JPS5928131B2 - Parallel operation generator disconnection control circuit - Google Patents

Description

[Detailed description of the invention] The present invention relates to a control circuit for parallel operating generators.

Generally, generators that operate in parallel are equipped with an automatic voltage regulator (
(hereinafter referred to as an AVR), and this AVR further includes a cross-current compensator.

In this case, the cross current compensator is adjusted on the premise that each generator receives a load distribution of active power and reactive power proportional to its rated capacity. For this reason, the following problem usually occurs when a so-called "slash" operation is performed in which the generators operating in parallel are disconnected from the operating system. In other words, when performing the above-mentioned discharge, the active power is transferred by operating the governor, but the governor cannot transfer the reactive power, so the discharge occurs while the reactive current remains. (hereinafter referred to as ACB) has an adverse effect on the contact life. On the other hand, in order to eliminate this drawback, it is possible to transfer the active power by operating the governor, then manually adjust the AVR's voltage setting device to transfer the reactive power, and then perform the conversion. This method has the disadvantage that it requires a very troublesome operation, that it is difficult to automate the disassembly operation, and that it cannot be carried out quickly and efficiently. Therefore, an object of the present invention is to prevent damage to contacts such as ACBs by making it possible to transfer not only active current but also reactive current to other machines in continuous operation with a simple operation when repairing generators in parallel operation. It is an object of the present invention to provide a sharp control circuit which can automate a parallel disassembly operation while preventing the occurrence of a turbulence.

In order to achieve such an object, the present invention changes the degree of drooping characteristics during transition of reactive current,
This will be explained in detail below using examples.

Fig. 1 is a circuit diagram showing the circuit configuration of one of the generators operated in parallel, and in the figure, 1 is an AC generator, 2
is an AVR, 3 is a voltage detection transformer, 4 is a current transformer for cross current compensation, and 5 is a resistor for cross current compensation.

FIG. 2 shows a vector diagram of the detected voltage in the circuit configuration shown in FIG. 4 and the voltage detected and converted by the cross current compensation resistor 5. Vector V3 is vector V1 and V2
This voltage is obtained by combining AVR2
The voltage is controlled by the AVR 2 based on this input. For this reason, the generator 1 can maintain the drooping characteristics shown in FIG. In addition,
In FIG. 2, ψ indicates the load power factor angle. Normally, the drooping characteristics of the generator 1 shown in FIG. 3 and the drooping characteristics of other generators are set to be equal. Note that the load current ratio shown in FIG. 3 is expressed as (load current/rated current) XlOO%.

FIG. 4 is a circuit diagram showing an embodiment of the parallel-operated generator disconnection control circuit according to the present invention, and the same parts as in FIG. 1 are denoted by the same reference numerals.

In the figure, 1a is a first alternating current generator, 4a is a current transformer for cross current compensation provided in this output circuit, 1b is a second alternating current generator, and 4b is a current transformer provided in this output circuit. It is. The current transformer 4a for cross current compensation is connected to both ends of the resistor 5 for cross current compensation, and is connected to the fixed contact 6b of the changeover switch 6.
, 6c, respectively. The fixed contact 6b and the movable contact 6a are drawn out and connected to the current transformer 4b in a crosswise manner. Therefore, when the changeover switch 6 is switched to the solid line side, the cross current compensating current transformer 4a and the current transformer 4b are connected crosswise, and when the changeover switch 6 is switched to the broken line side, the cross current compensating current transformer 4a and the current transformer 4b are connected crosswise. Current transformer 4b is simultaneously disconnected and short-circuited. In such a configuration, when transferring the load from the alternator 1a to the alternator 1b, first transfer the active power, then switch the changeover switch 6 from the solid line side to the broken line side, and switch the cross current compensation current transformer 4a. The input terminals of the changeover switches 6 to 6 are opened.

As a result, the voltage drop across the cross current compensating resistor 5 increases, and the vector V2 shown in FIG. 2 increases. As a result, the voltage characteristic changes from the solid line characteristic a to the chain line characteristic b, as shown in FIG. 5, and the reactive current can be shifted. In this case, the characteristics of the alternating current generator 1b also change as shown from d to c. In other words, in the voltage characteristics shown in Figure 5, during parallel operation, the load currents are balanced in terms of voltage at points A and C, respectively, and the operation is performed with 0A = 0C, but this can be resolved by shifting the loads. The load current ratio on the row side is small and the load current ratio on the side that carries the load is large, and the point of the load current shifts significantly, resulting in a difference in the generated voltage and a cross current, and this cross current flows to balance the load. will be maintained.

Therefore, by switching the changeover switch 6 to the broken line side as described above, the voltage characteristics of the AC generator 1a on the disconnected side are as follows.
As shown in b, the drooping characteristic becomes steep, and the load current ratio on the disconnected side is 0D, and the load current ratio on the load side is 0B, so that a balance is maintained, and the degree of occurrence of cross current is significantly reduced. When the reactive current is transferred by the method described above, the alternating current generator 1a is disconnected from the BUS by turning off ACBa, and the changeover switch 6 is returned to its original state to return to the normal cross current compensation state. The disconnection of the generator 1a can be completed. Therefore, since the ACB can be disconnected while the reactive current is being transferred, damage to the ACB can be prevented, and since the reactive current can be transferred by simply switching the changeover switch, it is possible to automate the disconnection operation. .

In this embodiment, the changeover switch 6 is not limited to a mechanical one, but may be constructed from a switching mechanism such as a semiconductor element.

As explained above, according to the parallel operation generator parallel disconnection control circuit according to the present invention, the AVR of the generator to be parallel operated is
Since the reactive current can be transferred by instantly increasing the input voltage of the ACB higher than that in the steady state, and then disconnecting the ACB, damage to the ACB etc. can be prevented.
Since the transition operation can be performed by a switching operation of a switch, great effects such as the ability to automate the disconnection operation are achieved.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram to explain the parallel disconnection method in general parallel operation, and Figures 2 and 3 are vector diagrams and characteristic diagrams to explain the parallel disconnection method explained in Figure 1. 4
FIG. 5 is a circuit diagram showing an embodiment of the parallel-operated generator parallel disconnection control circuit according to the present invention, and FIG. 5 is a characteristic diagram for explaining the parallel disconnect operation. 1a, 1b... AC generator, 2... Sent voltage regulator, 3... Voltage detection transformer, 4a...
... Current transformer for cross current compensation, 4b... Current transformer, 5... Current transformer for cross current compensation (resistor, 6... Changeover switch.

Claims (1)

[Claims] 1 The first and second alternating current generators that operate in parallel, and the first
a voltage detection transformer that detects the output voltage of the first alternator, an automatic voltage regulator that controls the first alternator, and a cross current that is connected between the voltage detection transformer and the automatic voltage regulator. A compensating resistor is provided in the output circuit of the first alternator, is connected to both ends of the cross-current compensating resistor, and is connected to a current transformer provided in the output circuit of the second alternator. A parallel-operation generator disconnection control circuit comprising a cross-current compensating current transformer connected to the cross-current compensating current transformer and a changeover switch for switching the connection between the cross-current compensating current transformer and the current transformer between cross-connection and disconnection.