JP2000287462A - Apparatus and method for controlling power converter - Google Patents

Abstract

(57) Abstract: Provided is a power conversion device and a method suitable for suppressing overcurrent of the power converter when starting or restarting the power converter. In a power converter control device, a feedforward voltage calculator for calculating a feedforward voltage command value based on an AC voltage, and a detected DC voltage and an AC voltage are calculated by a conventional method. A feedforward amplitude calculator 13a for calculating a coefficient K for adjusting the magnitude of the voltage component of the obtained feedforward voltage command value, and a feedforward voltage calculator 12a
Multipliers 14a, 14b, 14c for multiplying the output from
And

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power converter device, and more particularly, to a control device and a method for a power converter that cooperates with a power system and absorbs or discharges power.

[0002]

2. Description of the Related Art In a conventional converter control apparatus disclosed on page 6-298 of the 1998 IEEJ National Conference [6], the gain of a current control system is controlled when the DC link voltage fluctuates. Is multiplied by a compensation gain so as not to change, and the current control gain is controlled to be constant before and after the DC link voltage fluctuates.

[0003]

As described above, in the prior art, only the gain of the current control is fixed.
If the DC voltage changes significantly at start-up and restart after stop, current control does not work due to control delay,
Due to the fluctuation of the DC voltage, the magnitude of the voltage actually output by the converter changes according to the feedforward voltage command value, and as a result, a large difference occurs between the system voltage and the output voltage of the power converter, Excessive current will flow through the power converter.

[0004] It is an object of the present invention to provide a power converter and a method suitable for suppressing overcurrent of the power converter when starting or restarting the power converter.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention relates to a control apparatus and a control method for a power converter, wherein a DC voltage of the power converter is detected, and at least a voltage corresponding to the detected DC voltage is detected. A feedforward voltage command value having a voltage component to be used and used for controlling the power converter is set.

[0006] Further, in the control device or the control method according to the present invention, when setting the feedforward voltage command value, not only the detected DC voltage but also the AC voltage at a connection point is set. Alternatively, the magnitude of the feedforward voltage component may be set.

According to another aspect of the present invention, there is provided a control device and a control method for controlling a power converter, comprising: a feedforward voltage determined from an AC voltage at a connection point by a known method; An output voltage command value is added, and the magnitude of the voltage component as a result of the addition is adjusted so as to at least correspond to the DC voltage of the power converter.

According to another aspect of the present invention, there is provided a control device or a control method for controlling a power converter, comprising: detecting a DC voltage of the power converter; The magnitude of the feedforward voltage component determined by the conventional method is adjusted in accordance with the maximum phase voltage that can be output in step (1).

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

A first embodiment for realizing a power converter according to the present invention will be described with reference to FIGS.

As shown in FIG. 1, the power converter 1a of the present embodiment is connected to an interconnection transformer 3a, and the interconnection transformer 3a is connected to an electric power system. A rechargeable battery 4a is installed in the DC part of the power converter 1a, and the controller 18a
Thus, the active power P and the reactive power Q are supplied to the power system via the interconnection transformer 3a.

The control device 18a of the power converter 1a calculates the active power P and the reactive power Q output to the system by the power detector 6a from the output of the current detector 2b and the output of the voltage detector 5a.

The active power P and the reactive power Q obtained as described above are input to the active power adjuster 9a and the reactive power adjuster 8a, respectively. An active component current command value Id * and an active component current command value Iq * are calculated to match the value Qref and the active power command value Pref, and output to the current regulator 10a.

The phase detector 7a outputs phase signals Vcos and Vsin that follow the phase of the system voltage. The phase signals Vcos and Vsin are input to coordinate converters 16a and 17a. The converter current detection value Icnv is coordinate-converted by the coordinate converter 17a, and the effective component current detection value I, which is the two-axis current detection value that is the conversion result.
d, The reactive current detection value Iq is input to the current regulator 10a.

The current regulator 10a outputs an effective component voltage command value Vd * and an invalid component voltage command value Vq * in order to control the current of the power converter 1a to match the command values Id * and Iq *. . The outputs Vd * and Vq * of the current regulator 10a are input to a coordinate converter 16a, and the coordinate converter 16a outputs voltage command values Vuo *, Vvo *, Vwo
* Is output to the adders 15a, 15b, and 15c.

On the other hand, the detected interconnection point voltage Vac is input to the feedforward voltage calculator 12a. The feedforward voltage calculator 12a converts the input interconnection point voltage Vac into a voltage phase output from the power converter 1a and performs A / D conversion in the same manner as in the known method of calculating a feedforward voltage command value. Multiplied by a predetermined fixed gain to obtain the feedforward voltage command value Vuf
1, Vvf1 and Vwf1 are determined and output to multipliers 14a, 14b and 14c. Here, the fixed gain is set in advance in accordance with the condition of the device such as the winding ratio of the interconnection transformer.

The connection point voltage detection value Vac and the DC voltage detection value Vdc are input to the feedforward amplitude calculator 13a. The feedforward amplitude calculator 13a uses the interconnection point voltage detection value Vac and the DC voltage detection value Vdc to generate a power converter
A multiplication coefficient K for determining the magnitude of the feedforward voltage component 1a is calculated and output to the multipliers 14a, 14b, 14c.

In this embodiment, the feedforward voltage command values Vuf1, Vvf1, and Vwf1 calculated by the conventional method are set according to the interconnection point voltage detection value Vac and the DC voltage detection value Vdc. By multiplying by the coefficient K, the final magnitude of the feedforward voltage command value is determined. For this reason, even when the DC voltage or the system voltage fluctuates, the value of the coefficient K is adjusted according to the fluctuation state so as to prevent an overcurrent from flowing through the converter.

The multipliers 14a, 14b, 14c multiply the feedforward voltage command values Vuf1, Vvf1, Vwf1 by the coefficient K, and feed the feedforward voltage command values Vuf, Vvf, Vwf to the adders 15a, 15b, 15c. Output.

The adders 15a, 15b and 15c provide the voltage command value Vuo
*, Vvo *, Vwo * and the feedforward voltage command value Vu
f, Vvf, Vwf, which is the addition result of power converter voltage command value V
u *, Vv *, Vw * are output to the PWM calculator 11a.

The PWM calculator 11a outputs a gate pulse GP based on the voltage command values Vu *, Vv *, Vw * of the power converter to the power converter 1a.

FIG. 2 shows the detailed configuration of the feedforward amplitude calculator 13a.

In the feedforward amplitude calculator 13a,
The detected voltage value Vac at the interconnection point is converted to a three-phase to two-phase converter 25a.
To convert the data into an interconnection point voltage α component Va and an interconnection point voltage β component Vb, which are two-axis data. The two-axis data Va and Vb are input to the sum-of-squares arithmetic unit 26a, and output the system voltage amplitude value Vn at the interconnection point to the gain adjuster 27a.

The gain adjuster 27a multiplies the input voltage amplitude value Vn by the winding ratio of the interconnection transformer and converts the voltage amplitude value into a converter output end AC voltage amplitude instantaneous value Vi on the power converter side. The calculated voltage amplitude value Vi is input to the filter 19a, and the AC voltage amplitude value A at the converter output terminal, which is the output of the filter 19a, is output to the divider 24a.

The detected DC voltage Vdc is input to each of the filter 20a and the switch 22a, and the DC voltage filter output Vdc1 output from the filter 20a is input to the switch 22a. The control calculation start command is input to a delay circuit 21a that delays by a predetermined time, and the output of the delay circuit 21a is input to a switch 22a.

The switch 22a controls the DC voltage Vdc during the time from the start of the control calculation to when the operation signal is switched to the operation.
2a, and operates so as to output the DC voltage filter output Vdc1 from the filter 20a after the start of operation.

The output Vdcs from the switch 22a is halved by the multiplier 23a, so that the output Vdcs is converted into a fundamental wave amplitude maximum value B of the maximum phase voltage that can be output by the power converter 1a calculated from the DC voltage. You. The divider 24a divides the converter output terminal AC voltage amplitude value A from the filter 19a by the fundamental wave amplitude maximum value B, and outputs a coefficient K of a feedforward voltage component.

According to the present embodiment, the magnitude of the feedforward voltage command value for controlling the power converter is obtained from the system voltage and the DC voltage, so that the DC voltage or the system voltage fluctuates while the power converter is stopped. When the power converter is restarted in such a case, the magnitude of the AC voltage output from the power converter matches the system voltage, preventing excessive current from flowing through the converter, and Can be restarted.

Further, the feedforward amplitude calculator 13
By the switch 22a of a, during a predetermined period from the control calculation start command, since the instantaneous value of the DC voltage that does not pass through the filter is used for the calculation of the coefficient K of the feedforward voltage component, it is restarted without delaying the DC voltage fluctuation. Becomes possible.

Further, the feedforward amplitude calculator 13
By providing a filter for the DC voltage detection value of a and the system voltage amplitude value, the coefficient of the feedforward voltage component during operation
K can be suppressed from being affected by the ripple of the DC voltage caused by, for example, switching or disturbance.

Although the feedforward voltage command value of this embodiment is added by an AC signal, as shown in FIG. 9, the output of the feedforward voltage calculator 12a is coordinated by a newly provided coordinate converter 17g. Is converted, and the output after the coordinate conversion is multiplied by a coefficient K by multipliers 14s and 14t to obtain Vd in two-axis coordinates
Similar effects can be obtained by adding *, Vq * and adders 15s, 15t.

Next, a second embodiment of the present invention will be described with reference to FIGS. Note that the same reference numerals are given to the same components as those in the above embodiment throughout the drawings, and the detailed description will be omitted.

FIG. 3 shows the configuration of the control device 18b of the power converter 1a according to the present embodiment. Control device 18b of the present embodiment
In the embodiment of FIG. 1, the input to the feedforward amplitude calculator 13b is only the DC voltage detection value Vdc.

As shown in FIG. 4, the feedforward amplitude calculator 13b of this embodiment uses an interconnection point voltage setter 25 instead of calculating the converter output terminal AC voltage amplitude value A in the first embodiment. It is newly provided and the converter output voltage has a fixed value C. From the fixed value C and the output B based on the DC voltage detection value Vdc obtained by the same configuration as in the first embodiment, a coefficient K of the feedforward voltage component is obtained by the divider 24b. .

According to the present embodiment, when the system is installed in a place where the fluctuation of the system voltage Vac is small, or when the DC voltage Vd
When c is sufficiently larger than the system voltage Vac, that is, when the influence of the fluctuation of the system voltage is small, the same effect as that of the first embodiment can be obtained.

Furthermore, according to the present embodiment, since the operation block is simplified, the digital control has the effect of shortening the processing time.

Although the feedforward voltage command value of the present embodiment is added by an AC signal, the configuration for calculating the coefficient K on two-axis coordinates is similar to the example of FIG. 9 in the first embodiment. Is also good. That is, in the second embodiment, as shown in FIG. 10, the coordinates of the feedforward voltage component are converted by the coordinate converter 17g in two-axis coordinates as shown in FIG.
K is multiplied by multipliers 14s and 14t, and Vd *, Vq * and adder 15s,
Even if the addition is performed by 15t, the same effect as in the present embodiment can be obtained.

A third embodiment for realizing the power converter according to the present invention will be described with reference to FIGS.

The configuration of the control device 18c of this embodiment basically has the same configuration as that of the first embodiment.
The method of adding the feedforward voltage command value and the method of multiplying the coefficient K are different in the following points.

That is, in this embodiment, the feedforward voltage command values Vuf *, Vvf *, Vwf * output from the feedforward computing unit 12a and the two-axis voltage command values Vd *, output from the current regulator 10a, are used. The results Vuo *, Vvo *, and Vwo * of the result of the coordinate conversion of Vq * by the coordinate converter 16a are added to the adder 15 respectively.
g, 15h, and 15i, and add the voltage command values Vuof *, Vvof *, and Vwof1 * obtained as a result of the addition to the coefficient K of the feedforward voltage component obtained by the feedforward amplitude calculator 13a.
Is multiplied by the multipliers 14g, 14h, and 14i.

The feedforward amplitude calculator 13c has:
Any of the configurations shown in FIGS. 2 and 4 described in the above embodiment may be used.

According to the present embodiment, when the power converter 1a is started, the output of the current regulator becomes zero. For this reason, the feedforward voltage command value determines the output voltage of the power converter at the time of startup, and the same effect as in the first embodiment can be obtained.

Furthermore, according to the present embodiment, the response including the feedforward voltage control system and the current control system can be kept substantially constant even if the DC voltage or the interconnection point voltage fluctuates.

Although the feedforward voltage command value of this embodiment is added by an AC signal, as shown in FIG. 11, the coordinates are converted by a coordinate converter 17i and Vd *, Vq
The same effect as in the present embodiment can be obtained by a configuration in which * is added by the adders 15w and 15x and the coefficient K of the feedforward voltage component is multiplied by the multipliers 14w, 14x and 14y.

Next, a fourth embodiment of the present invention will be described with reference to FIGS.

The power storage converter 1a using the secondary battery 4a in the first embodiment is provided with a reactive power compensator (SV
FIG. 6 shows a configuration example when C) is applied.

In this embodiment, the power converter of the reactive power compensator is
A capacitor 29a is installed in the DC portion of 1d, and a DC voltage regulator 32a is provided in place of the reactive power regulator 9a in FIG.
The current command value Id * in the DC voltage regulator 32a so that the DC voltage Vdc matches the input DC voltage command value Vdcref.
Is calculated, the reactive power compensating device becomes the control device 18
The reactive power Q is exchanged with the system according to the command from d.

According to the present embodiment, it is possible to prevent the SVC from being stopped due to an overcurrent, and to stably supply the reactive power.

Also, as shown in FIGS. 12 and 13, even when the second and third embodiments are applied to an SVC, the same effects as in the present embodiment can be obtained.

The present invention is also applicable to a superconducting power storage device as shown in FIG. 7 in addition to the reactive power compensator (SVC) of the present embodiment. A superconducting coil 30 is provided in a DC portion of the power converter 1e of the superconducting power storage device, and absorbs or discharges power from a system according to a command from a control device.

The present invention also provides a reactive power compensator (SV
Instead of C), it may be used for a power converter of a variable speed system. The variable speed power generation system includes a pumped storage power generation system and a flywheel power generation system.

FIG. 8 shows an example in which the present embodiment is applied to a variable speed power generation system. In this example, the capacitor 29b is charged by the power converter 1f, and the power converter 1g is charged by the capacitor 2b.
9b is used for secondary excitation of the generator motor 28. The rotating shaft of the generator motor 28 is connected to the water wheel or the flywheel 31, and the primary side of the generator motor 28 is connected to the power system via the transformer 3a. This variable speed power generation system absorbs or discharges electric power from the system according to a command from a control device 18f to which the present invention is applied.

According to the control device 18f of this embodiment, the same effect as that of the configuration example of FIG. 6 can be obtained, but the power converter 1f,
It is possible to prevent the generator motor from stopping due to an overcurrent of 1 g or the like.

Here, the case where the present invention is mainly applied to the control device and method in the first embodiment has been described.
A configuration using the control device and the method described in other embodiments may be adopted.

[0055]

According to the present invention, the magnitude of the feedforward voltage command value for controlling the power converter is obtained from the system voltage and the DC voltage. Even when the power converter is restarted when the power is fluctuating, an excessive current is prevented from flowing through the power converter, and the device can be restarted.

Further, according to the present invention, the instantaneous value of the DC voltage is used for the magnitude of the feedforward voltage command value for a predetermined period from the control calculation start command by the switch of the feedforward amplitude calculator, so Restart is possible without delay.

Further, according to the present invention, the influence of the DC voltage ripple during operation can be suppressed by providing a filter for the DC voltage detection of the feedforward amplitude calculator and the system voltage amplitude value.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a control device of a power converter according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration example of a feedforward amplitude calculator in the embodiment of FIG.

FIG. 3 is a block diagram illustrating a configuration of a control device of a power converter according to another embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration example of a feedforward amplitude calculator in the embodiment of FIG. 3;

FIG. 5 is a block diagram showing a configuration of a control device according to another embodiment of the present invention.

FIG. 6 is a block diagram showing a configuration of a control device according to another embodiment of the present invention.

FIG. 7 is a block diagram showing a configuration of a control device according to another embodiment of the present invention.

FIG. 8 is a block diagram showing a configuration of a control device according to another embodiment of the present invention.

FIG. 9 is a block diagram showing a configuration of a control device according to another embodiment of the present invention.

FIG. 10 is a block diagram showing a configuration of a control device according to another embodiment of the present invention.

FIG. 11 is a block diagram showing a configuration of a control device according to another embodiment of the present invention.

FIG. 12 is a block diagram showing a configuration of a control device according to another embodiment of the present invention.

FIG. 13 is a block diagram showing a configuration of a control device according to another embodiment of the present invention.

[Explanation of symbols]

1a, 1d, 1g, 1e, 1f --- Power converter 2a, 2b --- Current detector 3a --- Interconnecting transformer 4a --- Secondary battery 5a --- Voltage detector 6a --- Power detector 7a --- Phase detector 8a --- Reactive power regulator 9a --- Active power regulator 10a --- Current regulator 11a --- PWM operator 12a --- Feed forward voltage operator 13a , 13b, 13c --- Feedforward amplitude calculators 14a, 14b, 14c, 14g, 14h, 14i, 14s, 14t --- Multipliers 15a, 15b, 15c, 15g, 15h, 15i, 15s, 15t --- Adder 16a --- Coordinate converter 17a, 17g --- Coordinate converter 18a-18k --- Power converter controller 19a, 20a --- Filter 21a --- Delay circuit 22a --- Switch 23a- --Multipliers 24a, 24b --- Divider 25a --- Three-phase two-phase converter 26a --- Sum-of-squares route calculator 27a --- Multiplier 28 --- Generator motors 29a, 29b --- Capacitor 30 --- Superconducting coil 31 --- Flywheel 32a, 32b --- DC voltage regulator Iac --- Connection point current detection value Vac --- Connection point voltage detection value Icnv --- Converter current Detection value Pref --- Yes Active power command value Qref --- Reactive power command value P --- Active power Q --- Reactive power Id * --- Active component current command value Iq * --- Reactive component current command value Id --- Active component Current detection value Iq --- Inactive component current detection value Vcos, Vsin --- Phase signal Vd * --- Effective component voltage command value Vq * --- Inactive component voltage command value Vuo *, Vvo *, Vwo *- -Voltage command value Vuf1, Vvf1, Vwf1, Vuf, Vvf, Vwf, Vuf *, Vvf *, Vwf *, Vdf, Vqf-
-Feedforward voltage command value Vu *, Vv *, Vw * --- Converter output voltage command value GP --- Gate pulse Va --- Interconnection point voltage α component Vb --- Interconnection point voltage β component Vn --- System voltage amplitude value Vi --- Converter output terminal AC voltage instantaneous value A --- Converter output terminal AC voltage amplitude value Vdc1 --- DC voltage filter output Vdcs --- Switcher output B- --Maximum fundamental wave amplitude K --- Coefficient of feedforward voltage component.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H02M 7/48 H02M 7/48 R (72) Inventor Kazuhiro Imaya 3-chome, Kochicho, Hitachi City, Ibaraki Prefecture 1 Hitachi, Ltd. Hitachi Plant (72) Inventor Motoo Futami 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture F-term in Hitachi Research Laboratory, Hitachi Ltd. F-term (reference) DA02 DA04 DB02 DB05 DC02 DC03 DC04 DC05 GA02 5H007 AA02 AA05 AA06 CC23 CC32 DA05 DA06 DB02 DB05 DB07 DC02 DC03 DC04 DC05 EA02 FA03 GA03 GA05

Claims (14)

[Claims] 1. A control device for a power converter for converting an AC voltage to a DC voltage or a DC voltage to an AC voltage, comprising: DC voltage detecting means for detecting the DC voltage of the power converter; And a feedforward voltage setting means for setting a feedforward voltage command value for use in controlling the power converter, the control device having a voltage component corresponding to at least the power converter. 2. The control device according to claim 1, further comprising an AC voltage detecting means for detecting an AC voltage at an interconnection point, wherein said feedforward voltage setting means is configured to detect said AC voltage and said detected AC voltage. A control device for a power converter, wherein a magnitude of the feedforward voltage component is set in accordance with a DC voltage. 3. A control device for controlling a power converter for converting an AC voltage into a DC voltage or converting a DC voltage into an AC voltage, wherein an AC voltage at an interconnection point is detected, and the detected AC voltage is A feedforward voltage determining means for determining a feedforward voltage used for controlling the power converter; a control for detecting the current of the power converter, accepting the detected current and a command value relating to the current, and matching the two. Current adjusting means for outputting a voltage command value used for: an adding means for adding the determined feedforward voltage and the voltage command value; and detecting a DC voltage of the power converter, and applying the detected DC voltage to the detected DC voltage. At least correspondingly, voltage command value adjusting means for adjusting the magnitude of the addition result of the feedforward voltage and the voltage command value. Power converter control device. 4. The control device according to claim 1, wherein the feedforward voltage setting means detects an AC voltage at the interconnection point and obtains a feedforward voltage command value according to the detected AC voltage. Value determining means, fundamental wave amplitude calculating means for calculating a fundamental wave amplitude of a maximum phase voltage that can be output from the power converter from the detected DC voltage, and a predetermined voltage amplitude at an AC output terminal of the power converter. Multiplying coefficient calculating means for calculating a multiplication coefficient for determining the magnitude of the feedforward voltage component by dividing the set value by the fundamental wave amplitude; and a voltage component of the calculated feedforward voltage command value. Adjusting means for adjusting the magnitude of the voltage component of the feedforward voltage command value to be output by multiplying the calculated multiplication coefficient. Converter control apparatus according to claim. 5. The control device according to claim 2, wherein the feedforward voltage setting means detects an AC voltage at the interconnection point, and obtains a feedforward voltage command value in accordance with the detected AC voltage. Value determination means, AC voltage amplitude means for calculating the amplitude of the AC voltage at the detected interconnection point, and amplitude conversion means for converting the calculated AC voltage amplitude to the AC voltage amplitude at the output end of the power converter, Fundamental wave amplitude calculating means for calculating a fundamental wave amplitude of a maximum phase voltage that can be output from the power converter from the detected DC voltage; and an AC output terminal of the power converter calculated from the detected connection point AC voltage. Is divided by the fundamental wave amplitude calculated from the detected DC voltage to calculate a multiplication coefficient for determining the magnitude of the feedforward voltage component. Arithmetic coefficient calculating means, and adjusting the magnitude of the voltage component of the feedforward voltage command value to be output by multiplying the voltage component of the calculated feedforward voltage command value by the calculated multiplication coefficient. And a control unit for the power converter. 6. The control device according to claim 5, further comprising a first filter for filtering a voltage amplitude at an output terminal of the power converter calculated from the AC voltage at the interconnection point, wherein the multiplication coefficient calculation means includes: The control device for a power converter, wherein the multiplication coefficient is calculated using the filtered voltage amplitude value. 7. The control device according to claim 4, further comprising a second filter for filtering a fundamental wave amplitude of a maximum phase voltage that can be output from the power converter and calculated from the DC voltage, The control device for a power converter, wherein the multiplication coefficient calculation means calculates the multiplication coefficient using the filtered fundamental wave amplitude value. 8. The control device according to claim 7, wherein the fundamental wave amplitude value output from the fundamental wave amplitude calculation means and the filtered fundamental wave amplitude value output from the second filter are included. A control device for a power converter, further comprising: a selection unit that selects one of them and outputs the selected value to the multiplication coefficient calculation unit. 9. The control device for a power converter according to claim 8, wherein a selection operation of said selection means is switched by an operation start command of said control device. 10. An AC voltage detecting means for detecting an AC voltage at an interconnection point, and a feedforward voltage determining means for determining a feedforward voltage from the detected AC voltage. make use of,
In a control device that controls an AC converter that converts an AC voltage to a DC voltage or converts a DC voltage to an AC voltage, a DC voltage detection unit that detects a DC voltage of the power converter, and is determined by the detected DC voltage. Feed-forward voltage adjusting means for adjusting the magnitude of the determined feed-forward voltage component in accordance with the maximum phase voltage that the power converter can output at that time. Control device. 11. A power storage system comprising: the control device according to claim 1; and a power converter controlled by the control device. 12. A reactive power compensator comprising: the control device according to claim 1; and a power converter controlled by the control device. 13. A variable speed power generation system comprising: the control device according to claim 1; and a converter for secondary excitation controlled by the control device. 14. A control method of a power converter for converting an AC voltage into a DC voltage or converting a DC voltage into an AC voltage, wherein the DC voltage of the power converter is detected, and a voltage corresponding to at least the detected DC voltage is detected. A method for controlling a power converter, comprising setting a feedforward voltage command value having a component for use in controlling the power converter.