JP6553985B2 - Power converter - Google Patents

Description

  The present invention relates to a multi-parallel power conversion device that connects a plurality of power converters in parallel to supply DC power to a load.

  Power converters are applied to applications ranging from small supply power fields to large ones, such as battery powering of electric vehicles and power converters for grid interconnection.

  In the case of supplying a large amount of power to a load in a power converter, a method of connecting the outputs of a single power converter in parallel is conventionally employed. However, when power converters are connected in parallel, a cross current is generated at the output due to differences in output voltage differences between the power converters and impedances of the input and output, and problems such as output reduction due to current imbalance and increase in output ripple Arise.

  Therefore, for example, Patent Document 1 discloses a multiple parallel DC chopper device that suppresses a cross current by connecting in parallel a DC chopper device provided with a reactor for cross current suppression and equalizing input impedance.

JP 2007-14109 A

  FIG. 6 is a circuit diagram showing a configuration of a multi-parallel chopper device disclosed in Patent Document 1. As shown in FIG. As shown in FIG. 6, cross current suppression reactors 3A, 3B,..., 3N are provided in series on the output side of a plurality of chopper devices 2A, 2B,. By making the input wiring impedance to the device equal, returning one negative output to the connection point B, cut off the loop in which the return current flows to the negative side of the chopper, and perform complex control. There is no cross current suppression with an easy circuit configuration.

  However, since it is necessary to provide each DC chopper device with a cross current suppression reactor, there is a problem that the size of the entire device is increased and the cost is increased. In addition, since it is necessary to equalize the input impedance, it is difficult to realize a wiring method to equalize the input impedance depending on the specifications of the device.

  An object of the present invention made in view of such circumstances is to provide a power conversion device capable of suppressing a cross flow with a simple and compact configuration.

In order to solve the above problems, a power conversion device according to the present invention is a power conversion device in which two power converters are connected in parallel, and each power converter is a reverse conversion that converts a DC voltage into an AC voltage. And a forward converter that converts the AC voltage converted by the inverse converter into a DC voltage, an insulating transformer, and a gate drive circuit, and the primary winding of the insulating transformer is configured to pass through the reactor. The secondary winding of the isolation transformer is connected to the inverse transformer, the secondary winding of the isolation transformer is connected to the forward converter via a reactor, and the reactor connected to the secondary winding of the isolation transformer is electromagnetically coupled at the same pole. The reverse converter includes a first leg having a first switching element and a second switching element, and a second leg having a third switching element and a fourth switching element, and the forward converter is a fifth switch. N A third leg having an element and a sixth switching element, and a fourth leg having a seventh switching element and an eighth switching element, wherein the gate drive circuit includes the first switching element, the second switching element, and The fifth switching element and the sixth switching element are turned on at different timings, and the gate drive circuit turns on the first switching element and the fourth switching element at the same time, and then the first dead time period elapses. The second switching element and the third switching element are simultaneously turned on, and the sixth switching element and the seventh switching are performed after the second dead time period has elapsed after the fifth switching element and the eighth switching element are simultaneously turned on. It is characterized in that on the device at the same time .

The power converter according to the present invention is a power converter in which n power converters are connected in parallel, and each power converter is an inverse converter that converts a DC voltage to an AC voltage; A forward converter that converts an AC voltage converted by the converter into a DC voltage, an insulation transformer, and a gate drive circuit. A primary winding of the insulation transformer is connected to the inverse converter via a reactor. The secondary winding of the isolation transformer is connected to the forward converter via (n-1) reactors connected in series and connected to the secondary winding of the isolation transformer (n -1) The reactors are electromagnetically coupled to each other between different power converters with the same polarity, and the inverse converter includes a first leg having a first switching element and a second switching element, a third switching element, and a first switching element. 4 switching elements The forward converter includes a third leg having a fifth switching element and a sixth switching element, and a fourth leg having a seventh switching element and an eighth switching element, and the gate The drive circuit turns on the first switching element, the second switching element, the fifth switching element, and the sixth switching element at different timings, and the gate driving circuit includes the first switching element and the first switching element. After simultaneously turning on the four switching elements, after the first dead time period has elapsed, simultaneously turning on the second switching element and the third switching element, and simultaneously turning on the fifth switching element and the eighth switching element, After the second dead time period has elapsed, the sixth switching element and Characterized by turning on the serial seventh switching element at the same time.

  According to the present invention, in a system in which a plurality of power converters are connected in parallel, crossflow can be suppressed with a simple and compact configuration.

It is a circuit diagram showing an example of composition of a power converter concerning a 1st embodiment of the present invention. It is a figure which shows the schematic waveform in each operation mode of the power converter device which concerns on the 1st Embodiment of this invention. It is a figure explaining each operation mode of a power converter in a power converter concerning a 1st embodiment of the present invention. It is a figure explaining each operation mode of a power converter in a power converter concerning a 1st embodiment of the present invention. It is a figure explaining an example of the effect of the electromagnetic coupling reactor applied to the 1st Embodiment of this invention. It is a circuit diagram which shows the structural example of the power converter device which concerns on the 2nd Embodiment of this invention. It is a circuit diagram which shows the structural example of the conventional multi-parallel chopper apparatus.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

First Embodiment
FIG. 1 is a block diagram illustrating a configuration example of a power conversion device according to the first embodiment of the present invention. In the example illustrated in FIG. 1, the power conversion device 1 includes a power converter 10, a power converter 20, gate drive circuits 51 and 52, and a PWM signal control circuit 60. The power conversion device 1 connects two power converters 10 and 20 in parallel to supply DC power to a load.

  The DC input power supply 100 is connected between the input terminals of the power converter 10 and the power converter 20.

  The power converter 10 is an insulation type DC power converter, and includes an inverter 11, an input smoothing capacitor 13, a reactor 15, an isolation transformer 16, a reactor 17, a forward converter 12, and an output smoothing capacitor. 14.

  Between the input terminals of the power converter 10, an input smoothing capacitor 13 and an inverse converter 11 are connected in parallel.

  A forward converter 12 and an output smoothing capacitor 14 are connected in parallel between the output terminals of the power converter 10. The power converter 10 is connected in parallel with the output terminal of the power converter 20.

Inverse transformer 11, an AC to those switching elements Q _11a and Q _11b are connected in series, that the switching elements Q _11c and Q _11d are connected in series and are configured by connecting in parallel, the DC voltage Convert to voltage.

  The input smoothing capacitor 13 keeps the input voltage constant.

The reactor 15 is connected between a connection point a11 where the switching elements _Q11a and _Q11b are connected in series and a connection point b11.

The insulation transformer 16 includes a winding (primary winding) n11 on the primary side and a winding (secondary winding) n12 on the secondary side. The primary winding n11 has a connection point b11, the switching element _{Q 11c} and _{Q 11d} is connected between the connection point c11 which are connected in series, the secondary winding n12, a connection point b12, the switching element Q _12a and _{Q 12b} are connected between the connection point c12 which are connected in series. The inverse converter 11 is connected to the primary winding n11 of the insulating transformer 16 through the reactor 15. The forward converter 12 is connected to the secondary winding n12 of the insulating transformer 16 through the reactor 17.

Reactor 17 includes a connection point b12, the switching element _{Q 12c} and _{Q 12d} is connected between the connection point a12 connected in series. Moreover, the reactor 17 is electromagnetically coupled by the same polarity (same polarity) as the reactor 27.

In the forward converter 12, one in which switching elements Q _12a and Q _12b are connected in series and one in which switching elements Q _12c and Q _12d are connected in series are connected in parallel Convert to voltage.

  The output smoothing capacitor 14 keeps the output voltage constant.

  The power converter 20 includes an input smoothing capacitor 23, an inverse converter 21, a reactor 25, an isolation transformer 26, a reactor 27, a forward converter 22, and an output smoothing capacitor 24. About the structure and connection of the power converter 20, since it is the same as that of the power converter 10, description is abbreviate | omitted. In addition, in order to distinguish from the power converter 10, the code | symbol of a component is changed.

  The PWM signal control circuit 60 generates a PWM signal and distributes the common PWM signal to the gate drive circuits 51 and 52.

The gate drive circuit 51 uses the PWM signal input from the PWM signal control circuit 60 to switch the switching elements _Q11a , _Q11b , _Q11c , _Q11d , _Q12a , _Q12b , _Q12c and Q of the power converter 10. _{12 d} is driven to perform on / off control. The gate drive circuit 52 uses the PWM signal input from the PWM signal control circuit 60 to switch the switching elements _Q21a , _Q21b , _Q21c , _Q21d , _Q22a , _Q22b , _Q22c and Q of the power converter 20. _22d is driven to perform on / off control. The gate drive circuits 51 and 52 have the same configuration.

  Operation | movement of the power converter device 1 comprised as mentioned above is demonstrated.

FIG. 2 is a diagram showing schematic waveforms in each operation mode of the power conversion device 1. The switching element _{Q 11a, Q 11b, Q 11c} , Q 11d, Q 12a, Q 12b, Q 12c, Q 12d, Q 21a, Q 21b, Q 21c, Q 21d, Q 22a, Q 22b, Q 22c and _{Q 22 d} is As shown in FIG. 2, the switching element is turned on and off while having a dead time period.

  The on / off operation of the switching element is switching-controlled based on a 50% duty fixed PWM signal generated by the PWM signal control circuit 60.

  The operation of each mode of the power converter 10 will be described with reference to FIG.

<FIG. 3 (b) mode a-2 (power transmission period)>
When the switching elements _Q12a and _Q12d on the secondary side are turned on with the switching elements _Q11a and _Q11d on the primary side turned on, the current _IL2 rises sharply. Thus, reactor 17, secondary winding n12 of the isolation transformer 16, was flowing in the path of the switching element antiparallel connected diodes _{D 5} to _{Q 12a,} diode _{D 8,} which are connected in inverse parallel to the switching element _{Q 12d} current The direction of I _L2 is switched, and a current I _L2 flows in the path of the switching element Q _12a , the secondary winding n12 of the isolation transformer 16, the reactor 17, and the switching element Q _{12 d} . As a result, as shown in mode a-2 in FIG. 2, the current rises from negative to positive and power is transmitted.

<FIG. 3 (c) mode b-1 (secondary side dead time period)>
Next, when the switching element _{Q 12a} and _{Q 12d} of the secondary side is turned off, the energy stored in the reactor 17 during the dead time, diode _{D 6} and D which are connected in inverse parallel to the switching element _{Q 12c} and _{Q 12b The} current I _L2 flows through the path ₇ . No power transfer takes place during this dead time.

<FIG. 3 (d) mode b-2 (power transmission stop period)>
When the dead time period of the secondary side is finished, the switching element _{Q 12c} and _{Q 12b} of the secondary side is turned on, the secondary winding n12 of the isolation transformer 16, reactor 17, which is connected in inverse parallel to the switching element _{Q 12c} diode D _7, a current flows through a path of the diode _{D 6} which are connected in inverse parallel to the switching element _{Q 12b.} At this time, since the current flows through the path of the switching element Q _11a , the reactor 15, the primary winding n ₁₁ of the insulating transformer 16 and the switching element Q _{11 d on} the primary side, as shown in mode b-2 in FIG. A voltage is generated in the same direction in the primary winding n11 and the secondary winding n12 of the isolation transformer 16, and power transmission on the primary side and the secondary side is stopped.

<FIG. 3 (e) mode c-1 (primary side dead time period)>
Next, when the switching element _{Q 11a} and _{Q 11d} of the primary side is turned off, the energy stored in the reactor 15 during the dead time, diode _{D 2} and D which are connected in inverse parallel to the switching element _{Q 11c} and _{Q 11b The} current I _L1 flows through the path ₃ . No power transfer takes place during this dead time.

<FIG. 3 (f) mode c-2 (power transmission period)>
When the primary-side dead time period ends, the primary-side switching elements Q _11c and Q _11b are turned on. In a state where the switching element _{Q 12b} and _{Q 12C} of the secondary side is on, the switching element _{Q 11c} and _{Q 11b} of the primary side is turned on, the current _{I L2} decreases drastically, the reactor 17, the isolation transformer 16 Of the current I _L2 flowing in the path of the secondary winding n12, the diode D ₇ reverse-parallel connected to the switching element Q _{12 c} , and the diode D ₆ reverse-parallel connected to the switching element Q _{12 b} Q _12c, the reactor 17, secondary winding n12 of the isolation transformer 16, since the current flows _{I L2} in the path of the switching element _{Q 12b,} power down from the current positive, as shown in mode c-2 in FIG. 2 to the negative Is transmitted

<FIG. 3 (g) mode d-1 (secondary side dead time period)>
Next, when the switching elements Q _12c and Q _12b on the secondary side are turned off, the energy stored in the reactor 17 during the dead time causes the diodes D ₅ and D connected in antiparallel to the switching elements Q _12a and Q _{12d. The} current I _L2 flows through the path ₈ . No power transfer takes place during this dead time.

<Fig. 3 (h) mode d-2 (power transmission stop period)>
When the secondary-side dead time period ends, the secondary-side switching elements Q _12a and Q _12d are turned on, and the secondary winding n12 of the insulating transformer 16 and the diode D ₅ connected in reverse parallel to the switching element Q _12a , The current I _L2 flows through the path of the diode D ₈ and the reactor 17 connected in reverse parallel to the switching element Q _12d . At this time, the current I _L1 flows through the path of the switching element Q _11c , the primary winding n _{11 of} the insulating transformer 16, the reactor 15, and the switching element Q _{11 b on} the primary side. Thus, a voltage is generated in the same direction in the primary winding n11 and the secondary winding n12 of the isolation transformer 16, and power transmission on the primary side and the secondary side is stopped.

<FIG. 3 (a) mode a-1 (primary side dead time period)>
Then, 1 when the switching element _{Q 11c} and _{Q 11b} of the primary side is turned off, the energy stored in the reactor 15 during the dead time, diode _{D 1} and D which are connected in inverse parallel to the switching element _{Q 11a} and _{Q 11d The} current I _L1 flows through the path ₄ . No power transfer takes place during this dead time. When the dead time period ends, the mode is switched to mode a-2.

This switching operation is repeated to transmit power. The control of this switching operation is phase shift control, and as shown in FIG. 2, by adjusting the phase difference δ between the voltages on the primary side and the secondary side, the secondary side from the primary side of the isolation transformer 16 is obtained. Adjust the amount of power transmitted to the That is, power transfer is performed by controlling the phase of the output voltage V _L1 of the inverse converter 11 and the phase of the input voltage V _L2 of the forward converter 12.

  The operation of the power converter 20 is similar to that of the gate drive circuits 51 and 52, and the on / off operation of the switching element is performed by the same signal distributed from the PWM signal. Since the operation is similar to that of the vessel 10, the description thereof is omitted.

  The output of the power conversion device 1 is a combined output of the power converter 10 and the power converter 20.

  As described above, the power converter 10 and the power converter 20 perform switching operations with the same circuit configuration and the same PWM signal, but in general, the switching characteristics of the power converter 10 and the switching elements of the power converter 20 are Different.

  Therefore, the on / off timings of the switching elements of power converter 10 and power converter 20 are deviated due to the difference between the turn-on time of the switching element, the turn-off time, the storage time of the gate due to the variation of the switching characteristics A difference arises in the output voltage of the converter 10 and the power converter 20, and a cross current flows.

  However, in the present invention, since the reactors 17 and 27 of the plurality of power converters are electromagnetically coupled with the same polarity, the cross flow can be suppressed.

For example, as shown in FIG. 4, when the current _{I L12} flowing through the reactor 17 is greater than the current _{I L22} flowing through the reactor 27, when the inductance value of the reactor 17 and the reactor 27 is L, the voltage _{V L12} generated in reactor 17 The voltage V _L22 generated in the reactor 27 is given by the equations (1) and (2).

From the equation (1), the voltage V _L12 generated in the reactor 17 becomes V _L12 > 0, which works as a voltage drop. On the other hand, according to equation (2), the voltage V _L22 generated by the reactor 27 becomes V _L22 <0, which works as a voltage increase. For this reason, the current flowing on the secondary side of each of the power converters 10 and 20 is balanced, and the cross current can be suppressed.

Second Embodiment
Below, the power converter device which concerns on the 2nd Embodiment of this invention is demonstrated. The power converter 1 according to the first embodiment connects two power converters 10 and 20 in parallel, but the power converter according to the second embodiment connects three or more power converters in parallel. To do.

  FIG. 5 is a block diagram illustrating a configuration example of the power conversion device according to the second embodiment of the present invention. The power converter 2 shown in FIG. 5 connects three power converters 10, 20, and 30 in parallel. The power converter 10 includes reactors 17 and 18, the power converter 20 includes reactors 27 and 28, and the power converter 30 includes reactors 37 and 38. In order to suppress the cross current, the reactors 17 and 27, the reactors 28 and 37, and the reactors 18 and 38 are electromagnetically coupled with the same polarity. The other configurations and the operations of the power converters 10, 20, and 30 are the same as those in the first embodiment, and thus description thereof is omitted.

  Similarly, four or more power converters can be connected in parallel. That is, when the number of power converters connected in parallel is n, the secondary winding of the isolation transformer of each power converter is sequentially connected via (n-1) reactors connected in series. Connected to the converter. The (n-1) reactors are electromagnetically coupled with the same polarity between different power converters. Thereby, regardless of the number of power converters, cross current can be suppressed.

  Although the embodiments described above have been described as representative examples, it will be obvious to those skilled in the art that many modifications and substitutions can be made within the spirit and scope of the present invention. Therefore, the present invention should not be construed as being limited by the above-described embodiments, and various modifications and changes are possible without departing from the scope of the claims.

1, 2 power converter 10, 20, 30 power converter 11, 21 inverse converter 12, 22 forward converter 13, 23 input smoothing capacitor 14, 24 output smoothing capacitor 15, 25 reactor 16, 26 isolated transformer 17, 27 Electromagnetically coupled reactors 51, 52 Gate drive circuit 60 PWM signal control circuit 100 DC input power supply

Claims (2)

A power converter in which two power converters are connected in parallel,
Each power converter includes an inverse converter that converts a DC voltage into an AC voltage, a forward converter that converts the AC voltage converted by the inverse converter into a DC voltage, an insulation transformer, and a gate drive circuit. ,
The primary winding of the isolation transformer is connected to the inverter via a reactor,
The secondary winding of the insulation transformer is connected to the forward converter via a reactor,
The reactor connected to the secondary winding of the insulation transformer is electromagnetically coupled with the same polarity,
The inverter includes a first leg having a first switching element and a second switching element, and a second leg having a third switching element and a fourth switching element,
The forward converter includes a third leg having a fifth switching element and a sixth switching element, and a fourth leg having a seventh switching element and an eighth switching element,
The gate drive circuit turns on the first switching element, the second switching element, the fifth switching element, and the sixth switching element at different timings .
The gate driving circuit simultaneously turns on the second switching element and the third switching element after the first dead time period has elapsed after simultaneously turning on the first switching element and the fourth switching element, and A power converter characterized in that the sixth switching element and the seventh switching element are simultaneously turned on after a second dead time period after the switching element and the eighth switching element are simultaneously turned on . A power converter in which n power converters are connected in parallel,
Each power converter includes an inverse converter that converts a DC voltage into an AC voltage, a forward converter that converts the AC voltage converted by the inverse converter into a DC voltage, an insulation transformer, and a gate drive circuit. ,
The primary winding of the isolation transformer is connected to the inverter via a reactor,
The secondary winding of the isolation transformer is connected to the forward converter via (n-1) reactors connected in series;
The (n-1) reactors connected to the secondary winding of the isolation transformer are electromagnetically coupled to each other in the same pole between different power conversion devices,
The inverter includes a first leg having a first switching element and a second switching element, and a second leg having a third switching element and a fourth switching element,
The forward converter includes a third leg having a fifth switching element and a sixth switching element, and a fourth leg having a seventh switching element and an eighth switching element,
The gate drive circuit turns on the first switching element, the second switching element, the fifth switching element, and the sixth switching element at different timings .
The gate driving circuit simultaneously turns on the second switching element and the third switching element after the first dead time period has elapsed after simultaneously turning on the first switching element and the fourth switching element, and A power converter characterized in that the sixth switching element and the seventh switching element are simultaneously turned on after a second dead time period after the switching element and the eighth switching element are simultaneously turned on .

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