Double Stator Windings Research Articles

A Novel Experimental Method for Identifying the Flux Linkage Map of a High-Power Medium-Voltage Electrically Excited Synchronous Machine with Double Stator Winding

Accurate knowledge of the magnitude and position of the magnetic flux is essential for implementing field-oriented control (FOC) and achieving high-performance behaviour of AC drives. For estimating the flux in a wide range of speeds, so-called hybrid flux estimators, which are a combination of current-model and voltage-model based estimators, are usually used. Since the inductances are used as parameters in the current model, knowledge of the actual flux–current relationship, i.e., of the actual flux linkage map, is inevitable. In this paper, a novel experimental method for identifying the flux linkage map of an electrically excited synchronous machine (EESM) with double stator winding is proposed, which, unlike most existing experimental methods, does not require an additional machine to be used as a load. The flux is determined for different operating points to which the unloaded and sped-up machine is brought to by injecting d- and q-axis stator current components, whereby the current controllers are used to keep them constant for a certain operating point. The proposed method has been used to identify the flux linkage map of a medium-voltage EESM with double stator winding. A more than acceptable accuracy confirmed by comparison with three different analytical methods, together with the fact that it does not require a complex experimental setup, makes the proposed method suitable for the identification of a machine’s flux linkage map in an industrial environment.

Management of a Dual-Bus AC+DC Microgrid Based on a Wind Turbine with Double Stator Induction Generator

The topology and management of a sustainable dual-bus, AC and DC, microgrid designed to operate connected to a weak grid is presented. AC+DC hybrid microgrids are a robust and cost-competitive solution for poorly connected areas, as can be found in rural or island electrification. The versatile microgrid proposed in this work is developed around a wind turbine based on a particular induction generator with double stator winding and squirrel cage rotor (DWIG). This singular generator is especially suitable for a combined AC+DC coupled microgrid application. One of its stator windings is coupled to the DC bus via a controlled AC/DC converter. The other is directly connected to the AC bus, only during the periods of abundant wind resource. The DWIG is complemented with photovoltaic panels and a hybrid energy storage system, comprising flow batteries assisted by supercapacitors, which converge to the DC Bus. The DC bus exchanges power with the AC bus through an interlinking inverter. The article describes the topology and details the operation of its Supervisory Control system, which gives rise to the five operating modes of the proposed AC+DC DWIG based microgrid. Its performance under different generation conditions and load regimes is thoroughly assessed by simulation.

Fault-Tolerant Control of NPC Three-Level Inverters-Fed Double-Stator-Winding PMSM Drives Based on Vector Space Decomposition

The purpose of this paper is to study and propose the fault-tolerant control schemes for neutral-point-clamped (NPC) three-level inverters-fed permanent magnet synchronous motor drive with double stator windings. Both open-phase faults and open-switch faults are considered. The proposed schemes maintain the advantages of vector space decomposition (VSD) control for multiple-stator-winding drives, where the torque of multiple windings is controlled as a whole. Different optimization goals such as minimum copper loss and minimum current amplitude variance are achieved in the proposed fault-tolerant control for open-phase faults. Moreover, the impacts of open-switch faults on voltage vectors of the drive are analyzed, and the VSD-based remedial schemes are proposed for symmetric operation under open-switch faults by adjusting the switching modulation strategies. The current harmonics and dc-link midpoint voltage deviation are suppressed well with the proposed schemes. Both simulation and experimental results are given to verify the validity of the proposed modulation strategies and control schemes under faulty conditions.

POWER CONTROLLER FOR A WIND-TURBINE-DRIVEN TANDEM INDUCTION GENERATOR

ABSTRACT A controller for delivering either constant power or maximum power from a wind-turbine-driven grid connected induction generator with double stator windings, one fixed and the other able to be physically rotated, and a squirrel-cage rotor common to both stators is described. The load torque of the generator is controlled by varying the angular displacement between the two stators. The generator can feed power to the grid at variable speed and constant frequency and is termed a Tandem Induction Generator. Dynamic models for the wind energy conversion system are proposed for both controlled and uncontrolled operation to predict changes in shaft speed to shifts in wind speed using data pertaining to a commercial wind turbine. Results based on laboratory tests on a 1hp tandem machine driven by a dc motor demonstrating the feasibility of both controllers are presented. A steady state model of the tandem generator is also proposed and compared to measurements made on the test machine.

Analysis of a double-stator induction machine used for a variable-speed/constant-frequency small-scale hydro/wind electric power generator

Abstract A polyphase/single-phase rotary induction machine with double-stator windings, one fixed and the other able to be manually adjusted and positioned to match the mechanical and electrical power when used as a generator or a motor, is analysed and the advantages and disadvantages of such a hydro/wind generator are discussed. The rotor of the machine is normally in the form of a squirrel cage. The machine can feed power to the grid without an interface network. Optimal coupling to the prime mover when used as a generator or to the load when used as a motor is also derived from the analysis. This machine is also called an isosynchronous machine.