Due to the doubly salient structure, high magnetic flux density in the air gap and low pole number, cogging torque of 6/4 pole flux-switching permanent magnet (FSPM) machine is seriously high. In some cases, it may cause this machine hard to start up and serious torque ripple. So, reducing the cogging torque of 6/4 pole FSPM machine to a certain low extent is important to keep it work properly. To reduce cogging torque, a chamfering and flange rotor pole shape is proposed to reduce the cogging torque of 6/4 pole FSPM machine without skewing teeth. The key dimensions of the proposed rotor pole shape have been optimised by analytical methods and simulation based on finite-element analysis. The effectiveness of the proposed method has been verified by experimental results. The effect of the proposed rotor pole shape method on back-electromagnetic force and average electromagnetic torque has also been investigated.

This study proposes a method to separate average permanent magnet (PM) torque and average reluctance torque of five-phase interior permanent magnet (IPM) machine based on transient finite element method (FEM). The key of this method is to count total torque as four torque components by considering the saturation and cross-magnetisation between d–q axes, and every torque components are calculated from d–q axes parameters directly. The parameters in d–q axes reference frame are transformed from ABCDE reference frame via five-phase Park transformation. Comparing with the existing methods, the proposed method maintains the same accuracy while time saving because d–q axes parameters can be obtained directly by one-time FEM simulation. Meanwhile, the proposed method is adopted to separate the PM torque and reluctance torque from two five-phase IPM machines with fractional-slot concentrated winding (FSCW) and integral-slot distributed winding (ISDW). Finally, the FEM and experimental results show that the IPM machine with FSCW produces lower reluctance torque ratio than that of IPM machine with ISDW. Besides, the results demonstrate that the flux-weakening performance connects with characteristic current (Ψ_PMd /L_dd ) strongly.

Here, a simplified predictive torque control strategy based on discrete duty cycle technology is proposed for the voltage source inverter permanent magnet synchronous motor drive system. Combining the discrete duty cycle technology, the candidate vectors are synthesised by two adjacent active vectors and zero vectors, and meanwhile, the duty cycles of the two adjacent active vectors and zero vectors are generated directly. Afterwards, an extended control set is constructed to improve the control accuracy of torque and flux. An inverted triangular matrix is constructed to store the duty cycle information, which corresponds to the row and column number of the elements. Also, the inverted triangle matrix is divided into three subregions according to the value of duty ratios. A cost function containing only the stator voltage vector error term is constructed and based on the geometric position of the reference voltage vector, the target region in the inverted triangle matrix is determined and the optimal vector is selected. So, the optimal vector prediction process and the duty cycle calculation process are combined into one, reducing the complexity of obtaining the optimal vector. Finally, the feasibility and effectiveness of the proposed algorithm are verified by experiments.

In this study, a finite set model predictive control method is proposed for the quasi-Z source inverter-permanent magnet synchronous motor drive system. In the proposed method, the control variables of quasi-Z source network and motor are controlled uniformly, which can avoid the conflicts between the shoot-through duty cycle and the inverter modulation coefficient during the dynamic adjustment process in traditional two-stage control method. Due to the particularity of the motor connected to the quasi-Z source inverter, a power compensation control method is used to obtain the inductor current reference value. Whether the shoot-through vector is chosen as the optimal vector is determined by the inductor current, and the influence of undershoot phenomenon of capacitor voltage, which results from the non-minimum phase characteristics of quasi-Z source inverter, is avoided. Steady-state, dynamic, and input voltage dip experiments are performed on a quasi-Z source inverter-permanent magnet synchronous motor drive system. The experimental results verify the feasibility of the proposed predictive control method. Besides, compared with traditional two-stage control method, the proposed method has quicker response speed and stronger anti-disturbance ability.

Axial flux switched reluctance machines (AFSRMs) exhibit unique characteristics that specify their superiority over other topologies in specific applications. A number of researchers have studied the efficient design and constructed structures in different types of AFSRMs. Each of such studies seeks to produce a motor with improved characteristics. Here, a comprehensive study is performed in AFSRMs, including their design considerations, sizing equations and the structural changes. The sensitivity of parameters for efficient operation is investigated. Also, the comparisons among topologies are provided for each of the identified metrics. This study ends with a comparison summary, which shows the performance indices evaluation of different topologies to utilise in various applications.

This study presents an analytic designing approach for the sensorless direct thrust force control (DTFC) of permanent magnet linear synchronous motor (PMLSM). A modified stator flux estimator developed by use of an adaptive mechanism and correction factors is devoted to measuring the stator flux linkage and the mover's position. The parameters of the flux estimator are adjusted in advance through an off-line identification process to increase the accuracy of estimation. Based on the principle of backstepping control, the reference q-axis flux command, which is equivalent to the thrust force command, is first obtained from the Lyapunov functional analysis. Then, the reference d-axis flux command is calculated according to the characteristics of stator flux linkage. The voltage control strategy is constructed to stabilise the global system and ensure the convergence of DTFC. Compared to the conventional direct torque/thrust control, the proposed control scheme can apply the space vector modulation to achieve a fixed switching frequency. Consequently, the phenomenon of flux and force ripples inherited from DTFC is improved. The experiment results are provided to validate the proposed control approach. Moreover, a recent work that is based on the optimal control is adopted as a comparison study.

The usage of renewable energy sources (RESs) with energy storage like battery and so on in the stand-alone household and commercial purpose is becoming popular. These systems have to manage the requirement with the generated energy from the RES. Further, in a typical stand-alone household application, a significant amount of power is consumed by single-phase induction motor (SPIM) fans in the form of the ceiling, pedestal formats. So, it is necessary to save energy by operating them efficiently and economically in a stand-alone system. This study proposes a fractional flux-based V/f control strategy for speed control of a SPIM. The proposed retrofit scheme is simple and is easy to implement. It minimises the magnetisation loss irrespective of the fan speed and also saves nearly 10–20% of power consumption as compared to the conventional voltage control method. Further, in this study, a new performance parameter is defined which helps in determining an economic zone in variable speed operation SPIM. In this economic zone of operation, a particular battery can deliver power for an extended time. All the details with respect to analysis, modelling, simulation and experimental results to support the proposed strategy are presented in this study.

In this study, the finite element method (FEM) is utilised for precise analysis and detection of the bearing faults in induction machine drives. For this purpose, the machine inductances in the presence of slots, teeth, and various bearing failures are obtained by FEM. In addition, the spectrum of the stator currents are analysed by employing the electrical model of the induction machine drives. Some experimental and numerical results are illustrated that the proposed model can consider small bearing failures in high-noise environments and thus can be used for analysing and detecting bearing failures in induction machine drives.

To eliminate the influence of gyroscopic effect on system stability and to improve the control performances for the active magnetic bearing (AMB) high-speed flywheel rotor system, a novel control strategy based on the modal separation and inverse system method is proposed. The translational motions and rotational motions of the AMB flywheel rotor system are firstly decoupled by the modal separation, then the rotational motions are decoupled by the inverse system method, so that the AMB flywheel rotor system, which is a multivariable and strong coupled system, is decoupled into four subsystems. Finally, the subsystems are regulated by four two-degrees-of-freedom (2-DOF) internal model controllers, respectively. Furthermore, the stability, tracking and robustness of the novel control strategy are analysed theoretically, and its effectiveness on vibration control of the AMB high-speed flywheel rotor system is further investigated by simulations and experiments. The results show that the novel control strategy can achieve stable suspension and effectively suppress the vibration of the AMB high-speed flywheel rotor system from static state to 24,000 rpm, with the advantages of high stability, strong robustness, and good performances of tracking and disturbance rejection simultaneously.

Torque ripple of permanent magnet synchronous motor (PMSM) will result in the distortion of current waveform and the load flexibility of spiral torsion spring (STS) will affect the control performance of driving system. This study focuses on a new control problem of simultaneous suppression of PMSM's torque ripple and flexible load's vibration. First, the Lagrange equation is used to establish the dynamic model of STS to describe its vibration mode. The overall model of STS directly derived by PMSM under stator current vector orientation is built. Then, based on the magnetic co-energy model of electromagnetic torque of PMSM, the constraint relation of optimal stator harmonic current under the condition of torque ripple minimisation is derived, and the controller based on stator current oriented closed-loop I/f control to suppress load vibration and torque ripple simultaneously is presented through backstepping control. A wide speed range identification method based on the least-square algorithm with a forgetting factor is also designed. The simulation and experiment show that the speed identification algorithm can estimate the speed accurately in a wide range. The proposed control scenario improves control performance, smoothes current waveform and inhibits torque ripple and load vibration effectively.

Doubly fed induction generators and permanent magnet synchronous generators are widely used in wind power generation system in recent years. However, they still have technological and economic penalties, which limit their applications in wind power generation. This study presents a novel brushless doubly fed generator (BDFG) with the hybrid rotor, which has several outstanding advantages, so as to penetrate into large-scale offshore wind power generation. In this study, the magnetic field modulation of the hybrid rotor is studied in detail. Owing to the decisive role of ‘special rotor’ on the performance of BDFG, the effect of main rotor structure parameters on coupling capacity is analysed based on Taguchi method, and the effect of assisted cage bars on the coupling capacity is also researched. The simulation models are simulated and analysed to compare the different exciting winding conditions. A 25.8 kW, 8/4 pole prototype BDFG with the hybrid rotor is manufactured to examine the performance of the proposed BDFG. Finally, the simulation and experiment results verify that the optimised rotor has stronger coupling capacity and the few-pole (i.e. 4-pole) winding should be used as control winding.

This paper presents a wind-generation system design for rural applications. In Southern areas of Argentina, there are right conditions for wind energy exploitation. Depending on the characteristics of these areas, the wind-generation systems can operate either isolated or connected to the grid. This work particularly emphasises the design of a generator to optimise the system performance and achieve its minimum volume. The analytical design is evaluated using finite element analysis and experimentally validated using a 35 kW prototype. The tests reveal that the design procedure is suitable. The initially proposed efficiency aim was exceeded, reaching a maximum value of 94.2%. The generator operating conditions make it particularly suited for the application for which it was designed.

So far, various categorisations have been proposed for segregating predictive controllers (PCs). However, these categorisations have some shortcomings which lead to improper segregation of PCs. In this study, a new categorisation is proposed for more precise segregation of PCs applied to AC motor drives. In this categorisation, PCs are categorised based on existence or the absence of a cost function, number of voltage vectors applied to motor in each control cycle, and prediction horizon. Basic concepts, operating principles, and important characteristics of each category are explained in depth. Moreover, the advantages and disadvantages of each category are identified by conducting various experimental tests.

The ironless permanent magnet (PM) planar motor (IPMPM) has great potential to realise multi-degree of freedom (DoF) motion. The insufficient ability to model the end effect limits its performance. Here, an extended unified wrench model (EUWM) of IPMPM is proposed through a systematic extension of previously proposed unified wrench model (UWM). Based on the concept of periodic extension, the EUWM is established in three steps. First, the side region and the vertex region are defined and extended into periodic pattern and the residual magnetisation vectors of the PM array in each region are expressed in Fourier series form. Then, the problem with unequal periods in the x and y direction is presented. Second, the space is divided into three layers and the magnetic flux density in each layer is solved by scalar potential method. In the last step, the decoupling characteristic of the wrench vector act on the infinitesimal current carrying volume is found. Then, the analytical expression of the EUWM is derived. It is much more general and suitable for the IPMPM with arbitrary-shaped coil and the PM array with unequal periods in the x and y direction. Finally, the EUWM is verified by experiment.

Aiming at the problem of transformer vibration in DC biasing operation, the relationship between excitation characteristics and vibration is studied. The electromagnetic coupling state equation of transformer in DC biasing operation is established. Then, the dynamic inductance and time-domain current are calculated based on the energy disturbance principle. On this basis, the identification method of exciting current is studied to present the excitation saturation state. The excitation–vibration harmonic response model is constructed to analyse the relationship between the variation law of exciting current and vibration characteristics of the core under different DC levels. The correctness of this method is verified by the comparison between simulation and experimentation.