Practically power systems are having a large numbers of generators, transmission networks, and different loads. Positive sequence models are used for stability assessment. There are a lot of methods for analysis of the transient stability, but suitability to different kinds of the fault is the matter of concern.It is also important to note that the time frame in which transient instability occurs is usually in the range of 1 to 5 sec, so that simulation times need not be excessively long. Power system planner looked for better methods in terms of
i. Speed ii. Accuracy iii. Large memory iv. Reduced storage
2.2.1 Excitation Control
The method of generator excitation controls are one of the oldest and basic control for stability. In case of large disturbance thyristor exciters with high ceiling voltage are used to improve stability. Due to dependence of excitation control on local measurements total effectiveness may not be get for inter area stability problems in case where normal local measurements are not sufficient. To increase the effectiveness (sensitivity) of excitation control line drop compensation (Rubenstein and Walkley, 1957; Dehdashti et al., 1988) is one of the best method and used to improve coordination with SVC that normally controls transmission voltage with little droop.
2.2.2 UPFC Control
From the few years use of Flexible AC Transmission Systems (FACTS) controllers in power transmission applications is continuously increasing [61]. One of the FACTS controllers Unified Power Flow Controller (UPFC) is capable of to improve the transient stability. Hence we are expecting that its control applications will rise. UPFC model is having controllable voltage source added in series with the transmission line, plus two cu...
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... will be extended to multi machine system. In transient stability the period is such small of few milliseconds to tens of second so dynamics of the system can be represented approximately by the generator swing equation only, given as
Here Pm : mechanical input
Pe : electrical output power
Pb : power absorbed by the braking resistor respectively
D : rotor angular position:
M : generator inertia
Fig. 2.1 Line diagram of the system with Braking Resistor
By switching the resistor in and out of the circuit, the power absorbed P (t) can be varied between maximum and zero respectively. It is assumed that at one time either the braking resistor or the shunt reactor will be switched in. Switching the resistor in is a load injection, and the shunt reactor insertion amounts to reduction in power transferred (P ) by the machine.
On August 14th, 2003, a major blackout swept across portions of the northeastern United States and Canada. It was reported that a series of equipment outages in the Midwest led to uncontrolled cascading outages of power transmission lines and generators serving parts of the Northeast, Midwest and Canada. Automatic protective systems operated to open circuits and shut down power plants to prevent further spread of the outages. This is very similar to what happened in The Great Northeast Blackout of 1965. In both situations, the “grid system” shut down one generator in line at a time to protect a surge from the station before it.
Z. Q. Bo, A. T. Johns, and R. K. Aggarwal, “A novel fault locator based on the detection of fault generated high frequency transients,” in Proc. IEE Development in Power System Protection Conference, 434, pp. 197-200.
...ment and Control System for Increasing Transmission Capacity in Deregulated Energy Markets. Proc. 2002 Power Systems Computation Conference in Sevilla, (2002).
The PSS is an additional control system, which is often applied as a part of an excitation control system. The basic function of the PSS is to apply a signal to the excitation system, producing electrical torques to the rotor in phase with speed differences that damp out power oscillations. They perform within the generator’s excitation system to create a part of electrical torque, called damping torque, proportional to speed change. A CPSS can be modeled by a two stage (identical), lead-lag network which is represented by a gain K and two time constants T1 and T2. This network is connected with a washout circuit of a time constant Tw. The signal washout block acts as a high-pass filter with the time constant Tw that allows the signal associated with the oscillations in rotor speed to pass unchanged. Furthermore, it does not allow the steady state changes to modify the terminal voltages. The phase compensation blocks with time constants T1i – T4i supply the suitable phase-lead characteristics to compensate the phase lag between the input and the output signals. The commonly used structure of the PSS is shown in Fig
Depending on excitation, a synchronous generator can either generate or consume reactive power within its capacity. Cables generate reactive power due to high shunt capacitance, while overhead lines and transformers are reactive power consumers, which cause most of reactive power losses. Most loads, either by industry consumer or by private consumer, are inductive loads, thus they also absorb reactive power. The reactive power generated by synchronous generators is usually less than the demand of loads. Hence, the generation and requirement need to be equalized by capacitive compensation devices, such as capacitor banks, SVC and STATCOM
Gaussian elimination avoids the need of matrix inversion while solving the nodal equation of large power systems. Moreover it also leads to reduced order network equivalents. This is used to analyze power system with special focus on voltages at some selected buses. For this purpose selective numbering of s...
Older controlling techniques use 16 pulse or 8 pulse rectifiers which are now replaced by 24 pulse rectifiers, which makes it effective in power factor regulation.
For the prevantion of the electricity blackout we need to build smart power grid. A modernized electrical grid that uses analog or digital information and communications technology to gather and act on information, such as information about the behaviours of suppliers and consumers is known as a smart grid. This is used to improve the efficiency, reliability, economics, and sustainability of the production and distribution of electricity in an automated fashion[12]. The important aspects of smart grid is to electronic power conditioning and control of the production and distribution of
Usually different optimization methods are used to solve the TEP: genetic algorithm (GA), Tabu search (TS) and several heuristic and metaheuristic techniques. Those are called static scenarios. Dynamic scenarios are the one based on game theory which represents the behavior of different participants in the electricity market. Different games and models like cournot, Stackelberg, bargaining etc.. are recently used to obtain an optimal decision concerning TEP.
Power transformers are the most expensive and strategic components of electric power system [1]. It plays an important role by interconnecting in every stage of power transmission and distribution system [2]. The advantage of power transformers are mainly used for either step up or step down voltages according to the application requirement. The population of transformers in service is increasing because of the load growth, which is continuously subjected to electrical, mechanical, thermal and chemical stresses during its operation causing degradation. Practically, the power transformer is one of the high risk equipment in electric power system due to its harsh operating condition at various circumstances such as high temperature, emergency
When the wheel starts to rotate, the magnets attached with the wheel circumference also rotates. When these rotating magnets cross near the winding placed, there is a deflection in flux density around the windings. This deflection in flux induces an emf in the windings. With this fluctuating change in flux we get a constant generation of emf in the windings. This emf generated will be used for the several electricity purposes.
When a buildings load is higher than what the provider can supply the generator will compensate for this and provide additional load when required. This is most common if a building has been changed of use and the new facility requires more power than the provider can provide. For most of the day and weekend the existing power from the supply will be sufficient but there will be peak times when the demand for the building exceeds the supply. If peak lopping is not available when the demand exceed supply the main power supply will trip and mains power will fail. If this happens the user will have to contact the supplier and advise how much more power is required from the supplier and assess if the supplier can provide the extra power. For peak looping to be used the generator control panel will monitor the usage from the supplier. Once the demand is reaching the maximum available from the supplier the generator will compensate and start-up and synchronise with the mains power. The generator will then top up the power supply to meet the peak demand from the building and supply the extra load. By using the generator to supply the building with partial or full power in peak
Alternators used in central power stations also control the field current to regulate reactive power and to help stabilize the power system against the effects of momentary faults. Often there are three sets of stator windings, physically offset so that the rotating magnetic field produces a three phase current, displaced by
Sieniutycz and Spakovsky investigated the maximum power output of a multistage continuous endo-reversible Carnot system, they carried out the optimization study by introducing Hamiltonian function.
The stator is the stationary component while the rotor is the rotational component of the motor. Usually magnetic fields are created when an electric current is applied to a set of conductive wires wound together (Dixon, 2001). Magnetic fields can also be created using Permanent Magnets (PM). Electrical motors can also work as electrical generators (Correla, 1986). Electrical generators are devices capable of converting mechanical energy into electrical energy. An example would be a wind turbine which works as an electrical generator. It converts the mechanical energy of the rotating shaft caused by wind into electrical energy (Correla, 1986). The focus of this research will ...