Second-Order Sliding Mode-Based Direct Torque Control of Variable-Flux Memory Machine

Wei Wang,Wei Liu,Heyun Lin,Hui Yang,Shukang Lyu

doi:10.1109/access.2020.2974238

Wei Wang, Wei Liu + Show 3 more

Open Access

https://doi.org/10.1109/access.2020.2974238

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Abstract

The variable-flux memory machine (VFMM) exhibits high efficiency over a wide speed range because its airgap magnetic flux can easily be regulated by varying the magnetization state (MS) of the employed low coercivity force permanent magnets. This paper proposes a second-order sliding mode (SM)-based direct torque control (DTC) strategy for the VFMM, which features a relatively low computational complexity and less dependence on machine parameters. The operating principle and mathematical model of the VFMM are first described and established. On this basis, a novel control scheme combining the DTC strategy with MS manipulation is proposed, in which the machine is controlled by utilizing the DTC strategy incorporating the $i_{\mathrm {d}} = 0$ condition, while the MS manipulation is implemented by energizing reference stator flux linkage pulses. A super-twisting second-order SM controller is subsequently developed to achieve strong robustness. The developed control structure avoids a complicated decoupling algorithm and is simpler than that of the conventional field-oriented control (FOC) method. Finally, the effectiveness of the proposed control scheme is validated by simulation and experimental results.

Highlights

The permanent magnet (PM) synchronous machine (PMSM) has been widely used for various applications due to its inherent merits such as an unsurpassed efficiency and power density [1], [2]
This paper proposes a second-order sliding mode (SM)based direct torque control (DTC) strategy for variable-flux memory machine (VFMM) to achieve a wide speed range, high efficiency, and strong robustness performance
The scheme combines the advantages of conventional DTC with the variable-flux characteristics of VFMMs

Summary

INTRODUCTION

The permanent magnet (PM) synchronous machine (PMSM) has been widely used for various applications due to its inherent merits such as an unsurpassed efficiency and power density [1], [2]. A variable-flux memory machine (VFMM) employing low coercive force (LCF) PMs has gradually become a competent candidate to realize convenient flux regulation by applying a temporary demagnetizing or magnetizing current pulse [7], [8]. A speedregion-based FW control combined with an MS manipulation method for a hybrid PM axial field flux-switching memory machine was presented, and an adaptive observer was utilized to mitigate the flux linkage estimation error in [24]. This paper proposes a second-order sliding mode (SM)based DTC strategy for VFMM to achieve a wide speed range, high efficiency, and strong robustness performance. The CPSR of the machine can be extended if an appropriate MS is selected

MATHEMATICAL MODEL

SLIDING MODE CONTROL

RESULTS AND DISCUSSIONS

CONCLUSION