This paper presents a hybrid AC/DC dual-stator winding induction generator (DWIG) and a multi-objective optimization design method for more-electric aircraft application. The DWIG has two sets of stator windings. One is DC winding which handles with part of reactive power for excitation and output 25kW/270 V DC power through power converter. The other is AC winding which directly outputs 25kVA/115 V AC power. To achieve the hybrid AC/DC generation with good performances, a separate-slot winding pattern is presented for two sets of stator windings and the winding factor is designed to obtain the optimal induced voltage ratio as well as electromotive force. A metamodel-of-optimal-prognosis (MOP)-based optimization method is proposed to handle with the conflicts between the optimization targets and constraints. By the parameter sensitivity analysis based on the response surface method, the important optimization variables and a MOP model with high parameter sensitivity and high quality is built. A multi-objective evolutionary algorithm is used with the MOP model to obtain the Pareto set. A design point is selected from the Pareto set as the final optimal design. The performances of the optimal DWIG are compared with the initial design. A prototype DWIG is manufactured and the test results validate its performance.

To address the critical challenges of efficiency enhancement, cost reduction, and system reliability in low-voltage high-current (LVHC) power generation system for small low-altitude transport autonomous aerial vehicles (AAVs/UAVs), this paper proposes a novel integrated starter/generator (ISG) power conversion architecture with a single DC bus current sensor. In this architecture, multiphase interleaved buck converters are employed, and a double closed-loop controller is typically adopted to regulate the output voltage. Additionally, a current-sharing loop is implemented to ensure a balanced distribution of inductor currents. However, coupling between loops can cause the current sharing process to affect the output voltage regulation. To address this problem, a decoupled current-sharing control method is proposed, ensuring mutual noninterference between output voltage regulation and inductor current-sharing. In this paper, the innovative aspects of the proposed power conversion architecture are first highlighted, followed by the development of a small-signal model. The principles of the decoupled current-sharing strategy and the phase current reconstruction method are elaborated comprehensively. Building on this, the proposed strategy employs a parallel loop structure, which effectively mitigates loop coupling. Quantitative analysis reveals that the coupling degree between the loops of the proposed strategy is negligible across the full operating range. Furthermore, controller loop parameters are meticulously designed to enhance system stability and dynamic performance. Finally, a 3-kW integrated starter/generator converter (ISGC) prototype is developed. Experimental results validate the effectiveness of the proposed architecture and strategy, demonstrating their practical applicability and superiority in the AAV power generation system.

This article proposes a sensorless fault-tolerant control strategy for a single-stator dual-rotor contra-rotating permanent magnet synchronous machine (CRPMSM). The proposed approach addresses the fundamental challenges arising from single current measurement and strong multiplicative coupling between the electrical states of the two counter-rotating rotors. A control-oriented state-space model is established to characterize the coupled dual-rotor electrical dynamics. Based on this model, a full-order sliding mode observer (FOSMO) is developed to reconstruct the composite back electromotive force (back-EMF) without introducing additional low-pass filtering, and its stability and convergence properties are analytically proven. A phase-locked loop is then employed to extract a control-equivalent electrical position from the estimated composite back-EMF, enabling sensorless vector control and seamless transition to fault-tolerant operation under position sensor failure. It is demonstrated that the extracted electrical angle inherently converges to an intermediate position between the two rotor electrical angles, thereby enabling natural torque sharing and synchronous operation without explicit estimation of individual rotor positions. Simulation and experimental results validate stable operation under speed transients and asymmetric load disturbances, demonstrating the suitability of the proposed strategy for high-reliability electric propulsion applications.

Standard modeling methodologies and classic PI control strategies are poorly suited for doubly salient permanent-magnet (DSPM) motors because of their nonlinear magnetic characteristics and commutation-dependent operating behavior. This study establishes a control-oriented nonlinear model for a 12/8-pole DSPM with an internal radial permanent-magnet arrangement. Current- and position-dependent finite-element flux-linkage Jacobians, rotor-position derivatives, and total electromagnetic torque are organized as three-dimensional lookup tables in the stationary αβ frame, thereby retaining the effects of saturation, armature reaction, interphase coupling, and simultaneous nonzero phase currents. Fuzzy-PI control, implemented as a low-complexity nonlinear gain-scheduling approach, provides a practical alternative to computationally intensive advanced algorithms. To optimize the operational performance, a closed-loop control system is introduced, which utilizes an outer fuzzy-PI loop and an inner current hysteresis loop. This fuzzy-PI speed controller is then compared with a conventionally tuned PI controller under the same conditions. The results demonstrate the usefulness of the FEA-derived model for control evaluation and the favorable transient performance of the fuzzy-PI controller.

This paper proposes a hybrid electric vehicle (HEV) transmission system using a doubly-fed induction generator (DFIG) that directly drives an induction motor (IM). The purpose is to reduce the capacity and voltage level of the inverter in the system, thereby reducing costs. The DFIG's rotor is managed by a small inverter, and the IM is directly driven by the DFIG's stator. A speed matching algorithm is developed to optimize the internal combustion engine's (ICE) efficiency and minimize the inverter's power and voltage by adjusting the vehicle's speed in some intervals, that keeps the ICE either idling or in a high-efficiency state. Additionally, the paper introduces a vector control algorithm for the DFIG direct-drive IM integrated system, ensuring high-performance speed control similar to the traditional vector control for single motor. Experiment results prove that this system meets the vehicle's speed control requirements and reduces the inverter's power and voltage to less than 2/3 of the original system.

This paper proposes a rotor topology for loss reduction in a high-speed homopolar inductor motor (HIM) prototype applied to flywheel energy storage systems (FESS). For HIM operating at a high rotational speed up to 20,000 rpm in a weak vacuum environment, rotor eddy current and hysteresis losses are prominent, while heat dissipation is constrained—posing critical challenges to motor reliability and service life. To address this issue, finite element method (FEM) is first employed for loss analysis, mapping the rotor loss distribution and clarifying magnetic circuit characteristics. Based on simulation insights, two rotor tooth optimization schemes are proposed: rotor tooth slotting and silicon steel laminated rotor teeth. Their loss reduction effectiveness is compared by FE simulations. To further suppress losses, a silicon steel sleeve for the rotor connecting shaft is introduced and integrated with the silicon steel laminated rotor teeth, with harmonic analysis conducted to evaluate its harmonic suppression performance. FEM shows the integrated topology achieves an 86.51% reduction in rotor iron loss compared to the solid rotor while maintaining required power output and voltage levels. Guided by simulation results, a prototype with consistent dimensions was manufactured and tested under typical operating conditions, and thermal experimental results indirectly confirm this loss reduction trend. This work demonstrates a rotor-loss reduction approach that is effective for the specific HIM prototype and the high-speed loaded conditions investigated in this study.

This article focuses on the energy extraction system of an aviation double-compound turbo jet under a high-voltage DC multi-generator electrical power system, and conducts research on the parallel operation control strategy of a dual winding induction generator high-voltage DC power generation system. This article proposes a control method for a dual winding induction generator based on droop control. Under the above architecture, the control method and system design are elaborated in detail. Based on the analysis of the generator and power system impedance characteristics, a parameter tuning method for parallel systems is proposed. The effects of generator voltage loop parameters and power distribution ratios on system performance are discussed, providing a basis for the design of parallel systems based on dual-winding induction generators. This article aims to integrate the advantages of parallel power generation systems and double winding induction generators, and conduct preliminary verification through experiments.

Bipolar DC systems have attracted much attention for their ability to provide multiple voltage levels and high power supply reliability. The three-phase voltage source converter (VSC) topology with a coupled ground inductor can suppress midpoint potential fluctuation caused by load imbalance without adding an additional voltage balancer. However, conventional dual-loop proportional-integral (PI) control exhibits slow dynamic response and entails complex parameter tuning, making it difficult to realize both fast AC current tracking and precise DC voltage balancing simultaneously. To address this, this paper proposes a three-loop cooperative control architecture: the voltage outer loop adopts PI control to ensure the stability of the total DC bus voltage; the current inner loop adopts the continuous control set model predictive current control (CCS-MPCC) to realize the fast and accurate tracking of the AC side current; and a zero-sequence control loop balances the positive and negative bus voltages by regulating the ground inductor current. Simulation results demonstrate that the proposed strategy significantly enhances the dynamic response of the bipolar DC converter under load transients and improves midpoint potential balancing performance.

The rim-driven fan (RDF) is a distinctive aviation electric propulsion system where fan blade tips are directly driven by a rim-driven induction motor (RDIM). This configuration offers higher propulsion efficiency and a stronger correlation between fan torque demands and motor output torque. Within this study, a model of the nonlinear load characteristics of the RDF is established, and principles governing the matching of RDIM output performance across diverse flight conditions are derived. A method for determining the rational design boundaries of the RDIM is formulated, which can guide the matching design between the RDIM and different RDFs. These design constraints for the RDIM encompass torque-fan load matching, output power, and power factor requirements. Although the preliminary design satisfies basic operational requirements, significant opportunities exist to enhance system efficiency and power density. A stepwise optimization method for aviation multioperating conditions is proposed, which gradually optimizes independent objectives required for different operating conditions, ultimately targets three balanced core objectives for the Pareto frontier, enables RDIM to achieve system optimization under diverse operating conditions, and enhances RDF propulsion efficiency. A prototype is developed and tested to experimentally validate the efficacy of the proposed design approach.

This paper proposes an emergency power supply system based on a dual-stator winding induction generator (DWIG) operating in parallel with an energy storage system (ESS), enabling a flexible multi-voltage power supply while improving dynamic response and light-load efficiency. A flux-orientated decoupled control strategy combined with a multi-mode operation mechanism is developed to achieve independent regulation of output voltage and power under different operating conditions. A comprehensive cost model considering diesel fuel consumption, power conversion losses, and battery ageing is established, and a real-time energy management strategy based on Pontryagin's Minimum Principle (PMP) is proposed to optimise power allocation between the diesel generator and the ESS. Simulation studies under different load ranges and initial state of charge (SOC) conditions show that the proposed PMP-based strategy achieves a net fuel saving of approximately 0.1-0.4 L compared with the conventional rule-based method. Experimental results further verify the feasibility and effectiveness of the proposed control and energy management strategy.

This paper proposes a vector control algorithm based on overall current loop pre-excitation for a doubly-fed induction generator (DFIG) drive system used for transmission loading. Traditional full-power converter drive systems are costly in high-voltage and high-power applications and result in higher losses. Utilizing the structure of a DFIG directly driving an induction motor (IM), with the rotor side controlled by a small power inverter and the IM directly driven by the stator of the DFIG, can reduce the cost, size, and capacity of the inverter. However, the IM's voltage-to-frequency (V/F) control restricts dynamic performance under load variations. Addressing these issues, the algorithm proposed in this paper reduces system cost while enabling stable startup and improving the dynamic response of the control system.

The speed signal plays a vital role in the starting/generation system of dual winding induction generator (DWIG). However, due to the poor working environment, the sampling of the speed signal is limited. Therefore, based on the velocity control strategy of the sliding mode observer and the mathematical model of the DWIG, the shortcomings of traditional sliding mode velocity control are analyzed in this article. Based on the principle that the two sets of windings of a double-winding motor are tightly coupled and the flux link is connected, the mechanical parameters of the traditional sliding mode observer are replaced by those on the power winding side that can be observed in real time, thus reducing the inaccurate observation caused by complex conditions and realizing the precise control of the sliding mode without velocity. The compatibility and efficiency of starting control and generation control of DWIG are improved, and the smooth transition and stable generation of the DWIG are ensured.

Electric vertical take-off and landing (eVTOL) aircraft has emerged as one of the promising platforms for nextgeneration low-altitude aircraft due to the low noise and the free emission. To guarantee safety and reliability during flight, it is crucial to accurately estimate the key parameters of eVTOL batteries. However, the continuously high-rate current during the flight mission poses significant challenges, hindering the direct application of existing battery state estimation algorithms from terrestrial electric vehicles to eVTOL applications. In addition, most state of health estimation methods for eVTOL applications lack the in-depth understanding of battery aging, such as the battery degradation modes (DMs). To overcome the above issues, this paper presents a concurrent estimation framework for multiple aging parameters of eVTOL batteries using the specific flight data. First, the evolution of measurements during flight throughout the aging is investigated, and the coupling relationships among battery parameters are analyzed. Secondly, the main DMs are calculated based on differential voltage curves. Then, the impacts of different flight scenarios on battery DMs are discussed. Thirdly, three measured sequences, including the current, the voltage, and the integral current, are selected to construct the input matrix through the correlation analysis and the consistency evaluation. Subsequently, a multi-parameter co-estimation model is trained by a bottleneck-architecture residual network. Lastly, a publicly available eVTOL battery dataset is employed to verify the effectiveness and the generalizability of the proposed method. The results show that percentage versions of the mean absolute error and the root mean squared error are within 2.5 % and 3.0 %, respectively.

In the system of a three-phase Buck PWM rectifier, the time delay and the variation in grid-side inductance can affect system stability and induce distortion in the grid-side current. To address this issue, this paper proposes a robust predictive deadbeat control strategy for the three-phase buck-type PWM rectifier to enhance the system's robustness and reduce the total harmonic distortion (THD) of the grid-side current caused by time delay and inductance mismatch. The deadbeat control model with delay is analyzed in the z-domain, and the impact of inductance mismatch on system stability is examined. The linear interpolation method and Luenberger observer are employed to predict the grid-side voltage and current, respectively, with stability analysis performed using the root locus technique. The simulation results demonstrate the effectiveness of the proposed control method.

This article proposes an optimized dual-stator unequal-slot permanent magnet synchronous motor (DSUS-PMSM). An unequal-slot structure has been used, with distributed windings in the outer stator and concentrated windings in the inner stator. The split ratio, stator slot type, skew angle, rotor construction, pole-arc coefficient, and other parameters have been optimized. An optimized motor model has been created, and finite-element analysis is performed. The results show that the proposed motor has a higher power density and can effectively reduce torque ripple and loss. A prototype of the proposed structure has been produced for experimental verification and provides the back electromotive force waveform and structure temperature.

The dual-winding induction generator power system, as a device capable of integrated ac-dc generation, plays a crucial role in the stability of the power generation system and the quality of power supply due to its dynamic performance and stability. This article proposes an improved control scheme to suppress the impact of magnetic field coupling effects in a novel five-phase and three-phase dual winding induction generator under ac-dc load disturbances. First, based on the flux linkage and power distribution of the five-phase and three-phase dual-winding induction generator, a dynamic mathematical model of its output ac and dc voltages is established. An improved linear active disturbance rejection control (LADRC) scheme is proposed novel application in ac-dc integrated generation control. By extending the order of the linear extended state observer (LESO), the compensation is performed for the generator's nonlinear characteristics and the total disturbance, which includes effects from system coupling and external disturbances. Experimental results demonstrate that the proposed control strategy enhances the dynamic response speed of the dual-winding machine, effectively mitigates the impact of coupled load disturbances on the system, and exhibits good robustness when facing parameter variations.

To enhance thrust and efficiency in rim-driven ducted fan, the rim-driven induction motor with the laminated stack rotor has been adopted. However, Considering the demand for high speed in aviation electric propulsion, the laminated stack rotor encounters significant challenges associated with stress concentration and breakage. The tip speed of the rotor inner diameter corresponds to the tip speed of the built-in fan, while the tip speed of the rotor outer diameter will be higher. Consequently, the peak Von Mises stress near the outer and inner surfaces of the rotor core becomes considerably high. Against this backdrop, this study analyzes stress distribution characteristics specific to the rim drive topology with different rotor bar shapes. To prevent the laminated stack rotor from experiencing failures, the study proposes an optimized rotor structure and reinforced structure to alleviate the stress concentration. Simultaneously, employing a new stress design in rotor construction may lead to a decline in output performance or an upsurge in losses. To reduce the iteration of stress optimization design and electromagnetic performance analysis, an evaluation methodology for coupling mechanical and electromagnetic characteristics by analyzing the system energy of rotor with different bar shapes is suggested. The stress optimization design was validated through prototype experiments eventually.

It is cost-efficient to attain high-performance position control on the semiclosed loop structure. However, the control deviation exists on the load side due to the low-stiffness shaft. This article constructs an observer-based full-closed loop position control (OFPC) using a state feedback method that offers the advantage of flexible pole assignment and high positioning accuracy. The utilization of an observer will introduce the nonlinear elements in the closed-loop system, which causes a limit cycle potentially. To solve this issue, the disturbance function has been developed, and the limit cycle phenomenon induced by motor and load friction has been studied emphatically via the describing function approach. Furthermore, this article presents an effective control gain boundary to prevent the load side limit cycle, and offers an adaptive compensation algorithm of motor friction to suppress the residual limit cycle. The effectiveness of the proposed strategy is validated on the linear tooth belt drive. The experimental results indicate that the OFPC scheme can achieve relatively high positioning performance.

This paper proposes a novel controller design method for servomechanism with elasticity to guarantee the position and speed response damping as well as dynamic. The disturbance observer (DOB), offering extra torque shaft feedback, promotes the natural frequency of the speed loop to attain anti-resonant frequency. The speed reference is compensated reasonably in speed loop output, taking the optimal amplitude-frequency response into account. The position loop proportional and feedforward gain are designed to achieve good position response using the polynomial design method. However, a high dynamic response may impose the speed controller saturates, which inevitably induces severe motor speed and shaft torque oscillation. The auxiliary proportional-derivative (PD) controller is proposed to compensate for the dynamic of shaft torque under the controller saturation, which achieves the protection of the drive train. The parameter design method in the proposed controller is simple and distinct. Experimental results validate the effectiveness of the proposed strategy.

In this paper, a dynamic current control strategy based on reduced-order observer (ROO) is proposed for dual stator-winding induction generator (DWIG), in order to suppress the disturbances and to improve the current dynamic response. Because of two stator windings, the mathematical model of DWIG is more complex and has higher order and more coupling terms, which makes poor current dynamic performance. In the proposed control strategy, by establishing the mathematical relations between the control winding (CW) current, power winding (PW) currents and rotor flux, the total disturbances of CW current are determined, observed by ROO and introduced into the current-control loop for feedforward compensation. The influence of observer parameters and parameter mismatch on the stability, rapidity and disturbance-rejection ability is also analyzed, which guides the parameter tuning of the ROO. The simulation and experiments verify the validity of the proposed current controller. The dynamic performance of is improved and the dynamic regulation time of current is shortened by more than half compared to traditional proportional-integral current controller. Moreover, the proposed current control strategy also has good robustness under the variation of machine parameters.