3. The power conversion device according to claim 2, wherein the current command value correction unit corrects the current command value so that the current command value becomes closer to the current detection value. 25 38

4. The power conversion device according to claim 2, wherein the current command value correction unit corrects the current command value so that a correction amount increases in accordance with the magnitude of the 5 current difference.

5. The power conversion device according to claim 2, wherein the current command value correction unit corrects the current command value so that a correction 10 amount increases in accordance with the magnitude of the voltage difference.

6. The power conversion device according to claim 2, wherein further the current command value correction 15 unit does not correct the current command value when the polarity of the voltage difference and the polarity of the current difference are the same.

7. The power conversion device according to claim 2, 20 wherein the current command value correction unit corrects the current command value so that the current command value becomes closer to the current detection value when the polarity of the voltage difference and the polarity of the current difference are different from each 25 other in the case where a direction of a voltage to be 39 controlled and a direction of a current to be controlled are defined in such a way that, if the current is increased, the voltage increases. 5 8. The power conversion device according to claim 7, wherein the voltage to be controlled is a voltage on an output side of the main circuit unit.

9. The power conversion device according to claim 8, 10 wherein the current to be controlled is a current at the output side of the main circuit unit.

10. The power conversion device according to claim 9, wherein the main circuit unit has a series-connected 15 circuit composed of a capacitor and a reactor on the output side, the voltage to be controlled is a voltage of the capacitor, and the current to be controlled is a current of the 20 reactor.

11. The power conversion device according to claim 10, wherein the main circuit unit is a DC/DC converter including a switching leg. 25 40

12. The power conversion device according to claim 10, wherein the main circuit unit is an inverter including a three-phase bridge circuit. 5 13. The power conversion device according to claim 8, wherein the current to be controlled is a current at an input side of the main circuit unit.

14. The power conversion device according to claim 13, 10 wherein the main circuit unit is an AC/DC converter including a three-phase bridge circuit.

15. The power conversion device according to claim 8, wherein the current to be controlled is a current 15 between the input side and the output side of the main circuit unit.

16. The power conversion device according to claim 15, wherein the main circuit unit is an insulated DC/DC 20 converter, and the electric current to be controlled is a winding current of a transformer included in the insulated DC/DC converter. 25 17. A power conversion device comprising: 41 a plurality of main circuit units that are connected in multi-parallel, and each of which has switching elements; a voltage control unit for generating a current 5 command value on the basis of a voltage difference between a voltage command value and a voltage detection value; and a plurality of current control units each of which controls the switching elements on the basis of a current difference between the current command value and the 10 current detection value of the main circuit unit, and a current command value correction unit for correcting the current command value on the basis of an average value of the current differences of the plurality of main circuit units.

0001]The present invention relates to a power conversion device having a function of controlling a current and a voltage. Background Art
10 [0002]
Along with the worldwide increasing awareness about global environmental conservation, systems including power supplies such as storage batteries and solar batteries are developed. In recent years, the modularizations of power
15 conversion devices which have high power capacity
expandability and are expected to lead to cost reduction owing to mass production are desired in these systems. [0003]
In order to prevent cross current flowing among the
20 power conversion devices connected in parallel and to
balance the currents of the respective power conversion devices, it is necessary to improve the load transient responses of the respective power conversion devices. As control means for improving the load transient responses,
25 there is current mode voltage control in which a current

3
control function is provided to each power conversion
device and a voltage supplied to the load of each power
conversion device is controlled by controlling a current.
However, in the current mode voltage control, if the 5 fluctuation of the current of the load becomes large, there
is a case where the fluctuation of the voltage supplied to
the load becomes large.
[0004]
As a countermeasure against this problem, an existing 10 technology disclosed in Patent Literature 1 is known.
[0005]
In the existing technology disclosed in Patent
Literature 1, the current mode voltage control is adopted,
and whether or not high response control using current 15 feedback control is executed is decided on the basis of
whether or not a detection voltage corresponding to a
voltage command is within a target range. And if the
detection voltage is not within the target range, the high
response control is executed. 20 Citation List
Patent Literature
[0006]
Patent Literature 1: Japanese Patent Application
Laid-Open No. 2011-125144 25 Summary of Invention

4
Technical Problem [0007]
In the current mode voltage control, a voltage control unit obtains a current command value so that an 5 output voltage may coincide with a voltage command value,
and a current control unit obtains the ON time/OFF time of each switching element so that a current inside a power conversion device may coincide with the current command value. In such current mode voltage control, in order to
10 assure control stability, the response of the voltage
control unit is set slower than the response of the current control unit. Therefore, when the current of the load abruptly changes, the current control unit restricts the current of the power conversion device to the current
15 command value until the current command value is changed by the voltage control, so that there may be some cases where the fluctuation of the output voltage supplied to the load becomes large. [0008]
20 Even in the abovementioned prior art, since the
current mode voltage control is adopted, there are some cases where, because the current control unit restricts the current of the power conversion device to the current command value, the fluctuation of the output voltage cannot
25 be sufficiently reduced when the load current abruptly

5
changes. [0009]
Accordingly, an object of the present invention is to provide a power conversion device in which a change in the 5 output voltage is small even if the load current abruptly changes.
Solution to Problem [0010]
The power conversion device according to the present
10 invention includes: a main circuit unit having switching
elements; a voltage control unit for generating a current command value on the basis of a voltage difference between a voltage command value and a voltage detection value; and a current control unit for controlling the switching
15 elements on the basis of a current difference between the current command value and a current detection value. The power conversion device includes a current command value correction unit for correcting the current command value on the basis of the voltage difference and the current
20 difference.
Advantageous Effects of Invention [0011]
According to the present invention, it is possible to suppress the change of the voltage to be controlled at the
25 time of the load current abruptly changing.

6
[0012]
Problems, features, and advantageous effects other than the above will be explicitly shown by the descriptions of the following embodiments. 5 Brief Description of Drawings [0013]
Figure 1 is the configuration diagram of a power conversion device according to Example 1.
Figure 2 is a control function block diagram showing 10 a configuration example of a control unit in Figure 1.
Figure 3 shows an example of a relationship between a voltage difference, a current difference, and a correction amount Y.
Figure 4 shows another example of a relationship 15 between the voltage difference, the current difference and the correction amount Y.
Figure 5 is the configuration diagram of a power conversion device according to Example 2.
Figure 6 is the configuration diagram of a power 20 conversion device according to Example 3.
Figure 7 is the configuration diagram of a power conversion device according to Example 4.
Figure 8 is the configuration diagram of a power conversion device according to Example 5. 25 Description of Embodiments

7
[0014]
Embodiments of the present invention will be described with reference to the accompanying drawings using the following Examples 1 to 5. In the drawings, components 5 having the same reference numerals denote that these components have the same features or features having similar functions. [0015]
10 Figure 1 is the configuration diagram of a power
conversion device according to Example 1 of the present invention. The power conversion device of the present Example 1 operates as a DC/DC converter device. [0016]
15 In the power conversion device 50, input terminals J1
and J2 are connected to a DC power supply 1, and output terminals J3 and J4 are connected to a DC load 2, and the DC power supply 1 supplies power to the DC load 2. [0017]
20 The main circuit unit of the power conversion device
50 includes a switching leg 60 having a switching element Q1 and a switching element Q2 connected in series. As the switching elements Q 1, Q2, semiconductor switching elements are adopted. In addition, in the present Example
25 1, MOSFETs (Metal Oxide Semiconductor Field Effect

8
Transistors) are used as the switching elements Q1, Q2 (the
same applies to Examples 2 to 5 described later).
[0018]
In the power conversion device 50, a capacitor C1 is 5 connected in parallel between both ends of the switching
leg 60. A series-connected circuit composed of an inductor L and a capacitor C2 is connected in parallel between both ends of the switching element Q2. One end and the other end of the capacitor C1 are electrically connected to the
10 input terminals J1 and J2 respectively, and one end and the other end of the capacitor C2 are electrically connected to the output terminals J3 and J4 respectively. [0019]
The power conversion device 50 further includes a
15 voltage sensor 21 that detects the voltage of the capacitor C2, a current sensor 22 that detects the current of the inductor L, and a control unit 40 that controls the switching operations of the switching elements Q1, Q2. [0020]
20 The control unit 40 includes: a current command value
correction unit 10 (Iref correction); a voltage control unit 11 (AVR); a current control unit 12 (ACR); and a PWM signal generation unit 13 (PWM generation). First, the control unit 40 subtracts an output voltage detection value
25 Vout detected by the voltage sensor 21 from a voltage

9
command value Vref that is the target value of the output voltage of the power conversion device 50 to calculate a voltage difference Verr. This voltage difference Verr is inputted into the voltage control unit 11. 5 [0021]
In accordance with the inputted voltage difference Verr, the voltage control unit 11 calculates a current command value Iref so that the voltage difference Verr may be set to zero. Here, in the present Example 1, the
10 current command value Iref is a command value of a current to be flowed through the inductor L. [0022]
The control unit 40 subtracts the current detection value Iout of the inductor L detected by the current sensor
15 22 from the current command value Iref calculated by the voltage control unit 11, and calculates a current difference Ierr. This current difference Ierr is inputted into the current control unit 12. [0023]
20 The current control unit 12 calculates the ON-time
ratio (duty) of the switching elements Q1, Q2 in accordance with the inputted current difference Ierr so that the current difference Ierr may be set to zero. This ON-time ratio (duty) is inputted into the PWM signal generation
25 unit 13.

10
[0024]
The PWM signal generation unit 13 generates a PWM (Pulse Width Modulation) signal that is a gate signal for the switching elements Q1, Q2 on the basis of the ON-time 5 ratio (duty) calculated by the current control unit 12, and the generated PWM signal is applied to the control terminals of the switching elements Q1, Q2 (the gates of the MOSFETs in the present Example 1). The switching elements Q1, Q2 are controlled so as to be ON or OFF by the
10 PWM signal supplied to the control terminals. With this, the power conversion device 50 converts DC power received from the DC power source 1 into DC power having a voltage different from the inputted voltage, and outputs the converted DC power to a DC load 2.
15 [0025]
As described above, in the control unit 40, the voltage control unit 11 operates the voltage command value Iref to restrict the output voltage detection value Vout to the voltage command value Vref, and the current control
20 unit 12 operates the ON-time ratio (duty) of the switching elements Q1, Q2 to restrict the current detection value Iout of the inductor L to the current command value Iref. In other words, in the control unit 40, current mode voltage control is adopted as control means.
25 [0026]

11
Note that, in the current mode voltage control, the response speed of a voltage control system is typically set slower than the response speed of a current control system in order to assure control stability. Therefore, in the 5 current mode voltage control, even if the input voltage abruptly changes, it is easy to keep the output voltage equal to the target value, but if the load current abruptly changes, there are some cases where the output voltage largely departs from the target value.
10 [0027]
For example, in the power conversion device 50, when the consumption current Iload of the DC load 2 abruptly increases, the charge of the capacitor C2 is discharged first, and the voltage Vout of the capacitor C2, which is
15 the output voltage, decreases. When the voltage of the
capacitor C2 decreases, the current Iout of the inductor L passively increases. At this time, since the voltage difference Verr (=Vref-Vout) becomes positive, the voltage control unit 11 increases the current command value Iref.
20 However, because the response speed of the voltage control system is set relatively slow as described above, the increase speed of the current command value Iref outputted from the voltage control unit 11 is slower than the increase speed of the actual inductor current Iout, so that
25 the current command value Iref becomes smaller than the

12
actual inductor current Iout. In such a state, the current control unit 12 controls the switching elements Q1, Q2 so that the inductor current Iout may coincide with the current command value Iref, but since the current 5 difference Ierr (=Iref-Iout) is negative, the increase of the inductor current Iout is delayed. Therefore, the decrease of the voltage of the capacitor C2, that is, the decrease of the output voltage Vout, sometimes becomes large.
10 [0028]
In order to alleviate such a phenomenon and to reduce the deviation of the output voltage from the target value at the time of the abrupt change of the load, the control unit 40 of the power conversion device 50 according to the
15 present Example 1 includes the current command value
correction unit 10. As described above, when the load current abruptly increases, the voltage difference Verr becomes positive owing to the decrease of the output voltage Vout, and, because the inductor current Iout
20 passively increases and the response speed of the voltage control system is set relatively slow, the current difference Ierr becomes negative. At this time, the current command value correction unit 10 corrects the current command value Iref so that the current command
25 value Iref may become closer to the actual inductor current

13
Iout that has already increased. With this, the phenomenon in which the current control unit 12 delays the increase of the inductor current Iout is alleviated. Accordingly, it is possible to suppress the fluctuation of the output 5 voltage when the load current abruptly increases by the current command value correction unit 10. [0029]
On the other hand, if the load current abruptly decreases, the increase and decrease of the current and the
10 increase and decrease of the voltage may be opposite to
each other, and the same phenomenon as in the case where the load current abruptly increases may occur. In other words, when the load current abruptly decreases, the voltage difference Verr becomes negative owing to the
15 increase of the output voltage Vout, and on top of that, the inductor current Iout passively decreases and the response speed of the voltage control system is set relatively slow, so that the current difference Ierr becomes positive. At this time, the current command value
20 correction unit 10 corrects the current command value Iref
so that the current command value Iref may become closer to the actual inductor current Iout that has already decreased. With this, the phenomenon in which the current control unit 12 delays the decrease of the inductor current Iout is
25 alleviated. Accordingly, it is possible to suppress the

14
fluctuation of the output voltage even if the load current
abruptly decreases.
[0030]
As described above, when the load current abruptly 5 changes, the polarity (positive/negative) of the voltage
difference Verr and the polarity (positive/negative) of the current difference Ierr becomes opposite to each other. In other words, the polarity of the voltage difference Verr is positive (Verr>0) and the polarity of the current
10 difference Ierr is negative (Ierr<0) when the load current abruptly increases, and the polarity of the voltage difference Verr is negative (Verr<0) and the polarity of the current difference Ierr is positive (Ierr>0) when the load current abruptly decreases.
15 [0031]
Accordingly, when the polarity of the voltage difference Verr and the polarity of the current difference Ierr are different from each other, by correcting the current command value Iref so that the current command
20 value Iref may become closer to the inductor current detection value Iout, it is possible to suppress the fluctuation of the output voltage when the load current abruptly increases or decreases. In other words, the response of the control against the abrupt change of the
25 load can be speeded up.

15
[0032]
An example of means for correcting the current command value Iref executed by the current command value correction unit 10 will be described with reference to 5 Figure 2 to Figure 4. [0033]
Figure 2 is a control function block diagram showing a configuration example of the control unit 40 in Figure 1. In this configuration example, the voltage control unit 11
10 and the current control unit 12 of the control unit 40 are composed of proportional integral control units. Here, Kp_V represents a voltage control proportional gain, Ki_V represents a voltage control integral gain, Kp_I represents a current control proportional gain, and Ki_I represents a
15 current control integral gain. [0034]
In the voltage control unit 11 (AVR), an added value is obtained by adding the correction amount Y, which is obtained by the current command value correction unit 10,
20 to an integrated value obtained by multiplying the voltage difference Verr (= Vref-Vout), which is obtained by a proportional calculation unit, by the voltage control integral gain Ki_V, and the added value is integrated by the integration calculation unit. The voltage control unit
25 11 (AVR) calculates a current command value Iref by adding

16
this integrated value and an integrated value obtained by
multiplying the voltage difference Verr by the voltage
control proportional gain Kp_V.
[0035]
5 The current control unit 12 (ACR) integrates an
integrated value obtained by multiplying the current difference Ierr (=Iref-Iout) by the current control integral gain Ki_I. The current control unit 12 (ACR) calculates the ON-time ratio (duty) by adding this
10 integrated value and an integrated value obtained by
multiplying the current difference Ierr by the current
control proportional gain Kp_I.
[0036]
Figure 3 shows an example of a relationship between
15 the voltage difference Verr, the current difference Ierr,
and the correction amount Y obtained by the current command value correction unit 10. In Figure 3, the horizontal axis represents the current difference Ierr, and the vertical axis represents the correction amount Y.
20 [0037]
The current command value correction unit 10 sets the correction amount Y on the basis of the relationship shown in Figure 3 in accordance with the voltage difference Verr and the current difference Ierr.
25 [0038]

17
As shown in Figure 3, when the polarity of the voltage difference Verr and the polarity of the current difference Ierr are the same (the broken line (Verr>0) in the case of Ierr>0, and the solid line (Verr<0) in the case 5 of Ierr<0), the correction quantity Y which the current
command value correction unit 10 outputs is zero. On the other hand, when the polarity of the voltage difference Verr is different from the polarity of the current difference Ierr (the solid line (Verr<0) in the case of
10 Ierr>0, and the broken line (Verr>0) in the case of Ierr<0), the current command value correction unit 10 outputs the correction amount Y in accordance with the magnitude of the current difference Ierr, that is, the correction amount Y in proportional to the magnitude of the Ierr in Figure 3.
15 Note that the voltage difference Verr is a parameter for setting the gradient of a straight line indicating a relationship between Y and Ierr, and the gradient varies in accordance with the magnitude of the voltage difference Verr (|Verr|).
20 [0039]
Figure 4 shows another example of the relationship between the voltage difference Verr, the current difference Ierr, and the correction amount Y obtained by the current command value correction unit 10. In Figure 4, the
25 horizontal axis represents the current difference Verr, and

18
the vertical axis represents the correction amount Y. [0040]
The current command value correction unit 10 sets the correction amount Y on the basis of the relationship shown 5 in Figure 4 in accordance with the voltage difference Verr and the current difference Ierr. [0041]
As shown in Figure 4, when the polarity of the voltage difference Verr and the polarity of the current
10 difference Ierr are the same (the broken line (Ierr>0) in
the case of Verr>0, and the solid line (Ierr<0) in the case of Verr<0), the correction quantity Y which the current command value correction part 10 outputs is zero. On the other hand, when the polarity of the voltage difference
15 Verr is different from the polarity of the current
difference Ierr (the solid line (Ierr<0) in the case of Verr>0, and the broken line (Ierr>0) in the case of Verr<0), the current command value correction unit 10 outputs the correction amount Y in accordance with the magnitude of the
20 voltage difference Verr, that is, the correction amount Y in proportional to the magnitude of the Verr in Figure 4. Note that the current difference Ierr is a parameter for setting the gradient of a straight line indicating a relationship between Y and Verr, and the gradient varies in
25 accordance with the magnitude of the voltage difference

19
Ierr (|Ierr|). [0042]
As shown in Figure 3 and Figure 4, when the load (Iload) abruptly increases to create a condition in which 5 Verr>0 and Ierr<0, the correction amount Y is positive. Therefore, since Iref which the voltage control unit 11 outputs increases, Iout promptly increases. As a result, it is possible to suppress the decrease of Vout owing to the abrupt increase of the load. On the other hand, when
10 the load (Iload) abruptly decreases to create a condition in which Verr<0 and Ierr>0, the correction amount Y is negative. Accordingly, Iref outputted by the voltage control unit 11 decreases, so that Iout rapidly decreases. Thus, the increase of Vout owing to the abrupt decrease of
15 the load can be suppressed. [0043]
In this way, when the polarity of the voltage difference Verr and the polarity of the current difference Ierr are different from each other, the current command
20 value correction unit 10 outputs the correction amount Y on the basis of the relationships shown in Figures 3 and 4, which makes it possible to correct the current command value Iref so that the current command value Iref may become closer to Iout which increases or decreases
25 passively along with the abrupt change of the load.

20
[0044]
Note that, as shown in Figure 3, because the magnitude of the correction amount Y is set proportional to the magnitude of the current difference Ierr, it is 5 prevented that the correction amount Y discontinuously changes and becomes unstable at an instant when the magnitude relationship between the current command value Iref and the current detection value Iout is reversed. In addition, as shown in Figure 4, since the magnitude of the
10 correction amount Y is set proportional to the magnitude of the voltage difference Verr, it is possible to prevent the correction amount Y from discontinuously changing and becoming unstable at an instant when the magnitude relationship between the voltage command value Vref and the
15 voltage detection value Vout is reversed. [0045]
The correction amount Y shown in Figure 3 and Figure 4 is calculated by, for example, the following expressions using K(>0) as a correction gain in the current command
20 value correction unit 10.
Y=-K×Verr×Ierr (in the case of the load rapidly increasing (Verr>0 and Ierr<0),
Y=+K×Verr×Ierr (in the case of the load rapidly decreasing (Verr<0 and Ierr>0), and
25 Y=0 (in the case of the polarities of Verr and Ierr

21
being the same).
The current command value correction unit 10 receives Verr and Ierr, selects one of the above expressions on the basis of the polarities of the inputted Verr and Ierr, and 5 calculates Y using the selected expression. The current
command value correction unit 10 outputs the calculated Y
to the voltage control unit 11 (AVR).
[0046]
Here, in the present Example 1, directions indicated
10 by arrows in Figure 1 are defined as positive directions
regarding the direction of Iout and the direction of Vout. In other words, the direction from the low potential side toward the high potential side is defined as the positive direction of Vout, and the direction of Iout that increases
15 the magnitude of Vout in the positive direction is defined as the positive direction of Iout. The same is true of the direction of Iref which is the command value of Iout and the direction of Vref which is the command value of Vout. [0047]
20 In addition, in the present Example 1, it is defined
that the current difference Ierr and the voltage difference Verr are obtained by subtracting the detection values from the command values respectively (Ierr=Iref-Iout, Verr=Vref-Vout). These definitions of the current difference Ierr
25 and the voltage difference Verr are not limited to these

22
definitions, and other definitions may be used, but in that case, the definitions related to the positive and negative polarities of Verr, Ierr, and Y have only to be changed as appropriate. 5 [0048]
As described above, according to the present Example 1, even if the load abruptly changes, it is possible to suppress the fluctuation of the output voltage of the power conversion device.
10 [0049]
In the present Example 1, as shown in Figure 2, Iref is corrected by adding the correction amount Y to the input of the integration calculation unit in the voltage control unit 11. As a result, it is possible to more reliably
15 suppress the fluctuation of the output voltage.
Alternatively, Iref may be corrected by other means such as means in which the calculation result (Iref) itself of the PI calculation unit of the voltage control unit 11 is corrected using the correction amount Y.
20 [0050]
Note that, in the present Example 1, as for the currents (the detection current and the current command) and the voltages (the detection voltage and the voltage command) in the current mode voltage control, that is, as
25 for the reactor current (Iout) and its current command

23
(Iref) and the output voltage (Vout) and its voltage command (Vref), the directions (positive directions) of the above currents and voltages are defined as directions in which the voltages increase as the currents increase. 5 Furthermore, under such definitions of the directions of the currents and the voltages, the current difference (Ierr) and the voltage difference (Verr) are defined as values obtained by subtracting the detection values from the command values respectively (Ierr=Iref-Iout, Verr=Vref-10 Vout). In addition, it is conceivable to define the
directions of the currents and the voltages as directions different from those defined in the present Example 1, or to define the current difference and the voltage difference as values obtained by subtracting the command values from 15 the detection values respectively (Ierr=Iout-Iref,
Verr=Vout-Vref). In this way, when the definitions are set different from the present example, the positive polarity and the negative polarity of the current and those of the voltage and the positive polarity and the negative polarity 20 of the current difference and those of the voltage difference have only to be changed as appropriate. [0051]
Figure 5 is the configuration diagram of a power 25 conversion device according to Example 2 of the present

24
invention. Hereinafter, differences from Example 1 will be
mainly described.
[0052]
A power conversion device 51 of the present Example 2 5 is an inverter device that receives DC power from input
terminals J19 and J20 and outputs three-phase AC power to
output terminals J14 to J16.
[0053]
The power conversion device 51 includes a three-phase
10 bridge circuit 61 composed of switching elements S11 to S16 to which diodes DS11 to DS16 are connected in anti-parallel respectively; a series-connected circuit composed of DC capacitors C14 and C15 that are disposed between DC terminals J17 and J18 of the three-phase bridge circuit 61;
15 inductors L11 to L13 one end of each of which is connected to each of the three-phase AC terminals J11 to J13 of the three-phase bridge circuit 61 respectively; and AC
capacitors C11 to C13 one end of each of which is connected to the other end of each of the inductors L11 to L13
20 respectively. The other ends of these AC capacitors C11 to C13 are connected to the series connection point of the DC capacitor C14 and the DC capacitor C15. [0054]
In the present Example 2, MOSFETs are adopted as the
25 switching elements S11 to S16. Here, if switching elements

25
each of which includes a body diode such as a MOSFET are
adopted, the diodes DS11 to DS16 may be omitted.
[0055]
Furthermore, the power conversion device 51 includes: 5 voltage sensors 31 to 33 for detecting the voltages of the capacitors C11 to C13 respectively; current sensors 34 to 36 for detecting the currents of the inductors L11 to L13 respectively; and a control unit 41 for controlling the switching operations of the switching elements S11 to S16.
10 In addition, the DC terminals J17 and J18 of the three-phase bridge circuit 61 are electrically connected to the input terminals J19 and J20 of the power conversion device 51 respectively, and the connection point of the inductors L11 and the AC capacitor C11, the connection point of the
15 inductors L12 and the AC capacitor C12, and the connection point of the inductors L13 and the AC capacitor C13 are electrically connected to the output terminals J14 to J16 of the power conversion device 51 respectively. [0056]
20 The control unit 41 controls the ON/OFF operations of
the switching elements S11 to S16, and thereby controls the voltages of the capacitors C11 to C13 respectively detected by the voltage sensors 31 to 33 and the currents of the inductors L11 to L13 respectively detected by the current
25 sensors 34 to 36.

26
[0057]
To put it more concretely, the control unit 41 calculates a U-phase inductor current command value so that the voltage (U-phase voltage) detection value Vout1 of the 5 capacitor C11 may follow a U-phase voltage command value, and further calculates the ON-time ratios of the U-phase switching elements S11, S12 so that the current (U-phase inductor current) detection value Iout1 of the inductor L11 may follow a U-phase inductor current command value. At
10 this time, similarly to the control unit 40 described in Example 1, the control unit 41 calculates a voltage difference, a current difference, and a correction amount. [0058]
As for the voltages (V-phase voltage and W-phase
15 voltage) of the capacitors C12 and C13 and the currents (V-phase current and W-phase current ) of the inductors L12 and L13, the V-phase and W-phase voltage differences, the V-phase and W-phase current differences, and the V-phase and W-phase correction amounts are obtained by calculation,
20 and the ON-time ratios of the V-phase and W-phase switching elements S13 to S16 are obtained by calculation, and the voltages (V-phase voltage and W-phase voltage) of the capacitors C12 and C13 and the currents (V-phase current and W-phase current ) of the inductors L12 and L12 are
25 controlled in a similar way to the U-phase voltage and the

27
U-phase inductor current.
[0059]
According to the present Example 2, by applying the
same control unit configuration as adopted in Example 1 to 5 the inverter device the output voltage of which is an AC
voltage and the instantaneous value thereof changes
momentarily, it is possible to suppress the variation of
the output voltage when a load connected to the inverter
device abruptly changes. 10
[0060]
Figure 6 is the configuration diagram of a power
conversion device according to Example 3 of the present
invention. Hereinafter, differences from Example 2 will be 15 mainly described.
[0061]
A power conversion device 52 according to the present
Example 3 is an AC/DC converter device which receives
three-phase AC power from input terminals J14 to J16 and 20 outputs DC power to output terminals J19 and J20. Here,
the main circuit configuration of the power conversion
device 52 is the same as that of the power conversion
device 51 of Example 2.
[0062]
25 Unlike Example 2, the power conversion device 52

28
includes a voltage sensor 37 that detects a voltage across the series-connected circuit composed of the capacitors C14 and C15, that is, the voltage between the input terminals J19 and J20. 5 [0063]
A control unit 42 has a function of controlling currents inputted from the input/output terminals J14 to J16 so that the currents may be turned into a three-phase AC waveform, and controls a DC voltage Vout0 by changing
10 the amplitudes or the active currents of the inputted currents. [0064]
To put it more concretely, the control unit 42 calculates the amplitudes or active current command values
15 of U-phase, V-phase, and W-phase inductor current command
values so that the DC voltage Vout0 detected by the voltage sensor 37 may follow the DC voltage command value, and generates the current command values of the three-phase AC waveform. Then, the ON-time ratios of the switching
20 elements S11 to S16 are calculated so that the detection values Iout1 to Iout3 of the currents (U-phase, V-phase, and W-phase inductor currents) of the inductors L11 to L13 may follow these current command values. At this time, similarly to the control unit 40 shown in Example 1, the
25 differences of the DC voltages, the amplitudes of the

29
inductor currents or the differences of the active currents,
the inductor current amplitude command values, or the
correction amounts of the active current command values are
calculated. 5 [0065]
According to the present example, by applying the
same control unit configuration as adopted in Example 1 to
the converter device the input current of which is an AC
current and the instantaneous value thereof changes 10 momentarily, it is possible to suppress the variation of
the DC voltage when a load connected to the converter
device abruptly changes.

[0066]
15 Figure 7 is the configuration diagram of a power
conversion device according to Example 4 of the present
invention.
[0067]
A power conversion device 53 of Example 4 is an 20 insulated DC-DC converter device that receives DC power
from input terminals J21 and J22, and outputs DC power to
output terminals J23 and J24.
[0068]
In the power conversion device 53, there is a full 25 bridge circuit 62 that is composed of switching elements

30
H21 to H24 to which diodes DH21 to DH24 are connected in anti-parallel respectively, and the full bridge circuit 62 converts the DC voltage of a capacitor C21 into an AC voltage, and applies the AC voltage to the series-connected 5 body composed of a resonance inductor Lr1, a resonance
capacitor Cr1, and the primary winding N1 of a transformer
T1.
[0069]
In the present Example 4, MOSFETs are adopted as the
10 switching elements H21 to H24. Here, if switching elements each of which includes a body diode such as MOSFETs are adopted, the diodes DS21 to DS24 may be omitted. [0070]
The transformer T1 magnetically couples the primary
15 winding with a secondary winding. An AC current induced in the secondary winding is rectified by a rectifier circuit 63 composed of diodes D21 to D24 and the rectified current is supplied to a capacitor C22. Then, one end and the other end of the capacitor C21 are electrically connected
20 to the input terminals J21 and J22 of the power conversion device 53 respectively, and one end and the other end of the capacitor C22 are electrically connected to the output terminal J23 sand J24 of the power conversion device 53 respectively.
25 [0071]

31
A control unit 43 controls the ON/OFF operations of the switching elements H21 to H24 to control the voltage of the capacitor C22 detected by a voltage sensor 38 and the current of the primary winding N1 of the transformer T1 5 detected by a current sensor 39. [0072]
To put it more concretely, the control unit 43 calculates a transformer primary current command value so that the voltage (output voltage) detection value of the
10 capacitor C22 may follow an output voltage command value,
and further calculates the ON-time ratios of the switching elements H21 to H24 so that the current (transformer primary current) detection value of the primary winding N1 may follow the transformer primary current command value.
15 At this time, similarly to the control unit 40 described in Example 1, the control unit 43 calculates a voltage difference, a current difference, and a correction amount. [0073]
According to the present Example 4, it is possible to
20 suppress the variation of the output voltage in response to the abrupt change of the load current in the insulated DC-DC converter device. [0074]
Note that in the present example, although the
25 transformer primary current is set to a current control

32
target, and the voltage of the capacitor C22 is set to a voltage control target, it is conceivable that the
transformer secondary current (the current of the secondary winding of the transformer T1), the current inputted into 5 the full-bridge circuit 62, or the current outputted from
the rectifier circuit 63 is set to a current control target. If a set of a voltage control target and a current control target is selected such that the current control target increases or decreases as the voltage control target
10 increases or decreases, it is possible to suppress the
variation of the voltage control target at the time of the abrupt change of the load by correcting such a current command Iref as mentioned above.
15 [0075]
Figure 8 is the configuration diagram of a power conversion device according to Example 5 of the present invention. Hereinafter, differences from Example 1 will be mainly described. Here, in Figure 8, suffixes (ref
20 (command), out (output), err (difference), and load (load)) of the current I and the voltage V have the same meanings as the suffixes described in the examples 1 to 4 have. [0076]
In the power conversion device, a plurality of DC/DC
25 converter units (two in the case of Figure 8) having the

33
same main circuit configurations (the switching legs 64 and 65) as the power conversion device 50 shown in Example 1 (Figure 1) are connected in multi-parallel with one another. However, a capacitor C3 at the input side and a capacitor 5 C4 at the output side are used in common with all the DC/DC converter units. [0077]
In a control unit, although current control units (72 and 73) are provided to the respective DC/DC converter 10 units, a voltage control unit 71 and a current command
value correction unit 70 are used in common with all the DC/DC converter units. In other words, a current command Iref0 and a correction amount (equivalent to “Y” in Example 1 (Figure 2)) are used in common with all the DC/DC 15 converter units. [0078]
The current command value correction unit 70 calculates the correction amount on the basis of the average value Ierr0 of a current difference Ierr1 (=Iref0-20 Iout01) in one of the DC/DC converter units and a current difference Ierr2 (=Iref0-Iout02) in the other DC/DC converter unit and a voltage difference Verr0 (=Vref0-Vout0). Here, the average value Ierr0, that is, an average current difference, is calculated by an average value 25 calculation unit 76 using, for example, an arithmetic

34
average (Ierr0=(Ierr1+Ierr2)/2). [0079]
According to the present Example 5, in the power conversion device in which the plurality of DC/DC converter 5 devices are connected in multi-parallel, it is possible to suppress the fluctuation of the output voltage when the load abruptly changes. Furthermore, since the common current command value is used for the respective DC/DC converter devices, it is possible to balance currents
10 allotted to the respective power conversion devices with one another. [0080]
Note that the present invention is not limited to the above embodiment, and the present invention may include
15 various kinds of modifications. For example, the above
examples have been described in detail in order to explain the present invention in an easily understood manner, and the present invention is not necessarily limited to examples including all the configurations that have been
20 described so far. Furthermore, a new example of the
present invention may be made by adding, deleting, or replacing another configuration to a part of the
configuration of each example with another configuration. [0081]
25 For example, each of the power conversion devices of

35
the main circuit configurations shown in Figure 5 to Figure
7 may be replaced with a plurality of power conversions
connected in multi-parallel.
[0082]
5 Furthermore, a single switching element such as a
step-down chopper may be used as the main circuit unit of a
power conversion device.
Reference Signs List
[0083]
10 1... DC power supply,
2... DC load,
50 to 53... power conversion device,
60... switching leg,
61... three-phase bridge circuit,
15 62... full bridge circuit,
63... rectifier circuit,
40 to 43... control unit,
10... current command value correction unit,
11... voltage control unit,
20 12... current control unit,
13... PWM signal generation unit
21, 31 to 33, 37, 38... voltage sensor,
22, 34 to 36, 39... current sensor, L, L11 to L13... inductor,
25 C1, C2, C21, C22... capacitor,

36
C14, C15... DC capacitor,
C11 to C13... AC capacitor,
Lr1... resonance inductor,
Cr1... resonance capacitor,
5 T1... transformer,
N1, N2... winding,
Q1, Q2, S11 to S16, H21 to H24... switching element, DS11, DS16, DH21 to DH24, D21 to D24... diode

WE CLAIM:

1.A power conversion device comprising:
a main circuit unit having switching elements;
5 a voltage control unit for generating a current
command value on the basis of a voltage difference between a voltage command value and a voltage detection value; and a current control unit for controlling the switching elements on the basis of a current difference between the 10 current command value and a current detection value, and
a current command value correction unit for correcting the current command value on the basis of the voltage difference and the current difference.
15 2. The power conversion device according to claim 1, wherein the current command value correction unit corrects the current command value in accordance with the polarity of the voltage difference and the polarity of the current difference.
20
3. The power conversion device according to claim 2, wherein the current command value correction unit corrects the current command value so that the current command value becomes closer to the current detection value.
25

38
4. The power conversion device according to claim 2,
wherein the current command value correction unit
corrects the current command value so that a correction amount increases in accordance with the magnitude of the 5 current difference.
5. The power conversion device according to claim 2,
wherein the current command value correction unit
corrects the current command value so that a correction 10 amount increases in accordance with the magnitude of the voltage difference.
6. The power conversion device according to claim 2,
wherein further the current command value correction
15 unit does not correct the current command value when the
polarity of the voltage difference and the polarity of the current difference are the same.
7. The power conversion device according to claim 2,
20 wherein the current command value correction unit
corrects the current command value so that the current command value becomes closer to the current detection value when the polarity of the voltage difference and the polarity of the current difference are different from each 25 other in the case where a direction of a voltage to be

39
controlled and a direction of a current to be controlled
are defined in such a way that, if the current is increased,
the voltage increases.
5 8. The power conversion device according to claim 7,
wherein the voltage to be controlled is a voltage on an output side of the main circuit unit.
9. The power conversion device according to claim 8,
10 wherein the current to be controlled is a current at
the output side of the main circuit unit.
10. The power conversion device according to claim 9,
wherein the main circuit unit has a series-connected
15 circuit composed of a capacitor and a reactor on the output side,
the voltage to be controlled is a voltage of the capacitor, and
the current to be controlled is a current of the 20 reactor.
11. The power conversion device according to claim 10,
wherein the main circuit unit is a DC/DC converter
including a switching leg. 25

40
12. The power conversion device according to claim 10,
wherein the main circuit unit is an inverter including a three-phase bridge circuit.
5 13. The power conversion device according to claim 8,
wherein the current to be controlled is a current at an input side of the main circuit unit.
14. The power conversion device according to claim 13,
10 wherein the main circuit unit is an AC/DC converter
including a three-phase bridge circuit.
15. The power conversion device according to claim 8,
wherein the current to be controlled is a current
15 between the input side and the output side of the main circuit unit.
16. The power conversion device according to claim 15,
wherein the main circuit unit is an insulated DC/DC
20 converter, and
the electric current to be controlled is a winding current of a transformer included in the insulated DC/DC converter.
25 17. A power conversion device comprising:

41
a plurality of main circuit units that are connected in multi-parallel, and each of which has switching elements;
a voltage control unit for generating a current 5 command value on the basis of a voltage difference between a voltage command value and a voltage detection value; and
a plurality of current control units each of which controls the switching elements on the basis of a current difference between the current command value and the 10 current detection value of the main circuit unit, and
a current command value correction unit for correcting the current command value on the basis of an average value of the current differences of the plurality of main circuit units.