JP2014236534A - Power converter for wind power generation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To continue operation while supplying power even during system voltage drop, in a power converter for wind power generation.SOLUTION: In a power converter for wind power generation including a synchronous generator 2 generating power with a driving force contributive to power generation, a power conversion unit 1 performing A/D conversion and D/A conversion of the output from the synchronous generator, and a system 3 supplied with power from the power conversion unit 1, the synchronous generator 2 is made to perform powering when the DC voltage detection value Vdc of the power conversion unit 1 exceeds a DC voltage command value Vdc. Consequently, increase in the DC voltage Vdc due to regenerative energy can be suppressed, and the DC section 4 of the power conversion unit 1 goes above an overvoltage failure level, thus preventing the power conversion unit 1 from stopping.

Description

  The present invention relates to a control method for continuing a driving operation without stopping a failure when a system voltage is reduced due to a system fault or the like in a wind power generation power converter using a synchronous generator.

  FIG. 6 shows the main circuit of the wind power generation power converter, and the power generated by the synchronous generator 2 is AC / DC / DC converted and orthogonal converted by the power converter 1 and supplied to the grid 3.

FIG. 7 shows a control circuit of the power converter for wind power generation. In the control circuit of the wind power generation power converter, as shown in FIG. 7, the DC voltage control unit 6 performs PI calculation on the DC voltage command value Vdc ^* and the DC voltage detection value Vdc, and the limiter 7 calculates the calculation result. The current command value I ^* is calculated.

The current command value I ^* and the current detection value I are input to the current controller 8 and PI calculation is performed to calculate the voltage command value V ^* . The inverter 1c of the power converter 1 is driven by this voltage command value V ^* to supply power to the system 3. Further, a current detector 10 is provided between the inverter 1 c and the system 3, and a current detection value I detected by the current detector 10 is output to the current controller 8.

  When 100% power is generated by the synchronous generator 2, if the system voltage decreases due to an accident such as the system 3, the power conversion unit 1 has a current limit. The power that can be transmitted is reduced.

  At this time, the power conversion unit 1 can transmit power to the system 3 up to the maximum output current of the power conversion unit 1, but when the active power that can be transmitted to the system 3 is smaller than the active power generated by the synchronous generator 2, The difference between the active power generated by the synchronous motor 2 and the active power that can be transmitted to the grid 3 is accumulated in the DC unit 4.

  Therefore, in the case as described above, the control circuit of the wind power generation power converter as shown in FIG. 6 does not allow constant DC voltage control, and the voltage of the DC unit 4 increases. As shown in FIG. 8, when the system voltage decreases for a long time, the voltage of the DC unit 4 continues to increase and exceeds the overvoltage failure level, and the power conversion unit 1 stops.

JP 2012-125144 A JP 2012-231624 A JP 2004-194417 A

  The stoppage of the power conversion unit 1 due to an overvoltage failure of the DC unit 4 due to a drop in the system voltage often cannot be recovered immediately, which hinders stable power supply. When a large number of power conversion units 1 are connected to the grid 3 in the use of the power conversion device for wind power generation, if power supply to the grid 3 is stopped at the same time, other devices try to compensate for the energy cut off, and the grid power supply There is a risk of becoming unstable or, in the worst case, a power outage.

  As described above, in the power generation apparatus for wind power generation, it is a problem to continue the operation while supplying power even when the system voltage is lowered.

  The present invention has been devised in view of the above-described conventional problems. One aspect of the present invention is a synchronous generator that generates electric power using a driving force that contributes to power generation, and an AC / DC and orthogonal conversion of the output of the synchronous generator. In a wind power generation power conversion device comprising a power conversion unit that performs power and a system to which power is supplied from the power conversion unit, a synchronous generator when a DC voltage detection value of the power conversion unit exceeds a DC voltage command value The power running operation is performed.

  Further, as one aspect thereof, when the rotational speed of the windmill is larger than a pre-overspeed preset to a value lower than the overspeed, the rotational speed of the windmill that is performing a power running operation is suppressed. To do.

  According to the present invention, in a power generation apparatus for wind power generation, it is possible to continue operation while supplying power even when the system voltage is lowered.

FIG. 2 is a block diagram illustrating a control circuit of the wind power generation power changing device according to the first embodiment. 4 is a time chart showing each waveform when the system voltage is lowered in the wind power generation power changing device according to the first embodiment. It is a characteristic view which shows the relationship between the rotation speed of a windmill, torque, and output electric power. It is a block diagram which shows the control circuit of the electric power change apparatus for wind power generation in Embodiment 2. 6 is a time chart showing each waveform when the system voltage is lowered in the wind power generation power changing device according to the second embodiment. It is the schematic which shows the main circuit of the electric power change apparatus for wind power generation. It is a block diagram which shows the control circuit of the conventional electric power change apparatus for wind power generation. It is a time chart which shows each waveform when the system voltage falls in the conventional power generation device for wind power generation.

  Hereinafter, Embodiments 1 and 2 in the power converter for wind power generation concerning this invention are explained in full detail based on FIGS.

[Embodiment 1]
The main circuit of the wind power generation power changing apparatus according to the first embodiment is configured in the same manner as in FIG. As shown in FIG. 6, the power converter 1 is connected to the synchronous generator 2. The synchronous motor 2 generates electric power with a driving force that contributes to power generation. The power conversion unit 1 includes a converter 1a that converts an AC voltage output from the synchronous generator 2 into a DC voltage, a capacitor 1b that charges energy converted into DC by the converter 1a, and energy that is charged in the capacitor 1b. And an inverter 1c for converting the AC voltage. The AC voltage output from the inverter 1 c is supplied to the system 3 through the transformer 5.

As shown in FIG. 1, the control circuit subtracts a corrected torque command value Tc1 ^*, which will be described later, from the torque command value T ^* . Here, the torque command value T ^* is a torque command value for power generation, and the corrected torque command value Tc1 ^* is a torque command value for increasing the rotational speed of the windmill.

This subtraction result is subjected to limiter processing by the limiter 11 and output to the current command calculation unit 12. The current command calculation unit 12 calculates a current command value I ^* based on the output value of the limiter 11 and outputs it to the current control unit 8. The current control unit 8 performs PI calculation of the current command value I ^* and the current detection value I, and outputs the calculation result as a voltage command value V ^* .

The inverter 1c is driven by the voltage command value V ^* to supply power to the system 3. Further, the current detector 10 is inserted between the power converter 1 c and the system 3, and the current detection value I detected by the current detector 10 is output to the current controller 8.

The DC voltage suppression unit 13 calculates a correction torque command Tc1 ^* for increasing the wind turbine speed. First, the DC voltage command value Vdc ^* and the DC voltage detection value Vdc detected from the DC unit 4 are inputted to the DC voltage control unit 14 to perform PI calculation, and the calculation result is subjected to limiter processing by the limiter 15 to obtain a corrected torque command value. Calculate Tc1 ^* .

  When the system voltage decreases, the amount of power that can be transmitted to the system 3 decreases, so that energy from the synchronous generator 2 is accumulated as surplus power in the DC unit 4.

At this time, by giving a correction torque command value Tc1 ^* for accelerating the synchronous generator 2, the synchronous generator 2 is set in a mode for operating as an electric motor, and the rotational speed of the windmill is increased. As a result, the energy accumulated in the DC unit 4 is consumed by increasing the inertial energy of the windmill, and the voltage of the DC unit 4 is lowered. Thereafter, the DC voltage is stabilized and power is supplied to the system 3.

FIG. 2 is a time chart showing each waveform when the system voltage is lowered, and FIG. 3 is a characteristic diagram showing the relationship between the rotational speed of the windmill, torque and output power. WT1 to WT4 shown in FIG. 3 are wind speed parameters. Although not shown, the torque command value T ^* for the system voltage with the wind speed as a parameter is output from the host controller.

For example, it is assumed that the windmill in FIG. 3 is operating at the wind speed WT2 and at the torque A1 and the output power B1. Until time t1, the corrected torque command value Tc1 ^* is 0, and the torque command value input to the current command calculation unit 12 is only the torque command value T ^* for power generation. Until this time t1, the DC voltage command value Vdc ^* ≈the DC voltage detection value Vdc. At time t1, the output voltage B1 cannot be supplied to the grid 3 due to the drop in the grid voltage, and the DC voltage Vdc starts to rise.

After time t1, the DC voltage detection value Vdc becomes equal to or greater than the DC voltage command value Vdc ^* , and the DC voltage control unit 14 performs proportional control and integral control from the difference between the DC voltage detection value Vdc and the DC voltage command value Vdc ^*. A correction torque command value Tc1 ^* for accelerating the wind turbine is generated. By subtracting the correction torque command value Tc1 ^* from the torque command value T ^*, the current command torque is output to the arithmetic unit 12 the command value T ^* -Tc1 ^*, the time becomes a torque command to accelerate the rotational speed of the windmill t2 Then the windmill starts to speed up. Here, there is a control delay from time t1 to time t2. Since the torque command value T ^* depends on the wind speed and the system voltage, it changes around time t1.

At times t2 to t3, the energy accumulated in the DC unit 4 is released by operating the synchronous generator 2 as an electric motor, and the DC voltage is suppressed. When the DC voltage detection value Vdc becomes equal to or less than the DC voltage command value Vdc ^{* at} time t3, the corrected torque command value Tc1 ^* becomes zero, and the torque and output power are the operating points of A2 and B2, as shown in FIG. Become. Thereafter, after the system voltage is restored at time t4, the state before time t1 is restored.

  As described above, according to the power generator for wind power generation in the first embodiment, the DC voltage control is incorporated in the control of the synchronous generator 2 to reduce the torque command value and make the torque command value a power running region. Therefore, it is possible to suppress an increase in the DC voltage Vdc due to regenerative energy, and it is possible to suppress the DC unit 4 from reaching the overvoltage failure level and stopping the power conversion unit 1. As a result, the operation continuation time when the system voltage drops can be extended.

[Embodiment 2]
In the first embodiment, the rotational speed of the wind turbine is accelerated by the function of the DC voltage suppression unit 13, and the DC voltage Vdc of the DC unit 4 is returned to the vicinity of the DC voltage command value Vdc ^* at time t3, but the torque command value T ^* is not correct. If appropriate, the rotational speed of the windmill may be overspeeded. In the second embodiment, countermeasures against overspeed in the rotational speed of the windmill are taken.

  FIG. 4 is a block diagram illustrating a control device for the wind power generation power changing device according to the second embodiment. The control circuit of the power converter for wind power generation according to the second embodiment is obtained by adding a speed suppression unit 16 to the control device for the power converter according to the first embodiment.

As shown in FIG. 4, in the speed suppression unit 16, the speed control unit 17 inputs the pre-overspeed ω and the speed estimation value ω to perform PI calculation, and the limiter 18 performs a limiter process on the calculation result, thereby overspeed suppression torque. The command value Tc2 ^* is calculated.

The overspeed suppression torque command value Tc2 ^* is subtracted from the correction torque command Tc1 ^* , which is the output of the limiter 15 in the DC voltage suppression unit 13, and the value to be subtracted from the torque command value T ^* is Tc1 ^* −Tc2 ^* . . Since the subsequent steps are the same as those in the first embodiment, description thereof is omitted.

An overspeed suppression torque command value Tc2 is obtained by performing speed control using proportional control and integral control from the difference between the estimated speed value ω and the speed before the overspeed, and a pre-overspeed ω ^* of a preset value. ^* Is generated, and the correction torque command value that increases the wind turbine speed is adjusted so that an overspeed failure does not occur.

Therefore, as shown in FIG. 5, even if the system voltage drop period extends to time t <b> 5 from FIG. 3, the estimated rotational speed ω of the windmill rises and exceeds the pre-overspeed ω ^* . The overspeed suppression torque command value Tc2 ^* is subtracted from the corrected torque command value Tc1 ^* . As a result, the torque command can be suppressed so that the generator does not become overspeed.

  Moreover, even if the DC voltage Vdc rises and the system voltage drop period extends, the period in which the power converter can be continuously operated without stopping the failure can be extended.

DESCRIPTION OF SYMBOLS 1 ... Electric power conversion part 2 ... Synchronous motor 3 ... System | strain Vdc ... DC voltage detection value Vdc ^* ... DC voltage command value omega ... Rotating speed of a windmill ω ^* ... Pre overspeed

Claims (2)

A synchronous generator that generates electric power with a driving force that contributes to power generation;
A power converter for AC / DC and orthogonal conversion of the output of the synchronous generator;
In a power conversion device for wind power generation comprising a system to which power is supplied from a power conversion unit,
A power converter for wind power generation, characterized in that when the detected DC voltage value of the power converter exceeds the DC voltage command value, the synchronous generator is powered.   A power converter for wind power generation, characterized in that, when the rotational speed of the windmill becomes larger than a pre-overspeed preset to a value lower than the overspeed, the rotational speed of the windmill operating in power running is suppressed. .

Images