A Robust Decoupling Estimator to Identify Electrical Parameters for Three-Phase Permanent Magnet Synchronous Motors

Abstract

As the high field strength neodymium-iron-boron (NdFeB) magnets become commercially available and affordable, the sinusoidal back electromagnetic force (emf) permanent magnet synchronous motors (PMSMs) are receiving increasing attention due to their high speed, high power density and high efficiency. These characteristics are very favourable for high performance applications, e.g., robotics, aerospace, and electric ship propulsion systems Rahman et al. (1996), Ooshima et al. (2004). PMSMs as traction motors are common in electric or hybrid road vehicles, but not yet widely used for rail vehicles. Although the traction PMSM has many advantages, just a few prototypes of vehicles were built and tested. The following two new prototypes of rail vehicles with traction PMSMs, which were presented at the InnoTrans fair in Berlin 2008, were the Alstom AGV high speed train and the Skoda Transportation low floor tram 15T ForCity. The greatest advantage of the PMSM is its low volume in contrast to other types of motors, which makes a direct drive of wheels possible. However, the traction drive with PMSM must meet special requirements typical for overhead-line-fed vehicles. The drives and especially their control should be robust to a wide range of overhead line voltage tolerance (typically from −30% to +20% ), voltage surges and input filter oscillations. These features may cause problems during flux weakening operation, which must be used for several reasons. The typical reason is to obtain constant power operation in a wide speed range and to reach nominal power during low speed (commonly 1/3 of the maximum speed). In the case of common traction motors such as asynchronous or DC motors, it is possible to reach the constant power region using flux weakening. This is also possible for traction PMSM, however, a problem with high back emf arises. In the report by Dolecek (2009), the usage of a flux weakening control strategy for PMSM as a prediction control structure is shown to improve the dynamic performance of traditional feedback control strategies. This is obtained in terms, for instance, of overshoot and rising time. It is known that, an accurate knowledge of the model and its parameters is necessary for realizing an effective prediction control. To achieve desired system performance, advanced control systems are usually required to provide fast and accurate response, quick disturbance recovery and parameter variations insensitivity Rahman et al. (2003). Acquiring accurate models for systems under investigation is usually the fundamental part in advanced control system designs. For instance, proper implementation of flux weakening control requires the knowledge of synchronous machine parameters. The most A Robust Decoupling Estimator to Identify Electrical Parameters for Three-Phase Permanent Magnet Synchronous Motors 16