Technological advances in the field of power electronics have made direct current (DC) more viable, paving the way for the so-called DC microgrids. In microgrids, it is quite common to provide the power electronic con...
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Inherently, power grids with multiple inverters have interactions that may lead to resonant phenomena, which is undesirable. Thus, this paper exploits the interaction between grid-following converters and the power gr...
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Technological advances in the field of power electronics have made direct current (DC) more viable, paving the way for the so-called DC microgrids. In microgrids, it is quite common to provide the power electronic con...
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ISBN:
(数字)9798350379419
ISBN:
(纸本)9798350379426
Technological advances in the field of power electronics have made direct current (DC) more viable, paving the way for the so-called DC microgrids. In microgrids, it is quite common to provide the power electronic converters with some kind of droop control to properly and automatically share the required load. With DC-DC converters, the simplest way to do that is using the concept of virtual resistance, but it does not provide any inertial response necessary to improve the voltage quality and guarantee the microgrid’s stability. Alternatively, there is the concept of a virtual DC machine, which allows the load share and the desired inertial response. In this context, this paper adapts this idea in such a way that the control loops are cascaded and the similarities with the DC machine are clearer. The innermost loop controls the converter’s output voltage, considering two possibilities for this part: one open-loop-based and another closed-loop-based. The cascaded outer loops implement the electromagnetic and electromechanical dynamics of the DC machine and the effect of the governor. A detailed methodology is provided for setting the machine parameters according to the desired dynamics. Simulations are carried out to compare the proposed virtual DC machine with a regular virtual-resistance-based droop approach. The results show smother dynamics for the proposed control, while maintaining the proper load share.
Inherently, power grids with multiple inverters have interactions that may lead to resonant phenomena, which is undesirable. Thus, this paper exploits the interaction between grid-following converters and the power gr...
Inherently, power grids with multiple inverters have interactions that may lead to resonant phenomena, which is undesirable. Thus, this paper exploits the interaction between grid-following converters and the power grid. Generally, the idea is to use the representation of the electrical grid populated by converters to determine the resonant modes using a frequency- domain impedance-modeling approach and eigenvalue analysis. This knowledge will enable planners to predict the oscillatory phenomena caused by inverters and prevent them by proposing modifications to the control systems of the inverters. The paper presents a step-by-step discussion of how to organize the impedance models into a multibus power grid and how to conduct eigenvalue analysis in this aggregated model. For testing the models, it was considered a 10-bus grid in different scenarios, one stable and another unstable. Simulations were also carried out to validate the results of the analysis.
This work compares three types of control-loop implementation for single-phase grid-forming inverters. The first two follow a single-loop approach using proportional resonant (PR) controllers in the Natural Reference ...
This work compares three types of control-loop implementation for single-phase grid-forming inverters. The first two follow a single-loop approach using proportional resonant (PR) controllers in the Natural Reference Frame and proportional integral controllers in the synchronous reference (SRF-PI). The third control loop is also based on an SRF-PI controller. However, it has two loops, where the innermost one is related to the current that passes through the filter capacitor, and the outermost one is related to the inverter voltage. The article employs a simulation methodology to analyze the dynamic behavior of the control loops. In the established environments, it was shown that systems in SRF present a better transient response to step changes in the reference value. Furthermore, all three systems achieve zero error at steady state conditions.
This paper addresses the problem of longitudinal platooning control of homogeneous vehicles subject to external disturbances, such as wind gusts, road slopes, and parametric uncertainties. Our control objective is to ...
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This work presents an analysis of the grid-forming Modular Multilevel Converter (MMC), in the frequency domain, when it is controlled through single or dual-loop implementation. The dual-loop approach presents an inne...
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This study investigates the effect of Sr doping on the physical and photocatalytic properties of ZnO nanorods/CuO nanocomposites. Various techniques were applied to understand how Sr doping modifies these films. SEM a...
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This work presents an analysis of the grid-forming Modular Multilevel Converter (MMC), in the frequency domain, when it is controlled through single or dual-loop implementation. The dual-loop approach presents an inne...
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ISBN:
(纸本)9781665421300
This work presents an analysis of the grid-forming Modular Multilevel Converter (MMC), in the frequency domain, when it is controlled through single or dual-loop implementation. The dual-loop approach presents an inner current-loop control gathered with the external voltage-loop control, whereas the single-loop only presents a voltage-loop control for the grid-forming capability. In both cases, the control algorithms were implanted in a natural reference frame, including resonant controllers. The paper follows an impedance-modeling approach for introducing the analytical representation of the MMC in the frequency domain. These representations are, in fact, the linearized Teéenin-equivalent models of the single- and dual-loop grid-forming MMC. The results showed that the inner current-loop control is a feasible approach for damping specific resonant peaks of the Thevenin-equivalent impedance. In other words, the current-control loop adds a resistive parcel in MMC impedance in the frequency range in which the resonant peaks appear. As a consequence, the LC resonance between this impedance and the capacitor bank in the main bus is damped. The article also contains some switching-level EMTDC/PSCAD simulations to validate the work.
Sparse arrays combined with Minimum Variance (SMV) beamformer is suggested to improve the data rate while maintaining the quality image of ultrafast ultrasound imaging. The motivation is that obtaining high quality im...
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Sparse arrays combined with Minimum Variance (SMV) beamformer is suggested to improve the data rate while maintaining the quality image of ultrafast ultrasound imaging. The motivation is that obtaining high quality images requires the acquisition, processing and storage of a large amount of data so that, with sparsity (disabled some array elements positions in the reception), the amount of data to be stored should be reduced in order to increase the scan rate. The experiments of the proposed method were performed using simulated and in-vivo dataset available in the PICMUS website. The tests were performed using 128 elements for transmission and 128, 65, 44, and 23 elements sparsely distributed in the reception. The performance evaluation has been done using the Full Width at Half Maximum (FWHM) and the Contrast Ratio (CR). Results showed that the images generated by the proposed method, with reduced number of active elements in the reception, were close to those provided by DAS in terms of spatial resolutions and contrast, indicating that the proposed SMV method is suitable for ultrasound imaging.
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