Stabilizing switching

A new idea of using switching to enhance the transient stability of a transmission network is outlined conceptually and illustrated by means of a simple example where the technical implications are given. A realistic system is used to show the benefit of stabilizing switching for a long distance transmission scheme. Depending on the type of fault, where the most severe is the three phase short circuit, an increase of the maximum transmissible power of about 10 percent can be achieved by the switching scheme. The additional benefits of this scheme include reduced fault currents and minimized effects of unsuccessful line reclosure. This scheme also provides a possibility for applying other control devices in stability control, e.g. surge arresters, current limiters and MOS controlled thyristors in the future     

Increased transmission capacity by forced symmetrization

Present planning procedures are based on single outages of three-phase circuits which do not take the actual fault pattern into account. The majority of faults are single-phase faults which is motivating the present approach to exploit the remaining conductors for power transmission. A shunt device (FACTS) is conceived which is able to generate a loading pattern at breaker locations with one or two phases open such that the network side always sees a symmetrical loading. The theoretical background is given and numerical examples illustrate the efficiency of the concept. The circuit affected by a fault may be modelled by a positive sequence impedance which can be inserted in ordinary power flow programs for security calculations     

Network Topology Optimization with Security Constraints

Strategic switching can be achieved by a current injection scheme which simulates the change in topology. The injected currents are applied to the terminals of the elements of a socalled base network corresponding to those actually switched. This requires that the base network must contain all elements in the "in" state. The injected currents to be used as a compensation in the commonly employed system matrices (Y, Z) for the real change in topology can be taken as control variables in an optimization procedure for the switching problem. With the aid of a method similar to linear programming (LP) objective functions such as line current, short circuit current or even losses can be formulated. By means of a switching sequence consisting of elementary switching operations the desired objective function will be brought to its optimum value.     

Switching as means of control in the power system

Many switching operations have been classified as unfavourable from the system point of view. However, an alternative view can also be taken. The effects of switching are described and ways in which these can be used as a means of control are outlined. An approach to modelling the switching operation is presented, including an explanation of the objective, constraints and search techniques involved. Several illustrative examples are presented.     

Speaker Modeling Using Emotional Speech for More Robust Speaker Identification

Journal of Communications Technology and Electronics - Automatic identity recognition in fast, reliable and non-intrusive way is one of the most challenging topics in digital world of today. A...     

Loss reduction by network switching

Systematic and fast switching for the purposes of reducing losses in power transmission networks is treated as an optimization problem whereby switching is to be understood in a general and comprehensive way. Injected currents applied to a base network are used to model the switching operation. These currents are used as variables in a linear programming (LP) problem formulation. The objective function, i.e. the change in losses, can be expressed by the injected currents, taking into account that all nodes are constrained by constant active powers except for the slack node. The change of power of the slack node is the change in losses, which is obtained by a two-step approximation. Each single optimal switching operation is obtained by an LP-like operation followed by a load-flow update. The interaction between LP and AC load-flow leads to a sequence of optimal switching operations whereby losses are reduced to a minimum subject to the given constraints     

Voltage collapse in power systems

The stages of a voltage collapse in a power system are described. Circuit and system techniques for analyzing voltage collapse that relate it to the changing number of solutions for the power-flow equations, due to slow changes in system parameters are presented. It is shown that to fully analyze voltage collapse for small- and large-disturbance cases, the essential dynamic mechanisms are considered. Several algorithms developed to detect how close a system is to voltage collapse are discussed. A voltage-collapse scenario based on the interaction among dynamic mechanisms is outlined     

Automatic generation control

Automatic generation control, one of the functions of a centralized system control centre, is discussed from the point of view of the steady-state loadflow between areas, the control algorithm, noninteractive control, optimum control and its impact on security enhancement, as well as the various interfaces to upper and lower level control functions. The importance of AGC in sparsely and highly interconnected systems is outlined, and present day problems are resolved.