918 research outputs found
New MMC capacitor voltage balancing using sorting-less strategy in nearest level control
No full textThis paper proposes a new strategy for balancing the Capacitor Voltages (CVs) for Modular Multilevel Converters (MMCs). The balancing is one of the main challenges in MMC applications and it is usually solved by adopting a global arm control approach. For performing such an approach, a sorted list of the SubModules (SMs) according to their capacitor voltages is required. A common way to accomplish this task is to implement a sorting algorithm in the same controller used for the modulation technique. However, the execution time and the computational efforts of these kinds of algorithms increase very rapidly when the number of SMs grows. A novel idea is presented in this paper by using a mapping strategy that directly stores in a ranked list the SMs according to the measured CVs. Avoiding the use of sorting algorithms leads to a considerable reduction of the execution time as well as the computational efforts
FPGA-based implementation of sorting networks in MMC applications
No full textIn this paper an implementation technique for Field Programmable Gate Array (FPGA) devices of two Sorting Networks (SNs) used for control of Modular Multilevel Converter (MMC) is presented. In such applications, the classical sorting algorithms are based on repetitive/recursive loops, and they are usually implemented in microcontrollers or DSPs. However, they are not convenient for hardware implementation due to their inherent sequential operation. Instead, the proposed SNs, are suitable for FPGA devices thanks to their fixed parallel structure that allows improving the timing performance of the capacitor voltage balancing algorithm. The advantages and the main challenges of the Bitonic SN and Even-Odd SN in MMC applications are discussed. Moreover, in order to pre-evaluate the required resources and the execution time, equations are derived for both the proposed SNs and then a comparison is performed between them. The proposed equations are validated by comparing the real required resources with the estimated ones by using the Xilinx Vivado Design Suite tool. Finally, the operation of the proposed Bitonic SN is also tested in Vivado Simulator, achieving the sorted list of 8 elements in 18 clock cycles as expected
System-on-chip implementation of embedded real-Time simulator for modular multilevel converters
No full textThe aim of this paper is to present the implementation of an Embedded Real-Time Simulator (ERTS) for Modular Multilevel Converters (MMCs), using low-cost System-on-Chip (SoC) platform. In order to achieve new functionalities such as sensor-less control, monitoring, diagnostic and fault detection, the MMC plant model can be implemented along with the controller. In MMC applications, the implementation of the RTS is particularly challenging due to the complex structure of the MMC and its stringent timing constraints, especially when the number of Sub-Modules (SMs) increases. In addition to the previous requirements, in case of ERTS, the hardware resources are also limited in order to keep low the cost of the entire controller. Moreover, the chosen device must also provide enough modulators for driving all the SMs and sufficient ADC interfaces for acquiring the capacitor voltages. For these reasons, a Xilinx Zynq SoC platform is adopted; this device provides two hard-processors along with the programmable gate array. In this work, the MMC plant model and the MMC controller are implemented in the two available microcontrollers, whereas, all the modulators and interfaces can be implemented in the programmable gate array. The achieved implementation is evaluated in terms of execution time and maximum allowable number of SMs. In order to validate the proposed implementation, HIL results for a single-phase MMC simulator are also provided
A Simplified Model based State-of-Charge Estimation Approach for Lithium-ion Battery with Dynamic Linear Model
Full text linkThe performance of model based State-of-Charge (SOC) estimation method relies on an accurate battery model. Nonlinear models are thus proposed to accurately describe the external characteristics of the Lithium-ion (Li-ion) battery. The nonlinear estimation algorithms and online parameter identification methods are needed to guarantee the accuracy of the model based SOC estimation with nonlinear battery models. A new approach forming a dynamic linear battery model is proposed in this paper, which enables the application of the linear Kalman filter for SOC estimation and also avoids the usage of online parameter identification methods. With a moving window technology, Partial Least Squares (PLS) regression is able to establish a series of piecewise linear battery models automatically. One element state space equation is then obtained to estimate the SOC from the linear Kalman filter. The experiments on a LiFePO4 battery prove the effectiveness of the proposed method compared with the Extended Kalman Filter (EKF) with two Resistance and Capacitance (RC) Equivalent Circuit Model (ECM) and the Adaptive Unscented Kalman Filter (AUKF) with Least Squares Support Vector Machines (LSSVM)
Single-point reactive power control method on voltage rise mitigation in residential networks with high PV penetration
No full textVoltage rise (VR) due to reverse power flow is an important obstacle for high integration of Photovoltaic (PV) into residential networks. This paper introduces and elaborates a novel methodology of an index-based single-point-reactive power-control (SPRPC) methodology to mitigate voltage rise by absorbing adequate reactive power from one selected point. The proposed index utilizes short circuit analysis to select the best point to apply this Volt/Var control method. SPRPC is supported technically and financially by distribution network operator that makes it cost effective, simple and efficient to eliminate VR in the affected network. With SPRPC none of the previous PV inverters need to upgrade and can retain their unity power factor to not to conflict with current grid codes. Comprehensive 24-h simulation studies are done on a modified IEEE 69-bus Network emulating a traditional residential power system with high r/x ratio. Efficacy, effectiveness and cost study of SPRPC is compared to droop control to evaluate its advantages
Development of a grid emulator for network integration studies
No full textIncludes bibliographical references.The economic and environmental side effects of fossil fuels have forced governments and authorities to investigate sustainable solutions. Main interest is focused on environment friendly benefits, provided by renewable energy sources. The growth rate of these energy sources has increased remarkably in the past few years. Correspondingly the research and development in the field of power electronics has also increased, especially in medium voltage and high power grid connected systems. The grid behaviour of the renewable energy systems is heavily influenced by the control techniques of these systems. For further development of these control methods the most basic and conventional way is to simulate, test and prove the system performance on a down-scaled lab test bench. The objective of this thesis is to develop a laboratory test bench grid emulator for network integration studies. Design and performance are investigated by introducing several kinds of unbalanced voltage conditions to test the behavior of connected systems. Voltage dips and swells are implemented to test the system’s performance
ENS Implementation - Part of the PSO Eltra contract 4524/2003
No full textwith PowerLynx A/S for the development of the ENS function for the PowerLynx PV inverters. The work started 01.01.03 and ended 29.02.04 and involved Frede Blaabjerg, Remus Teodorescu, Lucian Asiminoaei and Adrian Timbus from Aalborg University and Uffe Borup from PowerLynx A/S. The objective was to make the PowerLynx PV inverters compatible with the germans ENS standard which mainly consist in the requirement to disconnect from the grid in max. 2 seconds if the grid impedance is changed with 0.5 ohms resistive. During 01.07 ? 31.08 2003, an algorithm based on the injection of a voltage of 75 Hz and the on-line measurement the 75 Hz component from the grid current and voltage using simplified DFT was developed by Uffe Borup, Remus Teodorescu and Lucian Asiminoaei. The algorithm is described in detail in the report ?ENS design? enclosed in Appendix A and in the two published paper (final paper for APEC ?04 and approved digest for PESC ?04). Then the algorithm was finally implemented and the experimental test carried out proved to be satisfactory as shown in chapter 2 ?ENS implementation?. Very few missed tests were recorded on very high inductive grid (0.6 + 1.1i) when the reactance is higher than the resistance. In the period 03.02.04 ? 13.02.04 some attempts was done in order to improve the detection by compensating the delay in the voltage measurement but no improvement was noticed. Thus, these last minute changes was not included in the final version of the software. Finally, the detection mechanism of another PV running in parallel that injects t5Hz for ENS grid measurements has been done. The code for parallel ENS is also enclosed
Overview of Lithium-Ion Battery Modeling Methods for State-of-Charge Estimation in Electrical Vehicles
Full text linkAs a critical indictor in the Battery Management System (BMS), State of Charge (SOC) is closely related to the reliable and safe operation of lithium-ion (Li-ion) batteries. Model-based methods are an effective solution for accurate and robust SOC estimation, the performance of which heavily relies on the battery model. This paper mainly focuses on battery modeling methods, which have the potential to be used in a model-based SOC estimation structure. Battery modeling methods are classified into four categories on the basis of their theoretical foundations, and their expressions and features are detailed. Furthermore, the four battery modeling methods are compared in terms of their pros and cons. Future research directions are also presented. In addition, after optimizing the parameters of the battery models by a Genetic Algorithm (GA), four typical battery models including a combined model, two RC Equivalent Circuit Model (ECM), a Single Particle Model (SPM), and a Support Vector Machine (SVM) battery model are compared in terms of their accuracy and execution time
Meta-Analysis dataset: Methionine Sources for Weaned pigs
No full textThe datasets generated in the trials and by simulation during the current study belong to His Majesty the King in Right of Canada, as represented by the Minister of Agriculture and Agri-Food Canada. Data use is subject to obtaining permission of the representative of His Majesty the King in Right of Canada. Please contact the author for further information.Data collection (search strategy and inclusion criteria)A systematic review was conducted using the PRISMA statement (Page et al., 2021) to update the dataset previously used in a meta-analysis (Remus et al., 2015). The platforms Pubmed (126 references), ProQuest (235 references), Scopus (143 references) and Science Direct (1,663 references) were searched to identify studies reporting experimental dose-response results for the different Met sources used in pigs from weaning to finishing. The review question was proposed using the “PICo” framework, where a set of keywords was created, including elements designating population (pigs, piglets), interest (Met requirements, Met supplementation), and context (growth performance). After 293 duplicate references were removed, 1,898 studies remained. These studies were analyzed according to the following selection criteria: 1) research must have been conducted on pigs; 2) the paper must have been published between 1990 and 2021; 3) and it must present growth performance data. Based on these criteria, 1,779 papers were eliminated after the titles were assessed, while another 74 were eliminated after reading the abstract. An additional search in Google Scholar was performed. The keywords used were “pigs,” “Met,” and “growth,” and 24 adittional papers were selected according to the three previously stated criteria. At this step, the database comprised 45 references that were individually screened for full-text analysis. The inclusion criteria were as follows: 1) Studies must present treatments with different sources of free Met such as L-Met, DL-Met and/or OH-Met; 2) Free Met must have been provided at one or more inclusion levels; 3) Met must be the first limiting amino acid according to the material and methods; 4) Papers must present the nutritional composition of the experimental diets. A total of 33 studies were retained for the meta-analysis at the end of the evaluation process. Due to the small number of studies on the growing and finishing phase, only the post-weaning phase (5-25 kg body weight) was included in the analysis. Post-weaning data were present in 24 papers used in the meta-regression and meta-analysis. The ingredient composition of each diet was computed in spreadsheets and used to estimate (recalculate) the dietary composition in terms of net energy, SID AA, as well as mineral composition using the software EvaPig®. When available, the analyzed total AA composition provided by the authors was used to estimate SID values with EvaPig®.The codes used in the database are described on the Legend sheet
Geschichten von Onkel Remus
No full textForty-four stories and an afterword, with perhaps a dozen indifferent black-and-white line sketches and perhaps a dozen good colored pictures, generally a full page in size. The afterword goes out of its way twice to mention that the successors of the white masters still repress the Blacks today. It opens with a great quotation from Uncle Remus: if these stories were nothing but fun, the stuff of laughter, he would not have troubled himself with them. The binding and covers of this book are curiously flexible.Language note: GermanJoel Chandler Harris and Rolf F. Mülle
- …
