JP4398440B2 - Wind power generator - Google Patents

Description

  The present invention relates to a wind turbine generator that suppresses output fluctuations of a synchronous generator driven by a windmill.

  A conventional wind power generation system will be described. The windmill is connected to a synchronous generator, the windmill rotates by wind energy, and the synchronous generator generates electricity when the windmill drives the synchronous generator. The AC power output from the synchronous generator is converted into DC power by a forward converter, and further converted into AC power of commercial frequency by an inverse converter and supplied to the power system. As an example, Japanese Patent Laid-Open No. 2000-345952 discloses a wind power generation system having such a configuration.

  On the other hand, wind power generation systems are greatly influenced by fluctuations in wind speed, and output fluctuations caused by wind speed fluctuations will fluctuate the frequency and voltage of the power system and adversely affect the power system. Therefore, it is essential to suppress such output fluctuations.

  Therefore, in recent wind turbines, a method of suppressing output fluctuations caused by wind speed fluctuations by performing pitch control that adjusts the mechanical input to the wind turbines by changing the angle of the wind turbine blades according to the wind speed is adopted. It is done. Further, synchronous generator output control by a forward converter is also performed.

  However, it is difficult for the above prior art to generate power with high efficiency while suppressing output fluctuation with high response. This is because the wind turbine has a rotational speed at which the wind energy can be received most efficiently at each wind speed. Therefore, in order to obtain the maximum efficiency, the wind speed is detected, and the rotational speed of the wind turbine is determined according to the wind speed. This is because it is necessary to control.

  The object of the present invention is to perform high-efficiency operation by controlling the rotational speed with priority when the wind speed is weak, and control the wind power by prioritizing the effective power output from the synchronous generator when the wind speed is strong. It is providing the wind power generator which suppresses the output fluctuation | variation resulting from a fluctuation | variation.

  In order to achieve the above object, according to the present invention, a synchronous generator connected to a wind turbine shaft and variable frequency generated power of the synchronous generator connected to a stator of the synchronous generator are converted into DC power. A wind turbine generator comprising: a converter that converts the DC power connected between the converter and the power system into AC power having a fixed frequency and supplies the AC power to the power system. Rotation speed detection means for detecting the rotation speed, rotation speed command calculation means for obtaining an efficient rotation speed based on a detection value from the wind speed detector for detecting the wind speed, and a rotation speed command from the rotation speed command calculator Rotation speed control means for obtaining an active power command from the rotation speed of the rotation speed detector, and the output of the synchronous generator from the active power command from the rotation speed controller and the active power from the synchronous generator. Electricity to control Control means, and by adjusting the control gain of the rotational speed control means according to the wind speed state, the rotational speed of the windmill is controlled with priority, or the effective power output from the synchronous generator is It is characterized by priority control.

  According to the present invention, by adjusting the control gain of the rotational speed controller, it is possible to switch between the operation that prioritizes the rotational speed of the windmill or the active power that is output from the synchronous generator. Therefore, when the wind speed is low, high-efficiency operation is performed by controlling the rotation speed of the synchronous generator with priority, and when the wind speed is strong, the effective power output by the synchronous generator is prioritized and controlled. There is an effect of suppressing output fluctuation caused by fluctuation.

  An embodiment according to the present invention will be described below with reference to the drawings. FIG. 1 shows the overall configuration of an embodiment of the present invention.

  In FIG. 1, the rotor of the synchronous generator 2 is connected to the shaft of the windmill 1, and when the windmill 1 is rotated by wind energy, the synchronous generator 2 is AC power having a variable frequency corresponding to the rotational speed of the windmill 1. Is generated.

  A forward converter 3 is connected to the stator of the synchronous generator 2, and variable frequency AC power generated by the synchronous generator 2 is converted into DC power by the forward converter 3. The forward converter 3 is connected to the inverse converter 5 via a direct current capacitor 4 with a direct current, and the inverse converter 5 converts the direct current power sent from the forward converter 3 into alternating current power having a fixed frequency. The reverse converter 5 is connected to the power system via the grid interconnection transformer 6 and supplies AC power of a fixed frequency to the power system.

  A voltage detection sensor 7 and a current detection sensor 8 are installed between the synchronous generator 2 and the forward converter 3. The voltage detection sensor is a terminal voltage of the synchronous generator 2, and the current detection sensor 8 is a synchronous generator. Each of the currents flowing through the two stators is detected. The detected voltage and current values are converted by the three-phase / two-phase converter 17 into a two-axis component of an effective component and an ineffective component.

  The active power detector 9 detects the active power output from the synchronous generator 2 based on the two-axis component signal output from the three-phase / two-phase converter 17, and the reactive power detector 10 is the three-phase / 2-phase. Based on the biaxial component signal output from the converter 17, the reactive power output from the synchronous generator 2 is detected. The rotational speed detector 11 detects the rotational speed of the windmill 1.

  The input of the rotational speed controller 12 is a deviation between the rotational speed of the windmill 1 detected by the rotational speed detector 11 and the rotational speed command, and the output is an active power command to the forward converter 3. The rotational speed controller 12 is configured by a proportional-integral control system, for example. As for the rotational speed command, the wind speed detector 21 detects the wind speed, and based on the detected value, the rotational speed command calculator 22 obtains the rotational speed at which the wind energy can be received most efficiently and supplies the rotational speed command to the rotational speed controller 12. Output as rotation speed command.

  When the rotational speed of the windmill 1 is higher than the rotational speed command, the output of the rotational speed controller 12 is increased, which means that the active power command to the forward converter 3 is increased, and the synchronous generator 2 The effective power to be output increases.

  As a result, when the active power output from the synchronous generator 2 becomes larger than the mechanical input given to the windmill 1 from the wind, the input becomes insufficient, but the input shortage is stored in the blade of the windmill 1. Since it is compensated from the inertial energy, the rotational speed of the windmill 1 decreases and follows the rotational speed command.

  On the contrary, when the rotational speed of the windmill 1 is smaller than the rotational speed command, the output of the rotational speed controller 12 becomes small, which means that the active power command to the forward converter 3 becomes small, and the synchronous generator 2 The effective power output from the is reduced.

  As a result, when the effective power output from the synchronous generator 2 becomes smaller than the mechanical input given from the wind to the wind turbine 1, the input becomes surplus, but the surplus input is stored as inertia energy in the blade of the wind turbine 1. As a result, the rotational speed of the windmill 1 increases and follows the rotational speed command. That is, the rotational speed of the windmill 1 can be controlled according to the increase or decrease of the output of the synchronous generator 2.

  As can be seen from the relationship between the rotational speed of the windmill 1 and the mechanical input from the wind shown in FIG. 2, the windmill 1 has a rotational speed at which wind energy can be received most efficiently for each wind speed. That is, in order to obtain the maximum efficiency, the windmill 1 needs to change the rotation speed depending on the wind speed. Therefore, the wind speed detector 21 detects the wind speed, and based on the detected value, the rotational speed command calculator 22 obtains the rotational speed at which the wind energy can be received most efficiently, and the rotational speed to the rotational speed controller 12 is obtained. Output as a command. When the windmill 1 is operated based on this rotational speed command, it becomes possible to receive wind energy efficiently.

  The input of the active power controller 13 is a deviation between the active power command output from the rotation speed controller 12 and the detected active power value detected by the active power detector 9, and the output is an effective component of the current command to the forward converter 3. It becomes. The input of the reactive power controller 14 is a deviation between the reactive power command given from the outside and the reactive power detection value detected by the reactive power detector 10, and the output is the reactive part of the current command to the forward converter 3.

  Both the active power controller 13 and the reactive power controller 14 are configured by, for example, a proportional integral control system so that the deviation between the active power command and the active power detection value and the deviation between the reactive power command and the reactive power detection value become zero. A current command to the forward converter 3 is determined. The reactive power and the active power can be controlled independently. For example, when the reactive power command is set to zero, the forward converter 3 is operated at a power factor of 1.

  In addition, the terminal voltage of the synchronous generator 2 can be controlled by adjusting the reactive power command, and the terminal voltage of the synchronous generator 2 can be kept low even when the rotational speed of the synchronous generator 2 increases. There are merits such as.

  The input to the current controller 15 includes the current detected value of the biaxial component output from the three-phase / two-phase converter 18, the effective amount in the current command to the forward converter 3 output from the active power controller 13, and reactive power This is an invalid portion of the current command to the forward converter 3 output from the controller 14, and the output is an output voltage command to the forward converter 3. The current controller 15 is configured by, for example, a proportional-integral control system, and determines an output voltage command to the forward converter 3 so that the deviation between the detected current value and the current command becomes zero.

  Although omitted in FIG. 1, the current controller 15 is actually composed of an active current controller 19 that controls an effective amount of current and a reactive current controller 20 that controls an ineffective portion of current as shown in FIG. 3. The Since the output voltage command to the forward converter 3 output from the current controller 15 is a voltage command of a two-axis component, it is converted into a three-phase voltage command by the two-phase / three-phase converter 18.

  The pulse generator 16 outputs a gate pulse signal to the forward converter 3 by PWM (Pulse Width Modulation) based on the three-phase output voltage command to the forward converter 3 output from the two-phase / three-phase converter 18. To do. The forward converter 3 receives a gate pulse signal, and a switching element such as an IGBT performs switching at high speed, so that the forward converter 3 outputs a voltage corresponding to the command.

  With the configuration of the control system as described above, it is possible to control the rotational speed of the windmill 1 and to control the active power and reactive power output from the synchronous generator 2. Here, when the control gain of the rotational speed controller 12 is set high, the control response of the rotational speed of the windmill 1 increases as the changing speed of the active power command to the forward converter 3 increases. However, since the change of the active power command to the forward converter 3 becomes large, the fluctuation of the active power output from the synchronous generator 2 becomes large. FIG. 4 shows a waveform example of the rotational speed of the wind turbine 1 at this time and the active power output from the synchronous generator 2.

  As shown in FIG. 4, although the fluctuation | variation of the rotational speed of the windmill 1 is restrained small, the active electric power which the synchronous generator 2 outputs changes a lot. Conversely, when the control gain of the rotational speed controller 12 is set low, the rotational speed control response of the windmill 1 decreases as the change speed of the active power command to the forward converter 3 decreases. However, since the change in the active power command to the forward converter 3 is small, the variation in the active power output from the synchronous generator 2 is small. FIG. 5 shows a waveform example of the rotational speed of the windmill 1 at this time and the active power output from the synchronous generator 2.

  As shown in FIG. 5, although the fluctuation | variation of the rotational speed of the windmill 1 becomes large, the fluctuation | variation of the active electric power which the synchronous generator 2 outputs can be suppressed small. That is, by adjusting the control gain of the rotation speed controller 12, it is possible to adjust whether the rotation speed of the wind turbine 1 is controlled with priority or the active power output from the synchronous generator 2 is controlled with priority. .

  FIG. 6 shows the relationship between the wind speed and the power generation output. Since the wind energy is proportional to the cube of the wind speed, the power generation output increases as the wind speed increases. On the other hand, when the wind speed exceeds the rating, the wind turbine 1 performs pitch control, thereby releasing the wind energy received by the blades, thereby keeping the power generation output constant. Here, in order to give priority to efficiency when the wind turbine 1 is less than the rated wind speed, the wind speed is controlled with priority on the rotational speed. On the other hand, in order to obtain a constant output with little fluctuation above the rated wind speed, the active power is controlled with priority.

  Therefore, the control gain of the rotational speed controller 12 is switched according to the wind speed detected by the wind speed detector 21. That is, the control gain is set high when the wind speed is lower than the rated wind speed, and is set low when the wind speed is higher than the rated wind speed. Further, when the control gain of the rotation speed controller 12 is changed, the control response speed of the rotation speed controller 12 is changed accordingly.

  Since the active power controller 13 determines the active current command according to the active power command output from the rotation speed controller 12, the control response speed of the rotation speed controller 12 is greater than the control response speed of the active power controller 13. Need to set too late. Usually, the control response speed of the rotation speed controller 12 is set to a range that is between about 5 to 300 times the control response speed of the active power controller 13.

  As described above, it is possible to control the rotational speed of the wind turbine 1 and the effective power output from the synchronous generator 2. If the wind speed is lower than the rated wind speed, the rotational speed of the synchronous generator 2 is preferentially controlled to achieve high efficiency. When the wind speed is higher than the rated wind speed, it is possible to suppress the output fluctuation caused by the wind speed fluctuation by controlling the active power output from the synchronous generator 2 with priority.

  In addition, a rotation speed detector for detecting the rotation speed of the windmill and a rotation speed command calculator for obtaining an efficient rotation speed based on a detection value from the wind speed detector for detecting the wind speed are provided. The difference between the rotation speed of the motor and the rotation speed command calculator is input to the rotation speed controller, and the difference between the active power command from the rotation speed controller and the effective power from the synchronous generator is input. The power controller can control the output of the synchronous generator according to the active power command, and can control the rotational speed of the windmill 1 according to the increase or decrease of the output of the synchronous generator. That is, since the rotational speed of the windmill 1 is controlled by the synchronous generator, the mechanism and control of the windmill 1 can be simplified.

The block diagram of the wind power generator to which this invention is applied. The characteristic view which shows the relationship between a rotational speed and mechanical input. FIG. 2 is a detailed view of a current controller used in FIG. 1. The characteristic view which shows the example of a waveform in the case of controlling by giving priority to rotation speed. The characteristic view which shows the example of a waveform in the case of controlling with priority on active power. The characteristic view which shows the relationship between a wind speed and electric power generation output.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Windmill, 2 ... Synchronous generator, 3 ... Forward converter, 4 ... DC capacitor, 5 ... Reverse converter, 6 ... Transformer for grid connection, 7 ... Voltage detection sensor, 8 ... Current detection sensor, 9 ... Active power detector, 10 ... Reactive power detector, 11 ... Rotational speed detector, 12 ... Rotational speed controller, 13 ... Active power controller, 14 ... Reactive power controller, 15 ... Current controller, 16 ... Pulse generation 17 ... 3-phase / 2-phase converter, 18 ... 2-phase / 3-phase converter, 19 ... active current controller, 20 ... reactive current controller, 21 ... wind speed detector, 22 ... rotational speed command calculator.

Claims (2)

A synchronous generator connected to the shaft of the wind turbine, a converter for converting the variable frequency generated power of the synchronous generator connected to a stator of the synchronous generator into DC power, the converter and the power system, In a wind turbine generator comprising an inverse converter that converts the DC power connected between two to a fixed frequency AC power and supplies the power to the power system,
Rotational speed detecting means for detecting the rotational speed of the windmill, rotational speed command calculating means for obtaining an efficient rotational speed based on a detection value from the wind speed detector for detecting the wind speed, and rotation from the rotational speed command calculator Rotational speed control means for obtaining an active power command from the speed command and the rotational speed of the rotational speed detector, the active power command from the rotational speed controller and the active power from the synchronous generator Power control means for controlling the output,
By controlling the control gain of the rotational speed control means according to the state of the wind speed, the rotational speed of the windmill is controlled with priority or the active power output by the synchronous generator is controlled with priority. Wind power generator characterized by.   The wind power generator according to claim 1, wherein the control gain of the rotation speed command calculating means is switched based on a predetermined wind speed.

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