JPS6111831A - Dc transformation device - Google Patents

Abstract

PURPOSE:To improve a power factor/to obtain a waveform improving effect by forming a serial reactance having a reactance value corresponding to a commutation reactance for limiting a short current in capacitor equipment. CONSTITUTION:A DC transformation device for connecting an extra-high bus 1 to a load through a rectifier transformer 2 and a rectifier 3 is provided with the capacitor equipment 4 consisting of a capacitor 5 and a reactor 6. If it is defined that the capacity of the transformer is PT, the capacity of the capacitor is PC and the ratio of the reactance of the DC reactor in the capacitor to the commutation reactance is beta, the shown graph indicating the relation of alpha values to PC/PT values and using the beta as a parameter is obtained when the reactance ratio alpha of the capacitor equipment 4 is a quardrature axis and the capacity of the capacitor which can be set up is an ordinate axis. A large alpha value is selected when only the improvement of the power-factor is made an object, and a small alpha value is selected when the absorption of high frequency is targeted so that required improvement can be attained respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a direct current transformer, and more particularly to a direct current transformer that does not have a high distribution transformer, such as for electric railways.

Conventionally, in a DC substation having a high distribution transformer, a device for improving the power factor and waveform has been installed on the secondary side of the high distribution transformer. it is,
This is because it is the most economical and simple method since it can use general-purpose equipment for high pressure.

By the way, in a DC substation that does not have a high distribution transformer as described above, it is necessary to install a device for improving the power factor and waveform directly on the extra high voltage bus. 'The reason for this is that if a power factor or waveform improvement device is installed on the secondary side of the rectifier transformer, it will have an adverse effect on the rectifier. However, if a power factor or waveform improvement device is installed directly on the extra-high busbar as described above, the required capacitor capacity is generally small and all components must be made of extra-high-density equipment, so it must be carefully considered. There is a problem that it is uneconomical.

This invention has been made in view of the above, and its purpose is to
Even in the case of not having a high distribution transformer, it is possible to install it in parallel with a rectifier, and therefore it is an object of the present invention to provide an economical power factor and/or waveform improving device.

As a result of various studies regarding the above, the present inventor found that if the capacitor equipment is provided with a series reactance having a reactance value commensurate with the commutation reactance that limits the short-circuit current during the commutation period, which is the period of phase-to-phase short circuit, the rectifier No negative effects and strength.

The present inventors have discovered that the rate improvement and/or waveform improvement effect can be obtained, and have come to form the present invention.

That is, the DC transformer of the present invention is a DC transformer in which an extra-high busbar is connected to a load via a main rectifier circuit, in which a capacitor is connected in parallel to the rectifier circuit, and a capacitor is connected in series to the capacitor. This is characterized by the fact that a reactor is inserted into each reactor.

Next, specific embodiments of the DC transformer of the present invention will be described in detail with reference to the drawings.

First, Figure 1 shows the direct capacitor equipment of a DC transformer that does not have a high-voltage circuit. The capacitor equipment 4 includes a capacitor 5 and a reactor 6 connected to the capacitor 5 in series.

In the above-mentioned device, the capacitor installation capacity that can be installed is calculated as follows based on the commutation reactance. Note that the symbols in the formula are as follows.

PT:) Lance capacity (KVA) PC: Capacity of capacitor equipment (KVA) XT: Actual actance of main rectifier transformer (Ω) XL; Actance of series reactor of capacitor equipment (Ω) XC: Actance of capacitor equipment of capacitor equipment (Ω)
) α: Reactor ratio = XL/XC (unit method) β: X
L/XT (unit method) ZT:) Lance reactance (1 pL order method) From the above formula, it becomes as follows.

From the above formula, the following Table 1 is obtained.

Table 1 and Figure 2 are diagrams of Table 1 above, where β, which is the ratio of the reactance of the series reactor of the capacitor to the commutating actance, is taken as a parameter, and the capacitor equipment reactor cis ratio α is plotted on the horizontal axis. , shows the relationship between the α value and the PC/PTO value, with the vertical axis representing the installable capacitor capacity.

In the above diagram, when the only goal is to improve the power factor, it is more economical to use general-purpose capacitors and reactors, so the harmonic content of the capacitor equipment must be kept below the specified value. Therefore, for this purpose, a large α value may be selected.

On the other hand, if the goal is to absorb harmonics, a small α value may be selected. For example, for the 5th harmonic α=4
%, the harmonic content of the equipment becomes significantly large unless β=2nd place is considered.

In this case, PC/PT will be about 17%, and the harmonic content of the equipment will be about 100%. Therefore, special capacitors and reactors are required.

As described above, in the above-mentioned device, it is possible to improve the power factor and/or waveform when the above-mentioned formula (11) is satisfied.

Although one embodiment of the DC transformer of the present invention has been described above, the DC transformer of the present invention is not limited to the above embodiment, and can be implemented with various modifications within the scope of the purpose of the present invention. It's obvious that you can get it.

The DC transformer of this invention is configured as described above, and therefore, according to this invention, even if it does not have a high distribution transformer, it can be installed in parallel with a rectifier. Therefore, it is possible to provide an economical power factor and/or waveform improvement device.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a DC transformer according to the present invention, and FIG. 2 is a graph showing the relationship between α value and Pc/F1. 1... Special high bus bar, 2... Rectifier transformer, 3... Rectifier, 4... Capacitor equipment, 5... Capacitor,
6...Reactor. Patent applicant Japanese National Railway Mitsubishi Electric Co., Ltd. Shizuki Electric Manufacturing Co., Ltd. Figure 1 Figure 2

Claims (1)

[Claims] 1. In a DC substation consisting of an extra-high bus connected to a load via a main rectifier circuit, in parallel with the rectifier circuit,
A direct current transformer characterized by inserting a capacitor and a reactor connected in series to the capacitor.