JPH06284560A - System anomaly detection method - Google Patents

Abstract

PURPOSE:To make it possible to accurately detect the occurrence of anomaly such as phase jumping by comparing the number of pulses generated by a reference oscillator within a certain time period of the system voltage with the number of pulses within a certain time period immediately before the former. CONSTITUTION:A zero point of the system voltage is detected by a zero point detector 1, and pulses generated by the reference oscillator 2 up to the zero point after N/2 period are counted by the first counter 4 and the second counter. And the number of counts is compared with the number of counts in N/2 period just before with a computing element 6 and, if the difference exceeds the set point, it is judged to be system anomaly, that is, phase jumping. As stated above, the length of 1/2 time period of the system voltage is compared with the number of pulses, so that reliable detection is possible even though the amount of phase jumping is small. Also, the phase jumping only can be accurately detected because a gentle fluctuation in the system frequency hardly appears from a comparison to 1/2 period just before.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system abnormality detecting method capable of accurately detecting system abnormalities such as phase jump of system voltage and frequency abnormality.

[0002]

2. Description of the Related Art For example, in a system in which a distributed power system such as a solar cell is connected to a low-voltage distribution line or a high-voltage distribution line, when the system is stopped, the distributed power system goes into an independent operation state, There is a possibility that a reverse charging phenomenon may occur in which the voltage remains in the system even though the circuit breaker for distribution has stopped.

For this reason, various methods have been studied for detecting that the system has stopped. One of them is a phase jump detection method which utilizes the fact that the phase of the system voltage jumps when the system is stopped. It has been known. Here, the phase jump means a phenomenon in which the phase of the system voltage shown by the solid line in FIG. 1 shifts by α as shown by the broken line when the system is stopped.

Conventionally, to detect a phase jump, a system frequency is converted into a voltage by an FV converter 11 as shown in FIG. 4, and an output voltage of the FV converter 11 is converted into a reference voltage generator 12.
The method of comparing with the reference voltage of 3 by the comparator 13 was adopted. However, since the phase jump due to the system stop occurs only once, the fluctuation of the output voltage of the FV converter 11 is small, the detection is difficult when the amount of phase jump is small, and the fluctuation of the normal system frequency is also caused. There are drawbacks such as the possibility of malfunction.

[0005]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems and provides a method for detecting a system abnormality that can accurately detect a system abnormality such as a phase jump. It was done for good.

[0006]

Means for Solving the Problems The present invention made to solve the above problems is to count the pulses generated by a reference oscillator between the zero point of a system voltage and the zero point after N / 2 cycles, The feature is that the count number is compared with the count number in the immediately preceding N / 2 cycle and a system abnormality is judged when the difference exceeds a set value. N is a positive integer of about 1-10.

[0007]

According to the present invention, since the number of pulses generated by the reference oscillator during the N / 2 cycle of the system voltage is compared with the number of pulses during the N / 2 cycle immediately before that, the oscillation frequency of the reference oscillator is increased. If set, the steady-state system voltage waveform before the system stop jumps to the system stop voltage waveform after the system stop as shown in FIG. Since the difference is detected, the phase jump can be surely detected. Further, according to the present invention, since the comparison is made with the number of pulses in the immediately preceding N / 2 cycle, in the case of a gradual fluctuation of the normal system frequency, it is not judged as a system abnormality and no malfunction occurs.

[0008]

The present invention will be described in more detail below with reference to the embodiments shown in FIGS. FIG. 2 shows a first embodiment of the present invention, in which the zero point of the system voltage is constantly detected by the zero point detector 1. On the other hand, the reference oscillator 2 generates a pulse having a frequency sufficiently higher than the system frequency (for example, 10 kH), and each time the gate circuit 3 receives a signal from the zero-point detector 1, the pulse transmitted from the reference oscillator 2 is The output destination is alternately switched to the first counter 4 and the second counter 5.

These counters count the number of pulses and output them to the arithmetic unit 6. In this case, 1 / of the system voltage
Since the switching signal that also serves as the reset signal is output from the zero-point detector 1 every two cycles, the first counter 4 and the second counter 5 are always counting the number of pulses between adjacent 1/2 cycles. Become. Then, the arithmetic unit 6 compares the two, and when the difference exceeds the set value, it is determined that the phase jump occurs.

As described above, according to the present invention, since the length of the 1/2 cycle of the system voltage is compared by the number of pulses, reliable detection is possible even when the amount of phase jump is small, and the system frequency fluctuates gently. Since it hardly appears in comparison with the immediately preceding 1/2 cycle, only the phase jump can be detected reliably.

When the output of the counter (the number of pulses of 1/2 cycle) is D and the oscillation frequency of the reference oscillator 2 is f, the system frequency F can be calculated by the formula F = f / 2D. You can also ask for F. Therefore, if the function of determining the system abnormality when the system frequency F thus obtained exceeds the allowable range is added to the arithmetic unit 6, the frequency abnormality can be detected.

In the first embodiment described above, the number of pulses is counted by the first counter 4 and the second counter 5, respectively. However, in the second embodiment shown in FIG. 3, the second counter 5 is used instead. The memory 7 is installed and the output of the first counter 4 is sent to the memory 7. As a result, the number of pulses of the immediately preceding 1/2 cycle is stored in the memory 7, and if the output of the first counter 4 and the output of the memory 7 are compared, the phase jump etc. will occur in the same manner as described above. A system abnormality can be detected. Although the number of pulses of 1/2 cycle is counted in the embodiment, the number of pulses of 1 cycle, 1.5 cycles, 2 cycles, etc. may be counted by setting N to 2 or more. However, if N is increased, the accuracy of phase jump detection decreases, so it is not preferable to set N to 10 or more.

[0013]

As described above, according to the method of detecting a system abnormality of the present invention, when a system abnormality such as a phase jump or a frequency abnormality occurs, it can be detected with high accuracy. In a system in which a distributed power supply system is connected to a distribution line or a high-voltage distribution line, it has a great utility value in reliably detecting that the system has stopped.

[Brief description of drawings]

FIG. 1 is a waveform diagram illustrating phase jump.

FIG. 2 is a block diagram illustrating a first embodiment of the present invention.

FIG. 3 is a block diagram illustrating a second embodiment of the present invention.

FIG. 4 is a block diagram illustrating a conventional phase jump detection method.

[Explanation of symbols]

 1 Zero point detector 2 Reference oscillator 3 Gate circuit 4 1st counter 5 2nd counter 6 Arithmetic unit 7 Memory

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yoshihiko Sakurai 1 of 873 Kazawa, Tobu-cho, Ogata-gun, Nagano Prefecture

Claims (2)

[Claims] 1. The number of pulses generated by the reference oscillator is counted from the zero point of the system voltage to the zero point after N / 2 cycles,
A method for detecting a system abnormality, which compares the count number with the count number in the immediately preceding N / 2 cycle and determines that the system abnormality occurs when the difference exceeds a set value. 2. The system abnormality according to claim 1, further comprising a function for calculating a system frequency from the count number and determining a system abnormality when the calculated frequency exceeds an allowable range. Detection method.