JP2016005388A - Electric vehicle charge/discharge device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an electric vehicle charge/discharge device capable of efficiently performing power conversion in each of charge operation and discharge operation.SOLUTION: An electric vehicle charge/discharge device comprises: a charge circuit 2a for converting AC power to DC power to charge a lithium battery 1a in an electric vehicle 1; and a discharge circuit 2b for converting DC power stored in the lithium battery 1a in the electric vehicle 1 to AC power to perform discharge. Output capacity of the charge circuit 2a is made to be larger than that of the discharge circuit 2b.

Description

  The present invention relates to a charge / discharge device for an electric vehicle.

  Conventionally, a technique including a bidirectional circuit having a mode for converting AC power into DC power and a mode for converting DC power into AC power is disclosed in Patent Document 1 below regarding a charging / discharging device for an electric vehicle.

  Since the charging / discharging device for an electric vehicle completes charging of the storage battery of the electric vehicle in as short a time as possible, a device with a large output is required. For example, when the capacity of an electric vehicle storage battery is 24 kWh, the charge output of the charge / discharge device for an electric vehicle takes 8 hours from empty to full charge when the charge output is 3 kW, but 4 hours when the charge output is 6 kW, and 12 kW when the charge output is 12 kW. Charging is completed in 2 hours.

  On the other hand, in the case of a discharge operation in which DC power stored in a storage battery of an electric vehicle is converted into AC power and used, even when an air conditioner, a television, lighting, a refrigerator, or the like is used, power of 3 kW or less is sufficient. Since the charging / discharging device for an electric vehicle combines charging and discharging with one circuit, for example, when the charging output is designed at 12 kW, the output capacity at the time of discharging automatically becomes 12 kW. In the discharging operation, the electric vehicle charging / discharging device operates with a reduced output according to the load in the house.

JP 2014-27826 A

  However, according to the conventional technique, the efficiency of the circuit is greatest at the maximum output, and the efficiency decreases when the output is reduced. This is a design that selects parts such as transformers, switching elements, relays, etc. that make up the circuit so that it is highly efficient in accordance with the maximum output. Although the loss due to the resistance is reduced, the proportion of loss that does not depend on current, such as driving power of the relay and iron loss of the transformer, increases. Therefore, there is a problem that the efficiency of power conversion is reduced in the discharging operation relative to the charging operation.

  The present invention has been made in view of the above, and an object thereof is to obtain a charging / discharging device for an electric vehicle capable of converting power with high efficiency in each operation of a charging operation and a discharging operation.

  In order to solve the above-described problems and achieve the object, the present invention includes a charging circuit that converts AC power into DC power and charges a storage battery of an electric vehicle, and the DC power stored in the storage battery is AC power. A discharge circuit that converts the discharge circuit to discharge, and makes the output capacity of the charging circuit larger than the output capacity of the discharge circuit.

  According to the present invention, there is an effect that power conversion can be performed with high efficiency in each operation of a charging operation and a discharging operation.

FIG. 1 is a diagram illustrating an efficiency curve of a general power converter. FIG. 2 is a diagram illustrating a configuration example of the electric vehicle charge / discharge device according to the first embodiment. FIG. 3 is a diagram illustrating a configuration example of the charging / discharging device for an electric vehicle according to the second embodiment.

  Embodiments of a charging / discharging device for an electric vehicle 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.
First, characteristics of a general power converter will be briefly described. FIG. 1 is a diagram illustrating an efficiency curve of a general power converter. The horizontal axis indicates the output [%] relative to the maximum output, and the vertical axis indicates the efficiency [%]. Efficiency is greatest at maximum output, and efficiency decreases when output is reduced. For example, when the maximum output is 12 kW, the output is 12 kW and the efficiency is 90% as compared with the output of 100%. Therefore, a loss of about 1.3 kW is generated from the calculation formula of 12 / 0.9-12. Here, when the output is reduced to 3 kW, which is 25% of the maximum output 12 kW, the efficiency is reduced to 70%. Therefore, the loss is about 1.3 kW from the calculation formula of 3 / 0.7-3. As described above, in the power converter, when the output is reduced, the ratio of loss to the output is increased, so that the efficiency is lowered. Therefore, it is desirable that the power converter operates in a state where the output is large.

  It continues and demonstrates the charging / discharging apparatus for electric vehicles of this Embodiment. FIG. 2 is a diagram illustrating a configuration example of the electric vehicle charging / discharging device 2 according to the present embodiment. The electric vehicle charging / discharging device 2 is connected to the electric vehicle 1 via a power line 4 for power transmission / reception and a signal line 5 for information transmission / reception. The electric vehicle charging / discharging device 2 is connected to the house 3. The electric vehicle charging / discharging device 2 can be supplied with AC power from the commercial power system 6 via the house 3.

  The electric vehicle 1 includes a lithium battery 1a that is a storage battery serving as a power source, and an information communication device 1b that communicates various types of information between the electric vehicle charging / discharging device 2 and the electric vehicle 1.

  The house 3 includes an operation panel 2d of the electric vehicle charging / discharging device 2, a relay 2e that disconnects the house 3 and the commercial power system 6, and various home appliances 3a to 3d in the house.

  The electric vehicle charging / discharging device 2 includes a charging circuit 2a, a discharging circuit 2b, a control circuit 2c, and a control power generation circuit 2f.

  The charging circuit 2 a converts the AC power of the commercial power system 6 into DC power and charges the lithium battery 1 a of the electric vehicle 1.

  The discharge circuit 2 b converts the DC power of the lithium battery 1 a of the electric vehicle 1 into AC power, and discharges the AC power by supplying the AC power to various home appliances 3 a to 3 d in the house 3.

  The control circuit 2 c controls the operation of the electric vehicle charging / discharging device 2. The control circuit 2c detects the voltage on the commercial power system 6 side of the relay 2e. When the detected voltage is within the range of normal AC voltage and frequency of the commercial power system 6, for example, AC voltage 200V ± 20V, frequency 50Hz ± 2.5Hz, the control circuit 2c turns on the relay 2e and turns on the house 3 and commercial power. The system 6 is connected, and various household electrical appliances 3 a to 3 d such as a refrigerator, an air conditioner, and a television in the house 3 are operated by the power of the commercial power system 6. The control circuit 2 c receives information on the remaining capacity of the lithium battery 1 a from the electric vehicle 1 via the signal line 5. When the lithium battery 1a is not fully charged, the control circuit 2c turns on the connection switching means, which is a relay in the charging circuit 2a, and operates the switching element of the charging circuit 2a composed of a switching element and a transformer. AC power from the power system 6 is converted to DC power, and the lithium battery 1a of the electric vehicle 1 is charged.

  The control power supply generation circuit 2 f generates a control power supply from the power of the commercial power system 6 or the lithium battery 1 a of the electric vehicle 1. The electric vehicle charging / discharging device 2 is operated by the electric power from the control power generation circuit 2f.

  When power supply from the commercial power system 6 is stopped due to a power failure, in the electric vehicle charging / discharging device 2, the control circuit 2c displays a power failure on the operation panel 2d. In addition, the control circuit 2c determines that the operation panel 2d is connected to the operation panel 2d when the electric vehicle 1 is connected from the information obtained through the signal line 5 and the lithium battery 1a has a remaining capacity sufficient to supply power to the house 3. The display prompting the user whether or not to supply power from the lithium battery 1a into the house 3 is displayed.

  When the user is at home at the time of a power failure and the user gives an instruction to supply power to the house 3 using the operation panel 2d, the control circuit 2c opens the relay 2e to remove the house 3 from the commercial power system 6. Separate. The control circuit 2c stops the charging circuit 2a and opens the connection switching means in the charging circuit 2a. The control circuit 2c turns on the connection switching means, which is a relay in the discharge circuit 2b, and operates the switching element of the discharge circuit 2b composed of a switching element and a transformer to store in the lithium battery 1a of the electric vehicle 1. The generated direct current power is converted into alternating current power, and various household electrical appliances 3a to 3d in the house are operated.

  Here, in this embodiment, in the charging / discharging device 2 for an electric vehicle, a connection switching means, a switching element, and a transformer are selected with a maximum output of 12 kW for the charging circuit 2a. On the other hand, for the discharge circuit 2b, a connection switching means, a switching element, and a transformer are selected with a maximum output of 3 kW. That is, in the electric vehicle charging / discharging device 2, the output capacity that is the maximum output of the charging circuit 2a is set larger than the output capacity that is the maximum output of the discharging circuit 2b.

  In the case of the power converter shown in FIG. 1, for example, since the efficiency is 90% at the maximum output of 12 kW, a loss of about 1.3 kW occurs. When the output is reduced to 3 kW, the efficiency decreases to 70%, so the loss is about 1.3 kW.

  In the present embodiment, for the discharge circuit 2b, connection switching means, switching elements, and transformer components that maximize efficiency at a maximum output of 3 kW are selected. Since the iron loss of the transformer increases in accordance with the size of the transformer, the transformer can be reduced in accordance with 3 kW, so that the iron loss can be reduced. In addition, the connection switching means is also compatible with 3 kW, so that it is possible to reduce the driving power for maintaining the ON state as compared with the 12 kW compatible large current. By selecting parts for the discharge circuit 2b at the time of 3kW output, the efficiency at the time of 3kW output can be 90%. Thereby, in the charging / discharging apparatus 2 for electric vehicles, since the loss of the discharge circuit 2b can be suppressed to about 0.3 kW from the calculation formula 3 / 0.9-3, the electric power of the lithium battery 1a of the electric vehicle 1 can be reduced. Can be efficiently supplied into the house 3.

  As described above, according to the present embodiment, in the charging / discharging device 2 for an electric vehicle, the charging circuit 2a for charging and the discharging are configured as a configuration for charging and discharging power to and from the lithium battery 1a of the electric vehicle 1. The discharge circuit 2b is provided separately, and the output capacity that is the maximum output of the charging circuit 2a is made larger than the output capacity that is the maximum output of the discharge circuit 2b. Thereby, in the charging / discharging apparatus 2 for electric vehicles, in charging operation and discharging operation, power conversion can be performed with high efficiency for each operation, and loss can be reduced and electric power can be effectively used.

  The maximum output of the charging circuit 2a is 12 kW and the maximum output of the discharging circuit 2b is 3 kW. However, this is an example, and the size of the maximum output is not limited to this. In the electric vehicle charging / discharging device 2, it is possible to appropriately set the maximum output of the charging circuit 2a and the maximum output of the discharging circuit 2b in accordance with the actual use situation.

Embodiment 2. FIG.
FIG. 3 is a diagram showing a configuration example of the electric vehicle charging / discharging device 2A of the present embodiment. The electric vehicle charging / discharging device 2A is a charging circuit having a maximum output of 12 kW, a plurality of small-capacity charging circuits having a capacity smaller than the maximum output of 12 kW, and charging circuits 2 a 1 to 2 a 4 divided into four for each maximum output of 3 kW. In addition, as a discharge circuit having a maximum output of 3 kW, a plurality of small-capacity discharge circuits having a capacity smaller than the maximum output of 3 kW are provided. The discharge circuits 2b1 and 2b2 are divided into two at a maximum output of 1.5 kW. Further, in the house 3, a solar cell 7 having a power generation amount of 8 kW is installed on the roof, and a power conditioner 8 that converts DC power from the solar cell 7 into AC power and supplies the AC into the house 3 is provided. Other configurations are the same as those of the first embodiment shown in FIG.

  When charging the lithium battery 1 a of the electric vehicle 1, the control circuit 2 c acquires the power generation information of the solar battery 7 from the power conditioner 8. When the weather is good and the amount of power generation is large, the control circuit 2c operates all the charging circuits 2a1 to 2a4, and combines the electric power of solar power generation by the solar battery 7 and the electric power of the commercial power system 6 at 12 kW. 1 is charged into the lithium battery 1a. When there is no power generation due to rain, night, etc., the control circuit 2c operates only the charging circuit 2a1 and charges the lithium battery 1a of the electric vehicle 1 at 3 kW so as not to exceed the contracted power with the power company. . The control circuit 2c performs charging by further operating the charging circuits 2a2 to 2a4 in accordance with the amount of photovoltaic power generated by the solar battery 7. The control circuit 2c determines the number of charging circuits to be operated based on the chargeable electric energy.

  On the other hand, when a discharge is performed using the power of the lithium battery 1a of the electric vehicle 1 at the time of a power failure, the control circuit 2c operates the discharge circuits 2b1 and 2b2 and starts the operation at the same time, thereby specifying the specified AC voltage. Is output. For example, when the output power of each of the discharge circuits 2b1 and 2b2 is 0.7 kW or less, the control circuit 2c stops the operation of the discharge circuit 2b2 and outputs 1.4 kW only by the discharge circuit 2b1. When the output power exceeds 1.4 kW, the control circuit 2c operates the discharge circuit 2b2 to drive the two discharge circuits. In this way, the control circuit 2c determines the number of discharge circuits to be operated according to the load power, that is, based on the amount of power used, and drives one or two discharge circuits.

  In the present embodiment, in the electric vehicle charging / discharging device 2A, the charging circuit is divided into small blocks, and connection switching means, switching elements, and transformers that maximize the efficiency at the time of maximum rating in each small block are selected. Similarly, in the electric vehicle charging / discharging device 2A, the discharge circuit is divided into small blocks, and connection switching means, switching elements, and transformers that maximize the efficiency at the maximum rating in each small block are selected.

  As described above, according to the present embodiment, the electric vehicle charging / discharging device 2A includes a plurality of charging circuits and a plurality of discharging circuits, and one unit is provided according to the output during charging and the output during discharging. Only one or a plurality of units are driven simultaneously. As a result, the power at the time of charging is obtained from the solar power generation and the commercial power system 6, and when the charging power changes greatly due to changes in the amount of solar radiation such as bad weather and low power from solar power generation, In the case where the discharge output changes due to the load fluctuation within 3, operation with less power loss is possible depending on the situation.

  In the present embodiment, the charging circuit and the discharging circuit are each divided into small blocks and provided with a plurality of units. However, the present invention is not limited to this. In the electric vehicle charging / discharging device, for example, the charging circuit 2a may be provided as a charging circuit, the discharging circuits 2b1 to 2b2 may be provided as discharging circuits, the charging circuits 2a1 to 2a4 may be provided as charging circuits, and the discharging circuit 2b may be provided as a discharging circuit. Alternatively, one circuit may be configured by one unit and the other circuit may be configured by a plurality of units.

  As described above, the charging / discharging device for an electric vehicle according to the present invention is useful for charging / discharging a storage battery of an electric vehicle, and is particularly suitable for effective use of electric power.

  DESCRIPTION OF SYMBOLS 1 Electric vehicle, 1a Lithium battery, 1b Information communication apparatus, 2,2A Electric vehicle charging / discharging device, 2a Charging circuit, 2b Discharging circuit, 2c Control circuit, 2d Operation panel, 2e Relay, 2f Control power generation circuit, 3 Housing 3a to 3d Household appliances in a house, 4 power lines, 5 signal lines, 6 commercial power systems, 7 solar cells, 8 power conditioners.

Claims (6)

A charging circuit that converts alternating current power into direct current power and charges a storage battery of an electric vehicle;
A discharge circuit that converts the DC power stored in the storage battery into AC power and discharges it;
With
Making the output capacity of the charging circuit larger than the output capacity of the discharging circuit;
Charge / discharge device for electric vehicles. The charging circuit and the discharging circuit include connection switching means for connecting to the storage battery,
The charging / discharging apparatus for electric vehicles of Claim 1. A control circuit for controlling the charging operation of the charging circuit,
When the charging circuit is composed of a plurality of small capacity charging circuits having a capacity smaller than the output capacity of the charging circuit,
The control circuit determines the number of the small-capacity charging circuits to be operated based on the chargeable electric energy.
The charging / discharging apparatus for electric vehicles of Claim 1. The small-capacity charging circuit includes connection switching means for connecting to the storage battery,
The charging / discharging apparatus for electric vehicles of Claim 3. A control circuit for controlling the discharge operation of the discharge circuit,
When the discharge circuit is constituted by a plurality of small-capacity discharge circuits having a capacity smaller than the output capacity of the discharge circuit,
The control circuit determines the number of small-capacity discharge circuits to be operated based on the amount of power used.
The charging / discharging apparatus for electric vehicles of Claim 1, 3 or 4. The small-capacity discharge circuit includes connection switching means for connecting to the storage battery,
The charging / discharging apparatus for electric vehicles of Claim 5.

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