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This paper analyzes fixed-speed induction generator modeling oriented to rotor speed stability studies. The single- and double-cage models are compared. The effects of symmetrical voltage sags on generator behavior are studied in detail. The rotor speed stability of the turbine is also examined and rotor speed recovery time is proposed as an indicator of system stability. Significant differences in the results obtained for both models were found, e.g., the double-cage model shows better speed and voltage stability. For some generator designs, the single-cage model can lead to erroneous stability predictions because manufacturer data of such designs can only be fulfilled with a double-cage model. The use of the latter to simulate fixed-speed wind turbines with this type of designs is therefore strongly recommended. The simulations were carried out using PSpice and PSCAD/EMTDC. [ABSTRACT FROM PUBLISHER]

The authors discuss the modelling of the squirrel-cage induction motor. The experimental measurements on motors of different rated power, 1–90 kW, clearly show that the single-cage model does not fit the torque–speed curve adequately. Consequently, when the speed varies in a wide range, only the double-cage model can fit the curve well with the squirrel-cage induction motor. The equivalence between the two most commonly used double-cage models in the literature is studied, and a method to find the equivalent parameters is developed. In addition, the induction motor modelling in the PSCAD/EMTDC and EMTP-RV simulation programs is examined, and the inaccuracies resulting from the use of manufacturer data are discussed. [ABSTRACT FROM AUTHOR]

The consequences of unsymmetrical voltage sags on the three-phase squirrel-cage induction motor behaviour are analysed; namely torque and current peaks, and speed loss. These effects depend on several variables such as sag duration, depth and sag type. The study takes into account that the voltage recovery instant can take only discrete values since fault clearing occurs in the natural current zeroes. The torque and current peaks have a periodical dependence on the sag duration, and a linear dependence on depth. The study of the influence of sag type on speed loss shows that sag types C and D have the same behaviour, and the same is true for sag types E, F and G. [ABSTRACT FROM AUTHOR]

A very simple method for determining squirrel-cage induction motor parameters is presented, and some problems in the determination of parameters with two methods proposed in IEEE Standard 112 are discussed and clarified. The double-cage model is used to describe the motor response for the entire operating range. Equivalent circuit parameters are calculated from data of three tests: no-load test, locked-rotor test and overload test. The method has the advantage of not requiring torque measurements. It is formulated as an iterative algorithm, and has been tested with 16 motors of different power ratings, showing very good convergence. The influence of measurement errors on the stability of the proposed method has been studied and its behaviour is very good [ABSTRACT FROM AUTHOR]