This paper presents a novel position and speed estimation method for low-speed sensorless control of interior permanent-magnet synchronous machines (IPMSMs). The parameter design of the position and speed estimator is based on the sampled current rather than the motor electrical parameters. The proposed method not only simplifies the parameter design, it enables the estimator to work normally even in the condition that the electrical parameters are uncertain or varied. The adaptive filters are adopted to extract the desired high frequency current. The structure and corresponding transfer function are analyzed. To address the shortage of insufficient stop-band attenuation, the structure of the adaptive filter is modified to provide suitable bandwidth and stop-band attenuation simultaneously. The effectiveness of the proposed sensorless control strategy has been verified by simulations and experiments.

Two-level three phase rectifiers are widely used in industrial applications due to their superior performance. Their reliability has attracted lots of attention in recent decades. Transistor is one of the most fragile component because they suffer from voltage surge and thermic cycling. A fault diagnosis method based on current kernel density estimation for transistor open-circuit faults is proposed. The proposed method needs no extra sensors and it includes three steps: current kernel density estimation, Euclidean distance, fault detection and isolation. Experimental results show the proposed diagnosis method is highly efficient in single open-circuit fault and multiple open-circuit fault on the same leg.

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