Bernard Multon

Influence of magnetic losses on maximum power limits of synchronous permanent magnet drives in flux-weakening mode

The aim of this paper is to present the structure of a new synchronous machine with stator ferrite permanent magnets and a salient passive rotor (a robust and low-cost technology) which, when supplied with current by a three-phase bridge converter, produces continuous torque. This feature serves to place our machine on a par with the best synchronous machines available (e.g. high-energy rotor magnets with flux concentration). Furthermore, the electrical characteristics of this machine make it possible to apply the well-known flux weakening technique, which enhances the performance of the entire energy-conversion system. In theory, an operating area at constant power with unlimited speed can be obtained merely by taking into account the ohmic tension drops in the coils. Experimental results demonstrate that taking both magnetic losses and windage losses into account is necessary in order to identify the maximum mechanical output power characteristics.

Enhanced Aging Model for Supercapacitors Taking Into Account Power Cycling: Application to the Sizing of an Energy Storage System in a Direct Wave Energy Converter

This paper proposes an original model for supercapacitors that takes into account both calendar aging and cycling aging. A state variable is used to quantify the state of aging. This model is based on a series of recent experiments conducted in various research laboratories on the same technology (Maxwell Technology) and serves to represent the degradation of equivalent series resistance and capacitance. This model is particularly useful in an aging-aware life-cycle cost analysis. We show that an accurate aging model is critical to the design of an energy storage system that optimizes the economic life-cycle cost. Such an optimization is particularly applicable for smoothing in offshore systems such as direct wave energy converters, which require both cost reduction and high reliability. The influence of an aging model in the sizing process is investigated toward the end of this paper.

Preliminary sizing of a collaborative system: Photovoltaic power plant and electric vehicle fleet

Simultaneous upcoming of photovoltaic generation and electric vehicles increases constraints on electric power system. This paper explores the possible synergy between these players so as to jointly improve the production predictability while ensuring a low carbon mobility. First a context is defined for this collaboration. It consists in the association of a photovoltaic producer and some electric vehicles owners so as to both manage the EV recharge and meet a day-ahead production commitment. Several currently studied questions such as commitment strategies or optimal charging can be transposed into the proposed context called collaborative system. Here, we mainly focus on its sizing in terms of PV rated power and number of vehicles. A simplified model of the system is thus realised, including a day ahead commitment and an optimal vehicle charging planning, based on deterministic vehicle characteristics. First results show a strong influence of the sizing on the potential added value of vehicles in this association. Then, we assess the impact of day-ahead production forecast quality by comparing persistence forecast with some meteorological data. It appears that other things remaining equal, an imprecise forecast will increase the optimal number of vehicles that are supposed to get into the collaborative system. Finally, the robustness of the charging planning is investigated.

Sizing Optimization of Tubular Linear Induction Generator and Its Possible Application in High Acceleration Free-Piston Stirling Microcogeneration

We usually find applications of rotary induction generator, direct-drive tubular linear permanent-magnet generator, etc. for the mechanoelectrical conversion process within Stirling microcogenerator systems. This paper presents the design optimization investigation for a direct-drive tubular linear induction generator for a dual free-piston Stirling microcogenerator system. On the one hand, a high oscillating frequency and a relatively long pistons travel bring about a very high acceleration of the generators moving part, up to 1018 m/s 2. On the other hand, the tubular linear induction generator offers many interesting assets in this application: low weight mover, appearance of levitation force, no mechanical spring, low mechanical losses, no cogging force, easy manufacture, very low investment and maintenance cost, and so on. However, the tubular linear induction generator is sparsely used, because of its a priori relatively low energetic efficiency. This paper presents a sizing optimization approach for maximizing the performance and demonstrates that, with an astute arrangement of electrical devices, the tubular linear induction generator can constitute a well adapted solution for free-piston Stirling microcogenerator systems.

3D Analytical Model for a Tubular Linear Induction Generator in a Stirling cogeneration system

This article sets forth a 3D analytical model of a tubular linear induction generator. In the intended application, the slot and edge effects as well as induced current penetration phenomena within the solid mover cannot be overlooked. Moreover, generator optimization within the present context of cogeneration has necessitated a systemic strategy. Reliance upon an analytical modeling approach that incorporates the array of typically-neglected phenomena has proven essential to offering greater computational and analytical flexibility. This article will describe the electromagnetic model of the generator and draw comparisons with a finite element model, in addition to identifying the elements of equivalent electrical diagram and displaying results from the multi-objective optimization study performed using a genetic algorithm.

Comparison Between Centralized and Decentralized Storage Energy Management for Direct Wave Energy Converter Farm

This paper compares the sizing of distributed energy storage systems (ESS) with two control types in order to smooth a direct wave energy converter farm production, namely a centralized one that deals with the point of common coupling (PCC) power with aggregated information and a decentralized one that deals with each unit with only local information. The main objective is to compare the two controls on the basis of their life cycle cost. The ESS is necessary for grid integration in the case considered here due to the flicker constraint. The co-optimization strategies for both the sizing and the management of an ESS are based on a rule-based energy management and a sequential approach to deal with the power quality constraint. This management strategy has been optimized for each size in order to reduce aging speed while respecting the flicker criterion. The final design is expected to minimize total system cost. The centralized control clearly allowed smaller capacity. However, it may lead to an increase in cables losses compared with the decentralized case, although it is expected to be negligible under the conditions considered in this paper. The confirmation of this hypothesis will be the objective of future work.

Stochastic optimization of an Electric Vehicle Fleet Charging with Uncertain Photovoltaic Production

Simultaneous development of photovoltaic generation and electric vehicles strengthens the solicitations on the electric power system. This paper investigates the possible synergy between these players to jointly improve the production predictability while ensuring a low carbon mobility. It stands for a step towards a quantification of its economic and environmental fallout. First a context is described for a PV-EV collaboration. Then this is gathered into an optimization problem. Grid commitment constraints, battery aging and mobility needs are here considered from the environmental point of view of equivalent primary energy. Finally, a resolution method is presented which achieve an time-efficient optimization of the power flow for each vehicle, based on upstream computed charging policies. It relies on a stochastic modeling of both vehicles availability and forecast error of the PV production. The resolution framework is the stochastic dynamic programming, coupled with on-line minimization so as to avoid the curse of dimensionality. The proposed resolution enables to compute optimal power flow for each vehicle, even among large fleets. The emphasis is here set on a versatile resolution method which could take over many detailed objective functions.

Impact of the management strategy on the sizing of a collaborative system: Photovoltaic plant – electric vehicle fleet, under uncertainty

PURPOSE-To foster the grid integration of both electric vehicles (EV) and renewable generators, this paper investigates the possible synergies between these players so as to jointly improve the production predictability while ensuring a green mobility. It is here achieved by the mean of a grid commitment over the overall power produced by a collaborative system which here gathers a PV plant with an EV fleet. The scope of the present contribution is to investigate the conditions to make the most of such an association, mainly regarding to the management strategies and optimal sizing, taking into account forecast errors on PV production. METHODOLOGY-To evaluate the collaboration added value, several concerns are aggregated into a primary energy criterion: the commitment compliance, the power spillage, the vehicle charging, the user mobility and the battery aging. Variations of these costs are computed over a range of EV fleet size. Moreover, the influence of the charging strategy is specifically investigated throughout the comparison of three managements: a simple rule of thumb, a perfect knowledge deterministic case and a charging strategy computed by stochastic dynamic programming. The latter is based on an original modeling of the production forecast error. This methodology is carried out to assess the collaboration added value for two operators points of view: a virtual power plant (VPP) and a balance responsible party (BRP). FINDINGS-From the perspective of a BRP, the added value of PV-EV collaboration for the energy system has been evidenced in any situation even when the charging strategy is very simple. On the other hand, for the case of a VPP operator, the coupling between the optimal sizing and and the management strategy is highlighted. ORIGINALITY-A co-optimization of the sizing and the management of a PV-EV collaborative system is introduced and the influence of the management strategy on the collaboration added value has been investigated. This gave rise to the presentation and implementation of an original modeling tool of the PV production forecast error. Finally, to widen the scope of application, two different business models have been tackled and compared.

Optimization of a linear induction oscillatory machine in a stirling cogeneration system

The simultaneous production of heat and power at a small-scale is already a well known technique. Cogeneration is one of the main ways to bring about decentralized, embedded, localized and/or autonomous power production. However, it is still a challenge to design cogenerators to be below 10 kW as required for the smallest applications such as providing heat and power to a single house. This paper specifically presents an automated procedure to optimize the generator performances of a micro-cogenerator. The procedure uses a steady-state analytical model of the generator to determine the parameters of its dynamical model. Then, the micro-cogenerator dynamics are simulated to calculate two accurate objective functions that are minimized by a genetic algorithm.

A Switched Reluctance Motor Drive using Photovoltaic Transistors: Principle, Prototype, Experimental and Numerical Results

A solar-powered switch reluctance motor drive using photovoltaic transistors is presented. The expression photovoltaic transistor (PVT) is used to designate a conventional photovoltaic cell used as a light-controlled power transistor. To obtain a motor drive, a set of PVTs controls the current fed from an external DC power source to the motor phases. The control is achieved by modulating the sunlight hitting the PVTs using a shutter driven by the motor rotor. If the external DC source is a solar panel, the resulting system is able to convert light energy into mechanical energy, without the need of any brushes or other power electronics components. This system could be more affordable and reliable than conventional ones, and therefore is well suited for off-grid applications like water pumping. This article first discusses the operation of a photovoltaic transistor through the proposition and the validation of a model. Then, the operating principle of a PVT inverter is clarified. Finally, experimental and numerical results on the first PVT inverter-fed switched reluctance motor are reported. A prototype was built using a switched reluctance motor 6/4 and 12 PVTs. It was here connected to an external 12 V DC power source as a step before using a solar photovoltaic source. Results showed that the PVT inverter-fed switched reluctance motor was operating as expected and provided useful power.