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We investigate the stability properties of a multi-converter power system model, defined on a high-order manifold. For this, we identify its symmetry (i.e., rotational invariance) generated by a static angle shift and rotation of AC signals. We characterize the steady state set, primarily determined by the steady state angles and DC power input. Based on eigenvalue conditions of its Jacobian matrix, we show asymptotic stability of the multi-converter system in a neighborhood of the synchronous steady state set by applying the center manifold theory. We guarantee the eigenvalue conditions via an explicit approach. Finally, we demonstrate our results based on a numerical example involving a network of identical DC/AC converter systems.

International audience; This article deals with circuit modeling of power systems and more particularly of DC/AC converters used for controlling electric motors. The objective of the model is to be able to assess conducted emission currents at both inputs and outputs in order to apply appropriate mitigation design rules such as filtering. First, we propose a linear Thevenin block-model of the converter considering it as a 5-port linear black-box allowing possible interaction between the DC and AC ports. To this extent, the block-model is made of an impedance matrix and a Thevenin voltage generators vector. We also propose theoretical relationships allowing the processing of data in order to be able to generate this model from measurements. Then, we test the linear simplifications on a real DC/AC converter and compare the results to measurements. For this, S-parameter measurements in offmode and currents at the 5 ports in on-mode are used for the characterization of the model on a first test setup. The model is then applied and checked by comparing circuit simulated and measured current responses on a modified test setup for which the lengths of the connection cables are modified. Finally, the capability of this block-model to extrapolate by calculation the response of other installation configurations is showed considering the design of a filter and its insertion at input/output ports of the converter with much longer cables.

In the last decades, electric power produced through photovoltaic conversion has been increasing because of the need to reduce fossil fuel burning. Recently, photovoltaic systems have become more competitive and their role in the renewable energies market share is steadily gaining in importance. Improvements in the power electronics employed in the DC/AC conversion are topics of interest in the quest for more efficient and eventually reduced-cost inverters. The goal of this paper is to perform an investigation of control strategies and propose a topology for a single-phase DC/AC converter for photovoltaic arrays using the simulation software Power System Computer Aided Design/ Electromagnetic Transient Design and Control (PSCAD/EMTDC). The circuit proposed in this paper employs an isolating transformer to a grid-connected photovoltaic inverter. The control strategy proposed uses the instantaneous reactive power theory (p–q theory) and phase-locked loop (PLL). The p-q theory uses two virtual axes in the Park Transformation, which provide to the control system a good dynamic response, accuracy, and decoupling between the control and power system. Computer simulations using the electromagnetic transient software PSCAD show the efficiency of the proposed strategy for a single-phase inverter. The control strategy and topology are quite simple and easy to implement in the future using a Digital Signal Processor (DSP). The results provide insights into new power electronics solutions, which can improve the efficiency and efficacy of the current available in DC/AC converters for photovoltaic systems.

This paper presents a unified approach to the analysis of DC/AC converters based on an equivalent representation of their AC circuit as a series RLC circuit. The resonant DC/AC converter with reverse diodes was chosen as the basis of the examination, and the obtained ratios for this device were used to derive the main ratios describing the operation of the other types of DC/AC converters—voltage source inverters (VSI) and current source inverters (CSI). Based on the commonality of electromagnetic processes in power circuits, the expressions for the current through the inductance and the voltage of the capacitor are found in a compact form with their initial phases. The base ratios found through the analysis are normalized to the control frequency, thereby summarizing all possible operating modes. In this way, electromagnetic processes in a whole class of power electronic devices are described from general positions, which is convenient from a methodical point of view with a view to improving power electronics education. The proposed analysis approach is also applicable to three-phase DC/AC inverters, taking into account the specifics related to the presence of three phases and, accordingly, their mutual influence in the formation of the output currents and voltages. On the other hand, the basic ratios determined through the application of the unified analysis approach are also useful with a view to creating engineering design methodologies, in which the values of all circuit elements are determined with comparatively simplified calculation procedures.

Nas últimas décadas, verifica-se um crescente interesse na utilização da energia elétrica produzida por sistemas fotovoltaicos. Isto se deve ao fato de haver um decréscimo no incentivo quanto ao uso de combustíveis fósseis, tais como o carvão e o petróleo. Desta forma, verifica-se a importância de melhoramentos constantes no tratamento e controle da energia proveniente dos módulos fotovoltaicos, buscando uma melhor eficiência e eficácia de seus sistemas de controle e sistemas conversores CC/CC e CC/CA. O objetivo deste trabalho é realizar a investigação de uma proposta de estratégia de controle para um inversor CC/CA monofásico, isolado através de transformador de alta frequência (high frequency) e conectado à rede elétrica através de um indutor monofásico (ongrid) com alimentação proveniente de um conjunto de módulos fotovoltaicos. A estratégia de controle proposta se baseou em um sistema Phase Locked Loop (PLL) utilizando a teoria da potência reativa instantânea (p–q theory), no qual utilizou dois eixos virtuais pela transformação de Clark e de Park e permitindo uma boa velocidade de resposta, precisão e desacoplamento entre o sistema de controle e o sistema de potência. Simulações computacionais utilizando o software para Modelagem de Sistemas de Potência e Simulação de Transitórios Eletromagnéticos PSCAD/EMTDC demonstram a eficiência da estratégia proposta para o sistema inversor proposto através dos resultados gráficos das potências de entrada (fornecidas pelo conjunto de módulos fotovoltaicos) bem como pelos resultados das potências de saída (fornecidas pelo inversor monofásico). A estratégia proposta demonstrou-se simples e possuindo como característica a facilidade de implementação através de um Processador de Sinais Digitais (DSP – Digital Signal Processor), proporcionando eficiência e eficácia compatíveis com os obtidos nos inversores CC/CA atuais. In the last decades, electric power produced through solar panels is increasing due to the deterrent in the use of fossil fuels like coal and petrol. Constant improvement on treatment and control of solar panel power demands the development of efficient and effective control systems for DC/DC and DC/AC converters. The goal of this work is to perform an investigation about the control’ strategy of a single-phase DC/AC converter, which has an isolation high-frequency transformer and a single-phase inductor (On-Grid) to connect the inverter to the power grid of the electrical system. The control strategy proposed uses the theory of the instantaneous reactive power (p– q theory) and Phase-Locked Loop (PLL). The p-q theory uses two virtual axes in Park Transformation which provide to the control system good velocity response, accuracy and decoupling between the control system and power system. Computer simulations using electromagnetic transient simulation software PSCAD/EMTDC show the efficiency of the strategy proposed for a single-phase inverter from input power graphics results (from solar panel cluster) as well as the output power graphics results (provided by single-phase inverter). The control strategy proposed proved to be simple and easy to implement using a Digital Signal Processor (DSP) which contributes to the improvement of present DC/DC converters.

For multi-applications, a novel universal switched-capacitor (SC) converter is proposed in this paper. The proposed converter consists of a rotation-type SC converter and a full-bridge circuit. Unlike the existing universal converter consisting of a series–parallel type converter and a full-bridge circuit, the rotation-type SC converter can offer an output voltage in all clock cycles by rotating the connection position of capacitors. Therefore, the proposed universal SC converter can achieve four types of conversion with high power efficiency, namely, step-up/step-down dc/dc conversion, step-down ac/dc conversion, step-up multilevel dc/ac conversion, and direct step-up/step-down ac/ac conversion. Through theoretical analysis, computer simulations, and bread board experiments, the characteristics of the proposed universal SC converter are evaluated. The result of these analyses demonstrates the feasibility of the proposed universal SC converter. Keywords: Universal converters, DC/DC converters, AC/DC converters, DC/AC converters, AC/AC converters, Inductor-less converters

With the ever-growing aviation industry, energy researches on aviation have turned to renewable energy sources providing electric propulsion. Fuel cells are one of the most popular sources of power for electric vehicles terms of being greener, more reliability, and higher efficiency. Among fuel cells, the most attractive option for flight is polymer electrolyte membrane fuel cells (PEMFC). This paper aims to compose of a hybrid propulsion system to a lightweight aircraft Cri-Cri for more electric aircraft concept. For this purpose, first, conceptual a hybrid propulsion system is designed for the prototype aircraft. The fuel-cell hybrid system proposed for this paper consists of electric motor, fuel cell system, battery, DC/AC converter, and DC/DC converter. Second, some analyses are done. These analyses contain required power, hydrogen consumption, energy consumption, etc.. As a result, Cri-cri needs 26 Kw during take-off, 30 Kw during climb, 10 kW during cruise, and 7 kW during descent. It also consumed 0.75 kg of hydrogen in total, including 0.21 kg in the take-off and climb, 0.42 kg in the cruise, and 0.12 in the descent. The remaining 0.25 kg of hydrogen is reserved for use in emergencies. The total amount of energy consumed is 33 kWh.

Classically, the energy conversion architecture found in photovoltaic (PV) power plants includes solar arrays delivering a maximum voltage of 1kV followed by a step-up chopper connected to a three-phase Voltage Source Inverter. This multistage conversion system (DC/DC + DC/AC) is then connected to the medium-voltage grid through a low-voltage/medium-voltage transformer. In order to simplify the PV systems, this research work focuses on the study and implementation of a DC/AC topology employing a single power processing stage: the three-phase Current Source Inverter (CSI). To deal with the inconvenient of high conduction losses when implementing this topology, wide-bandgap Silicon Carbide (SiC) semiconductors are used, allowing to efficiently convert energy while keeping a relatively high switching frequency. Nonetheless, since the available power semiconductor modules on the market are not compatible with the CSI, a novel 1.7kV SiC-based voltage bidirectional module is developed in the context of this thesis. Hence, the dynamic characterization of the new SiC device is carried out and serves as the basis for the design of a 60kW CSI prototype.Finally, the inverter efficiency is evaluated at nominal operating conditions, employing both a calorimetric and electrical methods. The obtained results confirm the CSI ability to operate efficiently at high switching frequencies (η>98.5% @60kHz). The originality of this work lies mainly in the design, characterization and implementation of the new 1.7kV full-SiC power module adapted to the CSI topology.; Classiquement, la chaîne de conversion d’énergie électrique des centrales photovoltaïques comporte un champ photovoltaïque (PV) délivrant une tension maximale de 1kV suivi d’un hacheur élévateur connecté à un onduleur de tension triphasé. Cette chaîne de conversion à deux étages (DC/DC + DC/AC) est ensuite raccordée sur le réseau moyenne tension à l’aide d’un transformateur élévateur. Dans l’objectif de simplifier les systèmes de conversion PV, ce travail de recherche s’intéresse à l’étude et la mise en oeuvre d’une topologie DC/AC n’employant qu’un seul étage de conversion : l’onduleur de courant triphasé. Bien que relativement simple, l’onduleur de courant présente comme inconvénient majeur ses pertes par conduction. Pour pallier à ce problème, des interrupteurs grand-gap au Carbure de Silicium (SiC) sont employés, ce qui permet de convertir l’énergie à haut rendement ( > 98.5%) tout en gardant une fréquence de découpage élevée (plusieurs dizaines de kHz). Les modules à semi-conducteurs de puissance disponibles sur le marché n’étant pas compatibles avec ce type de convertisseur, des modules dédiés intégrant du SiC ont été développés dans le cadre de cette thèse. La caractérisation dynamique de ces nouveaux modules a été réalisée dans le but de servir de point d’appui à la conception d’un démonstrateur d’onduleur de courant d’une puissance nominale de 60kW. Enfin, le rendement de la partiesemi-conducteur de puissance est évalué à l’aide d’une méthode calorimétrique confirmant la capacité de cette topologie à fonctionner à des fréquences de découpage plus élevées. L’originalité de ces travaux réside principalement dans la conception, la caractérisation ainsi que la mise en oeuvre d’un nouveau module de puissance dédié à cette topologie. Cette dernière étant connue mais peu étudiée à l’heure actuelle avec des interrupteurs au SiC.

Classically, the energy conversion architecture found in photovoltaic (PV) power plants includes solar arrays delivering a maximum voltage of 1kV followed by a step-up chopper connected to a three-phase Voltage Source Inverter. This multistage conversion system (DC/DC + DC/AC) is then connected to the medium-voltage grid through a low-voltage/medium-voltage transformer. In order to simplify the PV systems, this research work focuses on the study and implementation of a DC/AC topology employing a single power processing stage: the three-phase Current Source Inverter (CSI). To deal with the inconvenient of high conduction losses when implementing this topology, wide-bandgap Silicon Carbide (SiC) semiconductors are used, allowing to efficiently convert energy while keeping a relatively high switching frequency. Nonetheless, since the available power semiconductor modules on the market are not compatible with the CSI, a novel 1.7kV SiC-based voltage bidirectional module is developed in the context of this thesis. Hence, the dynamic characterization of the new SiC device is carried out and serves as the basis for the design of a 60kW CSI prototype.Finally, the inverter efficiency is evaluated at nominal operating conditions, employing both a calorimetric and electrical methods. The obtained results confirm the CSI ability to operate efficiently at high switching frequencies (η>98.5% @60kHz). The originality of this work lies mainly in the design, characterization and implementation of the new 1.7kV full-SiC power module adapted to the CSI topology., Classiquement, la chaîne de conversion d’énergie électrique des centrales photovoltaïques comporte un champ photovoltaïque (PV) délivrant une tension maximale de 1kV suivi d’un hacheur élévateur connecté à un onduleur de tension triphasé. Cette chaîne de conversion à deux étages (DC/DC + DC/AC) est ensuite raccordée sur le réseau moyenne tension à l’aide d’un transformateur élévateur. Dans l’objectif de simplifier les systèmes de conversion PV, ce travail de recherche s’intéresse à l’étude et la mise en oeuvre d’une topologie DC/AC n’employant qu’un seul étage de conversion : l’onduleur de courant triphasé. Bien que relativement simple, l’onduleur de courant présente comme inconvénient majeur ses pertes par conduction. Pour pallier à ce problème, des interrupteurs grand-gap au Carbure de Silicium (SiC) sont employés, ce qui permet de convertir l’énergie à haut rendement ( > 98.5%) tout en gardant une fréquence de découpage élevée (plusieurs dizaines de kHz). Les modules à semi-conducteurs de puissance disponibles sur le marché n’étant pas compatibles avec ce type de convertisseur, des modules dédiés intégrant du SiC ont été développés dans le cadre de cette thèse. La caractérisation dynamique de ces nouveaux modules a été réalisée dans le but de servir de point d’appui à la conception d’un démonstrateur d’onduleur de courant d’une puissance nominale de 60kW. Enfin, le rendement de la partiesemi-conducteur de puissance est évalué à l’aide d’une méthode calorimétrique confirmant la capacité de cette topologie à fonctionner à des fréquences de découpage plus élevées. L’originalité de ces travaux réside principalement dans la conception, la caractérisation ainsi que la mise en oeuvre d’un nouveau module de puissance dédié à cette topologie. Cette dernière étant connue mais peu étudiée à l’heure actuelle avec des interrupteurs au SiC.

In many applications of power converters, an AC voltage with a controllable/variable frequency and voltage amplitude is desired (e.g., in motor-drive applications). By contrast, in the case of grid-connected applications (e.g., photovoltaic systems), the output AC voltage should be “constant” in terms of frequency and amplitude. In all, a power electronic interface is required to link the DC source with the load and to make the output AC voltage compatible in terms of phase, frequency, and amplitude. This power processing is called DC/AC conversion, and the power converters are referred to as DC/AC converters, also known as DC/AC inverters. Depending on the system power ratings, there are typically single- and three-phase DC/AC converters. In order to achieve the above goal (e.g., a constant-voltage and constant-frequency AC voltage), a proper control should be employed. In this chapter, the modeling and control of DC/AC converters are briefly presented in different reference frames (i.e., αβ- and dq-reference frames). The design of commonly employed DC-link and current controllers is in focus with different case studies.

International audience; This paper presents energy management improvement for a Hybrid Electric Boat (HEB) applications using frequency approach. A variable speed Diesel-Permanent Magnet Generator (Diesel-PMG) is assisted by the lithium-battery to satisfy energetic demand of HEB. The lithium-battery module is connected to DC-bus through a buck-boost converter, and that of the variable speed Diesel Generator, it is connected to DC-bus using three phase controlled rectifier. The two DC/AC converters connected to two electric motors are used as thrusters system which enables to emulate energetic demand of Hybrid Electric Boat (HEB) in propulsion operations. The power requirement of thrusters is added to embedded appliances demand to obtain load's profile. The contribution of this paper is focused on load's profile sharing between a variable speed Diesel Generator and Lithium-battery according to the dynamic responses of sources. The performances of proposed method are evaluated through some simulations using MATALB/Simulink software and experimental tests in reduced scale.

International audience; This paper presents energy management improvement for a Hybrid Electric Boat (HEB) using frequency approach. Diesel generator is assisted by supercapacitors and lithium-battery to satisfy energetic demand of hybrid electric boat. Supercapacitors and lithium-battery are linked to DC-bus through two bidirectional converters, and diesel generator is connected to DC-bus using three phase controlled rectifier. DC/AC converters connected to two electric motors are used as thrusters system which enables to emulate energetic demand of Hybrid Electric Boat (HEB) in propulsion operations. The power requirement of thrusters is added to embedded appliances demand to obtain load's profile. The contribution of this paper is focused on load's profile sharing between Diesel generator, supercapacitors and lithium-battery according to the dynamic responses of these sources. Proposed method performances are evaluated through some simulations using MATALB/Simulink software.

This paper deals with the design analysis and synthesis of power resonant inverter with sinusoidal output voltage for sensitive loads. The proposed filter must be capable of removing higher harmonic components from the supplying voltage to reach a harmonic distortion of roughly 5% in the whole range of the load (0 − 100%). The inverter can be supplied from either single-phase voltage inverter in full- or half- bridge connection, or from simple DC/DC buck converter. Non-symmetrical control causes higher harmonic content, both odd and even. Simulation and experimental results based on designed parameters and subsequently obtained from Matlab and OrCad models confirm good quality of output quantities, voltage and current., Tema je ovog članka analiza dizajna i sinteza učinskog rezonantnog invertera sa sinisuidalnim izlaznim naponom za osjetljive terete. Predloženi filtar mora moći filtrirati više harmonike ulaznog napona kako bi distorzija harmonika bila oko 5% u čitavom radnom području (0−100%). Inverter se može napajati ili iz jednofaznog naponskog invertera u mosnom ili uzrokuje pojavu viših harmonika u signalu, kako parnih tako i neparnih. Simulacijski i eksperimentalni rezultati temeljeni na sintetiziranim parametrima dobivenim od modela napravljenih u programskim paketima Matlab i OrCad potvr.uju dobru kvalitetu izlaznih veličina napona i struje.

A back-to-back HVDC converter system is typically used to connect two separate electrical grids or a remote large-scale renewable energy system with the electrical grid through a DC bus. The DC bus typically contains a large electrolytic capacitor giving a robust performance to the converter system. However, it is well known that the electrolytic DC bus capacitor is bulky and has a low reliability. Therefore, a possible solution to these drawbacks is to use a reduced DC bus capacitance, which will allow film capacitors to be used instead of electrolytic capacitors. This paper presents the performance evaluation of a five-level flying capacitor (FC) back-to-back converter system with reduced DC bus capacitance under different modulation schemes. Two carrier-based modulation strategies are studied, namely the phase shifted pulse-width modulation (PS-PWM) and the phase disposition pulse-width modulation (PD-PWM), along with their appropriate flying capacitor voltage balancing techniques. The classical synchronous reference frame control strategy has been implemented in order to provide DC bus voltage regulation and active/reactive power control. The performance of the two different modulation schemes is tested against the DC bus and FCs voltage ripples using the MATLAB/Simulink-PLECS software platform. The analyzed case studies demonstrate that the PS-PWM strategy is more suitable to operate the proposed FC converter system using reduced values for the DC bus and flying capacitors.

Auxiliary power supply for modern railway vehicles, powered from the DC catenary line, today is typically connected to the line through an inverter, and an output three-phase transformer. Generally, inverter includes DC component in its output voltage because of difference in switching behaviour of power devices which are used in the power converters. DC component leads to the magnetic field saturation of the transformers, which causes energy loss, and acoustic noise. Therefore, it is necessary to prevent the appearance of DC component on the inverter output. This paper proposes the basic methods used in practice to reduce adverse effects of DC component on the operation of three-phase transformer.

The advances in computing and communication technologies allow to connect inverters of energy generation systems in smart grids, to well control the power flows. Modeling tools would be helpful in the design of required new inverter topology. This paper presents a modeling technique, so called Power Oriented Graph, easy to use and to be implemented in Matlab-Simulink environment. This technique has been used for modeling a recently proposed soft-switching grid-connected DC/AC power converter for photovoltaic systems. Modifications in the structure of the DC/DC converter and in the control of the DC/AC converter for smart grid applications are proposed. Simulation results confirm the effectiveness of the presented models and the introduced improvements.