JP2015202008A - Operation stop method for generator and generator system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an operation stop method for generator, capable of suppressing a generator from being rotated by a shaft input after stopping the operation of an inverter.SOLUTION: In the operation stop method for a generator system including: a generator 1 with an input shaft; shaft input variable means 4 for variably controlling a shaft input of the generator 1; and a controller for controlling the inverter 3 and the shaft input variable means, the inverter 3 stops inverter operation after a shaft input is decreased by the shaft input variable means 4 upon reception of a stopping command from the controller.

Description

  The present invention relates to a stopping method for a generator controlled by a power converter.

   The following “free-run stop method” and “deceleration stop method” have been conventionally used as stop methods when stopping the operation of an inverter in a system in which an electric motor or a generator is driven by a power converter (hereinafter referred to as an inverter). Are known.

"Free-run stop method"
When a stop command is input to the inverter, the gate signal to the switching element in the inverter of the inverter is turned off to stop the operation of the inverter. The motor or generator stops after continuing to rotate due to inertia.

`` Deceleration stop method ''
When a stop command is input to the inverter, the motor or generator is decelerated by lowering the output frequency of the inverter, and then the gate signal to the switching element in the inverter is turned OFF to stop the operation of the inverter.

  FIG. 9 shows an example of both types of operation, and FIG. 10 shows an example of a control type of both types. Since the techniques of the “free-run stop method”, “deceleration stop method”, and the control configuration of FIG. 10 are disclosed in Patent Documents 1 to 3, description thereof is omitted here.

Japanese Patent Laid-Open No. 10-42591 JP 2010-161875 A JP 7-123800 A

   FIG. 11 shows a configuration example of both systems, and FIG. 12 shows an example of operation when both systems are stopped.

  In the case of the free-run stop method, the generator 1 is rotated by the shaft input from the prime mover 2 (turbine in FIG. 11). Therefore, when the inverter 3 that controls the generator 1 is stopped, the generator is generated by the shaft input. 1 will rotate. As a result, in some cases, the motor rotates to a speed higher than the rated speed, which may damage a mechanical system such as a bearing. This leads to a deterioration of the service life.

  Even in the case of the deceleration stop method, the generator 1 is stopped by decelerating according to the set deceleration stop time. If the shaft input from the prime mover 2 is still continued at the time of deceleration stop, the generator 1 generates power after stopping. Machine 1 will accelerate. Therefore, the deceleration stop time needs to be set to be longer than the time until the shaft input from the prime mover 2 completely disappears, but the system specifications (valve opening / closing time and input valve (shaft input variable means) 4 to the prime mover 2) Since the time changes due to the difference in altitude of the water pipe 5 between them, it is difficult to set an appropriate time.

  As an example, the system in the case of hydroelectric power generation in FIG. 11 will be described. A turbine 2 is connected to the generator 1. When the inlet valve 4 is opened, water flows through the water pipe 5 into the turbine 2, and the turbine 2 rotates. The inverter 3 controls the speed and torque of the generator 1, and the generated power is regenerated to the power source 7 via the converter 6. When the generator 1 is stopped, the controller 8 issues a command to close the inlet valve 4 and issues a stop command to the inverter 3. Therefore, the inverter 3 may be stopped before the inlet valve 4 is closed and water does not flow into the turbine 2.

  If the system is provided with a means for measuring the flow rate and the inverter 3 is stopped by the controller 8 after the inflow of water and the shaft input from the turbine 2 is lost, the problem that the generator 1 exceeds the rated speed can be avoided. It is. However, since this system requires a means for measuring the flow rate such as a flow rate sensor, there is a problem that it is expensive.

  As described above, in the generator system, when the operation of the generator is stopped, it is a problem to prevent the generator from rotating due to shaft input.

  The present invention has been devised in view of the above-described conventional problems, and one aspect thereof is a generator including an input shaft, an inverter that controls the generator, and a shaft that variably controls the shaft input of the generator. In a generator system comprising an input variable means, and an inverter and a controller for controlling the shaft input variable means, the inverter operates after the shaft input is reduced by the shaft input variable means at the time of a stop command from the controller. It is characterized by stopping.

  Further, as one aspect thereof, the inverter controls the generator speed in accordance with the speed command value even after the stop command from the controller, and the inverter torque command value obtained by calculation using the generator speed command value and the speed detection value. Or stop the inverter operation when the torque detection value of the generator or the torque current component command value or torque current component detection value or the generator output detection value obtained from the control calculation falls below the preset stop judgment value. It is characterized by.

  As another aspect, the inverter controls the torque of the generator according to the torque command value even after the stop command from the controller, and the generator speed detection value or the generator output detection value is equal to or less than the stop determination value. The inverter operation is stopped when

   Further, as another aspect, the inverter includes a torque limit that controls the generator speed according to the speed command value even after the stop command from the controller, and limits the torque command value so as not to become a predetermined value or less. The inverter operation is stopped when the generator speed becomes equal to or less than the stop determination value.

   The inverter controls the torque of the generator according to the torque command value even after the stop command from the controller, and sets the torque command decrease start speed at a speed higher than the stop determination value at that time, and the speed detection value is the torque When it becomes lower than the command decrease start speed, the torque command value of the inverter is decreased.

  According to the present invention, in the generator system, when the operation of the generator is stopped, the generator can be prevented from rotating due to the shaft input.

3 is a time chart showing the operation of the generator operation stop method according to Embodiment 1. FIG. FIG. 3 is a control block diagram illustrating a generator operation stop method according to the first embodiment. The time chart which shows operation | movement of the operation stop method of the generator in Embodiment 2. FIG. The control block diagram which shows the operation stop method of the generator in Embodiment 2. FIG. 10 is a time chart showing the operation of the generator operation stop method according to Embodiment 3. FIG. 5 is a control block diagram illustrating a generator operation stop method according to a third embodiment. 9 is a time chart showing the operation of the generator operation stop method according to Embodiment 4. FIG. 6 is a control block diagram illustrating a generator operation stop method according to a fourth embodiment. The time chart which shows the operation | movement of a free run stop system and a deceleration stop system. Control block diagram of free-run stop method and deceleration stop method. Configuration diagram of free-run stop method and deceleration stop method. The time chart which shows the operation | movement of a free run stop system and a deceleration stop system.

  Hereinafter, Embodiments 1 to 4 of the method for stopping a generator according to the present invention will be described in detail with reference to FIGS.

[Embodiment 1]
FIG. 1 shows the operation of the system of the first embodiment, and FIG. 2 shows the control configuration of the system of the first embodiment.

  The first embodiment is a system that performs speed control according to a speed command. Based on FIG. 2, the stop method of the generator controlled by the power converter device in the first embodiment will be described.

  First, the speed controller 11 compares the speed command with the detected speed value, and converts it into a torque command based on the deviation. Next, the current control unit 12 converts the torque command into a d-axis current command and a q-axis current command value. The current control unit 13 compares the d-axis current command and the q-axis current command with the d-axis current detection and the q-axis current detection, and calculates the d-axis voltage command and the q-axis voltage command based on the deviation. The two-phase / three-phase converter 14 converts the d-axis voltage command and the q-axis voltage command into a three-phase voltage command. The PWM conversion unit 15 compares the three-phase voltage command with the triangular wave carrier signal and outputs it to the AND circuit 18 as a gate command.

  The stop determination unit 16 compares the torque command and the stop determination value, and outputs an OFF signal to the switch 17 when the torque command value is equal to or less than the stop determination value. In other words, when the torque command is larger than the stop determination value, an ON signal is output to the switch 17. The switch 17 outputs an operation command ON when the operation command is ON, and outputs an OFF signal when the operation command is OFF and an OFF signal is input from the stop determination unit 16. The AND circuit 18 outputs a gate command as a gate signal to the semiconductor switching element of the inverter when the signal input from the switch 17 is an ON signal, and outputs a gate signal when the signal input from the switch 17 is an OFF signal. Shall not.

  Next, based on FIG. 1, the system operation | movement of this Embodiment 1 is demonstrated. After the operation command is turned off (that is, the stop command is turned on), the opening of the inlet valve is reduced to reduce the shaft input of the generator 1.

  On the other hand, the inverter continues to operate by controlling the generator speed in accordance with the speed command (100% in FIG. 1) even after the operation command is turned off. As the shaft input of the generator 1 decreases, the torque command necessary for controlling the speed also decreases.

  When the torque command output from the speed control unit 11 falls below a certain value (stop determination value in FIG. 1), the gate signal is turned off to stop the inverter operation. In FIG. 1, the shaft input of the generator 1 is 0% before the input valve opening is 0%, which is due to the characteristics of the hydroelectric turbine.

  During the period from the operation command ON → OFF of the first embodiment to the gate signal OFF, the generator shaft input is nearly equal to the power generation speed × torque, so the value of the shaft input of the generator 1 and the torque command are substantially proportional. Therefore, according to the present system in which the inverter operation is stopped when the torque command falls below a predetermined value (stop determination value in FIG. 1), the inverter is reliably operated when the shaft input of the generator 1 is less than the predetermined value. You can stop.

  Therefore, an increase in the generator speed after the inverter is stopped can be suppressed as compared with the conventional free-run stop method and deceleration stop method that do not consider the shaft input of the generator 1 when the inverter is stopped. Note that the slight increase in the speed detection value immediately after the gate signal OFF in FIG. 1 occurs because the shaft input of the generator 1 remains slightly when the gate signal is OFF because the torque command value of the stop determination value is not zero. To do.

  In the first embodiment, the stop determination value for stopping the operation is set in the torque command. However, this stop determination value is a torque current component command obtained from the torque detection value T or the control calculation in the inverter instead of the torque command. A value, a torque current component detection value, a generator output detection value, etc. may be substituted for those related to active power components.

  In the first embodiment, the speed command value is constant at 100%, but the present invention is not limited to this. The same applies to the opening of the inlet valve, and the relationship between the opening of the valve and the shaft input of the generator 1 naturally varies depending on the system. This is the same for the second to fourth embodiments described later.

   As described above, according to the first embodiment, since the shaft input of the generator 1 is small when the inverter operation is stopped, the generator is rotated by the shaft input even when the operation is stopped. Can be suppressed. Moreover, it becomes possible to stop after the input of the generator 1 is reliably lowered regardless of the system specifications or the power generation status. As a result, it is possible to suppress deterioration of the generator 1 and extend the life of the system. Furthermore, according to the first embodiment, a flow rate sensor is not necessary, so that cost reduction can be realized.

[Embodiment 2]
FIG. 3 shows the operation of the system of the second embodiment, and FIG. 4 shows the control configuration of the system of the second embodiment. A description of the same points as in the first embodiment will be omitted, and only differences from the first embodiment will be described.

  The second embodiment is a system that controls torque according to a torque command. Therefore, the speed control unit 11 in the first embodiment is omitted. Moreover, the input of the stop determination part 16 becomes a speed detection value. Others are the same as in the first embodiment.

  Next, based on FIG. 3, the system operation | movement of this Embodiment 2 is demonstrated. After the operation command is turned off (that is, the stop command is turned on), the opening of the inlet valve is reduced to reduce the shaft input of the generator 1.

  On the other hand, the inverter continues to control the torque of the generator 1 according to the torque command (100% in FIG. 3) and continues to operate. Even if the shaft input of the generator 1 decreases, if the torque is continuously applied, the speed of the generator 1 decreases. Then, when the speed detection value falls below the stop determination value, the gate signal is turned off to stop the inverter.

  During the period from the operation command ON → OFF of the second embodiment to the gate signal OFF, the generator shaft input is nearly equal to the power generation speed × torque, so the value of the shaft input of the generator 1 and the speed detection value are substantially proportional. . Accordingly, when the speed detection value falls below a predetermined value (stop determination value in FIG. 3), the inverter is stopped when the shaft input of the generator 1 is less than or equal to the predetermined value by this method of stopping the inverter operation. You can stop. Therefore, an increase in the speed of the generator 1 after the inverter is stopped can be suppressed as compared with a conventional free-run stop method or a deceleration stop method that does not consider the shaft input of the generator 1 when the inverter is stopped. The increase in the speed detection value ω immediately after the gate signal OFF in FIG. 3 occurs because the shaft input of the generator 1 remains when the gate signal is OFF because the stop determination value speed is not zero.

  The parameter for stopping the operation may be replaced with a generator output detection value instead of the speed detection value.

  In the second embodiment, the torque command value is set to be 100% constant, but the present invention is not limited to this. The same applies to the input valve opening and the generator shaft input.

[Embodiment 3]
FIG. 5 shows the operation of the system of the third embodiment, and FIG. 6 shows the control configuration of the system of the third embodiment.

  In the first embodiment, after the operation command is turned OFF, when there is a disturbance and the shaft input temporarily decreases, the speed control unit 11 decreases the torque command to control the speed, or the control response of the speed control unit 11 is high. In the case where the torque command is set, the torque command fluctuates excessively when the load suddenly changes, so the torque command may be less than the stop determination value.

  In such a case, the inverter is stopped in a state where the shaft input of the generator 1 is not reduced by adjusting the opening of the inlet valve, and therefore the generator 1 is accelerated after the inverter stops. .

  Therefore, a torque limiter 19 is provided as shown in FIG. 6, and limit processing is performed so that the torque command does not become a predetermined value (limit value in FIG. 6) or less. Thereafter, when the speed decreases and the speed becomes equal to or lower than a predetermined value (stop determination value in FIG. 5), the gate signal is turned OFF to stop the inverter. The limit value of the torque command is preferably zero or a value close thereto.

  In the third embodiment, the problem that the torque command falls below the stop determination value and stops the inverter due to a temporary decrease of the shaft input that may occur at the time of the occurrence of the disturbance or the response of the speed control unit 11 can be solved.

  Therefore, compared with Embodiment 1, it becomes possible to stop the generator 1 more reliably without accelerating it.

[Embodiment 4]
FIG. 7 shows the operation of the system of the fourth embodiment, and FIG. 8 shows the control configuration of the system of the fourth embodiment.

  In the second embodiment, when the operation of the inverter is stopped when the speed detection value falls below a predetermined value (stop determination value), when the generator 1 is not stopped after the speed is completely zero. The generator 1 is somewhat accelerated. The degree of acceleration increases as the shaft input or torque command of the generator 1 when the inverter is stopped increases.

  Therefore, a predetermined speed (torque command reduction start speed in FIG. 7) for decreasing the torque command at a speed higher than the stop determination value is set. When the speed detection value becomes lower than the torque command value decrease start speed, the torque command is decreased according to the speed of the stop determination value and the current speed detection value. Further, the torque command (after correction) during the torque command decrease period of FIG. 7 is calculated and corrected by the control block 20 shown in FIG.

  Here, the control block 20 will be described with reference to FIG. First, the subtraction unit 21 subtracts the detected speed value ω from the torque command decrease start speed. The limiter 23 outputs zero when the output of the subtractor 21 is a negative value. If the input is greater than zero, the value is output as is. The subtraction unit 22 subtracts the stop determination value from the torque command decrease start speed. The division unit 24 divides the output of the limiter 23 by the output of the subtraction unit 22, and the multiplication unit 25 multiplies the torque command by the output of the division unit 24.

  The switch 26 outputs 0 when the operation command is an ON signal, and outputs the output of the multiplier 25 when the operation signal is an OFF signal. The subtracting unit 27 subtracts the output of the switch 26 from the torque command and outputs a torque command (after correction).

  In the fourth embodiment, the torque command of the inverter is decreased when the speed detection value is equal to or lower than a predetermined value (torque command decrease start speed), and the inverter is turned on when the speed detection value becomes equal to or lower than the predetermined value (stop determination value). Stop.

  Thereby, the fall of the shaft input of the generator 1 at the time of an inverter stop becomes more reliable. Therefore, compared with Embodiment 2, the generator 1 can be stopped more reliably without acceleration.

  Although the torque command correction calculation as shown in FIG. 8 is performed in the fourth embodiment, any calculation method may be used as long as the torque command is corrected so as to decrease the torque command before the inverter stops.

   In the above first to fourth embodiments, the hydroelectric power generation system that controls the flow rate of water by opening and closing the inlet valve has been described as an example. The present invention can be applied to other power generation systems as long as the system has a function capable of controlling the generator shaft input corresponding to the inlet valve of the first to fourth embodiments.

1 ... Generator 2 ... Motor (turbine)
3 ... Inverter 4 ... Input valve (shaft input variable means)
8 ... Controller 16 ... Stop determination unit 17 ... Switch 19 ... Torque limiter 20 ... Control block

Claims (6)

A generator with an input shaft;
An inverter for controlling the generator;
Shaft input variable means for variably controlling the shaft input of the generator;
A controller for controlling the inverter and the shaft input variable means;
In the generator system with
The inverter is
A method of stopping an operation of a generator, characterized in that an inverter operation is stopped after a shaft input is reduced by a shaft input variable means when a stop command is issued from a controller. The inverter is
Even after the stop command from the controller, the generator speed is controlled according to the speed command value, and the inverter torque command value or the generator torque detection value or control calculation obtained from the calculation using the generator speed command value and the speed detection value 2. The power generation according to claim 1, wherein the inverter operation is stopped when a torque current component command value, a torque current component detection value, or a generator output detection value obtained by the method becomes equal to or less than a preset stop determination value. How to stop the machine. The inverter is
Even after the stop command from the controller, the generator torque is controlled according to the torque command value, and the inverter operation is stopped when the generator speed detection value or the generator output detection value falls below the stop judgment value. The method for stopping the operation of the generator according to claim 1. The inverter is
Even after the stop command from the controller, the generator speed is controlled according to the speed command value. At that time, a torque limit is set to limit the torque command value so that it does not fall below a certain value, and the generator speed falls below the stop judgment value. 3. The method of stopping the operation of a generator according to claim 2, wherein the inverter operation is sometimes stopped. The inverter is
Even after the stop command from the controller, the torque of the generator is controlled according to the torque command value, the torque command decrease start speed at a speed higher than the stop judgment value is set,
4. The method for stopping the operation of a generator according to claim 3, wherein when the detected speed value becomes lower than the torque command decrease start speed, the torque command value of the inverter is decreased.   A generator system, wherein the generator is stopped by the operation stop method according to claim 1.

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