Electric drives are an essential part of more electric aircraft (MEA) applications with ever-growing demands for high power density, high performance, and high fault-tolerant capability. High-speed motor drives can fulfill those needs, but their speeds are subject to the relatively low dc-link voltage adopted by MEA. The power inverters are thus expected to efficiently and effectively manage that limited voltage. A recently popular topology is represented by the dual inverters. They are featured by inherited fault tolerance, a high dc-link voltage utilization, and an excellent output power profile. This article aims to present a comprehensive review of different structures based on the dual inverter. To meet the stringent requirements of MEA applications, three performance aspects, including the voltage utilization, the inverter output quality, and the fault-tolerant capability, are selected. Based on the chosen performance metrics, the key features of adopting dual inverter topologies against other converter selections are explicitly demonstrated. Finally, a practical guideline for choosing suitable dual inverters for different MEA applications is provided.

This paper proposes a capacitor voltage regulation method for the dual converter with a floating bridge for aerospace applications. This topology has previously been reported, but with a constrained voltage utilisation factor due to the need for capacitor voltage regulations. In this paper, the effect of switching states on the voltage variation of capacitor is quantitatively modelled and an enhanced space vector modulation scheme with current feedback is proposed to achieve an active control of the floating capacitor voltages. This proposed method also allows further exploitation and utilisation of converter voltage. The relationship between the allowed modulation index of dual converter and load power factor is obtained and expressed using a fitted polynomial equation. The advantages of the proposed method include boosted voltage utilisation and superior performance in term of capacitor voltage balance. These advantages have been proven through simulation and experimental results on RL loads as well as with an open-end winding induction motor. The proposed modulation scheme can boost the converter voltage utilisation by at least 10% while achieving full four-level operation. More importantly, the higher available voltage allows extending the constant torque region of the motor, the further beginning of field weakening operation could be postponed.

The estimation of the state of health (SOH) of lithium-ion batteries (LIBs) plays an important role in ensuring the safe and stable operation of LIB management systems. In order to more accurately predict SOH, a model based on a sparse self-attentive transformer (SSAT) with multitimescale feature fusion is proposed. The SSAT follows an encoder-decoder structure construction, and the model inputs are the extracted health indicators and SOH sequences. The encoder stacks three cross-stage partial (CSP)-ProbSparse attention self-attention blocks, between every two CSP-ProbSparse attention blocks, connections are made by dilated causal convolution and max-pooling layers to obtain exponential growth of the sensory field. All the feature maps output from the self-attention blocks are integrated by multiscale feature fusion, and finally, the appropriate feature dimensions are fed to the decoder through a transition layer to obtain the estimation of SOH. Numerous comparative and ablation experiments have demonstrated that the SSAT model achieves superior performance in a wide range of situations.

This paper studies a dual inverter supplied by a DC-link and a floating capacitor (FC), emerged as a promising inverter topology for motor drive applications. For this type of inverter, the voltage ratio between the DC-link and the FC can be actively controlled. This ratio design is crucial as it essentially defines both the DC-link voltage utilization and the inverter output quality. Several voltage ratios have previously been discussed to enhance the dual inverter performance, but only one aspect, either the voltage utilization or the output quality, is investigated. As a result, although one performance aspect can be improved, the other aspect has been adversely affected. In this work, a comparative study considering both aspects is carried out for all the possible voltage ratios. Based on this analysis, the optimal ratios for different inverter modulation indices are identified. This is followed by proposing a ratio selection strategy to double the voltage utilization without degrading the output quality. This strategy enables an electric drive to work at a higher maximum speed without flux weakening for a given DC-link voltage. The claimed advantages have been proved by experimental tests on an open-end windings induction motor drive.

In the aircraft electric starter/generator system, the three-level neutral-point-clamped converters play a crucial role in driving turbofan engines and delivering onboard electrical power. However, the conventional pulsewidth modulation (PWM) strategies face the challenge of capacitor voltage deviation, large common-mode voltage (CMV), and extra switching losses. Regarding the characteristics of the studied wide-speed range aerospace drives, the modulation scheme needs to be designed according to its operating conditions. To tackle the above demerits, a hybrid active modulation approach is, hence, proposed in this article. By the coordinate-based PWM, the nearest-three-vector is used in the startup process as the neutral-point (NP) voltage balance can be realized with fewer switching intervals; when the drives run in generation mode, an enhanced carrier-based virtual-space-vector modulation technique is involved, which aims to eliminate NP voltage fluctuation, suppress CMV, and simplify the modulation process. With the help of bias-offset injection in the time and voltage domain, capacitor voltages can be effectively kept at a balanced state even though the imbalance exists. The validity of the presented algorithm is proved by simulation and experimental results obtained from a 45 kW, 32 kr/min aircraft starter/generator test rig.

Solid-state power controllers (SSPCs) have been received increasing attention as they can configure the electrical system and protect the system by fast tripping mechanism at the same time. Although the high-voltage direct current (HVDC) electrical system can bring sustainable savings on the cables' weight and losses, the protection can be considerably challenging. SSPCs have been successfully utilized for 28V DC aircraft onboard network. However, high-voltage ones are impeded by the vast over-voltage and the excessive losses generated from SSPC switching. This paper tries to fill this gap and presents the development of high-power SSPCs for a ±270VDC network of a future turboprop aircraft. Comprehensive designs of proper over-voltage suppression along with SSPC thermal management are presented in this paper. Besides, a comparative study on the SSPC device is carried out. Two prototypes, including a single MOSFET module and paralleling several discrete MOSFET devices, are built and then tested in the experiment. It has been validated that the proposed voltage clamping design cannot only effectively suppress the over-voltage, but also limit the SSPC temperature increase during switching for both candidates. After comparing the conduction losses, maximum junction temperature, power density, weight and volume, the single device solution is recommended as a preferable SSPC option for future aircraft.