This paper identifies the most promising electric power system (EPS) architecture for a future more electric aircraft (MEA) based on reviews and evaluations of both system weight and stability feature of the existing EPS architectures. When comparing the overall system weight of different architectures, various aspects, including voltage generation, wiring system, ground operation, power conversion and complexity of integrating alternative energy sources, are considered. After choosing the possible candidates among all the possible architectures by using weight-saving criterion, stability features for the initially selected candidates are further evaluated. Necessary simulation studies are carried out in Matlab/Simulink to prove the correctness of stability study. Finally, the one both good at weight saving and with highest stability region is deemed as the most promising EPS architecture for future MEAs.

A unified power controller for variable-speed fixed-pitch wind energy conversion system (WECS) is designed covering the whole range of wind speed in this paper. The proposed controller is composed of a modified maximum power point tracking (MPPT) controller in low wind speed and a new constant speed and constant power controller in high wind speed. For the former, a combination of modified hill climb searching (HCS) and power signal feedback (PSF) MPPT algorithms is used. The modified HCS method is activated to search for the maximum power point (MPP) first, which is followed by the PSF method once one MPP is found. By using this controller, not only the a priori knowledge of the aerodynamic characteristics of turbine blades is avoided, but also low torque/power ripple is achieved; for the latter, a new auxiliary passive stall control method is proposed. It temporarily increases the output power to force the turbine to operate in deep stall regime, thus to decrease the captured power of the turbine. The proposed controller is implemented on a digital signal processor. The validity of the proposed method is verified by experimental results done on a 10-kW WECS.

In this paper, a framework for stability analyses of a typical inverter-based islanded microgrid with two types of nonlinear loads is presented, namely ideal constant power loads (CPLs), which are the loads supplied by tightly regulated power electronics converters, and dynamic CPLs, which are used to represent motor-drive systems with large time constants. The comprehensive dynamic model of the considered microgrid is first developed, based on which a bunch of small-signal models are deduced using Taylor expansion made at different stable operating points. Afterward, eigenvalue-theorem-based stability analysis and parametric sensitivity analysis are successively performed on the obtained small-signal models to verify the stability of the system, predict the system's unstable regions, and identify the effects of parameters on the stability boundaries. In the meantime, the impacts of different kinds of nonlinear loads on the system stability are studied. Hardware-in-the-loop (HIL) real-time simulation platform of a 30-kVA microgrid, which is mainly formed by a 10-kVA photovoltaic (PV) system, a 10-kVA wind energy conversion system, a 10-kVA lithium-ion battery energy storage system, and two CPLs, is established in Typhoon HIL 602 device. The validity of the theoretical results is verified by real-time simulation results.

The interleave boost converter (IBC) has been used as the interface converter between the low voltage electrical energy sources, such as lithium-ion battery banks, solar panels and fuel cells, and the DC-bus of DC microgrids. With increasing penetration of tightly regulated power electronic loads, which behave as constant power loads (CPLs), the stability of microgrid DC bus voltage that is fed by the IBC is threatened by the loads‚ negative incremental impedance feature. To ensure the stability of bus voltage, this paper proposes a nonlinear disturbance observer (NDO) based sliding mode control algorithm. The proposed algorithm with excellent robustness, low computational burden and no extra hardware cost. A generalized average state-space model is proposed to facilitate the control design. In addition, a NDO is employed to estimate the output power of IBC rapidly and accurately. To verify the effectiveness of the proposed algorithm, simulation and experimental results are presented.

In this paper, a decentralized energy management strategy (EMS), which is based on a modified droop control, is proposed for a fuel cell (FC)/supercapacitor (SC)-based auxiliary power unit (APU) of a More Electric Aircraft (MEA). The proposed EMS is able to split the load power automatically into low- and high-frequency components and allocate them to the FC and SC units respectively. Since the proposed EMS is fully decentralized, it features high flexibility and scalability. Furthermore, the proposed strategy is not only suitable for extending the service life of the system because the protection and recovery of the state-of-charge (SoC) of the SC have been considered in doing the energy management, but also can make the system accommodate the regenerative power in a lossless way. The operational principle of the proposed strategy, system design details and performance analysis are elaborated, followed by which experiments based on a 3kW FC/SC-APU are conducted to verify its validity.

In this paper, an enhanced mixed droop control strategy is proposed for fuel cell/supercapacitor-based auxiliary power unit (FC/SC-APU), which is usually used in large electric vehicles, to achieve the dynamic load power allocation in a decentralized way. By applying an adjustable virtual impedance droop scheme to the SC converter and a virtual resistor droop scheme to the FC converter, the SC is able to buffer the fast-changing or pulsating load power flow, leaving the FC only providing the average load power. Since this method is fully decentralized, it features high flexibility and scalability. Furthermore, the proposed strategy is very suitable for extending the system's service life because the recovery and operational limit of the state-of-charge (SoC) of SC have been considered in the power allocation. The operational principle of the proposed control strategy and the system design are elaborated, followed by which real-time simulations are conducted to verify theoretical analyses.