Stand-alone Induction Generator Voltage Stability Study

The self-excited induction generator has the defect of not maintaining the terminal voltage stable at different loads. To understand the voltage changement at different parameters, bring forward reasonable voltage conpensation method and provide the theory foundation for machine design, the voltage stability of the self-excited induction generator is studied in this paper, including both aspects of steady state and transient state.The external parameters' effects on the terminal voltage are analyzed. Based on the steady-state equivalent circuit of a self-excited induction generator referred to the base frequency, the loop impedance is derived. Equating the loop impedance to zero is the prerequisite for predicting the steady-state performance of the induction generator. As a direct search optimization method, variable-shifting method is of the advantages in stability and feasibility over Newton-Raphson method is utilized to calculate the voltage under different loads, capacitances and rotor speeds. The agreement between the calculated results and the experimental results verifies the accuracy of the presented method.The approaches for the terminal capacitance, rotor speed and reactive compensation capacity calculation are presented to keep the terminal voltage at a constant value. With steady-state operation as a special case of transient operation, the transient model of the induction generator in the arbitrary reference frame is derived. Based on the transient equivalent and the optimization method, the steady state performances are analyzed, which unite the steady state analysis and transient state analysis of the induction generator and solve the difficulty of the constrained condition. The experimental results prove that the calculated results are correct.Voltage transient processes are studied to analyze the transient stability. The transient model underαβreference frame is built up and the system state equation is derived. By calculating the eigenvalues of the system and combing the system stable theory, the essence of voltage build-up and the effects of the parameters on the voltage build-up process are analyzed, so as to the voltage collapse and the voltage transient process as the parameters' change. At the same moment, the calculation methods of the critical parameters are put forward. The good agreement of the simulating results and the experimental results confirms the validity of the eigenvalue analysis method.