Power System Apparatus Research Articles

高速移相器を付加したSMESによる電力系統の安定化制御

Recently, electric power demand is rapidly increasing and will be in the future. In the large power systems with complex configuration, undamped power swing with low frequency tends to occur. Therefore several stabilizing control schemes, e. g. a power system stabilizer (PSS), have been investigated so far. On the other hand, superconducting magnetic energy storage (SMES) has been expected as an effective apparatus in power systems since a SMES located in power systems is capable of leveling load demand, compensating for load changes, maintaining bus voltages and stablilizing power swings. The effectiveness of each function, however, depends upon the location of the SMES in the power system because the output power from the SMES is distributed according to the impedance ratio of the transmission line at the SMES location. Therefore, it is rather difficult for realize a SMES to server for two different purpose at the same time. This paper proposes a combination of SMES with a high speed phase shifter (HSPS). The HSPS, which consists of a phase shift transformer and a set of power converters, is capable of controlling the power flow of the transmission line by adjusting the phase angle of phase shift transformer. Therefore, it is expected that the combination of SMES and HSPS can realize a highly effective controller independent of its location. Numerical examples demonstrate that the proposed apparatus located far from a generator in a long distance bulk power transmission system is capable of stabilizing the power swing as effectively as the SMES located at the generator terminal. In addition, the effectiveness on the load change compensation as well as on the power system stabilization is confirmed numerically.

Digital simulation of flexible topology power electronic apparatus in power systems

The authors introduce special modifications to the basic Dommel algorithm to expedite simulation of systems including arbitrary configurations of individual power-electronic switching devices. The techniques have been implemented in a prototype transients simulation program. Two time-step sizes are used. Individual switching devices are represented according to simple characteristic curves. The modified algorithm includes iteration of a time-step when required to provide solutions on the curves. A technique is described for removing numerical oscillations of currents in capacitive loops and voltages at inductive nodes. Simulation results are presented for an example power electronic apparatus. >

Selection, Design, and Operation of Power Transformers on American Gas and Electric Company System

This paper discusses briefly the philosophy underlying power transformer practices on the American Gas and Electric Company system. It includes power transformers used in generating, transmission, and distribution stations. It does not include transformers generally used on distribution lines to serve residential customers, or special purpose transformers not directly associated with the transmission and distribution of power. The size and extent of the interconnected electric system on which the transformers are used are described, and the requirements of such a system discussed. Considerations entering into the selection of transformers, their general design requirements, operation, and maintenance, including principles of loading, flexibility of use, and spare transformer practices, are amplified in considerable detail. Over-all economics are emphasized. The power transformer is a most important piece of apparatus in modern electric power systems, being second only to the generator. It makes possible the widespread use of power. In larger sizes it is the largest, heaviest, and most costly piece of electric equipment, except for the generator. In total rated capacity it far outranks all other elements; hence it is worthy of the utmost attention in our search for construction and operating economies. Fortunately, the present-day power transformer is a most dependable piece of electric equipment. It has become so reliable that interruptions to service because of transformer failure are rare. Notwithstanding, however, there is great need for less costly transformers that are still more reliable and require less maintenance. These are the goals we seek.