JPH07245872A - Variable speed generator motor - Google Patents

Abstract

PURPOSE:To prevent the flow of unnecessary current to a system and quickly recover an exciting system by detecting the recovery of a system accident on the basis of a voltage on the high voltage side of a main transformer and removing the accident point of the system and at the same time resetting the operation of converting into an alternating current. CONSTITUTION:A level comparator CP compares the output detected by a voltage detector S provided on the high voltage side of a main transformer 7M with a predetermined set value to output a signal when the detected output is larger than the set value. When a signal is outputted from the comparator CP, the function of a power converter 3 is stopped by a controller 55, and a d. c. current is supplied to a secondary winding through a switch 9 from a d.c. power supply 10 to perform the operation of converting into an alternating current, so that the a.c. component of the primary side of a generator motor is secured. When the accident point is removed from a transmission line by the release of a breaker 6, the system voltage is recovered in the case of two- network transmission line. Thereby, an unnecessary current can be prevented from flowing into the system.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable speed generator-motor, and a secondary winding of the generator-motor in an alternating operation of a fault current flowing through the primary side of the generator-motor when a fault occurs in a power system. AC current after the circuit breaker is released when the recovery of the generator motor terminal voltage after the circuit breaker is released due to the phase shift between the internal voltage of the generator motor and the system voltage due to DC excitation The present invention relates to a variable speed generator-motor that prevents the influence of operation on a system protection system.

[0002]

2. Description of the Related Art Conventionally, for example, a variable speed pumped storage power generation system has been used as one of variable speed generator motors.
Hereinafter, the configuration of the conventional variable speed generator-motor will be described with reference to the configuration diagram of FIG.

In this system, a variable speed generator-motor (hereinafter referred to as generator motor) having a structure in which a three-phase AC exciting current is supplied to a rotor 1, and a variable side generator (secondary winding) of the generator motor is variable. It is composed of a power converter 3 that supplies an alternating excitation current, a water turbine pump 4 that drives a generator motor during power generation, and is driven by the generator motor during pumping, and a control device 5 that controls the power converter 3.

The primary side (primary winding) of the generator motor is connected to the system 2 via a circuit breaker 6 and a main transformer 7M.
The power converter 3 does not perform current conversion by the secondary current command signal that controls the phase / peak value of the secondary current from the control device 5, and the converter transformer 8 connected to the low voltage side of the main transformer 7M. A predetermined AC current is output to the secondary side (secondary winding) of the generator motor from the voltage stepped down via the controller 5 to output a current.

The control device 5 outputs from the power converter 3 such that the rotating magnetic field of the rotor 1 is synchronized with the system frequency f based on the rotation phase ω of the rotor 1 of the generator motor and the system frequency f of the system A. It controls the output current, that is, the phase of the secondary current supplied to the secondary winding of the generator motor. The system frequency f and the slip s of the rotor 1 are obtained based on the speed of the rotating magnetic field of the rotor detected by a detector (not shown), and the speed of the rotor 1 is f (1-s). The secondary magnetic field of No. 1 is supplied with an AC exciting current having a frequency corresponding to the slip s to maintain a constant phase difference with respect to the phase of the system frequency f, so that the rotating magnetic field generated by the rotor 1 has zero slip ( It rotates at the synchronous speed) and becomes the same as the speed of the rotating magnetic field of the stator 2.

As described above, in the present system, since the speed of the rotor 1 can be operated at the rotational speed for which the efficiency is maximized without being restricted by the synchronous speed, highly efficient power generation operation and electric power adjustment during pumping are possible. It can greatly contribute to the adjustment of night power.

In the system as described above, when a three-phase ground fault or a three-phase short-circuit fault occurs in the system A to which the generator motor is connected, a fault current flows through the generator motor to cause a transient secondary winding. A direct current is induced in the line and overvoltage occurs. In order to prevent the destruction of the converter element of the power converter 3 due to this overvoltage, an overvoltage protection device (not shown) connected to the secondary winding is operated to short-circuit the circuit on the secondary winding side to prevent overvoltage. . Further, the voltage input to the power converter 3 also drops sharply, so that the function is temporarily stopped. When the power converter 3 stops functioning, the supply of the exciting current to the secondary winding also stops, so the AC component contained in the failure current flowing in the primary winding of the generator motor becomes small and zero crossing does not occur. The circuit breaker 6 that interrupts the current may cause DC interruption.

Since the breaker 6 on the primary side cannot cut off the direct current, the switch 9 selects the direct current power source 10 when the function of the power converter 3 is stopped in order to prevent the phenomenon that the alternating current component of the fault current decreases. Then, the secondary winding is directly excited from the DC power source 10 to secure the AC portion of the fault current. It should be noted that how to connect the P and N poles of the DC power supply 10 to the U, V and W phase terminals of the rotor winding 1 provided with the three phase winding is specified in advance.

As described above, in the event of a system failure, when the temporary power converter stops functioning, the AC component of the primary failure current is reduced, and the power converter is switched to a DC power source so that the circuit breaker does not cause DC interruption during operation. Securing the minute is called alternating current operation.

[0010]

However, when the secondary winding is DC-excited during the system failure as described above, and the alternating current is used during the failure, the following problems occur. When the power converter 3 is stopped at the time of system failure, the failure current on the primary side can be converted to AC by passing a DC current through the secondary winding, but the rotor 1 is rotating with slippage. The phases of the system A do not always match and they shift, and the output voltage phase of the generator motor generated by this DC exciting current fluctuates with time.

When the failure point occurs on one of the two circuit lines, the voltage must be restored as soon as the circuit breaker of the failure line is opened. In some cases, the phase shift becomes large and the output of the generator motor acts in the direction of suppressing the system voltage, so that the recovery of the output voltage of the generator motor may be slow. Alternating operation at the time of failure is controlled by stopping the power converter 3 after the occurrence of the system failure, and the fault point is removed by the circuit breaker 6, and the control is stopped so that the system voltage is restored. After that, the power converter 3 is restarted to return to the normal operation.

In the conventional control device, the recovery of the system voltage is detected by detecting the generator motor terminal voltage, and when the voltage level returns to a value close to the rating, the switch 9 is opened to cancel the AC conversion at the time of failure, and the power converter 3 Have control to restart.

As described above, if the phase shift at the time of opening the circuit breaker 6 is large, the generator motor terminal voltage does not recover to the rated value, and it is necessary to wait until the phase difference becomes small. Therefore, even if the stop of AC conversion is delayed at the time of a system failure and the failure point is removed, the AC operation continues, so that an unnecessary current is supplied from the generator motor. This may cause the system protection relay near the generator motor to malfunction. On the other hand, generator motor and turbine /
In the pump 4, during the system failure, an imbalance occurs between the mechanical input of the turbine / pump 4 and the electrical output of the generator / motor, and the difference in energy accelerates the generator / motor and the turbine / pump 4, thereby controlling the speed control range. Therefore, in order to shorten the acceleration period, it was necessary to quickly restore the generator motor to normal operation after the system failure was restored.

According to the present invention, when a three-phase ground fault or a three-phase short circuit occurs in the system, the power generation is performed in the AC operation, which is a means for avoiding DC interruption which may occur when the power converter 3 is stopped. The recovery delay of the system voltage after the circuit breaker is opened, which is caused by the phase deviation of the primary current of the generator motor 1 due to the DC excitation of the secondary winding of the motor, and the AC conversion is quickly stopped, The purpose is to prevent the influence on the system protection system due to the AC operation after the breaker is opened.

[0015]

In order to achieve the above object, in the invention described in [Claim 1], the primary winding is connected to a power system through a circuit breaker and a transformer, and the secondary winding is an alternating current. A generator motor to be excited, a power converter that performs predetermined calculation processing based on a signal stepped down via the low voltage side of the transformer to excite the secondary winding with alternating current, and a rotor of the generator motor. A control device that controls the exciting current output from the power converter so that the rotating magnetic field of the rotor is synchronized with the system frequency based on the rotation phase and the system frequency of the power system; and when the system fault occurs, the control device stops the function. In a variable speed generator motor having a direct current power supply for supplying direct current to the secondary winding instead of the power converter, the direct current power supply is used instead of the power converter stopped when a system fault occurs. On the secondary winding When a current is supplied, after the circuit breaker is opened, the detection output detected on the high-voltage side of the transformer is compared with a preset set value, and when the detected output exceeds the set value, The DC power supply to the secondary winding is stopped.

According to a second aspect of the present invention, after the circuit breaker is opened, a comparison is made between a detection voltage detected on the high voltage side of the transformer and a preset setting voltage, and the detection voltage is set. The supply from the DC power supply to the secondary winding is stopped when the voltage becomes equal to or higher than the voltage.

According to a third aspect of the invention, in the invention of the second aspect or the third aspect, the detection is made on the high voltage side of the transformer after the breaker is opened by the opening means. The output is compared with a preset set value, and when the detected output is equal to or greater than the preset value, the power supply from the DC power source to the secondary winding is stopped, and then the power converter is restarted. It is characterized by

[0018]

According to the inventions described in [Claim 1], [Claim 2] and [Claim 3], the system voltage is restored when the system voltage is restored when the system fault is eliminated by opening the circuit breaker. It is better to detect the voltage on the high voltage side (system side) of the main transformer instead of the output end of the generator motor to detect the voltage because there is no voltage drop due to the internal impedance of the main transformer. Can be detected, and the alternating current operation can be reset by comparing this detection output with a preset value. Therefore, it is possible to prevent unnecessary current from flowing to the system.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a configuration diagram of a variable speed generator-motor of the present embodiment. This system includes a variable speed generator motor (hereinafter referred to as generator motor 1) having a configuration in which a three-phase alternating current is supplied to a rotor 1, and a secondary side (secondary winding) of the generator motor.
A power converter 3 that supplies a variable AC exciting current to the turbine, a water turbine / pump 4 that drives a generator motor during power generation and is driven by the generator motor during pumping, and a controller 55 that controls the power converter 3. .

The primary side (primary winding) of the generator motor is connected to the grid A via the main transformer 7M. The power converter 3 inputs the stepped-down signal via the converter transformer 5 connected to the low-voltage side of the main transformer 7M, performs a predetermined calculation process, and performs secondary calculation (secondary winding of the generator motor). ) Is output. On the contrary, the variable frequency power is converted into the commercial frequency power to be regenerated in the system A, and bidirectional power conversion is performed.

The level comparator CP compares the output detected by the voltage detector S provided on the high voltage side (the side connected to the system) of the main transformer 7M with a preset set value, Outputs a signal when the detected output is larger than the set value.

Usually, the set value is a value with which it can be determined that the system has a normal voltage. For example, about 85% to 90% of the rated voltage.
The DC power supply 10 supplies a direct current such that an AC component is generated in the primary winding when the function of the power converter 3 is stopped due to a system fault or the like, and a current generated in the secondary winding is below the zero point. .

Normally, the fault current does not cross zero immediately after the occurrence of the fault, but the DC component gradually attenuates, so that the zero cross occurs by the time when the breaker operates. However,
In the case of a variable speed machine, the converter stops when the overvoltage protection device operates, so that the exciting current disappears and the AC component on the primary side becomes small, which makes it difficult for zero crossing.

FIG. 2 is an attenuation characteristic diagram showing the operation of a fault current when a system fault occurs. FIG. 2A shows the state of decay of the fault current in the case of a constant speed machine. When a system fault occurs at time t1, the current transiently rises, decays with time, cuts off the zero point, and opens the circuit breaker at time t2.
The dotted line in the figure shows the transient DC component.

FIG. 2B shows the state of attenuation of the fault current in the case of the conventional variable speed machine. When a system fault occurs at time t1, the current transiently rises and decays with time as in the case of FIG. 3A, but since the AC component on the primary side is small, it does not pass through the zero point at time t2.

When the power is cut off at the time t2, the direct current is cut off.
FIG. 2C shows the attenuation state of the fault current in the variable speed machine of this embodiment. When a system fault occurs at time t1, the current transiently rises and decays with time as in the case of FIG. 3B, but by performing the AC operation, the amplitude of the AC component increases and the zero point is passed. Therefore, the AC circuit performs the AC operation before the circuit breaker performs the opening operation.

The controller 55 controls the power converter 3 to synchronize the rotating magnetic field of the rotor 1 with the primary side system frequency f1 based on the rotation phase ω of the rotor 1 of the generator motor and the system frequency f of the system A. The output current, that is, the phase of the secondary current supplied to the secondary winding of the generator motor is controlled. Based on the speed of the rotating magnetic field of the rotor 1 detected by a detector (not shown), the system frequency f and the slip s of the rotor 1 are obtained, and the speed of the rotor 1 is f (1-s). Child 1
The rotating magnetic field generated by the rotor 1 rotates at a slip zero (synchronous speed) by supplying an AC exciting current of a frequency corresponding to the slip s to match the phases, and the rotating magnetic field of the stator 1 It will be the same as the speed.

When a signal is output from the level comparator CP, the function of the power converter 3 is stopped, and a DC current is supplied from the DC power supply 10 to the secondary winding through the switch 9 to perform the AC conversion operation. To secure the AC component on the primary side of the generator motor.

With the above configuration, when a system fault occurs, the control device 55 stops the function of the power converter 3 by the signal of the level comparator CP, and the DC power supplies 10 to 2
Excitation current is supplied to the next winding. When the fault point is removed from the transmission line circuit by opening the circuit breaker 6, the system voltage is restored in the case of the two-line transmission line.

The internal electromotive voltage of the generator motor, the output terminal voltage of the generator motor, the high voltage side voltage of the main transformer and the state of the system voltage when the circuit breaker 6 is released are shown in the voltage distribution diagram (A) and voltage vector diagram of FIG. This will be described with reference to (B).

When the circuit breaker 6 of the line at the failure point is opened, the voltage of the line on the healthy side is restored. The voltage distribution at that time is as shown in FIG. That is, the internal constant voltage VG of the generator motor and the system voltage VL are the internal impedance of the generator.
The dance ZG is connected to the impedance ZT of the main transformer 7M and the impedance ZL of the transmission line. Therefore,
The voltage difference between the internal constant voltage VG of the generator motor and the system voltage VL is divided by the ratio of these impedances. The impedance ZT of the main transformer 7M is the impedance Z of the transmission line.
Since it is larger than L, the voltage V2 on the high voltage side of the main transformer 7M
Indicates a value closer to the system voltage VL than the low voltage side V1 of the main transformer 7M. Therefore, if the system voltage signal is taken from the high voltage side of the main transformer 7M, the system voltage recovery can be detected more quickly.

That is, when the voltage phase θ between the constant voltage VG inside the generator motor and the system voltage V2 is greatly deviated,
The generator motor output terminal V1 has a value much lower than the rating.
Since the voltage V2 on the high voltage side of the main transformer 7M is on the system side,
It is possible to obtain a value close to the rating without being greatly affected by the voltage phase difference θ. Therefore, the output level of the voltage detector S is detected by the level comparator CP, and this signal resets the AC operation.

As described above, in the past, in order to reset the AC operation, it was necessary to wait until the voltage phase difference between the generator motor and the system became small. However, according to the present embodiment, the AC operation is performed at the same time as the accident point is removed. Since it can be reset, unnecessary current can be prevented from flowing to the system, and the power converter, which is an exciter, can be restored quickly to normal operation, and due to the imbalance between mechanical input and electrical input in the event of a system failure. It is possible to suppress overspeed of the water turbine / pump.

[0034]

According to the present invention, the system fault recovery is detected on the basis of the voltage on the high voltage side of the main transformer, thereby eliminating the fault point on the system and simultaneously resetting the AC operation. It is possible to obtain a variable-speed generator-motor that prevents unnecessary current from flowing to the excitation system and enables quick recovery of the excitation system.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a variable speed generator-motor of the present embodiment.

FIG. 2 is an attenuation characteristic diagram of the primary side current when a system fault occurs.

FIG. 3 is a voltage distribution diagram and a voltage vector diagram when the breaker of the present embodiment is released.

FIG. 4 is a configuration diagram of a conventional variable speed generator-motor.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Rotor, 2 ... Stator, 3 ... Electric power converter, 4 ... Water turbine / pump, 5, 55 ... Control device, 6 ... Circuit breaker, 7 ... Main transformer, 8 ... Converter transformer, 9 ... Switch , 10 ... DC power supply,
A ... system, S ... voltage detector, CP ... comparator, VG ... generator motor internal voltage, V1 ... generator motor terminal voltage, V2 ... main transformer high voltage side voltage, VL ... system voltage, ZL ... generator motor internal impedance Dance, ZT ... Main transformer impedance,
ZL: system impedance, θ: voltage phase difference.

Claims (3)

[Claims] 1. A generator motor in which a primary winding is connected to a power system via a circuit breaker and a transformer, and a secondary winding is AC-excited, and a signal stepped down via a low voltage side of the transformer is provided. Based on a power converter that performs a predetermined calculation process on the basis of the above to perform AC excitation on the secondary winding, and a rotating magnetic field of the rotor is synchronized with the system frequency based on the rotation phase of the rotor of the generator motor and the system frequency of the power system. A controller for controlling the exciting current output from the power converter, and a DC power supply for supplying DC to the secondary winding instead of the power converter stopped by the controller when a system fault occurs In the variable-speed generator-motor having the above-mentioned, when DC is supplied to the secondary winding by the DC power supply instead of the power converter that is stopped when a system fault occurs, after the circuit breaker is opened, High voltage side of transformer The detected output detected is compared with a preset set value, and when the detected output exceeds a set value, the supply from the DC power supply to the secondary winding is stopped. Variable speed generator motor. 2. After the breaker is opened, a comparison between a detection voltage detected on the high voltage side of the transformer and a preset set voltage is performed, and when the detected voltage becomes equal to or higher than the set voltage, 2. The variable speed generator-motor according to claim 1, wherein the supply of the DC power to the secondary winding is stopped. 3. After the circuit breaker is opened by the opening means, the detection output detected on the high voltage side of the transformer is compared with a preset set value, and the detected output becomes equal to or higher than the set value. The variable speed generator-motor according to claim 2 or 3, wherein the power converter is restarted after the supply of the DC power to the secondary winding is stopped in such a case.