Research On Single Current Sensor Based Vector Control For Indution Motor

Due to the advantages, such as the low cost, easy maintenance, sturdy and reliable, induction motors are widely used in industrial drive field. With the arising and development of vector control methods, the performance of the variable frequency speed adjustment system for induction motor is improved greatly by reducing the difficulty of control method for the system. In order to implement the vector control method, two closed loops are introduced to correct the system using the current and speed information that is obtained by current sensors and speed encoder. Since the sensors are prone to fail in harsh environment, which leads to reduce the reliability of the system. Regardless of the harsh conditions in which only one current sensor is healthy even when speed sensor is broken as well, the system can operate properly, so that the safety of the induction motor speed regulation system reliability greatly enhanced.In order to improve the reliability of the system, this paper proposes a vector control method with only one healthy current sensor. This method can be used as the tolerant control after the current and speed sensors broken.After improvement, the proposed control method can also have good performance even without speed encoder so that the proposed control system can achieve the tolerant control for induction motor under the harsh condition that the information of current and speed is missing simultaneously.Firstly, this paper proposes a vector control method with only one healthy current sensor. According to the actual situation, the structure of the full order state observer is improved and a more comprehensive feedback matrix designed. Therefore, the is proposed. The estimated stator currents obtained by the improved full order state observer replace the missing measurement currents to accomplish the current closed loop. What’s more, this paper also analyzes the stability of the current observer, the feasibility of the system is verified by simulation and experimental verification.Secondly, the speed sensorless vector control method with the only one healthy current sensor is proposed by combining the basic idea of the single current sensor vector control method. According to the theoretical analysis, the speed sensorless vector control method is also based on the full order state observer, and the current observer and speed observer are combined to achieve the tolerant control for the system under the situation that the information of current and speed is missing simultaneously. In order to improve the accuracy of speed estimation, a simple and effective feedback matrix is redesigned by analyzing the stability of the speed observer. In this paper, simulation and experimental analysis are used for the proposed method and the experimental results verify the feasibility of this method.Finally, the experimental platform that is based on ARM with 1.1kw induction motor is set up, using the coaxial motor for loading scheme. Meanwhile, the hardware architecture and software design process are both introduced briefly. The programing and debugging for proposed method are finished by Keil software. The feasibility of the proposed method is verified by the experiments under different conditions. The experimental results show that, in the case of the speed sensor is working, the proposed single current sensor vector control system has good control performance, the system can operate stably at low or even zero speed, in the case of the speed sensor is absent, the stability of the system can also be guaranteed, and the system can achieve stable switch from the motoring condition to generating condition.