Improved Nonlinear Flux Observer-Based Second-Order SOIFO for PMSM Sensorless Control

Abstract

The conventional rotor flux estimation method has issues of dc offset and harmonics, which are caused by initial rotor flux, detection errors, etc. To eliminate these defects, one improved nonlinear flux observer is proposed for sensorless control of permanent magnet synchronous machine (PMSM). Firstly, the rotor position estimation method based on PMSM rotor flux observation is studied. Meanwhile, the limitations of the traditional rotor flux estimators, i.e., the saturation of pure integrator, phase shift and amplitude attenuation of low-pass filter are analyzed. Then, two novel flux observers, second-order generalized integral flux observer (SOIFO) and second-order SOIFO are designed for the rotor flux estimation of PMSM. Based on second-order generalized integrator (SOGI) structure, the SOIFO can limit the dc component to a certain value. Furthermore, the second-order SOIFO is developed from the SOGI, which is characterized with effective dc and harmonics attenuation capability. With the second-order SOIFO, even without magnitude and phase compensation, the dc offset and harmonics of estimated rotor flux could be well eliminated. Therefore, the speed and rotor position can be estimated accurately. All the performances of the four methods are analyzed by transfer functions and Bode diagrams. Lastly, the new sensorless control strategy is validated by comprehensive experimental results.

A Super-Twisting Sliding-Mode Stator Flux Observer for Sensorless Direct Torque and Flux Control of IPMSM

“…However, in the process of reaching a steady state, the estimated flux dc offset is already accumulated. The estimated flux dc offset can be given as: (20) where, ψ s0 is the flux dc offset, and t 1 is the time to steady state. In general, ψ s0 can be omitted because A 0 and t 1 are small, but if new dc disturbances interfere with the system, it will cause the accumulation of flux estimation dc offset and eventually have a non-negligible impact on the stator flux observation.…”

“…Therefore, the active flux-based sensorless scheme is suitable for the DTFC-based IPMSM drive systemBased on the IPMSM model, the stator flux is the integral of the back-emf and it is critical for flux observers to consider the influence of disturbances, especially dc offset [19]. When the pure integrator is adopted as a flux observer, the flux dc offset will increase with time, eventually resulting in the saturation of the observer [20]. In [21], a disturbance observer is designed to eliminate the dc component, but it is difficult to implement due to its complex structure.…”

Luenberger‐typecubic observers for state estimation of linear systems

“…As a result, in many applications requiring the whole state variable vector, it is inevitable to use an observer to construct the state variable from the measured output. 1 Observers may be used for observer-based feedback control, [4][5][6][7][8] fault detection [9][10][11][12][13][14] and parameter estimation. 1 Unknown or partially known input, 3,10 robust, 7,15 optimal 2,15 and functional 16 observers have been investigated in the literature for linear 16 as well as descriptor, 3,16 delayed, 9 time varying, 2 linear parameter varying 13,14 and nonlinear systems.…”

Low-Cost Position Sensorless Speed Control of PMSM Drive Using Four-Switch Inverter

“…The detailed classifications of the sensorless control methods are depicted in Figure 1 [1][2][3][4][5][6][7]. Recently, improvements in model-based and signal injection methods for PMSM drives have been investigated in the literature [8][9][10][11][12][13][14][15]. To suppress the unwanted audible noises in the signal injection methods, pseudo-random high-frequency signal injection (HFSI) method is proposed as an alternative to the classical HFSI technique [8,9].…”

“…Adaptive synchronous-requency tracking-mode observer (SFTO) which is a combination of SMO and model reference adaptive system (MRAS) is investigated for a surface mounted PMSM drive in [13]. In [14], a highly accurate rotor position and speed estimation are achieved by eliminating the influence of harmonic components caused by torque fluctuations at high and low speed regions. Two novel nonlinear rotor flux observers, second-order generalized integral flux observer (SOIFO) and second-order SOIFO are proposed instead of a classical pure integrator and Low-Pass Filter (LPF) to eliminate the offset and harmonics in the estimated rotor flux.…”