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This article presents a method for analysis of the low-power periodic Wireless Power Transfer (WPT) system, using field and circuit models. A three-dimensional numerical model of multi-segment charging system, with periodic boundary conditions and current sheet approximation was solved by using the finite element method (FEM) and discussed. An equivalent circuit model of periodic WPT system was proposed, and required lumped parameters were obtained, utilizing analytical formulae. Mathematical formulations were complemented by analysis of some geometrical variants, where transmitting and receiving coils with different sizes and numbers of turns were considered. The results indicated that the proposed circuit model was able to achieve similar accuracy as the numerical model. However, the complexity of model and analysis were significantly reduced.

This article attempts to identify the key forces driving the successful digitalization of the energy sector, ensuring improvements in the energy triangle including sustainability, stability, and economic performance. The article sheds light on the diverse energy priorities at supra-, national, and managerial levels, and the role of digitalization in achieving these objectives. Catching up economies (such as Poland), being post-socialist EU member states, in order to transform its energetic sector, must overcome a number of infrastructural and social shortcomings retained as a legacy of the socialist economy. As such, sustainability (as the core priority at EU energy agenda) may not be the leading objective at both national and company level in the energy sector transformation. This article presents the results of empirical research carried out through distribution of e-questionnaire addressed to Polish managers from the energy sector. The results were analyzed using the fsQCA method. The findings suggest that, for managers, the most important drivers of digitalization and transformation of the energy sector in Poland are its high economic performance, together with support for energy prosumers and consumers. The prerequisites for a successful digitalization are alternatively the absence of management barriers, or a combination of high economic performance and a strong focus on environmental protection. Surprisingly, according to managers surveyed, the rapid implementation of new technologies is not considered a vital condition for successful digital transformation of the energy sector, which implies either or managerial lack of knowledge in this area and/or a reluctance to introduce digital rapid technologies.

Future energy markets are foreseen to integrate multiple entities located mainly at the distribution level of the grid so that consumers can participate in energy trading while acting as individual prosumers or by forming energy communities. To ensure the smooth integration of prosumers and satisfy the effective operation of the power distribution systems (PDSs), it is important to fundamentally assess their performance for different grid development scenarios. This paper aims to estimate and compare the hosting capacity (HC) thresholds and profitability for two alternatives: (a) when the PDS experiences rapid growth of scattered individual prosumers with photovoltaic (PV) installations and (b) when prosumers intend to formulate a medium-scale energy community, which is a single source located in one node. Maximization of the profits of decision-makers and maximization of the capacity of the PV generation were set as the two objectives for the optimization tasks. It has been analyzed how the physical topology of the distribution network can be harmonized with the underlying bidirectional power flows for each alternative while satisfying system constraints. A typical distribution test feeder is employed to estimate the energy loss and voltage variations in the PDS, as well as the profitability for energy producers, for various penetration levels of prosumers, in comparison to the base case with no PV generation. The results indicate that improvements in terms of profitability and reduction of energy losses can be achieved in both alternatives, as long as the penetration of PV systems does not reach a certain threshold, which can be chosen by decision-makers and is limited by the HC. Comparing the results of the simulation, EComs demonstrate higher HC vs. individual prosumers, both in terms of technical and economic priorities.

Designing a maximum power point tracking system (MPPT) can raise many questions when it comes to choosing the best converter and algorithm for the job. The number of possible solutions can be overwhelming, especially when it comes to MPPT algorithms. New algorithms are often tested in simulation environments only, where the accuracy and speed of a single measurement (i.e., in a single step) are usually assumed and sometimes unintentionally exaggerated. In practice, even if the algorithm is fast, its speed is limited by other factors. This article emphasizes the time limitations that are related to converter parameters and that naturally exist in all maximum power point tracking systems. Additionally, the article proposes a measurement method that enables voltage and current measurements with good accuracy for different transients that exist at the input and output of DC–DC converters.

This article presents the results of computer analysis of selected switching networks. In these analyses, the influence of selected parasitic components of electronic switches on the total and active power losses in these switches is considered. Analyses are performed using the SPICE software for two models of semiconductor switches: an ideal switch with RC parasitic components and the SPICE model of an IGBT. The influence of parasitic capacitances and resistances of these devices operating with the control signal of different parameters values on the total and active power dissipated in these switches is analyzed. On the basis of the obtained computations the average and peak-to-peak values of the junction temperature of electronic switches at the steady state are calculated using a compact thermal model. It is shown that parasitic elements visibly influence waveforms of the active and total power. It is proved that the simplified model using the total power in computations of the junction temperature makes it possible to obtain a high accuracy of computations only in a situation when the transistor operates with a resistive load. For an inductive load, such simplification can cause an unacceptably high computation error exceeding even 30%. Such an error is a result of big differences between the active and total powers during switching-on and switching-off processes.

DC microgrids, along with existing AC grids, are a future trend in energy distribution systems. At the same time, many related issues are still undefined and unsolved. In particular, uncertainty prevails in isolation requirements between AC grids and novel microgrids as well as in the grounding approaches. This paper presents a critical technical analysis and an overview of possible grounding approaches in DC systems and the feasibility of avoiding isolation between AC and DC grids.

This article analyzes the problem of modeling the properties of such magnetic elements as inductors, coupled inductors, and transformers using the SPICE software (version 17.2). Both the classical models of magnetic elements, built in this software, and the models implemented in the form of subcircuits are described. In particular, attention was paid to the possibility of taking into account the non-linearity of the characteristics of the considered elements and mutual couplings between electrical, magnetic, and thermal quantities. Using the results of thermographic measurements, the need to take into account the differences in temperature values between the individual windings and the core of inductors and transformers was justified. Selected models of the considered elements given in the literature are briefly characterized. The network structures of the electrothermal models of the considered elements elaborated at Gdynia Maritime University are presented. The results of calculations and measurements illustrating the correctness of the described models and their prac-tical usefulness for the elements of different structures are presented and discussed.

In Poland, special attention is focused on sustainable municipal waste management. As a result, new waste incineration plants are being planned. They are considered to be modern, ecologically friendly, and renewable energy sources. The waste from conventional incineration, which contains hazardous substances, must be disposed of in an appropriate manner. This study used advanced statistical tools, such as control charts, trend analysis, and time series analysis. The analysis was based on the leachability of selected elements and chemical compounds in incineration bottom ashes (IBAs) from the Waste to Energy Plant in Kraków, which were weathered for 2 weeks. The analysis was performed for 34 weeks. The obtained leachability results were compared with the leachability limit values of individual components. Based on the analysis of the control charts, it was found that in the case of selected samples, the leachability limit values for processing outside the plant using the R5 recovery process (LLVR5) values were exceeded. Seasonality analysis was performed using the autocorrelation function (ACF), the partial autocorrelation function (PACF), and the frequency analysis. Based on the obtained results, it was concluded that the leachability of elements and chemical compounds from waste does not confirm the occurrence of seasonality. It was found that from the exceedances of the LLVR5 mean that the two-week weathering is not sufficient and further studies should be carried out. The research methodology, which was presented on the example of the leachability of elements and compounds from IBA, can also be used for other waste analyses.