JPS5951013B2 - power control device - Google Patents

Description

[Detailed Description of the Invention] This invention prevents voltage fluctuations and stabilizes the power system by installing it in parallel with power transmission lines, distribution lines, etc., and controlling the reactive power supplied to the system. The present invention relates to a so-called reactive power control device, particularly a variable reactance type power control device that can be continuously controlled.

FIG. 1 is a configuration diagram showing a conventional variable reactance type power control device using a thyristor.

In the figure, 10 is a generator, 20 is a power transmission/distribution line, 30 is a load, and 40 is a power control device. The primary winding 41 of the transformer is connected to the power transmission/distribution line 20, and the secondary winding 42 of the transformer includes thyristors 51, which are connected in antiparallel to each other.
52 and reactors 60u, 60, and 60w are connected in series. Further, a phase capacitor 70 is connected in parallel to the primary winding 41 of the transformer, and a plurality of filter circuits each including a reactor 81 and a capacitor 82 are further connected. FIG. 2 is a voltage and current waveform diagram for explaining the operation of FIG. 1.

Now, if a sinusoidal voltage such as Vu is applied to the U phase from the power system, and the thyristor 51U is fired at a phase delayed by electrical angle X from the peak point of Vu, a voltage VLU will be applied to the reactor 60U, as shown in the figure. A current iu flows. The value of this delayed current iu is controlled by the firing phase α of the thyristor. That is, the equivalent reactance seen from the l-order side of the transformer can be continuously changed by the value of α, and by using it in parallel with the phase advance capacitor 70, it is possible to freely control the supply of power from lead to lag to the power transmission and distribution line 20. I can do things. As a result, the voltage drop due to the reactance 21 of the power transmission and distribution lines can be compensated for, the voltage can be kept constant at a certain level, and the power system can be stabilized. In this conventional device, as is clear from the waveform in FIG. 2, as the firing phase α of the thyristor increases, the distortion of the current waveform, that is, the harmonic content ratio increases.

On the other hand, since the permissible distortion rate of power transmission and distribution lines is about 1% or less, it is necessary to provide a removal filter for each harmonic component, as shown in Figure 1, and especially for low-order harmonics, the capacity of this filter is also small. I needed something big. This invention was made in view of the drawbacks of the conventional devices described above, and by configuring a multiple variable reactor type power control device, even if the firing phase α of the thyristor is increased, low-order harmonic components are not generated. , it is possible to remove the filter or make it significantly smaller.

FIG. 3 shows the configuration of an embodiment of the apparatus of the present invention.

In the figure, the power control device 40 has a star-connected primary winding 41.
and a transformer having secondary windings 42, 43 with circular and star connections, and each secondary winding 42, 43 includes bidirectional thyristors (hereinafter referred to as BCR) 53U to 53W and 54u to 54W. Reactor 61U~61W, 62u
~62W series body is connected. Also, transformer 1
A phase advance capacitor 70 is connected in parallel to the next winding 41 . 4a to 4g show waveforms of various parts for explaining the operation of the embodiment of FIG. 3.

Taking the U-phase voltage VUl of the primary winding 42 of the transformer as a reference, and assuming that the ignition phase delay of each BCR 53u to 53W is α, the currents 11, 13, and 15 of each phase have a 2π/3 phase difference. Currents with waveforms such as those shown in FIG. 4A, b, and c flow.

On the other hand, the voltage V across UW of the winding 43.

2 is delayed by π/6 compared to VUl, so Fig. 4D
, e, f, the currents 12, 14, 16 of each phase are delayed by π/6 with respect to 11, 13, 15, respectively.

Here, the ratio of the secondary windings 42 and 43 of the transformer is set so that the applied voltage magnitudes 1U11 and 1Vu21 are equal (i.e.,
The winding of the secondary winding 42 for each phase/the number of turns of the secondary winding 43 = ψ allowed), and the reactors 61u~6]W, 62U~62W
If all are made equal, U of the primary winding 41 of the transformer
Base of phase current 1u. The effective value of the main wave is twice the value of i1.

Also, if the waveform in the figure is Fourier expanded, it becomes 12n±1 (n:
It can be seen that all components other than the (integer) order harmonics become zero regardless of the value of α, and waveform distortion is greatly improved. As a result, it is possible to eliminate a conventional filter. Even if a refilter is provided, it is sufficient to deal with high-order harmonics, and the refilter can be made smaller in proportion to the frequency. Fig. 5 is a block diagram showing another embodiment of the present invention, which differs from the embodiment shown in Fig. 3 in that the primary circuit of the transformer is connected in a star pattern and the neutral point is grounded, which is suitable for high-voltage circuits. , and thyristor 51
The point is that U~51W and 52U~52W are connected in antiparallel.

In this case, in order to form a closed circuit, the thyristors 51u to 5
1W and the other phase thyristors 52U to 52W in series must be conductive, and the gate firing signal to the thyristor is a double pulse shifted by π/3 as shown in Figure 6. Or it must continue for a period of π/3 or more. FIG. 7 is also a configuration diagram showing still another embodiment of the present invention, in which the secondary windings 52, 5 of the transformer are
3 are star-connected to have a phase difference of π/3, and the thyristor side is also star-connected so that both can be grounded at the neutral point and form independent closed circuits for each phase.

In addition, in this embodiment, as in the conventional embodiment shown in FIG. 1, a tertiary winding 49 connected in a ring is provided in the transformer to form a zero-phase component processing loop in the event of an accident such as a one-line ground fault. , 3rd
In the embodiment shown in FIGS. 5 and 5, the secondary winding 42 also fulfills this function, so there is no need to provide it separately. FIG. 8 is a block diagram showing still another embodiment of the present invention, in which the secondary winding of the transformer has a winding 42 in phase with the primary winding 41, and a winding 42 having the same phase as the primary winding 41. In addition to the winding 43 having a phase difference, windings 44 and 45 having a phase difference of π/12 and π/4, respectively, with respect to the primary winding are newly provided.

Also, select the turns ratio so that the phase voltages of the four secondary circuits are equal, and
If the values of 2W, 63U~63W, and 64U~64W are made equal, the phase current 1u flowing through the primary winding 41 of the transformer is:
As shown in FIG. 9, even if the firing phase α of the thyristor is controlled, it approaches a nearly positive arc wave. If this Iu is subjected to Fourier expansion, it can be seen that all components other than the 24n±1st harmonic He component are always zero regardless of the value of α.

FIG. 10 shows a vector diagram for the fundamental wave component of the primary current in the configuration of FIG. 8.

Further, in the embodiments shown in FIGS. 5, 7, and 8, a reactor is provided separately, but it is also possible to utilize the leakage inductance of a transformer.

As described above, the present invention provides a transformer with a predetermined phase difference of π/6.
Alternatively, by providing two or four secondary windings with π/12 and connecting each with a reactor and an anti-parallel thyristor switch in series, even if the firing phase α of the thyristor is controlled, the primary winding of the transformer is always 12n±1 or 24n on the side
This realizes a multiplexed power control device that can supply and control reactive power without including harmonic components other than the ±1st order, making it unnecessary or extremely small to use a harmonic removal filter, making it possible to downsize equipment and reduce costs. It is something that makes you familiar. Further, according to the present invention, there are many advantages in manufacturing the device, such as the impedance (value of the reactor) of each secondary circuit and the capacity of the thyristor can all be made equal. It is clear that the power control device of the present invention can be used not only as a reactive power supply source, but also for voltage stabilization, flicker prevention, and dynamic stabilization of power systems by controlling reactive power. be.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a conventional power control device, FIG. 2 is a waveform diagram for explaining the operation of FIG. 1, FIG. 3 is a configuration diagram showing one embodiment of the present invention, and FIG. 5 is a configuration diagram showing another embodiment of the present invention. FIG. 6 is a waveform diagram for explaining the operation of FIG. 5. FIGS. 7 and 8 are waveform diagrams for explaining the operation of FIG. Block diagrams showing still other embodiments of the present invention, No. 9
10 are waveform diagrams and vector diagrams for explaining the operation of FIG. 8. In the figure, 10 is the generator of the system, 31 is the load, 20 is the transmission and distribution line, 40 is the power control device, and 41 is 1 of the isolation transformer.
The next winding, 42-49 is the secondary winding of the isolation transformer, 51u
~54w is a thyristor, 60u~63w is a reactor,
70 is a phase advance capacitor, and 81 and 82 are reactors and capacitors that constitute a harmonic removal filter.

Claims (1)

[Claims] 1. A transformer having a series circuit of a thyristor and a reactor whose primary side is connected in parallel to a power transmission/distribution line and whose secondary side is connected in anti-parallel, and whose primary side is connected in parallel. In the power control device that includes a capacitor and controls the firing phase of the thyristor to control the power supplied to the power transmission and distribution line, the transformer has a plurality of secondary windings having a predetermined phase difference. 1. A power control device comprising a series circuit of the thyristor and the reactor, each of which has a series circuit of the thyristor and the reactor. 2. The power control device according to claim 1, wherein the phase difference between the secondary windings of the transformer is selected equally, and the values of the respective reactors are selected equally.