Vfcon

Advanced Control of Variable Flux Permanent Magnet Synchronous Machines (VFCON)

Funding institution: Ministerio de Ciencia, Innovación y Universiodades.

Participating institutions: University of Oviedo.

Dates: 01/09/2023 – 01/09/2026 

Project leader: Daniel Fernández Alonso, David Díaz Reigosa

Research team: Fernando Briz, Diego Laborda, Marcos Orviz, Carlos Suárez, María Martínez 

INDEX

ABSTRACT

Permanent magnet synchronous machines (PMSM) have been the focus of significant research effort in recent years due to their superior performance, controllability, efficiency or power density, compared to other types of machines. The continuous demand of more efficient electric systems, safer and more reliable made PMSMs the primary option for traction and generation applications in multiple fields:household applications, electric traction and generation systems, military and aerospace applications. Nevertheless, efficiency of PMSMs is diminished in variable speed systems operating at high speeds as negative d-axis current must be applied in order to counteract permanent magnet (PM) flux linkage, matching the back electromotive force (Back-EMF) with the available voltage in the DC link. This mode of operation is known as flux-weakening and is characterized by an inherent copper and core loss increase; due to continuous application of negative d-axis current and the extra harmonics produced in the airgap field. Extra losses reduce the efficiency and increases the temperature of all machine parts (i.e. electric insulation, magnetization of PM), accelerating its degradation. To avoid the injection of flux weakening current and its subsequent adverse effects, variable flux permanent magnet machines (VFPMSMS, also known as memory motors) have been proposed. These types of machines dynamically change the PM magnetization state (MS) during high speed operation, to reduce the need of flux weakening current what drastically reduce the induced losses. Design optimization of a VF-PMSM becomes a complex task since power density, and the volume of permanent magnet used must be maintain compared to conventional PMSMs. At the same time, the machine must allow magnetization/demagnetization easiness to avoid overrated converters, and high demagnetization withstand capability to torque currents. VF-PMSM design relies also on the PM magnetics, electric and thermal stability. A precise characterization of the PMs is therefore key to achieve a precise, stable and safe control of VF-PMSM which is achieved when the magnetization state of the permanent magnets is accurately estimated. Therefore, the development of new PM magnetization state estimation state is a key factor for the controllability of VF-PMSMs. 

OBJECTIVES

There are two main goals in this project:

1. The first goal of the project proposal is to evaluate design methodologies for VF-PMSM to meet electric vehicle traction requirements or railway traction requirements. This includes the analysis of the design space of VF-PMSMs based on machine parameter plane, power conversion properties, and total loss distributions based on an assumed demagnetization characteristic.

This first objective will introduce advances in the design of the machine and can be further divided into five general goals:

• Development of analytical models to predict the feasible regions of VF-PMSMs parameter plane, feasible electromechanical power conversion of VF-PMSMs and suggested design space for VF-PMSMs.

• Development of analytical models to identify the potential limitations of VF-PMSMs designs in terms of torque, speed and variable flux characteristics.

• Development of FEA and analytical models of alternative non-standard PMs composites (Sm, SmCo, NdFeB) to exploit the VF properties of VF-PMSMs

• Development of analytical models to estimate the properties and key performance metrics of VF-PMSMs across a range of torque-power.

• Development of analytical models to predict the scalability of VF-PMSMs including loss reduction capability during the driving cycle and cost-benefit system analysis.

2. The second goal is to investigate MS trajectories that can be adopted depending on the machine working condition and MS requirements; this will include the analysis of the injected current for MS manipulation on the final PMs’ MS, the required energy consumption considering side effects, and the operating capabilities of MS manipulation possible trajectories. Also, this second goal includes monitoring techniques to determine the PMs’ MS.

This second objective will introduce advances both in the design and control of these types of machines. This objective can be divided into three general goals:

• Development of MS trajectories alternatives to reach both uniform and non-uniform MS patterns (MS shaping), including online magnetization and demagnetization strategies.

• Development of simulation models needed for the analysis of the MS trajectories alternatives.

• Development of MS measurement/estimation methods for VF-PMSMs.

The development of models to predict the scalability of VF-PMSMs, their capabilities during the driving cycle, and the cost-benefit analysis of the whole traction system will contribute to closing the gap between research stages to industry application. On the other hand, the development of magnetizing trajectories for VF-PMSMs considering complex modulation patterns, voltage, speed capability, torque ripple, and time duration to reach both uniform and non-uniform MS patterns, i.e. development of MS control algorithms, will also contribute to make VF-PMSMs a feasible alternative for industry applications. Both objectives will bring a performance and efficiency increase in the whole torque-speed range of the machine.

EQUIPMENT & RESULTS

REALTED PUBLICATIONS

• H. Lee, J. Jeong, M. O. Zapico, S. Bin Lee, D. D. Reigosa and F. B. del Blanco, "Airgap Flux-based Estimation of Permanent Magnet Temperature for Thermal Protection of PMSMs," IEEE Trans. on Ind. Appl., 60(1), 367:376. DOI: 10.1109/TIA.2023.3320644

• C-H. Lee, A. J. Salcedo, N. Byum, S.B. Lee, M. O. Zapico, D. D. Reigosa, F. B. del Blanco and M. Osama, "Inverter-embedded DFIG Rotor Winding Insulation Testing for Wind Energy Applications," IEEE Trans. on Ind. Appl., 60(6), 9195-9205. DOI: 0.1109/TIA.2024.3443788

• M. Orviz, J.G-A. Tiemblo, D. F. Laborda, D. Reigosa and J. M. Guerrero, "Optimization of Magnetization State Manipulation in Variable-Flux PMSMs," IEEE Trans. on Ind. Appl., accepted, publication pending, DOI: 10.1109/TIA.2025.3534161

• M. Saeed et al., «Model-Based Risk Assessment of Power Converters: Case Study of On-Board Battery System for Railway», IEEE Open Journal of Industry Applications, vol. 6, pp. 221-236, 2025, doi: 10.1109/OJIA.2025.3564730.

• P. B. Nazif et al., «Parameter Identification for dc-dc Buck Converter Digital Twin Considering Sensors Errors», IEEE Journal of Emerging and Selected Topics in Power Electronics, pp. 1-1, 2025, doi: 10.1109/JESTPE.2025.3557520.

• S. Ahmad et al., «Hybrid Signaling-Droop DC-Link Voltage Control for Trains With Multiple Onboard Power Sources», IEEE Access, vol. 13, pp. 75430-75443, 2025, doi: 10.1109/ACCESS.2025.3564406.

• D. García-Pérez, M. Saeed, I. Díaz, J. M. Enguita, J. M. Guerrero, y F. Briz, «Machine Learning for Inverter-Fed Motors Monitoring and Fault Detection: An Overview», IEEE Access, vol. 12, pp. 27167-27179, 2024, doi: 10.1109/ACCESS.2024.3366810.

• S. Ahmad et al., «Priority-based dc-link voltage control for railway traction chains with onboard energy storage», IEEE Open Journal of Industry Applications, pp. 1-13, 2024, doi: 10.1109/OJIA.2024.3501072.