Integrated Coal Gasification Combined Cycle (IGCC) plants, one of newest of power generation plants, take advantage of the reasonable cost, small environmental impact and flexibility of staged construction. As such, IGCC plants are expected to play a major role in coal-utilizing power plants in the near future. The load-regulating capability of the IGCC plant was studied by the simulation method. A large-scale mathematical model for the oxygen-blown Texaco-type entrained-flow gasifier (coal slurry) combined cycle plant was developed to study the responses of the IGCC plant against ramp changes in load demand. From this study, the load regulating capability of the IGCC plant was proved to be superior to that of the conventional coal-fired thermal power plant.
The goal of reactive power (VAR) planning is to find the minimum cost installation plan of new reactive power sources so that the system voltage is maintained within an acceptable level. The consideration of multiple contingency states, together with the discrete nature of VAR facilities, creates a large-scale nonlinear mixed-integer programming (MIP) problem. To overcome the discrete nature of VAR facilities, an approximate method for MIP problem is employed, since the method is Linear Programming based and thus efficient for large-scale problems. To treat the multiple contingencies, a resource directive decomposition approach is used in the proposed algorithm. If the number of installed VAR sources is fixed, the overall problem can be decomposed into independent subproblems. Then subproblems are coordinated to give a VAR installation pattern in which installation cost becomes cheaper than before. The algorithm proposed is tested for a 135-node real size system and the results show the validity and effectiveness of the algorithm.
With tte development of electric power system, disconnecting switch and earthing switch have been requested switching capabilities of loop current, induction current and small current. Many measurements have been taken especially for large current breaking. This paper describes switching duties, switching phenomena, switching test results and guidance of breaking unit design for SF6 gas disconnecting swith and earthing switch.
Optimal control has been discussed for models, in general, obtained by linearizing power systems. However, it is known that the control has not been effective for large disturbances. Fuzzy control, in which the nonlinearity of a system can be considered, has been recently studied in many fields of engineering. In this paper, two types of combination controls by means of fuzzy and optimal controls are proposed. The first type is a control combining two optimal controls, which can be obtained from two linear models given by linearizing a power system, through fuzzy theory. For the second one, fuzzy control is fundamentally used and optimal control is applied to fuzzy control rules around the stable equilibrium point. It is shown that these combination controls are better to improve the transient stability for large dinturbances in power systems than fuzzy only or usual optimal control. These controls are applied to the stabilizing control problem for a multimachine power system taking into account AVR and GOV.
One of the failure related to gas-insulated switchgear is caused by the poor contact between conductors, causing breakdown between the contact and the wall of chamber, initiated with the small discharge due to the poor contact. In this paper, the modeled experimental apparatus for contact portion of the gas-insulated switchger assumed a rod-to-plane gap with small arc current. The influence of the arc current on the breakdown into the chamber was investigeted experimentally, and the breakdown mechanism between the contacts and the wall was studied. It was cleared that the breakdown voltage between the contact and the wall decreased by increasing the current, and the small arc current in the contact portion played an important role on the breakdown between the contact and the wall. The reduction ratio of the breakdown voltage increased with increasing gap length of the small gap. The breakdown voltage was different depend on the duration of the small arc current.
Considering the unanticipated increase in contact resistance in Gas Insulated Switchgear, an investigated result on the reduction of the breakdown voltage due to the arc is reported. At first, incompressible fluid analysis is applied to calculate profiles of fluid velocity, gas density, etc. In experiment, the arc is generated on the gas gap between a pair of conductors located in the center of the tank. The breakdown voltage between them and the disc electrode located above them is measured. Results are as follows. (1) The transit time of the hot gas from the condutors to the disc electrode is 235ms in calculation and 233ms in experiment, respectively. (2) The breakdown voltage between the conductors and the disc electrode is estimated by the gas density and the electric field strength at the surface of the conductors. Because the gas density, which is calculated by the fluid analysis, is lowest and the electric field strength, which is calculated by FEM, is largest. Consequently, it is proved that condition of these calculation is similar to that of the lowest breakdown voltage in experiment.
A cryogenic power cable is expected to be capable of carrying bulk power as a main transmission Sine in a future metropolitan electric power system. It is important to establish a strategy how to sustain power supply when such a highly densified power supply route trips from the network due to contingency. Our proposal here is that the bulk power transmitted by the cryogenic cable could be distributed into the parallel conventional transmission lines by suitable circuit breaker operations in the system. In this process, however, power flow routes are forced to be changed with a remarkable modification in the system configuration. In this paper, the power swings associated with the large power flow change following contingent faults are analyzed by means of a transient network analyzer. It is found out that the proposed system modification could be realized without any harmful power swing if the parameters in generators as well as in control devices have conventional magnitudes. It is also shown by simulations that margin to occurrence in unstable power swing is left enough even if the parameters rather deviate from the present magnitudes.
Numerous control methods based on modern control theory have been proposed to improve the load frequency control (LFC) characteristics of power systems. These control methods generally regard the load frequency control system as a linear system model. Furthermore, complicated mathematical equations have to be solved to determine control laws. However, realistic power systems are nonlinear, i. e., the nonlinearities of tie-lines connecting between the control areas and of generation rate constraints of power plants are existed. Consequently, it is considered that the design of controllers are difficult. In this paper, the application of fuzzy control to the load frequency control system is proposed to solve the problems stated above. The proposed control first, to satisfy the load frequency control requirements, estimates power demand variations of the control areas and uses them as the output set-point values of power plants, instead of using an integral-type controller. Next, to improve stability and optimality of the nonlinear load frequency control system using the above output set-point control method, the proportional-type fuzzy control considering a computation time-delay is implemented. Parameters of the proposed fuzzy controller are determined by minimizing the integral square of the area control error (ACE) to assure optimality of the system.
Suppression of electromagnetic noise at the distributor gap for the automotive ignition system are studied. Noise frequency spectrum electrode materials and configusations are presented on the same base of the breakdown conditions in order to compensate the large dependency of the breakdown voltage on the noise levels. A wide gap or a piled electrode which accompanies a dielectric material at the tip is useful for suppression of the noise levels. ZrO2-ZnO ceramic electrodes having different resistivity are tested and found to show very low noise levels. Breakdown voltage of the ceramic electrodes are low and more stable than other electrodes. But the noise levels of the ceramic electrodes are fair lower than that expected by the low breakdown voltages.