Power Flow Modeling to Doubly-Fed Induction Generators (DFIGs) Under Power Regulation

With the constant k_opt model under the maximum power point tracking (MPPT) strategy, wind power fluctuation from the doubly-fed induction generators (DFIGs) increases the operational risk. With given wind speed, the constant k_opt model with variable slip yields impractical power output. The power loss and the active output of DFIGs are dependent on power flow of the system. The reference power may be dissatisfied by low wind speed, thus effectiveness of power regulation is unknown before solving power flow equations of the system and the DFIGs. In this paper, power flow model for DFIGs under regulation is newly proposed. Constraints of the power system and DFIGs are solved together to quantify the maximum output and verify if the power settings are satisfied. The DFIGs under effective regulation are seen as PQ buses. Power flow analysis is executed again to find the stator voltages. With the power outputs and the stator voltage, the effectively regulated DFIGs are finally solved. Modified flat start is proposed to improve the convergence. The proposed model reduces efficiency of the DFIGs but shows prospect of dispatching the wind power.