JPS6156693B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cross-current compensator, and particularly to a cross-current compensator that suppresses invalid cross-current that occurs when multiple generators are operated in parallel.
In particular, even if the CT ratios of multiple generator current transformers operated in parallel differ, it can be easily compensated for without adding a new current transformer.

A conventional device of this type is shown in FIG. In the figure, 1 is a generator, 2 is a current transformer for current detection provided, for example, in the S phase, 3 is a voltage detection transformer, 4 is a cross-current detection resistor connected to the output end of the transformer 2, and 5 1 shows a contact point of a parallel operation relay that opens when the generator 1 enters parallel operation, and 6 shows an automatic voltage regulator.

In the configuration shown in FIG. 1, the armature current of the generator 1 is detected by a current transformer 2 and converted by a cross current detection resistor 4 into a current detection signal in the form of a voltage. When the generator 1 enters parallel operation with another generator, the contact 5 is open, and the voltage signal obtained by stepping down the generator voltage by the transformer 3 is sent to the automatic voltage regulator 6 between both ends of the resistor 4. The obtained current detection signal is vector-combined and input. Now the secondary voltage of transformer 3 is V〓 _T
Assuming that _R is the voltage across the resistor 4, _V〓I is the voltage across the resistor 4, _V〓c is the input voltage of the automatic voltage regulator 6, and I is the S-phase current of the generator, these relationships are as shown in FIG.

For example, if a delayed cross current (this is defined as +θ) flows through the generator 1, the input voltage _V〓c becomes larger than the secondary voltage _V〓TR , as shown in Fig. 2. At this time, the automatic voltage regulator 6 detects that the generator voltage has increased and operates to reduce the field current and reduce the delayed cross current.

Conversely, when a forward (i.e. -θ) cross current flows to the generator 1, the input V〓 _c to the automatic voltage regulator becomes smaller than the generator voltage V〓 _TR , and the automatic voltage regulator 6 reduces the field current. It acts to increase and reduce the cross-current of advance.

Since the conventional cross current compensator operates as described above, the input signal V〓c to the automatic voltage regulator 6 includes the current detection signal _V〓I corresponding to the generator current, and the current detection signal _V〓I corresponding to the generator current is The drawback was that the actual generator voltage varied accordingly.

The present invention attempts to eliminate the drawbacks of the conventional ones as described above, and by connecting a current transformer that detects the generator current to each generator in a ring through a regulating resistance circuit, it is possible to adjust the current transformer according to the generator load. The present invention aims to provide a cross current compensator that prevents the actual generator voltage from fluctuating.

A cross-current compensation device according to the present invention includes: a transformer and a current transformer that detect the voltage and current of each generator operating in parallel; a cross-current detection resistor connected to the output end of the current transformer; an automatic voltage regulator that receives the vector addition of the outputs of the transformer and current transformer respectively provided to the current transformer, and two resistors connected in an L-shape to the output end of the current transformer, The generator includes an adjustment resistance circuit formed as a π-type resistance circuit with a resistor, and the output ends of the adjustment resistance circuits provided for all the generators are sequentially connected in a ring shape.

An embodiment of the present invention will be described below with reference to FIG. 3, in which parts corresponding to those in FIG. 1 are denoted by the same reference numerals.
In FIG. 3, an adjustment resistance circuit 11 is inserted between the output end of the current transformer 2 and the cross current detection resistor 4.
The adjustment resistance circuit 11 includes resistors 12 and 13 connected in an L-shape to the cross-current detection resistor 4, thus forming a π-type resistance circuit together with the cross-current detection resistor 4.

And the two output terminals t ₁ of this adjustment resistance circuit 11
and t ₂ are respectively connected to the output terminals t ₂ and t ₁ of a similar regulating resistance circuit 11A of the second generator 1A which is commonly connected to the power supplies R, S, T and operated in parallel,
In this way, a ring-shaped connection circuit is constructed. Note that the corresponding portion of the cross-current compensation circuit of the second generator 1A to the first generator 1 is indicated with a subscript A.

In the configuration shown in Fig. 3, the detection signal obtained between both ends of the cross current detection resistors 4 and 4A is
It is vector-combined with the next voltage and input to automatic voltage regulators 6 and 6A, respectively.

However, the resistor 4 and 4A therefore the adjustment resistor circuit 1
The voltages across 1 and 11A can be determined as follows. Now, the resistance value R4 of resistor 4.4A,
R4A is R, resistance value R7 of resistor 7 is KR (0<K
1), the resistance value R8 of resistor 8 is (1-k)R, resistor 7
The resistance value R7A of A is lR (0<l1), the resistance value R8A of resistor 8A is (1-l)R, and the current transformer 2,
Assuming that the secondary currents of 2A are I〓1 and I〓1A, respectively, this circuit can be expressed as the equivalent circuit shown in FIG. Here, current transformers 2 and 2A can be represented as current sources I〓1 and I〓1A.

In Fig. 4, the currents I〓 _a1 and I〓 _b1 flowing through the resistors 4 and 4A are the currents flowing out from the current source I〓 ₁ , and the currents I〓 _a2 and I〓 _a2 are flowing out from the current source I〓 _1A . It is a current and is determined by the following formula.

I〓 _a1 =I〓 _b1 =kR〓1/kR+(1-k)R+R/3×1/3=k/4I〓1 ……………(1) I〓 _a2 =I〓 _b2 =lR〓1A /lR+(1-l)R+R/3×1/3=l/4I〓1A…………(2
) Therefore, the voltage across the resistor 4 is R(I〓 _a1 −I〓 _b2 = R/4(kI〓1−lI〓1A)...
...(3), and the voltage across the resistor 4A is R (I〓 _a2 - I〓 _b1 ) = R/4 (lI〓1A - kI〓1)
...(4) becomes. Here, when the capacities of the parallel generators are equal and the current transformation ratios of the current transformers 2 and 2A are equal, the values of the constants k and l are set to mutually equal values that are not 0, and therefore |I〓1| and | When the magnitude and phase of I〓1A| match, the voltage across the resistors 4, 4A and therefore the adjusting resistance circuits 6, 6A becomes 0.

On the other hand, when the generator capacity is different and the current transformation ratio is different, the values of the constants k and l are set as follows. For example, the secondary current of the current transformer 2, 2A when the generator 1, 1A is operating at its rated value is |I〓1|
=2 [A], ｜I〓1A｜=3 [A] and slebe k/l
= 3/2.

At this time, the voltage across the resistor 4 is the current I〓1, I〓1A
Let _{the phases of ∠θ2} )...
………(5) becomes. Also, the voltage across the resistor 4A is R/4(lI〓1A−kI〓1)=lR/4( _3∠θ2−
3∠θ ₁ ) ……………(6), and if the phases, that is, the generator power factors match, each becomes 0.

Therefore, at the time of , the input to each automatic voltage regulator 6, 6A is simply the output signal of the transformer 3 or 3A. In addition, if there is a difference in the power factor of each generator, the voltage across the resistor 4 is changed to the transformers 3 and 3 to reduce this difference.
A vector is added to the secondary side signal of A. This means that if you stop the ring connection, the circuit in Figure 2 will become the
This can be seen from the fact that it is equivalent to the figure. Therefore, θ ₁ =θ ₂ on a steady basis.

Although the above-mentioned embodiment shows the case where there are two generators, in the case where there are two or more generators, the outputs of the adjusting resistance circuits 11, 11A, . . . may be similarly connected in a ring.

Moreover, the resistors 7, 8 and 7A, 8A may be constructed from a single variable resistor, while the adjustment resistor circuits 11, 11A are constructed from π-type resistor circuits.

As described above, according to the present invention, an adjustment resistance circuit formed of resistance elements connected in a π-type is provided at the output end of a current transformer, and this adjustment resistance circuit is connected to the adjustment resistance circuit of another parallel generator. Along with the ring connection, the cross current detection resistor 4,4A is connected by each resistor of each adjustment resistor circuit.
By adjusting this adjustment resistance circuit, even if the secondary current of the current transformer differs due to the current transformation ratio, etc., the current that flows through the current transformer can be adjusted.
The compensation output when no cross current is flowing can be made zero, thereby achieving the effect of performing cross current compensation without changing the generator voltage. In particular, since the adjustment resistance circuit is formed with resistance elements connected in a π-type, it is useful for current transformers of multiple generators operated in parallel.
Even if the CT ratio differs, cross current compensation can be performed with a simple circuit without the need to add and install a new current transformer.

Therefore, if π-type resistance circuits are used as the adjustment resistance circuits 11 and 11A as in the above embodiment, a relatively simple configuration can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a connection diagram showing a conventional cross current compensator, FIG. 2 is a vector diagram showing the relationship between its detection outputs, FIG. 3 is a connection diagram showing an example of the cross current compensator according to the present invention, and FIG. A connection diagram showing the equivalent circuit of Fig. 3,
FIGS. 5 and 6 are connection diagrams showing the current distribution of each current source broken down. 1,1A... Generator, 2,2A... Current transformer, 3,3A... Transformer, 4,4A... Cross current detection resistor, 5,5A... Parallel operation relay, 6,6A...
...Automatic voltage regulator, 11,11A...Adjustment resistance circuit.

Claims (1)

[Claims] 1. A transformer and current transformer that detect the voltage and current of each generator operating in parallel, a cross-current detection resistor connected to the output end of the current transformer, and the above-mentioned In a cross current compensator having an automatic voltage regulator that receives vector addition of the outputs of a transformer and a current transformer, two resistors are connected to the output end of the current transformer in an L shape, and the connected L A regulating resistor circuit is formed as a π-shaped resistor circuit by a type resistor and the cross current detection resistor, and the output ends of the regulating resistor circuit provided for all of the generators are sequentially connected in a ring shape. A cross-current compensator characterized in that it is configured to be connected.