Benoit Robyns

Design and Control Strategies of an Induction-Machine-Based Flywheel Energy Storage System Associated to a Variable-Speed Wind Generator

Flywheel energy storage systems (FESSs) improve the quality of the electric power delivered by wind generators, and help these generators contributing to the ancillary services. Presently, FESSs containing a flux-oriented controlled induction machine (IM) are mainly considered for this kind of application. The paper proposes the direct torque control (DTC) for an IM-based FESS associated to a variable-speed wind generator, and proves through simulation and experimental results that it could be a better alternative. This DTC application entails two specific aspects: 1) the IM must operate in the flux-weakening region, and 2) it must shift quickly and repeatedly between motoring and generating operation modes. DTC improvement for increasing the FESS efficiency, when it operates at small power values, is discussed. Some aspects concerning the flywheel design and the choice of the filter used in the FESS supervisor are also addressed.

Fuzzy Logic Supervisor-Based Primary Frequency Control Experiments of a Variable-Speed Wind Generator

In this paper, a primary frequency control strategy based on fuzzy logic, designed for variable-speed wind generators, is proposed and tested on a 2.2 kW test bench. The fuzzy logic supervisor ensures a regular primary reserve for a large range of wind speeds without any wind speed measurement. This supervisor controls simultaneously the generator torque and the pitch angle to keep the primary reserve; it determines in real time the generator power reference value. The fuzzy logic supervisor is compared to a simpler strategy, based only on the control of the generator torque. This classical strategy ensures a regular power reserve only when the wind generator operates at full load, and the generator power reference needs to be determined previously or by the network manager. A procedure for implementing a fuzzy logic supervisor in real time is proposed. The experiments indicate the regularity of the power reserve and the ability to contribute to frequency control.

Control based on fuzzy logic of a flywheel energy storage system associated with wind and diesel generators

The aim of this paper is to propose a control strategy of a flywheel energy storage system associated with a diesel generator and a fixed speed wind generator. To control the power exchanged between the flywheel energy storage system and the ac grid, a fuzzy logic based supervisor is proposed with the aim to minimize variations of the power generated by the diesel generator. The interesting performance of the proposed supervisor is shown with the help of simulations.

Modelling and simulation of an autonomous variable speed micro hydropower station

In this paper, the modelling of an autonomous variable speed micro hydropower station is presented. It is composed of a doubly fed induction generator linked mechanically and electrically to a permanent magnet synchronous machine which may recover or supply the slip power and which feeds the DFIG with its magnetizing reactive power leading to classical capacitor removing. The model lies on a classical approach, based on a Park representation, and on an energetic macroscopic representation (EMR). In its first part, this paper develops the modelling principles and underlines the complementarity of both approaches. The control strategy is then depicted in the case of passive loads supplying. Finally, some simulation results are showed and commented.

Comparison of technical features between a More Electric Aircraft and a Hybrid Electric Vehicle

With the more and more stringent energy crises and greenhouse effect, ldquomore electricrdquo transports are considered to be one of the solutions. The more electric aircraft and hybrid electric vehicle are the representation of ldquomore electricldquo transports. Some aspect of these two means of transport as installed capacity, role of electricity, electric sources, energy storage techniques and main electrical loads are compared in this paper. The future trend of ldquoelectricrdquo transport is also presented.

Experimental results on a variable-speed small hydro power station feeding isolated loads or connected to power grid

Following a series of articles presenting the modelling and simulation of an autonomous variable- speed hydropower station feeding an isolated load or connected to a power grid ([2], [3]), this paper is aiming to validate on the test bench the solutions proposed earlier. The studied system is composed of a doubly-fed induction generator (DFIG) linked mechanically and electrically (through back-to-back power electronic converters in the rotor circuit) to a permanent-magnet synchronous machine (PMSM) which may recover or supply the slip power. One of the advantages related to this system is that the PMSM and the power converters are designed for only about 25% of the plant nominal power.

A fuzzy-logic-based multimodel field orientation in an indirect FOC of an induction motor

Classical indirect field-oriented control is highly sensitive to uncertainties in the rotor resistance of the induction motor. This sensitivity can be reduced by combining two different methods to compute the stator electrical frequency. Fuzzy logic is used to combine both methods to obtain a compromise which reduces the flux control sensitivity to electrical parameter errors at each operating point. The design of the fuzzy logic block is based on a theoretical sensitivity analysis taking magnetic saturation into account, in simulations and in experiments. In this paper, the performance of the proposed control algorithm is theoretically and experimentally studied. The theoretical predictions are validated by experiments, by considering the stator current variations, to develop a given steady-state torque, induced by the imperfect flux control.

Vector Control of Induction Machines

From the analysis carried out in Chap. 2, we can observe that the operation of the induction machine and its mathematical model is rather complicated.

Stability analysis on the DC Power Distribution System of More Electric Aircraft

The local DC power distribution system (PDS) of a more electric aircraft is one of the cores of the electric power transmission. Generally, the PDS is made up of small power subsystems designed on their own stand-alone operation. But the interaction between the subsystems (sources and loads) induces some problems of stability. This paper compares the different stability behaviours of two load models: resistive load and constant power load. Some tests for the two load models at different operating points are carried out and the results are compared. The small signal theory and the impedance criterion GMPM (gain margin phase margin) are used to analyse the stability of each system. At conclusion, some statements are expressed to contribute to such electric interconnected systems stability.

Variable Speed Wind Generators Participation in Primary Frequency Control

To maintain a power reserve to contribute to the primary frequency control with variable speed wind generators, two control strategies are analysed in this paper: a torque control strategy and a fuzzy logic based multivariable control strategy. The first and most simple strategy allows to maintain a regular reserve only when the wind turbine generator works at full load and needs the determination of a power reference value a priori or by the network manager. The second control strategy allows to overcome these limits without any wind speed measurement; it determines in real time the generator power reference value to maintain a fixed minimum reserve. The main result of this paper is to shown that it is possible to maintain a regular reserve on a large range of the wind speed. This reserve is still more regular when considering a wind farm owing to the wind speed dispersion. The performance of the proposed primary frequency control strategies is shown with the help of simulations by considering a wind farm including three wind generators.