JP2645162B2 - Reverse pressure detection circuit for distributed power supply - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention detects power system separation in a power system to which a distributed power supply is connected, and detects the power system separation, and separates the power system. The present invention relates to a distributed-type power supply reverse pressure detection circuit used for disconnecting or stopping a distributed-type power supply connected to a power supply.

(Prior Art) FIG. 15 shows a conventional reverse voltage detection circuit of a distributed arrangement type power supply.

In this circuit, the DC power supply 1 as a power generation element
Connected to the DC input side of the inverter 2,
Is connected to a load 5 via a circuit breaker 4 and to a power system 6 via a circuit breaker 7, and the circuit breaker 7 and the receiver 3 are connected by a dedicated signal line 8.

The distributed power supply 10 includes a DC power supply 1, an inverter 2, a circuit breaker 4, and a receiver 3 among the above-described configurations. In such a circuit configuration, the circuit breaker 7 on the power system 6 side is opened. In the case where system separation occurs, a so-called reverse pressure state in which a voltage is supplied reversely from the distributed arrangement type power supply 10 to between the distributed arrangement type power supply 10 and the circuit breaker 7 may be a problem in the security of the power system. is there. Therefore, a signal notifying the opening of the circuit breaker 7 is transmitted to the receiver 3 via the dedicated signal line 8, the circuit breaker 4 is opened, and the distributed power supply 10 is disconnected or stopped.

(Problems to be Solved by the Invention) In such a conventional reverse pressure detection circuit, a system separation signal is received from a system separation point and system separation of the power system 6 is detected. There is a problem that equipment including a dedicated signal line 8 for transmitting a signal is required and the cost is high.

(Means for Solving the Problems) In order to solve this problem, in the first invention, the inverter is connected to the power system by slightly oscillating the AC output voltage phase of the power system interconnection inverter of the distributed arrangement type power supply. The active power to be supplied is fluctuated, and by monitoring this, the system separation is detected based on the fact that the fluctuation amount decreases after the system separation.

In the first invention, as means therefor, a first oscillator that oscillates at a frequency proportional to or approximately proportional to the generated power of a DC power supply that supplies DC power to the inverter;
By providing an active power setter that slightly increases or decreases the active power command value at a fixed ratio to the generated power and in synchronization with the first oscillator, the active power supplied from the inverter to the power system is reduced. Increase or decrease slightly.

Further, a second oscillator is provided which detects the active power and generates a pulse train having a frequency proportional to or approximately proportional to the value of the active power or an increase / decrease value thereof, synchronized with the oscillation cycle of the first oscillator; A counter is provided for adding or subtracting the number of pulse trains of the second oscillator in response to an instruction to increase or decrease the active power, and a value obtained as a result of one addition of the counter and subtraction from this value is a certain value. A determination circuit is provided for detecting the following and determining that the system is separated.

Further, in order to solve the above problem, in the second invention, the AC output voltage phase of the inverter for interconnecting the power system of the distributed arrangement type power supply is slightly fluctuated, thereby enabling the inverter to supply power to the power system. Fluctuate power. At this time, when interconnecting with a power system having an extremely large power capacity compared to the power generated by the distributed power source, the system frequency was kept substantially constant even if the amount of power supplied to the system by the inverter was changed. It is. On the other hand, when connected to other power sources such as a distributed power source or a generator having a power capacity not much larger than the power generated by the distributed power source, that is, when the power is not connected to the power system, the distributed power source is The system separation is detected based on the fact that the frequency of the interconnection point fluctuates according to the fluctuation of the active power supply amount supplied to another interconnection power supply.

Therefore, in the second invention, as a means therefor, there is provided an active power setter for slightly increasing or decreasing the active power supplied to the power system by the inverter in synchronization with the oscillator, and further comprising a connection point to which the inverter is connected. And a determination circuit for determining that the oscillation frequency component of the oscillator has fluctuated from the output of the frequency detector and determining system separation.

Here, in the back pressure detecting circuit according to the second aspect of the invention, only a single fluctuating frequency component equal to the inverter output fluctuating frequency is detected from the frequency of the system voltage. If a unique variation frequency equal to the variation frequency is included, there is a problem that even when the system is not separated, there is a possibility that the system separation is erroneously detected. In addition, since the power system generally includes a low-order frequency component unique to the equipment based on the control system of the equipment, there is a great risk that the frequency detector and the determination circuit will mistakenly identify the system as system separation.

Therefore, in order to solve the above problem, in the third invention, the inverter output fluctuation frequency is changed in an arbitrary pattern instead of being constant, and the frequency component detected by the frequency detector is also changed in synchronization with this. The determination circuit outputs a back pressure detection signal only when a variable frequency component is detected throughout the entire variation pattern.

That is, in the third invention, the second means
In the invention according to the invention, the oscillation frequency of the oscillator is changed in an arbitrary pattern, and a tuning frequency according to the oscillation frequency is made variable.

Further, in order to solve the above problem, in the fourth invention,
The power system interconnection inverter is provided with a function capable of outputting a waveform in which a sine wave voltage of the system frequency and a voltage waveform corresponding to the command are superimposed, and the first oscillator supplies the voltage waveform command to the inverter. Further, the oscillation frequency of the first oscillator is periodically changed in a predetermined frequency range according to the oscillation cycle of the second oscillator. On the other hand, the output current waveform of the distributed arrangement type power supply is detected, and the magnitude of the current component of the first oscillation frequency is extracted from the detected waveform by the frequency detector. The number of times that the magnitude of the detection value of the frequency detector exceeds a specified value for one frequency change of one oscillator is measured by a counter, and that the measured value is equal to or larger than a specified value is determined by a determiner. It is determined that the distributed power supply has been separated from the system.

Further, the fifth invention is made in view of the fact that the switch on the output side of the distributed arrangement type power supply is opened after the system is separated, and it is complicated to manually turn on the switch when the system is restored. The back pressure detection circuit detects back pressure generation and opens a switch on the output side of the distributed arrangement type power supply, and monitors the voltage on the power system side to determine the system A power recovery unit is provided which detects a power recovery after the separation and automatically closes the switch at the time of the power recovery to reconnect the power system and the distributed arrangement type power supply.

(Operation) The back pressure detection circuit according to the first invention slightly changes the AC output voltage phase (referred to the phase with respect to the voltage of the power system) of the inverter for power system interconnection of the distributed arrangement type power supply, and The active power setting unit as a means for slightly changing the active power, when monitoring the amount of change in the active power supplied to the system and detecting system separation based on the fact that the amount of change decreases after system separation, A value proportional to or approximately proportional to the generated power is output so that the amount of the small fluctuation can be increased or decreased according to the magnitude of the generated power of the DC power supply.

On the other hand, as a method of monitoring the variation, the difference between the active power when the active power is increased and the active power when the active power is decreased is calculated by the second oscillator and the counter, and the variation of the active power is grasped. At this time, the first integration time is changed so that the calculated value of each active power amount at the time of increase and at the time of decrease becomes substantially constant regardless of the magnitude of the minute fluctuation of the active power.
Oscillator works. As a result, the determination amount of the active power amount becomes a substantially constant value. As a result, the accuracy of the determination of the power system separation is improved, and the fluctuation range of the power consumption of the DC power supply is constant, so that the DC power supply can be easily stabilized.

A reverse pressure detection circuit according to a second aspect of the invention changes an AC output voltage phase (referred to as a phase difference with respect to a power system or another power supply voltage) of an inverter for interconnecting a power system of a distributed arrangement type power supply with a slight change. Changes the active power supplied to the power system or another power source, the voltage frequency at the grid connection point becomes almost constant at the natural frequency of the power system during grid connection, but the power of the distributed At the time of interconnection with another power supply that is not much larger than the capacity, that is, at the time of disconnection from the power system, the frequency of the voltage at the interconnection point fluctuates according to the fluctuation of the active power supply amount of the distributed arrangement type power supply. Therefore, the active power supply amount of the distributed arrangement type power supply is periodically changed by an oscillator oscillating at a specific frequency. further,
An oscillation frequency component of the oscillator is extracted by a frequency detector having the same frequency filtering characteristics as the oscillation frequency of the oscillator.
Here, when the distributed arrangement type power supply is connected to the grid, a signal associated with the frequency component of the oscillator is not detected in the output of the frequency detector, but when disconnected, a signal associated with the frequency component of the oscillator is detected. Therefore, whether the amount of detection is large or small is determined by a determination circuit, and detection of system non-connection, that is, so-called reverse pressure detection is performed.

The back pressure detecting circuit according to a third aspect of the present invention is configured such that, in the second aspect, when an oscillator whose output is applied to the active power setter and the frequency detector is a first oscillator, an output of the second oscillator for generating a disturbance pattern is provided. Is applied to the first oscillator, whereby the oscillation frequency of the first oscillator fluctuates within a certain range with the oscillation period of the second oscillator. The tuning frequency of the frequency detector changes according to the oscillation frequency of the first oscillator.

Therefore, while a first oscillator whose oscillation frequency fluctuates in a certain pattern, the active power supply of the distributed arrangement type power supply is periodically fluctuated, while a tuning frequency changes according to the oscillation frequency of the first oscillator. To detect the oscillation frequency component of the first oscillator. Here, when the distributed arrangement type power supply is in the grid connection, the frequency of the voltage at the grid connection point is substantially constant at the natural frequency of the power grid, and therefore the output of the frequency detector includes the fluctuating frequency of the first oscillator. No signal associated with the component is detected. On the other hand, when the system is disconnected, the inverter output fluctuating frequency component is tuned and detected by the frequency detector throughout the fluctuation pattern of the fluctuating frequency. Output.

Therefore, even if a low-order frequency component unique to the power system is normally included, the present invention does not detect only a single variable frequency component but detects a plurality of variable frequency components within a certain range. In addition, when the systems are not separated, it is possible to prevent erroneous detection as system separation.

Further, in the back pressure detection circuit according to the fourth invention, since the transmission line constituting the power supply system is apparently a distributed constant line as shown in FIG. 10, the impedance Zs of the transmission line viewed from the dispersed arrangement type power supply side is reduced. Attention is paid to the fact that there are local maximum values and local minimum values at a plurality of frequencies (in FIG. 10, 9 is a transmission line, 30 is a load circuit, 301 to 304 are line inductances, and 401 to 403 are line static values. Capacitance, 501 is resistance, 5
02 is a reactor and 503 is a capacitor). Thus, as an output power waveform of the distributed arrangement type power supply, a function capable of superimposing a voltage waveform in accordance with a command on the sine wave voltage of the conventional system frequency on the sine wave is given to the inverter constituting the power supply, A voltage waveform command to be superimposed on the inverter is supplied from the first oscillator. Here, when the oscillation frequency of the first oscillator is changed, as shown in FIG. 11, at a frequency at which the impedance Zs of the transmission line has a minimum value, the output current of the frequency from the distributed power supply flows to the system side most frequently. On the other hand, at a frequency at which the impedance Zs has a maximum value, the output current value at that frequency becomes minimum. In addition, since there are relatively many values of the frequency at which the maximum value and the minimum value of the current value occur, a resonance circuit or the like is connected to the load circuit of the distributed arrangement type power supply as shown in FIG. Even if there is a frequency band in which a large current flows, the number is sufficiently smaller than the number of the current maximum values of the transmission line.

Therefore the oscillation frequency of the first oscillator, the frequency range f _T as rich as possible frequency to produce a current maximum value as shown in FIG. 11 is selected, within the frequency range in accordance with the oscillation period of the second oscillator The oscillation frequency of the first oscillator is changed periodically. As a result, the current of the frequency component of the first oscillator having a large current value appears periodically in the output current of the distributed arrangement type power supply, and the frequency detector detects the oscillation frequency component of the first oscillator. Extract the size of the component. From the extracted values, the second
A counter counts the number of times that the detected value exceeds a specified value over one oscillation period of the oscillator, that is, the number of times the current has a maximum value or a minimum value.

When the distributed arrangement type power supply is interconnected, that is, connected to a transmission line, there are many current maximums and minimums as shown in FIG. On the other hand, in the unconnected state, the transmission line is generally cut off near the power receiving side of the long-distance transmission line, and the transmission line connected to the distributed power source becomes extremely short. frequency band that shows a minimum is shifted to the high frequency side, resulting current in the frequency fluctuation range f _T as Figure 12 is maximum, the number of times that the extremely small decreases rapidly. As described above, since the output of the counter is reduced, it is possible to easily determine the disconnection of the system, and to disconnect or stop the distributed power supply from the system.

Further, the reverse pressure detecting circuit according to the fifth aspect of the present invention detects a power return on the system side due to circuit breaker reclosing from a subsequent change in the system voltage, in addition to the reverse pressure detecting operation at the time of system separation, and turns on the switch. Then, it acts to perform automatic re-connection between the grid and the distributed power supply.

(Example) Hereinafter, the present invention will be described with reference to the drawings.

FIG. 1 is a system configuration diagram of a distributed arrangement type power supply to which a reverse pressure detection circuit according to the first invention is applied. In the figure, a DC power supply 1 is connected to a DC input side of an inverter 2, and an AC output side of the inverter 2 is connected to a power system 6 via a circuit breaker 4. Further, a power detector 13 and an active power detector 12 are connected to the DC input side and the AC output side of the inverter 2, respectively, and the detection signal lines thereof are connected to the reverse pressure detection circuit 11. A control signal line is connected to the inverter 2 and the circuit breaker 4 from the reverse pressure detection circuit 11.

In such a circuit configuration, the reverse pressure detection circuit 11 gives a small change command of the power supplied from the inverter 2 to the power system to the inverter 2, and further detects the small change amount by the active power detector 12 and the like. The result is determined, and if it is determined that the system is separated, the circuit breaker 4 is opened or the inverter 2 is stopped.

FIG. 2 is a control block diagram of one embodiment of the back pressure detecting circuit according to the first invention.

In the figure, a generated power value P of a DC power source as a power generation element
^* Is input to the active power setting device 101 and the first oscillator 108. The first oscillator 108 oscillates with a square waveform having a frequency proportional to or approximately proportional to the generated power value P ^* , and its output is input to the active power setter 101 and the up / down counter command input of the up / down counter 106. You.

Active power setter 101, in synchronization with the oscillation of the first oscillator 108, slight variation of a percentage of the generated power value P ^* delta
An active power command added and subtracted by P, that is, P ^*
+ ΔP and P ^* −ΔP are output. The third example of the waveform
This is shown in FIG. Active power command value and active power detector 12
Is input to the controller 102 and its output is input to the inverter 2 to form a control loop 300 for adjusting the active power of the inverter.

On the other hand, the output active power P of the inverter is equal to the second oscillator
The pulse is input to 105 and oscillates at a frequency proportional to the value of P or approximately proportional to the amount of small fluctuation of P, and outputs a pulse train. This pulse train is input to the count input of the up / down counter 106. Up-down counter 106 is the first
In synchronization with the up / down command of the oscillator 108, the up count is performed when the command value of the active power setting device 101 is P ^* + ΔP, and the down count is performed when the command value is P ^* −ΔP.
The operation waveform of the counter 106 at the time of system interconnection is shown by b in FIG. As is apparent from FIG.
The value (ΔX) of the result of one up-down count of
An almost constant value is obtained regardless of the value of the generated power P ^* .

By the way, at the time of system separation, the active power of the inverter hardly changes even if the active power command P ^* ± ΔP is given, so that the output of the active power detector 12 becomes almost constant. The down count value (ΔX) becomes almost 0. From the above, the judgment circuit 10
7 determines system separation based on whether the counter value is approximately 0 or ΔX after one up / down counting of the counter. Here, as described above, it is clear that the reliability of the operation of the determination circuit 107 is improved by making the value of ΔX substantially constant without being affected by the magnitude of the generated power P ^* .

FIG. 4 is a system configuration diagram of a distributed arrangement type power supply to which the reverse pressure detection circuit according to the second invention is applied. In the figure, a distributed power supply 10 includes a DC power supply 1, an inverter 2, a circuit breaker 4, a reverse pressure detection circuit 11, and an active power detector 12.
The DC power supply 1 is connected to a DC input side of an inverter 2, and an AC output side of the inverter 2 is connected to a power system 6 via a circuit breaker 4 and a circuit breaker 7. Further, a power detector 13 and an active power detector 12 are connected to the DC input side and the AC output side of the inverter 2, and this detection signal line is connected to the reverse pressure detection circuit 11, and a system voltage (voltage waveform) signal The line is also connected to the back pressure detection circuit 11. On the other hand, a control signal line is connected from the reverse pressure detection circuit 11 to the inverter 2 and the circuit breaker 4. Further, another distributed power supply 20 and a load circuit 30 are connected to a system to which the distributed power supply 10 is connected.

In such a circuit configuration, the reverse pressure detection circuit 11 gives the inverter 2 a periodic fluctuation command of the power supplied from the inverter 2 to the system (such as the power system 6 and the load circuit 30),
Further, the periodic fluctuation of the frequency of the system voltage is detected, and based on the detection result, if the system is separated (that is, the circuit breaker 7 is opened).
If determined to be, the circuit breaker 4 is opened or the inverter 2 is stopped.

FIG. 5 is a control block diagram of one embodiment of the back pressure detecting circuit according to the second invention.

In the figure, the output active power command value P ^* of the distributed arrangement type power supply 10 determined according to the power generated by the DC power supply as a power generation element is input to the active power setting device 101. The output of the generator 103 is input to the active power setter 101 and, if necessary, the frequency detector 104. Active power setting device 101 is oscillator 103
Outputs active power command value simply by adding or subtracting a constant ratio of the change amount [Delta] P ^* for in synchronization with the oscillation power generation command value P ^* ie P ^{* +} [Delta] P ^* and P ^* -ΔP ^*. Examples of the waveforms are shown in FIGS. 6a1 and a2. The specified active power value (P ^* + ΔP ^* , P ^* −ΔP ^* ) and the detection value (P + ΔP, P−ΔP) of the active power detector 12 are input to the controller 102, and the output thereof is input to the inverter 2 and the inverter 2 A control loop 300 for adjusting the active power of the device is configured.

On the other hand, a system voltage waveform is input to the frequency detector 104, from which the oscillation frequency component of the oscillator 103 is extracted and output. This output value is input to the determination circuit 107, and if it is determined that the oscillation frequency component has exceeded a certain level, a back pressure detection signal is output. In such a circuit configuration, when the power system is connected to the system to which the distributed arrangement type power supply is connected (when the system is connected), the effective output power of the distributed arrangement type power supply is ± Δ with respect to its average value P ^* .
When changing only P ^* , the phase difference θ between the output voltage of the distributed arrangement type power supply and the power system voltage is changed by ± Δθ, as shown in FIGS. Since it can be regarded as constant, the frequency of the distributed arrangement type power supply changes only slightly as shown in FIG. 6 c1.

On the other hand, when the power system is cut off from the system to which the distributed power supply is connected and is in a linked state with other power supply devices (when the system is not linked), the active power is compared with its average value P ^* as described above. When changing by ± ΔP ^* , FIGS. 6a2 and b2
As shown in (1), the phase difference θ between the output voltage of the distributed arrangement type power supply and the system voltage is changed by ± Δθ. At this time, the change amount ΔP of the active power flows into another distributed arrangement type power supply connected to the same system, but each distributed arrangement type power supply tries to cancel the change amount ΔP. The frequency of the voltage is changed so as to decrease ± Δθ. Therefore, as shown in FIG. 6 c2, the frequency of the system greatly changes in synchronization with the fluctuation period of the active power change (± ΔP).

With respect to the change in the operating frequency, the frequency component of the change is extracted by the frequency detector 104, and it is determined by the determination circuit 107 that the output has exceeded a certain level, and a back pressure detection signal is output.

FIG. 7 is a control block diagram of one embodiment of the back pressure detecting circuit according to the third invention. This reverse pressure detection circuit is the same as the reverse pressure detection circuit according to the second aspect of the present invention shown in FIG. 5 except that the input side of the first oscillator 103 connected to the active power setting device 101 and the frequency detector 104 This is configured by connecting two oscillators 202. Here, the second oscillator 202 is for generating a disturbance pattern, and the oscillation frequency of the first oscillation 103 can be changed within a predetermined range by the oscillation frequency of the second oscillator 202.

Also in this embodiment, the output active power command value P ^* of the distributed arrangement type power supply 10 determined according to the generated power of the DC power supply as the power generation element is input to the active power setting device 101.
The output of the first oscillator 103 is input to an active power setting device 101 and a frequency detector 104, and the active power setting device 101
3 in synchronism with the oscillation output active power command value simply by adding or subtracting the change amount [Delta] P ^* of constant ratio i.e. P ^{* +} [Delta] P ^* and P ^* -ΔP ^* for power generation command value P ^*. Then, the specified active power value (P ^* + ΔP ^* , P ^* −ΔP
^* ) And the detection values of the active power detector 12 (P + ΔP, P−Δ
P) is input to the controller 102, and its output is
To form a control loop 300 for adjusting the active power of the inverter 2.

Further, a system voltage waveform is input to the frequency detector 104, and the oscillation frequency component of the first oscillator 103 is extracted from the voltage waveform and output. This output value is output to the determination circuit 107
And if it is determined that the oscillation frequency component has exceeded a certain level, a back pressure detection signal will be output.

In such a circuit configuration, when a power system is connected to a system to which the distributed arrangement type power supply is connected (when the system is connected), the effective output power of the distributed arrangement type power supply is averaged by an average value P ^*.
Is changed by ± ΔP ^* , the phase difference θ between the output voltage of the distributed arrangement type power supply and the power system voltage is changed by ± Δθ as in the embodiment according to the second invention. Can be regarded as almost constant, the frequency of the distributed power supply changes only slightly, and the frequency detector 104
Does not detect a signal associated with the variable frequency component of the first oscillator 103.

On the other hand, when the power system is cut off from the system to which the distributed power supply is connected and is in a linked state with other power supply devices (when the system is not linked), the active power is compared with its average value P ^* as described above. When changing by ± ΔP ^* , an attempt is made to change the phase difference θ between the output voltage of the distributed arrangement type power supply and the system voltage by ± Δθ. At this time, the change amount ΔP of the active power flows into another distributed arrangement type power supply connected to the same system, but each distributed arrangement type power supply tries to cancel the change amount ΔP. The frequency of the voltage is changed so as to decrease ± Δθ. Therefore, the frequency of the system voltage greatly changes in synchronization with the fluctuation period of the active power change (± ΔP).

At the same time, the oscillation frequency of the first oscillator 103 also fluctuates according to a certain pattern, and the inverter output fluctuation frequency component (system voltage fluctuation frequency component) is synchronously detected by the frequency detector 104 throughout this fluctuation pattern. Therefore, if it is detected by the determination circuit 107 that the frequency component has exceeded a certain level, it is determined that the system is separated, and a back pressure detection signal is output.

For this reason, even if there is always an effective lower-order frequency component due to the control system of the equipment connected to the power system, the present invention does not detect only a single variable frequency component. Since a plurality of fluctuating frequency components within the range are detected, it is possible to eliminate the inconvenience of being erroneously recognized as system separation despite being linked to the system.

FIG. 8 is a system configuration diagram of a distributed arrangement type power supply to which the reverse pressure detection circuit according to the fourth invention is applied. In the figure, a distributed power supply 10 includes a DC power supply 1, an inverter 2, a circuit breaker 4, a reverse pressure detection circuit 11, and a current detector 14. DC power supply 1
Is connected to the DC input side of the inverter, the AC output side of the inverter 2 is connected to another distributed power supply 20 and the load circuit 30 via the circuit breaker 4, and the power is further connected via the circuit breaker 7 and the transmission line 9. Connected to system 6. A current detector 14 is connected to the AC output side of the inverter 2, and a detection signal line thereof is connected to the reverse pressure detection circuit 11.
, A control signal line is connected to the inverter 2. In such a circuit configuration, the back pressure detecting circuit 11 is
, A voltage waveform command to be superimposed on the output voltage of the inverter 2 is given, and the output current waveform of the inverter 2 is detected. If it is determined that the system is separated, that is, the circuit breaker 7 is opened, the circuit breaker 4 is opened. And the inverter 2 is stopped.

FIG. 9 shows a control block diagram of one embodiment of the back pressure detecting circuit according to the fourth invention. In FIG. 9, the adder 605 adds the output of the sine wave signal circuit 604 that outputs the output voltage waveform command of the inverter and the output of the first oscillator 201 that generates a waveform to be superimposed on the output voltage of the inverter. The output of the adder 605 and the output signal of the modulation signal circuit 603 are input to the pulse distribution circuit 602, and after being subjected to pulse width modulation, are converted into drive signals for the respective switching elements of the inverter 2,
It is supplied to the inverter unit 601. Therefore, the inverter unit 6
The output voltage waveform of 01 is a voltage waveform in which a similar waveform of the output waveform of the first oscillator 201 is superimposed on a sine wave voltage of the system frequency required for the original system linking.
And applied to the load circuit 30. The output current waveform of the inverter unit 601 is detected by the current detector 14 and input to the band-pass filter circuit 203.

By the way, the output signal of the second oscillator 202 is supplied to the filter circuit 203 and the first oscillator 201, and the same value is given to the oscillation frequency of the first oscillator 201 and the pass frequency band of the filter circuit 203. . Therefore, the filter circuit 20
The magnitude of the current component of the oscillation frequency of the first oscillator 201 is detected from the output of (3). As shown in FIGS. 11 and 12, the oscillation frequency fc of the first oscillator 201 changes the range from f _T1 to f _T2 with the oscillation cycle of the second oscillator 202, so that the output | Is | Increases and decreases according to fc. Further, the output of the filter circuit 203 and the output of the second oscillator 202 are input to the counter 204, and one oscillation of the second oscillator 202, that is, the oscillation frequency fc of the first oscillator 201 becomes f.
_The number of times that the output value of the filter circuit 203 has become equal to or more than the specified value Is ^* when changing from _T1 to _fT2 once is counted. In general, when the transmission line 9 is connected to the output side of the inverter 2, as shown in FIG. 11, and when the transmission line 9 is disconnected, as shown in FIG. In the state, the count value of the counter 204 is different. The output of the counter 204 is input to a determiner 205, which determines the difference between the count values and outputs a back pressure detection signal.

Next, FIG. 13 shows an embodiment of the fifth invention.
According to each of the above-described inventions, it is possible to reliably detect system separation and effectively prevent a distribution line or the like existing between the distributed power supply and the power system from being reversely charged at the time of system separation.

However, once the power output from the distributed power supply is once opened corresponding to the system separation, even if the power system side is restored due to the reclosing of the circuit breaker, it is provided on the output side of the distributed power supply. The switch is continuously left open. Therefore, in order to return to the original state, there is a problem that some kind of acquisition is required, such as manually turning on the switch in response to a report from the power system.

Therefore, in the fifth invention, the function of monitoring the rise of the power system side voltage at the output side of the distributed arrangement type power supply and turning on the power supply output side switch based on the logical judgment to reverse the function of re-linking with the power system. This is provided to the pressure detection circuit.

That is, in FIG. 13, reference numeral 11 'denotes a back pressure detecting unit configured similarly to the back pressure detecting circuit 11 in each of the above-described inventions. 40
Is connected. The reconnection system 40 is a distributed power supply
The voltage on the power system 6 side (the output voltage of the distributed power supply 10) is taken in from the line connecting the switch 4b inside the 10 and the circuit breaker 7 for interconnection, and the logic of the voltage with the output voltage of the reverse pressure detection unit 11 'is taken. The switch 4b is configured to be closed via the switch coil 4a according to the judgment. In addition, between the switch 4b and the circuit breaker 7 for interconnection, there is a distribution line 15 for preventing reverse charging at the time of system separation.
Is connected.

The configuration of the reconnection operation unit 40 will be described in detail below.The reconnection operation unit 40 includes a voltage detection circuit 41 that detects a system side voltage, a negation circuit 42, a delay circuit 46, and a A NOT circuit 43, a NOT circuit 44 connected to the output side of the back pressure detecting unit 11 ', and an AND circuit 4 to which outputs of the NOT circuits 43 and 44 are added.
7 and a delay circuit 45 connected to its output side,
The output of the delay circuit 45 is applied to the switch coil 4a.

Next, the operation of the reverse pressure detection circuit 11 will be described with reference to the timing chart of FIG.

First, interconnection with the power system by the operation of the breaker 7 at time t ₀ in FIG. 14 is cut off, after a reverse charge state,
At time td, the AND circuit is activated by the operation of the back pressure detecting section 11 '.
47, ie, the output of the delay circuit 45 becomes “0”, and the switch 4b is opened via the switch coil 4a. Note that during this time, the output of the voltage detection circuit 41 is “1” until time tv after time td.

Thereafter, at time tr, when the circuit breaker 7 is reclosed and the power distribution line 15 (system side voltage) is restored, the output of the voltage detection circuit 41, that is, the output of the negation circuit 43 also becomes "1". If the output of 11 'is "0", the output of the NOT circuit 44 maintains "1" and the output of the AND circuit 47 also becomes "1". Then, at time tc after a lapse of operation time period T ₄₅ of the delay circuit 45, the output also becomes "1" of the delay circuit 45, the switch 4b is closed via the switch coil 4a. That is, the distributed power supply 10 is automatically reconnected to the power system.

Incidentally, the operation time period T ₄₅ of the delay circuit 45, noise without switch 4b accidentally be penetrated is turned as shown in the figure No, also, by the operation time period T ₄₆ of the delay circuit 46, Even if noise such as Nc enters, it is not accidentally cut off. Here, between the operation time periods T ₄₅ and T ₄₆ , T ₄₅ >
There is a T ₄₆ relationship.

As described above, according to this embodiment, the switch 4b is closed when the system is restored, and the reconnection between the distributed power supply 10 and the power system 6 is automatically and reliably performed. The complexity of switching on the switch can be eliminated. Here, the configuration of the reconnection operation unit 40 is not limited to the illustrated one.

(Effect of the Invention) As described above, in the first invention, the active power of the AC output of the inverter for linking the power system of the distributed arrangement type power supply is slightly changed, and the amount of the change is reduced after the system is separated. based in the as a means for detecting a line separation, to the generator power P of the DC power source with the distributed power sources ^*, grasp the active power to be substantially proportional command fluctuation width of the effective power in the generated power P ^* Therefore, by integrating the output active power at the time of increase and the output active power at the time of decrease with a fluctuation cycle at a frequency substantially proportional to the generated power P ^* , the power amount after the integration is the generated power of the DC power supply. Almost constant regardless of the size of P ^* . For this reason, there is an effect that the accuracy of the determination for system separation can be improved and the determination circuit and the determination logic can be simplified. This effect is particularly large when the amount of generated power is small. That is, even if the fluctuation range of the power is small, the integration time is long, so that the power amount after the integration can be increased, and accordingly, the determination value ΔX can also have an appropriate value.

On the other hand, the power supplied from the power generation power source also fluctuates due to the operation of the detection circuit. However, since the fluctuating power amount can be kept almost constant, it is easy to take measures such as stabilization of the DC power supply voltage accompanying the fluctuation. It has the effect of smoothing out.

Also, as described above, in the second invention, the frequency of the AC output voltage after system separation is changed by periodically varying the AC output active power of the power system linking inverter of the distributed arrangement type power supply. The amount of the fluctuation is extracted by a frequency detector that periodically changes the frequency and filters the frequency component of the periodic fluctuation, and the occurrence of a so-called reverse pressure in the power system is detected from the magnitude of the fluctuation. This makes it possible to detect back pressure by the distributed arrangement type power supply itself, and furthermore, it is possible to set the fluctuation period of the active power to an arbitrary value. By setting them differently, highly accurate back pressure detection becomes possible.

Further, in the third invention, the oscillation frequency of the oscillator for periodically varying the AC output active power of the inverter is changed, and the oscillation frequency component of the oscillator is extracted from the system voltage to extract the oscillation frequency component of the oscillator. The tuning frequency of the frequency detector was made variable according to the frequency. As a result, it is possible to determine that the system is separated only when a plurality of fluctuating frequency components are detected from the system voltage, and it is possible to perform reliable and reliable back pressure detection regardless of system conditions. is there.

In the fourth invention, a voltage waveform whose frequency changes periodically is superimposed on the AC output voltage of the power system linking inverter of the distributed arrangement type power supply, and a harmonic current specific to the transmission line flowing from the inverter to the transmission line is obtained. The number of frequency bands is determined, and based on the decrease in the number, the occurrence of a so-called back pressure in the power system is detected. This makes it possible to detect the back pressure of the distributed power supply itself,
Even when combined with a distributed power supply, a generator and a load circuit, high-precision reverse pressure detection is possible because the presence or absence of the inherent harmonic current of the transmission line is directly monitored.

Further, according to the fifth aspect, the system-side voltage is constantly monitored by the re-connection operation unit, so that the system-side power is restored by the reclosing after the output side of the distributed power supply is opened due to the system separation. Can be detected, and the system can be quickly reconnected after power is restored without any intervention by a crowd.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram of a distributed arrangement type power supply to which a back pressure detection circuit according to the first invention is applied, FIG. 2 is a control block diagram of one embodiment of a back pressure detection circuit according to the first invention, and FIG. 2 is an operation waveform diagram of the embodiment shown in FIG. 2, FIG. 4 is a system configuration diagram of a distributed arrangement type power supply to which the reverse pressure detection circuit according to the second invention is applied, and FIG. 5 is a reverse pressure detection according to the second invention. FIG. 6 is a control block diagram of an embodiment of the circuit, FIG. 6 is an operation waveform diagram of the embodiment shown in FIG. 5, FIG. 7 is a control block diagram of an embodiment of the reverse pressure detection circuit according to the third invention, FIG. FIG. 10 is a block diagram of a distributed arrangement type power supply system to which a back pressure detection circuit according to the fourth invention is applied, FIG. 9 is a control block diagram of one embodiment of the back pressure detection circuit according to the fourth invention, and FIG. FIG. 4 is a circuit diagram showing a system to which a reverse pressure detection circuit according to the invention of claim 4 is connected and a circuit example;
11 and 12 are operation waveform diagrams of the embodiment shown in FIG.
FIG. 13 is a block diagram of one embodiment of a back pressure detecting circuit according to the fifth invention, FIG. 14 is a timing chart showing the operation thereof, and FIG.
FIG. 1 is a system configuration diagram of a conventional reverse pressure detection circuit. DESCRIPTION OF SYMBOLS 1 ... DC power supply 2 ... Inverter 4,7 ... Circuit breaker 4b ... Switch 6 ... Electric power system 9 ... Transmission line 10 ... Distributed arrangement type power supply 11 ... Back pressure detection circuit 11 ′… Back pressure detector, 12… Active power detector 13… Power detector, 14… Current detector 15… Distribution line, 20… Distributed arrangement type power supply 30 …… Load circuit, 40… Reconnection operation section 101 Active power setting device 102 Regulator 103, 105, 108, 201, 202 Oscillator 104 Frequency detector 106 Up / down counter 107 Judgment circuit 203 Bandpass filter circuit 204 Counter, 205: Judge 300: Control loop

Continued on the front page (72) Inventor Shigenori Matsumura 2-12-26 Uenomachi, Takamatsu City, Kagawa Prefecture (72) Inventor Ken Takemura 1-1-1, Tanabe Nitta, Kawasaki-ku, Kawasaki City, Kanagawa Prefecture Inside Fuji Electric Co., Ltd. 72) Inventor Toshihisa Shimizu 1-1, Tanabe-Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture Fuji Electric Co., Ltd.

Claims (5)

(57) [Claims] 1. A distributed arrangement type power supply for converting generated power of individually provided power generating elements into an AC output via an inverter, wherein the power generator oscillates at a frequency proportional to or approximately proportional to the generated power of the power generating elements. An active power setting device for increasing / decreasing an AC output active power command of an inverter according to the power generated by the power generating element at a fixed ratio and in synchronization with the oscillation cycle of the first oscillator; A second oscillator for generating a pulse train having a frequency proportional to or approximately proportional to the active power or an increase or decrease thereof, and a second oscillator that synchronizes with the oscillation cycle of the first oscillator and responds to an increase or decrease command of the active power. A counter for increasing and decreasing the number of pulse trains of the second oscillator, and a single addition,
A reverse pressure detection circuit for a distributed arrangement power supply, comprising: a determination circuit for determining that a subtraction result has become a certain value or less. 2. A distributed arrangement type power supply for converting power generated by a power generation element provided separately to AC power via an inverter, comprising: an oscillator oscillating at a specific frequency; and an inverter corresponding to the power generated by the power generation element. An active power setter for increasing / decreasing an AC output active power command at a fixed ratio and in synchronization with the oscillation cycle of the oscillator; and a frequency detector for extracting an oscillation frequency component of the oscillator from a system voltage to which the inverter is connected. And a determination circuit for determining the amount of detection from the frequency detector. 3. A distributed arrangement type power supply for converting generated power of individually provided power generating elements into AC power via an inverter, wherein an oscillator whose oscillation frequency is changed in an arbitrary pattern is provided; An active power setter that increases / decreases the AC output active power command of the inverter according to the generated power in a certain class and in synchronization with the oscillation cycle of the oscillator,
A frequency detector that changes a tuning frequency according to the oscillation frequency of the oscillator to extract an oscillation frequency component of the oscillator from a system voltage to which the inverter is connected, and a detection amount from the frequency detector is determined. A back pressure detecting circuit for a distributed arrangement power supply, comprising: a determination circuit. 4. A distributed arrangement type power supply for converting generated power of individually provided power generation elements into AC power via an inverter, wherein a sine wave signal circuit for outputting an output voltage waveform command of the inverter, and an oscillation frequency of A first oscillator for generating a periodically changing command waveform, a second oscillator for periodically changing the oscillation frequency of the first oscillator, and an output voltage of the inverter output from the sine wave signal circuit Adding means for adding a waveform command and a command waveform output from the first oscillator to form an addition signal for controlling the inverter; and an oscillation frequency component of the first oscillator based on an output current of the inverter. And a number of times that the magnitude of the detection value output from the frequency detector during one oscillation period of the second oscillator becomes equal to or greater than a specified value. A counter pressure detection circuit for a distributed power supply, comprising: a counter for counting; and a determiner for determining a count value from the counter. 5. A distributed power supply for converting the power generated by individually provided power generating elements into an AC output via an inverter and supplying the AC output via a switch to a power system to which a distribution line is connected. In the separation of the power system, a reverse pressure detection unit that detects a state in which voltage is supplied from the distributed arrangement type power supply to the distribution line to open the switch, and monitors the voltage on the power system side. A reconnection operation unit that detects power restoration after system separation from the change, automatically closes the switch at the time of the power restoration, and reconnects the power system and the distributed arrangement type power supply. A back pressure detecting circuit for a distributed arrangement type power supply, characterized in that: