Reactive power rescheduling with generator ranking for voltage stability improvement

Abstract

In a power system, voltage stability margin improvement can be done by regulating generators voltages, transformers tap settings and capacitors/reactors rated reactive powers (susceptances). In this paper, one of these methods which we name "reactive power rescheduling with generator ranking" is considered. In this method, using "ranking coefficients", the generators are divided into "important" and "less-important" ones and then, voltage stability margin is improved by increasing and decreasing reactive power generation at the important and less-important generators, respectively. These ranking coefficients are obtained using "modal analysis". In this paper, the method's performance for another type of ranking coefficients (which presents ranking coefficient for "all" generators) and using IEEE 30 bus test system is analyzed. The simulation results show that in this method, voltage stability margin is considerably improved and, also, the system active loss and the system operating cost are increased.

Impact of Wind Farms in Power Networks

“…One of the main issues is the Reactive Power Management which entails the requested operation and planning actions to be implemented in order to improve the voltage profile and the voltage stability in power networks (Raoufi & Kalantar, 2009). An efficient reactive power planning could be obtained by choosing an optimum location of var sources during the planning stage, whereas efficient reactive power dispatch could be achieved by scheduling an optimum regulation of the voltage set point at the generators connection point and at the var settings during the reactive power dispatch (Hugang, 2008).…”

“…Current power systems are working close to this operational stability limit, so distribution and transmission system operators (DSO and TSO) are required to wind energy to work as a conventional power plant and contribute to ancillary service such as reactive power control. Actual wind units are considered such as a non-dispatchable energy so, in many cases, they act as a PV or PQ nodes for load flows and reactive power studies (Raoufi & Kalantar, 2009). Some wind farm technologies, such as DFIG, have the ability to supply reactive power, so it could be possible to offer this reactive power capability to TSO and DSO in order to improve voltage stability of power network.…”

Voltage stability analysis based on multi - objective optimal reactive power dispatch under various contingency

“…In this paper, the voltage instability analysis study, which is one of the critical issues in electric power system [16][17], is also considered in a way to identify the critical buses to locate the SVC's devices and the critical lines for the contingency study purpose. For this purpose, three different stability indexes namely Fast Voltage Stability Index (FVSI) [18], Line stability index (Lmn 19] and Line Stability Factor(LPQ) [20] are used.…”

“…In this paper, three critical contingency cases are studied, these are: 1) Heavy load, 2) Lose a large Generator, 3) Lose a critical line. These cases are studied in a way to guarantee: i) The system stability after the increase of the power system load (voltage level, active and reactive power and load tap changer value are in the secure range), ii) The stability system maintainability after the outage of a large generator and a critical line, iii) a better location choice of the SVC's devices is for improving the network voltage level and stability.In this paper, the voltage instability analysis study, which is one of the critical issues in electric power system [16][17], is also considered in a way to identify the critical buses to locate the SVC's devices and the critical lines for the contingency study purpose. For this purpose, three different stability indexes namely Fast Voltage Stability Index (FVSI) [18], Line stability index (Lmn 19] and Line Stability Factor(LPQ) [20] are used.…”

Coordinated agent-based control for online voltage instability prevention

“…Compared to classical controls, such as Under-Voltage Load Shedding and LTCs tap blocking, the method performs better.A countermeasure which has less negative consequences is controlling reactive power compensating devices [17,18]. The method uses the Maximum Loadability Index to determine the amount of load relief necessary to restore stability.…”