The development of the DC microgrid system on-board has promoted the development of the DC circuit breaker, due to that the short circuit fault may cause serious damage to the system. However, the traditional DC circuit breaker exists many problems such as long period of fault interruption, complex circuit structure, existing arc, low reliability and low anti-interference. Aiming to solve these problems, a novel solid-state DC circuit breaker was proposed in this paper. Firstly, this paper analyzes the working principle and process of the circuit in detail according to the results of the simulation based on Saber. Secondly, this paper gives the criteria on how to choose the parameters of the components correctly in the circuit. The concept of the maximum fault resistance according to the minimum fault current is also introduced. Moreover, this paper analyzes the influence of the minimum fault ramp rate on the circuit performance. Finally, experimental results verify that the performance of this novel solid-state circuit breaker agree with theoretical analysis.

In islanded AC microgrids, loads are supplied by parallel inverters-based distributed generation (DG) units. Accurate power sharing, which is always degraded by the mismatched line impedances of DG units, is an essential mission. Reshaping the output impedance of DG units is an effective method to improve power sharing performance via eliminating the impedance mismatch. This paper classifies and summarizes various impedance-reshaping-based power sharing strategies. Firstly, the comprehensive evaluation criteria of the power sharing methods are illustrated in terms of power sharing accuracy, unbalanced and harmonic power sharing, influence on voltage regulation, dependence on communication and feasibility in practical applications. According to the operating principles, the existing impedance reshaping methods are categorized into four groups: fixed virtual impedance, adaptive virtual impedance regulation, impedance droops, and reconfiguration of inner loops. Then the advantages and disadvantages of the four groups of impedance reshaping techniques are discussed respectively. Finally, the characteristics of different impedance-reshaping-based power sharing methods are summed up and future research trends of impedance reshaping strategies for power sharing improvement in islanded AC microgrids are predicted.

With the development of high-altitude and long-endurance unmanned aerial vehicles (UAVs), optimization of the coordinated energy dispatch of UAVs’ energy management systems has become a key target in the research of electric UAVs. Several different energy management strategies are proposed herein for improving the overall efficiency and fuel economy of fuel cell/battery hybrid electric power systems (HEPS) of UAVs. A rule-based (RB) energy management strategy is designed as a baseline for comparison with other strategies. An energy management strategy (EMS) based on fuzzy logic (FL) for HEPS is presented. Compared with classical rule-based strategies, the fuzzy logic control has better robustness to power fluctuations in the UAV. However, the proposed FL strategy has an inherent defect: the optimization performances will be determined by the heuristic method and the past experiences of designers to a great extent rather than a specific cost function of the algorithm itself. Thus, the paper puts forward an improved fuzzy logic-based strategy that uses particle swarm optimization (PSO) to track the optimal thresholds of membership functions, and the equivalent hydrogen consumption minimization is considered as the objective function. Using a typical 30 min UAV mission profile, all the proposed EMS were verified by simulations and rapid controller prototype (RCP) experiments. Comprehensive comparisons and analysis are presented by evaluating hydrogen consumption, system efficiency and voltage bus stability. The results show that the PSO-FL algorithm can further improve fuel economy and achieve superior overall dynamic performance when controlling a UAV’s fuel-cell powertrain.

Instead of bulky electrolytic capacitors, active power decoupling circuit can be introduced to a single-phase converter for diverting second harmonic ripple away from its dc source or load. One possible circuit consists of a half-bridge and two capacitors in series for forming a dc-split capacitor, instead of the usual single dc-link-capacitor bank. Methods for regulating this power de-coupler have earlier been developed, but almost always with equal capacitances assumed for forming the dc-split capacitor, even though it is not realistic in practice. The assumption should hence be evaluated more thoroughly, especially when it is shown in the paper that even a slight mismatch can render the power decoupling scheme ineffective and IEEE 1547 standard to be breached. A more robust compensation scheme is thus needed for the dc-split-capacitor circuit, as proposed and tested experimentally in the paper.

With the development of More/All-Electric Aircraft, especially the progress of hybrid electrical propulsion or electrical propulsion aircraft, the problem of optimizing the energy system design and operation of the aircraft must be solved regarding the increasing electrical power demand-limited thermal sink capability. The paper overviews the state of the art in architecture optimization and an energy management system for the aircraft power system. The basic design method for power system architecture optimization in aircraft is reviewed from the multi-energy form in this paper. Renewable energy, such as the photo-voltaic battery and the fuel cell, is integrated into the electrical power system onboard which can also make the problem of optimal energy distribution in the aircraft complex because of the uncertainty and power response speed. The basic idea and research progress for the optimization, evaluation technology, and dynamic management control methods of the aircraft power system are analyzed and presented in this paper. The trend in optimization methods of engineering design for the energy system architecture in aircraft was summarized and derived from the multiple objective optimizations within the constraint conditions, such as weight, reliability, safety, efficiency, and characteristics of renewable energy. The cost function, based on the energy efficiency and power quality, was commented on and discussed according to different power flow relationships in the aircraft. The dynamic control strategies of different microgrid architectures in aircraft are compared with other methods in the review paper. Some integrated energy management optimization strategies or methods for electrical propulsion aircraft and more electric aircraft were reviewed. The mathematical consideration and expression of the energy optimization technologies of aircraft were analyzed and compared with some features and solution methods. The thermal and electric energy coupling relationship research field is discussed with the power quality and stability of the aircraft power system with some reference papers. Finally, the future energy interaction optimization problem between the airport microgrid and electric propulsion aircraft power system was also discussed and predicted in this review paper. Based on the state of the art technology development for EMS and architecture optimization, this paper intends to present the industry’s common sense and future trends on aircraft power system electrification and proposes an EMS+TMS+PHM to follow in the electrified aircraft propulsion system architecture selection

The balanced, unbalanced and harmonic current sharing inaccuracy caused by the mismatched wire impedances of distributed generation (DG) units influences the normal operation of islanded microgrids. To deal with this issue, an iterative virtual impedance regulation (IVIR) strategy is proposed in this paper, both the resistive and reactive parts in the output impedances of DG units are regulated. The whole process is decomposed into several successive iterations. In each iteration, the fixed virtual impedance and adaptive virtual impedance regulation are combined to generate a virtual resistance increment and uniform virtual reactance increment according to the uniform output current magnitude and phase angle respectively. Based on these increments, the virtual impedance at fundamental-negative and harmonic frequencies also are modified. With the proposed strategy, all the balanced, unbalanced and harmonic current sharing is accurate with a relatively small virtual impedance. Only the local current information is required for the IVIR process, and the communication is merely used to exchange the VIR mode status flags at the beginning and the end of the IVIR process, the dependency on communication is minimized. The feasibility of the proposed strategy is verified with the simulation and experimental results.