JP2023124429A - Power conversion device - Google Patents

Abstract

To provide a power conversion device with a mounted capacitor of small capacity and that can be controlled with ease.SOLUTION: A power conversion device comprises: a primary coil 15 provided between a connection point between a fifth switching element S5 and a sixth switching element S6, and a connection point between a seventh switching element S7 and an eighth switching element S8; a reactor L1 provided between a tap of the primary coil 15 and a connection point between a first capacitor C1 and a second capacitor C2; and an input reactor L2 connected with a connection point between a first switching element S1 and a second switching element S2. One terminal 17p is connected with the input reactor L2, and the other terminal 17n is connected with a connection point between a third switching element S3 and a fourth switching element S4.SELECTED DRAWING: Figure 1

Description

The present invention relates to a power conversion device that transmits power by switching.

Patent Document 1 discloses a boost type PFC (Power Factor Correction) control device that boosts an AC voltage using a boosting coil and a full bridge circuit to generate a DC voltage that is higher than the peak value of the input AC voltage. .

Non-Patent Document 1 discloses a matrix converter circuit using a DAB (Dual Active Bridge) system having full bridge circuits on both sides of an isolation transformer.

The mechanism by which a DC voltage can be generated by boosting an AC voltage in a power converter that uses a boosting coil and a full bridge circuit, and the reason why a capacitor with a large capacity is required will be explained below with reference to FIGS. 11 to 14. do.

FIG. 11 is a diagram showing the configuration of a power conversion device 200 using a boosting coil and a full bridge circuit. As shown in FIG. 11, the power converter 200 includes a first switching arm SA1, a second switching arm SA2, a capacitor arm C, an input reactor L, and a filtering capacitor Cf. The power converter 200 includes a positive terminal T1 and a negative terminal T2 on the input side, and a positive terminal T3 and a negative terminal T4 on the output side.

The first switching arm SA1 comprises a first switching element S1 and a second switching element S2 connected in series. The second switching arm SA2 comprises a third switching element S3 and a fourth switching element S4 connected in series. The first switching arm SA1 and the second switching arm SA2 are connected in parallel. By connecting the first switching arm SA1 and the second switching arm SA2 in parallel in this manner, a full bridge inverter FBI1 is configured.

Capacitor arm C comprises a first capacitor C1 and a second capacitor C2 connected in series. Capacitor arm C is connected in parallel with full-bridge inverter FBI1. That is, the capacitor arm C is connected between the two parallel connection points of the first switching arm SA1 and the second switching arm SA2. An upper parallel connection point and a lower parallel connection point of the first switching arm SA1, the second switching arm SA2, and the capacitor arm C are connected to the positive terminal T3 and the negative terminal T4, respectively. An output load such as a primary winding of a transformer is connected between the positive terminal T3 and the negative terminal T4.

One end of an input reactor L is connected to a connection point between the first switching element S1 and the second switching element S2. The other end of the input reactor L is connected to a filtering capacitor Cf and a positive terminal T1. A filter capacitor Cf and a negative terminal T2 are connected to a connection point between the third switching element S3 and the fourth switching element S4.

An AC voltage Vin is applied between the positive terminal T1 and the negative terminal T2. FIG. 12 shows the operation of each switching element of the power conversion device 200 and the fluctuation of the current _IL flowing through the input reactor L in the state where the AC voltage Vin is applied. In FIG. 12, regarding the ON/OFF operation of each switching element, ON is indicated as a high state, and OFF is indicated as a low state. When the AC voltage Vin is positive, as shown in FIG. 12, the first switching element S1 and the second switching element S2 are switched while the third switching element S3 is fixed at OFF and the fourth switching element S4 is fixed at ON. are turned on alternately, the first switching element S1 and the second switching element S2 are switched on and off. The second switching element S2 is always turned off when the first switching element S1 is on, and the second switching element S2 is always turned on when the first switching element S1 is off. However, when the AC voltage Vin is negative, the third switching element S3 and the fourth switching element S4 are turned on and off while the first switching element S1 is fixed to be off and the second switching element S2 is fixed to be on. alternately. Strictly speaking, the AC voltage Vin is a sine wave, but since the switching period of the first switching element S1 and the second switching element S2 is sufficiently shorter than the period of the AC voltage Vin, the value of the AC voltage Vin in FIG. is constant.

In period (1) shown in FIG. 12, the second switching element S2 and the fourth switching element S4 are on, and the first switching element S1 and the third switching element S3 are off. A current flows through the path indicated by , and the input reactor L is charged.

In period (2) shown in FIG. 12, the first switching element S1 and the fourth switching element S4 are on, and the second switching element S2 and the third switching element S3 are off. , the charged input reactor L is discharged, and the first capacitor C1 and the second capacitor C2 are charged.

In this way, the input reactor L is charged during the period (1) shown in FIG. 12, and the input reactor L is discharged during the period (2) shown in FIG. 12 to charge the first capacitor C1 and the second capacitor C2. is repeated, the input capacitor voltage Vc, which is the sum of the voltage Vc1 of the first capacitor C1 and the voltage Vc2 of the second capacitor C2, can be boosted. This input capacitor voltage Vc becomes the output voltage of the power converter 200 . FIG. 15 shows the results of a simulation performed under the conditions in which the full-bridge inverter FBI1 is operated in this manner. FIG. 15 shows simulated waveforms of the AC input current Iin flowing between the positive terminal T1 and the negative terminal T2, the pre-capacitor current Iac, and the input capacitor voltage Vc. Pre-capacitor current Iac is a current that is full-wave rectified by full-bridge inverter FBI1. As shown in FIG. 15, the power converter 200 can boost the input capacitor voltage Vc. However, the first capacitor C1 and the second capacitor C2 for converting the pre-capacitor current Iac that has been full-wave rectified by the full-bridge inverter FBI1 into direct current require very large capacitances.

JP 2014-99946 A

Shunsuke Takuma, Junichi Ito: "Surge Voltage Reduction Method for DAB Matrix Converter Using Return Current" <URL: http://itohserver01.nagaokaut.ac.jp/itohlab/paper/2021/20210801_%E9%9B%BB %E5%AD%A6%E8%AB%96D/takuma.pdf＞

The step-up PFC controller disclosed in Patent Document 1 can vary the output DC voltage using a step-up coil and a full bridge circuit.

A matrix converter circuit disclosed in Non-Patent Document 1 exists as a power conversion device capable of suppressing an increase in the capacity of a capacitor to be mounted in this manner. However, although the matrix converter circuit disclosed in Non-Patent Document 1 can reduce the capacity of the mounted capacitor, it is difficult to control the current (voltage) and output voltage for the matrix converter to perform ZVS (Zero Voltage Switching). Since the inverter controls the output voltage, the control is complicated.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a power conversion device in which the capacity of a capacitor to be mounted is small and the control is simple.

A power converter according to the present invention includes a first switching arm including a first switching element and a second switching element connected in series, and a second switching arm including a third switching element and a fourth switching element connected in series. a capacitor arm comprising a first capacitor and a second capacitor connected in series; a third switching arm comprising a fifth switching element and a sixth switching element connected in series; a fourth switching arm including a switching element and an eighth switching element; a primary winding magnetically coupled to a secondary winding; a primary winding provided between a switching element and a connection point of the eighth switching element; and a tap of the primary winding provided between a connection point of the first capacitor and the second capacitor. a reactor and an input reactor connected to a connection point between the first switching element and the second switching element, one end of the first switching arm on the side of the first switching element and the one end on the side of a third switching element, one end on the side of the first capacitor of the capacitor arm, one end on the side of the fifth switching element of the third switching arm, and one end on the side of the seventh switching element of the fourth switching arm one end of the first switching arm on the second switching element side; one end of the second switching arm on the fourth switching element side; one end of the capacitor arm on the second capacitor side; By commonly connecting one end of the switching arm on the sixth switching element side and one end of the fourth switching arm on the eighth switching element side, the first switching arm, the second switching arm, and the capacitor arm are connected in common. , the third switching arm and the fourth switching arm are connected in parallel, one of the input terminals is connected to the input reactor, and the connection point of the third switching element and the fourth switching element is connected to the input terminal. The other is connected.

In one aspect of the power converter according to the present invention, the second switching element, the fourth switching element, the sixth switching element, and the eighth switching element are turned on, and the first switching element, the 3 switching elements, a first state in which the fifth switching element and the seventh switching element are turned off, only one of the first switching element and the second switching element is turned on, and the fourth switching element is turned on; a second state in which the switching element, the fifth switching element and the eighth switching element are turned on and the third switching element, the sixth switching element and the seventh switching element are turned off; 1 switching element, the fourth switching element, the fifth switching element and the seventh switching element are turned on, and the second switching element, the third switching element, the sixth switching element and the eighth switching element are turned on. A third state in which elements are off, the second switching element, the fourth switching element, the fifth switching element and the seventh switching element are on, the first switching element, the third switching element a fourth state in which the switching element, the sixth switching element and the eighth switching element are turned off; only one of the first switching element and the second switching element is turned on; and the fourth switching A fifth state in which the element, the sixth switching element and the seventh switching element are turned on, and the third switching element, the fifth switching element and the eighth switching element are turned off, is realized in sequence. may be

In one aspect of the power converter according to the present invention, in the first state, a current circulates between the second capacitor and the reactor, and in the fourth state, between the first capacitor and the reactor. The current may circulate.

In one aspect of the power converter according to the present invention, in the first state, current circulates between the second capacitor and the reactor to form a voltage in the second capacitor, and in the fourth state, , a voltage may be formed in the first capacitor by current circulating between the first capacitor and the reactor.

In one aspect of the power converter according to the present invention, a voltage obtained by rectifying and boosting an AC voltage applied between the input terminals may be applied to the primary winding.

INDUSTRIAL APPLICABILITY The present invention can provide a power converter with a small capacity of a mounted capacitor and simple control.

1 is a circuit diagram of a power conversion system including a power conversion device according to an embodiment of the present invention; FIG. It is a figure which shows the current path in the 1st state of the power converter device of this embodiment. It is a figure which shows the current path in the 2nd state of the power converter device of this embodiment. It is a figure which shows the current path in the 3rd state of the power converter device of this embodiment. It is a figure which shows the current path in the 4th state of the power converter device of this embodiment. It is a figure which shows the current path in the 5th state of the power converter device of this embodiment. It is a figure which shows the result of having simulated in the power converter device of this embodiment by the conditions changed in order of the 1st state, the 2nd state, the 3rd state, the 4th state, and the 5th state. It is a figure explaining the definition of the current and voltage which show the result of a simulation in FIG. It is a figure which shows the result of having simulated the power converter device of this embodiment on the conditions of a low load. It is a figure which shows the result of having simulated the power converter device of this embodiment on the conditions of high load. FIG. 2 is a circuit diagram showing the configuration of a power converter using a boosting coil and a full bridge circuit; It is a figure explaining operation|movement of the power converter device using the coil for boosting and a full-bridge circuit. FIG. 13 is a diagram showing the flow of current in period (1) shown in FIG. 12; FIG. 13 is a diagram showing the current flow during the period (2) shown in FIG. 12; It is a figure which shows the result of having simulated with the power converter device using the coil for boosting, and a full-bridge circuit.

A power converter 10 according to an embodiment of the present invention will be described below with reference to FIGS. 1 to 10. FIG. FIG. 1 shows a circuit diagram of a power conversion system 100 including a power conversion device 10 of this embodiment. As shown in FIG. 1 , the power converter system 100 includes a power converter 10 and a power converter 20 .

The power converter 10 includes a first switching arm 11, a second switching arm 12, a capacitor arm C, a third switching arm 13, a fourth switching arm 14, a primary winding 15, a reactor L1, an input reactor L2, and a filtering capacitor 16. , a positive terminal 17p and a negative terminal 17n.

The first switching arm 11 comprises a first switching element S1 and a second switching element S2 connected in series. The second switching arm 12 comprises a third switching element S3 and a fourth switching element S4 connected in series. The third switching arm 13 comprises a fifth switching element S5 and a sixth switching element S6 connected in series. The fourth switching arm 14 comprises a seventh switching element S7 and an eighth switching element S8 connected in series. Each switching element may be an IGBT (Insulated Gate Bipolar Transistor) or a MOSFET (Metal Oxide Semiconductor Field Effect Transistor). When IGBTs are used as switching elements, connecting two IGBTs in series means that the emitter terminal of one IGBT is connected to the collector terminal of the other IGBT. When MOSFETs are used as switching elements, connecting two MOSFETs in series means that the source terminal of one MOSFET is connected to the drain terminal of the other MOSFET. Each switching element also includes a diode. When an IGBT is used as the switching element, the anode terminal is connected to the emitter terminal, and the cathode terminal is connected to the collector terminal. When a MOSFET is used as the switching element, the anode terminal is connected to the source terminal, and the cathode terminal is connected to the drain terminal.

The first switching arm 11 and the second switching arm 12 are connected in parallel. That is, the terminal of the first switching element S1 opposite to the second switching element S2 (upper side in FIG. 1) and the terminal of the third switching element S3 opposite to the fourth switching element S4 (upper side in FIG. 1). are connected to the terminal of the second switching element S2 opposite to the first switching element S1 (lower side in FIG. 1) and the terminal of the fourth switching element S4 opposite to the third switching element S3 (lower side in FIG. 1). ) are connected. By connecting the first switching arm 11 and the second switching arm 12 in parallel in this manner, the first full bridge inverter FBI1 is configured.

The third switching arm 13 and the fourth switching arm 14 are connected in parallel. That is, the terminal (upper terminal) of the fifth switching element S5 opposite to the sixth switching element S6 (upper terminal) is connected to the terminal (upper terminal) of the seventh switching element S7 opposite to the eighth switching element S8. and the terminal (lower terminal) of the sixth switching element S6 opposite to the fifth switching element S5 (lower terminal) and the terminal (lower terminal) of the eighth switching element S8 opposite to the seventh switching element S7. is connected. By connecting the third switching arm 13 and the fourth switching arm 14 in parallel in this manner, the second full bridge inverter FBI2 is configured.

Capacitor arm C comprises a first capacitor C1 and a second capacitor C2 connected in series. The capacitor arm C is connected in parallel with the first full bridge inverter FBI1 and the second full bridge inverter FBI2. That is, the capacitor arm C is connected between the two parallel connection points of the first switching arm 11 and the second switching arm 12, and the two parallel connections of the third switching arm 13 and the fourth switching arm 14. points are also connected.

One end of an input reactor L2 is connected to a connection point between the first switching element S1 and the second switching element S2. A filtering capacitor 16 and a positive terminal 17p are connected to the other end of the input reactor L2. A filter capacitor 16 and a negative terminal 17n are connected to a connection point between the third switching element S3 and the fourth switching element S4.

A primary winding 15 is connected between a connection point between the fifth switching element S5 and the sixth switching element S6 and a connection point between the seventh switching element S7 and the eighth switching element S8. A reactor L1 is connected between a tap provided at an intermediate point of the lead wire forming the primary winding 15 and a connection point between the first capacitor C1 and the second capacitor C2. The tap may be a center tap at the midpoint of the conductors that make up the primary winding 15 .

The use of IGBT, MOSFET, etc. for each switching element, the inclusion of a diode in each switching element, and the definition of series connection of switching elements are the same for the switching elements described below.

The power conversion device 20 includes a switching arm 21, a switching arm 22, a capacitor C3, a secondary winding 23, a positive terminal 24p and a negative terminal 24n.

The switching arm 21 comprises a ninth switching element S9 and a tenth switching element S10 connected in series. The switching arm 22 comprises an eleventh switching element S11 and a twelfth switching element S12 connected in series. Switching arm 21 and switching arm 22 are connected in parallel. That is, the terminal of the ninth switching element S9 opposite to the tenth switching element S10 (upper side in FIG. 1) and the terminal of the eleventh switching element S11 opposite to the twelfth switching element S12 (upper side in FIG. 1). are connected to the terminal of the tenth switching element S10 opposite to the ninth switching element S9 (lower side in FIG. 1) and the terminal of the 12th switching element S12 opposite to the eleventh switching element S11 (lower side in FIG. 1). ) are connected. By connecting the switching arm 21 and the switching arm 22 in parallel in this manner, the third full bridge inverter FBI3 is configured.

A secondary winding 23 is connected between a connection point between the ninth switching element S9 and the tenth switching element S10 and a connection point between the eleventh switching element S11 and the twelfth switching element S12. Secondary winding 23 is coupled to primary winding 15 and together with primary winding 15 forms a transformer.

A capacitor C3 is connected in parallel with the third full bridge inverter FBI3. That is, capacitor C3 is connected between the two parallel connection points of switching arm 21 and switching arm 22 . A parallel connection point on one side (upper side in FIG. 1) of the switching arm 21, the switching arm 22 and the capacitor C3 is connected to the positive terminal 24p, and the opposite side of the switching arm 21, the switching arm 22 and the capacitor C3 (lower side in FIG. 1) side) is connected to the negative terminal 24n.

An AC voltage Vac is applied between the positive terminal 17p and the negative terminal 17n of the power converter 10 . A load is connected between the positive terminal 24p and the negative terminal 24n of the power converter 20 . The configuration of the power conversion device 20 is not particularly limited, and is a circuit that includes a secondary winding 23 magnetically coupled to the primary winding 15 of the power conversion device 10 and supplies power to a load. I wish I had.

In the power electronics device 10, the states change in order of the first state, the second state, the third state, the fourth state, and the fifth state described below as time elapses. In the power electronics device 10, the process of switching from the first state to the fifth state is repeated in this order. 2 to 6 show states of current flowing through the power conversion device 10 in the first state, second state, third state, fourth state, and fifth state, respectively.

7 shows current Iac before capacitor, input capacitor voltage Vc, transformer current Itr and The result of simulating the transformer voltage Vtr is shown. The first state is entered at the timing (1) shown in FIG. 7, the second state is during the period (2) shown in FIG. 7, and the third state is during the period (3) shown in FIG. The period (4) shown in FIG. 7 is the fourth state, and the period (5) shown in FIG. 7 is the fifth state. FIG. 7 also shows the ON and OFF states of eight switching elements from the first switching element S1 to the eighth switching element S8. In FIG. 7, when the on/off signal of each switching element is in a high state, it is on, and when it is in a low state, it is off.

Definitions of the pre-capacitor current Iac, the input capacitor voltage Vc, the transformer current Itr, and the transformer voltage Vtr whose simulation waveforms are shown in FIG. 7 will now be described with reference to FIG. Pre-capacitor current Iac is a current that flows from full-bridge inverter FBI1 to capacitor arm C and second full-bridge inverter FBI2. The input capacitor voltage Vc is the sum of the voltage Vc1 of the first capacitor C1 and the voltage Vc2 of the second capacitor C2. A transformer current Itr is a current that flows through the primary winding 15 from one end to the other end of the primary winding 15 , and a transformer voltage Vtr is a voltage applied across the primary winding 15 .

The first state means that the second switching element S2, the fourth switching element S4, the sixth switching element S6 and the eighth switching element S8 are turned on, and the first switching element S1, the third switching element S3 and the fifth switching element S1 are turned on. This is a state in which the switching element S5 and the seventh switching element S7 are turned off.

The flow of current in the power converter 10 in the first state is indicated by dashed arrows in FIG. In the first state, current flows through the second switching element S2 and the fourth switching element S4 in the first full bridge inverter FBI1, thereby charging the input reactor L2. In the second full-bridge inverter FBI2, the sixth switching element S6 and the eighth switching element S8 are turned on, and both ends of the primary winding 15 are shorted, so the transformer voltage Vtr becomes zero. Therefore, a current flows from the second capacitor C2 via the reactor L1, branches at the tap of the primary winding 15, and returns to the second capacitor C2 via the sixth switching element S6 or the eighth switching element S8. That is, current circulates between second capacitor C2, reactor L1 and primary winding 15, and voltage is applied to second capacitor C2.

The second state means that only one of the first switching element S1 and the second switching element S2 is turned on, and the fourth switching element S4, the fifth switching element S5 and the eighth switching element S8 are turned on. , and the third switching element S3, the sixth switching element S6, and the seventh switching element S7 are turned off.

FIG. 3 shows the flow of current in the power conversion device 10 in the second state in which the first switching element S1 is turned on and the second switching element S2 is turned off. In the second state, current flows through the first switching element S1 and the fourth switching element S4 in the first full-bridge inverter FBI1, thereby discharging the input reactor L2 and charging the first capacitor C1 and the second capacitor C2. A transformer voltage Vtr is applied across the primary winding 15 in the second full-bridge inverter FBI2, and a transformer current Itr flows through the primary winding 15. FIG. In this case, in the capacitor arm C, the charging current flowing in from the input reactor L2 and the discharging current flowing out to the primary winding 15 cancel each other out, and the current flows directly from the input reactor L2 to the primary winding 15. Therefore, in the second state, as shown in FIG. 7, the input capacitor voltage Vc increases, power is supplied to the load, and the transformer current Itr increases.

In the second state, the first switching element S1 may be turned off and the second switching element S2 may be turned on. In this case, the transformer voltage Vtr is applied across the primary winding 15 by the first capacitor C1 and the second capacitor C2, as in the fifth state described later, so that the transformer current Itr flows through the primary winding 15 .

The third state means that the first switching element S1, the fourth switching element S4, the fifth switching element S5 and the seventh switching element S7 are turned on, and the second switching element S2, the third switching element S3 and the sixth switching element S3 are turned on. This is a state in which the switching element S6 and the eighth switching element S8 are turned off.

The flow of current in the power converter 10 in the third state is indicated by dashed arrows in FIG. In the third state, current flows through the first switching element S1 and the fourth switching element S4 in the first full-bridge inverter FBI1, thereby discharging the input reactor L2 and charging the first capacitor C1 and the second capacitor C2. . In the second full-bridge inverter FBI2, both ends of the primary winding 15 are short-circuited, so the transformer voltage Vtr becomes zero. Therefore, current flows from the first capacitor C1 via the sixth switching element S6 or the eighth switching element S8, joins at the tap of the primary winding 15, and returns to the first capacitor C1 via the reactor L1. That is, current circulates between first capacitor C1, reactor L1 and primary winding 15. FIG. In the third state, the discharge current of input reactor L2 flows into first capacitor C1 and second capacitor C2, so that input capacitor voltage Vc increases as shown in FIG.

The fourth state means that the second switching element S2, the fourth switching element S4, the fifth switching element S5, and the seventh switching element S7 are turned on, and the first switching element S1, the third switching element S3, and the sixth switching element S7 are turned on. This is a state in which the switching element S6 and the eighth switching element S8 are turned off.

The flow of current in the power converter 10 in the fourth state is indicated by dashed arrows in FIG. In the fourth state, as shown in FIG. 5, current flows through the first switching element S1 and the fourth switching element S4 in the first full bridge inverter FBI1, thereby charging the input reactor L2. In the second full-bridge inverter FBI2, the fifth switching element S5 and the seventh switching element S7 are turned on, and the current flows between the first capacitor C1, the reactor L1 and the primary winding 15 as in the third state. , forming a voltage across the first capacitor C1.

In the fifth state, only one of the first switching element S1 and the second switching element S2 is turned on, and the fourth switching element S4, the sixth switching element S6 and the seventh switching element S7 are turned on. , and the third switching element S3, the fifth switching element S5 and the eighth switching element S8 are turned off.

FIG. 6 shows the flow of current in the power conversion device 10 in the fifth state in which the first switching element S1 is turned off and the second switching element S2 is turned on. In the fifth state, current flows through the second switching element S2 and the fourth switching element S4 in the first full bridge inverter FBI1, thereby charging the input reactor L2. In the second full bridge inverter FBI2, a current path is formed through the sixth switching element S6 and the seventh switching element S7. As a result, the transformer voltage Vtr is applied across the primary winding 15 from the first capacitor C1 and the second capacitor C2, and the transformer current Itr flows through the primary winding 15 . Therefore, as shown in FIG. 7, the input capacitor voltage Vc drops.

In the fifth state, the first switching element S1 may be on and the second switching element S2 may be off. In this case, similarly to the second state in which the first switching element S1 is turned on and the second switching element S2 is turned off, in the capacitor arm C, the charging current flowing in from the input reactor L2 and the discharging current flowing out to the primary winding 15 cancel each other out, and the current flows directly from the input reactor L2 to the primary winding 15 .

The five states from the first state to the fifth state are divided into three periods: power transfer period (second state and fifth state), voltage control period (third state) and circulation period (first state and fourth state). It can be categorized into periods. The power transmission period is a period during which the transformer voltage Vtr is applied to the primary winding 15 , the transformer current Itr flows, and power is transmitted to and from the power converter 20 . During the voltage control period, the capacitor arm C is charged by the discharge of the input reactor L2, and the input capacitor voltage Vc is controlled. During the circulation period, current is circulated between the first capacitor C1 or the second capacitor C2 and the primary winding 15 to maintain the input capacitor voltage Vc.

Thus, in the power converter 10, the frequency of the power transmission period is increased when the power supply to the transformer is desired to be increased, and the frequency of the power transmission period is decreased when the power supply to the transformer is desired to be decreased. For example, when the load is low, a small amount of power may be supplied to the transformer, so the operating frequency during the power transmission period is reduced. In the case of a high load, it is necessary to increase the power supply to the transformer, so the operating frequency during the power transmission period is increased.

FIG. 9 shows the results of simulation under low-load conditions, and FIG. 10 shows the results of simulation under high-load conditions for the current Iac before the capacitor, the input capacitor voltage Vc, the transformer current Itr, and the transformer voltage Vtr. As shown in FIG. 9, under low load conditions, the frequency of operation during the power transmission period is low, and the voltages of the first capacitor C1 and the second capacitor C2 are controlled by the voltage control period and the circulation period. Then, as shown in FIG. 10, under high load conditions, the power supply to the transformer is increased by increasing the operation frequency during the power transmission period.

During the power transmission period, the power conversion device 10 can flow current directly from the input reactor L2 to the primary winding 15 instead of supplying power from the first capacitor C1 and the second capacitor C2 to the transformer. , the amount of charging and discharging of the first capacitor C1 and the second capacitor C2 can be reduced. In addition, since the power conversion device 10 can control the input capacitor voltage Vc by controlling the current Iac before the capacitor by increasing or decreasing the operation frequency during the power transmission period, the charge/discharge amount of the first capacitor C1 and the second capacitor C2 is can be reduced. Therefore, in the power conversion device 10, the capacitance of the mounted capacitor can be reduced. In addition, with such simple control, the power converter 10 can apply to the primary winding 15 a voltage obtained by rectifying and boosting the AC voltage applied between the positive terminal 17p and the negative terminal 17n. .

10 power converter, 11 first switching arm, 12 second switching arm, 13 third switching arm, 14 fourth switching arm, 15 primary winding, 16 filter capacitor, 17p positive terminal, 17n negative terminal, 20 power conversion device, 21, 22 switching arm, 23 secondary winding, 24p positive terminal, 24n negative terminal, 100 power conversion system, 200 power conversion device, C capacitor arm, C1 first capacitor, C2 second capacitor, C3 capacitor, FBI1 second 1 full bridge inverter, FBI2 second full bridge inverter, FBI3 third full bridge inverter, L1 reactor, L2 input reactor, S1 first switching element, S2 second switching element, S3 third switching element, S4 fourth switching element, S5 fifth switching element, S6 sixth switching element, S7 seventh switching element, S8 eighth switching element, S9 ninth switching element, S10 tenth switching element, S11 eleventh switching element, S12 twelfth switching element.

Claims (5)

a first switching arm comprising a first switching element and a second switching element connected in series;
a second switching arm comprising a third switching element and a fourth switching element connected in series;
a capacitor arm comprising a first capacitor and a second capacitor connected in series;
a third switching arm comprising a fifth switching element and a sixth switching element connected in series;
a fourth switching arm comprising a seventh switching element and an eighth switching element connected in series;
A primary winding magnetically coupled to the secondary winding, between a connection point of the fifth switching element and the sixth switching element and a connection point of the seventh switching element and the eighth switching element a primary winding provided;
a reactor provided between a tap of the primary winding and a connection point between the first capacitor and the second capacitor;
an input reactor connected to a connection point between the first switching element and the second switching element;
One end of the first switching arm on the side of the first switching element, one end of the second switching arm on the side of the third switching element, one end of the capacitor arm on the side of the first capacitor, the third switching arm of the third switching arm. 5 switching element side and one end of the fourth switching arm on the seventh switching element side are connected in common, and one end of the first switching arm on the second switching element side and the first switching element side of the second switching arm are connected in common. One end on the 4 switching element side, one end on the second capacitor side of the capacitor arm, one end on the sixth switching element side of the third switching arm, and one end on the eighth switching element side of the fourth switching arm are common. By connecting to, the first switching arm, the second switching arm, the capacitor arm, the third switching arm and the fourth switching arm are connected in parallel,
A power converter, wherein one of input terminals is connected to the input reactor, and the other of the input terminals is connected to a connection point between the third switching element and the fourth switching element. The power converter according to claim 1,
The second switching element, the fourth switching element, the sixth switching element and the eighth switching element are turned on, and the first switching element, the third switching element, the fifth switching element and the third switching element are switched on. 7 a first state in which the switching element is off;
Only one of the first switching element and the second switching element is turned on, the fourth switching element, the fifth switching element and the eighth switching element are turned on, and the third switching element is turned on. a second state in which the element, the sixth switching element and the seventh switching element are turned off;
The first switching element, the fourth switching element, the fifth switching element and the seventh switching element are turned on, and the second switching element, the third switching element, the sixth switching element and the third switching element are turned on. 8 a third state in which the switching element is off;
The second switching element, the fourth switching element, the fifth switching element and the seventh switching element are turned on, and the first switching element, the third switching element, the sixth switching element and the third switching element are turned on. 8 a fourth state in which the switching element is off;
Only one of the first switching element and the second switching element is turned on, the fourth switching element, the sixth switching element and the seventh switching element are turned on, and the third switching element is turned on. A power converter, wherein a fifth state in which an element, the fifth switching element and the eighth switching element are turned off is realized in order. The power converter according to claim 2,
In the second state or the fifth state, when the first switching element is turned on and the second switching element is turned off, the charging current flowing from the input reactor to the capacitor arm and the primary winding from the capacitor arm A power conversion device characterized in that a current flows directly from the input reactor to the primary winding, canceling out a discharge current that flows out to a line. The power converter according to claim 2 or 3,
In the first state, current circulates between the second capacitor and the reactor,
A power converter, wherein current circulates between the first capacitor and the reactor in the fourth state. The power converter according to any one of claims 1 to 4,
A power converter, wherein a voltage obtained by rectifying and boosting an AC voltage applied between said input terminals can be applied to said primary winding.