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This study presents a control method for DC–DC switching power converters to avoid the instability caused by the interaction between a tightly controlled switching converter and an input low-pass filter. The proposed method is based on the Lyapunov stability criterion. A non-linearised model is established, and the instantaneous quantities of the state variables are considered. The switching command is formulated by calculating the stability of the system. The inductor current and voltage across the filter capacitor, along with the state variables in the switching converter, follow the corresponding references. A boost converter is considered to demonstrate the associated effectiveness. The results of several simulations and experiments pertaining to the start-up, tracking, and regulation stages validate the proposed control approach. Moreover, the robustness of the approach against variations in the parameters of the controlled system is examined experimentally. To demonstrate the superiority of the proposed method, the method is compared with the proportional–integral, fuzzy, and flatness-based controllers.

International audience; Most of researchers have already studied and discussed the power sharing and synchronization of several generation systems connected to a unique point of common coupling (PCC) to which the loads are also connected. A high penetration rate of distributed generation systems (DGs) based on renewable energies has for logic consequence the development and setting up of networked multi-PCC microgrids. In this paper an improved droop control method for synchronization as well as active and reactive power sharing of different DGs in multiple PCC islanded microgrids is proposed while the real characteristics of the line feeders are taken into account. The simulation results confirm the feasibility and effectiveness of the proposed strategies for synchronization and interconnection of different microgrid DGs, while insuring accurate sharing of the DGs active and reactive powers. 

International audience; During the lifespan of a Polymer Electrolyte Membrane Fuel Cell (PEMFC) system, some heterogeneities between the cells constituting the stack can appear. The voltage of one particular cell in a stack may decrease because of specific aging or local malfunctioning such as drying. As a result, more heat is generated in this cell leading to an increase in its temperature and thus an additional voltage loss. This snowball effect can result in the failure of the cell. Therefore, the lifetime of a PEMFC stack can be increased by applying energy management to its cells. Notable that the output voltage of a cell is lower than a stack. Hence, a high conversion ratio converter is necessary to implement such energy management. An efficient way to increase the output voltage is to connect the output capacitors of the converters such as the boosts in series. Ensuring the converters' controllability is a key point to implement energy management. In this paper, an equalizer system is proposed to ensure the controllability of the boost converters. The balancing speed and the low number of switches are the main advantages of this system. The validity of the proposed system is verified through simulation and experiments.

International audience; This paper proposes a control method for a switching power converter. This converter is connected to a dc-link of a dc microgrid system via an LC input filter. This control method is based on a Lyapunov stability analysis; all state variables are acquired for evaluating stability analysis, including the output current for calculating the load resistance. To reduce a number of sensor counts, the input current is estimated. Moreover, loss occurrence in the converter is observed to reduce static errors of the controlled state variables, especially the output voltage. The losses are modelled as a series input voltage source observed from the dc-dc converter and a parallel current source. The latter enables us to eliminate the output current sensor. Using information from the estimated current source, a load resistance can be calculated. A Lyapunov function candidate is chosen to ensure that the system, including the observer, operates in a stable manner. Based on evaluating the time-derivative of the chosen Lyapunov function, we obtain the switching command that makes the system operate stably in each sampling cycle. In this paper, the proposed technique is applied on a boost converter. The simulation and as well experimental results validate the proposed control.

In the near future, the electrical vehicles will replace the traditional vehicles to get pollution free environment. Today, the electrical vehicles attract the interest of many researchers. In the recent years, the technology Wireless Power Transfer (WPT) was emerged and has a potential application. WPT is the technology using the magnetic resonance to transfer the electrical power without a direct connection. The WPT adopts the same basic theory which is based on the inductive power transfer employed in the conventional transformer. WPT can be applied to the electric vehicle (EV) for both charging system: stationary and dynamic chargers. This global system can integrate the photovoltaic systems in the charging stations which are built for the electric vehicles and the supervision base. The communication has been set up through a wireless network. An 8-kW prototype to charge 120 V battery was proposed to verify the theoretical analysis. The overall system efficiency is ∼ 93%. The charging system can get rid of the effects of the load, to obtain a reliable operation. The effectiveness of the proposed WPT is theoretically analyzed and validated by the simulations.

International audience; It is well known that the interaction between cascaded individually designed power conversion systems can cause instability. To overcome this issue, a Hamiltonian energy control scheme is proposed, which is based on passivity control theory and port-controlled Hamiltonian framework. A complementary PI adjustment term is also included in the control algorithm to eliminate the steady-state output voltage error caused by the parameter uncertainty. The proposed control approach is applied to three different cascade structures. First, the cascade structure between dc/dc converters is considered, and the detailed controller design is given. Second, the cascade connection of a single converter and its LC filter is studied. By placing the LC filter into the Hamiltonian model of the controlled converter system, the dynamic and potential instability caused by the filter can be adjusted. Finally, the cascade structure between subsystems including filters and converters, which are common in microgrids, is studied. By using the Hamiltonian function (storage function) as the Lyapunov function candidate, the large-signal stability of each controlled converter system is proved. When the cascade structure contains multiple controlled converter systems, the stability of the entire cascaded system is guaranteed by the superposition of multiple Lyapunov functions. A 3.5 kW 220-270-350 V test bench is built in the laboratory to demonstrate the application of the proposed control approach to these three cascade structures.

In more electrical aircraft, the embedded electrical network is handling more and more vital functions, being more and more strained as well. Attenuation of switching harmonics is a key step in the network reliability, thus filtering elements play a central role. To keep the weight of the embedded network reasonable, weakly damped high-order filters shall be preferred. Flatness-based control (FBC) can offer both high bandwidth regulation and large signal stability proof. This make FBC a good candidate to handle the inherent oscillating behavior of aforementioned filters. However, this control strategy can be tricky to implement, especially with high order systems. Moreover, FBC is more sensor demanding than classic PI-based control. This paper address these two drawbacks. First, a novel trajectory planning for high order systems is proposed. This method does not require multiple derivations. Then the input sensors are removed thanks to a parameters estimator. Feasibility and performances are verified with experimental results. Performances comparison with cascaded-loop topologies are given in final section to prove the relevance of the proposed control strategy.

This paper presents an investigation about commandability of a modular DC-DC converter topology. In this studied system, each converter module is based on a three-level DC-DC converter. The operation zones of this converter through commandability, have already studied. Here, a method for increasing of these zones is proposed. The simulation and experimental results corresponding to the theoretical analysis are provided to validate the proposed method.

Robust property of the controlled system is required for all applications. In this paper, the controlled method based on flatness properties is proposed. Due to its properties, high dynamical performances can be achieved thanks to a one-loop control architecture. An open-loop control can be used if the system being controlled is well known. In practice, an exact model is hard to develop. Therefore, online-estimators are applied to estimate the modeling error and make a more realistic model. In this way, open-loop control can be used. The contribution of this work is that the high bandwidth controlled system can be operated under either closed-loop or open-loop control and those with a reduced number of sensors. Simulation and experimental results are given to validate the proposed control method.

Hybridization systems working with electric generators and energy storage devices lead to optimal technologies for recent power sources. They are becoming more popular due to their advantages such as high efficiency, saved energy and low pollution. There are many types of architecture of hybridization. This article proposes a novel converter structure for a hybrid fuel cell/supercapacitor application that the fuel cell is hybridized with a bank of supercapacitors. Its benefits include high efficiency and maximum use of supercapacitor energy. The mathematical model is developed. The operation and modeling of the converter are presented. Closed-loop controls by using an indirect-sliding mode technique for the inner current loop and the energy control in the outer loop including a disturbance estimator are provided. Finally, simulation and experimental results obtained from the 150 W testbench are given to validate the proposed converter and system. The obtained results have shown that the proposed converter structure offers the right candidate for a hybridization fuel cell/supercapacitor power source.

Snow avalanches are an important natural hazard for backcountry skiers and alpinists in the Presidential Range (New Hampshire, United States). Over the past 20 years, over 72 people were involved in avalanche accidents. Direct-action avalanches resulting from recent snowfall dominate the avalanche regime of this region. Given this peculiarity, avalanche activity should be influenced by the intensity and duration of snowfalls. This study compares logistic regressions (LR) and a novel approach based on snowfall intensity–duration (ID) thresholds to analyse the weather patterns favourable to the triggering of snow avalanches. LR models suggest that 72-h solid precipitation, 24-h liquid precipitation, 72-h average daily maximum temperature and 72-h average winds peed are the best predictors of avalanche activity. The accuracy of the snowfall ID threshold to predict snow avalanches was similar to the accuracy of rainfall ID thresholds to identify landslide activity. However, a Monte Carlo cross-validation procedure suggests that the LR model is more accurate and more robust in predicting avalanche activity, since they allow the inclusion of more meteorological predictors. Finally, we discuss the relevance of this novel approach and the need for replicate studies in similar, direct-action avalanche-dominated contexts.

The lifetime and cost are two bottlenecks in the widespread use of fuel cells. Increasing the lifetime of the fuel cell can also counteract the cost justification bottleneck. However, this depends on the method of extending the life of the fuel cell. The durability of Polymer Electrolyte Membrane Fuel Cells (PEMFCs) can be improved using a management system. This management system must control the operating condition of cells or cell groups in such a way that the electrochemical and fluidic instabilities can be avoided to improve the lifetime of a stack. Developing this Fuel Cell Management System (FCMS) is challenging due to the coupling between cells inside a stack. In this paper, an FCMS is proposed. It can detect the instability of cell groups and change their reference power based on the detected instabilities. Since a mathematical model has a high ability to describe the phenomena occurring in a fuel cell, this paper uses a model to describe its operating conditions. The reference power of the cell groups can be changed using a developed power electronics structure. The last piece of the FCMS puzzle is to develop a management strategy. This strategy is developed in this paper. Eventually, the proposed system is evaluated experimentally. The experimental results validate the effectiveness of the proposed system.

International audience; This paper describes a method to control a dc-dc switching power converter with an LC input filter working under continuous conduction mode. It is known that the interaction between the low-pass filter and the tightly controlled switching converter occurs, and it might lead to an instability operation. The idea of this method relies on the Lyapunov stability criterion. The switching command of this control is defined by the manner of pre-evaluating the stability of the controlled system. All state variables are controlled in the same time. Therefore, the responses of this controlled system are fast while guaranteeing a stable operation. The proposed control is applied to a boost converter to demonstrate the implementation and its performance. The simulation and experimental results validate the proposed control approach.

International audience; Power loads are often modeled as constant power loads (CPLs) for stability analysis. However, this model may be too strict, and practical power loads are not ideal CPLs. In this paper, a discrete-time modeling is applied to the model of a power load of a dc system that is composed of a source converter, an LC filter, and the power load. A stabilizer is then added to the command scheme of the source converter in order to increase the maximum stable power of the system. The model also takes into account the dynamics of the load. Simulation and experimental results are given to validate the proposed model and to demonstrate the effectiveness of the proposed stabilizer, tuning of the stabilizer parameter, and the load current controller gain.

The lifetime of a fuel cell stack can be increased by controlling the cells separately. In such a topology, it is imperative to use a high voltage conversion ratio. The isolated step-up DC-DC converters can be a good solution but the efficiency is the major challenge. Connecting the output capacitors of classical converters like boost converters can cope with the problem of efficiency. However, the inequality of injected powers by different cells originated from the commands of the energy management system can lead to reducing the corresponding capacitor voltage. If the output capacitor voltage became lower than the corresponding converter input voltage, its controllability would be lost. An equalizer system that can send energy from the series connection to lower voltage cells is proposed in this paper to ensure the controllability of the boost converters in such a connection. The simulation and experimental results confirm the validity of the proposed equalizer.

This paper presents a new modular DC-DC converter topology. As modular topology, the converter can be used for several energy sources. Each converter module is based on a three-level DC-DC converter, which contains two output capacitors. The first module shares the second capacitor in common with the first capacitor of the next module. In this way, N-module can be utilized for N-energy source. The output capacitor voltages are balanced thanks to the proposed topology and the controller. The controller is based on the indirect-sliding mode controller where the input current of each energy source and the output voltage balancing are taken into account. Simulation and experimental results are provided to validate the topology.

Managing the energy is one of the most important issues for the efficiency of vehicular applications using hybrid electric power systems. This paper deals with an analysis of an energy management for hybrid power system, which consists of fuel cell, ultra-capacitor and battery and dedicated to electrical vehicles. Thus, an energy management method is applied in order to split the energy flow between the three used sources. This strategy is based on a combination of three control methods; a fuzzy logic control, a flatness control and rule-based algorithm. For the fuzzy logic, the main idea is inspired from rule-based algorithms except that it is more flexible and less aggressive. The second technic is an innovative control using the flatness property for a Fuel cell/ supercapacitor/ Battery hybrid power system. For the rules based algorithm, it uses a supercapacitor state-of-charge control principle. Then, an experimental validation is done for the energy management method to show the efficiency of the proposed control strategy in term of the well share of the energy between sources to satisfy the load demand. A dSpace real-time card is used for management algorithm implementation and data acquisition. The obtained experimental results prove the efficiency and the validity of the proposed supervisor.