Automated methodology for adjustment of component values in passive converter circuit for wind turbine generators

The current paper proposes an automated design approach for a previously developed passive converter circuits for wind turbine generators. This suggested approach allows to calculate the components for all passive converter circuits approved in European patent number PCT/EP2010/055637, where only minor changes in the source code of the mathematical and simulation software have to be made when different circuits are involved. An optimisation based on steepest descent method results in power/frequency (power/speed) curve that matches well the cubic dependence (Pwtmax~ω3) of the extracted power

Comparison of multiple stage braking circuits for wind driven generators

This paper presents multiple stage braking circuits for wind turbines with a permanent magnet synchronous generator. The system combines both passive converter circuit coupled to a resistive braking circuit. The second one is an over voltage protection when an emergency situation of no load is detected. The power converter control and braking are simulated and the output power/frequency graphics are derived. Three braking circuits are analyzed and compared. Design recommendations are formulated regarding the application of different topologies depending of the wind speed and the input assignment

Digital advantages for the construction industry

Currently, the digital transformation is recognized as a source of many potential effects for the business organization from all sectors of the economy. The purpose of this study is to identify and highlight the possible advantages of the application of digital technologies in the construction sector. A scientometric analysis of the existing literature is performed. The scope of the study is given from three perspectives through three search criteria - digitalization, big data, and forecasting. A total of 2371 articles are abstracted. Then, the extracted data is visualized through Vosviewer software tool. The growth of publications increases significantly over the last decade. The results illustrate that the digitalization in the construction sector affect all aspects of construction projects, with the strongest impact on the architecture design and building information modelling. Big data in construction is associated with the data storage, data analytics and information management, during the whole life of the buildings. The third search criterion shows that construction companies most often forecast the total costs using regression analysis, machine learning algorithms, artificial neural networks, etc The research findings could support decision makers and practitioners with-depth understanding for the possible advantages of digital technologies in the construction industry. The current study is part of a larger project called "Digitalization of Economy in a Big Data Environment" BG05M2OP001-1.002-0002-C02

Design considerations and loss analysis of DC chokes

The paper presents design considerations and a loss analysis of dc chokes in kW range, realized by different magnetic materials. Five designs under the same input parameters are realized with three different materials: ferrite (3F3), powder (sendust MS) and amorphous material (Microlite 245). An optimal design procedure is considered aimed at minimizing losses and volume of the component. A set of operating and construction parameters is analyzed. The obtained design results are verified by carried out simulations. Three of the compared DC chokes are realized, experimented and measured under the real operating conditions. The comparison of the three different materials is summarized and design recommendations are formulated regarding their use is such applications

Improved Battery Charger Circuit Utilizing Reduced DC-link Capacitors

The article presents a comparison of advantages and disadvantages of a battery charger circuit with and without the use of DC-link capacitors in it. The specific application requirements, namely ultra-light electric vehicles, are set as lightness, efficiency and robustness of the design. Prove of greater reliability and improvement on maintenance costs without significant decrease in the quality of charging process with the removal of DC-link capacitors in rectifier and boost converter circuits is accomplished. The proposed circuit parameters are analyzed by carried out simulations

Successive resistive braking circuit for permanent magnet wind turbine generators

An electric brake for wind turbine systems is proposed in this paper. Effective emergency electrical braking is needed if an overvoltage occurs due to grid failure. The derived circuits use high power thyristors corresponding to the high values of generated power from today's wind turbines. A practical confirmation with BLDC a generator is ongoing in the laboratory. The principle of operation is proved by the carried out simulations

Improvement on LiFePO4 Cell Balancing Algorithm

The paper presents improvement on operation time of cell balancing algorithm compared to conventional multiple cell LiFePO4 charge methodology. A flowchart is synthesised to explain the main steps of the software design, which afterwards is implemented in a microcontroller. Experimental results are provided to clarify the transition between charge and balance process. Graphical data for a voltage equalization of eight cells is presented to verify the proposed improvement

Design of passive converter for wind driven generators

The aim of the paper is to design and to do the fine tuning of a passive converter from a permanent magnet wind generator to a fixed DC link. It shapes a torque speed curve with only passive elements like diodes, inductors and capacitors. The result is a power/frequency (power/speed) characteristic close to the optimal one for wind turbines. The proposed novel circuit has the advantage to be a reliable, robust, and maintenance free and cost effective solution

Forecast the gross value added in construction sector of Bulgaria with SARIMA model

Construction is an important sector for national economies because it contributes with relatively high gross value added (GVA). The purpose of this study is to forecast GVA in a short-term period based on seasonal ARIMA models. Quarterly time series data from 2010 to 2020 are used for modelling and forecasting. Stationarity is achieved after differencing both - seasonal and non-seasonal component of the data. Based on autocorrelation plots SARIMA model is selected as most accurate. Ljung-Box test for the absence of autocorrelation confirms that the model is adequate and suitable to forecast. The current study is conducted as part of the research project BG05M2OP001-1.002-0002-C02 "Digitalization of Economy in a Big Data Environment"