Recently NAFU SA and other role players expressed some criticism about government programmes. The criticism was not so much about the objectives and content of these programmes, but rather about their accessibility, or lack thereof, to emerging farmers.

What about the messenger

I introduce batman, a Python package for modeling exoplanet transit light curves. The batman package supports calculation of light curves for any radially symmetric stellar limb darkening law, using a new integration algorithm for models that cannot be quickly calculated analytically. The code uses C extension modules to speed up model calculation and is parallelized with OpenMP. For a typical light curve with 100 data points in transit, batman can calculate one million quadratic limb-darkened models in 30 seconds with a single 1.7 GHz Intel Core i5 processor. The same calculation takes seven minutes using the four-parameter nonlinear limb darkening model (computed to 1 ppm accuracy). Maximum truncation error for integrated models is an input parameter that can be set as low as 0.001 ppm, ensuring that the community is prepared for the precise transit light curves we anticipate measuring with upcoming facilities. The batman package is open source and publicly available at https://github.com/lkreidberg/batman. Subject headings: methods: data analysis – methods: numerical

batman: BAsic Transit Model cAlculatioN in Python

Multilevel inverters (MLIs) are being used in wide range of power electronic applications. These converters have attracted a lot of attention during recent years and exist in different topologies with similar basic concepts. This paper presents five main submodules (SMs) to be used as the basic structures of MLIs. The paper reviews the common MLI topologies from the structural point of view. The topologies are divided into the different SMs to show conventional MLI configurations and future topologies that can be created from the main SMs. A comparative study between different topologies is performed in detail. The MLIs are categorized and investigated with from different perspectives such as the number of components, the ability to create inherent negative voltage, working in regeneration mode and using single dc source.

A General Review of Multilevel Inverters Based on Main Submodules: Structural Point of View

Doppler spectroscopy has uncovered or confirmed all the known planets orbiting nearby stars. Two main techniques are used to obtain precision Doppler measurements at optical wavelengths. The first approach is the gas cell method, which consists on the least-squares matching of the spectrum of Iodine imprinted on the spectrum of the star. The second method relies on the construction of a stabilized spectrograph externally calibrated in wavelength. The most precise stabilized spectrometer in operation is HARPS, operated by ESO in La Silla Observatory/Chile. The Doppler measurements obtained with HARPS are typically obtained using the Cross-Correlation Function technique (CCF). It consists of multiplying the stellar spectrum with a weighted binary mask and finding the minimum of such product as a function of the Doppler shift. It is known that CCF is suboptimal in exploiting the Doppler information in the stellar spectrum. Here, we describe an algorithm to obtain precision RV measurements using least-squares matching of each observed spectrum to a high signal-to-noise ratio template derived from the same observations. Such algorithm is implemented in our software called HARPS-TERRA (Template Enhanced Radial velocity Re-analysis Application). New radial velocity measurements on a representative sample of stars observed by HARPS is used to illustrate the benefits of the proposed method. We show that, compared to CCF, template matching provides a significant improvement in accuracy, specially when applied to M dwarfs.

The HARPS-TERRA project I. Description of the algorithms, performance and new measurements on a few remarkable stars observed by HARPS

In this paper, finite-set model-predictive control (FS-MPC) methodologies for a grid-connected three-level neutral-point-clamped converter are investigated. The proposed control strategies produce fixed switching frequency, maintaining all the advantages of predictive control such as fast dynamic response, inclusion of nonlinearities and restrictions, and multivariable control using a single control loop. The first of the proposed FS-MPC strategies is based on a multiobjective cost function, designed to regulate both the inverter currents and the balancing of the dc-link capacitor voltages. The second FS-MPC strategy is derived from the first one, and it is based on a cost function that regulates only the grid current, with the balancing of the capacitor voltages being realized by controlling the duty cycles of the redundant vectors. The proposed control systems are experimentally validated using a 5-kW prototype. The experimental results show a good performance for both strategies, in steady-state and transient response, with a total harmonic distortion lower than $\text{2}\%$ for the currents supplied to the grid.

Finite-Set Model-Predictive Control Strategies for a 3L-NPC Inverter Operating With Fixed Switching Frequency

The continuous monitoring of the energy storage system in electric vehicles is essential for safe operation. In particular, most electric vehicles use Lithium-ion batteries due to their power and energy density, which can introduce instability in their performance. Recently, the use of digital twins has been able to provide more information to the battery management system for real-time decision-making. This paper presents an overview of the main methods for modeling lithium-ion batteries and the identification of parameters of these models, summarizing their advantages and disadvantages. In addition, the application of the linear parameter-varying representation and their contributions are discussed. Finally, digital twin methods applied to battery management systems are described, and their main functionalities are analysed.

An Overview of Digital Twins Methods Applied to Lithium-Ion Batteries

Several off-the-shelf real-time control systems are available for industrial and academic applications. These systems enable real-time control and prototyping of power electronic applications. However, most of these systems have a considerable cost and are inflexible, limiting their teaching and academic research usage. Consequently, this paper presents the design and implementation of a control platform based on a low-cost easy-to-program microcontroller from Texas Instruments. The proposed control platform is intended for rapid-control-prototyping, and it considers optic PWM outputs, isolated sensing of voltage/currents, multipurpose input-outputs, and hardware protections. Experimental results are presented to validate the usefulness of the proposed control platform.

Design and Implementation of an off-the-shelf Controller for Power Electronics Research and Teaching

Modular Multilevel Converters have been proposed for high-voltage direct current and Low-Frequency Alternating Current transmission systems according to benefits associated with their topologies, such as scalability, modularity, high voltage and power capacity. In industrial applications, hundreds of power cells have to be connected in a cascade to reach high-power ratios. However, most of the academic prototypes are equipped with a low number of power cells to validate academic research. Moreover, they are limited to conventional frequency operation in AC ports over the range of 50-60Hz. Hence, this paper presents the experimental results of a Modular Multilevel Converter test-bench comprised of sixty power cells and through OPAL-RT cabinets. Partial results validate a power flow regulation with power factor correction for low-frequency operation at 10-20 HZ.

Experimental Assessment of a Modular Multilevel Converter using OPAL-RT Control and Power Stages for Low-Frequency AC transmission systems

In this paper is presented a simple method to design an inductor for high performance on a DC-DC Modular Multilevel Converter(MMC). This element is one of the main limitations for a proper fulfilment. A high-frequency inductor for high power applications is a key element to achieve high efficiency in such type of converters. The theoretical design of the inductor is compared with an experimental prototype, which is then implemented in a high-power DC-DC converter. Experimental results validate the accuracy of the theoretical design and the improvements in the efficiency of the overall DC-DC high power converter.

Inductor design for a High performance DC-DC Modular Multilevel Converter

The modular multilevel converter (MMC) based on half-bridge modules is a power converter topology suitable for high-power medium-voltage variable-speed drives. However, the voltage of its flying capacitors is negatively affected when low frequencies appear at the AC port. This paper analyzes the influence of using a variable DC port voltage in a machine-side MMC by implementing a closed-loop approach, ensuring a constant voltage fluctuation in the capacitors of the MMC during the whole operating range. The effectiveness of the proposed control scheme is demonstrated through simulation studies and experimental validation tests conducted using a 7.5 kW experimental prototype composed of an induction machine fed by an MMC with 18 half-bridge cells.

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Matias Diaz

Papers

An Overview of Digital Twins Methods Applied to Lithium-Ion Batteries

Design and Implementation of an off-the-shelf Controller for Power Electronics Research and Teaching

Experimental Assessment of a Modular Multilevel Converter using OPAL-RT Control and Power Stages for Low-Frequency AC transmission systems

Inductor design for a High performance DC-DC Modular Multilevel Converter

The Closed-Loop Control of the Half-Bridge-Based MMC Drive with Variable DC-Link Voltage