JPH09135538A - Automatic parallel operation equipment for engine generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent unwanted current (cross current) from flowing among generators without finding a power factor of a load when a plurality of the engine generators are paralelly operated. SOLUTION: In a cross current controlling process which is conducted in a parallel operation equipment, the output voltage and the current of a generator are detected in a step (hereinafter abbreviated as S) 110 and a phase difference between the output voltage and the current is detected in S120. In S130, a reactive current Ir is calculated from the phase difference and the current detected in S110. In S140, the reactive current Ir and a target value I0 are compared. When the reactive current Ir is larger, the next step is S150 and there the voltage is stepped down. When the reactive current is smaller, the next step is S160 and there the voltage is stepped up. If all the generators get through this process, the voltage is converged to a value corresponding to the reactive current I0 and there is no appearing of cross current. Furthermore, there is no necessity of finding a power factor of a load and so no structure nor wiring for detecting the power factor is required.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the frequency of each engine generator when operating a plurality of engine generators in parallel.
The present invention relates to an automatic parallel operation system for engine generators used to equalize phase and voltage.

[0002]

2. Description of the Related Art Conventionally, a plurality of engine generators are arranged in parallel to supply electric power to one load. When performing such parallel operation of generators (also referred to as parallel operation), an automatic parallel operation apparatus for engine generators (hereinafter, also simply referred to as parallel operation apparatus) is used. For example, the parallel operation device of Japanese Patent Publication No. 4-61579 discloses
Provided on each generator, the frequency, phase,
In addition, stable power supply is realized by adjusting the voltage and the voltage and making the load sharing even.

When the generators are operated in parallel in this way, a current (generally called a cross current) having a phase delayed with respect to the waveform of the bus voltage flows between the generators. This cause is mainly
The electromotive force of each generator is controlled so that the parallel operation device voltages become equal as described above, but there is a slight potential difference. This cross current has the effect of making the terminal voltage of both generators the average value of the electromotive force of both generators (however, when the synchronous impedances of both generators are equal), and as a result, the bus voltage also averages the electromotive force of both generators. It becomes a value.

This cross current has not been regarded as a problem for some time, but in recent years, it has become impossible to ignore it as a large number of generators are arranged in parallel in order to supply electric power to a higher load. In order to suppress the cross current, it is sufficient to make the electromotive force of each generator equal, but as described above, the terminal voltage of the generator becomes equal by connecting each generator, so the true electromotive force is Can not be detected.

Therefore, instead, the reactive power of the load is detected, and the exciting current of each generator is adjusted so that the power factor of each generator becomes equal to the power factor of the load that is found as a result, so that cross current is eliminated. (See, for example, Japanese Utility Model Laid-Open No. 52-12833).

[0006]

However, in order to calculate the power factor of the load, it is necessary to measure a large current flowing through the load, and in consideration of the versatility of the parallel operation device, various loads can be used. It is necessary to deal with this, and even a measuring device such as load power is very expensive. And
The installation location of this measuring device must be secured, and the wiring to the measuring device must be made for each parallel operation device.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide an automatic parallel operating system for an engine generator, which does not need to measure the electric power of a load or the like.

[0008]

The automatic parallel operating system for an engine generator according to claim 1 of the present invention made to achieve the above object is driven by an engine and designated by a voltage setting means. When a plurality of engine generators capable of outputting a voltage are operated in parallel, an engine generator automatic parallel operation device provided for each engine generator detects a reactive current output by the generator. A reactive current detection means and a command for correcting the voltage setting value to the voltage setting means are issued in accordance with the amount of the reactive current detected by the reactive power detection means, and between the plurality of parallel generators. And an electromotive force correction unit that reduces a cross current that is a flowing current.

The present invention described in claim 2 provides the present invention in claim 1.
In the automatic parallel operation device for engine generator described in
Voltage detection means for detecting the output terminal voltage of the generator,
Target value setting means for setting a target value of the reactive current amount based on the detection result by the voltage detecting means, and the electromotive force correcting means is configured to detect the current of the reactive current detected by the reactive current detecting means. When the quantity is larger than the target value set by the target value setting means, the voltage setting means is instructed to lower the voltage and raise the voltage when smaller than the target value.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An automatic parallel operating system for engine generator according to claim 1 of the present invention comprises a reactive current detecting means,
An electromotive force correction unit is provided, and is provided for each generator that is operated in parallel. A plurality of the generators are connected in parallel to the same load (the number is not limited), and each generator is driven by an engine. The parallel operation device applied to one of these generators will be described below.

The reactive current output by this generator is
The reactive current detection means detects, and the electromotive force correction means issues a correction command to the voltage setting means according to the detected amount of the reactive current. This correction command is for correcting the set value of the output voltage of the generator set by the voltage setting means, and the set voltage of the generator is changed by this command, and the potential difference with other generators is changed. Reduces and suppresses cross current flowing between both generators. This is due to the following actions.

In the two generators in which the cross current flows, the cross current flowing out from one of the generators at a certain time point will flow in when viewed from the other. Therefore, the phases of the cross currents flowing through each generator differ from each other by 180 °, and when the cross current is added to the original current flowing through each generator, the phase difference for each voltage is increased on the one hand and decreased on the other hand. Will be. This is the case where there are two generators, but the principle is the same when three or more generators are operated in parallel. That is,
In some generators, the phase difference between the voltage and the current increases and the reactive current increases, while in other generators, the reactive current decreases. That is, the amount of reactive current is affected by the potential difference between the generator and another generator.

In order to suppress the cross current, the set voltage may be corrected so that the potential difference between the two generators, which is the cause of the cross current, becomes small. The purpose of the parallel operation device is to perform this correction according to the value of the reactive current in the generator. Therefore, according to the parallel operation apparatus of the first aspect, the set voltage of the generator is corrected according to the reactive current, so that the cross current can be suppressed without obtaining the power factor of the load. Moreover, since it is not necessary to obtain the power factor of the load, there is no need for an expensive device for measuring this power factor, and it is not necessary to secure a place for its installation. The connection between this measuring device and the operating device can also be dispensed with.

Further, since the load or the signal of another generator is not used as an input signal used for the control system and only the generator is detected, the response can be improved. Claim 2
In the parallel operation device according to, further provided with a voltage detection means and a target value setting means, the voltage detection means has detected,
The target value of the reactive current amount is set based on the output terminal voltage of the generator.

The cross current has a lagging phase with respect to the voltage in a generator having a large electromotive force, and has an advancing phase in a generator having a small electromotive force. Therefore, the reactive current also increases in the former case and decreases in the latter case. That is, by detecting the reactive current, the magnitude of the electromotive force that cannot be detected during parallel operation can be estimated.

Therefore, the electromotive force correction means decreases the set voltage when the value of the reactive current detected by the reactive current detection means is larger than the target value, and conversely increases it when the value is small. Thereby, the electromotive force of the generator can be adjusted to a value corresponding to the target value of the reactive current.

In this way, when the voltage set values are corrected in each of the generators operated in parallel, the electromotive force of all the generators converges to a value corresponding to the target value. That is, the electromotive force of the plurality of generators can be adjusted to a constant value. Therefore, according to the parallel operation apparatus of claim 2, all the effects of the parallel operation apparatus of claim 1 are achieved, and the correction by the electromotive force correction means is realized by the simple method as described above. Moreover, since the electromotive force is corrected while reflecting the voltage value that is actually output, it is possible to provide a parallel operating device with high versatility.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. First, FIG. 2 shows a parallel operation apparatus 1 according to an embodiment of the present invention, in which a three-phase separately excited brushless AC generator 3 (hereinafter, also simply referred to as a generator 3) driven by an engine (not shown). FIG. 3 is an explanatory diagram showing a state in which the output wiring is represented by only one phase in this figure in order to realize the above. The generator 3 is connected from the output terminal 5 to a load (not shown) and is operated in parallel with the generator also connected to this load. The output voltage, current and frequency of the generator 3 can be monitored by a voltmeter V, an ammeter A and a frequency measuring instrument F, respectively.

The parallel operation system 1 includes a generator 3 and an output terminal 5
It is connected to the generator 3 by a signal line 9 for a voltage signal and a signal line 11 for a current signal that are drawn out from the wiring 7 between them. A current corresponding to the current flowing through the wiring 7 is made to flow through the signal line 11 by the current transformer CT, and the signal line 11 and the signal line 9 are connected to the automatic voltage regulator AV.
It is also connected to R. The automatic voltage regulator AVR controls the voltage of the generator 3, and receives feedback of the generated voltage via the signal line 9 so that the generator 3 outputs the set voltage. A correction signal line 13 for transmitting a correction signal from the parallel voltage controller AVR to the automatic voltage controller AVR is interposed between the automatic voltage regulator AVR and the parallel voltage controller 1.

The generator 3 outputs a predetermined electric power when the driven shaft 15 is driven by the engine, and the field is generated by energizing the field coil GF by the exciter EXG. VR is a varistor for stabilizing the current flowing through the field coil GF. Exciter EXG
Is also mechanically directly connected to the driven shaft 15, and when driven by the engine, supplies a direct current to the field coil GF via the rectifier RT. That is, the automatic voltage regulator AVR regulates the current flowing through the field coil EXGF of the exciter EXG.

The automatic voltage regulator AVR is a battery B.
Power is supplied from at and a predetermined amount of current is supplied to the field coil E based on this, the set value in the voltage regulator VA, and the fed back output voltage and output current of the generator 3.
It is passed through XGF and controlled so that a desired output voltage is obtained. This automatic voltage regulator AVR and voltage regulator V
A corresponds to the voltage setting means of the present invention.

In addition to the signal lines 9 and 11, the conventional parallel operation device also has a terminal for inputting the voltage and current of the bus line connected to the load. There is no terminal to receive. Although not shown in the figure, the parallel operation device 1 is also provided with a signal line for issuing a signal for changing the rotation speed to the engine in order to control the frequency of the generator 3. A schematic configuration of this parallel operation device 1 is shown in FIG.

As shown in FIG. 3, the parallel operation device 1 receives the output voltage and current of the generator and the input voltage 21 and current of the generator, and also converts them from analog value to digital value. A / D converter 23 for
An output circuit 25 for outputting a correction signal to the automatic voltage regulator AVR, and a calculation described later based on the signals received from the input circuit 21, the A / D converter 23, etc., and output to the output circuit 25. CPU 27, a crystal oscillator 29 on which the operation timing of the CPU 27 is based, and a CP
RO in which a control program executed by U27 is stored in advance
It is configured as a computer system that includes an M31, a RAM 33 that temporarily holds numerical values necessary for processing by the control program and generated numerical values, and a bus 35 that connects these units.

The input circuit 21 is an interface for detecting a cycle of voltage and current of the generator 3 and for receiving signals used for detecting each phase of the voltage and current, and When the voltage signal and the current signal 3 (usually both sine waves) are input, each zero-cross point is detected, and a square wave is placed on the bus 35.
The CPU 27 recognizes the rising and falling edges of this square wave as zero-cross points. On the other hand, the A / D converter 2
Reference numeral 3 denotes an interface for converting a voltage signal and a current signal into a digital signal, and the CPU 27 quantitatively evaluates the voltage value and the current value of the generator 3 from the signal put on the bus 35 from here. Used to.

The output circuit 25 not only outputs a correction signal to the above-mentioned automatic voltage regulator AVR, but also drives an engine governor (not shown in FIG. 2) to change the rotational speed of the engine. It also outputs a signal to 37. Further, 39a is a signal for increasing the engine speed, and 39b is a signal for decreasing the engine speed. The field coil E is shown by 13a.
A correction signal that increases the current flowing through the XGF and increases the output voltage of the generator 3, and conversely is a correction signal that decreases 13b.

Next, the main processing performed by the CPU 27 will be described with reference to FIGS.
This will be described with reference to FIG. First, FIG. 4 shows a cross current suppression process of issuing a correction signal to the automatic voltage regulator AVR in order to suppress the cross current. It is assumed that this process is activated at regular intervals. When this process is started, the first step (hereinafter, S
The output voltage and current of the generator 3 are detected at 110. This is because the digital value output from the A / D converter 23 is read into a predetermined register of the CPU 27, and the RAM 3 is appropriately used.
It is carried out by storing in 3.

Then, in S120, the phase difference between the output voltage of the generator 3 and the current is detected. This is the input circuit 2
It is obtained by measuring the time difference between the rising edges of two square waves output by 1 corresponding to the voltage and the current, based on the clock generated by the crystal oscillator 29, dividing this by the period, and multiplying by 2. The period can be obtained by measuring the time from one rising edge to the next rising edge of any one of the two square waves.

Next, a process corresponding to the reactive current detecting means of the present invention for calculating the reactive current I _r from the phase difference and the current detected in S110 is performed (S130). The reactive current I _r is obtained by multiplying the actual value of the current obtained in S110 by the sine of the phase difference obtained in S120.

Then, in S140, the reactive current I _r is
The current value I ₀ as the target value is compared. The current value I ₀ is a current value that should flow with respect to the output terminal voltage of the generator 3 when no cross current flows, and is set based on the voltage value detected via the signal line 9. . In parallel operation, all generators are connected to the bus,
The instantaneous value of the electric potential of each phase becomes equal in all generators and busbars. Therefore, it can be said that the current value I ₀ is set according to the bus voltage.

Returning to the determination of S140, here the reactive current I
_If it is determined that _r is larger, the process proceeds to S150, where a correction command is issued to the automatic voltage regulator AVR to decrease the voltage, and if the reactive current I _r is smaller, S16
Proceeding to 0, a correction command for raising the voltage is issued. By doing so, the reactive current I _r of the generator 3 is converged to I ₀ . This will be described with reference to FIG.

FIG. 5 is a graph showing the relationship between the electromotive force E and the value of the reactive current I _r of a plurality of generators operated in parallel.
The vertical axis represents the electromotive force E of the generator, and the horizontal axis represents the reactive current I _r . Then, if the reactive current of the generator 3-1 is I _r1 , the electromotive force of the generator 3-1 is E ₁ (point P), and if the reactive current of the generator 3-2 is I _r2 , power is generated. The electromotive force of machine 3-2 is E
₂ (point Q).

However, these generator 3-1 and generator 3-2
Since they are operated in parallel with each other, a cross current flows and the generator 3-1
Has an output voltage of E ₀ (point P ′), and the output voltage of the generator 3-2 is also E ₀ (point Q ′). Therefore, the original electromotive force E ₁
The electromotive force of the generator 3-1 is corrected so that the output voltage corresponds to. For example, for the generator 3-1 S in FIG.
Since I _r1 is smaller than I ₀ according to the determination at 140, the electromotive force is increased (S160). On the other hand, generator 3
Similarly for -2, I _r2 is larger than I ₀ ,
The electromotive force is reduced (S150). Actually, since the cross current is reduced by correcting the electromotive force in this way, from the point P ′ to the point P (in the generator 3-2, the point Q ′ to the point Q).
Instead of going to point R, it goes to point R while keeping the output voltage near E ₀ . That is, both the generators 3-1 and 3-2 converge to a state where the amount of reactive current is I ₀ and the output voltage is E ₀ .

Thus, by providing the parallel operation device 1 for all the generators that are operated in parallel and performing the cross current suppression process, the reactive current in all the generators is converged to I ₀ and the electromotive force is also I. ₀ is converged to a value E ₀ corresponding to. In this way, the generated voltage is converged, so that no cross current occurs.
The processing of S140 to S160 corresponds to the processing as the electromotive force correction unit of the present invention.

When the voltage correction signal is generated in this way,
The cross current suppression process ends. In the cross current suppression process, the process of S120 can be performed in the same manner even if all of the portions for rising timing are replaced with falling edges. Next, the frequency control process will be described as one of the processes performed by the parallel operation device 1 other than the cross current suppression process. This is shown in FIG. It is assumed that the frequency control process is activated subsequent to the cross current suppression process.

In the frequency control process, the output voltage and current of the generator 3 are detected in S210, and the phase difference between the output voltage and current is detected in S220. This is S for the cross current suppression process.
Same as the processing performed at 110 and S120,
The cross current suppression process is performed once to detect the voltage and current reflected by the process.

Next, in S230, the active power Pa of the generator 3
Is calculated. This is obtained by obtaining the respective execution values from the voltage and the current detected in S210 and multiplying the product of these by the cosine of the phase difference obtained in S220. Then, in S240, the active power Pa and the required power P ₀ are compared. If the effective power Pa is larger than P ₀ , S25
0, a correction command is issued to the actuator 37 so as to reduce the engine speed, and if smaller, S26
Proceed to 0 and issue a correction command to increase the engine speed. In this way, the output power of the generator 3 is compensated.

As described above, if the cross current suppression process and the frequency control process are performed on the generator 3 and the set voltage of the generator is corrected according to the reactive current, the cross current flowing between the generators can be suppressed. it can. Moreover, it is not necessary to obtain the load power factor. Therefore, an expensive device for measuring the power factor of the load is not required, and it is not necessary to secure the installation place. The connection between this measuring device and the operating device can also be dispensed with.

Further, since the control system is housed in the generator 3 and the load and the signal of other generators are not used, the response can be improved. Above, as an example of the present invention,
Although the parallel operation apparatus 1 has been described, the present invention is not limited to these embodiments and can be implemented in various modes.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an automatic parallel operating system for an engine generator of the present invention.

FIG. 2 shows a parallel operation system 1 according to an embodiment of the present invention,
It is explanatory drawing which shows a mode applied to the generator 3.

FIG. 3 is a schematic configuration diagram of a parallel operation device 1 that is an embodiment of the present invention.

FIG. 4 is a flowchart of a cross current suppression process performed by the parallel operation device 1.

FIG. 5 is a graph showing how the electromotive force of each generator is made constant by the cross current suppression process.

FIG. 6 is a flowchart of a frequency control process performed by the parallel operation device 1.

[Explanation of symbols]

1 ... Parallel operation device 3 ... Separately-excited brushless AC generator 5 ... Output terminal 7 ... Wiring 9, 11 ... Signal line 13 ... Correction signal line 15 ... Driven shaft 21 ...
Input circuit 23 ... A / D converter 25 ... Output circuit 27 ...
CPU 29 ... Crystal oscillator 31 ... ROM 33 ...
RAM 35 ... Bus 37 ... actuator _{I r, I r1, I r2} ... target value Pa ... active power P ₀ ... power requirements of the reactive current I ₀ ... reactive current

Claims (2)

[Claims] 1. An engine generator provided for each engine generator when a plurality of engine generators driven by an engine and capable of outputting a voltage designated by a voltage setting means are operated in parallel. In the automatic parallel operation device, a reactive current detecting means for detecting a reactive current output by the generator, and a voltage for the voltage setting means according to the amount of the reactive current detected by the reactive power detecting means. An automatic parallel operation apparatus for an engine generator, comprising: an electromotive force correction unit that issues a command to correct a set value and reduces a cross current, which is a current flowing between the plurality of parallel generators. 2. The engine generator automatic parallel operating apparatus according to claim 1, wherein the reactive current amount is based on voltage detection means for detecting an output terminal voltage of the generator and a detection result by the voltage detection means. Target value setting means for setting the target value of, and the electromotive force correcting means sets the target value of the reactive current detected by the reactive current detecting means to the target value setting means. An automatic parallel operation apparatus for an engine generator, wherein a command is issued to the voltage setting means so as to decrease the voltage when the value is larger than the target value and increase the voltage when the value is smaller than the target value.