Yoshihiko Kataoka

Voltage stability limit of electric power systems with Generator reactive power constraints considered

This paper investigates the smoothness of the transfer limit surface, or the loadability surface, of power systems. The reactive power output constraints of generators are taken into consideration. A new methodology employed for the investigation is based on characterizing each maximum loading point by the state of the generators (PV or PQ). Then the transfer limit surface is investigated through careful observation of nose curves. In those special cases with only one constraint, the transfer limit surface is smooth. However, in the more general case of multiple constraints, the transfer limit surface is nonsmooth. These properties have been confirmed in a numerical example using a system with two constraints and three load parameters.

An approach for the regularization of a power flow solution around the maximum loading point

A method which is capable of greatly widening the range where the power flow solution is regular is presented. This is achieved by giving some modifications to the conventional power flow solution method and eliminating the singular point or shifting it to region where the voltage is lower than that of the maximum loading point. Then, the continuous execution of V-P curves including the maximum loading point is realized. The efficiency and effectiveness of the method were tested in a practical 598-node system are compared with the conventional method. >

Study of modeling method of distributed generators considering partial dropout for trunk transmission system

Simultaneous dropout of a large amount of distributed generators caused by a fault in a power line with voltage drop and/or phase change may worsen power stability of a trunk power system. A reduced model of distributed generators in secondary systems considering partial dropout is proposed for the stability analyses. To verify the reduced model, a detailed model and the proposed reduced model are compared under same conditions for a variety of load and fault conditions. For an example of practical applications, a relative comparison of power stability in IEE of Japan EAST 10 machine system model under fault ride through (FRT) requirements is demonstrated.