Conception et caractérisation d'une antenne active en technologie uniplanaire

Théorie des oscillateurs micro-ondes -- Topologies de base des oscillateurs avec des résonateurs LC -- Oscillateurs contrôlés en tension -- Modélisation des composants actifs -- Modèle physique du transistor -- Modèle du circuit électrique équivalent -- Détermination des paramètres extrinsèques du modèle électrique -- Modélisation des éléments non-linéaires d'un MESFET -- Modélisation d'un diode varactor -- Mesures des caractéristiques du transistor et de la diode varactor -- Oscillateur contrôlé en tension à 5.8 GHz réalisé avec des lignes de transmission microrubans -- Oscillateur réalisé avec des lignes de transmission coplanaires -- Antenne active uniplanaire à 4 GHZ

Lifetime investigations of a lithium iron phosphate (LFP) battery system connected to a wind turbine for forecast improvement and output power gradient reduction

Lithium Ion batteries and especially Lithium Iron Phosphate (LFP) batteries can be characterized by high power densities, relatively long life-time, no maintenance and a lot of research currently being done on increasing their performance. Therefore, they seem to be a good choice for integration with wind turbines. However, the current Lithium Ion energy storage price and its limited lifetime are the main obstacles to the integration of storage technologies with wind turbines. That is why proper lifetime estimation of the lithium ion batteries, working with mission-profile characteristics for specific services, is very important, not only for optimisation of the revenues but also for correct scheduling of the maintenance jobs. This paper analyzes the connection of LFP battery storage systems into wind turbines, with a high focus on the lifetime of LFP batteries for selected services.Postprint (published version

New AC–AC Modular Multilevel Converter Solution for Medium-Voltage Machine-Drive Applications:Modular Multilevel Series Converter

Due to its scalability, reliability, high power quality and flexibility, the modular multilevel converter is the standard solution for high-power high-voltage applications in which an AC–DC–AC connection is required such as high-voltage direct-current transmission systems. However, this converter presents some undesired features from both structural and operational perspectives. For example, it presents a high number of components, which results in high costs, size, weight and conduction losses. Moreover, the modular multilevel converter presents problems dealing with DC-side faults, with unbalanced grid conditions, and many internal control loops are required for its proper operation. In variable-frequency operation, the modular multilevel converter presents some serious limitations. The most critical are the high-voltage ripples, in the submodule capacitors, at low frequencies. Thus, many different AC–AC converter solutions, with modular multilevel structure, have been proposed as alternatives for high-power machine-drive applications such as offshore wind turbines, pumped-hydro-storage systems and industrial motor drives. These converters present their own drawbacks mostly related to control complexity, operational limitations, size and weight. This paper introduces an entirely new medium-voltage AC–AC modular multilevel converter solution with many operational and structural advantages in comparison to the modular multilevel converter and other alternative topologies. The proposed converter presents high performance at low frequencies, regarding the amplitude of the voltage ripples in the submodule capacitors, which could make it very suitable for machine-drive applications. In this paper, an analytical description of the voltage ripples in the submodule capacitors is proposed, which proves the high performance of the converter under low-frequency operation. Moreover, the proposed converter presents high performance under unbalanced grid conditions. This important feature is demonstrated through simulation results. The converter solution introduced in this paper has a simple structure, with decoupled phases, which leads to the absence of undesired circulating currents and to a straightforward control, with very few internal control loops for its proper operation, and with simple modulation. Since the converter phases are decoupled, no arm inductors are required, which contributes to the weight and size reduction of the topology. In this paper, a detailed comparison analysis with the modular multilevel converter is presented based on number of components, conduction and switching losses. This analysis concludes that the proposed converter solution presents a reduction in costs and an expressive reduction in size and weight, in comparison to the modular multilevel converter. Thus, it should be a promising solution for high-power machine-drive applications that require compactness and lightness such as offshore wind turbines. In this paper, simulation results are presented explaining the behavior of the proposed converter, proving that it is capable of synthesizing a high-power-quality load voltage, with variable frequency, while exchanging power with the grid. Thus, this topology could be used to control the machine speed in a machine-drive application. Finally, experimental results are provided to validate the topology

Full-bridge MMC DC fault ride-through and STATCOM operation in multi-terminal HVDC grids

This paper investigates a control structure to enhance the DC fault ride-through capability of a full-bridge modular multilevel converter (MMC) station, while ensuring a stable controlled operation as a STATCOM during DC faults without the need for fault isolation. Taking advantage of the switching states of a full-bridge submodule, a DC current controller is proposed, which provides the DC voltage reference for the modulation when a DC fault is detected. By changing the outer controllers strategy from DC voltage or active power control to converter energy control during a fault, the decoupling of the converter operation from the DC side dynamics is realized. In this paper, the focus is on the control methodology at all times of operation and the evaluation of the STATCOM control during a fault. To this end, extensive simulations were performed on a three-terminal high voltage direct current (HVDC) grid in radial configuration and a pole-to-pole DC fault case was investigated. The results showed that the AC voltage and current were controlled within limits at all times, while the full-bridge MMC was able to provide reactive power support to the AC grid. Moreover, using the proposed control methodology, the transients at the operation transition points between STATCOM and inverter/rectifier operation were minimized and the stations were able to safely ride through the fault