JPH04229024A - Reverse voltage detecting circuit for distributed power supply - Google Patents

Abstract

PURPOSE:To synchronize and facilitate setting of the disturbance frequency of effective power and the resonance frequency of a detecting filter and to detect system interruption reliably by correcting the phase shift of disturbance frequency during interlinked operation of a plurality of power supplies based on phase shift signals between the power supplies thereby regulating the detec tion level of frequency fluctuation optimally. CONSTITUTION:A reference clock is fed from an oscillator 114 through a frequency divider 115 to a detecting filter 104 as a resonance frequency set signal. Output from the frequency divider 115 is fed to a frequency divider 116 which then produces a disturbance frequency set signal (a). The signal (a) is also employed as a disturbance frequency set signal for a slave side power supply through a phase shifter 117.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reverse pressure detection circuit for detecting the occurrence of reverse pressure that occurs when a power system is interrupted in one or more distributed power sources connected to a power system.

0002

[Prior Art] Conventionally, power generated by distributed DC power generation systems such as solar power generation and fuel cell power generation has been
Distributed power sources are known that use an inverter to convert AC power into AC power and connect it to a power grid. If a system interruption occurs while this distributed power source is connected to a power system, the power supply will normally stop due to an abnormality in the system voltage. However, if matching with the load is achieved, the distributed power source maintains the voltage and continues to supply power to the load. In this case, the voltage from the distributed power supply continues to be generated on the grid side. This is called reverse pressure (reverse charging), and if such a situation occurs, there is a risk of unexpected situations such as electric shock during equipment safety maintenance. To avoid this, it is necessary to accurately detect system interruption and promptly stop the operation of the distributed power sources. As a reverse pressure detection circuit for this purpose, the inventor previously proposed the one shown in FIG.

In FIG. 8, 300 is an inverter that supplies alternating current power to a power system 400, and 200 is its control device, which constitute the main part of the distributed power source. On the other hand, 100' is a reverse pressure detection circuit, and this reverse pressure detection circuit 100' includes a system voltage detector 101,
A frequency/voltage converter 102, a notch filter 103, a detection filter 104 such as a bandpass filter, a comparator 105 that outputs a discrimination signal (reverse pressure detection signal) when detecting reverse pressure, and an active power command P* for the inverter 300. A disturbance generator 106 generates a disturbance command ±ΔP* of an appropriate period from
00. In order to detect system interruption or reverse pressure in the distributed power source configured as described above, the adder 107 applies a signal obtained by adding the disturbance command Δ±P* to the active power command P* to the inverter control device 200 and controls the inverter 300. The frequency fluctuation that is the same as the power disturbance frequency that occurs when the grid is cut off due to this, that is, the frequency fluctuation of the voltage, is transferred to the path of the frequency/voltage converter 102, notch filter 103, detection filter 104, and comparator 105. This is done by detecting the

0004

[Problem to be Solved by the Invention] When detecting a system interruption by the method described above, the active power command with disturbance P*
Two settings are required: the fluctuation frequency of ±ΔP*, that is, the disturbance frequency, and the frequency fluctuation extraction frequency, that is, the resonance frequency of the detection filter 104. In this regard, in the past, the disturbance frequency and the resonant frequency were each set individually, so when setting the disturbance frequency, the resonant frequency of the detection filter 104 had to be set individually, and the distributed power supply There was a problem in that it was difficult to reconfigure the system due to changes in system conditions after deployment. In addition, this method detects frequency fluctuations caused by power interference with other distributed power sources, but when multiple distributed power sources that use the same method to detect grid interruption are operated, the effective power Because each power source generates a disturbance independently, there is a problem in that it may be difficult to detect frequency fluctuations caused by system interruption depending on the state of the phase difference between the disturbance frequencies. The first and second inventions were made to solve the above problems, and their purpose is to facilitate the setting work by synchronizing the settings of the disturbance frequency of the active power and the resonance frequency of the detection filter. Moreover, when multiple distributed power sources are connected to each other, the phase shift of the disturbance frequency is corrected using a phase shift signal between each power source, and the frequency fluctuation detection level is optimally adjusted to reliably detect grid interruption. It is an object of the present invention to provide a reverse pressure detection circuit for a distributed power source that is possible.

The third invention has been made in view of the fact that in each of the above inventions, the disturbance frequency of the active power is set to a fixed optimum value determined by simulation etc. using an oscillator or the like. be. That is, the first
In the second aspect of the invention, if the system conditions change after the distributed power source is installed, the optimum value changes, so the amount of frequency fluctuation decreases. Further, when inverters that generate such active power disturbances are operated in parallel, if the phase of the disturbance is shifted, a mode occurs in which the disturbance components cancel each other out, and the amount of frequency fluctuation is reduced. For this reason, in each of the above-mentioned inventions as well, there is a risk that it will be difficult to detect a system interruption. Therefore, the third invention sweeps the active power disturbance frequency setting signal at a low frequency, thereby making it possible to more reliably shut down the grid without being affected by grid conditions, and even when multiple inverters are operated in parallel. It is an object of the present invention to provide a reverse pressure detection circuit for a distributed power supply that is capable of detecting reverse pressure.

Furthermore, in the conventional technique shown in FIG. 8, when the amount of frequency fluctuation exceeds a certain level, the path of the system voltage detector 101, frequency/voltage converter 102, notch filter 103 and detection filter 104 A blockage, or occurrence of back pressure, is detected. However, with this detection circuit, if large-capacity distributed power supplies are in the same system,
The amount of frequency fluctuation after a grid shutdown becomes smaller, and the difference from the amount of fluctuation that occurs during grid connection becomes smaller, making it difficult to accurately detect a system shutdown, as it may lead to malfunctions if only level discrimination is used. . Therefore, the fourth invention focuses on the sudden change in the amount of frequency fluctuation that occurs after the grid is shut off, and by adding the rate of change in the amount of frequency fluctuation as a criterion for determining the grid shutoff, it is possible to optimally detect the grid shutoff and the occurrence of back pressure. An object of the present invention is to provide a reverse pressure detection circuit for a distributed power source.

[0007]

[Means for Solving the Problems] In order to achieve the above object, a first invention provides a resonance frequency detection filter for setting a disturbance frequency of active power and extracting frequency fluctuations for detecting back pressure at the time of grid interruption. This is synchronized with the frequency setting so that the two settings can be adjusted simultaneously.

[0008] In addition to the first invention, the second invention provides a disturbance frequency setting signal that has a phase difference and is used as a disturbance frequency setting signal for another distributed power source, so that the disturbance command can be positioned. This enables interconnected operation of multiple distributed power sources with phase differences.

[0009] In order to achieve the above object, the third invention performs optimal detection of system interruption by sweeping the disturbance frequency setting signal at a low frequency.

[0010] According to a fourth aspect of the present invention, the frequency fluctuation detection unit includes means for determining the occurrence of back pressure based on the rate of change in the frequency fluctuation amount in addition to means for determining the back pressure from the level of the system frequency fluctuation amount. It is something that

[0011]

[Operation] According to the first invention, simply by setting the disturbance frequency of the active power, the resonance frequency of the detection filter for frequency fluctuation extraction is also set, so even if the system conditions etc. change after the power supply is installed, the resonant frequency can be reset. The work can be made easier, and the optimum disturbance frequency can be set in accordance with the characteristics of the distributed power sources connected in parallel.

According to the second invention, by generating disturbance commands having the same phase or different phases between a plurality of power supplies, a phase shift in disturbance frequency caused by system conditions is corrected.

According to the third invention, the optimal set value of the disturbance frequency that changes depending on the system conditions is periodically given to the frequency fluctuation detection section, and the phase difference of the active power disturbance of the power supplies operated in parallel becomes zero. To prevent cancellation of disturbance components by making it possible to generate a mode.

[0014] According to the fourth invention, the system is shut off or reversed based on the rate of change discrimination signal for detecting a sudden change in the amount of frequency fluctuation due to grid shutdown and the amount of change determination signal based on the level determination of the previous frequency fluctuation amount. Accurately detect pressure generation.

[0015]

[Embodiments] Examples of each invention will be described below with reference to the drawings. First, FIGS. 1 and 2 show embodiments of the first and second inventions, and this embodiment is for the case where a plurality of distributed power sources are operated in parallel. Note that FIG. 1 shows a reverse pressure detection circuit diagram of a distributed power source serving as a master, and FIG. 2 shows a reverse pressure detection circuit diagram of a distributed power source serving as a slave. These master side reverse pressure detection circuits 100A
The only difference between the master side reverse pressure detection circuit 100B and the slave side reverse pressure detection circuit 100B is the presence or absence of an oscillator, frequency divider, and phase shifter, which will be described later.The configuration of the master side reverse pressure detection circuit 100A will be described below.

The master-side reverse pressure detection circuit 100A is roughly divided into three blocks as shown. That is, 100a is a disturbance active power command generation unit that generates a disturbance active power command P*±ΔP* necessary for detecting a system interruption. In the generating section 100a, first, the active power command P* received from the inverter control device is sampled and held in the sample and hold circuit 108 using pulses of a certain appropriate period (disturbance period) from the monostable IC 109. The signal outputted here is attenuated to an appropriate value by an attenuator 110 with an attenuation rate of K, and this signal becomes ΔP*. Further, the above ΔP* is input to a switch 111 which is switched by a disturbance frequency setting signal with a duty of 50%, one output is directly input to an adder 112, and the other output is input to an inverter 113.
After inverting the sign, the signal is input to the adder 112. Through this process, active power disturbance commands +ΔP* and −ΔP* are alternately input to the adder 112 for each disturbance cycle. Then, by further adding the active power command P* in the adder 112, the adder 112 outputs the active power command with disturbance P*±ΔP*.

Next, reference numeral 100b in FIG. 1 is a frequency fluctuation detection section for detecting the frequency fluctuation of the grid voltage that occurs after the grid is cut off by the disturbance active power command P*±ΔP*. In this frequency fluctuation detection section 100b, as in the conventional case, first, the system voltage VCOM is detected by the frequency/voltage converter (F
/V converter) 102. Here, the output of the frequency/voltage converter 102 is a constant value because there is no fluctuation in the grid frequency before the grid is cut off, but after the grid is cut off, the grid frequency changes due to the exchange of power with other distributed power sources. happens. This fluctuation period coincides with the disturbance period. That is, after the system is cut off, a signal that fluctuates at the disturbance period is generated from the frequency/voltage converter 102. The system frequency component (DC component) and other components are removed from this signal by a notch filter 103, and the disturbance frequency component is detected using a detection filter 104 such as a bandpass filter that has the disturbance frequency component at its resonance point. Here, detection filter 10
4 uses a switched capacitor filter,
Its resonant frequency is set digitally. The level of the output signal of the filter 104 is determined by a comparator 10.
5 to determine whether the system is shut off.

Furthermore, 100c in FIG. 1 generates a disturbance frequency setting signal for the switch 111 of the disturbance active power command generating section 100a and a resonance frequency setting signal for the detection filter 104 of the frequency fluctuation detecting section 100b. A disturbance frequency setting signal to the reverse pressure detection circuit (see FIG. 2) of another distributed power supply (on the slave side) that has a master/slave relationship with this reverse pressure detection circuit 100A,
This is a setting signal sending unit that sends out a resonance frequency setting signal. In this setting signal sending section 100c, the reference clock generated from the oscillator 114 is transmitted to the frequency divider 1 whose frequency division ratio can be adjusted.
15, and is converted into a resonant frequency setting signal for the detection filter 104. Further, this signal is further frequency-divided by the next-stage frequency divider 116 with a fixed frequency division ratio, and this signal becomes the disturbance frequency setting signal a.

In this way, by using the signal using the same clock from the oscillator 114 as each setting signal for the disturbance frequency and the resonance frequency, it is possible to tune both the active power command generating section 100a with disturbance and the frequency fluctuation detecting section 100b. becomes. Furthermore, the disturbance frequency setting signal a is sent to the phase shifter 117.
By inputting the output signal to a predetermined part a of the reverse pressure detection circuit 100B (see FIG. 2) in the other distributed power source on the slave side, it is possible to In-phase or out-of-phase disturbance command ±ΔP
It becomes possible to generate *.

As described above, according to this embodiment, the frequency division ratio of the frequency divider 115 is adjusted by tuning the disturbance frequency setting of the disturbance active power command P*±ΔP* and the resonance frequency setting of the detection filter 104. It is possible to detect system interruption or reverse pressure simply by adjusting the disturbance frequency appropriately and setting the disturbance frequency, making it easy to set the optimum disturbance frequency that corresponds to the characteristics of multiple distributed power sources connected in parallel. be able to. In addition, the phase shift signal output from the phase shifter 117 after the frequency divider 116 is transmitted to the reverse pressure detection circuit 100B of the other distributed power source.
By passing it to , it is possible for each power supply to generate disturbance commands ±ΔP* with the same disturbance frequency and the same phase or different phases, correcting the phase shift of the disturbance frequency that occurs depending on the system conditions, and optimizing the detection level of frequency fluctuations. It becomes possible to make adjustments.

Next, FIG. 3 shows a third embodiment of the invention. In the first and second inventions described above, the original active power command P* generated by the inverter control device is changed at a constant period determined by the oscillator 114 and the frequency dividers 115 and 116 to obtain the active power disturbance command ±. Although it is added to the active power command P* as ΔP*, in the third invention, the configuration of the setting signal sending unit is changed in order to sweep the set value of the disturbance frequency of the active power at an appropriate cycle. It is.

That is, FIG. 3 shows an embodiment of the present invention, and components common to those in FIGS. 1 and 8 are given the same reference numerals. In FIG. 3, 118 in the disturbance active power command generation section 100a is a disturbance command generation unit, which includes, for example, the sample hold circuit 108, monostable IC 109, and attenuator 110 in FIG.
, the functions of the switch 111 and the inverter 113 are collectively shown. Further, 100c' is a setting signal sending section, and this setting signal sending section 100c' includes a low frequency oscillator 119 that obtains a triangular wave output, a sine wave output, etc. for setting the sweep period and sweep level, and this oscillator 11.
It consists of a voltage/frequency converter 120 that converts the level of the sweep signal output from 9 into a disturbance frequency setting clock, and a flip-flop 121 that shapes this setting pulse. It is input to the disturbance command generation unit 118 and the detection filter 104 as a disturbance frequency setting signal.

According to this embodiment, the low frequency oscillator 119
By sweeping the disturbance frequency setting signal using the voltage/frequency converter 120, it is possible to periodically provide the frequency fluctuation detection unit 100b with an optimum setting value that changes depending on the system conditions, and also to improve the effectiveness of the inverters operated in parallel. It is also possible to generate a mode in which the phase difference of power disturbances is zero. As a result, it is possible to reliably detect a system shutdown or the occurrence of back pressure by preventing a reduction in the amount of frequency fluctuation caused by a change in system conditions and canceling out the active power disturbance during parallel operation of inverters.

Next, FIG. 4 shows an embodiment of the fourth invention. In the first to third inventions, including the prior art shown in FIG. Since the level has been exceeded, the system has been shut down, that is, the occurrence of back pressure has been detected. However, according to this, when large-capacity distributed power sources are in the same system, the amount of frequency fluctuation after the grid is cut off becomes smaller, and the difference with the amount of fluctuation that occurs during grid connection becomes smaller, causing errors. This may lead to detection. Therefore, the fourth invention focuses on the sudden change in the amount of frequency fluctuation that occurs after the system is shut off, and adds the rate of change in the amount of frequency fluctuation to the level determination as a criterion for determining whether or not the system is shut off.

In FIG. 4, the same components as those in FIGS. 1 to 3 are designated by the same reference numerals, and a detailed description thereof will be omitted, and the following description will focus on the different parts. In FIG. 4, 100c'
′ is a setting signal sending section consisting of an oscillator, and the reference clock from this setting signal sending section 100c'' is sent as a disturbance frequency setting signal to the disturbance command generating unit 118 in the active power command generating section 100a with disturbance, and also to the resonance The signals are respectively applied as frequency setting signals to the detection filters 104 in the frequency fluctuation detection section 100b'. The output signal of this detection filter 104 is applied to a frequency fluctuation amount (Δf) change rate detection circuit 131. In addition, Δf change rate detection circuit 1
31, a plurality of timing signals are inputted from a timing generation circuit 132 described later, and the output signal of the Δf change rate detection circuit 131 is inputted to the Δf level determination circuit 133.
, and is further applied to the system cutoff determination signal processing circuit 134 as a change rate determination signal S1. Also, Δf
The output signal of the level discrimination circuit 133 is the fluctuation amount discrimination signal S2
This is added to the system cutoff determination signal processing circuit 134 as a signal processing circuit. Here, the system interruption determination signal processing circuit 134 is for accurately detecting system interruption from the change rate determination signal S1 and the fluctuation amount determination signal S2. Then, the output signal of the grid cutoff determination signal processing circuit 134 is transmitted to the inverter 30.
This signal is applied to the inverter control device 200 as a system cutoff (reverse pressure generation) determination signal for stopping the power supply.

FIG. 5 shows the configuration of the Δf change rate detection circuit 131, the timing generation circuit 132, and the Δf level discrimination circuit 133. First, the Δf change rate detection circuit 131
is a peak hold circuit 135 which receives the frequency fluctuation amount (Δf) and detects the peak value of Δf every cycle;
A sample hold circuit 136 that holds the detected value of the peak hold circuit 135 and a sample hold circuit 136 that holds the detected value of the peak hold circuit 135 and a certain sampling timing (
sample-and-hold circuits 137 and 138 that hold the output of the sample-and-hold circuit 136 at the next sampling timing (n+1), respectively; and a subtracter 1 that takes the difference between these outputs.
39, and a comparator 140 to which the output is added.
It consists of volumes 141 and 142 for setting the discrimination level of this comparator 140. The output of the comparator 140 is input as a Δf change rate determination signal S1 to a system cutoff determination signal processing circuit 134, which will be described later. Note that the operation timings of the peak hold circuit 135 and the sample hold circuits 136, 137, and 138 are controlled by the timing generation circuit 132.

The timing generation circuit 132 includes a monostable IC 143 to which a reference clock from the setting signal sending section 100c'' is applied, and a monostable I at the subsequent stage.
C144, a 1/2 frequency divider 145 to which the output signal of the setting signal sending section 100c'' is added, an inverter 146 to which the output signal is added, and the output signal of the 1/2 frequency divider 145 and the monostable IC 144. an AND circuit 147 to which the output signal of is added, and an AND circuit 14 to which the output signals of the NOT circuit 146 and the monostable IC 144 are added
It consists of 8. Here, monostable IC
The output signal of the AND circuit 144 is used as the timing signal TP1 of the peak hold circuit 135, the output signal of the monostable IC 143 is used as the timing signal TP2 of the sample and hold circuit 136, and the output signal of the AND circuit 147 is used as the timing signal TP3 of the sample and hold circuit 137. The output signal of the circuit 148 is sent to the sample and hold circuit 13.
8 timing signals TP4. The timing of these signals TP1 to TP4 is shown in FIG.
Shown below. In this FIG. 6, ΔP* is a disturbance command, fΔp
*/2 and its inverted signal are each 1/2 frequency divider 145
and the output of the negation circuit 146 are shown.

Referring again to FIG. 5, the Δf level discrimination circuit 1
33, a comparator 149 to which the output signals of the sample and hold circuits 137 and 138 are added; a negation circuit 150 connected to its output side; and a sample and hold circuit 13.
7,138, and is connected to the output side of comparator 1.
49 and an inverting circuit 150, a comparator 152 connected to the output side of this switch, and a volume 153 for setting the discrimination level. The output signal of the comparator 152 is input to the system cutoff determination signal processing circuit 134 as the fluctuation amount determination signal S2.

FIG. 7 shows the configuration of the system cutoff determination signal processing circuit 134. As shown in the figure, this processing circuit 13
Reference numeral 4 denotes an AND circuit 154 to which the rate of change discrimination signal S1 and the variation discrimination signal S2 are input, a monostable IC 155 to which the rate of change discrimination signal S1 is input, and an AND circuit to which the output thereof and the rate of change discrimination signal S1 are input. A circuit 156 and a monostable IC 15 to which the fluctuation amount determination signal S2 is input.
7, an AND circuit 158 to which its output and the variation determination signal S2 are input, and each AND circuit 154, 156, 15.
and an OR circuit 159 to which the output signal of No. 8 is input.

Next, the operation of this embodiment will be explained with reference to FIGS. 4 to 7. First, the frequency fluctuation amount of the grid (Δf
) is detected by the system voltage detector 101, frequency/voltage converter 102, notch filter 103, and detection filter 104 in the same manner as described above. This detection signal Δf is input to the Δf change rate detection circuit 131. In the Δf change rate detection circuit 131, the peak value of Δf for each cycle is detected by a peak hold circuit 135 that operates based on the timing signal TP1. This peak value is the timing signal TP2
The sample-and-hold circuit 136 operating at the same time holds the signal during the next period, and inputs the signal to sample-and-hold circuits 137 and 138, which update the signal every other period. As is clear from the timing signals TP3 and TP4 in FIG. 6, the operation timings of these sample and hold circuits 137 and 138 are shifted by one cycle, and by subtracting each hold value in a subtracter 139 every cycle, The rate of change in Δf can be detected. The comparator 140 determines whether this rate of change has exceeded a certain value, and the rate of change determination signal S
1 and is output to the system cutoff determination signal processing circuit 134. Note that the level of Δf is determined by a Δf level determination circuit 133.
The comparator 149, the switch 151, etc., select the larger one of the outputs of the sample and hold circuits 137, 138, and the comparator 1 determines whether the selected output is greater than the discrimination level determined by the volume 153.
This is done by making a determination based on 52.

The system cutoff determination signal processing circuit 134 determines the presence or absence of the change rate determination signal S1 and the variation amount determination signal S2 (“1
” or “0”). ■Case 1 (with fluctuation amount discrimination signal, change rate discrimination signal present) In this case, it is determined that the system has been shut down (reverse pressure has occurred), and the system is immediately determined to be shut off. Generate a signal (inverter stop signal). ■Case 2 (with fluctuation amount determination signal, no change rate determination signal) In this case, there is a possibility that a frequency fluctuation component within the system has been detected, so set it to monostable IC157. If the fluctuation amount determination signal is detected again within this time, a system cutoff determination signal is generated via the AND circuit 158 and the OR circuit 159. Case 3 (No fluctuation amount determination signal, (with change rate discrimination signal) Also in this case, similar to case 2 above, a waiting time T set in the monostable IC 155 is set, and if the change rate discrimination signal is detected again within this time, the AND circuit 1
56 and an OR circuit 159 to generate a system cutoff determination signal. ■Case 4 (No fluctuation amount discrimination signal, no change rate discrimination signal) In this case, the operation of the inverter 300 continues without outputting the system cutoff discrimination signal. The above operations are summarized in Table 1 below.

[0032]

[Table 1]

[0033]

[Effects of the Invention] As described above, according to the first invention, the disturbance frequency of the disturbance active power command P*±ΔP* is appropriately set in the setting signal sending unit to match the characteristics of the distributed power source. Moreover, the resonant frequency of the system cutoff detection filter can be set and adjusted just by the setting operation. Therefore, it is possible to simplify the setting work and improve the accuracy of system interruption detection.

According to the second invention, by adjusting the phase shifter of the setting pulse sending section, it is possible to adjust the phase difference of the disturbance command between the plurality of distributed power sources, and the detection level of frequency fluctuation can be adjusted. Optimally adjustable, grid interruptions can be detected more accurately.

According to the third invention, by sweeping the setting signal of the active power disturbance frequency using the output of the low frequency oscillator, the optimal value corresponding to changes in system conditions is periodically set as the active power disturbance command. This makes it possible to detect back pressure more reliably without being affected by power system conditions. In addition, it is possible to generate a mode in which the phase difference of the active power disturbances of the inverters operated in parallel is zero, thereby preventing cancellation of the disturbance component and detecting the optimum amount of frequency fluctuation.

According to the fourth invention, in addition to determining the level of the frequency fluctuation amount, a system interruption is detected by determining whether the rate of change exceeds a certain value. By detecting sudden changes, it is possible to accurately detect grid interruption or generation of back pressure even when the level of frequency fluctuation is small, and to improve detection accuracy.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a reverse pressure detection circuit on the master side in an embodiment of the first and second inventions.

FIG. 2 is a configuration diagram of a slave-side reverse pressure detection circuit in an embodiment of the first and second inventions.

FIG. 3 is a configuration diagram showing an embodiment of the third invention.

FIG. 4 is a configuration diagram showing an embodiment of the fourth invention.

FIG. 5 is a configuration diagram of main parts in FIG. 4;

FIG. 6 is an explanatory diagram of timing signals and the like.

FIG. 7 is a configuration diagram of a system cutoff determination signal processing circuit.

FIG. 8 is a configuration diagram showing a conventional technique.

[Explanation of symbols]

100A Master side back pressure detection circuit 100B Slave side back pressure detection circuit 100a Active power command generation section with disturbance 100b, 1
00b' Frequency fluctuation detection section 100c, 100c'
Setting signal sending unit 102 Frequency/voltage converter 103 Notch filter 104 Detection filter 105 Comparator 108 Sample hold circuit 109 Monostable IC 110 Attenuator 111 Switch 112 Adder 113 Inverter 114 Oscillator 115, 116 Frequency divider 117 Phase shifter 118 Disturbance command generation unit 119 Low frequency oscillator 120 Voltage/frequency converter 121 Flip-flop 131 Δf change rate detection circuit 132 Timing generation circuit 133 Δf level discrimination circuit 134 Grid cutoff discrimination signal processing circuit

Claims (4)

[Claims] 1. A reverse pressure state in which the device is connected to a distributed power source consisting of a distributed DC power generation system connected to an electric power system, and voltage is supplied from the distributed power source to a load when the power system is interrupted. The counter pressure detection circuit includes a disturbance active power command generation unit that forcibly changes an active power command for the distributed power source at a predetermined disturbance frequency, and a counter pressure detection circuit for detecting a disturbance generated when the power system is cut off. a frequency fluctuation detection section that detects the occurrence of back pressure from a frequency fluctuation that is the same as the disturbance frequency of the power supply voltage; and a setting signal transmission section that sets the disturbance frequency and the extraction frequency of the frequency fluctuation in the frequency fluctuation detection section. A reverse pressure detection circuit for a distributed power source, characterized in that the disturbance frequency setting signal and the extraction frequency setting signal are synchronized. 2. A reverse pressure state in which the device is connected to a distributed power source consisting of a distributed DC power generation system connected to an electric power system, and voltage is supplied from the distributed power source to a load when the power system is interrupted. a reverse pressure detection circuit for detecting a disturbance, the disturbance active power command generation unit forcibly varying an active power command for the distributed power source at a predetermined disturbance frequency; a frequency fluctuation detection unit that detects the occurrence of back pressure from a frequency fluctuation that is the same as the disturbance frequency of the generated power supply voltage; and a setting signal sending unit that sets the disturbance frequency and the extraction frequency of the frequency fluctuation in the frequency fluctuation detection unit. In the counter pressure detection circuit, the disturbance frequency setting signal and the extraction frequency setting signal are synchronized, and the disturbance frequency setting signal is transmitted to the disturbance frequency detection circuit in another counter pressure detection circuit by synchronizing the disturbance frequency setting signal and the extraction frequency setting signal. A reverse pressure detection circuit for a distributed power supply, characterized in that it sends out to an active power command generation section. 3. A reverse pressure state in which the device is connected to a distributed power source consisting of a distributed DC power generation system connected to an electric power system, and voltage is supplied from the distributed power source to a load when the power system is interrupted. The counter pressure detection circuit includes a disturbance active power command generation unit that forcibly changes an active power command for the distributed power source at a predetermined disturbance frequency, and a counter pressure detection circuit for detecting a disturbance generated when the power system is cut off. a frequency fluctuation detection section that detects the occurrence of back pressure from a frequency fluctuation that is the same as the disturbance frequency of the power supply voltage; and a setting signal transmission section that sets the disturbance frequency and the extraction frequency of the frequency fluctuation in the frequency fluctuation detection section. What is claimed is: 1. A reverse pressure detection circuit for a distributed power source, characterized in that the disturbance frequency setting signal is periodically swept in the reverse pressure detection circuit. 4. A reverse pressure state in which the device is connected to a distributed power source consisting of a distributed DC power generation system connected to an electric power system, and voltage is supplied from the distributed power source to a load when the power system is interrupted. The counter pressure detection circuit includes a disturbance active power command generation unit that forcibly changes an active power command for the distributed power source at a predetermined disturbance frequency, and a counter pressure detection circuit for detecting a disturbance generated when the power system is cut off. a frequency fluctuation detection section for detecting the occurrence of back pressure by determining the level of frequency fluctuation due to the same frequency fluctuation as the disturbance frequency of the power supply voltage; and for setting the disturbance frequency and the extraction frequency of the frequency fluctuation in the frequency fluctuation detection section. In the reverse pressure detection circuit comprising a setting signal sending section, the frequency fluctuation detection section is a distributed arrangement, characterized in that the frequency fluctuation detection section is provided with means for determining occurrence of reverse pressure based on the rate of change of the frequency fluctuation amount. Reverse pressure detection circuit for type power supply.