Enhanced sensorless control of interior permanent magnet synchronous motors based on nonlinear extended state observers

Zhang, Tianru (2021) Enhanced sensorless control of interior permanent magnet synchronous motors based on nonlinear extended state observers. PhD thesis, University of Nottingham.

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In practice, sensorless drive systems of interior permanent magnet synchronous motors (IPMSMs) are usually working in highly utilized or continuous heavy duty conditions where various disturbance exist, such as fast changing uncertain loads, inverter losses, measurement noise, model inaccuracy, etc. These issues could reduce the performance and stability, which become the main vulnerability of sensorless drives. Direct calculation method or phase locked loop (PLL) is conventionally adopted to estimate the speed and position at the last stage of sensorless estimation which concerns the overall performance. Without compensation or gain-scheduling, these conventional methods are unable to accurately estimate the rotor position and speed for the sensorless drive systems. The linear extended state observer (LESO) can be introduced to replace the PLL for performance improvement. However, the fast changing uncertainties cannot be observed thoroughly and very high gains are more likely needed which may excite noise in the control channel.

In the thesis, a nonlinear third-order extended state observer (NESO) is proposed for the further enhancement of the rotor position and speed estimation for sensorless IPMSM drives. The disturbance observation bandwidth of the proposed observer is expanded by deploying a gain optimization method. The measurement noise excited in the control loop is suppressed effectively. Comparative experimental results between the LESO and NESO verify the effectiveness and improvement of the proposed NESO against rapid speed variations, sudden load variations and down speed challenge. The sensorless operation of IPMSM with different saliency is tested to validate the capability of the NESO. However, the complexity of the parameter configuration and analysis may limit the application of such method. Therefore, a third order super-twisting extended state observer (STESO) is then proposed to reduce the difficulty of implementation without sacrificing the advantages of nonlinear properties. Utilizing the high-order extended state and super-twisting algorithm, fast convergence and disturbance estimation can be achieved in STESO. The dynamic performance and robustness of the STESO against sudden speed and torque variations is comparable to that of the NESO. Experimental results focus on the disturbance estimation ability and robustness of STESO. In comparison with LESO, the enhancement of STESO can be markedly noticed in the experimental test.

Moreover, the extremely low speed operation is achieved with the aid of high frequency signal injection in the existing unified sensorless structure. A high frequency current controller and a high frequency extended EMF observer are proposed to estimate the excited extended EMF. The proposed STESO is used to retrieve the position and speed. The effectiveness of such scheme is verified by the experimental results.

Item Type: Thesis (University of Nottingham only) (PhD)
Supervisors: Xu, Zhuang
Li, Jing
Castellazzi, Alberto
Gerada, Chris
Keywords: sensorless drive systems; IPMSM
Subjects: T Technology > TK Electrical engineering. Electronics Nuclear engineering
Faculties/Schools: UNNC Ningbo, China Campus > Faculty of Science and Engineering > Department of Electrical and Electronic Engineering
Item ID: 63791
Depositing User: ZHANG, Tianru
Date Deposited: 10 Dec 2020 02:38
Last Modified: 20 Jul 2021 00:42
URI: http://eprints.nottingham.ac.uk/id/eprint/63791

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