CN1021531C - Measuring circuit of system separation for disperse disposition type of power source - Google Patents

Abstract

The present invention relates to a decentralized power supply including a power generating element and an inverter for converting the power generated by the generating element into an alternating current. According to the present invention, the predetermined signal is superimposed at the AC output of the converter, and the signal after superimposing the predetermined signal is taken out according to the signal on the AC output side of the converter, and according to the taken out signal, at the output of the converter The end side detects whether the circuit breaker of the connected power system is disconnected or whether the system is separated. However, in the prior art, it is uneconomical to design a dedicated signal line between the distributed power supply and the power system to know whether the circuit breaker of the power system is open or not.

Description

The present invention relates to: for a power system connected to a distributed power source by means of an electric circuit, in order to separate from the appropriate circuit or to use A system separation detection circuit for a decentralized power supply that detects the separation of the above-mentioned systems when the operation is stopped.

A distributed power supply is basically composed of a power generation element and an inverter that converts the power generation output from the power generation element into an AC output. For example, like a distributed power supply installed in each residential facility, in this case, for example, a solar cell can be used as a power generation element.

FIG. 15 shows a conventional system separation detection circuit for a distributed power supply.

In FIG. 15 , the decentralized power supply 140 is composed of a DC power source 1 , a converter 2 , a circuit breaker 4 and a receiver 3 . The DC power source 1 as a power generating element is connected to the DC input end of the converter 2 . The load 5 is connected to the AC output terminal of the converter 2 through a circuit breaker 4 and a circuit 9 . The circuit breaker 4 on the side of the decentralized power supply 140 is connected to the circuit breaker 7 on the side of the power system 6 through a circuit 9 , and a signal notifying the circuit breaker 7 of opening is input to the receiver 3 through the dedicated signal line 8 .

In this configuration, system separation occurs ie the circuit breaker 7 on the side of the power system 6 is opened. Then, on the circuit breaker 7 side, a voltage is supplied from the distributed power supply 140 through the circuit 9, and a so-called reverse voltage state occurs, which poses a risk in the control of the circuit breaker 7 and becomes a power system security problem. For this reason, the signal that informs the circuit breaker 7 to disconnect is introduced into the receiver 3 through the dedicated signal line 8, and the circuit breaker 4 is disconnected by the receiver 3 to disassemble the distributed configuration type power supply 140, that is, to separate from the circuit 9, or This means that the operation of the converter 2 is stopped.

In this existing system separation detection circuit, it is necessary to receive a signal notifying the system separation from the system separation place that the system separation can be detected. Usually, there is a long distance between the distributed configuration type power supply 140 and the power system 6, Therefore, the dedicated signal line 8 for conducting the above-mentioned system separation signal is very long, and since equipment for this arrangement is necessary, there is a problem that the existing system separation detection circuit is very expensive.

Therefore, it is an object of the present invention to solve the above-mentioned problems and to provide a system separation detection circuit for a decentralized power supply which is not only very economical but also can detect system separation very accurately.

In order to solve the above-mentioned problems, the first aspect of the present invention includes: a power generating element; and for a distributed power supply having a converter for converting the power generation output from the power generating element into an AC output, predetermined information is superimposed on the AC output of the converter. The superposition device; the detection device for detecting system separation on the side of the output end of the above-mentioned converter based on the superimposed signal of the above-mentioned predetermined information from the AC output side of the above-mentioned converter.

Accordingly, in a distributed power supply connected to the power system through an electric circuit, system separation can be detected without introducing such a dedicated signal line from the outside.

In order to solve the above-mentioned problems, the second solution of the present invention is: due to setting up the first oscillation device with a frequency that is proportional or approximately proportional to the active power command value and making the active power command value equal to the above-mentioned active power command value The active power setting means, which is increased or decreased by a small amount at a constant rate in synchronization with the first oscillating means, increases or decreases the active power supplied from the converter to the power system by a small amount.

Moreover, active power is detected, and a second oscillating device that generates a frequency pulse group that is proportional or approximately proportional to the active power value or an increase or decrease is set up, synchronized with the oscillation cycle of the first oscillating device and corresponding to the increase in active power , A counter for adding and subtracting the number of pulse groups of the second oscillating device, and a detection device for separating the detection system when the counter is added once and the result of the subtraction from the value becomes below a certain value .

Therefore, according to the second solution of the present invention, the voltage phase on the AC output side of the converter (referred to as the phase corresponding to the power system) is slightly changed, and the converter monitors the variation of the active power supplied to the power system. After the system is separated, the amount of change decreases. When the detection system is separated, the active power setting device, which is used as a device for making the active power change very small, is the same as the amount of small change that increases or decreases according to the power generated by the DC power supply. Output A value that is proportional or approximately proportional to the active power command value.

On the other hand, as the monitoring means for the amount of change, the difference between active power when active power increases and active power decreases according to the second oscillator and the counter is calculated to grasp the amount of change in active power. At this time, regardless of the magnitude of the slight change in active power, the calculated values of each active power amount are substantially constant when increasing and decreasing, and the accumulation time can be changed to enable the first oscillation device to function. As a result, the determination amount of the active power value becomes substantially constant. As the accuracy of system separation determination is thus improved, since the variation range of the power consumption of the DC power supply becomes constant, the stabilization of the DC power supply becomes easier.

Furthermore, the above-mentioned detection device has: according to the system separation detection A circuit breaker control device for disconnecting the circuit breaker on the side of the AC output terminal in the distributed configuration power supply by a signal; The circuit breaker on the AC output side is closed, and a closing control device that detects the voltage on the circuit between the circuit breaker on the AC output side and the power system in the decentralized configuration power supply and closes the circuit breaker on the AC output side. Thereby, since the restoration of power supply can be detected on the power system side after system separation, reconnection with the power system can be quickly performed after restoration of power supply.

Moreover, in order to solve the above-mentioned problems, in the third aspect of the present invention, the phase of the voltage on the side of the AC output terminal of the converter of the distributed power supply is changed very little by means of the oscillation device, whereby the converter makes the power supply The active power of the system changes. At this time, when the power system with much larger power generation capacity than the distributed configuration power supply is connected with the distributed configuration power supply through the circuit, although the converter makes the power supplied to the circuit connected to it changes, while the frequency on the circuit remains roughly constant. On the one hand, as the disconnection of the so-called power system, when an external power source such as a distributed power source and a generator, which has a power capacity not much larger than that of the distributed power source, is connected to the distributed power source, with the distributed The configurable power supply supplies changes in the amount of active power supplied to other connected power sources, and detects system separation from the power system based on changes in the frequency of the connected points.

Therefore, in the third aspect of the present invention, an active power setting device that synchronizes the amount of active power supplied by the converter to the power system with the oscillation device and has a small increase or decrease is set. frequency component extracting means for extracting an oscillation frequency component of the oscillating means from the voltage, and detecting means for detecting system separation based on an output value from the frequency component extracting means.

Therefore, according to the third solution of the present invention, the voltage phase of the AC output side of the converter (referred to as the phase difference with respect to the power system or other power supply voltage) is changed very little, so that the converter supplies power to the power system or other power sources. Active power changes, although when the distributed power supply is connected to the power system, the voltage frequency of the system contact point is roughly the same as the natural frequency of the power system. When other power sources with a much larger power capacity are connected to the distributed power supply, the voltage frequency at the contact point changes as the active power supply from the decentralized power supply changes. Therefore, the active power supply amount of the distributed power supply is periodically changed due to the oscillating device oscillating at a specific frequency. Furthermore, the frequency component having the oscillation frequency of the oscillation means and the same frequency filter characteristic is extracted from the voltage signal at the AC output side of the converter by the frequency acquisition means of the oscillation means. Here, when the distributed configuration power supply is connected with the power system, although the frequency component signal of the oscillation device is not included in the output signal from the frequency component extraction device, on the one hand, because when it is not connected with the power system, The frequency component signal of the oscillating device is included, so by detecting the frequency component signal of the oscillating device from the frequency component extraction device by the detection circuit: when the detection value is above a predetermined value, the power system becomes disconnected, that is, system separation is detected.

As a result, it is possible to detect system separation in the decentralized configuration power supply body, and since the active power change cycle can be extracted at any value, by setting the active power different from the natural frequency change cycle of the general power system and other frequency change cycles Change cycle, high-precision system separation detection becomes possible.

Furthermore, the detection device may also have: a disconnection control device for disconnecting the circuit breaker on the side of the AC output end in the decentralized configuration power supply according to the system separation signal; and, disconnecting the circuit breaker on the side of the AC output terminal Finally, the power system side resumes power supply, that is, the circuit breaker on the power system side is closed, and the voltage on the circuit between the circuit breaker on the AC output side of the decentralized power supply and the power system is detected and the above AC output Closing control device that closes the circuit breaker on the terminal side. As a result, since power supply recovery can be detected on the side of the power system after system separation, reconnection with the power system can be quickly performed after power supply recovery.

In order to solve the above-mentioned problem, in the 4th scheme of the present invention, with respect to the composition of the above-mentioned 3rd scheme, since the above-mentioned converter output change frequency is not fixed and changes with an arbitrary certain characteristic curve, the frequency component taken out by the frequency component extracting device is the same as that of the above-mentioned one. Adjustment and change, the change characteristic curve is completely carried out, and the detection signal from the detection device is output only when the change frequency component is detected. In short, in the fourth plan, in the active power setting device and the frequency component extraction device of the third plan, the oscillator whose output is increased becomes the first oscillator, and the generation of external disturbance is increased in the first oscillator. The output of the second oscillating device is used, thereby changing the oscillation frequency of the first oscillating device within a certain range during the oscillation period of the second oscillating device. Further, the frequency component extraction means adjusts the oscillation frequency of the first oscillation means to change the output frequency.

Thus, the active power supply of the distributed configuration power supply is periodically changed by the first oscillating device whose oscillating frequency changes with a certain characteristic curve. The oscillation frequency component of the voltage signal on the output side of the first oscillating means, here, is given by When the distributed configuration power supply is connected with the power system through a circuit, the voltage frequency at the AC output side of the distributed configuration power supply is roughly consistent with the natural frequency of the power system, and the output of the frequency component extraction device will not detect the first A signal of varying frequency content of an oscillating device. On the one hand, when the system is separated, the change characteristic curve of the above-mentioned change frequency is all continued to the bottom and the change frequency component of the AC output of the converter is taken out by the frequency component extraction device, only in this case it is determined that the system is separated and output by the detection device heartbeat.

For this reason, even though the power system usually contains inherent low-order frequency components, in the fourth aspect of the present invention, since multiple changing frequency components within the range of not only detecting a single changing frequency component are detected, the power system does not In the case of contact, it is possible to prevent false detection as system separation is completed.

Furthermore, the above detection device may also have: a circuit breaker for disconnecting the circuit breaker on the side of the AC output end in the distributed configuration power supply according to the system separation signal; and, after the circuit breaker on the side of the AC output end is disconnected , the power system side resumes power supply, that is, the circuit breaker on the power system side is closed, and the voltage on the circuit between the circuit breaker on the AC output side of the above-mentioned decentralized configuration power supply and the power system is detected and the above-mentioned AC output Closing control device that closes the circuit breaker on the terminal side. Thus, since the restoration of power supply on the side of the power system after system separation can be detected, reconnection with the power system can be quickly completed after restoration of power supply.

Furthermore, in the fifth aspect of the present invention, since the power transmission line constituting a part of the power system becomes a distributed parameter line as shown in FIG. Impedance Z has maximum and minimum values for multiple frequencies (in addition, from Figure 10, 900 is the transmission line, 5 is the load circuit, 901-904 is the line impedance, 905-907 is the line electrostatic capacitance, 501 is the resistance , 502 is a reactor, 503 is a capacitor).

However, in the fifth aspect of the present invention, as the AC output power waveform of the distributed power supply, the sinusoidal voltage with the same frequency as that of the power system is used, and the converter has the function of obtaining a waveform that can superimpose the voltage waveform according to the command, A voltage waveform command signal to superimpose a sinusoidal voltage having the same frequency as that of the power system is supplied to the inverter by the first oscillation device. Here, the oscillation frequency of the first oscillating device is changed, and for the frequency at which the transmission line impedance _ZS has a minimum value, the output current of this frequency from the distributed power supply flows into the power system side at the most, and on the other hand, for The frequency at which the impedance Z _S has a maximum value makes the output current of the frequency from the distributed power supply flow into the side of the power system at the least. Moreover, since there are relatively many maxima and minima frequencies that generate the current value, a resonant circuit and the like are connected to the load circuit of the distributed power supply as shown in Figure 10, although the resonant frequency is the frequency at which a large current flows. exist, the number of which is much less than the number of the maximum value of the transmission line current.

In the fifth aspect of the present invention, as the oscillation frequency range of the first oscillating device, a range f _T that includes a large frequency of generating the current maximum value is selected, and the oscillation period of the second oscillating device is within the above-mentioned frequency range f _T The oscillation frequency of the first oscillation device is changed periodically. As a result, since a plurality of oscillation frequency component currents of the first oscillating device having a large current value appear periodically in the AC output current of the distributed configuration power supply, the frequency component extracting device is extracted from the AC output current of the distributed configuration power supply. The oscillation frequency component of the first oscillator. The counter counts the number of extracted values equal to or greater than a predetermined value, that is, the number of current maximum values, from the values of the extracted frequency components within one cycle of oscillation of the second oscillator.

In the case where the above-mentioned decentralized power supply is connected to an electric power system including transmission lines, the count value of the counter is large. On the one hand, in the state of system separation, since the transmission line is generally cut off at the power consumption side close to the long-distance transmission line, in this state, since the transmission line connected to the distributed power supply is very short, the power transmission line The frequency range in which line impedance exhibits maximum and minimum shifts to the high-frequency side, and as a result, the number of currents exhibiting maximum and minimum decreases rapidly in the above-mentioned frequency range f _T . Furthermore, the count value of the counter is input by the detection means, and when the count value of the counter decreases, it is possible to easily detect the separation of the system.

As a result, it becomes possible to detect the separation of the system in the distributed configuration power supply body. Although the distributed configuration power supply is connected to the transmission line, other distributed configuration power supplies, generators and loads are connected, by directly detecting the inherent high-order harmonics of the transmission line The presence or absence of the system makes it possible to detect the system separation with high precision.

Moreover, the above-mentioned detection device may have: a disconnection control device for disconnecting the circuit breaker on the AC output side of the decentralized power supply according to the system separation detection signal; and, after the circuit breaker on the AC output side is disconnected, The power supply on the side of the power system is restored, that is, the circuit breaker on the side of the power system is closed, and the voltage on the circuit between the circuit breaker on the side of the AC output side in the decentralized configuration power supply and the power system is detected and the circuit breaker on the side of the above-mentioned AC output side is closed. The circuit breaker is closed closed-circuit control device, thus, since the restoration of power supply of the power system after the system is separated can be detected, the reconnection with the power system can be quickly realized after the power supply is restored.

Fig. 1 is according to the first embodiment of the present invention, the configuration diagram of the decentralized arrangement type power supply of application system separation detection circuit,

2 is a component diagram of a system separation detection circuit according to the first embodiment,

FIG. 3A is a diagram showing signal waveforms of the first embodiment,

Fig. 3B is a diagram showing other signal waveforms of the first embodiment,

Fig. 4 is a configuration diagram of a distributed configuration power supply applying a system separation detection circuit according to the second embodiment of the present invention,

5 is a component diagram of a system separation detection circuit according to a second embodiment,

Fig. 6A is a diagram showing signal waveforms of the second embodiment,

Fig. 6B is a diagram representing other signal waveforms of the second embodiment;

7 is a component diagram of a system separation detection circuit according to a third embodiment of the present invention;

Fig. 8 is a configuration diagram of a distributed configuration power supply applying a system separation detection circuit according to the fourth embodiment of the present invention,

9 is a component diagram of a system separation detection circuit according to a fourth embodiment,

Fig. 10 is a diagram showing an example of a power system and a load circuit,

Fig. 11 is a diagram showing signal waveforms of the fourth embodiment,

Fig. 12 is a diagram showing other signal waveforms of the fourth embodiment,

13 is a configuration diagram of a system separation detection circuit according to a fifth embodiment of the present invention,

Fig. 14 is a diagram showing the time characteristic of each signal in the fifth embodiment,

FIG. 15 is a configuration diagram of a conventional system separation detection circuit.

The best form for carrying out the invention.

Hereinafter, the present invention will be described with reference to the accompanying drawings.

Fig. 1 is a diagram showing the configuration of a distributed power supply applying a system separation detection circuit related to the first embodiment of the present invention. As shown in FIG. 1 , the DC power supply 1 is connected to the DC input end of the converter 2 through the power detector 13 , and the AC output end of the converter 2 is connected to one end of the circuit 9 through the active power detector 12 and the circuit breaker 4 . Also, a suitable load is connected to circuit 9 . 100 is a distributed power supply, which has a DC power supply 1 , a converter 2 , an active power detector 12 , a power detector 13 , a system separation detection circuit 40 and a circuit breaker 4 .

For this structure, the system separation detection circuit 40 provides an instruction to slightly change the output power of the converter 2 to the converter 2, and detects the small change amount based on the signal from the active power detector 12, and according to the detection result, the power system 6 The circuit breaker 7 on one side is disconnected, that is, the separation of the detection system is detected, and the circuit breaker is disconnected or the operation of the converter 2 is stopped when the system separation is detected.

Fig. 2 is a block diagram of a system separation circuit related to the first embodiment of the present invention.

For Fig. 2, 42 is an average active power calculation unit, according to the predetermined average active power reference value and the detection signal value from the power detector 13, for obtaining the active power command value P of the average active power meeting the reference value ^* is calculated, and the value P ^* is input to the active power setter 41 and the first oscillator 43 . The first oscillator 43 oscillates a frequency square wave signal that is proportional or approximately proportional to the active power command value P ^* , and the output signal is input to the control input terminal of the active power setting device 41 and the up-down count of the bidirectional counter 45 command input.

The active power setter 41 is synchronous with the oscillation period of the first oscillator 43 and alternately outputs an active power command value signal for performing addition and subtraction calculations on the active power command value P ^* with a small change ΔP of P ^* and a certain ratio, That is, a signal consisting of P ^* +ΔP and a signal consisting of P ^* -ΔP are alternately output. An example of the output signal waveform is indicated by "a" in FIGS. 3A and 3B. In the figure, T represents the oscillation period of the first oscillator 43 .

The converter 2 has an adder 203 , a regulator 201 composed of, for example, a PI regulator, and a converter 202 for converting direct current to alternating current. The output signal (P ^* +△P/P ^* -△P) from the active power setting device 41 is input to the "+" input terminal of the adder 203, and the detection output signal (P-△P/ P-△P) input “-”, the output signal from the output terminal is input to the regulator 201 . The output signal from the regulator 201 is input to the converter 202 , thereby constituting the control loop 11 for active power regulation of the converter 2 .

Moreover, the main circuit in the converter 2 is shown by the dashed line from the DC power supply 1 to the circuit breaker 4 .

On the one hand, the detection output signal from the active power detector 12 is input to the second oscillator 44, and the oscillator 44 is proportional to the value of P+ΔP or P-ΔP or is proportional to the value of +ΔP or -ΔP every T/2. The value of △P oscillates at a proportional frequency, and the resulting pulse group signal is output. This pulse group signal is input to the count input terminal of the bidirectional counter 45 . The two-way counter 45 is synchronized with the increase and decrease command every T/2 from the first oscillator 45, and the command value from the active power setter 41 counts up when P ^* +△P, and when P ^* P ^* -△P Count down at P, switch every T, when the system is connected, that is, when the circuit breaker 4 in the decentralized configuration power supply and the circuit breaker 7 on the side of the power system 6 are closed, in Figure 3A (when P±△P is large ) and in Fig. 3B (P ± △ P hours) denoted by "b" (but the simulated waveform is shown for convenience in the figure). This figure clearly shows that the value (△X) of the up-and-down count result (immediately before switching) of the bidirectional counter 45 once (every T) is substantially constant regardless of the magnitude of the active power command value P ^* .

However, when the system is disconnected, that is, when the circuit breaker 7 on the side of the power system 6 is disconnected, even if there is active power P±△P signal value provided on the converter 2, the AC output of the converter 2 Since the active power of the two-way counter 45 is substantially constant, the count value (ΔX) increased or decreased in each period T of the bidirectional counter 45 is approximately zero. According to the above situation, according to the signal detected per cycle on the first oscillator 43, that is, it is detected that the up-down counter is 0 or △X before each cycle T is about to be reset, and the judging circuit 46 can judge whether the system is When it is judged that the system is separated, the circuit breaker 4 is disconnected. Therefore, as mentioned above, when the systems are connected, because the value of ΔX is not greatly affected by the active power signal value P and is basically a certain value, the system separation detection device based on the decision loop 46 has high reliability. is obvious.

In the distributed power supply 100 described above, whether or not the system is separated can be reliably detected.

Fig. 4 is a second embodiment of the present invention, which shows a configuration diagram of a decentralized power supply suitable for such a system separation detection circuit. As shown in FIG. 4 , there are: a distributed power supply 110 , a DC power supply 1 , a converter 2 , a circuit breaker 4 , a system separation detection circuit 50 , an active power detector 12 and a power detector 13 . The DC power source 1 is connected to the DC input terminal of the converter 2 through a power detector 13 . The AC output terminal of the converter 2 is connected to one end of the circuit 9 through the active power detector 12 and the circuit breaker 4 . The other end of the circuit 9 is connected to the power system 6 through a circuit breaker 7 . Furthermore, the AC output terminal of the converter 2 is connected to the system separation detection circuit 50 through the system voltage (voltage waveform) signal line 10 .

According to this configuration, the system separation detection circuit 50 provides an instruction to the converter 2 that the AC power output by the converter 2 changes little in its period, so when the AC power at the AC output terminal side of the converter 2 is detected, When the cycle of the voltage fluctuates, the system disconnection is detected based on the detection result, and when the system disconnection is detected, the circuit breaker 4 is opened or the inverter 2 is stopped.

FIG. 5 is a block diagram having the system separation detection circuit 50 according to the second embodiment of the present invention.

As shown in FIG. 5 , the active power command value P ^* from the average active power calculator 42 is input to the active power setter 41 . The output signal of the oscillator 47 is input to the control input of the active power giver 41 . The active power given device 41 is synchronized with the oscillation period of the oscillator 47, and the active power command value signal calculated by adding and subtracting from P ^* with respect to its active power command value P ^{* according to a certain ratio of change △ P * is} also That is, P ^* +ΔP ^* as a signal and P ^* -ΔP ^* as a signal are alternately output every 1/2fD. In Fig. 6A (when the systems are connected) and Fig. 6B (when the systems are not connected, or when the systems are separated), waveforms a1 and a2 show the waveforms of their output signals.

The active power command value (P ^* +△P ^* , P ^* -△P ^* ) from the active power given device 41, and the detection value of the active power detector 12 (P+△P, P ^* -△P ^* ) The subtracted value is input to the regulator 201 through the adder 203 . The output signal of the regulator 201 is input to the converter 202 , so that the control link 11 of the converter 2 for the purpose of active power regulation is constituted.

On the one hand, for example, when a band-pass filter is used as the frequency detector 48, a signal for maintaining the voltage waveform on the AC output terminal side of the converter 2 is input to the frequency detector via the signal line 10, and based on the input signal , the same frequency component as the oscillation frequency of the oscillator 47 in the frequency detector is extracted and output. This output signal is input into a decision circuit 49 . The judging circuit 49 judges whether the system is separated according to whether the detected voltage value as its input signal is higher than a certain level value. When it is judged that the system is separated, the circuit breaker 4 is then disconnected.

When both the circuit breaker 4 on the side of the distributed power supply and the circuit breaker 7 on the side of the power system 6 are closed, when the active power output of the distributed power supply 110 is only ±ΔP relative to its average value P When changing, the phase change shown in "b1" of Fig. 6A is obtained. That is to say, due to the internal resistance included in the converter 2 , there is a phase difference between the internal voltage of the converter 2 and the voltage on the circuit 9 connected to the AC output terminal of the converter 2 . Therefore, when the system is connected, the active power output by the converter 2 changes only with ±ΔP as mentioned above, and its phase difference θ also changes only ±Δθ, but because the power system 6 side at this time The frequency of is substantially constant, and the frequency fo on the side of the distributed power supply 110, as shown by "C1" in FIG. 6A, is almost constant.

On the one hand, if the side circuit breaker 7 of the power system 6 connected to the distributed configuration power supply 110 is disconnected, when the power supply 110 is connected to other distributed configuration power sources 200 through the circuit 9 (the power system is not connected ), same as above, When the active power output of the converter is only changed by ±△P relative to its average value P, as shown in "b2" of Fig. 6B, the phase difference θ of the distributed configuration power supply 110 also only changes by ±△ theta. At this time, in other distributed configuration power sources 200 connected to the same circuit 9, the above-mentioned active power variation components ΔP are shunted and flowed in. In order to offset their variation components ΔP , when the phase difference ±θ is made to decrease, the frequency of the AC output voltage will change. As a result, the output voltage frequency fo of the AC output terminal side (on the circuit 9) of the converter 2, as shown by "C2" in Fig. 6B, is generated synchronously with the variation of the active power variation component (±ΔP). great change.

When the variable frequency component of the above-mentioned frequency fo of the frequency detector 48 is extracted, if the extracted output value exceeds a certain level, then the judging circuit 49 judges that the system is separated.

Fig. 7 shows a block diagram of the system separation detection circuit provided by the third embodiment of the present invention. The system separation detection circuit in this figure is suitable for the distributed configuration power supply shown in Figure 4. In the system separation detection circuit in the figure, an oscillation output signal from the first oscillator 52 is input to the input terminal of the active power setter 41 . on the input of the oscillator 52 . An oscillation output signal from the second oscillator 51 is input. Here, the second oscillator 51 is an oscillator that generates an external interference-type sawtooth wave signal. For example, the oscillation frequency response of the first oscillator 52 composed of a voltage-controlled oscillator is output from the second oscillator 51. The sawtooth wave voltage changes, so that the frequency of the first oscillator 52 changes within the determined range. Then, the frequency detector 53 is synchronized with the oscillation frequency of the first oscillator 52 and serves as a bandpass filter capable of changing the center frequency of the passband.

In this embodiment, its function is the same as that of the second embodiment shown in Figures 4 and 5. When the output signal of the frequency detector 53 exceeds a certain specified value, the determination circuit 54 determines that the system is separated, that is, the circuit breaker 4 disconnect.

However, the oscillation frequency of the first oscillator 52 changes within the range determined by the sawtooth waveform of the second oscillator 51, so that through the entire frequency change, the frequency component due to the change of the AC output voltage of the converter 2 Synchronization with the oscillation frequency of the first oscillator 52 and the use of the frequency detector 104 whose center frequency of the passband can be varied can be extracted.

For this reason, since the control system of the equipment is connected to the power system, and as the above-mentioned circuit 9, there is often a component with a low natural frequency, according to the third embodiment of the present invention, to extract the frequency fluctuating within the determined frequency range Composition is the purpose, so that regardless of whether it is in connection with the power system 6 or not, it is possible to eliminate inappropriate practices such as mistakenly thinking that the system is separated due to external interference.

Fig. 8 is the fourth embodiment of the present invention, which provides a structural diagram of a decentralized power supply using a system separation detection circuit. In FIG. 8 , a distributed power supply 120 is composed of a DC power supply 1 , a converter 2A, a circuit breaker 4 , a system separation detection circuit 70 , and a current detector 14 . The DC power source 1 is connected to the DC input of the converter 2A, the AC output of the converter 2 is connected to one end of the circuit 9 through the current detector 14 and the circuit breaker 4 . The other end of the circuit 9 is connected to the circuit breaker 7 on the power system 6 side. A feeder 900 is connected between the circuit breaker 7 and the power system 6 . Other distributed power sources 200 and loads 5 are connected to the circuit 9 .

Fig. 9 shows a block diagram of a system separation detector proposed in the fourth embodiment of the present invention. 2A shown in Fig. 9 is a converter that adopts a PWM modulation method based on a sine wave triangular wave, and outputs the output signal of the sine wave signal circuit 207 of the AC output voltage waveform command of the converter 2A and is in the converter 2A The output signal of the first oscillator 56 as the waveform to be superimposed on the AC output voltage is added by the adder 208 . The output signal of the adder 208 and the triangular signal from the modulation signal loop 205 are input into the pulse distribution loop 206. On this loop 206, the pulse amplitude modulation signal is modulated to convert DC to AC in the converter 204. The driving signals of the respective switching units are converted and supplied to the converter 204 in this way. Therefore, the AC output voltage waveform of the converter 204 becomes a voltage waveform in which a similar waveform to the output voltage waveform from the first oscillator 56 is superimposed on the sinusoidal voltage waveform that is the frequency of the original power system. The AC output voltage of 204 is added to load 5 and feeder 900 on circuit 9 . The AC output current of the converter 2A is detected by the current detector 14, and the output signal of the current detector 14 is input into the frequency detector 57, and the frequency detector 57 is a band-pass detector whose center frequency of the pass band can be changed. filter made.

However, when the sawtooth-shaped output signal from the second oscillator 55 is input to the frequency detector 57 and the first oscillator 56, the difference between the oscillation frequency of the first oscillator 56 and the passband of the frequency detector 57 The center frequency is given the same frequency value. In other words, in response to the output voltage value of the second oscillator 55, the frequency of the first oscillator 56 is regulated. because Therefore, according to the output voltage of the second oscillator 55, it is possible to make the center frequency of the passband of the frequency detector 57 coincide with the oscillation frequency of the first oscillator 56. Furthermore, it is also possible to directly change the center frequency value of the passband of the frequency detector 57 according to the output signal of the first oscillator 56 . For this reason, the same frequency signal as the oscillation frequency of the first oscillator 56 can be obtained at the output terminal of the frequency detector 57 .

As shown in FIG. 11 and FIG. 12, since the oscillation frequency fc of the first oscillator 56 varies with the oscillation frequency of the second oscillator 55 within the frequency range from _fT1 to _fT2 , the frequency detector 57 The output current Is correspondingly changes with the oscillation frequency fc and increases or decreases. Then when the output signal of the frequency detector 57 is input on the count input end of the counter 58, on the reset input end of the counter 58, the output signal of the second oscillator 55 is input, and the counter 58 only oscillates to the second In one oscillation of the oscillator 55 (that is, one change of the oscillation frequency fc of the first oscillator 56 from f _T1 to f _T2 ), the output current value Is of the frequency detector 57 exceeds the specified value Is ^* . count. Usually, due to the output current value Is of the frequency detector 57, when the feeder 900 is connected to the AC output terminal of the converter 2A as shown in FIG. As shown in FIG. 12 , whether the feeder 900 is connected or not makes a difference in the count value of the counter 58 . When the count output of the counter 58 is input into the judgment circuit 59, according to the difference of the count value, the judgment circuit 59 outputs a detection signal of whether the system is separated or not.

However, f _L shows the oscillation frequency of the loop formed by the inductive reactance 502 and capacitive reactance 503 in the load 5, and f _d1 , f _d2 , and f _d2 show the parallel resonance of the feeder line (equivalent parallel resonant network) respectively. impedance.

Then, Figure 13 shows a fifth embodiment of the present invention. If the above-mentioned embodiments are adopted, when the system separation is definitely detected, the circuit breaker on the side of the distributed power supply is turned off so that It can effectively prevent the circuit existing between the decentralized configuration power supply and the power system from being reversely charged.

In the fifth embodiment of the present invention, the voltage on the power system side is detected on the output side of the distributed power supply at the beginning. input, and the system separation detection circuit has the function of reconnecting the distributed configuration power supply to the power system.

That is to say, in FIG. 13 , 40 is exactly the system separation detection circuit in the aforementioned 2nd figure, the judgment circuit 46 in the system separation detection circuit 40 , and its output signal is input on the reclosing action part 300 . In the reclosing action part 300, the circuit 9 connecting the circuit breaker 4b inside the decentralized power supply 130 to the circuit breaker 7 on the side of the power system 6 extracts the voltage on the side of the power system 6, and separates the voltage from the system according to the extracted voltage. The output voltage obtained by the determination circuit 46 in the detection circuit 40 passes through the circuit breaker coil 4a to make the circuit breaker 4b close. 61 is a reset circuit, which resets the determination circuit 46 after the breaker 4b is turned off.

The structure of the reclosing operation part 300 is described in detail below. The structure of the reclosing operation part 300 is as follows: a voltage detection circuit 301 including a voltage detection circuit 301 for detecting the voltage of the power system 6 side, a NOT gate circuit 302 connected to the output side of the circuit 301, Delay circuit 306 and NOT gate circuit 303, the NOT gate circuit 304 connected on the output terminal of decision circuit 46, the AND gate circuit 307 that the output signal of NOT gate circuit 303 is added with the output signal of NOT gate circuit 304, and the The delay circuit 305 is connected to the output terminal of the circuit 307, and the output signal of the delay circuit is then applied to the above-mentioned circuit breaker diagram 4a.

Hereinafter, the mechanism of action thereof will be described with reference to the time chart of FIG. 14 .

First, at time t _o in Figure 14, due to the action of the circuit breaker 7, the connection between the power system and the distributed power supply is blocked (system separation); at time t _d , due to the function of the system separation detection circuit 40, the AND gate circuit 307 or the output of the delay circuit 305 is zero, and the circuit breaker 4b is turned off when it passes through the circuit breaker coil 4a. At this time, the output of the voltage detection circuit 301 is still "1" after the time t _d until the time t _v . Furthermore, the decision circuit 46 in the system separation detector 40 is reset after the reset time determined by the reset circuit 61 (before the time t _v arrives), so that its output becomes zero.

Thereafter, at time t _r , once the circuit breaker 7 is closed again and the power supply of the circuit 9 is restored, the output of the voltage detection circuit 301 or the output of the NOT gate circuit 303 becomes "1", and the system separation detection circuit 40 ( If the output of the decision circuit 46) is zero, the output of the NOT circuit 304 remains "1" and the output of the AND circuit 307 also remains "1". Therefore, when the time _tc after the action time limit _T45 of the delay circuit 305 has passed, the output of the delay circuit 305 is also "1", and the circuit breaker 4b is closed by the circuit breaker coil 4a. That is, the distributed power supply 130 is automatically reconnected to the power system.

It should be mentioned that due to the action time limit T ₄₅ of the delay circuit 305, if the noise shown at No in Fig. 14 interferes with the reclosing action part 300, the phenomenon that the circuit breaker 4b will not be switched on by mistake. Furthermore, since the operating time limit T ₄₆ of the delay circuit 306 is adopted, the phenomenon that the circuit breaker 4b is mistakenly opened due to the interference of noise shown at No does not exist. Here, the relationship of T ₄₅ >T ₄₆ exists between the operation time limits T ₄₅ and T ₄₆ .

If the above-mentioned fifth embodiment is adopted, when the power system resumes power supply, the re-throwing of the circuit breaker 4b, and the re-connection of the distributed configuration power supply 130 and the power system 6 can be properly handled automatically, and can be released. The trouble of having to put in the circuit breaker 4b manually. In addition, the structure of the reclosing action part 300 as shown in the figure does not have any limiting effect on it.

A note on practicality.

The present invention is applicable, for example, to distributed residential facilities or distributed power sources using solar cells as power generation elements. Such decentralized power sources are connected to the power system including power stations, substations, transmission lines, and the like.

Claims (8)

1. A system separation detection circuit for a distributed configuration power supply. The power supply has a power generation element and a converter for converting the output generated by the above power generation element into an AC output. Its characteristics are: superposition means having a first oscillator which oscillates at a frequency which is proportional or approximately proportional to the output power from the above-mentioned power generating element; The AC output active power command input into the converter is synchronized with the oscillation frequency of the first oscillator and increases or decreases in a certain proportion, and The detection device has a second oscillator for generating a pulse group signal with a frequency proportional or approximately proportional to the value of the AC output active power or the increase or decrease of the active power value; and an oscillation cycle of the first oscillator synchronous, counters that add and subtract the number of pulses from the pulse group signal from the second oscillator, and A device for detecting whether the system is disconnected or not on the AC output side of the converter based on the result of adding or subtracting the counter. 2. The system separation detection circuit for distributed configuration type power supply according to claim 1, characterized in that: said detection device has: according to the detection result of said system separation, the AC output side of said converter The disconnection control device for disconnecting the circuit breaker, and the disconnecting device for closing the circuit breaker when it detects that the power system resumes power supply according to the voltage on the power system side to which the circuit breaker is connected after the circuit breaker is disconnected control device. 3. The system separation detection circuit for decentralized configuration power supply according to claim 2, characterized in that, the detection device has: according to the detection result of the system separation; The off control device for disconnecting the circuit breaker, and the on control device for closing the circuit breaker when it detects that the power system is restored to power according to the voltage on the side of the power system to which the circuit breaker is connected after the circuit breaker is disconnected device. 4. The system separation and detection circuit for decentralized configuration power supply according to claim 1, characterized in that the superposition device includes: A sine wave signal output device that outputs the output voltage waveform command of the converter; first oscillator; a second oscillator for periodically varying the frequency of oscillation of the first oscillator; and means for forming an addition signal for controlling elements in a converter for converting direct current to alternating current, the addition signal being said sine wave signal output means The output voltage waveform instruction and the oscillation output signal of the first oscillator are added to form; And wherein the above-mentioned detection device has: frequency component extraction means for extracting an oscillation frequency component of the first oscillator from the converter output; A counter for counting the number of times the amplitude of the output signal from the frequency component extracting means exceeds a certain value within one oscillation cycle of the second oscillating means, and A detector for detecting whether or not the system is disconnected is on the output side of the inverter based on the count value of the counter. 5. The system separation detection circuit for distributed configuration type power supply according to claim 4, characterized in that, the detection device has: according to the detection result of the system separation, the disconnection of the AC output terminal side of the converter The disconnect control device for disconnecting the circuit breaker, and when the circuit breaker is disconnected, according to the voltage of the power system side connected to the circuit breaker, when it is detected that the power system resumes power supply, the circuit breaker is connected Switch on the control unit. 6. A system separation detection circuit for a decentralized configuration power supply. The power supply has a power generating element and a converter that converts the output generated by the power generating element into an AC output. Its characteristics are: superimposing means having an oscillator oscillating at a fixed frequency; and an active power setting means for making the AC output active power command fed to said converter in response to the power generated by the generating element, and said The oscillation frequency of the first oscillator mentioned above is synchronized and increased or decreased proportionally; and The detecting means has frequency component extracting means for extracting oscillator frequency components of the oscillator from the converter output side, and detecting means for detecting system separation at the converter output side based on the amount of oscillation frequency components generated from the frequency component extracting means. 7. The separation detection circuit for distributed configuration type power supply system according to claim 6, characterized in that the oscillator changes the oscillation frequency in response to the output signal from the power generation device, and the power generation device periodically generates a voltage with a specified voltage change The signal of the mode, and the above-mentioned frequency component extracting means change the extraction frequency along with the output oscillation frequency of the oscillating means. 8. The system separation detection circuit for distributed configuration type power supply according to claim 7, characterized in that, the detection device has: according to the detection result of the system separation, the disconnection of the AC output side of the converter The disconnect control device for disconnecting the circuit breaker, and when the circuit breaker is disconnected, according to the voltage of the power system side to which the circuit breaker is connected, when it is detected that the power system resumes power supply, the circuit breaker is turned on Switch on the control unit.

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