JPH11136865A - System linked power supply equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to surely detect independent operation of a system linked power supply equipment even if a plurality of generators are link-operated by separating an inverter circuit and a commercial power system, and fluctuating the output current of the inverter circuit when it is judged that the commercial power system stops and the power supply equipment is independently operated. SOLUTION: A system linked power supply equipment is constituted of a power supply equipment 1, an inverter circuit 2, a commercial power system 3, a load 4, a voltage detecting means 5, and a system linked protective equipment 8 built up of an active fluctuation generating section 6 and an independent operation judging section 7. The system linked protective equipment 8 is provided with a random fluctuation outputting section 9 which adds random elements to the active fluctuation which fluctuates the output current of the inverter circuit 2. In the protective equipment, a random value is selected from various values in a specified range and then the output current is allowed to actively fluctuate at time intervals of the random value. In other words, in an active power fluctuation method wherein the output current of the inverter circuit 2 is fluctuated, the time intervals of the output current fluctuation is randomly changed, and in a reactive power method, the time intervals of the output phase fluctuation is randomly changed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grid-connected power supply used in connection with a commercial power grid.

[0002]

2. Description of the Related Art A conventional system interconnection power supply will be described with reference to FIG. FIG. 19 is a block diagram showing a conventional grid-connected power supply device.

[0003] A conventional grid-connected power supply includes a power supply 1
, Inverter circuit 2, commercial power system 3, load 4
, A voltage detecting means 5, an active fluctuation creating unit 6, an isolated operation judging unit 7, and a system interconnection protection device 8.

[0004] The power supply device 1 outputs DC power, such as a solar cell that converts the energy of sunlight into DC power. The inverter circuit 2 converts DC power supplied from the power supply device 1 into AC power and supplies a predetermined AC voltage. The commercial power system 3 supplies power to the load 4 in connection with the inverter circuit 2. The voltage detecting means 5 detects a voltage at a connection point between the inverter circuit 2 and the commercial power system 3. Active fluctuation generator 6
Changes the output current of the inverter circuit 2. The isolated operation determination unit 7 determines that the commercial power system 3 has stopped and is in the isolated operation state based on the voltage value of the interconnection point detected by the voltage detection unit 5. The grid connection protection device 8 is provided when the commercial power system 3 is stopped and the islanding operation determination unit 7 determines that the islanding operation state is established.
This is to separate the inverter circuit 2 from the commercial power system 3.

In the system interconnection power supply device as shown in FIG. 19, the output from the power supply device 1 is connected to the commercial power system 3 via the inverter circuit 2.

[0006] In this grid-connected power supply device, power is supplied from the commercial power system 3 such as when an accident occurs in the commercial power system 3 or when the commercial power system 3 is disconnected for maintenance work. Is stopped, if the private power generation system including the power supply device 1 and the inverter circuit 2 continues to operate independently, the transformer or the like of the commercial power system 3 is reversely charged, and the boosted high voltage is Since the voltage is applied to the power system 3 side, there is a danger that the worker receives an electric shock, an accident is damaged, the load 4 is damaged, or the like. For this reason, it is a very important problem to prevent the independent operation of the private power generation facility that occurs when the commercial power system 3 is opened or the like. Hereinafter, the conventional procedure will be described.

The system interconnection protection device 8 detects the independent operation of the private power generation facility including the power supply device 1 and the inverter circuit 2 and separates the private power generation facility from the commercial power system 3. In the grid connection protection device 8, the overvoltage detection function (○
V), an undervoltage detection function (UV), a frequency rise detection function (OF), and a frequency decrease detection function (UF), and two methods, a passive method and an active method, are used together.

The overvoltage detection function (検 出 V), the undervoltage detection function (UV), the frequency increase detection function (○ F), and the frequency decrease detection function (UF) correspond to the voltage and frequency generated when the above-mentioned independent operation state is established. Is to detect the change of However, the power relationship between the power output by the private power generation facility including the power supply device 1 and the inverter circuit 2 and the power consumption of the load 4 is completely balanced (the active power and the reactive power are also balanced).
Under special conditions, even if the supply of power from the commercial power system 3 is stopped, the voltage and frequency of the off-line locations are small in the amount of change, and the above-described function alone cannot detect the isolated operation of the private power generation facility. There are cases.

Therefore, a passive system and an active system described later are used together. The passive method is a method for detecting a sudden change in a voltage phase, a frequency, or the like at the time of transition to the islanding operation, and generally has a feature of being excellent in high speed. This method includes a voltage phase jump detection method, a third harmonic voltage distortion sharp increase detection method, a frequency change rate detection method, and the like.

The voltage phase jump detection method is a method for detecting a sudden change in the voltage phase due to imbalance between the power generation output and the load 4 at the time of transition to the islanding operation, and it is possible to increase the detection sensitivity. If the active power and the reactive power of No. 4 are completely balanced, islanding may not be detected. The third harmonic voltage distortion sharp increase detection method is a method for detecting that the columnar transformer is excited by the power generation output during the transition to the isolated operation and the third harmonic voltage increases rapidly. Although it is not affected, it cannot be applied to a three-phase circuit having no imbalance or a voltage-controlled inverter. The frequency change rate detection method is a method for detecting a sudden change in frequency due to imbalance between the power generation output and the load 4 at the time of transition to the islanding operation, and can increase the detection sensitivity. If the connected power sources are interconnected, the islanding phenomenon may not be detected.

In the active system, the voltage and frequency output from the inverter circuit 2 are constantly varied by a control system of the inverter or a resistor added externally. Is a method of detecting Although this system is excellent in that there is no dead zone region in principle, it may not operate effectively if a number of private power generation facilities employing other active systems are interconnected to the same system. This method includes a frequency shift method, an active power fluctuation method, a reactive power fluctuation method, and the like.

The frequency shift method is a method of applying a frequency bias to an internal oscillator or the like of the inverter and detecting a frequency change appearing at the time of transition to the islanding operation. If the system is connected to the grid, if the direction of the frequency shift of the private power generation equipment is not matched during the islanding operation, the islanding operation may not be detected if it is changed by chance in the same cycle in the opposite direction. There is. The active power fluctuation method is a method in which periodic power fluctuations are given to the power generation output and periodic voltage fluctuations, current fluctuations or frequency fluctuations appearing during the transition to the islanding operation are detected. When the equipment is connected to the same system, it is necessary to match the active power fluctuation cycle and phase of the private power generation equipment during the single operation. The reactive power fluctuation method is a method in which a periodic reactive power fluctuation is given to the power generation output and periodic frequency fluctuations or current fluctuations appearing during the transition to the islanding operation are detected. When connected to the grid, it is necessary to match the reactive power fluctuation cycle and phase of the private power generation equipment during islanding operation.

At present, as functions of the system interconnection protection device 8, an overvoltage detection function (（V) and an undervoltage detection function (U
V), the frequency increase detection function (ＦF), the frequency decrease detection function (UF), the passive system, and the active system are both used to increase the detection probability of islanding.

[0014]

However, in the system interconnection power supply employing the active system as described above, when the private power generation equipment employing the same system is interconnected to the same system, each of the active systems is switched. There has been a problem that a state in which the private power generation equipment employed interferes with each other and the isolated operation cannot be detected occurs.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to connect a plurality of power generators adopting an active system on the same wiring at the time of system disconnection. It is an object of the present invention to provide a grid-connected power supply device that can avoid an undetectable state due to the influence of the output of another private power generation facility and can reliably detect an isolated operation even during operation.

[0016]

According to the first aspect of the present invention,
A power supply device for outputting DC power such as a solar cell, an inverter circuit for converting DC power output from the power supply device to AC power, a commercial power system interconnecting the inverter circuit and supplying power to a load, and an inverter The voltage detecting means for detecting the voltage at the interconnection point between the circuit and the commercial power system, and the commercial power system is stopped based on the voltage value at the interconnection point detected by the voltage detecting means, and is in an independent operation state. An independent operation determination unit that determines that the inverter is operating, an active fluctuation creating unit that varies the output current of the inverter circuit, and an inverter that determines that the commercial power system has stopped and is in an isolated operation state. A system interconnection protection device that separates the circuit from the commercial power system and a random variation output unit that provides a random element to an active variation creation unit that varies the output current of the inverter circuit And it is characterized in and.

According to a second aspect of the present invention, in the system interconnection power supply according to the first aspect, the random variation output unit includes:
The present invention is characterized in that the time interval of active fluctuation for fluctuating the output current of the inverter circuit is randomly changed within a certain range.

According to a third aspect of the present invention, in the grid-connected power supply according to the first aspect, the random variation output unit includes:
The method is characterized in that the time interval of the active variation for fluctuating the output current of the inverter circuit is changed so that the frequency of occurrence of the variation increases as the isolated operation determination unit determines that the value is closer to the criterion of the isolated operation. is there.

According to a fourth aspect of the present invention, in the grid-connected power supply according to the first aspect, the random variation output section includes:
The present invention is characterized in that the time width of the active fluctuation for changing the output current of the inverter circuit is randomly changed within a certain range.

According to a fifth aspect of the present invention, in the grid-connected power supply according to the first aspect, the random variation output unit includes:
It is characterized in that the time width of the active fluctuation for fluctuating the output current of the inverter circuit is changed so that the frequency of occurrence of the fluctuation increases as the islanding operation judging unit judges the numerical value closer to the judgment standard of the islanding operation. is there.

According to a sixth aspect of the present invention, in the grid-connected power supply according to the first aspect, the random variation output unit includes:
It is characterized in that the magnitude of the variation of the active variation that varies the output current of the inverter circuit is randomly changed within a certain range.

According to a seventh aspect of the present invention, in the system interconnection power supply according to the first aspect, the random variation output unit includes:
The magnitude of the fluctuation amount of the active fluctuation that fluctuates the output current of the inverter circuit is changed so that the frequency of occurrence of the fluctuation increases as the islanding operation judging unit judges the numerical value closer to the criterion of the islanding operation. Things.

According to an eighth aspect of the present invention, in the system interconnection power supply according to the first aspect, the random variation output unit includes:
The present invention is characterized in that at least two or more of the time interval, the time width, and the magnitude of the variation of the active variation for varying the output current of the inverter circuit are randomly changed within a certain range.

According to a ninth aspect of the present invention, in the grid-connected power supply according to the first aspect, the random variation output unit includes:
The more the at least two or more of the time intervals, time widths, and the magnitudes of the fluctuations of the active fluctuations that fluctuate the output current of the inverter circuit are determined to be close to the standard for the single operation, the more the fluctuation occurrence frequency increases. It is characterized by being changed so as to rise.

According to a tenth aspect of the present invention, in the grid-connected power supply according to the eighth or ninth aspect, the random variation output unit determines a time interval, a time width, and a variation amount from a predetermined range of random values. At least two or more of the sizes are randomly changed.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A grid-connected power supply according to the present invention will be described below in detail with reference to FIGS. The same parts as those of the system interconnection power supply shown in FIG. 19 described in the related art are denoted by the same reference numerals, and detailed description thereof will be omitted.

FIG. 1 is a block diagram showing a system interconnection power supply device. FIG. 2 is a block diagram showing another system interconnection power supply device. FIG. 3 is an explanatory diagram showing an example of an active fluctuation occurring at random time intervals. FIG. 4 is an explanatory diagram showing an example of an active fluctuation occurring at a random time width. FIG. 5 is an explanatory diagram illustrating an example of an active fluctuation occurring at a random size. FIG. 6 is an explanatory diagram illustrating an example of active fluctuations occurring at random time intervals and random time widths. FIG. 7 is an explanatory diagram illustrating an example of an active fluctuation occurring at a random time width and a random size. FIG. 8 is an explanatory diagram illustrating an example of an active fluctuation occurring at a random time width and a random size. FIG. 9 is an explanatory diagram illustrating an example of active fluctuations occurring at random time intervals, random time widths, and random magnitudes. FIG. 10 is an explanatory diagram showing an example of an active fluctuation occurring at a random time interval and a random time width based on a certain random value. FIG. 11 is an explanatory diagram showing an example of an active fluctuation occurring at a random time interval and a random magnitude based on a certain random value. FIG. 12 is an explanatory diagram showing an example of an active fluctuation occurring at a random time width and a random size based on a certain random value. FIG. 13 is an explanatory diagram illustrating an example of an active fluctuation occurring at a random time interval, a random time width, and a random size based on a certain random value. FIG. 14 is an explanatory diagram showing the relationship between the generated random value and the time interval, time width, and magnitude of the active fluctuation. FIG. 15 is an explanatory diagram showing the relationship between the possibility of occurrence of islanding and the random time interval of active fluctuation. FIG. 16 is an explanatory diagram showing the relationship between the possibility of occurrence of islanding and the random time width of active fluctuation. FIG. 17 is an explanatory diagram showing the relationship between the possibility of occurrence of islanding and the random magnitude of active fluctuation. FIG.
8 is an explanatory diagram showing a relationship between the possibility of occurrence of an islanding operation and a random time interval, a random time width, and a random size of active fluctuation, and (a) shows a relationship between the possibility of occurrence of an islanding operation and a random value. It is an explanatory view, and (b) is an explanatory view showing the relation between the generated random value and the time interval, time width, and magnitude of the active fluctuation.

[First Embodiment] FIGS. 1 and 2 are block diagrams showing a system interconnection power supply device.

This system interconnection power supply comprises a power supply 1 and
It includes an inverter circuit 2, a commercial power system 3, a load 4, a voltage detection unit 5, an active fluctuation creating unit 6, an isolated operation determining unit 7, and a grid connection protection device 8.

Further, the grid interconnection protection device 8 includes a random fluctuation output section 9 for adding a random element to the active fluctuation for fluctuating the output current of the inverter circuit 2. By the random fluctuation output unit 9, for example, a random value is selected from a certain range of numerical values, and as shown in FIG.
Actively fluctuates at the time interval of the random value.

That is, in the system interconnection power supply device shown in FIG. 1, the output time interval of the fluctuation itself by the conventional active system is randomly changed. That is, in the active power variation method in which the magnitude of the output current of the inverter circuit 2 is varied, the time interval of the variation in the magnitude of the output current is randomly changed.
In the reactive power fluctuation method in which the output phase is changed, the time interval of the output phase change is changed randomly.

Further, in the system interconnection power supply device shown in FIG. 2, the output time interval of the variation itself of the conventional active system or a variation different from that of the conventional active system is randomly changed. That is, a frequency shift method in which the frequency value of the output current of the inverter circuit 2 is obtained by adding a small amount of shift value to the frequency value of the voltage detection means 5 detected last time, a frequency variation having a more random time interval. This is an additional configuration.

The random variation output unit 9 may select a random value from a certain range of numerical values, and may actively vary within a time width of the random value as shown in FIG.

That is, in the system interconnection power supply device shown in FIG. 1, the output time width of the fluctuation itself by the conventional active system may be changed at random. That is, in the active power variation method in which the magnitude of the output current of the inverter circuit 2 is varied, the time width of the variation in the magnitude of the output current may be changed randomly, or the output of the inverter circuit 2 may be varied. In the reactive power fluctuation method in which the phase is changed, the time width of the output phase change may be changed randomly.

Further, in the system interconnection power supply device shown in FIG. 2, the output time width of the variation of the conventional active system or the variation different from that of the conventional active system may be changed randomly. . In other words, a frequency shift method in which the frequency value of the output current of the inverter circuit 2 is obtained by adding a minute shift value to the frequency value of the voltage detection means 5 detected last time, a frequency variation having a more random time width is used. An additional configuration may be adopted.

Further, a random value may be selected from a certain range of numerical values by the random fluctuation output unit 9 so as to be actively varied according to the magnitude of the variation of the random value as shown in FIG. .

That is, in the grid-connected power supply device shown in FIG. 1, the magnitude of the fluctuation itself by the conventional active system may be changed randomly. That is,
In the active power variation method in which the magnitude of the output current of the inverter circuit 2 is varied, the magnitude of the output current may be varied randomly,
In the reactive power variation method of varying the output phase of the above, the magnitude of the variation of the output phase may be randomly changed.

Further, in the system interconnection power supply device shown in FIG. 2, the magnitude of the fluctuation itself of the conventional active system or the amount of fluctuation different from that of the conventional active system is changed randomly. Is also good. In other words, the frequency shift method in which the frequency value of the output current of the inverter circuit 2 is obtained by adding a small shift value to the frequency value of the voltage detection means 5 detected last time has a more random fluctuation amount. You may make it the structure which adds a frequency fluctuation.

According to the present embodiment, since the active fluctuation output from the private power generation equipment fluctuates at random rather than at a periodic constant fluctuation, a plurality of private power generation equipment is provided on the same wiring when the system is disconnected. Even in the case of the interconnected operation, the undetectable state due to the influence of the output of the other private power generation equipment is avoided, and the isolated operation can be reliably detected.

The random fluctuation output unit 9 selects a random value from a constant numerical value for each of two or more items of the time interval, the time width, the magnitude of the fluctuation amount, etc. for generating the active fluctuation. Active fluctuation may be output based on a random value.

For example, as shown in FIG. 6, a value of a random time interval is determined from a certain range of numerical values, and a value of a random time width is determined from a certain range of numerical values. You may make it output.

As shown in FIG. 7, a value of a random time interval is determined from a certain range of numerical values, and a value of a random fluctuation amount is determined from a certain range of numerical values. Active fluctuations may be output.

As shown in FIG. 8, a value of a random time width is determined from a certain range of numerical values, and a value of a random fluctuation amount is determined from a certain range of numerical values. Active fluctuations may be output.

Further, as shown in FIG. 9, a value of a random time interval is determined from a certain range of numerical values, and a value of a random fluctuation amount is determined from a certain range of numerical values. Alternatively, a value of the magnitude of the random fluctuation amount may be determined from a certain range of numerical values, and the active fluctuation may be output.

Further, as shown in FIGS. 10 to 13, for the items of the time interval, the time width, and the magnitude of the amount of fluctuation which are the targets of the fluctuation of the active fluctuation, values are randomly selected from a certain range of numerical values. Then, one or more active fluctuations out of the time interval, the time width, and the magnitude of the fluctuation amount may be derived from the random value by a preset arithmetic expression or the like, and the active fluctuation may be generated based on the derived formula.

Further, a value is randomly selected from a certain range of numerical values, and FIG.
As shown in (1), the relationship between the random value and the time interval, the time width, and the magnitude of the variation may be determined in advance, and at least one or more active variations may be determined. That is, in FIG. 14, when the random value is 2, it has a time width of four cycles at a time interval of once every 25 cycles.
The active fluctuation of 25% (1/4) of the magnitude of the fluctuation is output.

[Second Embodiment] FIG. 15 shows an active fluctuation generator 6 of the grid-connected power supply shown in FIG. 1 or FIG.
5 shows the selection range of the random time interval shown in FIG. 3 created by the random variation creation unit 9 of the grid-connected power supply shown in FIG. The range of the random time interval is determined by the isolated operation determination unit 7 of the grid-connected power supply device shown in FIGS.
In FIG. 3, the random time interval in FIG. 3 is shortened so that the closer the voltage value of the interconnection point detected by the voltage detecting means 5 to the islanding determination criterion, the more frequently the random fluctuation occurs.

As shown in FIG. 16, the range of the random time width is determined by the isolated operation judging section 7 of the grid-connected power supply shown in FIGS. The selection range of the random time width in FIG. 4 may be extended so that the closer the value is to the single operation determination criterion, the higher the frequency of occurrence of random fluctuations.

Also, as shown in FIG. 17, the range of the magnitude of the random variation is determined by the isolated operation determination unit 7 of the grid-connected power supply shown in FIGS. As the voltage value at the point approaches the islanding judgment criteria,
The selection range of the magnitude of the random variation amount in FIG. 4 may be increased so that the frequency of occurrence of the random variation increases.

According to the present embodiment, the frequency of occurrence of random fluctuations can be reduced in the case of interconnected operation, so that a decrease in the output power factor of the private power generation equipment caused by the output of the random fluctuations can be reduced. As well as being possible, if the possibility of islanding increases, the frequency of random fluctuations can be increased, so that the accuracy of islanding detection can be increased.

It is to be noted that at least two or more of the time interval, the time width, and the magnitude of the variation amount of the active variation may be varied based on the selection range described above.

Also, as shown in FIG. 18A, the range of the random time width is such that the islanding operation judging section 7 of the grid-connected power supply shown in FIGS. , For example, to make the value of the random value larger,
As shown in FIG. 18B, at least two of the time interval, the time width, and the magnitude of the variation may be determined from predetermined values so that the frequency of occurrence of the variation increases. In other words, when the random value is 2, an active fluctuation having a time width of two cycles and a fluctuation amount of about 11% (1/9) of the normal value is output at a time interval of once every 28 cycles. Therefore, active fluctuation occurs in two or more of these items.

[0053]

As described above, according to the first aspect of the present invention, a power supply device for outputting DC power, such as a solar cell,
An inverter circuit that converts DC power output from the power supply into AC power, a commercial power system that supplies power to the load in connection with the inverter circuit, and a voltage at a connection point between the inverter circuit and the commercial power system. A voltage detecting means for detecting, an isolated operation determining unit for determining that the commercial power system is stopped and in an isolated operation state based on the voltage value of the interconnection point detected by the voltage detecting means, and an output of the inverter circuit; An active fluctuation generator that fluctuates current, and a system interconnection protection device that disconnects the inverter circuit and the commercial power system when the isolated operation determination unit determines that the commercial power system has stopped and is in an isolated operation state. And an active fluctuation generating section for fluctuating the output current of the inverter circuit, and a random fluctuation output section for giving a random element to the active fluctuation generating section. Since the dynamic change varies randomly,
Even when multiple power generators adopting the active method are connected and operated on the same wiring during grid disconnection, undetectable states due to the influence of the output of other private power generation equipment can be avoided and reliable. In addition, there is an effect that it is possible to provide a grid-connected power supply device capable of detecting islanding operation.

According to the second aspect of the present invention, the first aspect is provided.
In the grid-connected power supply device described above, the random fluctuation output unit randomly changes the time interval of the active fluctuation that fluctuates the output current of the inverter circuit within a certain range. Is randomly changed, so that even when a plurality of power generators adopting the active method are connected and operated on the same wiring at the time of system disconnection, isolated operation can be reliably detected. It works.

According to the third aspect of the present invention, a first aspect is provided.
In the described grid-connected power supply device, the random variation output unit determines that the time interval of the active variation that fluctuates the output current of the inverter circuit is such that the isolated operation determination unit determines that the time interval is closer to the determination criterion of the isolated operation. Since the occurrence frequency is changed so as to increase, during normal operation, by reducing the occurrence frequency of the random fluctuation, it is possible to reduce the decrease in the output power factor of the inverter circuit caused by the output of the random fluctuation, If possible, increase the frequency of random fluctuations to ensure that even if multiple generators employing the active method are connected to the same wiring during grid disconnection, This has the effect that islanding can be detected.

According to the fourth aspect of the present invention, there is provided the first aspect.
In the above described grid-connected power supply device, the time width of the active fluctuation output from the inverter circuit is randomly varied within a certain range by the random fluctuation output unit, so that the time width of the active fluctuation output from the inverter circuit is varied. Is randomly changed, so that even when a plurality of power generators adopting the active method are connected and operated on the same wiring at the time of system disconnection, isolated operation can be reliably detected. It works.

In the invention according to claim 5, claim 1 is
In the described grid-connected power supply device, the random fluctuation output unit determines the time width of the active fluctuation that fluctuates the output current of the inverter circuit as the isolated operation determination unit determines that the time width is closer to the criterion of the isolated operation. Since the occurrence frequency is changed so as to increase, during normal operation, by reducing the occurrence frequency of the random fluctuation, it is possible to reduce the decrease in the output power factor of the inverter circuit caused by the output of the random fluctuation, If possible, increase the frequency of random fluctuations to ensure that even if multiple generators employing the active method are connected to the same wiring during grid disconnection, This has the effect that islanding can be detected.

In the invention according to claim 6, claim 1 is
In the system interconnection power supply described above, the random fluctuation output section randomly changes the magnitude of the active fluctuation that fluctuates the output current of the inverter circuit within a certain range, so that the active fluctuation output from the inverter circuit is output. Since the magnitude of the fluctuation amount fluctuates at random, even when multiple power generators employing the active method are connected to the same There is an effect that it can be detected.

In the invention according to claim 7, claim 1 is
In the grid-connected power supply device described above, the random variation output unit determines that the magnitude of the fluctuation amount of the active fluctuation that fluctuates the output current of the inverter circuit is a value close to the criterion for the single operation. , The frequency of occurrence of fluctuations is increased so that during normal operation, by reducing the frequency of occurrence of random fluctuations, it is possible to reduce the decrease in the output power factor of the inverter circuit caused by the output of random fluctuations, and If there is a possibility of driving, increase the frequency of random fluctuations,
Even when a plurality of power generators adopting the active method are connected and operated on the same wiring at the time of system disconnection, the independent operation can be reliably detected.

According to the invention of claim 8, claim 1 is
In the above described grid-connected power supply device, at least two or more of the active fluctuation time interval, time width, and fluctuation amount that fluctuate the output current of the inverter circuit are randomized within a certain range by the random fluctuation output unit. Since the active fluctuation output from the inverter circuit fluctuates at random, even when a plurality of power generators adopting the active method are operated on the same wiring at the time of system disconnection, the operation is interconnected. This has the effect that islanding can be detected more reliably.

According to the ninth aspect of the present invention, the first aspect is provided.
In the grid-connected power supply device described above, the independent operation determination unit independently determines at least two or more of the active fluctuation time interval, the time width, and the magnitude of the fluctuation amount that fluctuates the output current of the inverter circuit by the random fluctuation output unit. It is characterized in that the change occurrence frequency is changed so that the closer the value is to the driving reference, the higher the fluctuation occurrence frequency. If it is possible to reduce the decrease in the output power factor of the inverter circuit caused by the output of random fluctuation, and if there is a possibility of islanding,
By increasing the frequency of occurrence of random fluctuations, it is possible to reliably detect islanding even when multiple generators employing the active method are connected to the same wiring when the grid is disconnected. It has the effect of being able to do so.

According to a tenth aspect of the present invention, in the grid-connected power supply according to the eighth or ninth aspect, the random variation output unit converts the time interval, the time width and the time interval from a random number within a certain range. Since at least two or more of the magnitudes of the fluctuation amounts are changed at random, the number of occurrences of random values can be reduced, so that it is possible to reduce the computational burden in controlling the grid interconnection protection device. It has the effect of becoming.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a system interconnection power supply device.

FIG. 2 is a block diagram showing another system interconnection power supply device.

FIG. 3 is an explanatory diagram illustrating an example of active fluctuation occurring at random time intervals.

FIG. 4 is an explanatory diagram illustrating an example of an active fluctuation occurring at a random time width.

FIG. 5 is an explanatory diagram illustrating an example of active fluctuation occurring at a random size.

FIG. 6 is an explanatory diagram showing an example of active fluctuations occurring at random time intervals and random time widths.

FIG. 7 is an explanatory diagram illustrating an example of an active fluctuation occurring at a random time width and a random size.

FIG. 8 is an explanatory diagram illustrating an example of an active fluctuation occurring at a random time width and a random size.

FIG. 9 is an explanatory diagram illustrating an example of an active fluctuation occurring at a random time interval, a random time width, and a random size.

FIG. 10 is an explanatory diagram illustrating an example of an active fluctuation occurring at a random time interval and a random time width based on a certain random value.

FIG. 11 is an explanatory diagram illustrating an example of an active fluctuation occurring at a random time interval and a random magnitude based on a certain random value.

FIG. 12 is an explanatory diagram illustrating an example of an active fluctuation occurring at a random time width and a random size based on a certain random value.

FIG. 13 is an explanatory diagram illustrating an example of an active fluctuation occurring at a random time interval, a random time width, and a random size based on a certain random value.

FIG. 14 is an explanatory diagram showing a relationship between a generated random value and a time interval, a time width, and a magnitude of active fluctuation.

FIG. 15 is an explanatory diagram showing a relationship between a possibility of occurrence of an islanding operation and a random time interval of active fluctuation.

FIG. 16 is an explanatory diagram showing the relationship between the possibility of occurrence of islanding and the random time width of active fluctuation.

FIG. 17 is an explanatory diagram showing a relationship between the possibility of occurrence of islanding and the random magnitude of active fluctuation.

FIG. 18 is an explanatory diagram showing a relationship between the possibility of occurrence of an islanding operation and a random time interval, a random time width, and a random size of active fluctuation, and (a) shows a relationship between the possibility of an islanding operation and a random value; (B) is an explanatory diagram showing a relationship between a generated random value and a time interval, a time width, and a magnitude of an active fluctuation.

FIG. 19 is a block diagram showing a conventional grid-connected power supply device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Power supply device 2 Inverter circuit 3 Commercial power system 4 Load 5 Voltage detection means 6 Active fluctuation creation part 7 Single operation judgment part 8 Grid connection protection device 9 Random fluctuation output part

Claims (10)

[Claims] 1. A power supply device for outputting DC power such as a solar cell, an inverter circuit for converting DC power output from the power supply device to AC power, and a commercial power supply connected to the inverter circuit to supply power to a load. The power system, the voltage detection means for detecting the voltage at the interconnection point between the inverter circuit and the commercial power system, and the commercial power system is stopped based on the voltage value at the interconnection point detected by the voltage detection means, and the isolated operation is performed. The islanding operation determining unit that determines that the state is in the state, the active fluctuation creating unit that varies the output current of the inverter circuit, and the islanding operation determining unit determines that the commercial power system is stopped and is in the state of islanding. In this case, a system interconnection protection device that separates the inverter circuit from the commercial power system and a random fluctuation output that gives a random element to the active fluctuation generator that fluctuates the output current of the inverter circuit And a grid-connected power supply device. 2. The grid-connected power supply according to claim 1, wherein the random fluctuation output section randomly changes a time interval of active fluctuation for fluctuating the output current of the inverter circuit within a certain range. 3. The frequency of occurrence of the fluctuation increases as the time interval of the active fluctuation for fluctuating the output current of the inverter circuit is determined by the random fluctuation output unit to be a value closer to the criterion of the single operation. The grid-connected power supply device according to claim 1, wherein the power supply is changed as follows. 4. The grid-connected power supply according to claim 1, wherein the random fluctuation output section randomly changes the time width of the active fluctuation for fluctuating the output current of the inverter circuit within a certain range. 5. The frequency of occurrence of the fluctuation increases as the time width of the active fluctuation for fluctuating the output current of the inverter circuit is determined by the random fluctuation output unit to be a value closer to the criterion of the single operation. The grid-connected power supply device according to claim 1, wherein the power supply is changed as follows. 6. The system interconnection according to claim 1, wherein the random fluctuation output section randomly changes the magnitude of the fluctuation of the active fluctuation which fluctuates the output current of the inverter circuit within a certain range. Power supply. 7. The more the random operation output unit determines the magnitude of the fluctuation amount of the active fluctuation that fluctuates the output current of the inverter circuit to a value closer to the criterion for the single operation, the more the fluctuation occurs. 2. The system interconnection power supply according to claim 1, wherein the frequency is changed so as to increase. 8. A method for randomly changing at least two or more of a time interval, a time width, and a magnitude of a fluctuation amount of an active fluctuation which fluctuates an output current of an inverter circuit within a predetermined range by a random fluctuation output unit. The grid-connected power supply according to claim 1, characterized in that: 9. The islanding operation determining unit determines at least two or more of the time interval, the time width, and the magnitude of the amount of variation of the active variation for varying the output current of the inverter circuit by the random variation output unit. The system interconnection power supply according to claim 1, wherein the change occurrence frequency is changed so as to be closer to the value. 10. A random fluctuation output unit for randomly changing at least two or more of a time interval, a time width, and a magnitude of a fluctuation amount from a random numerical value in a certain range. Item 10. The grid-connected power supply device according to Item 9.