Power System Reliability Assessment and Enhancement for Different Contingency Conditions

Abstract

A power grid in a nation or continent integrates utilities by generating stations and loads in order to meet power requirements. When such colossal power systems are involved in power transfer, the voltage stability issue typically crops up. Voltage collapse may lead to blackouts. A blackout in a power system may affect one nation politically, socially, and economically. Blackouts can only be reduced by focusing on a detailed study of the steady state and dynamic operation of the power system. A possible solution may be to increase the power system infrastructure in order to endure these blackouts. Knowledge of the most vulnerable portion of the system, such as a line or bus, is essential for this endurance. Therefore, we need to distinguish the weak and less reliable buses or lines as soon as possible in the power system operation in order to take the necessary actions for smooth operation or to maintain steady-state equilibrium. The weak bus and lines may suffer outages, leading to cascading outages. As part of the analysis in this study, the ranking of contingencies was carried out using two evaluation approaches. The two approaches, namely the “Fast Voltage Stability Index” (FVSI) and a new “Reduced Fast Voltage Stability Index” (RFVSI) or the classical approach and the soft computing approach based on Fuzzy Logic (FL), have been used for different bus systems. The RFVSI is a reduced and faster version of FVSI. The outcomes of the two approaches were compared. It is found that the Fuzzy Logic (FL) approach computes the contingency ranking in less time compared to the classical approaches. In contrast, the classical approach based on the RFVSI method calculates contingencies more correctly, producing reliable results.
Two evolving contingency screening methods are described for faster system screening of important double-line contingencies. These methods analyze the complete double-line contingencies without considering all possible double-line outages, instead of taking only a few outages for the complete analysis, which reduces computational effort and time by using predefined power system sensitivity factors. The method described in this work is used in an Indian 62 Bus power system, and promising results are obtained. The work calculates the “Total Transfer Capability” (TTC) and the “Available Transfer Capability” (ATC) in different contingency conditions, such as line outages and generator outages. The most common continuous power flow method is utilized for TTC calculations. These calculations are useful for power wheeling in different power systems for power trading purposes in deregulated power systems.
Most of the power systems operate at their highest loading limits these days. Therefore, a small disturbance might bring the system to instability or oscillatory mode. In order to operate the system in a steady state, the system should be returned to the steady state in the event of a fault or any other disturbance. The Contingency in the power system is a severe problem, which may make the system insecure. There are several methods to mitigate the contingencies. However, it is most important to choose the point of action faster so that necessary action can be taken. The line outage contingencies, and the contingencies due to the outage of generators, affect the small signal stability of the system. The influence of generator outages on other generators has been investigated in this study using small-signal analysis. It is necessary to study the impact on the other generators present in the system so that essential control actions can be taken to reduce the generators' cascading outage. The damping of the low-frequency oscillations created due to the outages by different control actions, such as the application of “Power System Stabilizers” (PSSs), is described in detail.
In the event of contingencies such as generator outage or line outage conditions in a power system, the transmission lines in the network may be overloaded, leading the system to approach cascading outages. In generator outage conditions, the other generators in the system may fail to supply the load, which causes stability issues such as loss of synchronism in the system. The voltages of the buses of the system also decrease. In order to overcome these issues, a possible solution is to integrate renewable energy sources (RES) at the network's appropriate location for injecting active and reactive power into the network. With the RES in the proper places, the power transfer capability of the network could be improved along with the minimization of the line losses and the improvement of the voltage profiles of the buses. The optimization method involves the minimization of the "Reduced fast voltage stability index" and the minimization of "Transmission line losses".
All the methodologies are applied to the IEEE-14, IEEE-30, and practical Indian 62 Bus power systems.