Operation of double fed induction generators with unmodified low cost standard converters

Abstract

This paper presents how to operate a double fed induction generator (DFIG) with a rated power of approximately 30kW with unmodified low cost standard converters. The stator of the machine is directly connected to the grid and the rotor is fed with variable voltage and frequency from two standard low cost voltage source converters. Actually such machines are used in wind generators with a rated power of more than 500 kW with special build converters. In the presented solution the rotor of the DFIG is fed with two DC-Link connected standard voltage source converters. The original software is designed to calculate speed and phase of the rotor by receiving a speed signal from the rotor shaft. Therefore it is necessary to add two small application modules to modify the firmware externally to realize the calculation of slip frequency and phase in real time. The equivalent network parameters of the DFIG are determined by the converter itself by using an autotune function. With this parameters it is possible to develop an analytical model of the system to set up a closed loop active and reactive power control. The test system provides the ability to control both power types decoupled and with an approximately linear characteristic.

DFIG stator flux‐oriented control scheme execution for test facilities utilising commercial converters

“…While such designs generally enable real-time implementation of DFIG control utilising digital signal processor (DSP)-based controllers, this approach is challenging and complex for practical implementation. The use of commercial off-the-shelf power electronics equipment in DFIG research test facilities would be considerably more cost-effective, provide a significant advantage in simpler to manage switching signals in the real-time application, and also safer operation due to the availability of proprietary commercial protection [21,22]. Commercial converter systems application, however, poses considerable challenges, as they are not designed to allow direct access to switching signals control nor the application of nonstandard control routines, such as those required for DFIG operation.…”

“…The literature treating DFIG control utilising commercial offthe-shelf power electronics equipment is limited [19,21,22]. In [21,22], the RSC operates in open loop mode, since the standard power electronics equipment is generally not designed to facilitate straightforward application of DFIG vector control schemes.…”

“…The literature treating DFIG control utilising commercial offthe-shelf power electronics equipment is limited [19,21,22]. In [21,22], the RSC operates in open loop mode, since the standard power electronics equipment is generally not designed to facilitate straightforward application of DFIG vector control schemes. In [19], achieving practical SFOC DFIG control required additional computing and specialised software which imposed limitations in switching synchronisation and therefore a requirement for system de-rating, yielding a costly yet operationally constrained practical SFOC DFIG facility.…”

“…The magnitude, frequency, and position of the DFIG rotor current vector are calculated using an external real-time platform (dSPACE) and supplied to the RSC through a dedicated communications module (SM-Resolver module). In comparison with reported methods utilising off-the-shelf commercial converters [19,21,22], the proposed methodology enables effective implementation of SFOC: here, the RSC is operated in a conventional closed-loop servo control mode employing the external references provided by the dSPACE platform; the realtime platform is operated to execute a proposed routine providing the RSC real-time demand that is evaluated to ensure the implementation of rotor current control following the principles of SFOC. Furthermore, the GSC requires no modification and uses commercial off-the-shelf filters and protection components.…”

Simulador de Generador Eólico Doblemente Alimentado

“…Se observa que la tensión que debe proporcionar el convertidor es superior en el caso de estator abierto, que es el esquema habitual utilizado en la sincronización de aerogeneradores En otras máquinas de rotor bobinado con un requerimiento de tensión de rotor elevada se podría complicar la modulación para velocidades alejadas del sincronismo, por ejemplo, la conexión que habitualmente se produce a baja velocidad. En este sentido, Wegener [75] indica que es necesario conseguir una velocidad del 80% del velocidad de sincronismo para poder conectar en sincronismo estas máquinas.…”