JPH1169634A - Received power controlling device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate hunting as quickly as possible, by outputting a command to increase or decrease the output of the generator of a non-utility power generating facilities when power received from a commercial power supply system is out of a given control target range and by setting an output increasing command with a longer outputting interval than that of an output decreasing command. SOLUTION: A received power controlling device 10 is made up of a first received power value determining means 11, which detects that received power measured by a received power meter 4 is deviating from dead band, and an output increasing and decreasing means 12, which output increased or decreased pulses if the first received power value determining means 11 detects the deviation from the dead band. Then, this output increasing and decreasing means 12 outputs pulses for increasing the output of a generator 5 of a non-utility power generating facilities, if the received power is exceeding the dead band, and if it is below the dead band, the means 12 outputs pulses for decreasing the output of the generator 5 of the non-utility power generating facilities.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiving power control for controlling a receiving power from a commercial power supply system to be substantially constant in a system interconnection operation system for operating a customer's private power generation equipment in connection with a commercial power supply system. Related to the device.

[0002]

2. Description of the Related Art In recent years, there has been a tendency for consumers to have their own power generation equipment such as a cogeneration (cogeneration) system and to supplement their own power consumption with the generated power. In some cases,
Private power generation equipment is often operated in connection with a commercial power supply system for effective use. A customer who is performing grid-connected operation supplies his or her own power as much as possible from a private power generation facility, and replenishes the shortage with power from a commercial power system, that is, a power company. There are two methods for this grid connection: "no reverse power flow", which does not allow the surplus power of the private power generation facilities to be sent to the power company, and "reverse power flow", which allows the power company to purchase the surplus power under certain conditions and purchase it. When the power receiving contract is made, it is decided which method to use for grid connection operation.However, there is a problem with the unit price of surplus power purchased by the power company, and generally there is no reverse power flow. There are many.

In general, the load on the premises fluctuates, so that the power generated by the private power generation equipment or the power received from the commercial power supply system is controlled in order to prevent reverse power flow in any case. When the load is large, the generator of the private power generation equipment operates at the rated output, and responds to the load fluctuation by adjusting the power received from the commercial power supply system. The power received from is kept constant, and the generator output of the private power generation equipment is increased or decreased in accordance with the load fluctuation.

[0004]

When the load on the premises is small and the power received from the commercial power supply system is to be controlled to be substantially constant, a reverse power flow does not normally occur even for a sharp change in the premises load. A control width ± P _db (dead band) centered on the predetermined received power control target value P _c as described above is set, and if the actual received power is larger than the dead band upper limit, the generator of the private power generation equipment is used. The output is increased, and when the received power is smaller than the dead band lower limit, the generator output is reduced.

In the conventional received power control device, it is determined that the received power has exceeded the upper limit value of the dead zone or has fallen below the lower limit value, and a pulse as a command to increase or decrease the output of the generator of the private power generation equipment is output for, for example, 4 seconds. Although output is performed at intervals, there is a certain time delay (for example, 12 seconds) before the generator actually increases or decreases the output. During this time, the generator output increase / decrease pulse is output several times. As a result, even if the received power falls within the control target range (dead zone) due to the first output increase / decrease pulse, the output may be increased / decreased by a subsequent pulse and may fall outside the dead zone again. On the other hand, an increase / decrease pulse in the opposite direction is output this time in an attempt to put the received power in the dead zone again, but also in this case, there is a time delay of the control similarly to the above, and the pulse goes out of the dead zone too much. . By repeating such an operation, the generator periodically increases or decreases the output. This phenomenon is called hunting, and if the control is continued for a long time, it eventually falls within the dead zone, but it is extremely inefficient from the viewpoint of the life of the equipment and fuel consumption.

Conventionally, when such hunting has occurred, if the hunting is mild, the hunting may be left as it is, and may naturally wait within the dead zone. Engineers are dispatched to the site to adjust the dead band width and output fluctuation settings based on the technician's experience and intuition.However, the labor and labor costs required for this are not small, and urgent It is also undesirable from the viewpoint of efficiency to keep a technician waiting for a situation.

[0007] The present invention has been made in view of the above points, and an object of the present invention is to provide a received power control device that eliminates hunting as quickly as possible in a system in which a private power generation system and a commercial power supply system are connected to each other. Aim.

[0008]

In order to achieve the above object, according to a first aspect of the present invention, it is determined whether or not electric power received from a commercial power supply system is outside a predetermined control target range (dead zone). Power receiving power value determining means for determining whether the output of the power generator is increased or decreased, and an output increasing / decreasing means for outputting a command to increase or decrease the output of the generator of the private power generation facility when the power is outside the predetermined control target range. Is set longer than the output interval of the output reduction command.

According to a second aspect of the present invention, the power received from the commercial power supply system is within a predetermined control target range (dead zone).
A first received power value determining means for determining whether the power is outside of the predetermined range, and an output increasing / decreasing means for outputting a command to increase or decrease the output of the generator of the private power generation facility when the power is outside a predetermined control target range, The output interval of the output increase / decrease command is set to be longer than the output interval of the output increase / decrease command in the normal control mode.

In a third aspect of the present invention, hunting detecting means for detecting whether the generator of the private power generation facility is hunting, and switching from the normal control mode to the slow control mode when hunting is occurring. A control mode switching means is provided, and in the slow control mode, the output interval of the output increase command is set larger than the output interval of the output decrease command or the output interval of the output increase / decrease command is set larger than the output interval of the output increase / decrease command in the normal control mode.

[0011] In a fourth aspect of the present invention, the second step of judging whether or not the absolute value of the difference between the power received from the commercial power supply system and the predetermined control target value is equal to or more than a predetermined multiple of the predetermined control target range. Receiving power value determining means, and a control mode switching means for switching from the normal control mode to the slow control mode when the power is less than or equal to a predetermined value, wherein the output interval of the output increase command in the slow control mode is larger than the output interval of the output decrease command. Alternatively, the output interval of the output increase / decrease command is set to be longer than the output interval of the output increase / decrease command in the normal control mode. In a fifth aspect of the present invention, a second received power for determining whether an absolute value of a difference between power received from a commercial power supply system and a predetermined control target value is equal to or more than a predetermined multiple of a predetermined control target range. Value determination means, hunting detection means for detecting whether or not the generator of the private power generation facility is hunting when the hunting is not more than a predetermined multiple, and control mode switching for switching from the normal control mode to the slow control mode when hunting is occurring Means in the slow control mode, wherein the output interval of the output increase command is set larger than the output interval of the output decrease command or the output interval of the output increase / decrease command is set larger than the output interval of the output increase / decrease command in the normal control mode.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

FIG. 1 is an electrical diagram of a system interconnection system using a first embodiment of a received power control device according to the present invention. In the figure, 1 is a commercial power supplied from a power company, 2 is a disconnector, 3 is a circuit breaker, and 4 is an instrument transformer PT.
And a power receiving wattmeter that measures power received from the commercial power supply 1 via the current transformer CT, a generator 5 for a private power generation facility operated by a gas engine, for example, and a power receiving control device 10 according to the present invention. , 20 are generator control devices for controlling the power generated by the generator 5.

The generator control device 20 includes a governor 21 and
Actuator 22 driven by this governor 21
And a gas engine 23, and the actuator 22 adjusts an opening degree of a valve 24 that adjusts a supply amount of the fuel gas supplied to the gas engine 23.

On the other hand, the received power control device 10 comprises a first received power value judging means 11 for detecting that the received power measured by the received power meter 4 is out of the dead zone, It comprises an output increasing / decreasing means 12 for outputting an output increasing / decreasing pulse when the judging means 11 detects that it is out of the dead zone. This output increasing / decreasing means 12 is connected to the generator 5 when the received power exceeds the dead zone.
And an output decrease pulse for decreasing the output of the generator 5 when the output is below the dead zone.

FIG. 2 is a flowchart showing the control operation of the first embodiment of the received power control device in the above-mentioned system interconnection system. The control operation will be described with reference to FIG. After the timer reset (F-1), measures the power P _r for receiving from the commercial power supply 1 by receiving power meter 4 (F-
2). In a first received power value determining unit 11, whether the upper limit value P _ch more dead band received power P _r is determined by setting the control range ± P _db in the control target value P _c is determined (F- 3) If this is the case, a command to that effect is given to the output increasing / decreasing means 12, and as a result, an output increasing pulse is output from the output increasing / decreasing means 12 (F-4). The received power P _r is whether less dead zone lower limit value P _cl is determined (F-5), is commanded to that effect outputting adjusting unit 12 equal to or less than, the output down pulses from the result output adjusting unit 12 Is output. The output interval of the output increasing pulse is set time T ₂ (for example, 15) which is considerably longer than the output interval (for example, 4 seconds) in the conventional control.
Second) (F-7), and the output interval of the output reduction pulse is a shorter set time T ₁ (for example, 4 seconds) (F-8).

As described above, in the first embodiment,
The output interval of the output increase pulse is set to be longer than before (therefore, in the following, such control is referred to as "slow control").
It is possible to determine after the completion of the control for increasing the output of the generator for one output increase pulse whether or not an additional output increase pulse is necessary, thereby avoiding excessive control of the output increase. Can escape from the hunting state. Output interval T of output reduction pulse
₁ was shorter than the output interval T ₂ of the output increase and decrease pulse,
This is because, if the received power is too small, a reverse power flow may occur if control is delayed. If there is no risk of reverse power flow, the number of output fluctuations of the generator 5 can be suppressed as much as possible by setting the output interval of the output increasing pulse as well as the output interval of the output decreasing pulse longer than in the past (for example, 4 seconds). Therefore, the control for increasing the output and the control for decreasing the output can be prevented from going too far, and the hunting state can be quickly escaped.

FIG. 3 is an electrical diagram of a system interconnection operation system using a second embodiment of the received power control device according to the present invention. 3, the same components as those of the embodiment shown in FIG. 1 are denoted by the same reference numerals, and the description will be omitted.

The receiving power control device 10A in this embodiment includes a hunting detecting means 13 for detecting whether or not the generator 5 of the private power generation facility is hunting;
When hunting is detected, the control mode of the generator 5 is changed from normal control (control in which both the output interval of the output increasing pulse and the time interval of the output decreasing pulse are performed in a short set time (for example, 4 seconds)) to the slow control. It comprises a control mode switching means 14 for outputting a switching command, and an output increasing / decreasing means 15 for changing the output interval of the output increasing / decreasing pulse in accordance with the control mode switching instruction.

Here, hunting detection by the hunting detecting means 13 will be described.

The hunting detection method includes the first method shown in FIG.
And the second method shown in FIG. (1) First hunting detection method: This method pays attention to the fact that the output of the output increase / decrease pulse always inverts in the control system when the hunting occurs, and counts the number of inversions. This is a method for detecting hunting.

In FIG. 4, the timer is reset (G
-1) After that, the memory M, the signal type (in this case, whether the output is increased or decreased) S, and the count value C of the counter are initialized (G-2). In the control system shown in FIG. 3, when hunting occurs, an output increase / decrease pulse is output. Therefore, it is first checked whether or not the output increase pulse has been output (G-
3) When output, S = 0 is set (G-4). If it is not output, it is next checked whether or not an output reduction pulse is output (G-5). If it is output, S = 1 is set (G-
6). In any case, it is checked whether or not the contents of the memory M and the signal type S are the same (G-7). If they are the same, it is determined that the same type of pulse has been output and the step (G-
Return to 3) and repeat steps (G-3) to (G-7). If M = S is not satisfied, it is determined that different types of pulses have been output, and the count value C of the counter is increased by 1 (G
-8), the content of the memory M is updated to the new signal type S (G-9). It is checked whether or not the elapsed time t up to that time has exceeded the set value T of the timer (for example, 3 minutes) (G-1
0), if not exceeded, then the count value C of the counter
Is checked whether or not exceeds the set value H (G-11). The set value H is a value which is determined in advance how many times the output is switched from the output increasing pulse to the output decreasing pulse and from the output decreasing pulse to the output increasing pulse when hunting is considered, for example, three times. Therefore, step (G-1)
In 1), the count value C of the counter is set to its set value H.
It is determined that hunting has occurred when G
-12). In step (G-10), the timer t1
Has exceeded the set value T, the count value C of the counter is cleared, the process returns to the start, and the step (G-
The operation from 1) is repeated. This is to determine whether hunting is truly occurring or due to normal fluctuations in the premises load.

Steps (G-10) and (G-11)
In any case, if both are determined to be "NO (No)", the process returns to step (G-3) and repeats the above steps. Thus, hunting is detected. (2) Second hunting detection method: This method is the same as the first hunting detection method described above, except that the number of counts is determined in order to determine whether the inversion of the output increase / decrease pulse is due to true hunting or load variation. Therefore, it is necessary to take a large amount of time, so that it takes time to determine hunting.

According to this method, the speed of increasing or decreasing the output due to hunting is determined by the ON-OFF of a single load.
It uses the property that it is slower than the speed of increase and decrease of the output due to the above, but is faster than the speed of increase and decrease of the output due to normal in-plant load fluctuation. In this method, hunting is detected by measuring the time required to pass through a dead zone at the time of output reversal.

In FIG. 5, the first and second timer resets (H-1), the memory M, the signal type S, the initialization of the count value C of the counter (H-2), and the presence / absence of output increase pulse (H-2) H-3), S = 0 (H-4), presence / absence of output pulse reduction (H-5), S = 1 (H-6), comparison between contents of memory M and signal type S (H- The steps up to 7) are the same as the above-described first hunting detection method. Step (H-
In 7), if the contents of the memory M and the signal type S are the same, it means that the same type of pulse is being output, and thus the output is being increased or output is being controlled.
Then, the second timer is reset (H-8), and the process returns to step (H-3). If not M = S, since i.e. pulse heterogeneous pulse is output so that the inverted, wherein the second time the elapsed time t2 is preset in the timer T _l and T _h (dead zone, the output (Determined by the fluctuation amount and the output cycle of the output increase / decrease pulse) are checked (H-9). The elapsed time t2 is equal to the times _Tl and T
not within the scope of the _h to update the contents of the memory M to the new signal type S (H-10). But when the elapsed time t2 of the second timer is in the range of time T _l and T _h is
Assuming that the possibility of hunting is high, the count value C of the counter is increased by 1 (H-11). This count value C
Is the number of inversions of the output increase / decrease pulse.

At this time, it is checked whether or not the elapsed time t1 of the first timer has exceeded the set value T1 (for example, 3 minutes) (H-
12) If it is within the set value T1, it is checked whether the count value C of the counter (corresponding to the number of inversions of the output increase / decrease pulse) has exceeded the set value H (H-13). This set value H has the same property as the set value H in the above-described first hunting detection method, and when the number of inversions is changed from the output increase pulse to the output decrease pulse and from the output decrease pulse to the output increase pulse, It is a value that determines in advance whether it is considered as hunting. Therefore, in step (H-13), it is determined that hunting has occurred when the count value C of the counter exceeds the set value H (H-14).
In step (H-12), when the first timer t1 has exceeded the set value T1, the count value C of the counter is cleared, and the process returns to the start and proceeds to step (H-1).
Repeat the operation from. If it is determined in step (H-12) and (H-13) that the result is "NO (No)", the memory M is updated in step (H-19), and in step (H-8) After resetting the timer 2, return to step (H-3) and repeat the above steps.

Since this method measures the time required for passing through the dead zone, if the dead zone passing time due to hunting can be specified to some extent, the set value H is extremely described.
May be 0. Therefore, in such a case, hunting can be detected in a relatively short time.

FIGS. 6, 7 and 8 are flowcharts showing different control operations of the second embodiment of the received power control device according to the present invention shown in FIG. The control operation will be described with reference to these figures.

First, the control operation shown in FIG. 6 will be described. Hunting of the generator 5 is always detected by the hunting detecting means 13 (J-1). The hunting detection method in this case is the first hunting detection method described with reference to FIGS.
And the second hunting detection method.

When hunting is not detected, a normal control method, that is, a control method in which the output interval between the output increasing pulse and the output decreasing pulse output from the output increasing / decreasing means 15 is a short set time (for example, 4 seconds) is adopted. (J-
2) When hunting is occurring, the timer is first reset (J-3), and the control is switched to the slow control system (J-4). The elapsed time t of the timer is equal to the set value T
(For example, 60 minutes).
When the set value T is reached, the process returns to step (J-1) and the above control operation is repeated. Hunting can be converged by performing such control.

The control operation of FIG. 7 is basically the same as the control operation of FIG. 6, except that steps (J-4) and (J-
The step (J-6) of detecting hunting once again is inserted between the step (5). However, the set value T in this case is a time for confirming the presence or absence of hunting, and thus is a set value of, for example, about 3 minutes. Therefore, it is possible to return to the normal control in a shorter time.

The control operation in FIG. 8 is basically the same as the control operation in FIG. 6, but instead of step (J-6) in FIG. 7, a step (J) for checking whether or not an output increase / decrease pulse has been output. -7). When the output increase / decrease pulse is output, it is determined that the output does not fall within the dead zone. Therefore, the flow returns to step (J-3), and the slow control is continued until the output increase / decrease pulse is output. For a predetermined time T
After a lapse of (for example, one minute), the control returns to the normal control. FIG. 9 is an electric system diagram of a system interconnection operation system using the third embodiment of the received power control device according to the present invention. 9, the same components as those of the embodiment shown in FIG. 3 are denoted by the same reference numerals, and the description will be omitted.

[0033] whether the received power control apparatus 10B of the embodiment is the received power P _r predetermined multiple of the absolute value of the dead zone width [Delta] P _db of the difference between the received power control amount P _c (multiple A) above And a control mode switching unit 14 that outputs a command to switch the control mode of the generator 5 from the normal control to the slow control when it is detected that the received power is equal to or more than the predetermined number. And an output increasing / decreasing means 15 for changing the output interval of the output increasing / decreasing pulse in accordance with the control mode switching command.

The control operation of the received power control device will be described with reference to FIG.

The received power _Pr is measured by the received power meter 4 (K-1), and the second received power value determining means 16
The measured received power _Pr and the received power control target value _Pc
Absolute value of the difference between the constant A times the dead zone width [Delta] P _db (A is for example, about 3) determines whether or (K-2). Constant A
If it is more than twice, it is determined that it is not related to hunting,
The control switching means 14 outputs a control command according to the normal control method (K-3), but if it is less than the constant A, it outputs a slow control command as a possibility of hunting (K-
4). When a normal control command is output, normal control is performed in which the output interval between the output increasing pulse and the output decreasing pulse is a short set time (for example, 4 seconds) (K-5). On the other hand, when the slow control command is output, the output interval of the slow control, that is, the output increasing pulse output from the output increasing / decreasing means 15 is set to be longer than before (K-6). The control operation of the generator 5 by the generator control device 20 is the same as in the embodiments described above.

FIG. 11 is an electrical diagram of a grid-connected operation system using a fourth embodiment of the received power control device according to the present invention. In FIG. 11, the same components as those in the above-described embodiment are denoted by the same reference numerals, and description thereof will be omitted.

[0037] In this embodiment, first the second received power value determination means 16, the absolute value of the dead zone width of the difference between the control target value P _c of the reception power P _r measured by the received power four received power it is determined whether (the a for example, about 3) a constant a times the [Delta] P _db or more, it is determined that is independent of the hunting if the constant a times, outputs a normal control command from the control mode changeover part 14 However, if it is less than the constant A, it is determined that hunting is possible and the hunting detecting means 13 detects the presence or absence of hunting. As the hunting detection method, the first detection method or the second detection method described with reference to FIG. 4 or FIG. 5 can be used. When hunting is detected by the hunting detecting means 13, a slow control command is output from the control mode switching means 14, and as a result, the output increasing / decreasing means 15 increases the output interval of the output increasing pulse to a value larger than the conventional one. A command and a decrease command are output. In response to the increase / decrease command, the generator control device 20 controls the generated power of the generator 5, but the control operation is the same as that of the above-described embodiment, and the description is omitted.

In the above-described embodiment, the slow control is described as the control in which the output interval of the output increase command is set to be larger than the output interval of the output decrease command. Even if the output interval for both is set to be longer than the output interval of the output increase / decrease command in the conventional control, that is, the normal control, the same or more effect can be obtained in terms of suppressing or eliminating hunting. You may think similarly to slow control.

Although a power receiving wattmeter is used to measure the power received from the commercial power supply, the present invention does not require that the received power value be visible and can be taken out as data. Transducers can also be used.

[0040]

As described above, according to the present invention,
Hunting is automatically resolved in a short time,
There is no need to keep a specialist engineer on standby for hunting or to send a technician to the site when hunting occurs to adjust the set values of the dead zone width and the output fluctuation amount.

As a method of detecting hunting, there is a method of detecting the presence or absence of hunting based on the number of times that a command for increasing or decreasing the output of the generator of the private power generation equipment is inverted from output increase to output decrease or from output decrease to output increase. There is a method of detecting the presence or absence of hunting based on the number of inversions when the power received from the commercial power system changes across a predetermined control target range (dead zone) within a predetermined time. According to the method, hunting can be detected with a smaller number of inversions than in the former method, so that hunting can be determined in a short time and control responsiveness can be improved.

[Brief description of the drawings]

FIG. 1 is an electric system diagram of a system interconnection operation system using a first embodiment of a received power control device according to the present invention.

FIG. 2 is a flowchart showing a control operation of the first embodiment of the received power control device shown in FIG. 1;

FIG. 3 is an electric system diagram of a system interconnection operation system using a second embodiment of the received power control device according to the present invention.

FIG. 4 is a flowchart illustrating a first hunting detection method.

FIG. 5 is a flowchart illustrating a second hunting detection method.

FIG. 6 is a flowchart showing one control operation of the second embodiment of the received power control device shown in FIG. 3;

FIG. 7 is a flowchart showing another control operation of the second embodiment of the received power control device shown in FIG. 3;

FIG. 8 is a flowchart showing still another control operation of the second embodiment of the received power control device shown in FIG. 3;

FIG. 9 is an electric system diagram of a system interconnection operation system using a third embodiment of the received power control device according to the present invention.

FIG. 10 is a flowchart showing one control operation of the second embodiment of the received power control device shown in FIG. 9;

FIG. 11 is an electric system diagram of a system interconnection operation system using a fourth embodiment of the received power control device according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Commercial power supply 2 Disconnector 3 Circuit breaker 4 Received power meter 5 Generator 10 Received power control device 11 First received power value determination means 12, 15 Output increase / decrease means 13 Hunting detection means 14 Control mode switching means 16 Second power reception Power value determination means 20 Generator control device 21 Governor 22 Actuator 23 Gas engine 24 Valve

Claims (12)

[Claims] In a system interconnection operation system for operating a private power generation system in connection with a commercial power supply system, it is determined whether or not electric power received from the commercial power supply system is outside a predetermined control target range (dead zone). A first received power value determining unit that performs output, and an output increasing and decreasing unit that outputs a command to increase or decrease the output of the generator of the private power generation facility when the power is outside the predetermined control target range. Is set to be larger than the output interval of the output reduction command. 2. In a system interconnection operation system for operating a private power generation system in connection with a commercial power supply system, it is determined whether or not electric power received from the commercial power supply system is outside a predetermined control target range (dead zone). A first received power value determining unit that performs output, and an output increasing / decreasing unit that outputs a command to increase or decrease the output of the generator of the private power generation facility when the output is outside the predetermined control target range. Is set larger than the output interval of the output increase / decrease command in the normal control mode. 3. A hunting detection means for detecting whether or not a generator of a private power generation facility is hunting, wherein the hunting detection means comprises: Control mode switching means for switching from the normal control mode to the slow control mode when it occurs, and outputting a command to increase or decrease the output of the generator, and outputting the output interval of the output increase command in the slow control mode to the output interval of the output decrease command. A receiving power control device, comprising: an output increasing / decreasing means for setting a larger value. 4. A hunting detecting means for detecting whether or not a generator of a private power generation facility is hunting, wherein the hunting detection means comprises: Control mode switching means for switching from the normal control mode to the slow control mode when it is occurring, and outputting a command to increase or decrease the output of the generator, and increasing or decreasing the output interval of the output increase or decrease command in the slow control mode in the normal control mode. An output increasing / decreasing unit that sets the output interval to be longer than a command output interval. 5. The hunting detecting means detects the presence or absence of hunting based on the number of times that the output increase / decrease command output from the output increase / decrease means is inverted from output increase to output decrease or from output decrease to output increase. The received power control device according to 3 or 4. 6. The hunting detecting means includes means for detecting an increase or decrease in an output output from the output increasing or decreasing means when power received from a commercial power supply system changes across a predetermined control target range (dead zone) within a predetermined time. 5. The received power control device according to claim 3, wherein the presence or absence of hunting is detected based on the number of reversals of the command from the output increase to the output decrease or from the output decrease to the output increase. 7. A system interconnection operation system for operating a private power generation system in connection with a commercial power supply system, wherein an absolute value of a difference between power received from the commercial power supply system and a predetermined control target value is a predetermined control target value. A second received power value determining means for determining whether or not the power is not less than a predetermined multiple of the range; a control mode switching means for switching from the normal control mode to the slow control mode when the power is not more than the predetermined power; An output increasing / decreasing unit that outputs an instruction to increase or decrease the output and sets an output interval of the output increase instruction to be larger than an output interval of the output decrease instruction in the slow control mode. 8. A system interconnection operation system for operating a private power generation facility in connection with a commercial power supply system, wherein an absolute value of a difference between electric power received from the commercial power supply system and a predetermined control target value is a predetermined control target value. A second received power value determining means for determining whether or not the power is not less than a predetermined multiple of the range; a control mode switching means for switching from the normal control mode to the slow control mode when the power is not more than the predetermined power; An output increasing / decreasing unit that outputs an instruction to increase / decrease the output, and sets an output interval of the output increasing / decreasing command in the slow control mode to be larger than an output interval of the output increasing / decreasing instruction in the normal control mode. 9. A system interconnection operation system for operating a private power generation facility in connection with a commercial power supply system, wherein an absolute value of a difference between electric power received from the commercial power supply system and a predetermined control target value is a predetermined control target value. A second received power value determining means for determining whether or not the hunting is not less than a predetermined multiple of the range; a hunting detecting means for detecting whether or not the generator of the private power generation facility is hunting when the power is not more than a predetermined multiple; Control mode switching means for switching from the normal control mode to the slow control mode when it occurs, and outputting a command to increase or decrease the output of the generator, and outputting the output interval of the output increase command in the slow control mode to the output interval of the output decrease command. A receiving power control device, comprising: an output increasing / decreasing means for setting a larger value. 10. A system interconnection operation system for operating a private power generation system in connection with a commercial power supply system, wherein an absolute value of a difference between electric power received from the commercial power supply system and a predetermined control target value is a predetermined control target value. The second to determine whether it is more than a predetermined multiple of the range
Receiving power value determining means, hunting detecting means for detecting whether or not the generator of the private power generation facility is hunting when the hunting is not more than a predetermined multiple, and switching from the normal control mode to the slow control mode when hunting is occurring Control mode switching means, and output increasing / decreasing means for outputting a command to increase / decrease the output of the generator, and setting the output interval of the output increasing / decreasing command in the slow control mode to be larger than the output interval of the output increasing / decreasing command in the normal control mode. A receiving power control device, comprising: 11. The hunting detection means detects the presence or absence of hunting based on the number of times the output increase / decrease command output from the output increase / decrease means is inverted from an increase in output to a decrease in output or from an decrease in output to an increase in output. The received power control device according to 9 or 10. 12. The hunting detecting means includes means for detecting an increase or decrease in the output output from the output increasing or decreasing means when the power received from the commercial power supply system changes across a predetermined control target range (dead zone) within a predetermined time. The received power control device according to claim 9 or 10, wherein the presence or absence of hunting is detected based on the number of reversals of the command from output increase to output decrease or from output decrease to output increase.