JPH07222367A - Reactive current suppressing circuit for system interconnection generator - Google Patents

Abstract

PURPOSE:To provide a reactive current suppressing circuit having excellent characteristics and simple circuitry. CONSTITUTION:The reactive current suppressing circuit for system interconnection generator comprises a deciding function, e.g. a reactive current detecting function 4, and exciting current suppressing functions 21, 22 for nonutility AC generator. The exciting current suppressing functions 21, 22 function when a reactive current detected through the deciding function, e.g. the reactive current detecting function 4, exceeds a preset level. Means for reducing the exciting current through control of commutation phase angle may be employed in place of a fixed resistor 21 being inserted into an exciting circuit in order to suppress the exciting current.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit for suppressing an overload reactive current of a private AC generator installed in a business establishment in which a private AC generator is connected in parallel to a power supply system supplied from an electric utility. The present invention relates to a reactive current suppressing circuit for a grid-interconnected generator that does not cause an excessive reactive current to flow to a private AC generator even when a large load in the plant is activated.

[0002]

2. Description of the Related Art An electric power system is used in which a private AC generator is connected in parallel to a power supply system supplied from an electric utility to supply electric power to its own AC load device. FIG. 3 shows an outline of the connection of the power system in such means.
In FIG. 3, the AC circuit is a concept of the power system shown by a single line diagram. In FIG. 3, in a private power generator of a business establishment, a power output of an AC generator (hereinafter abbreviated as a generator) 1 driven by a prime mover (not shown) constitutes a business system through a breaker 2 for the generator. It is connected to the local distribution line 3. The output power of the generator 1 is CT (Current Transforme
r) 4 makes the output current component value PT (Potential T
The ransformer 5 detects the voltage component value. AVR (Automatic Voltage Regu
6) controls the exciting current supplied to the exciting winding 7 a of the exciter 7, which supplies the exciting current to the exciting winding 1 a of the generator 1. Reference numeral 7b indicates a rectifier that rectifies the alternating current output by the exciter 7. The DC power used inside the AVR 6 is supplied by converting the output voltage of the generator 1 into a predetermined voltage by the transformer 8 and converting it into DC by a rectifier circuit (not shown). The power receiving input supplied from the power generation function 10 of the electric power company is supplied to the local distribution line 3 which constitutes the above-mentioned in-office system through the power receiving breaker 11. The premises distribution line 3 has various premises load devices 13a, 13 in the office.
i, 13n, etc. are connected.

In the above-mentioned circuit configuration, the power reception capability and the operation of the local power system control device (not shown) correspond to the operating conditions of the local load devices 13a, 13i, 13n, etc.
The generator 1 controls the unillustrated prime mover and AVR 6 to generate an appropriate amount of electric power to be borne. In such a power system, the load current is borne by the power receiving system and the generator as shown in FIG. FIG. 4 shows the concept of a power distribution system. In FIG. 4, 10Z indicates the internal impedance of the power generation function 10 of the electric utility and the transmission and distribution lines,
1Z indicates the internal impedance of the generator 1. The electric power received from the electric utility and the electric power generated by the generator 1 are combined and supplied to the premises load 13 shown collectively via a circuit breaker 13S (not shown in FIG. 3). If the current supplied from the electric utility is IR and the current output from the generator 1 is IG, the current value IS supplied to the compound load 13 shown as a composite
Is expressed by equation (1). IS = IR + IG (1) In addition, the current I supplied from the electric utility to the premises load 13
R, the total current IG supplied from the generator 1 to the premises load 13 is expressed by the following equation. IG = [10Z / (10Z + 1Z)] × IS ... (2) IR = [1Z / (10Z + 1Z)] × IS ... (3)

[0004]

By the way, in the above power system, when the circuit breaker 13S is turned on and the current is supplied to the premises load 13, the premises load 13 looks like a high power motor. In this case, the starting current of the motor is large, and the internal impedance 10Z and the generator 1 on the electric utility side are
Depending on the relationship with the internal impedance 1Z, there is a case where an overcurrent flows to the generator as shown in the following formula (4). IG> IR (4) Therefore, if the load current becomes excessive, such as when the motor starting current is large, there is a risk that the generator will be burned out. In the grid-connected generator, as a measure to prevent overload of the generator when the power purchase becomes impossible,
For example, Japanese Patent Laid-Open No. Sho 56-56 has a means for minimizing the chance of load interruption by having a capacitor for reactive power supply and an automatic voltage regulator configured to switch the voltage setting value to a preset value. No. 153935. However, in this prior art,
There was no means to prevent overloading of the generator by controlling the reactive current while executing grid interconnection operation, which was insufficient. SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems (problems) of the conventional one, and to provide a system interconnection generator reactive current suppressing circuit which has a simple structure and can suppress a reactive current having a good characteristic.

[0005]

In order to solve the above-mentioned problems, in the reactive current suppressing circuit of the grid interconnection generator according to the present invention, the reactive current detecting function of the private AC generator,
A generator exciting current suppressing function is provided, and the generator exciting current suppressing function is activated when the reactive current value detected by the reactive current detecting function becomes larger than a preset predetermined value. In this case, a fixed resistor and a switch are connected in parallel to the exciting circuit as the generator exciting current suppressing function, and the switch is opened when the current is suppressed. A function may be provided to control the phase control function when the current is suppressed.

[0006]

As described above, the present invention is provided with the reactive current detecting function of the private AC generator and the generator exciting current suppressing function, and the reactive current value detected by the reactive current detecting function is preset. Since the generator exciting current suppressing function is activated when it becomes larger than the predetermined value, the generator reactive current is always suppressed to a value allowed for this generator.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a reactive current suppressing circuit of a grid interconnection generator according to the present invention will be described with reference to FIGS. 1 and 2 show the concept of the electric power system diagram by showing the AC circuit as a single line diagram. Further, the same reference numerals are used for the element functions corresponding to or the same as the element functions shown in FIG. 3 in the prior art. Example 1 In FIG. 1, a power generator for private use at a business site is a premises where an output power of a generator (alternating current generator) 1 driven by a prime mover (not shown) constitutes a business system through a circuit breaker 2 for the power generator. It is connected so as to be supplied to the distribution line 3. In the output circuit of the generator 1, CT4 is connected in series and PT5 is connected in parallel. The output circuit of CT4 and the output circuit of PT5 are connected to the AVR 20A. Although not shown in the AVR 20A, PT
It is assumed to have a determination function of determining whether the reactive current is equal to or more than a predetermined value from the voltage component detected by 5 and the output current component detected by CT4. The output circuit of the AVR 20A supplies an exciting current to the exciting winding 1a of the generator 1 via a parallel circuit of a fixed resistor 21 having a predetermined resistance value and a switch 22, and supplies the exciting winding 7a of the exciting machine 7 with the exciting current. The exciting current is controlled. Reference numeral 7b indicates a rectifier that rectifies the alternating current output by the exciter 7. The DC power used inside the AVR 20A is supplied to the generator 1 by the transformer 8.
The output voltage is converted to a predetermined voltage, converted into a direct current by a rectifier circuit (not shown), and supplied. The above-mentioned switch 22 is closed in a steady state to short-circuit the fixed resistor 21, but the reactive current becomes a predetermined value or more, and the above A
When the judgment function of the VR 20A operates, it is controlled so as to be opened. The power receiving input supplied from the power generation function 10 of the electric power company is supplied to the local distribution line 3 which constitutes the above-mentioned in-office system through the power receiving breaker 11. The premises distribution line 3 has various premises load devices 13a, 13 in the office.
i, 13n, etc. are connected.

In the above-mentioned circuit configuration, the indoor load device 1
When, for example, a large-capacity motor of 3a, 13i, 13n is activated, a current component of the output is detected by CT4 and a voltage component is detected by PT5. Therefore, the AVR20A
The output current component of the generator 1 detected by CT4, P
When it is determined from the voltage component detected by T5 that the reactive current output by the generator 1 is larger than a predetermined value set in advance, the switch 22 is opened. Therefore, AVR2
The fixed resistor 21 is inserted in the exciting circuit that supplies the exciting winding 7a of the exciting machine 7 from 0A, and the exciting current of the exciting machine 7 is reduced. Therefore, the generated current of the exciter 7 is attenuated and the excited current of the generator 1 is reduced. Therefore, the reactive current output from the generator 1 is reduced, and the output reactive current value of the generator 1 is previously set to AVR while the above-described control loop is balanced.
It is maintained at a safe predetermined value set to 20A. When the load current decreases and returns to the normal value, the AVR 20A determines this and closes the switch 22 to return to the normal excitation current control action of the generator 1.

Embodiment 2 In FIG. 2, the power generator for private use at a business site is configured such that the output power of a generator (alternating current generator) 1 driven by a prime mover (not shown) passes through a circuit breaker 2 for the business site to establish a system inside the business site. It is connected so as to be supplied to the constituent distribution line 3 constituting the premises. In the output circuit of the generator 1, CT4 is connected in series and PT5 is connected in parallel. The output circuit of CT4 and the output circuit of PT are AVR20B
Connected to. The output circuit of the AVR20B is the generator 1
The exciting current supplied to the exciting winding 7a of the exciter machine 7 that supplies the exciting current to the exciting winding 1a is controlled. Reference numeral 7b indicates a rectifier that rectifies the alternating current output by the exciter 7. The AVR 20B includes a maximum phase angle setter 25 for controlling the exciting current value of the exciter 7 and a phase angle control function 26. The maximum phase angle setting device 25 is set by the switch function 27 so that the generator 1 functions during the interconnection operation. Although not shown in the figure, the AVR 20B has the same determination function as that of the AVR 20A of the first embodiment, but since the other element functions are irrelevant to the present invention, the configuration and description thereof will be omitted. . The DC power used inside the AVR 20B is supplied by converting the output voltage of the generator 1 into a predetermined voltage by the transformer 8 and converting it into DC by a rectifier circuit (not shown). The output circuit of the transformer 8 is also supplied to the phase angle control function 26. The power receiving input supplied from the power generation function 10 of the electric power company is connected to the local distribution line 3 that constitutes the above-mentioned in-office system via the power receiving breaker 11. Various kinds of in-house load devices 13a, 13i, 13n, etc. in the office are supplied to the in-house distribution line 3.

In the above circuit configuration, the premises load device 1
When, for example, a large-capacity motor of 3a, 13i, 13n is activated, a current component of the output is detected by CT4 and a voltage component is detected by PT5. If the AVR 20B determines from the output current component of the generator 1 detected by CT4 and the voltage component detected by PT5 that the reactive current component output by the generator 1 is larger than a predetermined value set in advance, the AVR20B Controls the rectification phase angle of the alternating current input from the transformer 8 by the phase angle control function 26. That is,
The exciting current value supplied to the exciter 7 is reduced. In this case, the maximum reduction value of the exciting current is determined by the maximum phase angle set in the maximum phase angle setting device 25, and the exciting current of the generator 1 does not become too low. Therefore, even if a situation occurs in which the reactive current output by the generator 1 rises above a predetermined value, the reactive current is immediately reduced, and the output reactive current of the generator 1 is balanced with the above-described control loop balanced. The value is maintained at a safe predetermined value set in the AVR 20B in advance. When the load current decreases and returns to the normal value, AVR2
The function of 0B returns to the normal excitation current control operation of the generator 1.

The above description shows the basic method and configuration for realizing the technical idea of the present invention, and the functional configuration of the AVR can be variously applied and modified corresponding to the internal configuration of the conventional AVR. Of course you can. Further, although the example in which the exciting current of the generator 1 is supplied by the exciter has been described, the present invention is also applicable to the case where the exciting current is excited by other means, and the power supply used inside the AVR is obtained from the generator 1. However, it goes without saying that the present invention can also be applied to the case where the power can be supplied to the AVR even when the generator 1 is not generating power.

[0012]

Since the present invention is constructed as described above, it has the following excellent effects. The reactive current output by the generator is always suppressed to a value allowed by this generator, and there is no risk of the generator burning out. If a fixed resistor and a switch are connected in parallel to the exciting circuit as the generator exciting current suppressing function and the switch is opened when suppressing the current, the desired function can be obtained with a simple configuration. If a phase control function is provided in the exciting current rectifying circuit as a generator exciting current suppressing function and the phase controlling function is controlled when suppressing the current, the exciting current can be suppressed with high accuracy.

[Brief description of drawings]

FIG. 1 is a schematic block diagram illustrating a functional configuration of a reactive current suppressing circuit of a grid-connected generator according to a first embodiment of the present invention.

FIG. 2 is a schematic block diagram illustrating a functional configuration of a reactive current suppressing circuit of a grid-connected generator according to a second embodiment of the present invention.

FIG. 3 is a schematic block diagram showing a configuration of a power generation control function of a conventional grid interconnection generator.

FIG. 4 is a conceptual circuit diagram of a power distribution system for explaining the problems of the grid interconnection generator.

[Explanation of symbols]

 1: Generator (alternator) 1a: Generator excitation winding 2: Generator breaker 3: Premise distribution line 4: CT 5: PT 7: Exciter 7a: Exciter excitation winding 8: Transformer 10 : Power generation function of electric power company 11: Power receiving circuit breaker 13a, 13i, 13n: Internal load device 20A, 20B: AVR 21: Fixed resistor 22: Switch 25: Maximum phase angle setting device 26: Phase angle control function

Claims (3)

[Claims] 1. A private AC generator that is connected in parallel to a power supply system supplied from an electric utility, has a reactive current detection function of the private AC generator and a generator exciting current suppression function, and detects the reactive current. A reactive current suppressing circuit for a grid-interconnected generator, wherein the generator exciting current suppressing function is activated when the reactive current value detected by the function becomes larger than a preset predetermined value. 2. The grid interconnection generator according to claim 1, wherein a fixed resistor and a switch are connected in parallel to the exciting circuit as the generator exciting current suppressing function, and the switch is opened when the current is suppressed. Reactive current suppression circuit. 3. The reactive current suppression of the grid-connected generator according to claim 1, wherein a phase control function is provided in the exciting current rectifying circuit as the generator exciting current suppressing function to control the phase controlling function when suppressing the current. circuit.