JPH0340077Y2 - - Google Patents

Description

[Detailed explanation of the idea] [Technical field of invention] The present invention relates to a power harmonic filter device.

[Technical background of the invention and its problems]

In recent years, the number of electrical devices using semiconductors such as thyristors has increased, and the harmonic current flowing out from these devices increases harmonics in power circuits, causing many harmonic disturbances. In order to absorb harmonics generated from these semiconductor application devices and suppress them from flowing into the power system, a harmonic filter device consisting of a capacitor, a reactor, a resistor, and the like is used.

A harmonic filter uses the resonance phenomenon of a reactor and a capacitor to reduce the impedance in a specific frequency range and allow harmonic current to flow in, and is made up of a combination of a reactor, a capacitor, and a resistor. A circuit configuration in which a reactor and a resistor are connected in parallel, and a capacitor is arranged in series with this is called a quadratic harmonic filter. As shown in Fig. 6, the conventional quadratic harmonic filter device is constructed by connecting a three-phase capacitor 1 in series to a circuit in which a three-phase reactor 2 and a three-phase resistor 3 are connected in parallel. Both the reactor 2 and the three-phase resistor 3 are connected in a star shape, and their neutral points are connected by a connecting wire 5.

Recently, in order to downsize electric power equipment, downsized equipment in which the connecting busbar of the equipment is constructed of an oil-filled pipe or a gas-insulated pipe has been adopted. In addition, if this configuration is adopted in the harmonic filter device, the three-phase capacitor 1, the three-phase reactor 2, and the three-phase resistor 3 will be connected by a connection bus, but in this type of device, When a steep surge enters the phase capacitor 1, the potential at the neutral point N of the three-phase reactor 2 and the three-phase resistor 3 increases, so special consideration must be given to the insulation on the neutral point side. For this reason, it is necessary to use materials with high dielectric strength for the neutral point bushing of each device and the connection bus bar on the neutral point side, which has the disadvantage that the insulation of the device and the connection bus bar are complicated.

[Purpose of invention]

The purpose of the present invention is to provide an inexpensive power harmonic filter device that simplifies the configuration of each device and connection busbar, and also reduces installation work and installation space.

[Summary of the idea]

The power harmonic filter device according to the present invention has a three-phase capacitor placed on the power supply side, and the three-phase reactor and resistor connected to this are connected in a star shape, but their neutral point is outside the device. This feature is characterized in that it is configured so that it is not derived.

[Example of idea]

The present invention will be described below with reference to an embodiment shown in FIG. The three-phase capacitor 1 has one end connected to the power supply side terminal 4.
The other terminal is used as a load-side terminal 5, and a three-phase reactor 2 and a three-phase resistor 3 are connected in parallel to this load-side terminal 5. The three-phase reactor 2 and three-phase resistor 3 are connected in a star shape, and their neutral point N
are configured so that they are located within each device and are not exposed to the outside. Therefore, when configuring this power harmonic filter device as a reduced-sized equipment with a sealed structure, only the connections between the three-phase capacitor 1, the three-phase reactor 2, and the three-phase resistor 3 are connected to the connecting bus of the oil-filled pipe. It will be connected with.

Here, it will be explained that the characteristics as a harmonic filter do not change even if the neutral point N of the three-phase reactor 2 and the three-phase resistor 3 are not directly connected.

In Fig. 6, the reactance L of each phase of the three-phase reactor 2 and the resistance R of each phase of the three-phase resistor 3 are connected in parallel, and this composite impedance Z
The calculation results in the following formula.

Z=jωL・R/R+jωL …(1) Here, ω is the angular velocity, the frequency is Hz, and pi is π.
Then, it is equal to 2π.

Figure 2 is an equivalent circuit diagram of the harmonic filter device of the present invention shown in Figure 1, where C is the capacitance for one phase of the capacitor, L is the reactance for one phase, and R is the resistance for one phase. There is.

When this circuit is converted into a triangular connection with equal impedance, the result is shown in FIG. In Figure 3, if the reactance for one phase corresponding to one side of the triangular connection is L', and the resistance for one phase is R', the circuit shown in Figure 2 and the circuit shown in Figure 3 have equivalent impedance. In order to do so, the relationship L′=3L, R′=3R…(2) must exist.

If Figure 3 is drawn so that the triangular connections of reactor L' and resistor R' are overlapped, Figure 4 is obtained. Here, the reactance L′ and resistance R′ of each phase are connected in parallel, and the combined impedance of both is
Letting Z' be the following equation.

Z'=jωL'・R'/R'+jωL'...(3) In Figure 4, the combined impedance Z' of reactance L' and resistance R' is a triangular connection, but it can be changed to a star connection with equivalent impedance. When converted, it becomes Figure 5. If Z is one phase of the impedance of the converted star-shaped connection in this figure, then there is a relationship of Z=Z'/3. Therefore, when calculating Z using the relationship between equations (2) and (3), the result is as follows.

Z=Z'/3 =jωL'・R'/3(R'+jωL') =jωL・R/R+jωL...(4) In other words, the neutral point N of the conventional reactor 2 and resistor 3 is connected with the connecting wire 6. Equation (1), which is the impedance of the configuration, and (4), which is the impedance of the configuration of the present invention.
The value is the same as the formula, and it can be seen that the characteristics as a harmonic filter do not change.

In this way, since the neutral point terminal N of the three-phase reactor 2 and three-phase resistor 3 is not drawn out, the neutral point bushing and the neutral point side connection bus bar are not required, and moreover, the neutral point terminal N of the three-phase reactor 2 and the three-phase resistor 3 is not drawn out. The internal insulation of the device can sufficiently cope with the increase in the potential of the electric point N, and there is no need to specially strengthen the insulation.

Furthermore, since there is no connection line on the neutral point N side, there is more freedom in the placement of the three-phase reactor 2 and three-phase resistor 3, which reduces the number of connection buses and reduces installation space and installation work. can be configured at low cost.

[Effect of idea]

As described above, according to the present invention, the three-phase capacitor is placed on the power supply side, the three-phase reactor and the three-phase resistor are connected in a star shape, and their neutral points are not connected to each other. This eliminates the need for connecting wires, which reduces equipment insulation and connection busbars, reduces installation work and installation space, and has the advantage of being inexpensive.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing one embodiment of a power harmonic filter device according to the present invention, Figs. 2 to 5 are various equivalent circuit diagrams for explaining the operation of the present invention, and Fig. 6 is a conventional circuit diagram. FIG. 2 is a circuit diagram showing a harmonic filter device of FIG. 1... Three-phase capacitor, 2... Three-phase reactor, 3... Three-phase resistor, 4... Power supply side terminal, 5...
Load side terminal.

Claims (1)

[Scope of utility model registration request] In a power harmonic filter device that consists of a three-phase reactor and three-phase resistor connected in parallel and a three-phase capacitor connected in series, the three-phase capacitor is placed on the power supply side, and the three-phase reactor and three-phase resistor are connected in series. A power harmonic filter device characterized in that the wires are connected in a star shape, and their neutral points are not connected to each other.