Shanghai University, Shanghai 200072, China)

 Abstract: Aiming at solving the voltage instability problem of Ningbo power grid under extreme loads, the operation statuses including bus bar voltage and power factor of Ningbo power grid under peak load in summer and valley load in vocation were analyzed and the critical factors of voltage stability, e.g., reactive source outputs, transformer taps, parallel capacitors, were concluded. Then, a simulation approach based on BPA (Bonneville Power Administration) was proposed. Moreover, taking the situation under peak load in summer for example, the simulation results were compared with the real results to validate the proposed method. Finally, the solution to reactive problem of Ningbo power grid under extreme loads was provided. The experiment results indicate that the simulation results and the real results are basically consistent and the bus bar voltages under extreme loads are within a limit when adopting the provided solution which stands for the voltage stability.

 Key words: extreme load; voltage stability; reactive problem; bonneville power administration（BPA） simulation