Feeding Substations Research Articles

Analysis of Catenary Voltage of an AT-Fed AC HSR System

This paper represents an exact modeling for autotransformer (AT)-fed ac high-speed railroad (HSR) using constant current mode. AC HSR has rapidly changing single-phase load, and at a feeding substation, three-phase electric power is transformed to the paired directional single-phase electric power. As the train moves along a section of line between two adjacent ATs, analysis of the catenary voltage in AT-fed ac HSR system is a quite complicated work. Therefore, in order to solve this complicated system, this paper proposes a novel and efficient method with generalized equations for the catenary voltage of AT-fed ac HSR. The voltage profile through the entire railroad system can be solved regardless of the number and position of trains, feeding distance from substation, and normal or extension mode. In the case studies, the results of the proposed equation for the catenary voltage profile are compared with those of the simulation using PSCAD/EMTDC.

Power-Electronic Interface for a Supercapacitor-Based Energy-Storage Substation in DC-Transportation Networks

A Power-electronic interface for supercapacitive-storage based substation in DC-transportation networks is proposed, which allows to feed as a current-source in any voltage conditions of the line. The system has been designed as a com-Pensation-substation to be placed at weak points like end-of-line stations, and can replace supplementary feeding substations. A dedicated power-electronic converter with associated control system is proposed, for the stabilization of the voltage level at the point of coupling. Practical results are also presented, which have been recorded from a reduced scale prototype.

A Supercapacitor-Based Energy Storage Substation for Voltage Compensation in Weak Transportation Networks

A supercapacitive-storage-based substation for the compensation of resistive voltage drops in transportation networks is proposed. It allows to feed as a current source in any voltage conditions of the line. The system has been designed as a compensation substation to be placed at weak points like end-of-line stations, instead of additional feeding substations. A dedicated power-electronic converter with an associated control system for the stabilization of the voltage level at the point of coupling in case of strong perturbations is proposed. Practical results are also presented, which have been recorded from a reduced size prototype.

Peak power demand reduction under moving block signalling using an expert system

The concept of moving block signallings (MBS) has been adopted in a few mass transit railway systems. When a dense queue of trains begins to move from a complete stop, the trains can re-start in very close succession under MBS. The feeding substations nearby are likely to be overloaded and the service will inevitably be disturbed unless substations of higher power rating are used. By introducing starting time delays among the trains or limiting the trains' acceleration rate to a certain extent, the peak energy demand can be contained. However, delay is introduced and quality of service is degraded. An expert system approach is presented to provide a supervisory tool for the operators. As the knowledge base is vital for the quality of decisions to be made, the study focuses on its formulation with a balance between delay and peak power demand.

A static voltage fluctuation compensator for AC electric railway using self‐commutated inverters

AbstractIn this paper, the authors describe the basic configuration of an RPC (Railway Static Power Conditioner), its compensation principles and successful test results (using a small model of RPC).An ac electric railway is placed under a rapidly changing single‐phase load. To avoid a voltage fluctuation under single‐phase loads, electric power is received from a large source. At a feeding substation, three‐phase electric power is transformed into two kinds of directional single‐phase feeding electric power.The authors have already proposed a static voltage compensator for the ac electric railway, called “RPC.” The RPC links a pair of feeding circuits, using two self‐commutated inverters.At the substation, the RPC accommodates an active power in the directional pair of feeding circuits to balance three‐phase power, and possess a reactive power to regulate a three‐phase voltage fluctuation. At a sectioning post, it can compensate for voltage drop using reactive power. It can also act as an active filter to compensate for harmonics.The authors have made a small model (220 V, 20 kVA) of the RPC, and report on the test results obtained using this small model under various conditions. The results indicate that the RPC can accommodate single phase loads, such as transformers and thyristors, can handle an exciter rush current from a transformer, can compensate for harmonics, and so on.

Suppression of time-varying resonances in the power supply line of AC locomotives by inverter control

The harmonic currents generated by the line-side converter of an electric locomotive are injected into the overhead supply system. Although low in magnitude, they give rise to traveling waves that start propagating in both directions along the overhead line. The traveling waves are reflected at various electrical discontinuities along the line such as the feeding substations and other traction vehicles, the positions of which are time varying. This produces eigenresonances at multiple frequencies. High resonant currents may be generated that cause problems of electromagnetic interference with railway communication and signaling systems. It is demonstrated that the time-varying eigenresonances can be identified in real time. Methods of optimal adaptive inverter control are employed in order to avoid the excitation of the line resonances. >

Power Factor and Higher Harmonic Currents of the Electric Power System for a High-Power Three- Phase AC Electrified Automated Guideway Transit

In three-phase ac electrified automated guideway transit (AGT) systems, the car uses a thyristor phase control type controller. The controller has a low power factor, and it generates higher harmonic currents to the power line. Such AGT systems as the Osaka- Nanko Port Town line which opened in 1981, need much more electric power than conventional personal rapid transit systems. In such a case, the harmonic currents at the receiving point are necessary not to exceed the limits of the power company. A simulator has been developed to calculate electric power and higher harmonic currents in a multivehicle power feeding system. Simulations for the Osaka-Nanko Port Town AGT system show that the average power factor is less than 0.7 and harmonic currents exceed the limits with no countermeasures. After several simulations, we developed the power feeding system which uses a fifth higher harmonic filter of 250 kVA at all seven feeding substations, and seventh, eleventh, and thirteenth harmonic filters, which total 1.0 MVA, at the receiving substation.

Computer Simulation of Faulted URD Cables: Analysis and Results

A method for computing shield potentials of underground directly buried (URD) cable is presented. Earth potentials in the vicinity of the buried cable are also computed. The method utilizes a numerical solution of Laplace's equation to account for earth currents, and a modified nodal analysis method to account for conductor and shield currents as well as inductive coupling in the underground cable system. A computer program has been developed capable of analyzing long lengths of URD cable together with existing ground rods, faults, open neutrals, feeding substation and substation grounds. The system analyzed corresponds to practical URD cable distribution systems. Extensive simulation of various URD cable systems in various soil environment has been performed and the results have been tabulated in a two-volume EPRI report.