JPS5837798B2 - Abnormality detection device for synchronous motors - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an abnormality detection device for a synchronous motor, and more particularly to an abnormality detection device for a synchronous motor that is started and stopped via a frequency conversion device.

The present invention is particularly effective when applied to a pumped storage power generator equipped with a silice converter.
In the following explanation, this will be taken as an example, but the present invention is of course not limited to this and can be applied to general synchronous motors.

FIG. 1 is a circuit diagram of a conventional pumped storage generator generator with a silisk starter.

In the figure, 1 and 2 are Cyrisk converters, 3 is a DC reactor connected between them, 4 is a gate circuit for Cyrisk converters 1 and 2, 5 is a current control circuit, 6 is a speed control circuit, and 7 is an operation command device. ．． 8 is a synchronous generator motor (hereinafter referred to as G/M), 9 is a distributor, 10 is a speed generator, 1
1 is a G/M8 excitation device, 12, 22 and 23 are circuit breakers, 13 to 15, 24 and 25 are switches, 16
and 1γ is a switching circuit for selecting a specific one when there are multiple G/Ms controlled by this device, 18 is a synchronous parallel device, 19 is an AC current transformer (hereinafter referred to as ACCT),
20 is a starting transformer, and 21 is a main transformer.

When starting the G/M8 as a synchronous motor, first close the switches 13 and 24 and the circuit breaker 12, then close the circuit breaker 22, and generate the operation command from the operation command device T. The output of converter 2 is supplied to G/M 8 to start it.

Under the control of the gate circuit 4, the output frequency of the 2-thigh risk converter 2 is increased to accelerate the G/M 8.

When the G/M 8 is accelerated and approaches the synchronous speed, the synchronous parallel control device 18 is operated to control the speed so that the phase of the G/M 8 matches the phase of the power supply side.

When the synchronization control device 18 detects that the phases match, the current is set to zero by both the SiRisk converters 1 and 2, and the circuit breaker 23 is closed. The circuit breaker 12 is shut off and the G/M8 is synchronized.

Next, the circuit breaker 22 and the switch 13 are opened, and other G/Ms (not shown) are started one after another in the same manner as described above.

Although not shown in FIG. 1, in order to protect G/M8, a ratio differential detector is provided that detects the difference current using ACCT inserted between the coils of G/M8. M
A grounding relay is usually inserted between 8 and ground.

However, the frequency of the current and voltage flowing between #2 Cyrisk converter 2 and G/M8 changes from 0, that is, DC to commercial frequency (50Hz or 60Hz) when G/M8 starts and stops.
Hz), so ACCT, which is conventionally inserted between G/M8 coils, cannot be used because it saturates in the low frequency range.

4l=2 between Cyrisk converter 2 and G/M8 or G/
If a short circuit accident or two or more points of grounding occur between M8 and the main transformer 21, +1 and ″ from the current side
An overcurrent flows through the +2 cyrisk converters 1 and 2, and an overcurrent flows due to the energy (voltage) generated in the G/M 8.

In the former case, an overcurrent flowing from the power supply side is detected by the ACCT 19, and the current is limited by the current control circuit 5, so that no overcurrent actually occurs.

However, there is no means for detecting the latter overcurrent from G/M8, so the overcurrent continues to flow and the
/There is a high risk of a serious accident resulting in damage to the M8.

Recently, G/M8, Cyrisk converter 1, 2. The main transformer 21, circuit breaker 12, switch 13, and other devices have become larger (
For example, G/M has a capacity of about 300 MVA)
, these devices are often installed in locations isolated from each other, which increases the possibility of a grounding accident occurring between the G/M8 and the 12-Sirisk converter 2 or between the G/M8 and the main transformer 21. It got bigger.

Therefore, the conventional example without a protective device has the disadvantage that it is easy to cause a serious accident.

The purpose of the present invention is to detect the voltage between G/M8 and #2 Cyrisk converter 2 and between G/M8 and main transformer 21, that is, the terminal voltage of G/M8 and its speed (proportional to frequency f). G/M is detected by detecting the ratio of voltage and frequency (V/f), and using the characteristic that V/f becomes abnormal in the event of a short circuit accident.
An object of the present invention is to provide an abnormality detection device for a synchronous motor, especially a power generator for water pumping, which has a function of protecting the motor.

FIG. 2 shows an embodiment of the present invention.

In the figure, 101 is a voltage transformer (hereinafter referred to as PT);
102 is a voltage detector that converts the signal of the PT into a DC voltage or digital signal, and 103 is a signal converter that converts the signal of the speed generator 10 into a DC voltage or digital signal. 104 is a V/f abnormality detector that is supplied with the outputs V and f of the voltage detector 10 and signal converter 103, calculates /f, and detects an abnormality thereof; 105 is the V/f abnormality detector This is a protection logic that controls the excitation device 11 and the operation command device 1 based on the abnormal signal 104, reduces the excitation current, and generates a signal that blocks the gate signals of the &ζ side risk converters 1 and 2.

FIG. 3 shows a detailed block diagram of the V/f abnormality detector 104, which is a feature of the present invention.

In the figure, 201 is a divider that divides the output signal ■ of the voltage detector 102 by the output signal f of the signal converter 103, and 202
203 is an A comparator that detects that the signal (V/f) of the divider 201 has decreased to below the lower limit value, and 203 is a B comparator that detects that the signal V/f has increased beyond the upper limit value. 204
is an OR circuit that takes the OR logic of the signals of both comparators A and B, 2
05 is a prohibition circuit that prevents a false abnormal signal from being generated before or after the start of the G/M8.

The operation of the embodiment of the present invention will be explained with reference to FIG.

Before starting (to), the outputs of the signal converter 103 and the voltage detector 102 are both O, so the divider 2
The output of 01 is undefined and may fall outside the normal V/f range as shown in FIG. 4(C).

Therefore, before starting (the same applies after starting), generation of the V/f abnormal signal is prohibited by the prohibition command shown in (g).

During the acceleration of G/M8, the voltage and speed (i.e. frequency) increase proportionally as shown in (a) and (b), so
The divider output (c) becomes almost constant and within the normal range.

If a short circuit accident occurs at time t1, the voltage drops instantaneously as shown in (a), but the speed (that is, frequency) gradually drops as shown in (b).

Therefore, the divider output (V/f) suddenly decreases as shown in (c) and goes out of the normal range, and the A comparator 20
2 produces an output, so the V/f abnormality detector 104 outputs V/f
Generates an abnormal signal (h).

That is, by instantly detecting an accident and controlling the gate circuit 4 and the excitation device 11 via the protection logic 105, it becomes possible to appropriately protect the G/M 8.

According to one embodiment of the present invention, regardless of the speed of the G/M8 (proportional to the frequency between the #2 Cyrisk converter 2 and the G/M8 and the main transformer 21), i.e. even in the low frequency region Short circuits and grounding faults that occur in the line from the Cyrisk converter 2 to the G/M 8 or the main transformer 21 are reliably and instantaneously detected, and the abnormal signal generated from the V/f abnormality detector 104 is used to detect the G/M 8. It is possible to rapidly reduce the excitation current supplied to the G/M and to stop the Cyrisk converters 1 and 2, which has the effect of reducing overcurrent in a short time and preventing serious accidents such as damage to the G/M. In addition, if an abnormality occurs in the excitation current during operation of the G/M8, the generated voltage will change and the value of V/f will deviate from the normal range, so such an abnormality can also be detected. There is an effect.

Furthermore, in the past, accidents between coils in G/M were handled by ACC.
Since the T was inserted between the coils and its output was detected using a ratio differential method, the current was in the low frequency range at startup and could not be detected.However, in the present invention, the rotation of the G/M Since the frequency f of the terminal voltage (current) is calculated from the number, it has the advantage of being able to detect any low frequency range.This makes it suitable for brushless G/Ms that cannot detect the field current independently. The present invention is also applicable.

In addition, as a 2 frequency conversion device. In addition to the ones illustrated and explained above, it may also be a type using a cycloconverter or other types, and it goes without saying that the application is not limited to G/M, but can also be applied to ordinary synchronous motors. It is.

Furthermore, in the above embodiment, the frequency f is determined from the rotation speed of the G/M, but instead, the frequency may be detected directly from the rotation axis of the G/M, or the frequency may be determined directly from the terminal voltage (current). The signal may also be supplied to the signal converter 103.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of a conventional pumped storage power generator equipped with a silisk starting device, Fig. 2 is a circuit diagram of one embodiment of the present invention, Fig. 3 is a detailed block diagram of a part thereof, and Fig. 4 is a diagram of the present invention. It is a time chart for explaining the invention. 1, 2... Cyrisk converter, 4...
Gate circuit, 7... Operation command device, 8...
...Synchronous generator motor, 10...Speed generator, 1
1... Excitation device, 101... Voltage converter, 102... Voltage detector, 103...
- Signal converter, 104...V/f abnormality detector.

Claims (1)

[Claims] 1. A synchronous motor, a frequency conversion device that is controlled according to the relative position of an armature of the synchronous motor and a field, and supplies variable frequency alternating current to the synchronous motor, and a terminal of the synchronous motor. a device for detecting voltage and its frequency, respectively;
An abnormality detection device for a synchronous motor, comprising: an abnormality detector that calculates a ratio between the terminal voltage and its frequency and generates an output when the ratio falls outside a predetermined range. 2. Claim 1, characterized in that the device for detecting the frequency comprises a speed generator coupled to a synchronous motor and a signal converter that converts the output thereof into a value corresponding to the frequency. Abnormality detection device for synchronous motors.