JP2016208693A - Power conversion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the number of semiconductor devices on a power conversion device to which an isolation transformer is mounted.SOLUTION: The power conversion device includes: an AC side first electric circuit running from one input terminal of an AC side to a primary side neutral point of an isolation transformer; an AC side second electric circuit running from the other input terminal to both terminal parts of a primary side winding through a common electric circuit by being branched at a branch point to two electric circuits; a reactor interposed by at least one of the AC side first electric circuit and the common electric circuit; a first switch and a second switch, having bidirectionality, bidirectionally cutting off power supply in an off state, inserted respectively between the branch point and one end and the other end of the primary side winding; a DC side first electric circuit reaching one output terminal by being mutually connected to a negative electrode of each rectifier whose positive electrode is connected to both terminal parts of the secondary side winding; a DC side second electric circuit reaching from the secondary side neutral point to the other output terminals; a capacitor provided between two output terminals; a control part for controlling each switch.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power converter that converts alternating current to direct current or converts direct current to alternating current.

FIGS. 17 to 21 are circuit diagrams each showing a conventional typical isolated DC power supply (AC to DC power converter).
First, the insulation type DC power source shown in FIG. 17 includes an insulation transformer 201, a diode bridge rectifier circuit 202, and a boost chopper circuit 203. This circuit is widely used because the number of semiconductor devices used (5 diodes and 6 switches in total) is small and the control is simple. In addition, since it is a known circuit and the circuit operation is obvious from the circuit diagram and symbol, detailed description is omitted here (the same applies hereinafter).

  The insulated DC power source shown in FIG. 18 is a circuit widely used for an AC adapter or the like, and includes a rectifier circuit 202, a boost chopper circuit 203, and an insulated DC / DC converter 204. In this circuit, the number of semiconductor devices used (a total of 10 diodes and 3 switches) is larger than that of the circuit of FIG.

  The insulated DC power source shown in FIG. 19 performs rectification and power factor control by replacing the rectifier circuit 202 and the boost chopper circuit 203 in FIG. 18 with a bipolar boost chopper circuit 205. In this case, the number of semiconductor devices (a total of eight diodes and four switches) is smaller than that of the circuit of FIG. 18, but larger than that of the circuit of FIG.

The insulated DC power source shown in FIG. 20 includes a rectifier circuit 206 and an insulated DC / DC converter 207 (see, for example, FIG. 5 of Patent Document 1). In this case, the number of semiconductor devices used is eight (a total of eight diodes and two switches).
The insulated DC power source shown in FIG. 21 includes a rectifier circuit 208 and an insulated DC / DC converter 209 (see, for example, FIG. 2 of Patent Document 1). In this case, the number of semiconductor devices used is eight (a total of eight diodes and four switches).

Japanese Patent No. 3216736

  In the conventional insulation type DC power supply (power conversion device) as described above, first, the circuit of FIG. 17 has the smallest number of semiconductor devices, but the insulation transformer 201 is a low-frequency transformer used at a commercial frequency. It becomes. For this reason, the size and weight of the insulating transformer 201 are larger than those of the high-frequency transformer. In addition, the exciting current of the insulating transformer 201 is large, so that the efficiency at no load or light load is poor.

On the other hand, all of the insulated DC power supplies shown in FIGS. 18 to 21 use eight or more semiconductor devices. Looking at the section from the AC side to the high frequency insulation transformer, it is 6 or more. Semiconductor devices have power loss due to on-resistance and power loss due to switching.
In the case of a switch, a space for installing a peripheral circuit such as a snubber circuit that absorbs a turn-off surge caused by parasitic inductance is required in addition to the drive circuit. In addition, a radiator is required to cool the switch itself, but its size is larger than the switch. Therefore, the more semiconductor devices, the more difficult it is to reduce the size of the entire apparatus.

  In view of such conventional problems, an object of the present invention is to reduce the number of semiconductor devices in a power converter equipped with a high-frequency insulating transformer and having a function of performing power conversion between AC and DC. To do.

(Conversion from AC to DC)
The power converter of the present invention is a power converter that performs power conversion from alternating current to direct current, and has a primary side neutral point and a secondary side neutral point in each of the primary side winding and the secondary side winding. Branching into two electric circuits at a branching point via an insulating transformer having a point, an AC side first electric circuit from one input terminal on the AC side to the primary neutral point, and a common electric circuit from the other input terminal on the AC side The AC side second electric circuit reaching both ends of the primary side winding, the reactor inserted in at least one of the AC side first electric circuit and the common electric circuit, and bidirectionally energizable, and In the switch-off state, the current is cut off in both directions, and the first switch inserted between the branch point and one end of the primary side winding can be energized in both directions, and the switch is turned off. In this state, power is cut off in both directions, and the branch point and the other end of the primary winding are A second switch inserted into the first winding, a first rectifying element having a positive electrode connected to one end of the secondary winding, and a second rectifying element having a positive electrode connected to the other end of the secondary winding A first DC circuit that connects the negative electrodes of the first rectifying element and the second rectifying element to each other and reaches one output terminal on the DC side, and the other on the DC side from the secondary neutral point DC-side second electric circuit that reaches the output terminal, a capacitor provided between the one output terminal and the other output terminal, both the first switch and the second switch are on, and one is off And a control unit that performs a switching operation so that a process in which both are turned on and the other is turned off is repeated.

(Both directions between AC and DC)
The present invention is also a power conversion device that performs bidirectional power conversion between alternating current and direct current, the primary side of each of the primary side winding on the alternating current side and the secondary side winding on the direct current side. An insulation transformer having a neutral point and a secondary side neutral point, an AC side first electric circuit from one port on the AC side to the primary side neutral point, and a common circuit from the other port on the AC side An AC side second electric circuit that branches into two electric circuits at the branch point and reaches both ends of the primary side winding; a reactor inserted in at least one of the AC side first electric circuit and the common electric circuit; It can be energized, and can be energized in both directions with the first switch inserted between the branch point and one end of the primary winding when the switch is off. In the switch-off state, the power supply is cut off in both directions, and the branch point and the primary A second switch inserted between the other end of the winding, a third switch provided in parallel with a rectifier having a positive electrode connected to one end of the secondary winding, and the secondary side A fourth switch provided in parallel with a rectifier having a positive electrode connected to the other end of the winding; and a rectifier of the third switch and a negative electrode of the rectifier of the fourth switch DC side first electric circuit reaching one port on the side, DC side second electric circuit extending from the secondary side neutral point to the other port on the DC side, one port on the DC side and the other on the DC side And a capacitor provided between the first switch and the second switch, both of the first switch and the second switch are on, one is off, both are on, and the other is off. Switching operation is repeated, and conversely, from DC to AC At the time of conversion, a switching operation for alternately turning on the third switch and the fourth switch is performed, and correspondingly, a switching operation for alternately turning on the first switch and the second switch. And a control unit that performs the operation.

(Conversion from DC to AC)
In addition, the present invention is a power conversion device that performs power conversion from direct current to alternating current, and includes a primary-side neutral point and 2 for each of an alternating-current primary winding and a direct-current secondary winding. An isolation transformer having a secondary neutral point, a first AC circuit on the AC side from one output end on the AC side to the primary neutral point, and a branch point via the common circuit from the other output terminal on the AC side Bi-directionally energized with a second AC circuit that branches into two electric circuits and reaches both ends of the primary winding, a reactor that is inserted into at least one of the first AC circuit and the common circuit And in a switch-off state, the current is cut off in both directions, and the first switch inserted between the branch point and one end of the primary winding can be turned on in both directions. In the switch-off state, the power supply is cut off in both directions, and the branch point and the primary winding A second switch inserted between the second side winding, one end connected to one end of the secondary winding, and one end connected to the other end of the secondary winding. The fourth switch, the other end of the third switch and the other end of the fourth switch are connected to each other, and the first DC circuit that reaches one input terminal on the DC side, and the secondary neutral point A DC side second electric circuit extending from the DC side to the other input terminal on the DC side, and a switching operation for alternately turning on the third switch and the fourth switch, and correspondingly, the first switch And a control unit for performing a switching operation for alternately turning on the second switch.

  ADVANTAGE OF THE INVENTION According to this invention, the number of semiconductor devices from an alternating current side to an insulation transformer can be reduced in the power converter device which mounts a high frequency insulation transformer and was equipped with the function to perform the power conversion between alternating current and direct current. .

It is a circuit diagram of the power converter device which makes an insulated rectifier converter the principal part as a 1st embodiment. It is a control block diagram until it calculates | requires the reactor electric current command value Ic * which should be sent to a reactor. It is a control block diagram which calculates | requires the reference wave Vref. It is a control block diagram which shows the PWM gate pulse arithmetic logic of an insulation rectifier converter. It is a control block diagram which shows the PWM gate pulse arithmetic logic of an insulation rectifier converter. It is a control block diagram of a step-down chopper. The input AC voltage Va, the gate drive pulses Gate1, Gate2, Gate3, Gate4, the reactor current command value Ic *, and the detected value Ic of the insulating rectifier converter are shown in a part of the interval in which the sign of the AC voltage transitions from positive to negative. It is a waveform diagram. It is an input-output waveform diagram in an insulated rectifier converter and a step-down chopper. It is a circuit diagram of the power converter device which has an insulated bidirectional converter as a principal part as 2nd Embodiment. It is a control block diagram for calculating | requiring a reactor current command value and a reference wave. It is a control block diagram which shows a PWM gate pulse calculation logic. It is a control block diagram which calculates | requires the electric current command value of the reactor in a bidirectional chopper. It is a control block diagram which shows a PWM gate pulse calculation logic. It is a wave form diagram which shows the gate drive pulse of an insulated bidirectional | two-way converter, a voltage, and a current waveform. It is an input-output waveform diagram in the reverse conversion of an insulated bidirectional converter and a bidirectional chopper. It is a wave form diagram when transfering from forward conversion to reverse conversion. It is a circuit diagram which shows the 1st example of the conventional typical insulation type DC power supply. It is a circuit diagram which shows the 2nd example of the conventional typical insulation type DC power supply. It is a circuit diagram which shows the 3rd example of the conventional typical insulation type DC power supply. It is a circuit diagram which shows the 4th example of the conventional typical insulation type DC power supply. It is a circuit diagram which shows the 5th example of the conventional typical insulation type DC power supply.

[Summary of Embodiment]
The gist of the embodiment of the present invention includes at least the following.

  (1) A power converter that performs power conversion from alternating current to direct current, having an insulation transformer having a primary side neutral point and a secondary side neutral point in each of the primary side winding and the secondary side winding The first AC circuit on the AC side extending from one input end on the AC side to the primary neutral point, and the second input circuit branching from the other input end on the AC side through the common circuit to the second circuit at the branch point. In an AC side second electric circuit reaching both ends of the side winding, a reactor inserted in at least one of the AC side first electric circuit and the common electric circuit, bidirectionally energizable, and in a switch-off state A first switch that cuts off electricity in both directions and is inserted between the branch point and one end of the primary winding, and can be energized in both directions, and is bidirectional when switched off. The second is inserted between the branch point and the other end of the primary winding. A first rectifier element having a positive electrode connected to one end of the secondary winding, a second rectifier element having a positive electrode connected to the other end of the secondary winding, and the first rectifier A first DC circuit that connects one of the negative electrodes of the element and the second rectifying element to one output terminal on the DC side, and a DC that extends from the secondary neutral point to the other output terminal on the DC side Side second electric circuit, a capacitor provided between the one output terminal and the other output terminal, both the first switch and the second switch are on, one is off, both are on, the other And a control unit that performs a switching operation so that the process of turning off is repeated.

In the power conversion device configured as described in (1) above, energy is accumulated in the reactor while both the first switch and the second switch are on. When either the first switch or the second switch is turned off, energy is released to the secondary side of the insulating transformer, and the reactor is reset by the load voltage. The voltage of the secondary winding is rectified by the first rectifying element and the second rectifying element, and is output after being smoothed by the capacitor. Since the first switch and the second switch have bidirectionality, such a function as a current type converter can be realized regardless of the sign (direction) of the AC voltage / AC current.
Therefore, a low-frequency alternating current such as a commercial frequency can be transformed with an insulating transformer by high-frequency switching without being rectified, and rectified on the secondary side to be a direct-current output. According to such a configuration, conversion from the AC input to the isolation transformer can be realized by switching only the first switch and the second switch.
In this way, it is possible to obtain an AC to DC power conversion device that has an insulating transformer and suppresses the total number of switches.

(2) Further, in the power conversion device of (1), each of the first switch and the second switch includes a pair of semiconductor switches in which a diode is connected in parallel to a switch element that can be energized bidirectionally. It may be a switch series body in which the diodes are connected in series so as to have reverse polarity.
In this case, desired characteristics can be easily obtained by the series body of a pair of switch elements. Examples of such switch elements include MOSFETs (Metal-Oxide-Semiconductor Field Effect Transistors) including body diodes, IGBTs (Insulated Gate Bipolar Transistors) connected with anti-parallel diodes, and Schottky barrier diodes connected in anti-parallel. A SiC-MOSFET can be used.

(3) In the power converter of (2) above, the control unit switches one of the pair of semiconductor switches to a conductive state and switches the other according to the sign of the input AC voltage. You may make it operate.
In this case, among the total of four semiconductor switches of the first switch and the second switch, there are two semiconductor switches that perform switching operation at a high frequency during a period in which the sign of the AC voltage is positive or negative, thereby reducing the switching loss. be able to. In order to bring the semiconductor switch that is not to be switched into a conducting state, the switch element may be kept on or the switch element may be kept off and an antiparallel diode may be used as the energization path.

  (4) Moreover, it is a power converter device which performs power conversion bidirectionally between alternating current and direct current, and is in the primary side in each of the primary side winding on the alternating current side and the secondary side winding on the direct current side. An isolation transformer having a neutral point and a secondary neutral point, an AC side first electric circuit from one port on the AC side to the primary side neutral point, and a branch from the other port on the AC side via a common circuit Bi-directionally energized bi-directionally to the two ends of the primary winding and to both ends of the primary winding, a reactor inserted in at least one of the AC side first electric circuit and the common electric circuit, bidirectionally In a state where the switch is turned off, the current can be cut off in both directions, and the first switch inserted between the branch point and one end of the primary winding can be turned on in both directions. In the switch-off state, power is cut off in both directions, and the branch point and the primary winding A second switch inserted between the other end of the second winding, a third switch provided in parallel with a rectifier element having a positive electrode connected to one end of the secondary winding, and the secondary winding. A fourth switch provided in parallel with a rectifier having a positive electrode connected to the other end of each of the first switch, and the negative electrodes of the rectifier of the third switch and the rectifier of the fourth switch are connected to each other, DC side first electric circuit reaching one port, DC side second electric circuit extending from the secondary side neutral point to the other port on the DC side, one port on the DC side and the other port on the DC side During the conversion from AC to DC, a process is repeated in which both the first switch and the second switch are on, one is off, both are on, and the other is off. Reverse switching from direct current to alternating current Performs a switching operation for alternately turning on the third switch and the fourth switch, and correspondingly performs a switching operation for alternately turning on the first switch and the second switch. And a control unit to be performed.

  In the power conversion device configured as in (4) above, energy is accumulated in the reactor during the period in which both the first switch and the second switch are on during conversion from AC to DC. When either the first switch or the second switch is turned off, energy is released to the secondary side of the insulating transformer, and the reactor is reset by the load voltage. The voltage of the secondary winding is rectified by the first rectifying element and the second rectifying element, and is output after being smoothed by the capacitor. Since the first switch and the second switch have bidirectionality, such a function as a current type converter can be realized regardless of the sign (direction) of the AC voltage / AC current.

  Therefore, a low-frequency alternating current such as a commercial frequency can be transformed with an insulating transformer by high-frequency switching without being rectified, and rectified on the secondary side to be a direct-current output. According to such a configuration, conversion from the AC input to the isolation transformer can be realized by switching only the first switch and the second switch.

On the other hand, when converting from direct current to alternating current, the third switch and the fourth switch are alternately turned on so that the secondary side (DC side) circuit of the isolation transformer can be operated as a push-pull converter. . On the primary side of the isolation transformer, alternating current is generated by turning on one of the first switch and the second switch in correspondence with the on state of either the third switch or the fourth switch. be able to.
Thus, it is possible to obtain a bidirectional power conversion device that has an insulating transformer and suppresses the total number of switches.

(5) Moreover, in the power converter of (4), each of the first switch and the second switch includes a pair of semiconductor switches in which a diode is connected in parallel to a switch element that can be energized bidirectionally. It may be a switch series body in which the diodes are connected in series so as to have reverse polarity.
In this case, desired characteristics can be easily obtained by the series body of a pair of switch elements. As such a switch element, for example, a MOSFET including a body diode, an IGBT connected with an antiparallel diode, or an SiC-MOSFET connected with a Schottky barrier diode in antiparallel can be used.

(6) Further, in the power conversion device of (5), at the time of conversion from direct current to alternating current, the control unit corresponds to the ON state of one of the third switch and the fourth switch, and By turning on one of the first switch and the second switch, the sign of the AC voltage can be positive, and by turning the other switch on, the sign of the AC voltage can be negative.
In this case, it is possible to easily generate a desired AC voltage by performing pulse width modulation control on the ON time of each switch.

  (7) In addition, as a power conversion device that performs power conversion from direct current to alternating current, the primary side neutral point and the secondary side are respectively provided to the primary side winding on the AC side and the secondary side winding on the DC side. An isolation transformer having a neutral point, an AC side first electric circuit from one output end on the AC side to the primary side neutral point, and two electric circuits at a branch point from the other output end on the AC side via a common circuit An AC side second electric circuit that branches to both ends of the primary side winding, a reactor inserted in at least one of the AC side first electric circuit and the common electric circuit, and can be energized in both directions. And in the switch-off state, the current supply is cut off in both directions, the first switch inserted between the branch point and one end of the primary winding, and can be supplied in both directions, and In the switch-off state, power is cut off in both directions, and the branch point and the other end of the primary winding A second switch inserted between the second switch, one end connected to one end of the secondary winding, and one end connected to the other end of the secondary winding. 4 switches, the other end of the third switch and the other end of the fourth switch are connected to each other, the DC side first electric circuit leading to one input end on the DC side, and the secondary side neutral point to DC A DC side second electric circuit that reaches the other input terminal on the side, and a switching operation that alternately turns on the third switch and the fourth switch, and correspondingly, the first switch and the And a control unit that performs a switching operation to alternately turn on the second switch.

In the power conversion device configured as described in (7) above, the secondary (DC side) circuit of the isolation transformer operates as a push-pull converter by alternately turning on the third switch and the fourth switch. Can be made. On the primary side of the isolation transformer, alternating current is generated by turning on one of the first switch and the second switch in correspondence with the on state of either the third switch or the fourth switch. be able to.
According to such a configuration, conversion from the insulating transformer to the AC side can be realized by switching only the first switch and the second switch.
In this way, it is possible to obtain a direct-to-alternate power conversion device that has an insulating transformer and suppresses the total number of switches.

(8) Moreover, in any one of (1) to (7), the control unit detects a voltage sensor that detects an AC voltage, a voltage sensor that detects a DC voltage, and a current sensor that detects a current flowing through the reactor. The control unit may perform switching of the first switch and the second switch so that an alternating current synchronized with the alternating voltage flows through the reactor.
In this case, the power factor of AC input can be made close to 1.

(9) In any one of (4) to (8), a capacitor may be provided between both electric paths at the end on the AC side.
In this case, the ripple due to the switching operation of the first switch and the second switch can be absorbed by the capacitor.

(10) Further, in the power conversion device according to any one of (1) to (6), DC that performs control such that the output voltage with respect to the load is constant between the two electric circuits at the DC side end and the load. A / DC converter may be provided.
A low-frequency ripple having a period that is half of the AC period may be superimposed on the output voltage (DC voltage) between both ends of the DC side, depending on the impedance of the load. Therefore, by providing a DC / DC converter, such a low frequency ripple can be smoothed. The DC / DC converter can be selected from a step-down type, a step-up type, and a step-up / down type as required. In order to increase the current capacity, a plurality of DC / DC converters can be provided in parallel. In this case, when it is necessary to insulate each DC / DC converter from each other, an insulation type DC / DC converter can be used.

[Details of the embodiment]
Details of embodiments of the present invention will be described below with reference to the drawings. As main parts of an AC-DC power converter including an insulation transformer, for example, there are the following three types.
(A) Insulating rectifier converter: A converter that performs power conversion from alternating current to direct current through an insulating transformer.
(B) Insulated bidirectional converter: A converter that performs bidirectional power conversion between alternating current and direct current through an insulating transformer.
(C) Insulated inverter: A device that performs power conversion from DC to AC through an insulating transformer.
Here, since (c) is functionally included in (b), hereinafter, a power conversion device having the insulated rectifying converter of (a) as a main part and an insulating bidirectional converter of (b) as the main part Each of the power conversion devices will be described.

  << 1st Embodiment: The power converter device which uses an insulated rectifier converter as a principal part >>

(Overview of overall circuit configuration)
FIG. 1 is a circuit diagram of a power conversion device having an insulated rectifier converter as a main part, as a first embodiment. In the figure, a power converter 100 includes an insulated rectifier converter 10 and a step-down chopper 20 as main circuits, and a control unit 30 that controls them. Considering the control function, the control unit 30 is also a part of the insulating rectifier converter 10 and also a part of the step-down chopper 20.
This power converter 100 converts an AC input into a DC output.

  In addition, the power conversion apparatus 100 includes, as control measurement elements, a voltage sensor 31 that detects a voltage between input terminals Pa1 and Pa2 to which an AC input is supplied, a current sensor 32 that detects a current flowing through the reactor 1, an insulation A voltage sensor 33 that detects a voltage between the output terminals Pd1 and Pd2 of the rectifier converter 10 and a voltage sensor 34 that detects a voltage between the output terminals Pd3 and Pd4 of the step-down chopper 20 are provided. Detection outputs of the sensors 31 to 34 are sent to the control unit 30. Each sensor 31 to 34 can be considered to be a part of the control unit 30 in terms of function.

(Insulated rectifier converter circuit configuration)
The isolated rectifying converter 10 includes a reactor 1, a first switch S1, a second switch S2, an insulating transformer 2, a first rectifying element D1, a second rectifying element D2, and a capacitor 3 as main components of the main circuit. These are connected as shown in FIG. Note that “first” and “second” are names for convenience, and devices are equivalent. Therefore, it may be reversed.

The first switch S1 is a series of switches in which a pair of semiconductor switches S11 and S12 are connected in series so as to have opposite polarities. The semiconductor switches S11 and S12 are, for example, MOSFETs, and have body diodes D _S11 and D _S12 in parallel, respectively. The pair of semiconductor switches S11 and S12 are connected in series so that the source sides are connected to each other. Conversely, the drain sides can be connected in series so as to be connected to each other. However, connecting the source sides to each other has the advantage that the control can be performed in common.

Similarly, the second switch S2 is a series of switches in which a pair of semiconductor switches S21 and S22 are connected in series so as to have opposite polarities. The semiconductor switches S21 and S22 are, for example, MOSFETs, and have body diodes D _S21 and D _S22 in parallel, respectively.

In addition, although the circuit using MOSFET was illustrated as a switch element of semiconductor switch S11, S12, S21, S22 here, it may replace with MOSFET and may use IGBT which connected the diode antiparallel. When the IGBT is used as a switch element, a current in the reverse direction can be passed through the diode.
Further, an SiC-MOSFET in which a Schottky barrier diode is connected in antiparallel can also be used.
Further, the first switch S1 and the second switch S2 have been described as constituting a switch series body by a pair of semiconductor switches, but it is also possible to produce a one-chip device incorporating such a switch series body circuit. Is possible.

The insulating transformer 2 has a primary side neutral point 21n and a secondary side neutral point 22n in each of the primary side winding 21 and the secondary side winding 22.
Here, the electric circuit from one input terminal Pa1 on the AC side to the primary side neutral point 21n via the current sensor 32 and the reactor 1 is referred to as an AC side first electric circuit L1. In addition, the AC side second electric circuit L2 from the other input terminal Pa2 that generates an AC voltage to the input terminal Pa1 to the insulating transformer 2 branches to the two electric circuits L21 and L22 at the branch point P1 through the common circuit L20. To both ends of the primary winding 21. That is, the branched electric circuit L21 is connected to one end 21b of the primary side winding 21 through the first switch S1. Further, the branched electric circuit L22 is connected to the other end 21a of the primary winding 21 via the second switch S2.

  In addition, in this example, although the reactor 1 inserted in the alternating current side 1st electric circuit L1 was shown, you may provide the reactor 1 in the common electric circuit L20 of the alternating current side 2nd electric circuit L2. Moreover, you may insert in both the common electric circuit L20 of the alternating current side 1st electric circuit L1 and the alternating current side 2nd electric circuit L2.

The first switch S1 is in the following operation state by control.
When both the semiconductor switches S11 and S12 are turned on by the switching operation, a current flows in the direction from the end 21b of the primary winding 21 to the branch point P1 and in the opposite direction (bidirectional). Can be energized). In this case, a common control signal can be used for the semiconductor switches S11 and S12.
When both the semiconductor switches S11 and S12 are off, no current flows in the direction from the end 21b of the primary winding 21 to the branch point P1 and in the opposite direction (in a bi-directionally interrupted state). ).

When the semiconductor switch S11 is on and S12 is off, a current flows by using the diode _DS12 as an energization path in the direction from the end 21b of the primary winding 21 to the branch point P1, It does not flow in the reverse direction.
When the semiconductor switch S11 is off and S12 is on, a current flows in the direction from the branch point P1 toward the end 21b of the primary winding 21 by using the diode _DS11 as an energization path. It does not flow in the opposite direction.

Similarly, the second switch S2 is in the following operation state by control.
When both the semiconductor switches S21 and S22 are turned on by the switching operation, current flows in the direction from the end 21a of the primary winding 21 to the branch point P1 and in the opposite direction (bidirectional). Can be energized). In this case, a common control signal can be used for the semiconductor switches S21 and S22.
When both of the semiconductor switches S21 and S22 are off, no current flows in the direction from the end 21a of the primary winding 21 to the branch point P1 or in the opposite direction (in a bi-directionally interrupted state). ).

When the semiconductor switch S21 is on and S22 is off, a current flows by using the diode _DS22 as an energization path in the direction from the end 21a of the primary winding 21 to the branch point P1, It does not flow in the reverse direction.
When the semiconductor switch S21 is off and S22 is on, a current flows by using the diode _DS21 as an energization path in the direction from the branch point P1 toward the end 21a of the primary side winding 21, It does not flow in the opposite direction.

To summarize the location and operation of the first switch S1 and the location and operation of the second switch S2, the first switch S1 is inserted between the branch point P1 and one end 21b of the primary winding 21. Thus, power can be passed in both directions, and power can be cut off in both directions when the switch is off.
The second switch S2 is inserted between the branch point P1 and the other end 21a of the primary winding 21, and can be energized in both directions. In addition, the second switch S2 is bidirectional in the switch-off state. The energization can be cut off.

Moreover, according to the code | symbol of the alternating voltage input by the control part 30, either one is made into a conduction | electrical_connection state (ON holding | maintenance or diode utilization) among a pair of semiconductor switches which comprise a serial body, and the other is switched. You can also.
In this case, of the total of four semiconductor switches (S11, S12, S21, S22) of the first switch S1 and the second switch S2, the semiconductor switch that performs switching operation at a high frequency during a period in which the sign of the AC voltage is positive or negative is Since there are two, switching loss can be reduced.

  Next, the first rectifying element D1 is a diode, and the positive electrode (anode) is connected to one end 22a of the secondary winding of the insulating transformer 2. The second rectifying element D <b> 2 is a similar diode, and the positive electrode (anode) is connected to the other end 22 b of the secondary winding 22. Here, the negative electrodes (cathodes) of the first rectifying element D1 and the second rectifying element D2 are connected to each other at the junction P2, and reach one output terminal Pd1 on the DC side. When this electric circuit is called a DC side first electric circuit L3, the other DC side second electric circuit L4 is a DC side that generates a DC voltage between the secondary side neutral point 22n and one output terminal Pd1. This is an electric circuit that reaches the other output terminal Pd2.

  A smoothing capacitor 3 is connected between the output terminals Pd1 and Pd2 on the DC side as the insulating rectifier converter 10.

The control unit 30 includes an AC input voltage detected by the voltage sensor 31, an AC current detected by the current sensor 32, a DC voltage detected by the voltage sensor 33 between the output terminals Pd1 and Pd2 of the insulated rectifier converter 10, and a step-down voltage. The isolated rectifier converter 10 and the step-down chopper 20 are controlled based on the DC output voltage detected by the voltage sensor 34 between the output terminals Pd3 and Pd4 of the chopper 20.
The control unit 30 includes, for example, a computer, and realizes a control function necessary for the isolated rectifying converter 10 and the step-down chopper 20 when the computer (computer program) is executed by the computer. In this case, the software is stored in a storage device (not shown) of the control unit 30. It is also possible to configure the control unit 30 with a hardware-only circuit that does not include a computer.

(Operation of isolated rectifier converter)
In the isolated rectifying converter 10 configured as described above, the control unit 30 turns on both the first switch S1 and the second switch S2 with respect to the AC input. At this time, for example, from the input end Pa1, the AC side first electric circuit L1 including the reactor 1, the neutral point 21n of the primary side winding 21 of the insulating transformer 2, the both ends 21b and 21a of the primary side winding 21, A closed loop that passes through the first switch S1 and the second switch S2 and returns to the input terminal Pa2 via the common electric circuit L20 is formed, and energy is stored in the reactor 1. In addition, since current flows through the primary side winding 21 in opposite directions with respect to the neutral point 21n, the voltage across the primary side winding 21 becomes 0, and no voltage is generated in the secondary side winding 22. .

  Next, the control unit 30 turns off the first switch S1, for example. At this time, the energy accumulated in the reactor 1 is released to the secondary side of the insulating transformer 2, and the reactor 1 is reset by the load voltage. The voltage of the secondary winding 22 is rectified by the first rectifying element D1 and the second rectifying element D2, and is output after being smoothed by the capacitor 3.

  Subsequently, the control unit 30 turns on both the first switch S1 and the second switch S2 again. Thereby, energy is accumulated in the reactor 1. Next, the control unit 30 turns off the second switch S2. At this time, the energy accumulated in the reactor 1 is released to the secondary side of the insulating transformer 2, and the reactor 1 is reset by the load voltage. The voltage of the secondary winding 22 is rectified by the first rectifying element D1 and the second rectifying element D2, and is output after being smoothed by the capacitor 3.

  In this way, the control unit 30 performs the switching operation so that the process of turning on both of the first switch S1 and the second switch S2 and turning off one of them, turning on both, and turning off the other is repeated. The switching frequency is, for example, 10 to 20 kHz. Therefore, the ON period and the OFF period for the first switch S1 and the second switch S2 are extremely shorter than the wavelength of the AC input (for example, frequency 50 Hz).

(Summary of isolated rectifier converter)
As described above, in the above-described isolated rectifying converter 10, energy is accumulated in the reactor 1 during a period in which both the first switch S1 and the second switch S2 are on. When one of the first switch S1 and the second switch S2 is turned off, energy is released to the secondary side of the insulating transformer 2, and the reactor 1 is reset by the load voltage. The voltage of the secondary winding 22 is rectified by the first rectifying element D1 and the second rectifying element D2, and is output after being smoothed by the capacitor 3. Since the first switch S1 and the second switch S2 are bidirectional, such a function as a current converter can be realized regardless of the sign (direction) of the AC voltage / AC current.

Therefore, a low-frequency alternating current such as a commercial frequency can be transformed by the insulating transformer 2 by high-frequency switching without being rectified, and rectified on the secondary side to be a direct-current output. According to such a configuration, conversion from the AC input to the isolation transformer 2 can be realized by switching only the first switch S1 and the second switch S2.
In this way, it is possible to obtain an AC-to-DC isolated rectifier converter 10 that has the insulating transformer 2 and suppresses the total number of switches.

(Details of step-down chopper)
Next, the step-down chopper 20 includes a switch S5, a diode D3, a reactor 13, and a capacitor 4. Switch S5 is, for example, a MOSFET having a body diode _{D S5.} The step-down chopper 20 steps down the output voltage of the isolated rectifier converter 10 by switching the switch S5 with a predetermined duty, and outputs it to the output terminals Pd3 and Pd4. The voltage between the output terminals Pd3 and Pd4 is detected by the voltage sensor 34.

  Note that providing the step-down chopper 20 as a DC / DC converter is merely an example, and can be selected from a step-down type, a step-up type, and a step-up / step-down type as necessary. In order to increase the current capacity, a plurality of DC / DC converters can be provided in parallel. In this case, when it is necessary to insulate each DC / DC converter from each other, an insulation type DC / DC converter can be used.

  As described above, by providing the DC / DC converter between both ends of the insulated rectifier converter 10 and the load, it is possible to perform control in which the output voltage with respect to the load becomes constant. That is, a low-frequency ripple having a period that is half of the AC period may be superimposed on the output voltage (DC voltage) between both ends of the insulating rectifier converter 10 depending on the impedance of the load. Therefore, by providing a DC / DC converter, such a low frequency ripple can be smoothed and a higher quality DC output can be obtained.

(Example of control block diagram)
Next, a specific example of control by the control unit 30 will be described using a control block diagram.
First, for example, the AC frequency is 50 Hz, the effective value of the AC voltage is 202 V, the DC output voltage is 48 V, and the load resistance is 1 Ω (about 2.3 kW). The output voltage of the insulating rectifier converter 10 is 100 V, and the winding ratio of the insulating transformer 2 is 3: 1. A capacitor 3 having a capacitance Cm of 4 mF was placed between the insulating rectifier converter 10 and the step-down chopper 20 in order to smooth the low frequency ripple of 100 Hz.

FIG. 2 is a control block diagram until the reactor current command value Ic * to be passed through the reactor 1 is obtained.
In order to set the power factor of the AC input to 1, a current synchronized with the AC voltage must flow. First, the AC voltage Va and the reactor current Ic are detected by the voltage sensor 31 and the current sensor 32, respectively. Reactor current command value Ic * is determined so that the waveform of detected reactor current value Ic matches AC voltage Va.

  Reactor current command value Ic * was converted to the primary side by combining the reactive current flowing through smoothing capacitor 3 (capacitance Cm) on the secondary side of insulation transformer 2 and the output current of insulated rectifier converter 10. Can be considered a thing. The reactive current of the capacitance Cm is used to convert the value obtained by passing the PI compensator into the deviation between the output target voltage 100V (= Vm *) and the voltage detection value Vm at both ends of the capacitance Cm to the primary value. , And multiplied by 1/3 (“K” in FIG. 2) that is the reciprocal of the winding ratio (n1 / n2) of the insulating transformer 2. Thereby, feedback control of the output voltage of the insulating rectifier converter 10 is incorporated in the control system.

  The output current is substituted with the reactor current detection value Ic (absolute value) of the insulating rectifier converter 10. Since the reactor current detection value Ic is originally a value on the primary side of the transformer, no conversion is necessary. An average current command value of the insulating rectifier converter 10 is obtained by averaging this with the reactive current component obtained previously and averaging the alternating current period (50 Hz). The reactor current command value Ic * can be obtained by multiplying this average value by a sine wave obtained by standardizing the AC voltage Va.

  FIG. 3 is a control block diagram for obtaining the reference wave Vref. In the figure, the value obtained by passing the PI compensator to the deviation between the reactor current command value Ic * and the reactor current detection value Ic is subtracted from the AC voltage detection value (AC voltage) Va. The reference value Vref can be obtained by dividing the resultant value by the voltage obtained by converting the voltage detection value Vm at both ends of the capacitance Cm to the primary side.

  4 and 5 are control block diagrams showing the PWM (Pulse Width Modulation) gate pulse calculation logic of the isolated rectifying converter 10. Each of the first switch S1 and the second switch S2 is a switch series body in which a pair of semiconductor switches and antiparallel diodes are connected in series so as to have opposite polarities. Therefore, according to the sign of the AC voltage, one semiconductor switch of the switch series body is switched at a high frequency (for example, 10 kHz), and the other semiconductor switch is turned off and the diode is used as a current-carrying path or turned on without depending on the diode. Hold on. That is, the two semiconductor switches (S11 and S12, S21 and S22) constituting each of the first switch S1 and the second switch S2 are individually controlled on and off.

  For this purpose, for example, a virtual gate corresponding to the high side of the non-insulated chopper is once created (FIG. 4 (a), FIG. 5 (a)), and this virtual gate is used as a virtual gate carrier wave (20 kHz). A rectangular pulse with a double period (10 kHz) is input to the NAND gate ((b) in FIG. 4 and (b) in FIG. 5). If the phases of the rectangular pulses of the semiconductor switches are shifted from each other by 180 degrees (FIG. 4 (c), FIG. 5 (c)), a pulse in which the OFF periods of the two switches are alternated can be generated.

  For the semiconductor switches S11 and S21 that perform switching when the sign of the input AC voltage is positive, a virtual gate drive pulse GateA obtained by passing a reference wave and a carrier wave through a comparator is used (FIG. 4). Based on GateA, gate drive pulses Gate1 and Gate2 of the semiconductor switches S11 and S21 are obtained.

  On the other hand, for the semiconductor switches S12 and S22 that perform switching when the sign of the input AC voltage is negative, the virtual gate drive pulse GateB obtained by using the reference wave with the sign inverted is used (FIG. 5). Based on this GateB, gate drive pulses Gate3 and Gate4 of the semiconductor switches S12 and S22 are obtained.

  FIG. 6 is a control block diagram of the step-down chopper 20. The step-down chopper 20 performs simple hysteresis control using two comparators that set the upper limit value and the lower limit value of the output voltage as constant voltages and compare with the output voltage detection value Vout, and a flip-flop. Thus, the gate drive pulse Gate5 of the semiconductor switch S5 is obtained.

(Waveform diagram)
FIG. 7 shows the input AC voltage Va, the gate drive pulses Gate1, Gate2, Gate3, Gate4 of the insulating rectifier converter 10, the reactor current command value Ic * () in a part of the section where the sign of the AC voltage transitions from positive to negative. It is a wave form diagram which shows the detection value Ic (one with a ripple) and the detection value Ic. In the first half of the positive sign of the AC voltage Va, the semiconductor switches S11 and S21 perform switching based on the gate drive pulses Gate1 and Gate2. The gate drive pulse of the other semiconductor switch S12, S22 in series holds the H level (ON). However, the gate drive pulses of the other semiconductor switches S12 and S22 in this case may be kept at the L level (off), and in this case, the anti-parallel diode becomes the energization path.

  In the second half in which the sign of the AC voltage Va is negative, the semiconductor switches S12 and S22 perform switching based on the gate drive pulses Gate3 and Gate4. The gate drive pulse of the other semiconductor switch S11, S21 in series holds the H level (ON). However, the gate drive pulses of the other semiconductor switches S11 and S21 in this case may be held at the L level (off), and in this case, the anti-parallel diode becomes the energization path.

  Although the reactor current detection value Ic includes ripples, it closely follows the reactor current command value Ic * and substantially matches. The ripple period is half the switching period of the semiconductor switch.

  FIG. 8 is a waveform diagram of input / output in the isolated rectifier converter 10 and the step-down chopper 20. In order from the top, the AC voltage Va input to the isolated rectifying converter 10, the reactor current detection value Ic as the input current, the voltage detection value Vm at both ends of the capacitor 3, and the output voltage detection value Vout of the step-down chopper 20 are shown. . The power factor of the input current is 0.999, and the distortion rate is 3.3% (0.5% below the 40th order), both of which are satisfactory values. The voltage detection value Vm is expressed as an AC waveform because the numerical range of the vertical axis is narrowed, but it appears as an AC waveform, but includes a frequency component twice as high as the AC voltage Va, a minimum of 90.40 V, a maximum of 109.0 V, and an average. It is a DC voltage with a value of 100V. The output voltage Vout through the step-down chopper 20 is 48.02 V (maximum 48.50 V, minimum 47.53 V), which matches the target value, and the ripple is as small as 2%, and a good result is obtained.

(Supplement)
The isolated rectifying converter 10 of the present embodiment can perform functions of rectification, power factor improvement, and insulation with a single converter, so that the circuit is simplified, and miniaturization and high efficiency are possible.
When a DC voltage with a small ripple is required, a DC / DC converter such as a step-down chopper 20 that outputs a constant output voltage may be added to the output side of the isolated rectifying converter 10. This DC / DC converter can be a non-insulated circuit with few components. Therefore, it is advantageous when the capacity is increased by connecting a plurality of DC / DC converters in parallel. For example, when the output circuits are 5 in parallel, the total number of semiconductor devices combined with the rectifier circuit is 24 in the non-insulated rectification type, whereas in the isolated rectifier converter 10 of this embodiment, 16 is sufficient. This makes it possible to reduce the size and loss. In the present embodiment, the DC chopper is the step-down chopper 20 as viewed from the DC bus side (both ends of the capacitor 3). However, this is replaced with a step-up chopper or a step-up / step-down chopper according to the required final output voltage. Also good.

  << 2nd Embodiment: The power converter device which has an insulated bidirectional converter as a principal part >>

(Overview of overall circuit configuration)
FIG. 9 is a circuit diagram of a power conversion device mainly including an insulated bidirectional converter as a second embodiment. In the figure, a power converter 100 includes an insulated bidirectional converter 10 and a bidirectional chopper 20 as main circuits, and a control unit 30 for controlling them. Considering the control function, the control unit 30 is also a part of the insulating rectifier converter 10 and a part of the bidirectional chopper 20.
The power conversion apparatus 100 can convert an AC input into a DC output, and can convert a DC input into an AC output.

  In addition, the power conversion apparatus 100 includes, as control measurement elements, a voltage sensor 31 that detects a voltage between the ports Pa1 and Pa2 on the AC side, a current sensor 32 that detects a current flowing through the reactor 1, and an insulated bidirectional converter 10. A voltage sensor 33 for detecting a voltage between the ports Pd1 and Pd2, a voltage sensor 34 for detecting a voltage between the ports Pd3 and Pd4 of the bidirectional chopper 20, and a current sensor 35 for detecting a current flowing through the reactor 13. Yes. Detection outputs of the sensors 31 to 35 are sent to the control unit 30. Each sensor 31 to 35 can be considered to be a part of the control unit 30 in terms of function.

(Circuit configuration of isolated bidirectional converter)
The insulated bidirectional converter 10 includes, as main components of the main circuit, an AC capacitor 5, a reactor 1 across two wires, a first switch S 1, a second switch S 2, an insulation transformer 2, a third switch S 3, a fourth switch. A switch S4 and a capacitor 3 are provided, and these are connected as shown in FIG. Note that “first” and “second” are names for convenience, and devices are equivalent. Therefore, it may be reversed. Similarly, “third” and “fourth” are names for convenience, and the devices are equivalent, and may be reversed.

The first switch S1 is a series of switches in which a pair of semiconductor switches S11 and S12 are connected in series so as to have opposite polarities. The semiconductor switches S11 has a MOSFET and a body diode _{D S11} as a switch element. The semiconductor switches S12, includes a MOSFET and a body diode _{D S12} as a switching element. The pair of semiconductor switches S11 and S12 are connected in series so that the source sides are connected to each other. Conversely, the drain sides can be connected in series so as to be connected to each other. However, connecting the source sides to each other has the advantage that the control can be performed in common.

Similarly, the second switch S2 is a series of switches in which a pair of semiconductor switches S21 and S22 are connected in series so as to have opposite polarities. The semiconductor switch S21 includes a MOSFET as a switch element and a body diode _DS21 . The semiconductor switch S22 includes a MOSFET and a body diode _DS22 as switching elements.

  The MOSFET is merely an example as a semiconductor switch. Further, the first switch S1 and the second switch S2 have been described as constituting a switch series body by a pair of semiconductor switches, but it is also possible to produce a one-chip device incorporating such a switch series body circuit. Is possible.

The insulating transformer 2 has a primary side neutral point 21n and a secondary side neutral point 22n in each of the primary side winding 21 and the secondary side winding 22.
Here, an electric circuit from one port Pa1 on the AC side to the primary side neutral point 21n via the current sensor 32 and the reactor 1 is referred to as an AC side first electric circuit L1. The AC-side second electric circuit L2 from the other port Pa2 that generates an AC voltage to the port Pa1 to the insulating transformer 2 branches to the two electric circuits L21 and L22 at the branch point P1 via the common electric circuit L20. It reaches both ends of the secondary winding 21. That is, the branched electric circuit L21 is connected to one end 21b of the primary side winding 21 through the first switch S1. Further, the branched electric circuit L22 is connected to the other end 21a of the primary winding 21 via the second switch S2.

The first switch S1 is in the following operation state by control.
When both the semiconductor switches S11 and S12 are turned on by the switching operation, a current flows in the direction from the end 21b of the primary winding 21 to the branch point P1 and in the opposite direction (bidirectional). Can be energized). In this case, a common control signal can be used for the semiconductor switches S11 and S12.
When both the semiconductor switches S11 and S12 are off, no current flows in the direction from the end 21b of the primary winding 21 to the branch point P1 and in the opposite direction (in a bi-directionally interrupted state). ).

When the semiconductor switch S11 is on and S12 is off, a current flows by using the diode _DS12 as an energization path in the direction from the end 21b of the primary winding 21 to the branch point P1, It does not flow in the reverse direction.
When the semiconductor switch S11 is off and S12 is on, a current flows in the direction from the branch point P1 toward the end 21b of the primary winding 21 by using the diode _DS11 as an energization path. It does not flow in the opposite direction.

Similarly, the second switch S2 is in the following operation state by control.
When both the semiconductor switches S21 and S22 are turned on by the switching operation, current flows in the direction from the end 21a of the primary winding 21 to the branch point P1 and in the opposite direction (bidirectional). Can be energized). In this case, a common control signal can be used for the semiconductor switches S21 and S22.
When both of the semiconductor switches S21 and S22 are off, no current flows in the direction from the end 21a of the primary winding 21 to the branch point P1 or in the opposite direction (in a bi-directionally interrupted state). ).

When the semiconductor switch S21 is on and S22 is off, a current flows by using the diode _DS22 as an energization path in the direction from the end 21a of the primary winding 21 to the branch point P1, It does not flow in the reverse direction.
When the semiconductor switch S21 is off and S22 is on, a current flows by using the diode _DS21 as an energization path in the direction from the branch point P1 toward the end 21a of the primary side winding 21, It does not flow in the opposite direction.

To summarize the location and operation of the first switch S1 and the location and operation of the second switch S2, the first switch S1 is inserted between the branch point P1 and one end 21b of the primary winding 21. Thus, power can be passed in both directions, and power can be cut off in both directions when the switch is off.
The second switch S2 is inserted between the branch point P1 and the other end 21a of the primary winding 21, and can be energized in both directions. In addition, the second switch S2 is bidirectional in the switch-off state. The energization can be cut off.

Moreover, according to the code | symbol of the alternating voltage input by the control part 30, either one is made into a conduction | electrical_connection state (ON holding | maintenance or diode utilization) among a pair of semiconductor switches which comprise a serial body, and the other is switched. You can also.
In this case, of the total of four semiconductor switches (S11, S12, S21, S22) of the first switch S1 and the second switch S2, the semiconductor switch that performs switching operation at a high frequency during a period in which the sign of the AC voltage is positive or negative is Since there are two, switching loss can be reduced.

Next, the third switch S3 is provided with a MOSFET and a body diode _{D S3} as a switching element. The positive electrode of the MOSFET of the source and the body diode _{D S3} (anode) is connected to one end 22a of the secondary coil of a transformer 2. The fourth switch S4 includes a MOSFET as a switch element and a body diode _DS4 . The positive electrode of the MOSFET of the source and the body diode _{D S4} (anode) is connected to the other end 22b of the secondary coil of a transformer 2.

The drains of the switches S3 and S4 (MOSFETs) and the negative electrodes (cathodes) of the body diodes D _S3 and D _S4 are connected to each other at the junction P2 and reach one port Pd1 on the DC side. When this circuit is called a DC side first circuit L3, the other DC side second circuit L4 is a DC side that generates a DC voltage from the secondary side neutral point 22n to one port Pd1. This is an electric circuit leading to the other port Pd2.

  A smoothing capacitor 3 is connected between the ports Pd1 and Pd2 on the DC side as the insulated bidirectional converter 10.

The control unit 30 includes an AC input voltage detected by the voltage sensor 31, an AC current detected by the current sensor 32, a DC voltage detected by the voltage sensor 33 between the ports Pd1 and Pd2 of the insulated bidirectional converter 10, and both. Based on the DC output voltage detected by the voltage sensor 34 between the ports Pd3 and Pd4 of the direction chopper 20, the insulated bidirectional converter 10 and the bidirectional chopper 20 are controlled.
The control unit 30 includes, for example, a computer, and realizes functions necessary for the insulated bidirectional converter 10 and the bidirectional chopper 20 when the computer (computer program) is executed by the computer. In this case, the software is stored in a storage device (not shown) of the control unit 30. It is also possible to configure the control unit 30 with a hardware-only circuit that does not include a computer.

(Operation of isolated bidirectional converter)
(Forward (AC to DC))
The function of the insulated bidirectional converter 10 when performing conversion from alternating current to direct current is the same as that of the insulated rectifying converter 10 in the first embodiment.
First, with respect to the AC input, the control unit 30 turns on both the first switch S1 and the second switch S2. At this time, for example, from the port Pa1, the AC side first electric circuit L1 including the reactor 1, the neutral point 21n of the primary side winding 21 of the insulation transformer 2, the both ends 21b and 21a of the primary side winding 21, the first A closed loop that passes through the switch S1 and the second switch S2 and returns to the port Pa2 through the common electric circuit L20 including the reactor is formed, and energy is accumulated in the reactor 1. In addition, since current flows through the primary side winding 21 in opposite directions with respect to the neutral point 21n, the voltage across the primary side winding 21 becomes 0, and no voltage is generated in the secondary side winding 22. .

Next, the control unit 30 turns off the first switch S1, for example. At this time, the energy accumulated in the reactor 1 is released to the secondary side of the insulating transformer 2, and the reactor 1 is reset by the load voltage. The voltage of the secondary winding 22 is rectified by the body diodes D _S3 and D _S4 , and is output after being smoothed by the capacitor 3.

Subsequently, the control unit 30 turns on both the first switch S1 and the second switch S2 again. Thereby, energy is accumulated in the reactor 1. Next, the control unit 30 turns off the second switch S2. At this time, the energy accumulated in the reactor 1 is released to the secondary side of the insulating transformer 2, and the reactor 1 is reset by the load voltage. The voltage of the secondary winding 22 is rectified by the body diodes D _S3 and D _S4 , and is output after being smoothed by the capacitor 3.

  In this way, the control unit 30 performs the switching operation so that the process of turning on both of the first switch S1 and the second switch S2 and turning off one of them, turning on both, and turning off the other is repeated. The switching frequency is, for example, 10 to 20 kHz. Therefore, the ON period and the OFF period for the first switch S1 and the second switch S2 are extremely shorter than the wavelength of the AC input (for example, frequency 50 Hz).

As described above, in the above-described insulated bidirectional converter 10, energy is stored in the reactor 1 during a period in which both the first switch S1 and the second switch S2 are on. When one of the first switch S1 and the second switch S2 is turned off, energy is released to the secondary side of the insulating transformer 2, and the reactor 1 is reset by the load voltage. The voltage of the secondary winding 22 is rectified by the body diodes D _S3 and D _S4 , and is output after being smoothed by the capacitor 3. Since the first switch S1 and the second switch S2 are bidirectional, such a function as a current converter can be realized regardless of the sign (direction) of the AC voltage / AC current.

Therefore, a low-frequency alternating current such as a commercial frequency can be transformed by the insulating transformer 2 by high-frequency switching without being rectified, and rectified on the secondary side to be a direct-current output. According to such a configuration, conversion from the AC input to the isolation transformer 2 can be realized by switching only the first switch S1 and the second switch S2.
In this way, it is possible to obtain an AC to DC isolated bidirectional converter 10 that has the isolation transformer 2 and suppresses the total number of switches.

(Details of bidirectional chopper)
Next, the bidirectional chopper 20 includes a switch (MOSFET) S5 having a body diode D _S5 , a switch (MOSFET) _S6 having a body diode D _S6 , a reactor 13, and a capacitor 4. The bidirectional chopper 20 steps down the output voltage of the isolated bidirectional converter 10 by switching the switches S5 and S6 with a predetermined duty, and outputs it to the ports Pd3 and Pd4. The voltage between the ports Pd3 and Pd4 is detected by the voltage sensor 34. The output current is detected by the current sensor 35.

  Note that providing the bidirectional chopper 20 as a DC / DC converter is merely an example, and can be selected from a step-down type, a step-up type, and a step-up / down type as necessary. In order to increase the current capacity, a plurality of DC / DC converters can be provided in parallel. In this case, when it is necessary to insulate each DC / DC converter from each other, an insulation type DC / DC converter can be used.

  As described above, by providing the DC / DC converter between the two electric circuits at the end of the insulated bidirectional converter 10 and the load, it is possible to perform control so that the output voltage with respect to the load becomes constant. That is, a low-frequency ripple having a period that is half of the AC period may be superimposed on the output voltage (DC voltage) between both electric circuits at the end of the insulated bidirectional converter 10 depending on the impedance of the load. Therefore, by providing a DC / DC converter, such a low frequency ripple can be smoothed.

(Reverse conversion (DC to AC))
On the other hand, in reverse conversion, direct current is converted into alternating current. The DC voltage input to the ports Pd3 and Pd4 can be boosted to a predetermined voltage by turning on the switches S5 and S6 of the bidirectional chopper 20 alternately. The boosted DC voltage is input to the insulated bidirectional converter 10.
Here, the secondary side circuit of the isolation transformer 2 can be operated as a push-pull converter. However, since the switch of the primary circuit blocks bidirectional current and voltage, it does not operate as a push-pull converter unless at least one of the switches included in the bidirectional switch is actively turned on.

Therefore, in the circuit shown in FIG. 9, when the third switch S3 on the secondary side of the isolation transformer 2 is turned on, the first switch S1 is turned on on the primary side. When the fourth switch S4 on the secondary side of the isolation transformer 2 is turned on, the second switch S2 is turned on on the primary side. As a result, a voltage having a positive sign is generated at the ports Pa1-Pa2 on the AC side.
Conversely, to generate a voltage with a negative sign, when the third switch S3 on the secondary side of the isolation transformer 2 is turned on, the second switch S2 is turned on on the primary side. When the fourth switch S4 on the secondary side of the isolation transformer 2 is turned on, the first switch S1 is turned on on the primary side. As a result, a voltage having a negative sign is generated at the ports Pa1-Pa2 on the AC side.
An AC waveform can be obtained by PWM control of each on time.

  In the above-described insulated bidirectional converter 10, an AC half-cycle pulsating current flows on the DC side, as in a non-insulated inverter. In order to smooth the current flowing through the DC power supply or the load, a chopper having a reactor disposed on the DC side of the insulating bidirectional converter 10 on the right side of the smoothing capacitor 3 may be connected. The chopper is a step-down type because it is in the order of a bridge and a reactor when viewed from the capacitor 3. In this configuration, both the AC power supply and the connection portion with the DC power supply are reactor inputs, and the input / output current is continuous. Therefore, a normal choke is basically unnecessary, and the filter circuit can be simplified.

  As the first switch S1 and the second switch S2 which are bidirectional switches, two MOSFETs having a common source or an IGBT including an antiparallel diode having a common emitter can be used. Current detection is performed at two locations: the current of the AC reactor 1 included in the insulated bidirectional converter (current sensor 32) and the current of the DC reactor 13 included in the bidirectional chopper 20 (current sensor 35). The voltage is detected at three locations: an AC voltage (voltage sensor 31), a link voltage (voltage sensor 33), and a DC voltage (voltage sensor 34).

(Summary of isolated bidirectional converter)
According to the insulated bidirectional converter 10 as described above, during conversion from alternating current to direct current, energy is accumulated in the reactor 1 while both the first switch S1 and the second switch S2 are on. When one of the first switch S1 and the second switch S2 is turned off, energy is released to the secondary side of the insulating transformer 2, and the reactor 1 is reset by the load voltage. The voltage of the secondary winding is rectified by the body diodes D _S3 and D _S4 , and is output after being smoothed by the capacitor 3. Since the first switch S1 and the second switch S2 are bidirectional, such a function as a current converter can be realized regardless of the sign (direction) of the AC voltage / AC current.

  Therefore, a low-frequency alternating current such as a commercial frequency can be transformed by the insulating transformer 2 by high-frequency switching without being rectified, and rectified on the secondary side to be a direct-current output. According to such a configuration, conversion from the AC input to the isolation transformer 2 can be realized by switching only the first switch S1 and the second switch S2.

On the other hand, when converting from direct current to alternating current, the third switch S3 and the fourth switch S4 are alternately turned on so that the secondary side (DC side) circuit of the isolation transformer 2 operates as a push-pull converter. be able to. On the primary side of the isolation transformer 2, one of the first switch S 1 and the second switch S 2 is turned on in correspondence with the on state of either the third switch S 3 or the fourth switch S 4. , Can generate alternating current.
Thus, it is possible to obtain a bidirectional power conversion device that has the isolation transformer 2 and suppresses the total number of switches.

(Example of control block diagram)
Next, a specific example of control by the control unit 30 will be described using a control block diagram.
First, for example, the AC frequency is 50 Hz, the effective value of the AC voltage is 202 V, and the DC voltage is 200 V. The frequency of the AC power supply is 50 Hz, and the effective value of the AC voltage Va is 202V. A power supply with a voltage of 200 V is connected to the DC side. The target value of the interconnection point between the insulating bidirectional converter 10 and the bidirectional chopper 20 is 350 V, and the winding ratio of the insulating transformer 2 is 1: 1. The capacitor 5 on the AC side is a film capacitor having a capacitance Ca of 22 μF in order to smooth the switching ripple of the insulating bidirectional converter 10. The capacitor 3 (capacitance Cm) is a 4 mF electrolytic capacitor for smoothing the low frequency ripple of 100 Hz.

(Control block diagram)
FIG. 10 is a control block diagram for obtaining the reactor current command value and the reference wave. In the control block diagram on the left side of the figure, first, an alternating current command value Ia * is given. Ia * can set an arbitrary phase with respect to the AC voltage detection value (AC voltage) Va. When the current flowing from the AC power source toward the DC power source is defined as positive, charging from the AC power source to the DC power source if the phase is 0 degrees, and discharging from the DC power source to the AC power source if the phase is 180 degrees. Become. In addition, the delay phase and the lead phase can be arbitrarily set. The reactor current command value Ic * is obtained by adding a reactive current (calculated by multiplying the differential of the AC voltage detection value by Ca) flowing through the capacitance Ca of the capacitor 5 to Ia *.

  On the right side of FIG. 10, the reactor voltage can be obtained by the reactor current feedback that inputs the deviation between Ic * and the detected reactor current value Ic to the proportional-integral compensator. A reference wave is obtained by subtracting this reactor voltage from the AC voltage detection value and dividing by the voltage detection value Vm of the capacitor 3 (Cm) converted to the primary side (bidirectional switch side) in consideration of the transformer turns ratio. V_ref is obtained.

FIG. 11 is a control block diagram showing the PWM gate pulse calculation logic.
In FIG. 11A, a reference pulse and a carrier wave (triangular wave) are input to a comparator to obtain a drive pulse GateA for the virtual gate A. Next, in (b), GateA and a rectangular wave whose period is twice that of the carrier wave (half the frequency) are input to the AND gate, and Gate4P is input to the NOT gate, and Gate1P is obtained. Similarly, in (c), GateA and the rectangular wave are obtained by inputting a rectangular wave whose phase is shifted by 180 degrees to the AND gate, and further inputting this to the NOT gate, thereby obtaining Gate2P.

  Further, in (f), the reference pulse and carrier wave whose signs are inverted are input to the comparator to obtain the drive pulse GateB of the virtual gate B. In (g), as in Gate A, Gate 3 and a rectangular wave whose period is twice that of the carrier wave (frequency is half) are input to the AND gate to obtain Gate 3N, which is then input to the NOT gate. To obtain Gate1N. In (h), Gate 4N is obtained by inputting Gate B and a rectangular wave whose phase is 180 degrees out of phase with the rectangular wave, and Gate 2N is obtained by inputting the same to the NOT gate.

  Gate1 and Gate2 are obtained by AND-inputting Gate1P and Gate1N, Gate2P and Gate2N, respectively. These are gate drive pulses for the first switch S1 and the second switch S2, which are two bidirectional switches on the primary side of the insulated bidirectional converter 10. Gate3 and Gate4 are obtained by inputting Gate3P and Gate3N, and Gate4P and Gate4N to the OR gate, respectively. These are gate drive pulses of the third switch S3 and the fourth switch S4 on the secondary side of the insulated bidirectional converter 10.

FIG. 12 is a control block diagram for obtaining the current command value of the reactor 13 in the bidirectional chopper 20.
First, the target voltage of the capacitor 3 (capacitance Cm) is set to Vm *, and a deviation from the voltage detection value Vm is input to the proportional-integral compensator to feed back Vm, thereby obtaining a reactive current flowing through Cm. Considering Vm and the DC power supply voltage Vg, this is converted into a current value on the DC power supply side. By subtracting this reactive current from the DC power supply current, a current command value Ig * of the reactor 13 (DC reactor) is obtained. In this case, the current detection value Ig of the reactor 13 is used instead of the detection circuit for the DC power supply current. doing. The low frequency ripple generated by the isolated bidirectional converter is absorbed by the smoothing capacitor Cm, and a direct current that does not include ripple is caused to flow in the direct current power supply. Therefore, the current command value Ig * is averaged over a half period of alternating current, not as it is. Use the numerical value.

FIG. 13 is a control block diagram showing the PWM gate pulse calculation logic.
First, the deviation between Ig * and the detected value Ig is input to the proportional-integral compensator, the voltage detection value Vg of the DC power supply is added to this, and further divided by the voltage detection value of Cm to obtain the reference wave Vm_ref. By inputting this reference wave Vm_ref together with the carrier wave to the comparator, the drive pulse Gate5 of the high-side switch S5 of the bidirectional chopper 20 is obtained. The drive pulse Gate6 of the low-side switch S6 is obtained by inputting Gate5 to the NOT gate.

(Waveform diagram)
FIG. 14 is a waveform diagram showing the gate drive pulse, voltage, and current waveforms of the insulated bidirectional converter 10. This figure shows a period in which the sign of the current Ic of the reactor 1 changes from positive to negative in the reverse conversion. Since the current flowing from the AC side to the DC side is positive, the phases of the AC voltage and the reactor current are shifted from each other by 180 degrees. Gate 1 and Gate 2 have alternating off periods. When the sign of Ic is positive, the off period of Gate 1 coincides with the on period of Gate 3, and the off period of Gate 2 coincides with the on period of Gate 4. When Ic is a negative period, the OFF period of Gate1 changes to match the ON period of Gate4, and the OFF period of Gate2 changes to match the ON period of Gate3.

  FIG. 15 is an input / output waveform diagram in the reverse conversion of the insulated bidirectional converter 10 and the bidirectional chopper 20. The AC output current Iac is synchronized with the AC voltage Va, and the power factor approaches 1 as much as possible and is 99.9%. The overall distortion rate of the output current is 1.6%, which is sufficiently small. A low frequency ripple of 100 Hz is superimposed on the link voltage Vm, but the current (Ib) output from the DC power source by the chopper is smoothed to a ripple rate of 0.6%, which is not a problem.

  FIG. 16 is a waveform diagram when transitioning from forward conversion to reverse conversion. In this example, switching from forward conversion to reverse conversion is performed by gradually changing the amplitude and phase of the AC current command value Ia * during 0.1 seconds. However, both the AC current Ia and the DC current Ib have waveforms. Is changing without being disturbed.

  As in the first embodiment, the isolated bidirectional converter 10 can perform functions of rectification, power factor improvement, insulation, and reverse conversion with a single converter, thereby simplifying the circuit, reducing size, and increasing efficiency. Can be realized.

<Appendix>
In addition, about each above-mentioned embodiment, you may combine the at least one part arbitrarily mutually.
The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 1 Reactor 2 Insulation transformer 3, 4, 5 Capacitor 10 Insulation rectification converter, insulation bidirectional converter 13 Reactor 20 Step-down chopper, bidirectional chopper 21 Primary side winding 21a, 21b End part 21n Primary side neutral point 22 Secondary Side winding 22a, 22b End 22n Secondary side neutral point 30 Control unit 31 Voltage sensor 32 Current sensor 33, 34 Voltage sensor 35 Current sensor 100 Power converter 201 Insulation transformer 202 Rectifier circuit 203 Boost chopper circuit 204 DC / DC Converter 205 bipolar step-up chopper circuit 206 rectifier circuit 207 DC / DC converter 208 rectifier circuit 209 DC / DC converter D1 first rectifier element D2 second rectifier element D _S11 , D _S12 , D _S21 , D _S22 diode L1 AC side first Electric circuit L AC side second electric circuit L3 DC side first electric circuit L4 DC side second electric circuit L20 Common electric circuit L21, L22 Electric circuit P1 Branch point P2 Junction point Pa1, Pa2 input terminal, port Pd1, Pd2 output terminal, port Pd3, Pd4 output terminal, Port S1 First switch S2 Second switch S3 Third switch S4 Fourth switch S11, S12, S21, S22 Semiconductor switch

Claims (10)

A power conversion device that performs power conversion from alternating current to direct current,
An insulating transformer having a primary side neutral point and a secondary side neutral point in each of the primary side winding and the secondary side winding;
An AC side first electric circuit extending from one input end of the AC side to the primary side neutral point;
A second AC circuit on the AC side that branches from the other input terminal on the AC side through the common circuit to the two circuits at the branch point and reaches both ends of the primary winding;
A reactor inserted in at least one of the AC side first electric circuit and the common electric circuit;
A first switch that can be energized in both directions and cuts off in both directions when switched off, and is inserted between the branch point and one end of the primary winding;
A second switch that can be energized in both directions and cuts off the current in both directions in a switch-off state, and is inserted between the branch point and the other end of the primary winding;
A first rectifying element having a positive electrode connected to one end of the secondary winding;
A second rectifying element having a positive electrode connected to the other end of the secondary winding;
A DC side first electric circuit that connects the negative electrodes of the first rectifying element and the second rectifying element to each other and reaches one output terminal on the DC side;
A DC side second electric circuit extending from the secondary side neutral point to the other output end of the DC side;
A capacitor provided between the one output end and the other output end;
A controller that performs a switching operation so that both the first switch and the second switch are on, one is off, both are on, and the other is off; and
A power conversion device comprising:   Each of the first switch and the second switch is composed of a pair of semiconductor switches each having a diode connected in parallel to a bidirectionally switchable element and connected in series so that the diodes have opposite polarities. The power converter according to claim 1 which is a switch series object.   The power conversion device according to claim 2, wherein the control unit switches one of the pair of semiconductor switches to a conductive state and switches the other according to a sign of an input AC voltage. A power conversion device that performs bidirectional power conversion between alternating current and direct current,
An insulation transformer having a primary side neutral point and a secondary side neutral point in each of the AC side primary side winding and the DC side secondary side winding;
An AC side first electric circuit extending from one port on the AC side to the primary side neutral point;
An AC side second electric circuit that branches from the other port on the AC side through a common electric circuit to two electric circuits at a branch point and reaches both ends of the primary side winding;
A reactor inserted in at least one of the AC side first electric circuit and the common electric circuit;
A first switch that can be energized in both directions and cuts off in both directions when switched off, and is inserted between the branch point and one end of the primary winding;
A second switch that can be energized in both directions and cuts off the current in both directions in a switch-off state, and is inserted between the branch point and the other end of the primary winding;
A third switch provided in parallel with a rectifying element having a positive electrode connected to one end of the secondary winding;
A fourth switch provided in parallel with a rectifying element having a positive electrode connected to the other end of the secondary winding;
A DC side first electric circuit that connects the negative electrodes of the rectifier element of the third switch and the rectifier element of the fourth switch to each other and reaches one port on the DC side;
A DC side second electric circuit extending from the secondary side neutral point to the other port on the DC side;
A capacitor provided between one port on the DC side and the other port on the DC side;
At the time of conversion from AC to DC, a switching operation is repeated so that both the first switch and the second switch are turned on, one is turned off, both are turned on, and the other is turned off. At the time of conversion to alternating current, a switching operation for alternately turning on the third switch and the fourth switch is performed, and correspondingly, the first switch and the second switch are alternately turned on. A control unit for performing a switching operation of
A power conversion device comprising:   Each of the first switch and the second switch is composed of a pair of semiconductor switches each having a diode connected in parallel to a bidirectionally switchable element and connected in series so that the diodes have opposite polarities. The power converter according to claim 4 which is a switch series body.   At the time of conversion from direct current to alternating current, the control unit turns on one of the first switch and the second switch in response to the on state of either the third switch or the fourth switch. The power converter according to claim 5, wherein the sign of the AC voltage is positive and the sign of the AC voltage is negative when the other is turned on. A power conversion device that performs power conversion from direct current to alternating current,
An insulation transformer having a primary side neutral point and a secondary side neutral point in each of the AC side primary side winding and the DC side secondary side winding;
An AC side first electric circuit from one output end on the AC side to the neutral point on the primary side;
A second AC circuit on the AC side that branches from the other output end on the AC side through the common circuit to the two circuits at the branch point and reaches both ends of the primary winding;
A reactor inserted in at least one of the AC side first electric circuit and the common electric circuit;
A first switch that can be energized in both directions and cuts off in both directions when switched off, and is inserted between the branch point and one end of the primary winding;
A second switch that can be energized in both directions and cuts off the current in both directions in a switch-off state, and is inserted between the branch point and the other end of the primary winding;
A third switch having one end connected to one end of the secondary winding;
A fourth switch having one end connected to the other end of the secondary winding;
A DC side first electric circuit connecting the other end of the third switch and the other end of the fourth switch to one input end on the DC side;
A DC side second electric circuit extending from the secondary side neutral point to the other input end on the DC side;
A switching operation for alternately turning on the third switch and the fourth switch is performed, and a switching operation for alternately turning on the first switch and the second switch is performed correspondingly. A control unit;
A power conversion device comprising: The control unit includes a voltage sensor that detects an AC voltage, a voltage sensor that detects a DC voltage, and a current sensor that detects a current flowing through the reactor,
The electric power according to any one of claims 1 to 7, wherein the control unit performs switching of the first switch and the second switch so that an alternating current synchronized with the alternating voltage flows through the reactor. Conversion device.   The power converter of any one of Claims 4-8 provided with the capacitor | condenser between both electric circuits of the edge part by the side of an alternating current.   The DC / DC converter according to any one of claims 1 to 6, further comprising a DC / DC converter that performs control such that an output voltage with respect to the load is constant between both electric circuits at the end portion on the direct current side and the load. Power conversion device.