Communication-based distributed secondary control is deemed necessary to restore the state of islanding AC microgrids to set points. As its limited global information, the microgrids become vulnerable to cyber-attacks, which by falsifying the communicating singles, like the angular frequency, can disturb the power dispatch in the microgrids or even induce blackout by pushing the microgrids beyond the safe operation area and triggering the protection. To make the microgrids more cyber secure, adaptive resilient control for the secondary frequency regulation is proposed. It assumes that each converter is communicating with its adjacent converters. With the proposed control, the weight of the communication channel being attacked is automatically reduced, and the more the communicating signals are falsified, the further the weight of that communication channel is weakened. The proposed approach does not rely on attack detection and thereby is easy to implement; Besides, it still works when challenged by a combination of multi-attack signals; Moreover, it applies to multiple communication lines getting attacked cases. Finally, the effectiveness and feasibility of the proposed resilient control scheme are validated by both simulations and experimental results.

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The report examines the role of Standalone Microgrids (SMs) in electrification and emissions reduction, focusing on the comparison of HOMER Pro and iHOGA PRO+ software. It assesses these tools using 22 criteria and three case studies, highlighting differences in optimization results and the importance of selecting software based on specific requirements. Despite minor discrepancies in sizing, the comparison underscores each software’s strengths and weaknesses in designing efficient and cost-effective SMs. The main authors have identified the following 3 Key Takeaways from the report: HOMER PRO and iHOGA PRO+ are publicly available software tools for the microgrid optimization process during the microgrid pre-design phase. Task 18 has defined 22 criteria (quantitative and qualitative) to help software users evaluate which software tool fits better their needs. Based on the quantitative criteria, Task 18 has found that the simulation results from both software tools are equivalent, both when simulating an existing microgrid with real measurement data and when simulating a new microgrid from scratch. However, based on the qualitative criteria, both software tools have some uniqueness in terms of their features.@en

In low-voltage distribution networks, the high penetration of renewable energy generators in residential buildings has proven challenging for system operators. In response, the grid operators can reinforce the grid infrastructure or deploy battery energy storage systems throughout the network to compensate for the voltage fluctuations. Alternatively, new energy markets for ancillary services have been proposed to involve the prosumers; however, most are at medium and high voltage levels. This paper investigates, from a cost perspective, what conditions can make it attractive for individual prosumers to participate in a low-voltage ancillary service market, specifically power curtailment and peak shaving. We considered a prosumer with a 2 kWp PV system for both ancillary services, adding a 10 kWh battery for the peak shaving case. Curtailing power to comply with the maximum power exchange with the grid does not create any significant change in the LCoE of the PV system, keeping it near 0.072 €/kWh for permitted return grid powers above 1.25 kW. Scenarios closer to zero-injection increase exponentially the LCoE to 0.222 €/kWh. Using a semi-empirical ageing model, we estimated the degradation of the batteries for the cases with and without providing peak shaving, concluding that doing peak-shaving to avoid demanding more than 1 kW from the grid extends the battery life by up to 320 % while increasing its LCoS only 9.5 % when compared to a zero-consumption scenario due to the reduced depth-of-discharge and number of cycles. The results suggest that power curtailment and peak shaving can be attractive for prosumers, thus creating opportunities for ancillary services business models at the residential scale.@en

This article presents an analysis, multiobjective design, and benchmark of three modified 3 phase shift full-bridge (PSFB) converters that are well-suited for electric vehicle (EV) battery charging applications, covering both typical battery voltage classes (400 and 800 V). These three modified PSFB converters, denoted as the t-PSFB, r-PSFB, and i-PSFB converters, have the ability to reconfigure and provide better efficiency performance in the wide voltage range necessary for public EV battery charging applications. In this article, the characteristics and design considerations of these reconfigurable PSFB converters are discussed in detail. A multiobjective converter design process is proposed to optimize the average efficiency, normalized cost, and power density of the magnetic components and heat sinks. This design process employs the correlations between the cost and performance indexes of the key components derived based on open and accessible components' data to estimate the design objectives. In this way, the design process is not constrained by certain component choices, making it easier to identify the most advantageous design. A benchmark study is conducted among the reconfigurable PSFB topologies and the conventional PSFB circuit using the proposed multiobjective design process. To validate the analysis, a close-to-Pareto-front 11-kW, 45-kHz r-PSFB converter prototype with 640-840-V input voltage and 250-1000-V output voltage ranges is developed and tested.

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Accurately predicting the battery's aging trajectory is required to ensure the safe and reliable operation of electric vehicles (EVs) and is also the fundamental technique toward residual value assessment. As a critical enabler for mainstreaming EVs, fast charging has presented formidable challenges to health prognosis technology. This study systematically compares the performance of features extracted from the multistep charging process in the state of health (SOH) assessment. First, 12 direct features are extracted from the voltage curve, and the degradation mechanisms strongly correlated to these features are analyzed in detail. Integrating the degradation mechanism and correlation analysis, a data feature construction strategy is designed to categorize extracted features into groups. Then, the performance of different features extracted from the fast charging process in the SOH assessment is compared regarding estimation accuracy. Finally, the generalization and feasibility of the optimal data feature are verified with different fast charging protocols and training data sizes. The verification results indicate that the data feature representing fused degradation modes has excellent generalization and feasibility in SOH estimation, and the mean absolute error (MAE) and root-mean-squared error (RMSE) for various cells under different decline patterns are within 0.90% and 1.10% , respectively.

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Power control of flexible loads will play a significant role in energy transition. This work has developed a mixed-integer linear power control (MILP) model that manages electric vehicle (EV) chargers, heat pumps (HPs), and PV rooftops. The power control was tested with and without vehicle-to-grid (V2G) capabilities in different grid types, namely residential, commercial, and mixed grids. Moreover, the effect of different seasons and charger efficiencies was investigated. It was shown that grid characteristics such as EV parking times and building occupations can affect significantly the power control, e.g. the amount of imported and V2G power. Moreover, while V2G power is rarely used due to current V2G round-trip efficiency, future efficiency improvement can lead to a significant increase in V2G use. Finally, the seasonal effect had also a significant impact with Summer being characterized by higher exported and lower imported energy due to the high and prolonged PV power availability.

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This paper concerns the control problem of the active caused by the mismatched impedance in resistive feeders-dominated microgrids. A distributed model predictive control (DMPC) scheme is suggested to regulate the virtual impedance of each involved unit. Moreover, the proposed method benefits resilience to communication failure by designing the communication matrix. Furthermore, it involves propagating information among units in a short period, significantly reducing the communication and computation burden. Finally, the performance of the proposed control scheme is evaluated in terms of its convergence, robustness to communication delay and load variations, resilience to communication failure, and plug-and-play functionality without communication in an inverter-connected system.

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The urge to reduce the dependence on natural gas for heating at the residential level has led to the deployment of different fossil fuel-free alternatives. In the Netherlands, two technologies are leading the transition: heat pumps, due to their high COP, and photovoltaic–thermal systems, due to their dual electric-thermal output. However, both represent a challenge for users and grid operators, aside from their stochastic behavior. Heat pumps alone can surpass a typical Dutch house's total energy and power consumption. Photovoltaic–thermal systems, as their only electric homologs, usually have a mismatch between generation and demand, causing energy injections to the grid. From the electric perspective, storage systems are a proven solution to reduce the energy exchange with the distribution network. This paper proposes four multi-carrier energy system configurations for a Dutch household, comprising different combinations of a photovoltaic–thermal system, a battery energy storage, a heat pump, and an underground water tank thermal energy system, providing analytical models for every component (including the thermal losses from the thermal storage to the ground), and the space heating and electrical demands. We determined the components’ compatibility and evaluated the combinations considering their thermal performance, electrical performance, and equivalent CO₂ emissions. The results suggest that using a heat pump combined with a photovoltaic system and a battery provides the best trade-off. The photovoltaic–thermal system alone could not supply the thermal demand required for comfortable space heating nor reach temperatures high enough to charge the thermal storage. Combining the thermal storage with the heat pump allows a certain degree of flexibility for the heat pump activation at the cost of COPs between 0.8 and 1.38 when used to charge the thermal storage, thus increasing energy consumption and equivalent emissions considerably.

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In the production of green hydrogen, electrolyzers draw power from renewable energy sources. In this paper, the design of Solid State Transformer (SST) for large-scale H ₂ electrolyzers is benchmarked. The three most promising topologies are chosen for design and comparison, including Modular Multi-level Converter (MMC) based SST, Modular Multi-level Resonant (MMR) based SST, and Input-Series-Output-Parallel (ISOP) based SST. The distance between converter towers for insulation and maintenance, the insulation system of the transformer, and the cooling system are designed with practical considerations in order to have an accurate estimation of the volume and weight of the SST. Losses in the switches are calculated based on equations, and losses in passive components are calculated based on FEM simulation. The operating frequency for each topology is optimized to minimize loss, weight, and volume. The best of each topology is then compared with each other to identify the most suitable one for large-scale H ₂ electrolyzers.

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The development of lithium-ion batteries has experienced massive progress in recent years. Battery aging models are employed in advanced battery management systems to optimize the use of the battery and prolong its lifetime. However, Li-ion battery cells often experience fluctuations in battery capacity and performance during cycling, which makes capacity prediction more difficult. Moreover, the reason for the capacity regeneration phenomenon occurring after resting periods is not clear yet, as well as the influence of cycling conditions on capacity regeneration. A relationship between this phenomenon to cycling state of charge (SoC) ranges and current rates was investigated in this paper on a battery cell with Lithium Nickel Manganese Cobalt Oxide positive electrode. Experimental results show that the capacity increase is a consequence of decreased internal impedance after the resting period. The experiments also showed that a significant power drop and subsequent power regeneration after a resting period occurs only for specific SoC ranges, and applying a resting period after battery cycling can mitigate this power fading process. The semi-empirical model of battery degradation including capacity regeneration is proposed in this paper based on physical processes inside of the cell retaining low computational requirements. The acquired results can be utilized in battery management systems for more accurate state of health estimation and to prolong battery lifetime.

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This article discusses the various operating modes of a series resonant balancing converter for bipolar dc grids. It is shown that the converter can be operated in both the capacitive and inductive regions with respect to the resonant frequency of the LC tank. Furthermore, concerning the pulse width modulation signals to the switches, the converter can either be operated by controlling the phase shift between the converter half bridge legs or the duty cycle of the half bridges. A qualitative comparison of the different modes proves that a) the phase shift modes have better soft switching capabilities, b) the capacitive phase shift mode can show zero voltage switching at switch turn-on in the whole operating range, c) the losses in case of capacitive phase shift mode shows best performance at low load power, d) the inductive region power modes show lower rms current for the same power flow compared with capacitive region modes which lead to lower losses at higher output power. The simulation and experimental results depict the operation of all the modes. Finally, a prototype is designed to validate all operating modes, demonstrating $>$99% system efficiency at 1.75 kW.@en

This article presents an optimal multivariable control (OMC) strategy for the LCC-LCC compensated wireless power transfer systems. To mitigate reactive power and achieve higher efficiency, the proposed OMC method incorporates dual-side hybrid modulation and primary-side switch-controlled-capacitor (SCC) tuning into the triple-phase-shift (TPS) control. First, the impact of hybrid modulation and SCC tuning on the system characteristics is investigated. The inverter and rectifier zero-voltage-switching (ZVS) conditions are then analyzed to achieve dual-side ZVS with minimal reactive power. Furthermore, a multivariable optimization problem is established based on the power loss analysis. The solution to this problem provides optimal control variables that minimize the overall system loss. Through collaborative modulation and control of the inverter, rectifier, and SCC, the proposed method reduces the rms values of the currents and lowers the turn-off currents for the converters. As a result, this approach improves efficiency in both light- and heavy-load conditions, enabling wide output regulation and full-range efficiency optimization simultaneously. Finally, the proposed method is benchmarked with the existing TPS method. Experimental results demonstrate that the proposed method achieves higher dc-to-dc efficiency in the power range of 0.2-2.2 kW, with a maximum efficiency improvement of up to 6.3%.

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This article presents a detailed procedure for deriving the generalized average model (GAM) of a dual active bridge converter. The proposed model incorporates higher orders of harmonic components to increase accuracy. Moreover, the turn ratio of the high-frequency transformer (N_t) is considered for realistic modeling, which removes the conventional assumption of unity turn ratio. A detailed model of the DAB will ensure an accurate control design. Required mathematical expressions are derived and explained thoroughly, with an example showcasing a GAM model of the DAB converter up to the ninth harmonics. Several GAM models using different harmonic orders (first, third, fifth, seventh, and ninth harmonics) are derived and compared to the PLECS simulation model and a real-time simulation of the DAB converter on the PLECS RT-Box-2. Results show that including up to the ninth harmonics in the proposed model of the DAB converter leads to achieving accurate voltage and current amplitudes that are almost identical to the simulation outputs and even better than the experimental results.

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This article proposes a new configuration of a modular multilevel converter (MMC) and a Marx generator to generate fast-rising impulse waveforms. This new configuration improves the capabilities of the MMC-based high voltage arbitrary wave shape generator to generate fast-rising impulse since the MMC topology faces many inherent limitations. Similar to the conventional superimposed circuit of the ac transformer or dc rectifier circuit with the Marx generator, three hybrid circuits of MMC and the Marx generator are introduced, where the most optimal choice is made considering the practical aspects of testing, such as the size, cost, and preparation time. Then, a detailed analytical study is performed on the Marx generator circuit and the MMC circuit, and both circuits are coupled together to deliver a complete guideline on choosing various system parameters when the impulse wave shape and the load capacitor are given. The concept of this new hybrid configuration is demonstrated with a scaled-down prototype where the impulse with a rise time of 1 μs is superimposed on different arbitrary wave shapes. Similarly, the MATLAB-Simulink simulation model validates the proposed configuration for a 200, k V dc link voltage and 67 submodules with the desired impulse performance.

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This article proposes an analytic approach to design the typical power factor correction (PFC) control of an electric vehicle (EV) charger to ensure small signal stability in weak grid conditions. Compared to the previous works, the proposed method considers the dynamics of all the control loops, i.e., phase-locked loop (PLL), voltage loop (VL), and current loop (CL). The impacts of key influential parameters on stability are analyzed. Furthermore, the upper limits of the PLL and VL bandwidth to ensure small signal stability are derived. Accordingly, the influences of the CL bandwidth, short circuit ratio (SCR), and the filter inductance on the upper limit of the PLL bandwidth and the VL bandwidth are quantified. Consequently, a design procedure that eliminates the need to model the input impedance for tuning the controller to prevent small signal instability is proposed. Simulations and experiments validate the analysis.@en

Resonant converters are popular in power electronics due to their soft-switching capabilities, which enhance efficiency and prolong component lifetime. Three- phase resonant converters are particularly noteworthy for their higher power density and reduced ripple, making them ideal for demanding applications. A critical aspect of optimizing three-phase LLC resonant converters is the design of a transformer with adequate leakage inductance required for the resonance circuit. This paper compares two distinct transformer designs for such converters: a five-limb shell-type transformer and a symmetrical triangular transformer. Both designs are evaluated in terms of their performance, efficiency, and suitability for integration into the converter architecture. A detailed design procedure using Finite Element Method (FEM) analysis is presented to guide the development of these transformers. The practicality of this approach and its effectiveness are demonstrated through the implementation of a 3.4 kV to 60 V, 50 kVA prototype. This work provides a comparative analysis of transformer designs and introduces a validated methodology for improving the performance of three-phase LLC resonant converters through optimized transformer design.

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This paper studies the power density limits of propulsion motor for electric aircraft considering thermal aspects and breakdown voltage reduction of insulation. The study em-ploys multi-objective optimization (MOO) to explore various mo-tor cooling options and filter configurations. The results show that motors with direct winding heat exchanger (DWHE) can reach higher specific power, while those equipped with water jacket cooling (WJC) offer a moderate design with simpler structure. Furthermore, the impact of sine wave and dv/dt filters on electric motors design is studied. The findings demonstrate that dv/dt filters enable designs with higher overall specific power compared to sine wave filters. Through simulations, this study identify the challenge faced by aviation motor design in significantly increased insulation thickness, necessitating advanced insulation materials with a minimum thermal conductivity of 5 W/(m.K) to facilitate a high specific power design. Based on this assumption, a preliminary design of 9.6 kW/kg with an efficiency of 98% is presented.

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This paper presents a control strategy for active power decoupling in a Solid State Transformer (SST) using a cascaded H-bridge (CHB) converter, dual active bridge (DAB) converters, and a high-frequency link (HFL). The strategy balances capacitor voltage and decouples power flow, significantly reducing second harmonic voltage ripple in DC link capacitors and potentially reducing their size.

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Converters that produce an isolated dc output from a three-phase mains supply are often required. Moreover, input power factor correction (PFC) functionality is essential. A standard two-stage conception with ac/dc and dc/dc converters may be used. However, a single-stage or quasi-single-stage solution can simplify the circuitry and increase efficiency; therefore, many variants of single-stage converters have been researched and published. This paper introduces a novel quasi-single-stage resonant topology with an integrated transformer. Additionally, an original control structure is proposed. This converter enables full control over the output dc voltage and current. Another benefit of the proposed converter is a relatively low complexity of its power circuit and control compared to other single-stage converters. The operation principle of the power circuit is explained and the control strategy is also analyzed in detail. A description of the integrated transformer together with aspects of the resonant circuit design are presented. A simulation of the entire converter was performed and evaluated. Furthermore, a test-bench prototype was designed and constructed and is outlined in this paper. The test-bench measurement results are provided and compared to the simulation results. Power factor and efficiency measurements in terms of their dependence on the output voltage and current are included.

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The rising demand for electric vehicles (EVs) in the face of limited grid capacity encourages the development and implementation of smart charging (SC) algorithms. Experimental validation plays a pivotal role in advancing this field. This article formulates a hierarchical mixed integer programming EV SC algorithm designed for low voltage (LV) distribution grid applications. A flexible receding horizon scheme is introduced in response to system uncertainties. It also considers the practical constraints in protocols, such as IEC/ISO 15118 and IEC 61851-1. The proposed algorithm is verified and assessed in a power hardware-in-the-loop testbed that incorporates models of real LV distribution grids. Furthermore, the algorithm's capabilities are examined through eight scenarios, out of which four focus on the uncertainties of the input data and two address the engagement of extra grid capacity restrictions. The results demonstrate that the SC algorithm adequately lowers the EV charging cost while fulfilling the charging demand, and substantially reduces the peak power as well as the overloading duration, even when faced with input data uncertainty. The additional grid restrictions in place are proven to improve peak demand reduction and overloading mitigation further. Finally, the limitations and potentials of the developed algorithm are scrutinized.

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