JP2014003827A - Charging/discharging system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a charging/discharging system capable of preventing excessive ripple current from flowing into a capacitive element during charge of a power storage device, and preventing excessive surge voltage from applying to a switching element during discharge of the power storage device.SOLUTION: A charging/discharging system 1 performs a DC-AC conversion by a power conversion part 30 and an AC-DC conversion by a power conversion part 50 via a transformer 40, and supplies power to a power storage device 2 via a capacitive element 55 during a charge. While during a discharge, the system performs a DC-AC conversion by the power conversion part 50 and an AC-DC conversion by the power conversion part 30, and extracts power from the power storage device 2. The charging/discharging system 1 further has a charge auxiliary inductor element 70 and a discharge auxiliary part 80 between the power conversion part 50 and the capacitive element 55. An auxiliary switching element 81 of the discharge auxiliary part 80 is turned-on during discharge, at least in the period when all full-bridge type switching elements in the power conversion part 50 are turned-off.

Description

  The present invention relates to a charge / discharge system for charging a power storage device (for example, a battery) and making available electric power stored in the power storage device.

  As environmentally friendly vehicles, electric vehicles such as electric vehicles and hybrid vehicles have been put into practical use. In an electric vehicle, an in-vehicle battery can be charged from a power source (for example, a power outlet) outside the vehicle. For example, charging is performed by connecting a power outlet provided at home or a common facility to a charging port provided in the vehicle with a charging cable. On the other hand, plug-in hybrid vehicles that enable charging of an in-vehicle battery from a power source outside the vehicle have also been put to practical use.

  In recent years, it is expected that an in-vehicle battery is used not only as an in-vehicle device but also as a power source for movement, disaster, or emergency that supplies power to other electric devices, and the electric power stored in the in-vehicle battery is used in the vehicle. It is desired to be able to discharge through the charging port and the charging cable. That is, it is desired to mount a charge / discharge system capable of both charging and discharging on a vehicle. Patent Document 1 discloses a bidirectional converter as this type of charge / discharge system.

  The bidirectional converter 1 disclosed in Patent Document 1 includes an AC / DC converter 2 including an AC / DC converter 2A and a DC / DC converter 2B. The AC / DC conversion unit 2A includes a full-bridge circuit configured by switching elements SW21 to SW24 and a rectifying element, and a capacitor 25C. On the other hand, the DC / DC converter 2B includes a DC / AC converter composed of full-bridge switching elements SW31 to SW34 and a rectifier, a transformer 22, and full-bridge switching elements SW41 to SW44 and a rectifier. A configured AC / DC converter and a capacitor 26C are provided. In this bidirectional converter 1, during battery charging, the AC / DC converter 2A functions as a synchronous rectifier circuit having a PFC function, the DC / AC converters SW31 to SW34 function as inverter circuits, and the AC / DC converter SW41. ... SW44 functions as a rectifier circuit. On the other hand, when the battery is discharged, AC / DC converters SW41 to SW44 function as inverter circuits, DC / AC converters SW31 to SW34 function as rectifier circuits, and AC / DC converter 2A functions as an inverter circuit.

JP 2010-178666 A

  However, in the bidirectional converter 1 described in Patent Document 1, since the output of the AC / DC converters SW41 to SW44 is smoothed only by the capacitor 26C when the battery is charged, an excessive ripple current flows through the capacitor 26C, and the capacitor 26C May be damaged.

  Regarding this problem, it is conceivable to insert a choke coil between one of the outputs of the AC / DC converters SW41 to SW44 and the capacitor 26C. The choke coil acts so as to eliminate a change in the current flowing through the choke coil, so that an excessive ripple current can be prevented from flowing through the capacitor 26C during battery charging. However, when the battery is discharged, the energy of the choke coil cannot be properly stored / released, and the switching elements SW41 to SW44 of the AC / DC converter may be damaged. Specifically, in the full bridge circuit, it is necessary to provide a period during which all the switching elements SW41 to SW44 are turned off during switching of the switching elements SW41 to SW44 to prevent short circuit current. Since the voltage of the choke coil is reversed when there is no current flowing through the choke coil, an excessive surge voltage is applied to the switching elements SW41 to SW44 during a period in which all the switching elements SW41 to SW44 are turned off. There is a risk of damage.

  Therefore, the present invention can suppress an excessive ripple current from flowing through the capacitor element during charging of the power storage device, and suppress an excessive surge voltage from being applied to the switching element during discharging of the power storage device. It aims at providing the charging / discharging system which can be performed.

  The charging / discharging system of the present invention charges the power storage device connected to the second system input / output terminal pair by the power supplied to the first system input / output terminal pair, and uses the power stored in the power storage device for the first time. A charge / discharge system for discharging to one system input / output terminal pair, wherein: (a) a first input / output terminal pair electrically connected to the first system input / output terminal pair; and a second input / output terminal A pair, and during charging, the DC power supplied to the first input / output terminal pair is converted into AC power, and the AC power is output to the second input / output terminal pair. A first power converter that converts AC power supplied to the second input / output terminal pair into DC power and outputs the DC power to the first input / output terminal pair; and (b) first power. A transformer having a primary coil connected between the second input / output terminal pair of the converter; ) A first input / output terminal pair connected to the secondary coil of the transformer, a second input / output terminal pair electrically connected to the second system input / output terminal pair, and the second input / output First and second switching elements connected in series between a pair of terminals, the first and second switching elements having a node between them connected to one of the first input / output terminal pairs; Third and fourth switching elements connected in series between the second input / output terminal pair, and a node between them is connected to the other of the first input / output terminal pair. 4 switching elements and first to fourth rectifying elements connected in parallel to the first to fourth switching elements, respectively, and during charging, the first to fourth rectifying elements AC power supplied to the first input / output terminal pair is converted to DC power, and the DC power Is output to the second input / output terminal pair, and at the time of discharging, the first to fourth switching elements convert DC power supplied to the second input / output terminal pair into AC power. A second power converter that outputs power to the first input / output terminal pair; (d) a capacitive element electrically connected between the second input / output terminal pair of the second power converter; (E) a charge auxiliary inductor element connected between one of the second input / output terminal pair of the second power conversion unit and the capacitive element; and (f) a second input / output of the second power conversion unit. A discharge auxiliary unit connected between the pair of terminals, the auxiliary discharge unit having an auxiliary switching element and an auxiliary capacitance element connected in series; and (g) the auxiliary switching element of the discharge auxiliary unit At least all of the first to fourth switching elements of the second power conversion unit are off It becomes an ON state during the period.

  Note that “the switching element is turned on” means that the switching element is in a state where a current can flow (conduction state), and “the switching element is turned off” means that the switching element cuts off the current. It shows that it will be in a state (non-conduction state).

  According to this charging / discharging system, during charging, the charging auxiliary inductor element acts so as to eliminate a change in the current flowing to itself, so that it is possible to suppress an excessive ripple current from flowing through the capacitive element. Damage to the element can be avoided.

  On the other hand, at the time of discharging, since at least the auxiliary switching elements of the discharge assisting unit are in the on state during the period when all the first to fourth switching elements of the second power conversion unit are in the off state, Can continue to flow and the voltage of the charging auxiliary inductor element can be prevented from reversing. Therefore, it is possible to avoid applying an excessive surge voltage to the first to fourth switching elements of the second power conversion unit, and to avoid damage to these switching elements.

  The auxiliary switching element of the discharge auxiliary unit described above maintains the on state even during the period in which the first and fourth switching elements and the second and third switching elements of the second power conversion unit are alternately turned on. May be.

  The charging / discharging system described above is connected to the first input / output terminal pair electrically connected to the first system input / output terminal pair and the first input / output terminal pair of the first power conversion unit. A second input / output terminal pair, and at the time of charging, the AC power supplied to the first input / output terminal pair is converted into DC power, and the DC power is transferred to the second input / output terminal pair. A third power conversion unit that outputs and converts the DC power supplied to the second input / output terminal pair to AC power and outputs the AC power to the first input / output terminal pair during discharging. You may have.

  ADVANTAGE OF THE INVENTION According to this invention, it can suppress that an excessive ripple current flows into a capacitive element at the time of charge of an electrical storage apparatus, and suppresses that an excessive surge voltage is applied to a switching element at the time of discharge of an electrical storage apparatus. Can do.

It is a circuit diagram which shows the charging / discharging system which concerns on a 1st comparative example. It is a circuit diagram which shows the charging / discharging system which concerns on a 2nd comparative example. It is a circuit diagram which shows the charging / discharging system which concerns on a 3rd comparative example. 1 is a circuit diagram showing a charge / discharge system according to a first embodiment of the present invention. It is a figure which shows the state at the time of battery discharge of the auxiliary transistor of the discharge auxiliary | assistant part shown in FIG. 4, and the 1st-4th transistor of an AC / DC conversion part. FIG. 6 is a diagram illustrating current paths of a transformer, an AC / DC conversion unit, a choke coil, and a discharge auxiliary unit in a period Pa to Pf illustrated in FIG. 5. The collector-emitter voltage / current waveform of the first transistor of the AC / DC converter shown in FIG. 4, the voltage / current waveform of the primary coil of the transformer, and the voltage / current waveform of the first diode of the DC / AC converter shown in FIG. It is a figure which shows an example of the simulation result of a current waveform. FIG. 8 is a diagram illustrating current paths of the AC / DC conversion unit, the transformer, and the DC / AC conversion unit 30 in the periods Pa to Pd illustrated in FIG. 7. It is a circuit diagram which shows the charging / discharging system which concerns on the 2nd Embodiment of this invention. It is a figure which shows an example of the simulation result of the voltage and current waveform of the primary side coil of the transformer shown in FIG. It is a figure which shows the state at the time of battery charge of the auxiliary transistor of the charge auxiliary | assistant part shown in FIG. 9, and the 1st-4th transistor of an AC / DC conversion part. It is a figure which shows the current pathway of the AC / DC conversion part, choke coil, and charge auxiliary | assistant part in period Pa-Pf shown in FIG. It is a circuit diagram which shows the charging / discharging system which concerns on the modification of this invention.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals.

Before describing the preferred embodiment of the present invention, in order to facilitate understanding of the characteristics of the charge / discharge system according to the embodiment of the present invention, first, the present inventors have devised up to the present invention. The charge / discharge system according to the first to third comparative examples will be described.
[First Comparative Example]

  FIG. 1 is a circuit diagram showing a charge / discharge system according to a first comparative example. A charge / discharge system 1X of the first comparative example shown in FIG. 1 is mounted on an electric vehicle such as an electric vehicle or a plug-in hybrid vehicle, and charges and discharges an in-vehicle battery. The terminal pair T1, T2 is a charging port of the vehicle, and the second system input / output terminal pair T3, T4 is connected to the battery 2. When charging the battery, a power source external to the vehicle (for example, a power outlet provided at home or a common facility) is connected to the first system input / output terminal pair T1, T2 via a charging cable or the like. When the battery is discharged, AC power is generated at the first system input / output terminal pair T1, T2.

  The charge / discharge system 1X of the first comparative example includes a noise filter 10, an AC / DC converter (third power converter) 20, a capacitor 25, and a DC / AC converter (first power converter). ) 30, a transformer 40, an AC / DC converter (second power converter) 50, a capacitor 55, and a controller 60.

  The noise filter 10 is for removing noise of commercial AC power supplied to the first system input / output terminal pair T1, T2. The AC power from which noise has been removed is supplied to the first input / output terminal pair 20T1 and 20T2 of the AC / DC converter 20.

  The AC / DC converter 20 functions as a rectifier circuit having a PFC function when the battery is charged, and functions as an inverter circuit when the battery is discharged. The AC / DC converter 20 includes a capacitor 21, inductors 22a and 22b, first to fourth n-type transistors (switching elements) 23a to 23d, and first to fourth diodes (rectifier elements) 24a to 24d. Including a full bridge circuit. As the first to fourth transistors 23a to 23d, high power transistors such as IGBTs (Insulated Gate Bipolar Transistors) and MOSFETs (Metal-Oxide-Semiconductor Field Effect Transistors) can be used. In this embodiment, the case where IGBT is used as the 1st-4th transistors 23a-23d is illustrated.

  A capacitor 21 is connected between the first input / output terminal pair 20T1 and 20T2 of the AC / DC converter 20. One of the first input / output terminal pairs 20T1 is connected to the emitter of the first transistor 23a and the collector of the second transistor 23b via the inductor 22a, and the other of the first input / output terminal pairs. 20T2 is connected to the emitter of the third transistor 23c and the collector of the fourth transistor 23d via the inductor 22b.

  The collector of the first transistor 23a is connected to one of the second input / output terminal pairs 20T3, and the emitter of the first transistor 23a is connected to the collector of the second transistor 23b. The emitter of the second transistor 23b is connected to the other 20T4 of the second input / output terminal pair. Similarly, the collector of the third transistor 23c is connected to one of the second input / output terminal pairs 20T3, and the emitter of the third transistor 23c is connected to the collector of the fourth transistor 23d. The emitter of the fourth transistor 23d is connected to the other 20T4 of the second input / output terminal pair.

  The anodes of the first to fourth diodes 24a to 24d are connected to the emitters of the first to fourth transistors 23a to 23d, respectively. The cathodes of the first to fourth diodes 24a to 24d are respectively The first to fourth transistors 23a to 23d are connected to the collectors.

  The gates of the first to fourth transistors 23a to 23d are connected to the control unit 60, and the conduction state between the collector and the emitter in each of the first to fourth transistors 23a to 23d is provided from the control unit 60. Controlled by a control voltage (or control current).

  A capacitor 25 is electrically connected between the second input / output terminal pair 20T3 and 20T4 of the AC / DC converter 20. The second input / output terminal pair 20T3 and 20T4 of the AC / DC conversion unit 20 are connected to the first input / output terminal pair 30T1 and 30T2 of the DC / AC conversion unit 30, respectively.

  The AC / DC converter 30 functions as an inverter circuit when the battery is charged, and functions as a rectifier circuit when the battery is discharged. The AC / DC conversion unit 30 is configured by a full bridge circuit including first to fourth n-type transistors (switching elements) 31a to 31d and first to fourth diodes (rectifier elements) 32a to 32d. Yes. Note that high power transistors such as IGBTs and MOSFETs can be used as the first to fourth transistors 31a to 31d. In this embodiment, the case where IGBT is used as the 1st-4th transistors 31a-31d is illustrated.

  The collector of the first transistor 31a is connected to one of the first input / output terminal pair 30T1, and the emitter of the first transistor 31a is connected to the collector of the second transistor 31b. The emitter of the second transistor 31b is connected to the other 30T2 of the first input / output terminal pair. Similarly, the collector of the third transistor 31c is connected to one of the first input / output terminal pair 30T1, and the emitter of the third transistor 31c is connected to the collector of the fourth transistor 31d. The emitter of the fourth transistor 31d is connected to the other 30T2 of the first input / output terminal pair.

  The emitter of the first transistor 31a and the collector of the second transistor 31b are connected to one terminal of the primary side coil of the transformer 40, and the emitter of the third transistor 31c and the collector of the fourth transistor 31d are the transformer. 40 is connected to the other terminal of the primary coil.

  The anodes of the first to fourth diodes 32a to 32d are connected to the emitters of the first to fourth transistors 31a to 31d, respectively. The cathodes of the first to fourth diodes 32a to 32d are respectively The first to fourth transistors 31a to 31d are connected to the collectors.

  The gates of the first to fourth transistors 31a to 31d are connected to the control unit 60, and the conduction state between the collector and the emitter in each of the first to fourth transistors 31a to 31d is provided from the control unit 60. Controlled by a control voltage (or control current).

  Here, the ground potential of the electric device mounted on the vehicle is a floating potential, and it is necessary to insulate the power supply outside the vehicle from the in-vehicle battery 2. The transformer 40 is for insulating a power supply outside the vehicle and the in-vehicle battery 2. The secondary coil of the transformer 40 is connected to the first input / output terminal pair 50T1 and 50T2 of the AC / DC converter 50.

  The AC / DC converter 50 functions as a rectifier circuit when the battery is charged, and functions as an inverter circuit when the battery is discharged. The AC / DC converter 50 is configured by a full bridge circuit including first to fourth n-type transistors (switching elements) 51a to 51d and first to fourth diodes (rectifier elements) 52a to 52d. As the first to fourth transistors 51a to 51d, high power transistors such as IGBTs and MOSFETs can be used. In this embodiment, the case where IGBT is used as the 1st-4th transistors 51a-51d is illustrated.

  One of the first input / output terminal pairs 50T1 of the AC / DC converter 50 is connected to the emitter of the first transistor 51a and the collector of the second transistor 51b, and the other 50T2 of the first input / output terminal pair. Are connected to the emitter of the third transistor 51c and the collector of the fourth transistor 51d.

  The collector of the first transistor 51a is connected to one of the second input / output terminal pairs 50T3, and the emitter of the first transistor 51a is connected to the collector of the second transistor 51b. The emitter of the second transistor 51b is connected to the other 50T4 of the second input / output terminal pair. Similarly, the collector of the third transistor 51c is connected to one of the second input / output terminal pairs 50T3, and the emitter of the third transistor 51c is connected to the collector of the fourth transistor 51d. The emitter of the fourth transistor 51d is connected to the other 50T4 of the second input / output terminal pair.

  The anodes of the first to fourth diodes 52a to 52d are connected to the emitters of the first to fourth transistors 51a to 51d, respectively. The cathodes of the first to fourth diodes 52a to 52d are respectively The first to fourth transistors 51a to 51d are connected to the collectors.

  The gates of the first to fourth transistors 51a to 51d are connected to the control unit 60, and the conduction state between the collector and the emitter in each of the first to fourth transistors 51a to 51d is provided from the control unit 60. Controlled by a control voltage (or control current).

  A capacitor 55 is electrically connected between the second input / output terminal pair 50T3 and 50T4 of the AC / DC converter 50. Further, the second input / output terminal pair 50T3, 50T4 of the AC / DC converter 50 is connected to the second system input / output terminal pair T3, T4, respectively.

Next, the operation of the charge / discharge system 1X of the first comparative example will be described.
(When charging the battery)

  First, when the battery is charged, the AC / DC conversion unit 20 turns off the first and third transistors 23a and 23c, for example, and sets the second and fourth transistors 23b and 23d for each half cycle of the AC voltage. Are alternately controlled to convert AC power supplied to the first input / output terminal pair 20T1 and 20T2 into DC power, and this DC power is output to the second input / output terminal pair 20T3 and 20T4.

  At this time, in the half cycle in which the second transistor 23b is turned on and the fourth transistor 23d is turned off, the second transistor 23b is PWM-controlled so that the phase of the alternating voltage and the phase of the alternating current are matched. To do. Similarly, in the half cycle in which the second transistor 23b is turned off and the fourth transistor 23d is turned on, the fourth transistor 23d is subjected to PWM control so that the phase of the AC voltage and the phase of the AC current are matched. To do. Thereby, the AC / DC conversion unit 20 functions as a rectifier circuit having a PFC function.

  Next, the AC / DC conversion unit 30 functions as an inverter, and specifically controls switching between the first and fourth transistors 31a and 31d and the second and third transistors 31b and 31c alternately. Thus, the DC power supplied to the first input / output terminal pair 30T1 and 30T2 is converted into AC power, and this AC power is output to the second input / output terminal pair 30T3 and 30T4.

Next, the AC / DC converter 50 turns off the first to fourth transistors 51a to 51d, and supplies them to the first input / output terminal pairs 50T1 and 50T2 by the first to fourth diodes 52a to 52d. The AC power is converted into DC power, and this DC power is output to the second input / output terminal pair 50T3, 50T4.
(During battery discharge)

  On the other hand, when the battery is discharged, the AC / DC converter 50 functions as an inverter. Specifically, the first and fourth transistors 51a and 51d and the second and third transistors 51b and 51c are alternately arranged. By switching control, the DC power supplied to the second input / output terminal pair 50T3, 50T4 is converted into AC power, and this AC power is output to the first input / output terminal pair 50T1, 50T2.

  Next, the DC / AC conversion unit 30 turns off the first to fourth transistors 31a to 31d and supplies them to the second input / output terminal pair 30T3 and 30T4 by the first to fourth diodes 32a to 32d. The AC power to be converted is converted into DC power, and this DC power is output to the first input / output terminal pair 30T1 and 30T2.

  Next, the AC / DC converter 20 functions as an inverter, and specifically controls switching of the first and fourth transistors 23a and 23d and the second and third transistors 23b and 23c alternately. By doing so, the DC power supplied to the second input / output terminal pair 20T3, 20T4 is converted into AC power, and this AC power is output to the first input / output terminal pair 20T1, 20T2.

  In the charge / discharge system 1X of the first comparative example, the output of the AC / DC converter 50 is smoothed only by the capacitor 55 when the battery is charged. Therefore, an excessive ripple current flows through the capacitor 55 and the capacitor 55 may be damaged.

With regard to this problem, the inventors of the present application devise utilizing the current holding action of the choke coil as shown in the charge / discharge system 1Y of the second comparative example.
[Second Comparative Example]

  FIG. 2 is a circuit diagram showing a charge / discharge system according to a second comparative example. The charge / discharge system 1Y of the second comparative example shown in FIG. 2 is different from the charge / discharge system 1X of the first comparative example in that one of the second input / output terminal pair 50T3 of the AC / DC converter 50 and the capacitor 55 This is different from the first comparative example in that it further includes a choke coil (charging auxiliary inductor element) 70 connected therebetween.

  The choke coil 70 acts to eliminate a change in the current flowing through the choke coil 70. With this action, according to the charging / discharging system 1Y of the second comparative example, it is possible to suppress an excessive ripple current from flowing through the capacitor 55 during battery charging, and it is possible to avoid damage to the capacitor 55.

  However, when the battery is discharged, the energy of the choke coil 70 cannot be stored and released appropriately, and the first to fourth transistors 51a to 51d of the AC / DC converter 50 may be damaged. Specifically, in the full bridge circuit, it is necessary to provide a period in which all the transistors 51a to 51d are turned off during the on / off switching of the first to fourth transistors 51a to 51d in order to prevent a short-circuit current. Since the voltage of the choke coil 70 is reversed when the current flowing through the choke coil 70 disappears, an excessive surge voltage is applied to the transistors 51a to 51d during the period in which all the transistors 51a to 51d are turned off. 51d may be damaged.

With respect to this problem, the inventors of the present application devise provision of a bypass during battery discharge, as shown in the charge / discharge system 1Z of the third comparative example.
[Third comparative example]

  FIG. 3 is a circuit diagram showing a charge / discharge system according to a third comparative example. The charge / discharge system 1Z of the third comparative example shown in FIG. 3 is similar to the charge / discharge system 1Y of the second comparative example in that the first switch element 71 connected in series to the choke coil 70, the choke coil 70, and the first This is different from the second comparative example in that it further includes a bypass second switch element 72 connected in parallel to a series circuit of one switch element 71.

  According to the charge / discharge system 1Z of the third comparative example, when the battery is charged, the first switch element 71 is turned on and the second switch element 72 is turned off. On the other hand, when the battery is discharged, the first switch element 71 is turned off and the second switch element 72 is turned on to avoid the problem of the choke coil 70 described above. Can do. However, there are problems such as an increase in the number of parts, an increase in size, and a problem of a decrease in efficiency due to a constant loss occurring in any of these switch elements.

With regard to these problems, the inventors of the present application devise providing a discharge assisting unit 80 as shown in the charge / discharge system of the present embodiment.
[First Embodiment]

  FIG. 4 is a circuit diagram showing the charge / discharge system according to the first embodiment of the present invention. The charge / discharge system 1 of the first embodiment shown in FIG. 4 is connected between the second input / output terminal pair 50T3, 50T4 of the AC / DC converter 50 in the charge / discharge system 1Y of the second comparative example. The second comparative example is different from the second comparative example in that the discharge auxiliary unit 80 is further provided.

  The discharge auxiliary unit 80 includes an n-type auxiliary transistor 81 and an auxiliary capacitor 82 connected in series between the second input / output terminal pair 50T3 and 50T4. The discharge auxiliary unit 80 includes an auxiliary diode 83 connected in parallel to the auxiliary transistor 81. As the auxiliary transistor 81, a high power transistor such as IGBT or MOSFET can be used. In this embodiment, the case where IGBT is used as the auxiliary transistor 81 is illustrated.

  The emitter of the auxiliary transistor 81 is connected to one of the second input / output terminal pairs 50T3 of the AC / DC converter 50, and the collector of the auxiliary transistor 81 is connected to one terminal of the auxiliary capacitor 82. The other terminal of the auxiliary capacitor 82 is connected to the other 50T4 of the second input / output terminal pair of the AC / DC converter 50. The anode of the auxiliary diode 83 is connected to the emitter of the auxiliary transistor 81, and the cathode of the auxiliary diode 83 is connected to the collector of the auxiliary transistor 81. The gate of the auxiliary transistor 81 is connected to the control unit 60, and the conduction state between the collector and the emitter is controlled by a control voltage (or control current) provided from the control unit 60.

  FIG. 5 is a diagram illustrating a state of the auxiliary transistor 81 of the discharge auxiliary unit 80 and the first to fourth transistors 51a to 51d of the AC / DC conversion unit 50 during battery discharge. The high side indicates an on state, and the low side indicates an off state. 6A to 6F are diagrams showing current paths of the transformer 40, the AC / DC conversion unit 50, the choke coil 70, and the discharge auxiliary unit 80 in the periods Pa to Pf shown in FIG. .

  First, as shown in FIGS. 5 and 6A, in the period Pa, all of the first to fourth transistors 51 a to 51 d are turned on, and energy is accumulated in the choke coil 70. Thereafter, as shown in FIGS. 5 and 6B, in the period Pb, all of the first to fourth transistors 51a to 51d are temporarily turned off to prevent a short circuit current. At this time, by turning on the auxiliary transistor 81 and continuing to pass a current through the choke coil 70, the voltage of the choke coil 70 is avoided from being inverted, and an excessive surge voltage is applied to the first to fourth transistors 51a to 51d. Is prevented from being applied. At this time, energy is stored in the auxiliary capacitor 82. In the first partial period in the period Pb, the auxiliary diode 83 is used to hold current and store energy.

  After that, as shown in FIGS. 5 and 6C, in the period Pc, the first and fourth transistors 51a and 51d are turned on. In the present embodiment, the auxiliary transistor 81 is kept on even during the period Pc. Thus, energy accumulation in the auxiliary capacitor 82 is continued (current path I), and after the energy accumulated in the choke coil 70 is released, the energy accumulated in the auxiliary capacitor 82 can be released (current path II). ). Thereafter, as shown in FIGS. 5 and 6D, in the period Pd, all the first to fourth transistors 51a to 51d are temporarily turned off to prevent a short circuit current. At this time, the ON state of the auxiliary transistor 81 is maintained and the current is continuously supplied to the choke coil 70, thereby avoiding the inversion of the voltage of the choke coil 70, and the first to fourth transistors 51a to 51d being excessively large. Prevents surge voltage from being applied. At this time, energy is stored again in the auxiliary capacitor 82. Even in the first partial period in the period Pd, the auxiliary diode 83 can be used to hold current and store energy.

  After that, as shown in FIGS. 5 and 6E, in the period Pe, the second and third transistors 51b and 51c are turned on. In the present embodiment, the auxiliary transistor 81 is kept on even during the period Pe. Thus, energy accumulation in the auxiliary capacitor 82 is continued (current path I), and after the energy accumulated in the choke coil 70 is released, the energy accumulated in the auxiliary capacitor 82 can be released (current path II). ). After that, as shown in FIGS. 5 and 6 (f), in the period Pf, all the first to fourth transistors 51a to 51d are temporarily turned off to prevent a short circuit current. At this time, the ON state of the auxiliary transistor 81 is maintained and the current is continuously supplied to the choke coil 70, thereby avoiding the inversion of the voltage of the choke coil 70, and the first to fourth transistors 51a to 51d being excessively large. Prevents surge voltage from being applied. At this time, energy is stored again in the auxiliary capacitor 82. Even in the first partial period in the period Pf, the auxiliary diode 83 can be used to hold current and store energy. Thereafter, returning to the above-described period Pa, the operations in the periods Pa to Pf are repeated.

  Thus, according to the charging / discharging system 1 of the first embodiment, during battery discharge, discharging is performed during a period in which all of the first to fourth switching elements 51a to 51d of the AC / DC conversion unit 50 are in the off state. Since the auxiliary transistor 81 of the auxiliary unit 80 is in the ON state, and the auxiliary diode 83 is provided, it is possible to prevent the current from continuously flowing through the choke coil 70 and the voltage of the choke coil 70 from being inverted. Therefore, it is possible to avoid an excessive surge voltage from being applied to the first to fourth switching elements 51a to 51d of the AC / DC conversion unit 50, and to prevent the switching elements 51a to 51d from being damaged.

  Furthermore, according to the charging / discharging system 1 of the first embodiment, the number of parts can be reduced and the size can be reduced as compared with the charging / discharging system 1Z of the third comparative example. A decrease in efficiency due to the occurrence can be suppressed.

On the other hand, when charging the battery, the choke coil 70 acts so as to eliminate the change in the current flowing through itself, as in the charge / discharge system 1Y of the second comparative example described above, and therefore an excessive ripple current flows through the capacitor 55. This can be suppressed, and damage to the capacitor 55 can be avoided.
[Second Embodiment]

  By the way, in the charging / discharging system 1 of 1st Embodiment, adjustment of an output voltage is difficult at the time of battery discharge, and a desired alternating voltage might not be obtained. With regard to this problem, the inventors of the present application have found that the cause is that the rectified output voltage of the DC / AC conversion unit 30 becomes larger than the design value as a result of intensive studies. This cause will be described in detail below.

  7 shows the collector-emitter voltage / current waveform of the first transistor 51a of the AC / DC converter 50, the voltage / current waveform of the primary coil of the transformer 40, and the first of the DC / AC converter 30. It is a figure which shows an example of the simulation result of the voltage and current waveform of the diode 32a. FIG. 7 also shows the on / off states of the first and third transistors 51a and 51c of the AC / DC converter 50. 8A to 8D are diagrams showing current paths of the AC / DC conversion unit 50, the transformer 40, and the DC / AC conversion unit 30 in the periods Pa to Pd shown in FIG.

  According to FIG. 7, voltage remains in the primary side coil of the transformer 40 even when the first and fourth transistors 51a and 51d of the AC / DC converter 50 change from the on state to the off state in the period Tb. I understand that. Further, it can be seen that the collector-emitter voltage of the first transistor 51a of the AC / DC converter 50 and the terminal voltage of the first diode 52a of the DC / AC converter 30 are increased.

  Further, it can be seen that voltage remains in the primary coil of the transformer 40 even when the second and third transistors 51b and 51c of the AC / DC conversion unit 50 are turned off from the on state in the period Td. In addition, a voltage remains between the collector and the emitter of the first transistor 51a of the AC / DC conversion unit 50 and between the terminals of the first diode 52a of the DC / AC conversion unit 30 and gradually decreases. Recognize.

  From this, the inventors of the present application infer as follows.

  When the first and fourth transistors 51a and 51d of the AC / DC converter 50 are on during the period ta, the second and third transistors of the AC / DC converter 50 are turned on as shown in FIG. Energy is stored in the parasitic capacitances of the transistors 51b and 51c and the second and third diodes 52b and 52c. Further, energy is accumulated in the parasitic capacitances of the second and third transistors 31b and 31c and the second and third diodes 32b and 32c of the DC / AC conversion unit 30.

  After that, when the first and fourth transistors 51a and 51d are turned off in the period tb, as shown in FIG. 8B, the second and third transistors 51b, 51c, The energy accumulated in the parasitic capacitances of the second and third diodes 52b and 52c is discharged, and the parasitic capacitances of the first and fourth transistors 51a and 51d and the first and fourth diodes 52a and 52d. Current path A is formed when charging. By forming the current path A, a voltage remains in the primary coil of the transformer 40 and the capacitor 25 is charged.

  Further, the energy accumulated in the parasitic capacitances of the second and third transistors 31b and 31c and the second and third diodes 32b and 32c of the DC / AC converter 30 is discharged, and the first and fourth transistors A current path B is formed when the parasitic capacitances of the transistors 31a and 31d and the first and fourth diodes 32a and 32d are charged. By forming the current path B, the capacitor 25 is charged.

  Similarly, when the second and third transistors 51b and 51c of the AC / DC converter 50 are in the on state during the period tc, as shown in FIG. 8C, the first of the AC / DC converter 50 Energy is stored in the parasitic capacitances of the fourth transistors 51a and 51d and the first and fourth diodes 52a and 52d. Further, energy is stored in the parasitic capacitances of the first and fourth transistors 31a and 31d and the first and fourth diodes 32a and 32d of the DC / AC conversion unit 30.

  Thereafter, when the second and third transistors 51b and 51c are turned off in the period td, as shown in FIG. 8D, the first and fourth transistors 51a and 51d, The energy accumulated in the parasitic capacitances of the first and fourth diodes 52a and 52d is discharged, and the parasitic capacitances of the second and third transistors 51b and 51c and the second and third diodes 52b and 52c. Current path A is formed when charging. By forming the current path A, a voltage remains in the primary coil of the transformer 40 and the capacitor 25 is charged.

  Also, the energy accumulated in the parasitic capacitances of the first and fourth transistors 31a and 31d and the first and fourth diodes 32a and 32d of the DC / AC converter 30 is discharged, and the second and third transistors The current path B is formed when the parasitic capacitances of the transistors 31b and 31c and the second and third diodes 32b and 32c are charged. By forming the current path B, the capacitor 25 is charged.

  As described above, the capacitor 25 is charged also during the periods tb and td in which all the transistors 51a to 51d are turned off to prevent a short-circuit current. However, in the design, the capacitor 25 is not charged during these periods tb and td, and thus the rectified output voltage of the DC / AC converter 30 becomes larger than the design value. This is because the load of the rectifier circuit is the capacitor 25 and the inverter circuit (AC / DC converter 20) that consumes relatively little energy.

  In this regard, the inventors of the present invention devise using the energy storage action of the choke coil as described below.

  FIG. 9 is a circuit diagram showing a charge / discharge system according to the second embodiment of the present invention. The charge / discharge system 1A of the second embodiment shown in FIG. 9 is the same as the charge / discharge system 1 of the first embodiment in that it further includes a choke coil (discharge auxiliary inductor element) 70A and a charge auxiliary unit 80A. This is different from the embodiment.

  The choke coil 70 </ b> A is connected between the first input / output terminal pair 30 </ b> T <b> 1 of the DC / AC conversion unit 30 and the capacitor 25.

  Further, the auxiliary charging unit 80A is connected between the first input / output terminal pair 30T1 and 30T2 of the AC / DC conversion unit 30. The charging auxiliary unit 80A includes an n-type auxiliary transistor 81A and an auxiliary capacitor 82A connected in series between the first input / output terminal pair 30T1 and 30T2 of the AC / DC conversion unit 30. The auxiliary charging unit 80A includes an auxiliary diode 83A connected in parallel to the auxiliary transistor 81A. As the auxiliary transistor 81A, a high power transistor such as an IGBT or a MOSFET can be used. In the present embodiment, a case where an IGBT is used as the auxiliary transistor 81A is illustrated.

  The emitter of the auxiliary transistor 81A is connected to one of the first input / output terminal pairs 30T1 of the AC / DC conversion unit 30, and the collector of the auxiliary transistor 81A is connected to one terminal of the auxiliary capacitor 82A. The other terminal of the auxiliary capacitor 82A is connected to the other 30T2 of the first input / output terminal pair of the AC / DC converter 30. The anode of the auxiliary diode 83A is connected to the emitter of the auxiliary transistor 81A, and the cathode of the auxiliary diode 83A is connected to the collector of the auxiliary transistor 81A. The gate of the auxiliary transistor 81A is connected to the control unit 60, and the conduction state between the collector and the emitter is controlled by a control voltage (or control current) provided from the control unit 60.

  Next, the energy storage action of the choke coil 70A will be described. FIG. 10 is an example of a simulation result corresponding to FIG. 7 described above, and is a diagram illustrating a voltage / current waveform of the primary side coil of the transformer 40.

  According to FIG. 10, during the period Tb, when the first and fourth transistors 51a and 51d of the AC / DC conversion unit 50 change from the on state to the off state, a voltage remains in the primary side coil of the transformer 40. It turns out that it is suppressed. In addition, during the period Td, when the second and third transistors 51b and 51c of the AC / DC conversion unit 50 are turned from the on state to the off state, the voltage on the primary side coil of the transformer 40 is suppressed. I understand that. This is because the energy remaining in the primary coil of the transformer 40 is accumulated in the choke coil 70A.

  In this way, the choke coil 70A acts so as to accumulate energy supplied to the capacitor 25 through the current paths A and B described above. Therefore, according to the charging / discharging system 1A of the second embodiment, it is possible to prevent the capacitor 25 from being charged during the periods tb and td in which all the transistors 51a to 51d are turned off to prevent a short-circuit current. it can. As a result, it is possible to suppress the rectified output voltage of the DC / AC conversion unit 30 from becoming larger than the design value, and it is possible to adjust the output voltage of the charge / discharge system during battery discharge.

  However, when the battery is charged, the energy of the choke coil 70 </ b> A cannot be appropriately stored and released, and the first to fourth transistors 31 a to 31 d of the AC / DC conversion unit 30 may be damaged. Specifically, during the period when all the transistors 31a to 31d are turned off to prevent a short circuit current, the voltage of the choke coil 70A is inverted, and an excessive surge voltage is applied to these transistors 31a to 31d. The transistors 31a to 31d may be damaged.

  Regarding this problem, the charging / discharging system 1A of the present embodiment includes a charging auxiliary unit 80A. FIG. 11 is a diagram illustrating a state of the auxiliary transistor 81A of the auxiliary charging unit 80A and the first to fourth transistors 31a to 31d of the AC / DC conversion unit 30 during battery charging. The high side indicates an on state, and the low side indicates an off state. 12A to 12F are diagrams illustrating current paths of the AC / DC conversion unit 30, the choke coil 70A, and the auxiliary charging unit 80A in the periods Pa to Pf shown in FIG.

  First, as shown in FIGS. 11 and 12A, in the period Pa, all of the first to fourth transistors 31a to 31d are turned on, and energy is accumulated in the choke coil 70A. After that, as shown in FIGS. 11 and 12B, in the period Pb, all the first to fourth transistors 31a to 31d are temporarily turned off to prevent a short circuit current. At this time, by turning on the auxiliary transistor 81A and continuing to flow current through the choke coil 70A, the voltage of the choke coil 70A is prevented from being inverted, and an excessive surge voltage is applied to the first to fourth transistors 31a to 31d. Is prevented from being applied. At this time, energy is stored in the auxiliary capacitor 82A. In the first partial period in the period Pb, the auxiliary diode 83A is used to hold current and store energy.

  After that, as shown in FIGS. 11 and 12C, in the period Pc, the first and fourth transistors 31a and 31d are turned on. In the present embodiment, the auxiliary transistor 81A is kept on even during the period Pc. Thereby, energy accumulation in the auxiliary capacitor 82A is continued (current path I), and after the energy accumulated in the choke coil 70A is released, the energy accumulated in the auxiliary capacitor 82A can be released (current path II). ). Thereafter, as shown in FIGS. 11 and 12D, in the period Pd, all the first to fourth transistors 31a to 31d are temporarily turned off to prevent a short circuit current. At this time, by keeping the ON state of the auxiliary transistor 81A and continuing to pass a current through the choke coil 70A, the voltage of the choke coil 70A is avoided from being inverted, and the first to fourth transistors 31a to 31d are excessively large. Prevents surge voltage from being applied. At this time, energy is stored again in the auxiliary capacitor 82A. Even in the first partial period in the period Pd, the auxiliary diode 83A can be used to hold current and store energy.

  After that, as shown in FIGS. 11 and 12E, in the period Pe, the second and third transistors 31b and 31c are turned on. In the present embodiment, the auxiliary transistor 81A is kept on even during the period Pe. Thereby, energy accumulation in the auxiliary capacitor 82A is continued (current path I), and after the energy accumulated in the choke coil 70A is released, the energy accumulated in the auxiliary capacitor 82A can be released (current path II). ). After that, as shown in FIGS. 11 and 12 (f), in the period Pf, all the first to fourth transistors 31a to 31d are temporarily turned off to prevent a short circuit current. At this time, by keeping the ON state of the auxiliary transistor 81A and continuing to pass a current through the choke coil 70A, the voltage of the choke coil 70A is avoided from being inverted, and the first to fourth transistors 31a to 31d are excessively large. Prevents surge voltage from being applied. At this time, energy is stored again in the auxiliary capacitor 82A. Even in the first partial period in the period Pf, the auxiliary diode 83A can be used to hold current and store energy. Thereafter, returning to the above-described period Pa, the operations in the periods Pa to Pf are repeated.

  As described above, according to the charging / discharging system 1A of the second embodiment, during battery charging, during the period in which all of the first to fourth transistors 31a to 31d of the AC / DC conversion unit 30 are in the off state, charging assistance is performed. Since the auxiliary transistor 81A of the section 80A is turned on and the auxiliary diode 83A is provided, it is possible to prevent the current from continuously flowing through the choke coil 70A and the voltage of the choke coil 70A from being inverted. Therefore, it is possible to avoid an excessive surge voltage from being applied to the first to fourth transistors 31a to 31d of the AC / DC converter 30, and to avoid damage to the first to fourth transistors 31a to 31d. it can.

  The present invention is not limited to the above-described embodiment, and various modifications can be made. For example, in the present embodiment, not only the periods Pb, Pd, and Pf in which all of the first to fourth transistors 51a to 51d of the AC / DC conversion unit 50 are turned off during battery discharge, but also the first and fourth The auxiliary transistor 81 of the auxiliary discharge unit 80 is kept in the ON state during the period Pc in which the transistors 51a and 51d are in the ON state and the periods Pc and Pe in which the second and third transistors 51b and 51c are in the ON state. The auxiliary transistor 81 only needs to be in the on state during the periods Pb, Pd, and Pf in which all the first to fourth transistors 51a to 51d are in the off state.

  Similarly, in the second embodiment, during battery discharge, not only the periods Pb, Pd, and Pf in which all the first to fourth transistors 31a to 31d of the AC / DC conversion unit 30 are off, The auxiliary transistor 81A of the auxiliary charge unit 80A is also kept on during the period Pc when the fourth transistors 31a and 31d are on and the periods Pc and Pe when the second and third transistors 31b and 31c are on. However, the auxiliary transistor 81A only needs to be in the on state during the periods Pb, Pd, and Pf in which all of the first to fourth transistors 31a to 31d are in the off state.

  In the present embodiment, the AC / DC converter (third power converter) 20, the DC / AC converter (first power converter) 30, and the AC / DC converter (second power converter) The charge / discharge system that performs AC / DC conversion is illustrated. However, as shown in FIG. 13, the feature of the present invention is that the DC / AC converter (first power converter) 30 and the AC / DC The present invention is also applicable to a charge / discharge system 1B that includes a conversion unit (second power conversion unit) and performs DC / DC conversion. This type of DC / DC conversion type charging / discharging system is applied to, for example, quick charging (charging) or connecting an in-vehicle battery to a PCS that cooperates with a system power supply (commercial power supply) (discharge). It is being considered.

  In the present embodiment, the method of charging the in-vehicle battery by connecting the power source outside the vehicle and the charging port of the vehicle with the charging cable is exemplified, but the feature of the present invention is not limited to this method. For example, in recent years, a non-contact charging method that does not use a charging cable has attracted attention. The charge / discharge system of the present invention is also applicable to such a non-contact charging method. In this case, the secondary side of the transformer may be mounted on the vehicle and the primary side may be provided outside the vehicle.

  Further, in the present embodiment, a large power charge / discharge system that charges and discharges an in-vehicle battery or the like is illustrated, but the present invention is also applicable to a small power charge / discharge system that charges and discharges a battery such as a portable terminal. .

  1, 1A, 1B, 1X, 1Y, 1Z ... charge / discharge system, T1, T2 ... first system input / output terminal pair, T3, T4 ... second system input / output terminal pair, 2 ... battery (power storage device), DESCRIPTION OF SYMBOLS 10 ... Noise filter, 20 ... AC / DC converter (3rd power converter), 20T1, 20T2 ... 1st input / output terminal pair, 20T3, 20T4 ... 2nd input / output terminal pair, 21 ... Capacitor, 22a , 22b ... inductor, 23a-23d ... first to fourth transistors, 24a-24d ... first to fourth diodes, 25 ... capacitor, 30 ... DC / AC converter (first power converter), 30T1 , 30T2 ... first input / output terminal pair, 30T3, 30T4 ... second input / output terminal pair, 31a-31d ... first to fourth transistors, 32a-32d ... first to fourth diodes, 40 ... transistor 50T1, 50T2 ... First input / output terminal pair, 50T3, 50T4 ... Second input / output terminal pair, 51a-51d ... First to fourth Transistors (first to fourth switching elements), 52a to 52d ... first to fourth diodes (first to fourth rectifier elements), 55 ... capacitor (capacitance element), 60 ... control unit, 70 ... Choke coil (charge auxiliary inductor element), 70A ... choke coil (discharge auxiliary inductor element), 71, 72 ... switch element, 80 ... discharge auxiliary part, 81 ... auxiliary transistor (auxiliary switching element), 82 ... auxiliary capacitor (auxiliary capacitor) Element), 83 ... auxiliary diode (auxiliary rectifying element), 80A ... charge auxiliary section, 81A ... auxiliary transistor (auxiliary switching element), 82A ... auxiliary condenser (Auxiliary capacity element), 83A ... auxiliary diode (auxiliary rectifier element).

Claims (3)

The power storage device connected to the second system input / output terminal pair is charged by the power supplied to the first system input / output terminal pair, and the power stored in the power storage device is used as the first system input / output terminal. A charge / discharge system that discharges to a pair,
A first input / output terminal pair electrically connected to the first system input / output terminal pair; and a second input / output terminal pair, which are supplied to the first input / output terminal pair during charging. The direct current power is converted into alternating current power, and the alternating current power is output to the second input / output terminal pair. At the time of discharging, the alternating current power supplied to the second input / output terminal pair is converted into direct current power. A first power converter that outputs the DC power to the first input / output terminal pair;
A transformer having a primary coil connected between a second input / output terminal pair of the first power converter;
A first input / output terminal pair connected to the secondary coil of the transformer, a second input / output terminal pair electrically connected to the second system input / output terminal pair, and the second input / output terminal pair. First and second switching elements connected in series between the output terminal pair, and a node between the first and second switching elements connected to one of the first input / output terminal pairs; , Third and fourth switching elements connected in series between the second input / output terminal pair, and a node between the third and fourth switching elements connected to the other of the first input / output terminal pair It has a fourth switching element and first to fourth rectifying elements connected in parallel to the first to fourth switching elements, respectively, and at the time of charging, by the first to fourth rectifying elements, AC power supplied to the first input / output terminal pair is converted to DC power to Electric power is output to the second input / output terminal pair, and at the time of discharging, the first to fourth switching elements convert DC power supplied to the second input / output terminal pair into AC power, A second power converter that outputs AC power to the first input / output terminal pair;
A capacitive element electrically connected between the second input / output terminal pair of the second power converter;
A charge auxiliary inductor element connected between one of the second input / output terminal pair of the second power conversion unit and the capacitive element;
A discharge auxiliary unit connected between the second input / output terminal pair of the second power conversion unit, the auxiliary discharge unit having an auxiliary switching element and an auxiliary capacitance element connected in series;
With
The auxiliary switching element of the discharge auxiliary unit is turned on at least during a period in which all of the first to fourth switching elements of the second power conversion unit are turned off.
Charge / discharge system. The auxiliary switching element of the discharge auxiliary unit remains on even during a period in which the first and fourth switching elements and the second and third switching elements of the second power conversion unit are alternately turned on. To
The charge / discharge system according to claim 1.   A first input / output terminal pair electrically connected to the first system input / output terminal pair, and a second input / output terminal connected to the first input / output terminal pair of the first power conversion unit A pair, and during charging, the AC power supplied to the first input / output terminal pair is converted to DC power and the DC power is output to the second input / output terminal pair. 3. A third power converter that converts direct current power supplied to the second input / output terminal pair into alternating current power and outputs the alternating current power to the first input / output terminal pair. The charge / discharge system according to 1.

Images