This paper presents a 3-D magnetic equivalent circuit (MEC) network that integrates the hysteresis model for the analysis of the axial field flux-switching (AFFS) memory (AFFSM) machine. Similar to finite element method, meshing is used to subdivide the model into smaller domains called elements, over which a set of element equations and a reluctance network equation are built. Newton-Raphson method is adopted to handle the nonlinear problems. The fixed-point technique is introduced to cope with the problem involving hysteresis. The proposed method is capable of predicting the operation of the low coercive force permanent magnet during flux regulation and the electromagnetic field distribution of the machine. Finally, the proposed 3-D MEC method is implemented for analysis of the AFFSM machine. MEC results are compared with 3-D finite element analysis and experimental results. The results show that the proposed method offers reasonable accuracy with moderate computational effort.

Grid-forming inverters, which are represented by droop control and virtual synchronous generator control, have been widely studied and applied because of their excellent grid-supporting ability and smooth off-grid switching. When a grid-forming inverter is connected to a microgrid or utility grid, the control loops of active power and reactive power will be coupled because of the voltage phase difference, which will affect the power control performance. This paper first derives the small-signal linearized model of the system, based on which a frequency feedforward control and an amplitude feedforward control are proposed to decouple the active power and reactive power control loops, respectively. The proposed decoupling strategy directly modifies the reference values through feedforward with an easily implementable principle that is applicable to various control coordinate systems, control coordinate systems, and control structures. By comparing system models with and without the proposed decoupling strategy, its effectiveness can be theoretically proven. Time-domain simulations and hardware experiments are presented to further validate its effectiveness.

This paper presents a novel axial field flux switching memory (AFFSM) machine which integrates series permanent magnet (SPM) and an additional DC field winding for improving the flux regulation capability. The configuration and the operation principle of the SPM-AFFSM machine are presented. The design considerations for the SPM and the DC field winding are discussed. The voltage regulation capability and torque-speed characteristics of the SPM-AFFSM machine are investigated by 3-D FEA. Finally, a prototype is developed for experimental verification. The measured results verify structural validity and the finite-element predictions.

Subjected to a fixed dc-link voltage, this paper presents a novel flux-weakening control combined with magnetization state for the hybrid permanent magnet axial field flux-switching memory machine. Due to the flux regulation characteristic, the wide speed range can be further extended and the torque output can also be enhanced. The machine configuration is introduced and its distinct features are analyzed. The mathematical model of the machine is built based on the rotor reference frame. Then, the proposed control strategy is addressed from multiple aspects including the control mechanism, the current distribution strategy, the voltage and current trajectory. Both the simulation and experimentation are carried out to evaluate the machine performance. The results verify the effectiveness of the proposed control strategy.

Due to the short axis, high torque density and wide permanent magnet (PM) flux linkage regulation range, the series hybrid PM axial field flux-switching memory machine (SHPM-AFFSMM) has been paid much attention. In order to extend its speed range, the way to generate an effective current pulse to regulate the magnetization state of the low coercive force PM is the key issue. The magnetization state regulation (MSR) method characterized with bidirectional and quantitative current pulse, is presented to investigate the MSR characteristics of the SHPM-AFFSMM. Based on the proposed MSR method, the MSR characteristics of the researched machine, including no-load induced electromotive force (EMF), inductance characteristics, cogging torque and permanent magnet flux density, are investigated by simulation and experiment.

This article investigates the generation mechanism of electromagnetic torque, particularly the reluctance torque in fractional slot concentrated winding (FSCW) V-type interior permanent magnet machine (V-IPM) machine. Based on the air-gap field modulation theory, the modulation process of the PM field and armature reaction field is elucidated by establishing a magnetomotive force (MMF) and permeance model considering the magnetic saturation of rotor magnetic bridge. Through analyzing the conditions for effective coupling of air-gap field harmonics, studying the time-domain modulation effect resulting from the magnetic saturation of rotor magnetic bridge, and establishing the mapping relationship between inductance harmonic and single-phase winding field harmonic, the generation mechanism of electromagnetic torque, including both the PM torque and reluctance torque in FSCW V-IPM machine, is first revealed. Then, a harmonic restoration method based on frozen permeability is adopted to quantitatively analyze the contribution of the armature reaction MMF harmonics to the PM torque and reluctance torque. Moreover, the reluctance torque ratio, defined as the ratio of reluctance torque to electromagnetic torque, is additionally presented from the aspect of armature reaction MMF harmonics. Finally, the analysis is verified numerically by an exist well-developed FSCW V-IPM machine.