JP2603237Y2 - Reverse charge detection device - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a distributed power supply used by connecting to a system power supply such as a solar power generator.
The present invention relates to a reverse charge detection device for preventing a construction worker from being electrically shocked by being reversely charged from a distributed power supply device to a system power supply side when a system power supply is disconnected due to regular maintenance, an accident, or the like.

[0002]

2. Description of the Related Art Recently, distributed power supplies such as solar power generation and wind power generation have been developed as energy saving and clean energy, and a power supply system connected to a system power supply of a commercial power supply has been developed.

For example, FIG. 3 shows a power supply system of a distributed power supply device using a solar cell as a power supply. The distributed power supply device 1 includes a solar cell 2, an interconnection inverter 3, a control circuit 4 for driving the interconnection inverter 3, and the like. It is configured.

The system power supply 5 transmits the AC power generated by the power plant 6 to each pole transformer 8 at a high voltage of 6.6 kV via the substation 7 and reduces the voltage to 200 V by the pole transformer 8.
The power is distributed to each load 10 in the home via the interconnection switchboard 9. On the other hand, on the home side, the DC power generated by the solar cell 2 is converted into AC power by the interconnection inverter 3 controlled by the control circuit 4 and distributed to each load 10 in the home, and the surplus power is placed on the pole. Power is transmitted to the system power supply 5 via the transformer 8.

[0005] By the way, such a power supply system of the distributed power supply device is designed such that when the power supply of the distributed power supply 1 is connected to the power supply 5 when the power supply of the distributed power supply 5 is cut off due to periodic maintenance or an accident, the power supply of the distributed power supply 1 is disconnected. 5 was reverse-charged by the distributed power supply 1, and the construction worker was electrocuted and dangerous.

For this reason, it is necessary to disconnect the distributed power supply 1 during such a power failure of the system power supply 5 so as not to apply the voltage of the distributed power supply 1 to the system power supply 5. Although not shown, a reverse-charge detection device for detecting reverse charging of the system power supply 5 is provided at the connection portion of.

The pole transformer 8 has a hysteresis excitation characteristic. When a sine wave current of the distributed power supply device 1 flows into the power transformer during a power outage, the pole transformer 8 has a property of generating a third harmonic voltage according to the hysteresis in the line. The reverse charge detection device detects a third harmonic voltage generated in the system power supply 5 at the time of reverse charge, and
When the amplitude of the harmonic voltage is equal to or higher than a predetermined level, it is determined that reverse charging is performed, and the so-called third harmonic voltage method in which the distributed power supply device 1 is opened from the system power supply 5 is employed.

FIG. 2 is a block circuit diagram of the third harmonic voltage type reverse charging detecting device 11 utilizing the hysteresis characteristic of the pole transformer 8. As shown in FIG.

That is, the reverse charging detecting device 11 detects the system voltage signal VF from the line of the system power supply 5 and passes the system voltage signal VF through a band-pass filter 12 tuned to the frequency of the third harmonic. The harmonic voltage signal VF3 is detected. The absolute value of the detected third harmonic voltage signal VF3 is calculated by an absolute value calculation circuit 13 to be converted into an absolute value signal | VF3 | of the third harmonic voltage. Then, the determination circuit 14 compares the amplitude of the absolute value signal | VF3 | with the set value, determines that the set value or more is reverse-charged, and outputs a reverse-charge detection signal a.
By operating a protection device (not shown), the distributed power supply device 1 is opened from the system power supply 5.

[0010]

However, many household rectifier loads, such as televisions and refrigerators, are connected to the line of the system power supply 5, and the line of the system power supply 5 to which the distributed power supply device 1 is connected. The third harmonic voltage of about several percent often exists. The third harmonic voltage fluctuates from time to time due to the driving of the home rectifier load, and the content of the third harmonic voltage varies depending on the line of the system power supply 5. The set value for detection cannot be set uniformly, and it is necessary to make fine adjustments each time the distributed power supply device is installed, and it is difficult to make automatic adjustments.

Therefore, the present invention has been made in view of the above-mentioned problems in the conventional reverse charge detection device, and the reverse charge detection device is capable of automatically adjusting the reverse charge detection level and reliably detecting the reverse charge. It is intended to provide.

[0012]

For this reason, the reverse charging detection device of the present invention is connected to the system power supply when the system power supply fails.
Conversely charge as variance power supply to continue operating
The amplitude value of the third harmonic voltage signal generated in the system power source <br/> detected Ri, in the reverse charging detection apparatus amplitude value has to output a reverse charge detection signal when above a predetermined level, said first A time constant to which the absolute value signals of the three harmonic voltage signals are input and output the short-time average amount of the absolute value signals
A first low-pass filter having a small absolute value signal;
The second row with a large time constant for outputting the long-term average amount of signals
-Pass filters and the output of each low-pass filter
A determination circuit for comparing values , wherein the first low-pass
The output value of the filter is the output of the second low-pass filter
It is characterized in that a reverse charge detection signal is output when the value exceeds a predetermined judgment time or more.

[0013]

The third harmonic component increases in the system power supply due to the reverse charging at the time of the power failure, and the amplitude value of the third harmonic voltage increases and changes.
This increase in the amplitude value quickly changes following the absolute value signal of the third harmonic voltage, and the output changes. The short-time average amount of the low-pass filter set to a small time constant changes slowly.
It is detected by comparing with the long-term average amount of the low-pass filter whose time constant is set to be large. In addition, since the long-term average amount, which is the set value of the reverse charge detection, follows the absolute value signal of the third harmonic voltage, it also corresponds to the constantly changing third harmonic voltage component of the system power supply voltage. The detection level is always adjusted automatically. Also, with respect to an instantaneous increase in the third harmonic voltage component of the system power supply due to a load change or the like, the timer function of the low-pass filter circuit is used to determine a short-term average amount and a long-term average amount in a predetermined manner. It is determined by setting the determination time.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a block circuit diagram of the reverse charge detection device 15 of the present invention. Like the above-described conventional reverse charge detection device 11, at the time of a power failure, the reverse power supply from the distributed power supply 1 is applied to the system power supply 5 side. This is a third harmonic voltage type reverse charge detection device that detects the generated third harmonic voltage.

The reverse charge detection device 15 also detects the third harmonic voltage signal VF3 contained in the system voltage signal VF using the bandpass filter 12 tuned to the third harmonic frequency, and the amplitude of the third harmonic voltage signal VF3 is large. In order to detect the absolute value, the absolute value calculation circuit 13 calculates the absolute value, and the absolute value signal | VF3 | of the third harmonic voltage is calculated.

The absolute value signal | VF3 of the third harmonic voltage
| Outputs the short-term average value and the long-term average value of the third harmonic voltage .
The low-pass filters 16 and 17 are input to the low-pass filters 16 and 17, and the outputs S1 and S2 of the low-pass filters 16 and 17 are input to the determination circuit 18 and compared therewith . Reverse charging is detected as follows.

The low-pass filters 16 and 17 are given by the following transfer functions, respectively. G1 (S) = K1 / (1 + T1 S) Low-pass filter 17; G2 (S) = K2 / (1 + T2 S) where K1 <K2, T1 << T2

That is, the transfer function G of the low-pass filter 17
2 (S) is the transfer function G1 (S) of the low-pass filter 16.
As compared with the above, both the gain K and the time constant T are set to be large, the output is large for the same input signal, and the response is slow.

FIG. 4 is a waveform diagram for explaining the operation of the reverse charging detection device 15. The jagged waveform in FIG. 4 shows the absolute value signal of the third harmonic voltage obtained by performing an absolute value operation on the system voltage signal VF. | VF3 | waveform, and the waveform of the smooth line is the output S of the low-pass filter 17 whose time constant is set to be large.
The waveform of FIG. 2 shows a slightly jagged line, and the waveform of the output S1 of the low-pass filter 16 whose time constant is set to be small is shown. The output S2 is provided with a low-pass filter gain K such that the amplitude of the output S2 is about 1.5 times that of the output S1 in a steady state.

In this waveform diagram, at time t 1, when the power supply of the system power supply 5 is cut off and reversely charged by the distributed power supply device 1, the system power supply 5 has the third harmonic component due to the magnetic characteristics of the pole transformer 8. A voltage is generated, and the absolute value signal | VF3 | of the third harmonic voltage changes to a signal waveform having a high amplitude. Then, the low-pass filter 16 whose time constant is set small is set.
Output S1 rapidly rises in accordance with the time constant in the output waveform of the short-time average amount of the third harmonic voltage. On the other hand, the output S2 of the low-pass filter 17 whose time constant is set to a large value slowly rises in accordance with the time constant in the output waveform of the long-term average amount of the third harmonic voltage.

Then, the judgment circuit 18 takes in the output S2 of the low-pass filter 17 whose time constant is set to a large value as a set value for reverse charging detection, and outputs the output S1 value of the low-pass filter 16 whose time constant is set to a small value. Set value output S
When the time ta when the value of the output S1 exceeds the value of the output S2 exceeds the set determination time ts or more, it is determined that reverse charging is present, and a reverse charging detection signal a is output.

At time t2, if the load of the system power supply 5 fluctuates due to the driving of the household load 10 or the like, the system power supply 5 generates a voltage of the third harmonic component when the load fluctuates,
As the absolute value signal | VF3 | of the harmonic voltage, a signal waveform having a high amplitude appears instantaneously. Also in this case, the output S1 of the low-pass filter 16 whose time constant is set small and the output S2 of the low-pass filter 17 whose time constant is set large are
As in the case of the reverse charging of the system power supply 5, the output waveform of the short-time average amount and the output waveform of the long-time average amount of the third harmonic voltage rise in accordance with the time constants, and the output S1 thereof increases.
, S2 are similarly compared and determined by the determination circuit 18.

In this case, the appearance time of the third harmonic voltage of the system power supply 5 due to the load fluctuation is instantaneous compared to the appearance time of the third harmonic voltage due to the reverse charging, and the output S
The time tb in which the value 1 exceeds the output S2 value is extremely short, and the determination circuit 18 determines that the value is within the set determination time ts.
Ignores this and does not output the reverse charge detection signal a.

[0025]

As described in detail above, the reverse charge detection device of the present invention inputs the absolute value signal of the third harmonic voltage of the system power supply to two low-pass filters whose time constants are set small and large. Since the output values of both filters are compared to detect a change in the third harmonic voltage contained in the system power supply, a change in the third harmonic voltage such as a load fluctuation that appears instantaneously. Is reliably removed and no malfunction occurs. Also, the output S2 value of the low-pass filter 17 whose time constant, which is the set value for detecting reverse charging, is set to be large, changes following the third harmonic voltage value that fluctuates every moment. The value is automatically adjusted, and there is no need to fine-tune the set value every time the distributed power supply is installed.

[Brief description of the drawings]

FIG. 1 is a block circuit diagram of the reverse charging detection device of the present invention.

FIG. 2 is a block circuit diagram of a conventional reverse charge detection device.

FIG. 3 is a block circuit diagram of a power supply system of the distributed power supply device.

FIG. 4 is a waveform chart for explaining the operation of the reverse charge detection device of FIG. 1;

[Explanation of symbols]

 1 Distributed power supply 5 System power supply 8 Pole-mounted transformer 10 Load 15 Reverse charge detection device 16 Low-pass filter with small time constant set 17 Low-pass filter with large time constant set 18 Judgment circuit VF System voltage signal VF3 Third harmonic Voltage signal | VF3 | Absolute value signal of third harmonic voltage ts Judgment time

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H02J 3/00-5/00 G01R 19/165 H02H 3/50-3/52

Claims (1)

(57) [Scope of request for utility model registration] When a power failure occurs in a system power supply, the system is connected to the system power supply.
The amplitude value of the third harmonic voltage signal generated in the system power supply due to reverse charging such that the distributed power supply apparatus continues to operate is detected, and when the amplitude value is equal to or higher than a predetermined level. In a reverse charge detection device configured to output a reverse charge detection signal, a time constant to which an absolute value signal of the third harmonic voltage signal is input and outputs a short-time average amount of the absolute value signal
A first low-pass filter having a small absolute value signal;
A second time constant with a large time constant for outputting the long-term average amount of signals
-Pass filters and the output of each low-pass filter
A decision circuit for comparing values , wherein the first low-pass
The output value of the filter is the output of the second low-pass filter
A reverse charge detection device, wherein a reverse charge detection signal is output when the value exceeds a predetermined determination time or more.