Weighted Bandwidth Method for Stability Assessment of Complex DC Power Systems on Ships

In shipboard DC grids, tightly controlled load converters can impair the system stability, thus provoking the ship blackout. Conversely, load converters regulated by low control bandwidths are capable of inducing a stabilizing action. This compensation is verifiable if the loads are few. On the contrary, the balancing of control dynamics is hardly evaluated if the bus feeds multiple (i.e., hundreds or more) DC controlled loads. In this paper, the weighted bandwidth method (WBM) is presented to assess the small-signal stability of a complex shipboard power system by aggregating the multiple converters into two sets of controlled loads. Once the validity of the aggregation is proven, a stability study is performed on the two-loads system. As the last system is more inclined to instability than the initial multiple-loads system, the verification of the two-loads stability criterion guarantees that the shipboard DC grid also remains stable. Finally, emulations on HIL verify the proposed stability assessment thus providing the first unique verification of WBM.

Tribological and Rheological Investigations of MWCNT/PMMA Polymeric Composites and Hybrid Compounds

The Nano scale self-lubricating compounds were prepared by in-situ free radical polymerization with the dispersion of MWCNT ultrasonic molecules embedded in the polymer matrix to enhance the tribological mechanical properties as well as the production of hybrid compounds to detect the tibial changes on the polymer surface, dry friction under the conditions of slip was studied, the friction coefficient was found For hybrid compounds slightly lower than the coefficient of friction of Nano composites under multiple loads and constant velocities, enhancements of Nano composites in rheological behavior were investigated and the influencing factors were determined: shear stress, shear viscosity, as well as shear rates. By using visual inspection, tracking of the behavior of compounds during extrusion was carried out and obtaining the shapes of the threads resulting from extrusion, which are usually important matters whose results depend on many industries.

Short-Term Multiple Load Forecasting Model of Regional Integrated Energy System Based on QWGRU-MTL

In order to improve the accuracy of the multiple load forecasting of a regional integrated energy system, a short-term multiple load forecasting model based on the quantum weighted GRU and multi-task learning framework is proposed in this paper. Firstly, correlation analysis is carried out using a maximum information coefficient to select the input of the model. Then, a multi-task learning architecture is constructed based on the quantum weighted GRU neural network, and the coupling information among multiple loads is learned through the sharing layer in order to improve the prediction accuracy of multiple loads. Finally, the PSO algorithm is used to optimize the parameters of the quantum weighted GRU. The simulation data of a regional integrated energy system in northern China are used to predict the power and cooling loads on summer weekdays and rest days, and the results show that, compared with the LSTM, GRU and single task learning QWGRU models, the proposed model is more effective in the multiple load forecasting of a regional integrated energy system.

Single Source Multi-Frequency AC-AC Converter for Induction Cooking Applications

In recent years, induction heating (IH) applications aided by electronic power control have gained significance. Particularly, for cooking applications, an appropriate control technique is required to feed power from a single source to multiple loads with minimum switching losses. Additionally, when multiple loads are used, it requires independent control and operation for each of the loads. The main idea of this work is to develop a single-stage AC-AC converter topology to feed power to multiple loads independently with a single source, with a reduced number of switching devices and with minimum switching losses. The proposed topology uses a frequency bifurcation concept to feed power to multiple loads by placing the transmitting coil and work coil at a distance of 3 cm. The source is resonated at a 25 kHz switching frequency, with the designed bifurcated frequencies of 20 kHz and 33 kHz. The resonant capacitors are appropriately chosen to operate at those frequencies. For real-time applications, simultaneous and independent power control are inevitable in multi load-fed IH applications. This is achieved through a pulse density modulation scheme with minimum switching losses. The simulation of the proposed system is performed in MATLAB/Simulink, and also the 1 kW system is validated using a PIC16F877A microcontroller. The real-time thermal variation in the load is also recorded using a FLIR thermal imager. The experimental and simulation results are observed, and the obtained efficiency of the system is plotted for various duty cycles of pulse density modulation control.

Tas-de-charge – An Essential Part of Gothic Vault

Gothic architecture can be viewed from several perspectives, including stylistic aspects, architectural theory, and structural analysis.As Gothic architecture is a skeletal construction, it is essential to achieve an equilibrium with the multiple loads and forces. Medieval master masons' architectural knowledge was firmly based on empirical learning, which stimulated the dynamic development of structural innovations.This paper emphasises and describes a particular type of vault springer, one of the most complicated and sensitive parts of Gothic construction. Known as tas-de-charge, it became especially characteristic of high Gothic architecture. According to its principle, the springer's lower courses contain the merged vault nerves and are carved from one single stone block in each course. The beds of these courses are not radial as those of the average voussoirs, but horizontal. Without the concept of tas-de-charge, the development of late Gothic vaults could not be imaginable. This particular solution made possible the creation of elegantly narrow imposts supporting the vault ribs, the double arch and the formerets. So far, tas-de-charge has not been a focus of interest in the historiography of Hungarian medieval architecture; however, it appears that it was commonly applied in our late Romanesque and early Gothic monuments.

Multiple-Load Forecasting for Integrated Energy System Based on Copula-DBiLSTM

With the tight coupling of multi-energy systems, accurate multiple-load forecasting will be the primary premise for the optimal operation of integrated energy systems. Therefore, this paper proposes a Copula correlation analysis combined with deep bidirectional long and short-term memory neural network forecasting model. First, Copula correlation analysis is used to conduct correlation analysis on multiple loads and various influencing factors. The influencing factors that have a great correlation with multiple loads were screened out as the input feature set of the model to eliminate the influence of interfering factors. Then, a deep bidirectional long and short-term memory neural network was constructed. Combined with the input feature set screened by the Copula correlation analysis method, the useful information contained in the historical data was more comprehensively learned from the forward and backward directions for training and forecasting. Through the actual calculation example analysis and comparison with other models, the forecasting accuracy of the method presented in this paper was improved to a certain extent.

Dynamic Process Analysis and Voltage Stabilization Control of Multi-Load Wireless Power Supply System

At present, wireless power supply technology has gradually attracted people’s attention due to its safety, convenience, and portability. It has become one of the development trends of power supply for future technologies such as electric vehicles. In many engineering applications, inductive wireless power supply systems need to supply power to multiple loads at the same time. Therefore, it is necessary to analyze the dynamic process of the multiload system. This paper first selects the optimal compensation network according to the stable operating conditions of the multiload system. Secondly, in order to classify and describe the movement state of the load in the dynamic process, the simulation model is established on the MATLAB/SIMULINK platform to analyze the influence of the mutual inductance or resistance of any load on the output characteristics of the primary system and other loads. Then, in order to solve the problem of unstable output voltage used by multiple loads entering the same track at the same time or load resistance changes, this paper adopts a secondary side control strategy. The duty cycle of the Buck circuit is adjusted by the fixed frequency PWM sliding mode controller (PWMSMC), so as to realize the independent control of each load. Finally, an experimental platform was established to verify the correctness of the theoretical analysis.

Analysis method of manufacturing process of the multi-directional internal screws of the pipe hull parts and tool selection for implementation

Рассматривается возможность интенсификации процесса изготовления разнонаправленных внутренних винтовых пазов трубных корпусных деталей, используемых в судовых энергоустановках и пусковых устройствах для запуска подводных и летательных беспилотных аппаратов, и их элементов, испытывающих многократные нагрузки в период эксплуатации. Для выбора наиболее рационального и эффективного способа изготовления применен функционально-структурный анализ используемого оборудования для изготовления внутренних винтовых пазов трубных корпусных деталей, с помощью которого найдены закономерности процесса. Выявленный способ обработки, оборудования и применяемый инструмент являются наименее затратными и наиболее эффективными для выполнения необходимых технических требований. При проведении анализа зон локальных деформаций выявлен ряд зависимых величин, влияющих на конечное усилие и степень деформации при изготовлении разнонаправленных внутреннихвинтовых пазов трубных корпусныхдеталей. The following analysis deal with the possibility of intensification for the manufacturing process of the multi-directional internal screws of the pipe hull parts, used in the ship power plants and launch devices to launch submarine and unmanned aerial vehicles as well as their elements ,which experience multiple loads during their period of operation. Functional-structural analysis of the equipment, used for the manufacturing of the internal screws of the pipe hull parts, has been applied in deciding the most rational and efficient way of production. This analysis helps to find process patterns. The revealed way of machining, used equipment and the applied instrument provide the least expensive and the most effective results to execute necessary technical requirements. During executing local deformation areas analysis, there have been revealed a number of dependent values which make an impact on the final force as well as the deformation degree when manufacturing multi-directional internal screws of the pipe hull parts.