Voltage Stability Margin Of System Research Articles

Simulation of Voltage Stability and Alleviation Through Knowledge Based System

Modern power systems are large sized and rapidly growing. They require constant attention to monitor their performance. Attention is also required to ensure that the voltage stability margin of the power system is above a desired level. In order to achieve the objective, this study proposes a knowledge-based system. It computes using simple Fast De-Coupled Load Flow (FDLF), the state of a power system. Thereafter, the power system is subjected to an additional load at a certain power factor. If the power system collapses, then additional capacitor that needs to be switched on is computed by an iterative procedure. This is done for different load levels and tabulated. Thereafter, in the actual usage, based upon the computed Table, given any load one may determine the level of compensation required to avert voltage collapse.

Online voltage stability monitoring using var reserves

For many years, system operators have noticed that the VAr reserves of key generators can indicate the degree of controllability of key bus voltages in a system. This observation has led to the development of a few VAr reserve monitoring systems. In this paper, a rigorous investigation on the subject is conducted. Using the correlative relationship between generator VAr reserves and system voltage stability margins, a practical and systematic method for online voltage stability monitoring is proposed. The method has been thoroughly tested on two real-life power systems with promising results.

Coordinated secondary voltage control to eliminate voltage violations in power system contingencies

In order to achieve more efficient voltage regulation in a power system, coordinated secondary voltage control has been proposed, bringing in the extra benefit of enhancement of power system voltage stability margin. This paper investigates a new potential application of coordinated secondary voltage control by multiple FACTS voltage controllers in eliminating voltage violations in power system contingencies. The study is presented by the example New England ten-machine power system with two SVCs and two STATCOMs installed. The coordinated secondary voltage control is assigned to the SVCs and STATCOMs in order to eliminate voltage violations in system contingencies. In the paper, it is proposed that the secondary voltage control is implemented by a learning fuzzy logic controller. A key parameter of the controller is trained by P-type learning algorithm via offline simulation with the assistance of injection of artificial loads in controller's adjacent locations. A multiagent collaboration protocol, which is graphically represented as a finite-state machine, is proposed in the paper for the coordination among multiple SVCs and STATCOMs. As an agent, each SVC or STATCOM can provide multilocation coverage to eliminate voltage violations at its adjacent nodes in the power system. Agents can provide collaborative support to each other which is coordinated according to the proposed collaboration protocol.

On-line monitoring of maximum permissible loading of a power system within voltage stability limits

On-line determination of the maximum permissible loading of a power system is essential for operating the system with an adequate security margin. A very simple and straightforward method of determining the maximum permissible loading and voltage stability margin of a power system using information about the current operating point is proposed. The method simply requires some locally measurable quantities, such as bus voltage magnitude, and active and reactive components of load power. The measured data are carefully processed to estimate the maximum permissible loading and voltage stability margin of a system. The proposed method was vigorously tested on the IEEE 14- and 30-bus systems and the simulation results indicated that the method can correctly estimate the maximum permissible loading of the systems at the verge of voltage collapse.

Co-ordinated application of FACTS devices to enhance steady-state voltage stability

This paper examines the co-ordinated application of flexible ac transmission system (FACTS) technologies to extend system voltage stability margins. A systematic analysis and design method, based on the singular value/eigenvalue decomposition analysis of the load-flow Jacobian and the study of the controllability characteristics of an equivalent state model is used to study the voltage instability phenomenon as well as to assess the potential for small-signal voltage stability improvement by means of FACTS compensation. The method is of particular interest for the preliminary design of new system devices and the study of interactions among existing controllers. Results obtained using a practical system representative of the Central American interconnected network are presented, illustrating the application of FACTS technologies to extend voltage stability limit.

IEEE-PES Transmission and Distribution Conference and Exposition Call for Papers

Static network-related system voltage stability margin (VSM) depends on the availability of reactive power to support the transport of real power from sources to sinks. Based on this premise, the total VAr loss is minimized in the unified OPF framework considering real and reactive power controllers, and its effect on VSM is studied. Studies are conducted on a three-bus system, the IEEE 30-bus system, and a 191-bus Indian electric power system, and their results are reported.

Unified OPF method for maximizing voltage stability margin using successive fuzzy LP

This paper proposes a new unified OPF method that optimally schedules real and reactive power controllers. It minimizes the total generation cost and system transmission loss while maximizing the system voltage stability margin (VSM). VSM is maximized by maximizing a set of few least singular values of the load flow Jacobian. The method employs a successive fuzzy LP technique. Fuzzy models of the violated operating constraints are used. The use of fuzzy models allows scheduling of stressed power systems having violated operating constraints and gets their best enforcement. Sparse matrix computing techniques and constant network matrices are employed to realize the practical applicability. The proposed method is tested on modified IEEE 6- and 30-bus systems and on a 191-bus Indian electric system. Results serve to demonstrate the practical utility of the method.

Effect of generation rescheduling on voltage stability margin

One of the recent concerns that power utilities are facing is to maintain the required system voltage stability margin. This paper investigates the effect of generation rescheduling in enhancing the overall system voltage stability margin. A new formulation of generation rescheduling in view of minimization of the slack reactive power injection has been suggested. In addition, conventional optimal power flow (OPF) formulations, with their objectives being the minimization of total generation cost and minimization of total system transmission loss, and another formulation of generation rescheduling in view of the maximization of the minimum singular value of the power flow Jacobian have been studied. All the four formulations have a more realistic voltage dependent model of the generators and the synchronous condensers. The study has been carried out on three sample systems.