JPS6345814Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a cross-current compensation circuit that adjusts the share of reactive power of AC (synchronous) generators operating in parallel.

One of the purposes of excitation control of an alternator is to adjust the sharing of reactive power during parallel operation. A cross-current compensation circuit is involved in this reactive power sharing adjustment, and an example thereof is shown in FIG.

In Figure 1, 1 is an alternator, 2 is an AVR
(automatic voltage regulator), 3 is an instrument transformer that detects the generator output voltage and uses it as the voltage detection input of the AVR;
4 is a current transformer that detects the armature (load) current, 5 is a cross current compensation resistor, which connects the AVR 2 and the voltage transformer 3.
The current transformer 4 is inserted between the secondary terminals of the current transformer 4 and connected between the secondary terminals of the current transformer 4. That is, the circuit configuration is such that the voltage detection input of the AVR 2 is corrected by the reactive current.

The reactive power sharing characteristics (voltage-current characteristics) of the cross current compensation circuit with the above configuration are as shown in Figure 2 when the existing and new machines are used in parallel. OB), during overcurrent (OA′・
The voltage drop characteristic has the same rate of change regardless of OB').

By the way, if a new generator is added to the existing generator and connected in parallel, and there is a connection to a load that generates a large short-term overcurrent, such as when a large-capacity induction motor is connected directly, it is possible that the existing generator is made by another company. In some cases, the machine is old and its short-term overcurrent capability is unknown.

In such a case, when sharing the reactive power between each generator, (a) below the rated current, it will be proportional to the rated capacity of each generator. (b) It is important to satisfy the condition that the existing generator will not share more than a certain overcurrent value in the event of an overcurrent.

However, if the above-described cross-current compensation circuit is applied to the parallel operation of an existing machine and a new machine with the above-mentioned limitations, the existing generator will also have to share in the overcurrent, which is undesirable.

This invention was made taking the above points into consideration.
By using an element with non-linear characteristics that saturates the compensation voltage with a constant current as the cross-current compensation element, we have created a cross-current compensation circuit that can reliably share the reactive power in the event of overcurrent with the newly installed machine during parallel operation due to expansion. The purpose is to provide.

Hereinafter, the present invention will be explained in detail based on illustrated embodiments.

Fig. 3 shows an embodiment of the present invention, in which 1 is an alternating current generator, 2 is an AVR, 3 is an instrument transformer, and 4 is an AC generator.
is a current transformer, and 5' is a nonlinear resistor as a cross-current compensation element.As shown in Fig. 4, this resistor 5' is a voltage - at which the voltage V _CT is saturated when the current I _CT is above a certain value (rated current). It has a current. This resistance 5'
The circuit configuration inserted between the AVR 2 and the potential transformer 3 and connected between the secondary terminals of the current transformer 4 is the same as the conventional one (FIG. 1).

With this configuration, if this cross-current compensation circuit is attached to the existing machine during parallel operation due to expansion, the compensation voltage will be saturated at the rated current of the existing machine and become constant, and the reactive power sharing between the two machines will be as shown in Figure 5. On the existing equipment side, the current is limited to a certain value, such as below rated current (OA) and overcurrent (OA'). Therefore, even if the short-term overcurrent withstand capacity of the existing equipment is unknown, it will not be assigned an excessive amount of responsibility, which can contribute to the prevention of failures due to overcurrent. In other words, the existing equipment can be used effectively when increasing the capacity of the existing power supply.

FIG. 6 shows another embodiment of the present invention, in which a current transformer 4' as a cross-current compensation element has a secondary current I _CT for a primary current I ₁ exceeding a certain value as shown in FIG. 7. This is a case where a saturated current transformer is used in which the current is a certain constant value, and in this case, the cross current compensation resistor 5 is a normal resistor as in FIG.

Even with this configuration, the secondary current I _CT of the current transformer 4' remains constant at the rated current of the existing machine, and accordingly, the compensation voltage becomes constant. The reactive power share does not increase with overcurrent and remains constant.

As described above, according to the present invention, the resistor or current transformer as a cross-current compensation element has a non-linear characteristic that saturates the compensation voltage at a certain current or more. This eliminates the need for the other parties to bear an excessive burden of responsibility, and is effective in making effective use of existing power sources.

[Brief explanation of the drawing]

Fig. 1 is a connection diagram showing an example of a conventional cross current compensation circuit, Fig. 2 is a diagram showing reactive power sharing characteristics when using a conventional cross current compensation circuit, and Fig. 3 is a diagram showing a cross current compensation circuit according to the present invention. A connection diagram showing one embodiment, FIG. 4 is a voltage-current characteristic diagram of a nonlinear resistor as a cross-current compensation element in the same embodiment, FIG. 5 is a diagram showing reactive power sharing characteristics of the same embodiment, and FIG. A connection diagram showing another embodiment of the present invention, FIG. 7 is a characteristic diagram of the saturated current transformer in the embodiment of FIG. 6. 1... AC generator, 2... AVR, 3... Instrument transformer, 4... Current transformer, 4'... Saturation current transformer,
5...Cross current compensation resistance, 5'...Nonlinear resistance for compensation.

Claims (1)

[Scope of claim for utility model registration] It has a cross-current compensation element that corrects the voltage detection input of the automatic voltage regulator using the reactive current of the synchronous generator, and the reactive power when the existing generator and the new generator are operated in parallel. In the cross-current compensation circuit that adjusts the division of power, a compensation circuit using an element with non-linear characteristics that saturates the compensation voltage with a constant current is provided as the cross-current compensation element on the existing generator side of the parallel-operated generators. A cross current compensation circuit characterized by: