This article proposes a method to optimize the design of a small fixed-voltage wind energy conversion system (WECS).The system is composed of commercially available elements which are: a small horizontal axe wind turbine, a onestage gearbox, a permanent magnet synchronous generator, a diode bridge and a battery bank.As there are no controlled devices on the system, the design must be carefully done to find the configuration that maximizes both, the system utilization and the system's output power.Using the mechanical and the electrical power equations, an optimization problem is proposed.This problem is aimed to find the optimal combination of the gearbox ratio and the battery voltage in order to extract the maximum amount of energy form the WECS.The mechanical power is modelled using a new proposed power coefficient function approximation.The constrained optimization problem is then solved by a MATHEMATICA© genetic algorithm based routine.Results are shown and discussed.

High-temperature superconducting coils are achieving technological maturity to be integrated into medium and high-voltage direct current applications. We propose to replace the conventional air-core dry-type arm coils of a modular multilevel converter with high-temperature superconducting coils. The goal is to reduce the the size and weight of arm coils, reduce losses under normal operation and limit the current under fault conditions. To demonstrate the feasibility of this proposition, we integrate air-core superconducting pancake coils in the arms of a single-phase modular multilevel converter prototype. The pancake coils were wound with BSCCO tapes. In this article, we detail the construction of the cryo-MMC and report the first experimental results.

In this article, we study the integration of high-temperature superconducting arm coils in a mod-ular multilevel converter (Cryo-MMC). With this integration, the fault current can be greatly reduced by the increased resistance of the superconducting arm coils during fault condition. We simulate and compare the performance of the cryo-MMC and a conventional MMC under a DC-side pole-to-pole fault. The simulation results show that the Cryo-MMC reduces the DC-side surge current by 57%, the peak arm currents by 65%, and the peak AC-current by 73.7% during the simulated fault. We also report the construction of the first cryo-MMC prototype that will experimentally validate the integration of superconducting arm coils into a single-phase 6-level MMC.

In this article, we compare the detailed switching (DS) model of the modular multilevel converter (MMC) with the arm average model (AA), the state-space time-invariant (SSTI) model, and the harmonic state-space (HSS) model. We consider a five sub-modules (SM) and a 50 SM application. We evaluate their performance in terms of accuracy on the representation of dynamics and simulation speed. The results show that the AA can be 700 times faster than the DS model, while the SSTI and the HSS can be more than 7000 times faster than the DS model. The highest relative deviation between models is kept under 8%.

This paper presents a control philosophy for multiterminal DC grids, which are embedded in the main AC grid. DC transmission lines maintain higher power flow at longer distances compared with AC lines. The voltage losses are also much lower. DC power transmission is good option for Russian north. Arctic seashore regions of Russia don't have well developed electrical infrastructure therefore power line lengths are significant there. Considering above it is possible to use DC grids for supply mining enterprises in Arctic regions (offshore drilling platforms for example). Three different control layers are presented in an hierarchical way: local, primary and secondary. This whole control strategy is verified in a scaled three-nodes DC grid. In one of these nodes, a modular multilevel converter (MMC) is implemented (five sub-modules per arm). A novel model-based optimization method to control AC and circulating currents is discussed. In the remaining nodes, three-level voltage source converters (VSC) are installed. For their local controllers, a new variant for classical PI controllers are used, which allow to adapt the values of the PI parameters with respect to the measured variables. Concerning the primary control, droop control technique has been chosen. Regarding secondary level, a new power flow technique is suggested. Unbalance conditions are also verified in order to show the robustness of the whole control strategy.

A constrained optimization problem based on the Lagrange multipliers method is formulated to derive the circulating current references of modular multilevel converters (MMCs) directly in abc coordinates. The resulting analytic expressions for calculating the circulating current reference signals are designed to eliminate oscillations in the dc-side power flow, independently of the ac-side operation of the MMC. As a result of the constrained optimization, the circulating currents are shaped to optimally utilize the degrees of freedom provided by the internal energy buffering capacity of the MMC, to effectively decouple the ac-grid conditions from the dc bus. This property of the proposed control method makes it especially suitable for preventing oscillations due to unbalanced ac-grid voltage conditions from propagating into multiterminal high-voltage dc systems. It is shown that the power flow at the dc-side of the MMC will he most effectively decoupled from ac-side transients if the desired steady-state power flow is imposed by acting directly on the circulating current references instead of by acting on the ac-side current references. The operation of an MMC controlled by the proposed approach is demonstrated by simulation studies, verifying the ability to keep the de power flow free of second harmonic oscillations, independently of the power control objectives applied for calculating the ac-side current references of the converter.

In this article we discuss the PQ diagrams for the modular multilevel converter. Firstly, we compare two models associated with PQ diagram construction: the conventional model and the steady-state time-invariant model. We show that the former model is less accurate than the latter model, since it is based on various hypotheses such as a zero arm resistance and an ideal modulated voltage behavior. Secondly, we study the impact of the arm resistance and arm inductance on the operating area of the converter using the steady-state time-invariant model. We show that the arm resistance is responsible for the asymmetry of the operating area leading to different maximal power transfers in the two directions. Further, we show that a reduction of the inductance expands the operating area, potentially leading to a better exploitation of the converter.

Cet article etudie l'influence du couplage des bobines d'un convertisseur modulaire multiniveaux monophase sur son fonctionnement en regime permanent. En particulier, l'effet du couplage sur le courant de circulation est examine en details pour differents coefficients de couplage. L'article presente brievement le modele mathematique de ce convertisseur. Il donne des informations sur la conception du convertisseur et explique le controle utilise. Finalement, il presente les resultats de simulation et les resultats experimentaux.

In this paper, a multiphysics model is proposed for a multi-V-shape interior permanent magnet motor with concentrated winding. This paper develops a nonlinear magnetic model that computes the flux density in the motor. The analytical model includes several novel aspects: it takes into account the local saturation near the iron bridges, it proposes a method for modeling the concentrated tooth winding, and it calculates the slot tangential leakage flux and includes it in the flux linkage calculation. The magnetic model is coupled with an electrical model that computes the power factor and the voltage at the motor terminals. A loss model is developed in order to calculate the copper and the iron losses. They are used as inputs to a nodal thermal model that introduces a thermal circuit for concentrated end-winding and computes the temperature of the motor. A mechanical model is developed. It evaluates the mechanical constraints encountered by the structure. The models are verified using finite element computations and numerical calculations performed with dedicated software. Besides, the coupled analytical model is experimentally validated using a prototype motor. Finally, two multiphysics bi-objective optimizations are carried out in order to design the motor for high-torque and low-speed application.

This paper presents a noval 18 poles /16 slots Axial Flux Permanent Magnet-Assisted Synchronous Reluctance Motor (AF-PMASynRM) with non-overlapping concentrated winding. At first, the torque ripple and iron losses are analyzed using 3D Finite Element Analysis (3D-FEA). Then, a comparison between 3D-FEA and 2D-FEA based on flux and iron losses is established. In this paper, we propose to design the motor for high torque low speed application using a multiobjective optimization. In this kind of iterative procedure, the use of Finite Element is generally time consuming. Thus, we propose a 2D analytical saturated model that considers the local saturation near the iron bridges and the slot tangential leakage flux. The magnetic model is coupled with an electrical model that computes the power factor and the voltage at the motor terminals. A loss model is also developed to calculate the copper and the iron losses. The proposed analytical model is 5 times faster than the 2D- FEA. The optimal axial structure is compared to a previously optimized radial motor in order to evaluate the design benefits of axial flux machines.

The influence of the coupling of the arm inductors of a modular multilevel converter has been investigated through transient simulations. In particular, positive, negative and zero coupling coefficient were considered for both steady-state and transient operating conditions. The effect of the coupling on the transient response, the capacitor voltage ripple, the circulating current, the DC short-circuit current and the switch power losses has been closely examined. The possibility to reduce either the circulating current or the DC short-circuit current has been demonstrated, opening the door to improved performances of modular multilevel converter with only minor modifications.

This paper presents a non-linear analytical model of a multi-V-shape Interior Permanent Magnet (IPM) motor with non-overlapping concentrated winding. The model relies on Maxwell equations to compute the flux density in the different parts of the motor. This article proposes a saturated analytical model of the stator and the rotor. The analytical model is used to calculate the average torque, the power factor and the voltage of the motor. It is compared to 2D Finite Element Analysis (FEA) and shows very good results. The developed model is 5 times faster than the FEA thus, it can be used in optimization procedures.

This paper deals with real-time implementations of a nonlinear and robust control applied on a marine turbine system. For the experimental validation which uses real data from Raz de Sein site (Brittany, France), the DC motor drives a wound rotor synchronous generator. A computer pilots this DC motor in order to stand in for the marine turbine behavior. Experimental results show the control successful of both outputs (terminal voltage and speed) making possible direct connection to electrical grid. In addition, we verify the robustness properties of the complete system under hard mechanical and electrical perturbations. Finally, a comparative study highlight the proposed control performances compared with conventional AVR-PSS which is one of the most widely adopted controller in industry for electrical grid stabilization.

This paper provides a solution for the control of multiterminal dc networks from the point of view of the network's transmission system operator, which includes local, primary, and secondary controllers. A new power flow technique is validated for this approach, which guarantees the stability and requires fewer calculations than the conventional techniques. This study also describes an optimal control strategy for intermittent (renewable) energy producers, where the controller periodically transmits information about its state to the system operator. Its main goal is to optimize economic profit for the producer. This last controller is implemented via model predictive control. The whole control strategy is validated in a scaled dc grid test-bench with four nodes. Real solar production (5 kW rated power), a storage system, as well as short-term weather and consumption forecasts are also included.

In this paper a coupled multi-physics model is proposed for a multi-V-shape Interior Permanent Magnet (IPM) motor with concentrated winding. A non-linear magnetic model computes the flux density in the stator and the rotor and delivers the torque, the internal power factor and the internal voltage. It is coupled with an electrical model that computes the power factor and the voltage at the motor terminals by considering the resistance and the leakage inductance. A loss model is developed in order to calculate the copper and the iron losses. They are used as inputs to a thermal model that computes the temperature of the motor. Finally, a multi-objective optimization is carried out in order to design the motor for a high torque and low speed application.

In this paper, a new approach to a nonlinear dq model is proposed for transient simulations of a salient-pole wound-rotor synchronous machine with dampers. Despite the nonlinearity between the flux linkage and the current, the comparison with finite element simulations shows that the new model is reliable for saturated transient state of the machine. This method allows to obtain far more accurate results than a classical nonlinear dq model, which assumes the equality between the mutual inductances. This model contains many improvements compared to most nonlinear dq models. The first one consists of considering each mutual inductance individually. The saturation of every inductance and its leakage part are evaluated separately. Furthermore, the calculation method of the mutual inductance between the stator circuits and the damper circuits is presented. Finally, the cross magnetization is introduced. This makes the proposed model closer to reality than most of traditional models.

In this paper, a nonlinear dq model is proposed for transient simulations of a salient-pole wound-rotor synchronous machine. Despite the nonlinearity between the flux linkage and the current, it is shown, thanks to a validation based on finite element simulations, that the new model is efficient for saturated transient state of the machine. This method allows obtaining more accurate results than classical linear dq model based on equivalent circuits or inductance matrices. This model is also more convenient than the linear dq model because it is more closely related to a physical model of the machine. Finally, it is far easier and faster to use than the finite element model in simulation and control.

This paper presents an electromagnetic analytical model for a Permanent Magnet Assisted Synchronous Reluctance Motor (PMA-SRM). The proposed model is based on the Maxwell equations: Ampere's theorem and the flux conservation law. The stator and rotor magnetic saturation are considered, as well as the effect of the magnetic bridges of the flux barriers. The goal is to compute the motor performances (average torque, voltage and power factor) for several current values and current angles. The analytical model results are compared to those from a Finite Element Model (FEM) and are subsequently validated by an experimental prototype.

This paper presents the analysis of a novel doubly salient structure with concentrated tooth winding and multi-V shape ferrite magnets. Permanent Magnet Synchronous Machines (PMSM) have been universally used with rare-earth magnets or with ferrite magnets and distributed winding. The proposed topology is presented as an improvement to PMSM for high torque and low-speed applications. It has low copper losses due to its short end-winding and benefits from a low cost by virtue of its lack of rare earth materials. This paper presents two slot/pole combinations: the 18/16 and the 12/10. A 2D Finite Element Analysis is used to investigate the average torque, the power factor and the torque ripple of each structure. It is shown that high performance is achieved for both motors. However, a parametric-analysis is performed on the 18/16 motor and shows that the saliency torque cannot be improved without reducing the torque and the power factor. As for the 12/10 motor, its main drawback is its high torque ripple. The torque ripple is reduced using two techniques; a rotor step skew and the use of an asymmetric pole shape. In this paper, a combination of both methods is proposed in order to reduce specific torque harmonics. Finally a comparison of the two motors is presented in order to determine which one is more suitable for the high torque and low speed application.

The purpose of this article is to describe the design of a limited stroke actuator and the corresponding prototype to drive a Low Pressure (LP) Exhaust Gas Recirculation (EGR) valve for use in Internal Combustion Engines (ICEs). The direct drive actuator topology is an axial flux machine with two air gaps in order to minimize the rotor inertia and a bipolar surface-mounted permanent magnet in order to respect an 80° angular stroke. Firstly, the actuator will be described and optimized under constraints of a 150 ms time response, a 0.363 N·m minimal torque on an angular range from 0° to 80° and prototyping constraints. Secondly, the finite element method (FEM) using the FLUX-3D® software (CEDRAT, Meylan, France) will be used to check the actuator performances with consideration of the nonlinear effect of the iron material. Thirdly, a prototype will be made and characterized to compare its measurement results with the analytical model and the FEM model results. With these electromechanical behavior measurements, a numerical model is created with Simulink® in order to simulate an EGR system with this direct drive actuator under all operating conditions. Last but not least, the energy consumption of this machine will be estimated to evaluate the efficiency of the proposed EGR electromechanical system.