State modelling of self-excited induction generator for wind power applications



The increase in wind power production with self-excited induction generators (SEIGs) has led to new kinds of protection and stability problems. Suitable state models of a wind plant with SEIGs must accurately simulate balanced and unbalanced transient phenomena for adequate calibration and control of protection devices. However, the SEIG models currently available are unable to simulate the neutral current following unbalanced faults for forecasting the SEIG insulation and protection needed against some network stresses. In addition, the saturation model commonly used is not flexible when deriving a state model. This article presents an effective electromechanical state model for transient analysis of a saturated SEIG for wind power applications. A neutral connection through impedance is included for exact modelling of a Park wye-connected SEIG. Simple-shunt and short-shunt (series) configurations are explored. A comparative analysis of the effects of these two types of configuration on the steady state and transient performances of an SEIG is presented. Numerical and experimental data obtained with a 380V, 5·5kVA, 11·9A, 50Hz induction generator are presented to attest to the effectiveness of the proposed SEIG modelling framework. Among the results obtained, simulations show that the simple-shunt configuration produces poor voltage regulation, possible voltage collapse and inherent protection against short-circuit faults, while the short-shunt connection provides better voltage variation but needs to be well protected against short-circuit faults. Copyright © 2006 John Wiley & Sons, Ltd.