The online power allocation strategy based on the improved genetic algorithm is proposed to address the problems of the hybrid energy storage system, such as the difficulty in achieving the relative optimal power allocation among the energy storage when smoothing the wind power fluctuation or the lack of constraints on the climbing ability of the energy storage equipment. Firstly, the improved genetic algorithm model is proposed to address the problems of genetic algorithm. secondly, the improved genetic algorithm online power allocation strategy is proposed to achieve the relative optimal power allocation among energy storage with the objective function of minimizing the power loss and reducing changes in the state of charge. Finally, the online power allocation strategy model is built in Matlab/Simulink, and the strategy is compared with other online allocation strategies (such as state of charge based power allocation and rule control based power allocation) in terms of climbing capacity, charging and discharging times, power loss and deviation from the middle value of charge state, etc. to verify the feasibility and advantages of the proposed power allocation strategy in this paper.

Vienna rectifiers can be treated as promising rectification units for transportation electrification systems because of their high efficiency and reliability. However, commonly used modulation techniques for Vienna rectifiers, such as space vector pulse width modulation, heavily depend on the generator's parameters, including winding inductance and rotor position, leading to reduced control performance under complex operating conditions. This article proposes a novel control strategy for the three-phase four-wire Vienna rectifier connected to a permanent magnet synchronous generator to address this issue. By adjusting the input impedance of the rectifier to be purely resistive, automatic power factor correction and current quality enhancement are achieved. The effectiveness of the proposed method is validated through experiments performed by a 500 W prototype.

The precise in-circuit impedance extraction in a switched-mode power supply (SMPS) is essential for the optimal design of electromagnetic interference (EMI) filters. The design of EMI filter parameters based on in-circuit impedance has already been widely investigated in the literature, but the variation characteristics of the in-circuit impedance for an SMPS is still a research gap and needs further study. In this article, based on the concept of the inductive coupling approach, a novel method for in-circuit impedance modeling is proposed. Subsequently, an accurate in-circuit impedance modeling is derived, which indicates that the in-circuit impedance for the SMPS is related to the external impedance, the modal impedance under different switching modes, and the proportion of each switching mode. Based on the derived model, the variation characteristics of the in-circuit impedance are revealed, which can provide valuable guidance for the design of EMI suppression measures. Finally, the simulation results show good agreement with the calculated results. Experimental verification further indicates that the model accurately characterizes the impedance of the switching power supply across the range of 10 kHz to 30 MHz, with amplitude deviation within 3 dB and phase deviation below 6 degrees. This work provides a quantitative foundation for designing electromagnetic interference suppression strategies, enabling more precise filter optimization over a broad frequency range.

With the increasing penetration of converter-interfaced renewable energy sources, converter-dominated power systems (CDPS) have become increasingly vulnerable to wideband oscillations. Impedance-shaping control has been recognized as an effective solution for oscillation mitigation. However, existing impedance-shaping approaches offer suffer from inconsistent design objectives and complicated parameter tuning requirements, which limit their applicability in practical CDPS. To address these issues, this paper proposes a broadband admittance-shaping control strategy incorporating a fundamental-frequency reactance coefficient regulation mechanism to improve compatibility among diverse converter types. Furthermore, a coordinated admittance-shaping control scheme is developed for converters with dominant oscillatory dynamics. Specifically, distributed coordination among multiple converters is achieved through online adjustment of admittance-shaping coefficients according to oscillation participation factors, oscillation conditions, and converter capacities. Hardware-in-the-loop (HIL) experimental results validate the theoretical analysis and demonstrate the effectiveness of the proposed strategy in enhancing system stability and suppressing sideband oscillations.

To meet the cross-timescale response requirements of new electrified loads, lithium batteries and supercapacitors are being integrated into onboard electrical power systems via DC/DC converters. Despite the rapid response and energy recovery capabilities of these storage units, the onboard hybrid power systems remain prone to significant power quality degradation and instability under transient conditions such as wide-range load transients, partial source failures, and pulsed loads with a high peak-to-average ratio. To address these issues, this article proposes a composite controller that integrates a fixed-time sliding mode disturbance observer (FTSMDO) with a prescribed performance controller (PPC). The FTSMDO is designed to estimate lumped disturbances, upon which a PPC is developed using the backstepping method. This approach enhances the system’s capability for rapid voltage recovery under various transient events and ensures large-signal stability. Finally, the effectiveness of the proposed composite control strategy is validated through both simulation and experimental results.

The occurrence of open-phase faults in five-phase permanent magnet synchronous motors (5Ph-PMSMs) disrupts the current balance among the remaining healthy phases, resulting in the introduction of second and fourth harmonics into the position estimation. To address this challenge, this paper proposes an innovative sensorless control approach specifically for open-phase 5Ph-PMSM systems. This methodology integrates improved second-order generalized integrators (ISOGIs) to effectively mitigate undesirable harmonics and extract the positive sequence component from the distorted back electromotive force (back-EMF). Additionally, an adaptive neutral-voltage compensator is implemented to alleviate the asymmetry present in the back-EMF, thereby further enhancing the precision of the sensorless control. The effectiveness of the proposed methodology is corroborated through rigorous experimental results.

Grid-connected inverters (GCI) operating with the grid-following (GFL) control tend to suffer from unstable problem under weak grids with low short-circuit ratios (SCR). The improved GFL control can enhance the small signal stability of GCI under weak grids, but it will cause dynamic performance degradation and remains unstable under extreme weak grids. It is reported that the GCI can maintain stable under weak or even very weak grids if the grid-forming (GFM) control is adopted. However, it may face unstable under strong grids. Both the GFL and GFM control strategies are difficult to meet the stability requirements. Therefore, this paper proposes a GFL and GFM hybrid synchronous control strategy for the GCI. It can adaptively synthesis the GFL and GFM control according to the real SCR. Thus, the GCI can stably operates both in the strong grid or weak grid, and its stability margin can be effectively improved. Then, an optimal weighted factor analysis method based on similar diagonalization of feedback sensitivity matrix is proposed to optimize the control performance of the hybrid synchronous control. Finally, simulation results verify the feasibility of the proposed strategies.

With the increasing requirement of power density of power electronic converters, it is of great importance to design the electromagnetic interference (EMI) filter to meet electromagnetic compatibility (EMC) standards, meanwhile featuring small size. CL/LC/CLC are the three commonly used topologies. Traditionally, the selection of the topology is determined by the mismatch of noise source impedance and load impedance, ignoring its mismatch with filter components impedance. Therefore, it is still not clear how to accurately select and design the EMI filter. In order to solve this problem, the concept of capacitance allocation coefficient is first introduced in this article to treat the CL/LC/CLC three different topologies with a uniform form, i.e., capacitor-inductor-capacitor (CLC) structure. The unified expression for the insertion loss (IL) of CL/LC/CLC EMI filter is then deduced. From the perspective of achieving maximum IL, an optimal allocation method of the CLC filter capacitance under different noise source impedance is elaborately studied which can quantitatively optimize the topology selection and parameter design to reduce the filter volume. Finally, a corresponding design method of EMI filter is proposed and an EMI filter is designed for a converter based on the proposed method. Simulation and experimental results verify the effectiveness of the proposed method.

Hybrid power supply systems (HPSSs), which integrate the dynamic properties of different power sources, are a promising solution for transportation electrification systems. However, extreme cases such as large variations of load like large step-changing load and high peak-to-average ratio pulsed power load are highly susceptible to power supply system destabilization, which is beyond the scope of small-signal analysis. In this article, a comprehensive large-signal stability analysis for HPSSs considering variation in virtual impedance droop parameters and proportional and integral (PI) regulators under extreme load switching conditions is conducted based on the region of attraction estimation (ROA). On this basis, the impact of system parameters and load power on the large-signal stability is elaborated. The stability of the system is greatly improved by the adoption of active capacitors to absorb the pulsed power. The effectiveness of the proposed large-signal stability analysis method and the correctness of the analyzing results are verified through experiment results.

Droop control is widely utilized in parallel inverter control within microgrids. However, conventional droop control strategy struggle to achieve reactive power sharing and circulating current suppression among multiple parallel inverters due to mismatched output impedances. To address this issue, this paper proposes a current-sharing strategy for single-phase parallel inverters based on multi-loop cooperative control. The proposed control strategy comprises a voltage-current loop, a droop control loop, a virtual impedance loop, and a reactive power tracking loop. Under the multi-loop cooperative control framework, the virtual impedance can be adaptively adjusted to compensate for output impedance discrepancies, thereby achieving reactive power balance and output current sharing in the parallel system. Finally, the effectiveness and feasibility of the control strategy were verified through experimental results.

The application of wide-band gap (WBG) semiconductor devices is extremely beneficial to the compact design and power conversion efficiency enhancement of high power medium voltage (MV) power electronic transformers (PETs). However, the insulation system is exposed to high-frequency and high slew rate (dv/dt) electrical stresses, the defect induced partial discharge (PD) is more severe, which can significantly affect life and reliability. PD tests on casting epoxy resin are carried out using high-frequency pulse voltage at the slew rate of 70 kV/mu s with the repetitive frequency ranging from 10 to 100 kHz. Subsequently, the insulation degradation caused by frequency-induced PD is explored based on physical and chemical techniques. The results reveal that the degree of PD intensifies with the increasing frequency. The discharge repetition rate increases by 1220% at 100 kHz, the cumulative discharge amplitude increases by 41.8%. The frequency-induced heating effect becomes more significant as the frequency increases, while the insulation damage can be reflected by changes in morphology, chemical bonding, carbon, and oxygen content. The degradation of epoxy resin is more obvious at higher frequency, the atomic content of carbon and oxygen decreases by 17.06% and increases by 11.4%, respectively, with a large number of bond breaking changes. While it tends to increase working frequency of MV PET utilizing WBG, leads to challengeable insulation degradation, which must be considered during the preparation of epoxy resin.

Power electric source composed of fuel cell (FC) and supercapacitor (SC) is regarded as an appealing onboard hybrid power supply system (HPSS) for electrical propulsion-based aircraft. However, with the ever-growing electrification of the aircraft, the type and number of the electrified sources and loads increase significantly, where a large number of onboard loads are constant power loads (CPL). As a consequence, the interconnected system tends to suffer from instability problem. This paper first establishes the impedance model of FC and SC, and corresponding simulation models were built to verify the accuracy of the impedance model. To clearly reveal the effective of the key parameters, sensitivity analysis is adopted to guide the optimization of the parameters, thus, a better distribution of power between FC and SC unit is achieved. Moreover, when connected to CPL, the influence of control parameters and the number of parallel FC-SC units on system stability is investigated. All the analyses are verified via simulation results eventually. The conclusions of this paper can serve as the basis for the stability analysis and parameters design of more complex aircraft power systems.

In order to solve the problem of calculating the reasonable completed bridge state of a self-anchored hybrid cablestayed suspension bridge (SA-HCSB), this paper proposes an analytical method. This method simplifies the main beam into a continuous beam with multi-point rigid supports and solves the support reaction forces. According to the segmented catenary theory, it simultaneously solves the horizontal forces of the main span main cables and the stay cables and iteratively calculates the equilibrium force system on the main beam in the collaborative system bridge state while completing the shape finding of the main span main cable and stay cables. Then, the horizontal forces of the side span main cables and stay cables are obtained based on the balance of horizontal forces on the bridge towers, and the shape finding of the side spans are completed according to the segmented catenary theory. Next, the difference between the support reaction forces of the continuous beam with multiple rigid supports obtained from the initial and final iterations is used to calculate the load of ballast on the side span main beam. Finally, the axial forces and strains of each segment of the main beam and bridge tower are obtained based on the loads applied by the main cable and stay cables on the main beam and bridge tower, thereby obtaining analytical data for the bridge in the reasonable completed state. In this paper, the rationality and effectiveness of this analytical method are verified through a case study of a SA-HCSB with a main span of 720m in finite element analysis. At the same time, it is also verified that the equilibrium force of the main beam under the reasonably completed bridge state can be obtained through iterative calculation. The analytical algorithm in this paper has clear physical significance, strong applicability, and high accuracy of calculation results, enriching the shape-finding method of this bridge type.

High voltage DC systems have become one of the dominant electrical power system architectures for future applications in more electric aircraft. Accurate model and stability analysis of these systems are crucial. However, past studies typically use the DC impedance model, which may overlook some system characteristics. Additionally, the impedance model needs repetitive adjustment as the source side and the load side change. In this paper, an AC-DC coupled impedance model is proposed, which can model the overall system into submodules. The resulting converter impedance is independent of load and source-side parameters, which means that changes on the AC and DC side have no effect on the converter impedance model. Furthermore, this model is more accurate as it includes AC, DC, and AC-DC coupled terms, better aligning with actual onboard characteristics. The modelling process, frequency sweep verification, and stability analysis in MATLAB/Simulink are provided in this paper.

To enhance the reliability of the power grid in islanded scenarios, a grid-forming energy storage system is proposed to maintain stable isolated power grid operation. First, establish a power supply structure and frequency modulation and voltage regulation control strategy for VSG-controlled grid-forming energy storage system. Secondly, a pre-synchronous grid-connected operation control strategy using the Clark transform method is presented to achieve smooth grid-connected operation of the energy storage system under operation of the isolated power grid. Finally, a simulation case analysis of the proposed method is carried out on. The simulation results indicate that the grid-forming energy storage system based on VSG control technology can ensure the stable operation of the isolated power grid.

China attaches great importance to the development of hydrogen energy and fuel cell industry, and a series of industrial policies and relevant national departments have repeatedly mentioned the direction of industrial development. This paper comprehensively sorts out and analyzes the relevant domestic and foreign standards focusing on fuel cell system for vehicle use, suggest that the standard system construction of them should center on key components and performance indicators, and establishes a four-level system from performance indicators to components. On several key performance indicators that restrict the large-scale industrialization of fuel cell vehicles, the entire industry should strengthen research.

The large-signal stability analysis of two-stage cascaded dc-dc converter systems is still a troublesome problem due to various limitations of existing stability analysis methods. To address this problem, a large-signal stability analysis method based on Lyapunov's stability theory and the sum-of-squares programming technique is proposed. With the proposed method, one can not only obtain the maximum stability boundary of the system under large disturbances, which helps understand the system's transient behaviors, but also can analyze the influences of system parameters on the stability region and identify the dominant parameters. The proposed stability analysis method could provide a practical guide for designing system parameters. The effectiveness of the large-signal stability analyzing results is verified by experimental results.

For the fuel cell-battery-ultracapacitor hybrid energy storage system applied to the transportation electrification system, its energy management system (EMS) has to achieve the expected energy management objectives, including dynamic load power-sharing, state-of-charge regulation of battery and ultracapacitor, regenerative braking capability, etc. Conventionally, such an EMS is achieved in a centralized or hierarchical way, resulting in poor flexibility, scalability, and reliability. In this article, a completely decentralized EMS, which is achieved based on a modified mixed droop control, is proposed to achieve the above objectives. As the implementation of the proposed EMS does not rely on any communication links or common signals, the system cost is reduced. Besides, the system with the proposed EMS is of high reliability as it can still operate well during the outage of one power source due to malfunction. The operational principle of the decentralized EMS is analyzed in detail, followed by which the system design is elaborated. In the end, the feasibility and effectiveness of the proposed EMS are verified by experimental results.

In case of large number of distributed generation (DG) connected to grid, harmonic pollution becomes more seriously. DGs and grid-connected inverters are expected to participate in grid operation and management responsibly. Especially when the grid meets serious harmonic pollution, inverter’s grid connecting manipulation requires very high-precision phase angle detection. In these years, as a novel phase locked loop (PLL) method, second-order generalized integral (SOGI) PLL attracts more and more attentions. For inverter grid connecting manipulation purpose, in this paper, relationship between SOGI controller parameters and its dynamic performance are analyzed firstly. Then via SOGI, positive sequence components are extracted accurately and rapidly from the seriously polluted grid voltage. Using this information, inverter grid connecting controller can be designed. Through Matlab/Simulink simulation tool, above proposed method is justified and simulation results show its effectiveness when inverter connecting with grid under serious harmonic pollution.