1,721,139 research outputs found
Full-Bridge LLC Converter Using Voltage-Doubler
No full textThe title of this thesis is Full-Bridge LLC Converter with Voltage-Doubler, consisting of a full-bridge series resonant converter on the primary side and voltage multiplier on the secondary side. It is to propose a full-bridge LLC converter with voltage multiplier with the nominal output power is 150 W and 150 V of DC input voltage. The LLC resonant tank serves as a second-order low-pass filter and dc-blocking stage simultaneously. It is featured with the purpose to achieve zero-voltage-switching (ZVS) to reduce switching losses of the circuit. In order to minimize the passive components in the converter, it operates at high frequency mode. But, since there might exist some range that would lack of decent efficiency, specifically if it is operating under light load. The converter will be morphed to half-bridge to gain the reduced loss. Unfortunately the voltage fed into the resonant tank will reduce into half of the input and the voltage gain cannot fulfill the output needs under this special half-bridge and light load condition. The voltage multiplier will be applied to regain the output voltage caused by the decreasing voltage in the input side. The thesis experimental results applied under heavy load and light load. Under full-bridge LLC converter resulted with the output of 36V, 2.5A and 44V, 2.5A for the heavy load, meanwhile under light load the output voltage will be 36V, 0.25A and 44V, 0.25A
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Unit commitment considering regional PM2.5 concentration
No full textPM_2.5 poses a threat to the environment and ecology and has become an important issue in recent years. Reducing coal consumption is one of the ways to improve thermal power plants. At this stage, there is no precise criterion for coal reduction (especially for estimating the impact of emission reduction on specific affected objects, such as cities). The air dispersion model can quantify the regional impact of power plant emissions based on meteorological conditions. In this paper, the air dispersion model is added to unit commitment, which becomes a Multi-Objective Programming problem that considers the economy and the pollution concentration of major regions at various times. This paper uses AQI to set relevant pollution regulations. At this time, PM_2.5 forecast and load forecast are of the same importance. This paper studies the influence of forecast values with different accuracy on the scheduling results. The penalty factor is used to convert the concentration into economic valuation and included in the objective function. This paper uses the YALMIP toolbox to construct mathematical problems in the MATLAB and solves through the Gurobi optimizer. The IEEE 39-bus is used as the power grid model. Finally, the simulation results confirmed that with the help of the dispersion model, a more detailed unit commitment can be provided with consideration of regional PM_2.5 concentration can be provided. As the penalty factor changes, different costs and pollution concentration results in each region are produced. This relationship will be drawn into a trade-off curve to provide a preliminary basis
A Dynamically Smoothing State of Charge Estimation on Electric Vehicle Batteries
No full textWith the successful development of electric vehicle industries, the advanced utilization and the management of onboard batteries has become indispensable. As a result, the requirements on Battery Management Systems (BMS) become more and more stringent. To achieve demanding goals for energy efficiency and battery life, the BMS needs to function effectively with accurate real-time system information. Battery state-of-charge (SOC) is one of the most important system parameters, and therefore SOC online estimation is of parameters paramount importance to operations of BMS and the entire EV. In this thesis, we propose a battery SOC estimation method for EV operations. The proposed method uses neural network to obtain a preliminary estimation. After that, a corrected version of SOC is obtained by passing the preliminary estimate through a smoothing FIR filter. The neural model used was long short-term memory (LSTM) model as a member of recurrent neural network family. On the other hand, the proposed filter is a self-defining FIR filter, whose coefficients are trained using genetic algorithm. By doing this, we have the ability to achieve a SOC mean error exist within 1% and a SOC max error up to 5.17% before passing through the filter. And max error decrease to 2.44% after passing through the filter. The dynamic test data used in this paper was according to the light vehicles testing standards releasing by DiselNet
Control of MMC for Partial Shading of Photovoltaic Generation System
No full textThe modular multilevel converters have high expansion, and as the more the number of modules, the smaller the AC current harmonics. In recent years, many scholars have also carried out research in this direction, and used this topology to combine with solar power generation. In order to make the solar panels not affected by shading, they can be independently controlled, and the system can stably output balanced three-phase current to the grid. Therefore, this thesis uses a modular multilevel converter topology to connect the solar panel to the module in parallel. Power distribution between modules by changing the voltage command. Use the DC and AC components of the circulating current to transfer the power between the phases and the arms, so that the modules can output their maximum power. And the system can output balanced three-phase current to the grid stabilit
Non-Differential Chopper Based Bipolar Buck-Boost AC-AC Converter
No full textAn H-bridge structured non-differential ac choppers based bipolar ac-ac converter has been proposed recently, and it has identical non-inverting/inverting output voltage. However, the existing topology only provides buck operation and the input current is not continuous. Therefore, in this thesis, a new bipolar PWM buck-boost ac-ac converter is proposed based on the extension of the bipolar buck type ac-ac converter, which not only provides the identical-inverting/inverting buck-boost operation but also ensures the continuous input current, which improves the quality of the input current and doesn\ue2t require an additional input LC filter. In addition, in this new design, the structure of the circuit consists of two sets of non-differential converters, and each set of them has two inductors and a DC snubber. This structure improves the open-circuit issue of the inductor currents caused by the complementary relationship of the AC switches and does not need to add additional control strategies to maintain the current path, which enhances the reliability of the circuit. In this thesis, the operation of two control modes (single and two duty ratios) is firstly analyzed, discuss the parameters design of the circuit and verify the theory through experiments. The proposed prototype is operated at the rated power of 400W, the output voltage demand is 155Vpeak, and the single-phase power supply is used to simulate the disturbances of the grid voltage, with the variation range of 100Vpeak ~ 200Vpeak. In order to observe the efficiency of the circuit as well as the variation of the total harmonic distortion of the output current, the input voltage is increased from 100Vpeak, with each increase of 10Vpeak. The circuit's highest efficiency is 80.5%, and the lowest is 77.5%
Design of a Wireless Power and Data Transmission System for Audio Devices
No full textA circuit for simultaneously transferring power and an audio signal by magnetic resonant coupling is proposed. The transmitter contains a self-oscillation circuit and therefore is able to auto-tune the oscillation frequency close to the system resonant frequency which is 1 MHz in this thesis. A phase shifting circuit is utilized to slightly vary the oscillation frequency according to an audio input signal, thereby modulating the amplitude of the driving current through the transmitter coil. The receiver is able to convert the induced high-frequency voltage into DC power and also demodulate the audio signal back from the high-frequency carrier. A class-D power amplifier, supplied with the DC power and fed with the audio signal, is then used to drive a speaker for demonstration
Renewable hosting capacity improvement with grid reinforcement optimization
No full textThe integration of renewable energy sources (RES) into power grids plays a crucial role in the transition towards sustainable power systems. However, the intermittent and unpredictable nature of RES introduces challenges that require a careful and effective strategy to enhance the hosting capacity for renewable energy while maintaining optimal power flows within the grid. This thesis proposes an innovative methodology that combines Particle Swarm Optimization (PSO) and Second-Order Cone Programming (SOCP) for the Distflow equation, aiming to maximize the Renewable Energy Hosting Capacity (REHC) without compromising operational limits.
Our approach leverages a PSO-based technique to optimize grid reinforcement parameters, including line current, resistance, and reactance. The optimization process considers the resistance, reactance, and rating of each line, with the objective of increasing the hosting capacity of renewable energy while minimizing investment costs.
To evaluate the effectiveness of the proposed methodology, we plan to implement and test it on a radial 33-bus distribution system. Our results demonstrate that the method effectively enhances the hosting capacity for RES while adhering to the given budget for grid reinforcement. This approach shows promise in assisting power system planners and operators in making strategic decisions related to grid reinforcement and the integration of renewable energy
SEPIC Converter Design with Power Regulation and Load Compensation
No full textA SEPIC converter is designed in combination with an inverter to form a driving circuit of an ultrasonic transducer for the spray coating application. The SEPIC converter provides an adjustable DC output to an H-bridge inverter. By adjusting the DC output level, the output power of the inverter is thereby regulated. Considering the requirement of steady driving power and the possible changes in the transducer impedance, additional driving power feedback control and feedforward load compensation are included in the control scheme of the SEPIC converter, so that the resulting ultrasonic driver can maintain a constant driving power even under load variations. The experimental results confirm that the designed SEPIC converter not only has a high power factor, but also help regulate the driving power under a sudden change in load impedance
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