JP5661075B2 - Charge / discharge device - Google Patents

Description

  The present invention relates to a charge / discharge device that performs bidirectional power conversion between a power system and a power storage device.

  2. Description of the Related Art Electric vehicles (EV) and plug-in hybrid electric vehicles (PHEV), which have been spreading in recent years, charge a battery (power storage device) mounted from a commercial power source such as a home. In addition, as a technique using EV or PHEV, a technique for discharging power storage devices and supplying power to a load (home appliance) in an emergency such as a commercial power supply being interrupted is being studied (for example, Patent Document 1). ).

  In addition, the number of households that introduce solar power generation systems is increasing, and Patent Document 2 discloses an operation of charging a power storage device with power supplied from a commercial power source and power generated by solar power generation and discharging from the power storage device. A power conversion device capable of converting the direct-current power to be converted into alternating-current power and supplying it to a load is described. Patent Document 3 discloses a photovoltaic power generation capable of simultaneously performing a parallel operation between a power supply system using a photovoltaic power generation and a commercial power supply and charging a power storage device by the photovoltaic power generation while performing maximum power tracking control on the solar battery. The system is described.

JP 2008-312395 A JP-A-6-113482 Japanese Patent Laid-Open No. 10-31525

  In the future, EVs and PHEVs will become more widespread and the number of vehicle types will increase, but it is predicted that the specifications of power storage devices mounted on vehicles will not necessarily be unified. In particular, when manufacturers are different, there is a high possibility that the electrical specifications (voltage, capacity, etc.) of the power storage devices to be mounted are also different. Therefore, when a new vehicle is purchased, the specifications of the newly purchased power storage device of the vehicle and the power storage device of the previously owned vehicle are different, and the charging device may have to be newly purchased. From the user's point of view, it is costly to purchase a dedicated charging device each time a vehicle is replaced and install it in a garage or the like. Moreover, since the removal work and installation work of a charging device involve a danger, it is necessary to request a specialized worker and is complicated. When replacing with a vehicle of the same manufacturer, there is a possibility that the charging device that has been used until then can be used continuously, but when purchasing a vehicle on the assumption that the charging device will continue to be used, the vehicle to be purchased The selection range is limited.

  For this reason, it is considered necessary to have a charging device that can handle a plurality of types of power storage devices, but the charging device for power storage devices mounted on EVs or PHEVs is an isolated DC / DC converter on the input side (AC side). And the output side (DC side) must be insulated. Therefore, when realizing a charging device that can handle a plurality of types of power storage devices (a wide range of voltages), an insulation transformer corresponding to the voltage range of the power storage device to be charged is required, which increases the size of the device. There is.

  This invention is made | formed in view of the above, Comprising: It aims at obtaining the charging / discharging apparatus which can be compatible with the size reduction of an apparatus and the response | compatibility to a wide range of voltage.

  In order to solve the above-described problems and achieve the object, the present invention is a charging / discharging device that performs bidirectional power conversion between a system power source and a power storage device, and that receives AC power input from the system power source. A first power conversion unit capable of performing an operation of converting to DC power and an operation of converting DC power input from the power storage device side to AC power; and an insulation transformer; and from the first power conversion unit A second power conversion unit that converts the input voltage from the power storage device side or the input voltage from the power storage device side at a constant conversion ratio, and the input voltage from the second power conversion unit or the input voltage from the power storage device to the power storage And a third power converter that converts at a conversion ratio based on the voltage across the device.

  According to the present invention, it is possible to reduce the size of the device by avoiding an increase in size of the insulating transformer, and to realize a charge / discharge operation for a plurality of types of power storage devices having different electrical specifications. Play.

FIG. 1 is a circuit block diagram illustrating a configuration example of the charge / discharge device according to the first embodiment. FIG. 2 is a circuit block diagram showing another configuration example of the charge / discharge device according to the first embodiment. FIG. 3 is a circuit block diagram illustrating another configuration example of the charge / discharge device according to the first embodiment. FIG. 4 is a circuit block diagram illustrating a configuration example of the charge / discharge device according to the second embodiment.

  Embodiments of a charge / discharge device according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
1 is a circuit block diagram showing a configuration example of a first embodiment of a charge / discharge device according to the present invention. The charging / discharging device of the present embodiment includes a grid interconnection inverter 2, an insulation type DC / DC converter 3, and a step-up / step-down DC / DC converter 4 as main components. This charging / discharging device converts the AC power supplied from the system power supply 1 into a DC voltage to charge the storage battery 5 and the DC power discharged from the storage battery 5 during AC power outage, etc. A discharging operation for converting to electric power and supplying it to an in-house load or the like (not shown) is performed. The storage battery 5 is a power storage device mounted on an EV or PHEV, and the charge / discharge device of the present embodiment is capable of charging and discharging operations for a plurality of types of power storage devices having different voltages. The grid interconnection inverter 2, the insulation type DC / DC converter 3 and the step-up / step-down DC / DC converter 4 drive the switching element according to the drive signal output from the control unit 10 and input through the drive units 11a to 11d. Perform power conversion.

  The grid interconnection inverter 2 is a first power conversion unit, operates according to a drive signal from the drive unit 11d, and performs a process of flowing power from the system power supply 1 toward the isolated DC / DC converter 3 or an isolated DC. A process for causing power to flow from the DC converter 3 to the system power supply 1 side is executed.

  The insulation type DC / DC converter 3 is a second power conversion unit, and includes single phase inverters 21 and 22 and an insulation transformer 6. The single-phase inverter 21 operates according to the drive signal from the drive unit 11c, and the single-phase inverter 22 operates according to the drive signal from the drive unit 11b. This insulated DC / DC converter 3 can be provided with bidirectionality by providing the single-phase inverters 21 and 22, and the power flow is charging the storage battery 5 of the single-phase inverter 21 → the insulation transformer 6 → the single-phase inverter 22. The direction and the discharge direction of the storage battery 5 of the single-phase inverter 22 → the insulation transformer 6 → the single-phase inverter 21 can be controlled. In addition, since the bidirectional converter is constituted by the single-phase inverters 21 and 22, it is possible to realize both step-up and step-down with a bidirectional power flow. In other words, V1> V2 (step-down) and V1 <V2 (step-up) can be controlled in the charging direction of the storage battery 5 with respect to the voltage V1 across the capacitor 7 and the voltage V2 across the capacitor 8, and V1 in the discharging direction. > V2 (step-up) and V1 <V2 (step-down) both mean that controllable four-quadrant operation is possible.

  The step-up / step-down DC / DC converter 4 is a third power converter, and operates according to a drive signal from the drive unit 11a. The step-up / step-down DC / DC converter 4 operates as a step-down converter when charging the storage battery 5 and as a step-up converter when discharging. That is, the circuit is a pair of a step-down chopper during charging and a step-up chopper during discharging.

  In the charging / discharging device of the present embodiment, it is important to provide two DC / DC converters that can step up and down the voltage. In other words, an insulation type DC / DC converter 3 and a step-up / step-down DC / DC converter 4 are provided. The insulation type DC / DC converter 3 can freely realize step-up / step-down if the insulation transformer 6 is an ideal transformer. However, in the transformer, the magnetic flux density is determined by the flowing current and the step-up / step-down ratio, and there is a possibility of magnetic saturation if the current and the step-up / step-down ratio exceed a predetermined value. Therefore, when dealing with a wide range of current ranges and step-up / step-down ratios, it is necessary to design a large size so that the transformer does not saturate. Therefore, in the charging / discharging device of the present embodiment, the voltage is stepped up or stepped down by the step-up / step-down DC / DC converter 4 to be converted into a desired voltage, and the step-up / step-down step is performed in the isolated DC / DC converter 3. Is constant (value close to 1). As a result, the insulation transformer 6 can be prevented from becoming larger than necessary, and the apparatus can be downsized.

  The storage battery 5 is generally a lithium ion battery, but is about 3 to 4 V per battery cell. For example, if battery cells of 3.7V / cell are connected in series, the battery voltage will be 355.2V. Since the battery voltage has different design specifications such as the amount of stored electricity, life, and temperature management depending on the manufacturer, the number of battery cells changes. Since the battery voltage per cell varies from manufacturer to manufacturer, the battery voltage generated at both ends of the storage battery can be low, around 200V, and high can exceed 400V. It is required to respond.

  When the isolated DC / DC converter 3 and the step-up / step-down DC / DC converter 4 discharge 3 kW of power from the storage battery 5 at the same step-up ratio, if the storage battery 5 has a battery voltage of 200 V, a current of 15 A is required. Assuming 400V, a current of 7.5A is required. Since the magnetic flux density is proportional to the current, if the battery voltage changes by half, the magnetic flux density excited by the insulating transformer also changes by half and the transformer outer shape changes greatly.

  When the storage battery 5 to be connected is not uniquely determined, for example, when there is a difference in the number of battery cells depending on the vehicle type or vehicle manufacturer, such as an electric vehicle, the battery voltage varies if the charger is highly public. Even if the transformer is increased in size according to the width of the range, it will not be a big problem. However, when installing in a general household, it is difficult to install a charger / discharger that covers all the specifications of the world despite having only one or several electric vehicles. Although it is also expected that the size and weight will be higher and the cost will be higher than the one that is dedicated to the vehicle type, repurchasing when replacing the vehicle not only increases the inconvenience for the user but also contributes to the global environment Not good. For this reason, in this embodiment, two DC / DC converters capable of boosting and lowering the voltage are provided, and the isolated DC / DC converter 3 maximizes power transmission, and the insulating transformer 6 is reduced in size. Therefore, the boosted voltage is transmitted. Thereby, charging / discharging for the storage battery 5 of various specifications can be performed while avoiding an increase in size and weight of the apparatus.

  The grid interconnection inverter 2 performs an operation of taking in or outputting power from the grid power supply 1. When the system power supply 1 is 200 V, the controllability is poor unless the DC voltage of the grid-connected inverter 2 or the voltage across the smoothing capacitor 7 is higher than 200 V × √2, and the power flow cannot be controlled. Therefore, it is desirable that this DC voltage be about 350 to 400V. Therefore, the DC voltage on the system power supply 1 side of the insulated DC / DC converter 3 is designed by the system interconnection inverter 2. Further, if maximum power transmission is performed for both charging and discharging, the step-up ratio = 1 can make the insulating transformer 6 most compact, and the power transmission amount during charging and discharging can be maximized.

  Therefore, the step-up / step-down DC / DC converter 4 may perform step-down when charging and step-up when discharging. The conversion ratio (step-down ratio and step-up ratio) in the step-up / step-down DC / DC converter 4 is changed according to the specifications of the connected storage battery 5 and the conversion ratio in the isolated DC / DC converter 3. When the storage battery 5 includes a BMC (Battery Management Controller) and the control unit 10 and the storage battery 5 can communicate with each other, the control unit 10 communicates with the BMC to grasp the specification of the storage battery 5, and the step-down ratio or step-up according to the specification The step-up / step-down DC / DC converter 4 is controlled so as to obtain the ratio. When the control unit 10 and the storage battery 5 cannot communicate with each other, for example, when the storage battery 5 is connected and an operation designation (whether the storage battery 5 is charged or discharged) is performed by the user, the specifications of the storage battery 5 ( Information for determining the step-down ratio and the step-up ratio (for example, voltage at both ends) is inquired and inputted to the user, and the specification is grasped. The conversion ratio may be determined by grasping the specifications of the storage battery 5 by other methods. By setting the conversion ratio in the insulated DC / DC converter 3 in advance, the voltage output from the insulated DC / DC converter 3 when the storage battery 5 is charged, and the insulated DC / DC converter 3 when the storage battery 5 is discharged. In order to uniquely determine the voltage to be input to the control unit 10, when the storage battery 5 is charged, the control unit 10 steps down and outputs the input voltage from the insulated DC / DC converter 3 to the voltage across the storage battery 5. At the time of discharging, the step-up / step-down DC / DC converter 4 can be controlled so that the input voltage from the storage battery 5 is boosted to a voltage to be input to the isolated DC / DC converter 3 and output.

  When the voltage across the storage battery 5 exceeds 400 V, if the voltage across the capacitor 7 is controlled to be equal to or higher than the voltage across the storage battery 5, only the current passing through the insulating transformer 6 is reduced, and magnetic flux saturation of the transformer occurs. Thus, it is possible to transmit more than the maximum amount of power transmission assumed. However, it goes without saying that it is less than the breakdown voltage of the transformer.

  1 shows a configuration in which the isolated DC / DC converter 3 is realized by two single-phase inverters 21 and 22. However, as shown in FIG. 2, two three-phase inverters 21a and 22a are provided. You may make it comprise with. In FIG. 2, the drive units 11b and 11c in FIG. 1 are replaced with drive units 11e and 11f that generate drive signals for the three-phase inverters 21a and 22a. When the insulation type DC / DC converter 3 is constituted by two three-phase inverters, the insulation transformer 6b is constituted by Y-Y connection, Y-Δ connection, or Δ-Δ connection. Although not shown in the figure, the insulated DC / DC converter 3 may be constituted by a single-phase inverter on one side and a three-phase inverter on the other side. In this case, the insulating transformer can be realized by using Scott connection. In either case, the voltage conversion is configured with a 1: 1 step-up ratio so that the minimum shape of the insulating transformer that can maximize the transmission power is obtained. As a result, the same power for charging and discharging can be secured by the same size of the insulating transformer. The voltage conversion ratio need not be 1: 1.

  In FIG. 1 and FIG. 2, since the isolated DC / DC converter 3 is insulated via an insulation transformer, the single-phase inverters 21 and 22 or the three-phase inverters 21a and 22a have different reference potentials and have the same control unit. The operation signal from 10 (so-called PWM gate signal) also needs to be insulated. 1 and 2 include drive units (drive units 11b, 11c, 11e, and 11f), which insulate operation signals. Even if the insulation of the operation signal is realized by a method other than this, it is needless to say that an effect equivalent to that of the present embodiment is brought about.

  Further, by using a wide band gap semiconductor such as SiC to increase the frequency, the insulating transformer 6 can be further reduced in size and reduced in weight. By downsizing, for example, when the storage battery 5 is mounted on an electric vehicle, it is possible to install a small charge / discharge device in the parking lot and prevent the dwelling interior from being damaged. If it can be installed in a parking lot, the routed distance of the insulated power line can be shortened, the probability of a ground fault can be reduced, and the reliability can be improved.

  As shown in FIG. 3, the insulation transformer 6 may be provided on the AC side. In this case, since the insulation transformer 6 has a power supply frequency and increases in size, the insulation constituted by the insulation type DC / DC converter 3 as shown in FIGS. Then it becomes advantageous. However, in the case of the configuration shown in FIG. 3, the number of semiconductor elements is small, and the operation reliability can be improved. Furthermore, since the potentials are the same, it is possible to reduce the number of parts for insulating the operation signal, and it is possible to reduce signal transmission delay and variation due to the insulation. Thereby, controllability is improved and the operating frequency (carrier frequency) can be improved.

  The grid-connected inverter 2 connected to the grid power supply 1 is a single-phase inverter (4-element configuration) in the configurations of FIGS. 1 to 3, but may be a 3-phase inverter having a 6-element configuration (illustration is omitted). ). In the case of a single-phase inverter, it becomes a single-phase two-wire output, but in the case of a three-phase inverter, a single-phase three-wire output can also be made, and it can be applied to a three-phase power source. Also, a circuit configuration in which capacitors connected in series with a single-phase inverter configuration are connected in parallel may be used. With this configuration, a single-phase three-wire output can be realized.

  Thus, the charging / discharging device of the present embodiment includes a grid interconnection inverter 2 having a function of flowing power in the direction (forward direction) from the system power supply 1 side to the storage battery 5 side and a function of flowing power in the opposite direction. An isolated DC / DC converter 3 that performs forward and reverse voltage conversion with a fixed voltage conversion ratio (eg, 1: 1), and a step-up / step-down DC / DC converter that steps down the forward direction and boosts the reverse direction 4 and the step-up / step-down DC / DC converter 4 steps down or boosts the power at a conversion ratio according to the specifications of the connected storage battery 5. This makes it possible to charge and discharge a plurality of types of storage batteries 5 having different electrical specifications while avoiding an increase in the size of the insulated DC / DC converter 3. As a result, it is possible to avoid a new purchase of a charging device (charging / discharging device) when replacing an electric vehicle or a plug-in hybrid car, and to keep costs low. In addition, it is possible to reduce the installation space of the charging / discharging device that can handle a plurality of types of storage batteries 5. Since the power output from the storage battery 5 can be converted into the power supplied to the home load, the home battery can be used using the storage battery 5 when the system power supply 1 fails.

Embodiment 2. FIG.
FIG. 4 is a circuit block diagram illustrating a configuration example of the charge / discharge device according to the second embodiment. 4 is a secondary-side converter that controls the secondary side of the step-up / step-down DC / DC converter 4 and the isolated DC / DC converter 3 by using the controller 10 of the charge / discharge device shown in FIG. The control part 12, the inverter control part 13 which controls the grid connection inverter 2, the primary side converter control part 14 which controls the primary side of the insulation type DC / DC converter 3, the inverter control part 13 and the primary side The converter control unit 14 and the secondary side converter control unit 12 are replaced with an insulation signal transmission unit 15 that insulates.

  In the present embodiment, the block constituted by the step-up / step-down DC / DC converter 4 and the secondary side converter (single-phase inverter 22) of the insulation type DC / DC converter 3 and the secondary side converter control unit 12 is insulated and secondary. A block constituted by the primary side converter (single-phase inverter 21) of the isolated DC / DC converter 3 and the primary side converter control unit 14 is referred to as an isolated primary converter 32. A block configured by the grid interconnection inverter 2, the inverter control unit 13, and the like is referred to as a grid interconnection inverter 33.

  Insulated secondary converter 31 of the present embodiment is a power conversion device that can be used alone as a power conditioner for photovoltaic power generation, and is used as a power conditioner for photovoltaic power generation or used as insulated secondary converter 31. This can be modified only by the software of the secondary side converter control unit 12.

  The isolated primary converter 32 and the interconnection inverter 33 have substantially the same configuration when compared only with the control circuit unit and the semiconductor circuit configuration.

  By separating in this way, the same circuit configuration form can be obtained, and diversion can be made only by standardization of the circuit or change of software. Therefore, the cost can be greatly reduced. In addition, circuit diversion can be realized with a power conditioner for photovoltaic power generation, and further cost reduction can be realized by increasing the quantity.

  The primary side converter control unit 14 may configure a circuit with a gate array or the like without using a CPU such as a microcomputer. By configuring with H / W without using a microcomputer or the like, it can be realized as a conversion device including the isolated DC / DC converter 3 by the isolated secondary converter 31 and the isolated primary converter 32, and in particular, the phase of the PWM signal Therefore, no control delay occurs when boost / buck or charge / discharge is controlled, and voltage controllability and current controllability are improved.

  In particular, since the primary side converter control unit 14 and the secondary side converter control unit 12 (secondary side converter control unit 12 in FIG. 4) only need to be a master, functional separation that is easy to configure with a gate array or the like. I can say that.

  Since the grid interconnection inverter 2 and the insulation type DC / DC converter 3 need to operate in conjunction with each other, it is also necessary to cooperate with each other's control unit. For this reason, the inverter control unit 13 is preferably configured by software.

  As described above, the charging / discharging device of the present embodiment uses a circuit that can be used as a power conditioner for photovoltaic power generation, and uses the secondary-side inverter (single-phase inverter 22) of the insulated DC / DC converter 3. Insulated secondary converter 31 including step-up / step-down DC / DC inverter 4 is configured. As a result, standardization of the circuit and diversion of the circuit are possible, and cost reduction due to the mass production effect can be realized.

  As described above, the present invention is suitable for a charge / discharge device that charges and discharges a battery mounted on an electric vehicle or the like.

  1 system power supply, 2 system interconnection inverter, 3 insulation type DC / DC converter, 4 buck-boost DC / DC converter, 5 storage battery, 6 insulation transformer, 7, 8 capacitor, 10 control unit, 11a, 11b, 11c, 11d, 11e, 11f Drive unit, 12 Secondary side converter control unit, 13 Inverter control unit, 14 Primary side converter control unit, 15 Insulation signal transmission unit, 21, 22 Single phase inverter, 21a, 22a Three phase inverter, 31 Insulation 2 Secondary converter, 32 Insulated primary converter, 33 Interconnected inverter.

Claims (6)

A charge / discharge device that performs bidirectional power conversion between a system power supply and a power storage device,
A first power conversion unit capable of performing an operation of converting AC power input from the system power source into DC power and an operation of converting DC power input from the power storage device side into AC power;
A second power conversion unit that includes an insulation transformer and converts the input voltage from the first power conversion unit or the input voltage from the power storage device side at a constant conversion ratio;
A third power converter for converting the conversion ratio based on the input voltage and the input voltage from the power storage device from the second power conversion unit to the voltage across said energy storage device,
A charge / discharge device comprising: The second power conversion unit converts the input voltage into a voltage insulated at a constant conversion ratio when the power storage device is charged and when the power storage device is discharged,
When the third power conversion unit charges the power storage device, the third power conversion unit steps down the input voltage at a conversion ratio based on the conversion ratio in the second power conversion unit and the voltage across the power storage device, and the power storage device When discharging, the input voltage is boosted at a conversion ratio based on the conversion ratio in the second power conversion unit and the voltage across the power storage device,
The charging / discharging device according to claim 1. Charge and discharge operations for multiple types of power storage devices with different voltage at both ends,
3. The charge / discharge device according to claim 1, wherein the third power conversion unit is configured to selectively connect one of the plurality of types of power storage devices.   4. The charge / discharge device according to claim 1, wherein a conversion ratio in the second power conversion unit is set to 1. 5. The second power conversion unit has a configuration in which two inverters are connected via the insulation transformer,
The third power conversion unit and the inverter arranged on the third power conversion unit side in the second power conversion unit are realized by a circuit common with a power conditioner for photovoltaic power generation. The charge / discharge device according to any one of claims 1 to 4. A charge / discharge device that performs bidirectional power conversion between a system power supply and a power storage device,
A first power conversion unit capable of performing an operation of converting AC power input from the system power supply side into DC power, and an operation of converting DC power input from the power storage device side into AC power;
A second power converter for converting the conversion ratio based on the input voltage from the input voltage and the power storage device from the first power conversion unit to the voltage across said energy storage device,
An insulating transformer provided between the system power supply and the first power converter;
A charge / discharge device comprising:

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