JPH0410320B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a device for preventing disturbances in a synchronous motor during recovery from an instantaneous voltage drop in a power system.

[Technical background of the invention and its problems]

Commonly used synchronous motors often experience disturbances due to excessive power flowing into them when recovering from an instantaneous voltage drop in the power system to which it is connected. In other words, this means that the load angle of the synchronous motor increases during instantaneous voltage drops and even voltage drops.
When the grid voltage recovers after this load angle has greatly expanded, transient impedance acts due to the sudden change in voltage, so excessive power flows in with the large load angle, and a new load angle based on the transient impedance is generated. It vibrates around the center, and if this vibration angle becomes too large, it will lose synchronization and stop.

Therefore, no direct method has been implemented to prevent such disturbances, and an indirect method is to reduce the resistance value of the damper winding.
Methods such as increasing the unit inertia constant, increasing the escape torque, decreasing the synchronous impedance, and increasing the excitation have been adopted, but these are only measures to increase the transient stability, and the above-mentioned disturbances There is a strong demand for a method to reliably suppress this.

[Purpose of the invention]

The present invention was made in response to the above-mentioned demands, and its purpose is to suppress the inflow of excessive power by suppressing the recovery of the internal induced voltage before excessive power inflows when the system voltage is restored. An object of the present invention is to provide a disturbance prevention device for a synchronous motor that can prevent disturbance vibrations.

[Summary of the invention]

In order to achieve the above object, the present invention provides a disturbance prevention device for a synchronous motor comprising an armature winding connected to a power system and an armature winding connected to an exciter. an internal voltage suppressor which is formed by connecting switches in parallel and is inserted in series in the field circuit of the synchronous motor, and detects that the voltage of the armature circuit of the synchronous motor is equal to or higher than a predetermined value; A voltage detection relay that performs the second operation, and a power detection relay that performs the second operation when it detects that the power based on the voltage and current of the armature circuit of the synchronous motor is below a predetermined value. 1st
The second operation of the power detection relay opens the switch (because the power grid voltage has recovered to a predetermined value or higher), and the switch is re-closed due to the second operation of the power detection relay (because the incoming power has decreased to a predetermined value or less). It is configured to do so.

[Embodiments of the invention]

An embodiment of the present invention shown in the drawings will be described below. The figure shows an example of the configuration of a synchronous motor disturbance prevention device according to the present invention. In the figure,
1 is a synchronous motor equipped with an armature winding 1a and a field winding 1b, and the armature winding 1a is connected to a power system (not shown) via a motor primary switch 2 to form an armature circuit. The field winding 1b is connected via a field switch 3 to an exciter 4 connected to the power system to form a field circuit.

On the other hand, 5 is a resistor, and 6 is a switch, which are connected in parallel to form an internal voltage suppressor, which is inserted in series into the field circuit of the synchronous motor 1.
Further, 7 is a voltage transformer that detects the voltage of the armature circuit of the synchronous motor 1, and 8 is a current transformer that similarly detects the current of the armature circuit. Further, reference numeral 9 denotes a voltage detecting device that performs a first operation upon detecting that the output voltage of the voltage transformer 7 is equal to or higher than a predetermined value (equivalent to the system circuit voltage value), and the first operation causes the switch I'm trying to leave 6 open. 10
is a power detection relay that performs a second operation by detecting that the output power based on the output voltage of the voltage transformer 7 and the output current of the current transformer 8, that is, the inflow power of the synchronous motor 1 is below a predetermined value. Then, the switch 6 is closed by the second operation.

Here, the first operation of the voltage detection relay 9 is as follows:
The voltage detection relay 9 detects that the output voltage of the voltage transformer 7 is equal to or higher than a predetermined value (hereinafter referred to as "predetermined value or higher detection"), and detects a change from the non-energized state before detection to the energized state. This is an operation indicating that a state has been reached in which it is possible to transmit to the subsequent circuit that the above-mentioned "predetermined value or more detection" has been performed.

Similarly, the second operation of the power detection relay 10 means that the power detection relay 10 operates based on the output voltage of the voltage transformer 7 and the output current of the current transformer 8, that is, when the inflow power of the synchronous motor 1 is below a predetermined value. This refers to a change in state from the non-energized state before detection to the energized state when a certain state is detected (hereinafter referred to as "detection of less than a predetermined value"), and the above-mentioned "detection of less than a predetermined value" is performed on the subsequent circuit. This is an action that indicates that the person is now in a state where they can communicate something.

In this configuration, normally the switch 6 and the field switch 3 are in the closed state, the field winding 1b of the synchronous motor 1 is excited with a predetermined excitation current by the exciter 4, and the motor primary switch 2 is in the on state, power is supplied from the power grid, and the synchronous motor 1 is operated at a predetermined speed.

In this state, if the voltage in the power system momentarily drops and recovers, the voltage detection relay 9 performs the first operation upon detecting that this instantaneous voltage drop has recovered, and the voltage detection relay 9 performs the first operation. The operation opens the switch 6 and inserts the resistor 5 in series into the field circuit of the synchronous motor 1. On the other hand, as the grid voltage is restored, the synchronous motor 1 accelerates and reduces the load angle. The power detection relay 10 detects that the inflow power of the synchronous motor 1 has decreased to a predetermined value and performs the second operation, and the second operation of the power detection relay 10 causes the switch 6 to open again. Injected. Therefore, it is possible to prevent excessive power from flowing into the first half cycle during load angular oscillation, and since the power supply voltage of the exciter 4 has already been recovered after that, the previous excitation is restored according to the time constant of the field circuit. The current will be restored.

As can be seen from the above, excessive power flows into the power system during the time it takes to accelerate from the load angle at the time of the voltage drop to the load angle at the time of voltage recovery, and the excess power causes the system to accelerate too much, and then attempts to decelerate to the new load angle. In order to prevent such vibrations from repeating, excessive power flowing in during the first half period of vibration is suppressed, and disorderly vibrations are prevented by reducing the excess or deficiency of power. Therefore, other systemically weak synchronous motors connected to the same power system will not be agitated by beat vibrations, so by applying this device to relatively large motors, small motors can also be used as secondary motors. This has the advantage of avoiding loss of synchronization. On the other hand, from a production perspective, it has an extremely large effect on equipment for chemical plants and the like that require a long period of time to restart.

〔Effect of the invention〕

As explained above, according to the present invention, the voltage of the internal voltage suppressor, which is formed by connecting a resistor and a switch in parallel and is inserted in series in the field circuit of the synchronous motor, and the armature circuit of the synchronous motor is A voltage detection relay that performs a first operation when detecting that the voltage is above a predetermined value, and a second operation when detecting that the power based on the voltage and current of the armature circuit of the synchronous motor is below a predetermined value. a power detection relay to open the switch (when the power system voltage has recovered to a predetermined value or higher) by the first operation of the voltage detection relay;
The second operation of the power detection relay turns on the switch again (when the inflow power decreases below a predetermined value), so the internal induced voltage is reduced before excessive power flows in when the grid voltage is restored. By suppressing recovery, it is possible to provide a highly reliable synchronous motor disturbance prevention device that can suppress the inflow of excessive power and prevent disturbance vibration.

[Brief explanation of drawings]

The figure is a circuit configuration diagram showing an embodiment of the present invention. 1...Synchronous motor, 1a...Armature winding, 1b
... Field winding, 4 ... Exciter, 5 ... Resistor, 6
... Switch, 7 ... Voltage transformer, 8 ... Current transformer, 9 ... Voltage detection relay, 10 ... Power detection relay.

Claims (1)

[Scope of Claims] 1. A disturbance prevention device for a synchronous motor comprising an armature winding connected to a power system and an armature winding connected to an exciter, in which a resistor and a switch are connected in parallel. an internal voltage suppressor inserted in series in the field circuit of the synchronous motor; and a voltage that performs the first operation upon detecting that the voltage of the armature circuit of the synchronous motor is equal to or higher than a predetermined value. a detection relay; detects that the power based on the voltage and current of the armature circuit of the synchronous motor is below a predetermined value;
and a power detection relay that performs the following operations, and is configured to open the switch by a first operation of the voltage detection relay, and close the switch again by a second operation of the power detection relay. A synchronous motor disturbance prevention device characterized by: