are presented on different operating conditions [6]. A single fault diagnostic algorithm for multiple IGBTs open-circuit faults and current sensor faults in direct-driven wind turbines. Several simulations are presented, showing the algorithm reliability against false alarms under both multiple IGBTs and current sensor faults in the back-to- back converter[7]. A real-time and computation-efficient method for diagnosing 2L-BTB converter in PMSG.The fault detection and localization are implemented with the average absolute value of the sum of the normalized three phase currents and the average absolute values of the normalized currents[8]. A general framework is proposed for open-circuit fault of full scale converter in PMSG system, where fault detection and fault identification are implemented by making use of the derivative of the absolute current Parks vector, current polarity and errors of the normalized current average absolute values[9]. Due to the complexity of the operating environment of the wind power system and the irregularity of the wind speed, the existing fault diagnosis methods are challenged. The methods proposed so far are mostly aimed at constant wind speed operating conditions. Good robustness of converter fault detection method is required for wind power system application against disturbances such as rapid wind speed change, fault detection speed, and multiple-tube fault diagnosis and positioning. 2 Operation and fault characteristics 2.1 Operation characteristics of PMSG Wind Turbine