Ivonne et al. / J Zhejiang Univ Sci A 2008 9(2):156-164 156 Study on inverter fault-tolerant operation of PMSM DTC * Yznaga Blanco IVONNE 1,2 , Dan SUN †‡1 , Yi-kang HE 1 ( 1 School of Electrical Engineering, Zhejiang University, Hangzhou 310027, China) ( 2 Researches and Electrical Tests Center, Cujae University, Havana City 19390, Cuba) † E-mail: sundan@zju.edu.cn Received July 23, 2007; revision accepted Oct. 30, 2007 Abstract: This paper presents an investigation of inverter fault-tolerant operation for a permanent magnet synchronous motor (PMSM) direct torque control (DTC) system under various inverter faults. The performance of a faulty standard 6-switch inverter driven PMSM DTC system is analyzed. To avoid the loss or even disaster caused by the inverter faults, a topology-modified inverter with fault-tolerant capability is introduced, which is reconfigured as a 3-phase 4-switch inverter. The modeling of the 4-switch inverter is then analyzed and a novel DTC strategy with a unique nonlinear perpendicular flux observer and feedback compensation scheme is proposed for obtaining a continuous, disturbance-free drive system. The simulation and experimental results demonstrate that the proposed inverter fault-tolerant PMSM DTC system is able to operate stably and continuously with acceptable static and pretty good dynamic performance. Key words: Permanent magnet synchronous motor (PMSM), Direct torque control (DTC), Fault-tolerant operation, Four-switch inverter, Nonlinear perpendicular flux observer doi:10.1631/jzus.A071399 Document code: A CLC number: TM302; TM351 INTRODUCTION The permanent magnet synchronous motor (PMSM) direct torque control (DTC) system has attracted much attention at present because of its outstanding advantages, such as high torque/current ratio, high power density, high efficiency, high power factor, simplicity, robustness and excellent dynamic performance, compared with other types of motor drives (Takahashi and Ohmori, 1989; Zhong and Rahman, 1997). It is considered as one of the greatest potential to be adopted in automotive industries, electric vehicle, ship propulsion and other critical military situations (Diamantis and Prousalidis, 2004; Xing et al., 2005). The practical application of this technology, however, relies highly on its capability of maintaining continuous trouble-free operation and system reliability. A modern electrical drive system generally con- sists of a power electronic inverter, a microprocessor controller and a motor. Depending on the control strategy, various sensors are employed to acquire essential information of the system status. According to the instruction signal and system status, the control algorithm stored in the microprocessor controller generates appropriate gate drive signals, which con- trol the inverter to produce appropriate voltage space vectors to drive the motor with desired performance. In such a system, the inverter is a key component since any fault occurred without a pre-programmed fault-tolerant control strategy will cease the drive system, which may lead to disastrous economical loss. However, this can be avoided by incorporating a fault-tolerant control algorithm, which is able to maintain the system stable and generate a system fault signal to warn the system operator to clarify the problem. In the past few years, a great amount of works have been conducted on the faults diagnosis and their Journal of Zhejiang University SCIENCE A ISSN 1673-565X (Print); ISSN 1862-1775 (Online) www.zju.edu.cn/jzus; www.springerlink.com E-mail: jzus@zju.edu.cn ‡ Corresponding author * Project supported by the National Natural Science Foundation of China (No. 50507017) and the SRF for ROCS, SEM