Charging and discharging system

Abstract

To provide a charging / discharging system capable of reducing wiring loss.SOLUTION: Between a power conditioner 3 and a charging / discharging device 4, DC power having a higher voltage than AC power of a system power supply 1 is transmitted. Wiring loss is determined by a product of square of a current value and a resistance value (I2×R). Therefore, by increasing a voltage in wiring L1a between the power conditioner 3 and the charging / discharging device 4, it is possible to reduce wiring loss in that portion. Further, the power conditioner 3 is provided on a connection line L1 as a device separate from the charging / discharging device 4. Therefore, as compared with a configuration in which components of the power conditioner 3 are incorporated in the charging / discharging device 4 (see FIG. 2), a wiring length of the wiring L1a with less wiring loss can be increased. As described above, it is possible to reduce wiring loss of a charging / discharging system 100.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a charging and discharging system. [Background technology]

[0002] Conventionally, a charge / discharge system for charging and discharging objects is known, as described in Patent Document 1. This charge / discharge system has multiple charge / discharge devices, each of which is individually and directly connected to a distribution board. Each charge / discharge device includes an AC / DC converter and a DC / DC converter. The distribution board and the charge / discharge devices are connected to each other via connecting wires. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-202697 [Overview of the project] [Problems that the invention aims to solve]

[0004] However, the aforementioned charging and discharging system had a problem: large wiring losses between the distribution board and the charging and discharging device. Therefore, there was a need for a charging and discharging system that could reduce wiring losses.

[0005] The present invention aims to provide a charging and discharging system that can reduce wiring losses. [Means for solving the problem]

[0006] The charge / discharge system according to the present invention comprises a charge / discharge device having a DC / DC conversion unit that charges and discharges an object to be charged and discharged, a distribution board connected to a grid power supply, a power conditioner connected to the grid power supply and having an AC / DC conversion unit, and a connecting line connecting the charge / discharge device and the distribution board. DC power with a voltage higher than the AC power of the grid power supply is transmitted between the power conditioner and the charge / discharge device, and the power conditioner is provided on the connecting line as a separate device from the charge / discharge device.

[0007] In the charge / discharge system according to the present invention, during charging, the power conditioner converts AC power supplied from the grid power source via a distribution board into DC power and transmits it to the charge / discharge device. The charge / discharge device adjusts the voltage of the DC power to charge the object to be charged or discharged. During discharging, the charge / discharge device, having received discharge from the object to be charged or discharged, adjusts the voltage of the DC power and transmits it to the power conditioner. Here, DC power with a higher voltage than the AC power from the grid power source is transmitted between the power conditioner and the charge / discharge device. Wiring loss is determined by the product of the square of the current value and the resistance value. Therefore, by increasing the voltage in the connection line between the power conditioner and the charge / discharge device, wiring loss at that point can be reduced. Furthermore, the power conditioner is provided as a separate device from the charge / discharge device in the connection line. Therefore, compared to a configuration in which the components of the power conditioner are incorporated inside the charge / discharge device, the wiring length in areas with less wiring loss can be increased. As a result, wiring loss in the charge / discharge system can be reduced.

[0008] The power conditioner may be installed on the distribution board side of the connection line. In this case, the length of the wiring can be increased in areas where wiring loss is minimal.

[0009] The charging and discharging system comprises two or more charging and discharging devices, which are connected in parallel to the power conditioner via branching connection lines. In this case, when increasing the number of charging and discharging devices, only the charging and discharging devices need to be added, eliminating the need to add power conditioners. Therefore, the number of charging and discharging devices can be increased in a space-saving and low-cost manner. [Effects of the Invention]

[0010] According to the present invention, a charging and discharging system that can reduce wiring losses can be provided. [Brief explanation of the drawing]

[0011] [Figure 1] This is a block diagram showing a charge / discharge system according to an embodiment of the present invention. [Figure 2] This is a block diagram showing a charge / discharge system related to a comparative example. [Figure 3] This is a block diagram showing a modified charging and discharging system. [Figure 4] This is a block diagram showing a charge / discharge system related to a comparative example. [Modes for carrying out the invention]

[0012] Embodiments of the present invention will be described in detail below with reference to the attached drawings. In the description of the drawings, the same or equivalent elements will be denoted by the same reference numerals, and redundant descriptions will be omitted.

[0013] Figure 1 is a block diagram showing a charge / discharge system 100 according to an embodiment of the present invention. The charge / discharge system 100 charges and discharges an automobile V. In this embodiment, an electric vehicle (EV) having a battery is used as the object to be charged and discharged. The charge / discharge system 100 comprises a grid power supply 1, a distribution board 2, a power conditioner 3, a charge / discharge device 4, and connecting lines L1 and L2.

[0014] The connection lines L1 and L2 are wiring for connecting devices to each other and transmitting power. The utility power supply 1 and the distribution board 2 are connected by the connection line L2. The distribution board 2 and the charge / discharge device 4 are connected by the connection line L1. The power conditioner 3 is provided at an arbitrary position on the connection line L1. The connection line L1 has a wiring L1b connecting the distribution board 2 and the power conditioner 3, and a wiring L1a connecting the power conditioner 3 and the charge / discharge device 4.

[0015] The utility power supply 1 is a power supply provided by an electric power company. The distribution board 2 is a part electrically connected to the utility power supply 1. The distribution board 2 is a device for distributing the power from the utility power supply 1. The distribution board 2 transmits and receives power to and from the utility power supply 1 via the connection line L2.

[0016] The power conditioner 3 is a device that is grid-connected to the utility power supply 1 and performs power conversion between the utility power supply 1 and the charge / discharge device 4. A bidirectional PCS (Power Conditioning System) is used as the power conditioner 3. The power conditioner 3 includes a grid connection unit 11 and an AC / DC conversion unit 12. The grid connection unit 11 has a function of being grid-connected to the utility power supply 1. The AC / DC conversion unit 12 has a function of converting AC power into DC power and converting DC power into AC power.

[0017] The charge / discharge device 4 is a device that charges and discharges the automobile V. The charge / discharge device 4 includes a DC / DC conversion unit 13 and a communication unit 14. The DC / DC conversion unit 13 has a function of converting a predetermined DC power into DC power of another voltage. The communication unit 14 communicates with the automobile V and controls the DC / DC conversion unit 13 based on an instruction from the automobile V.

[0018] For example, the system power supply 1 supplies 200V AC power via the distribution board 2. The AC / DC conversion unit 12 of the power conditioner 3 converts the AC power of the system power supply 1 into DC power at a voltage higher than the AC power (for example, 300V to 400V). Therefore, the power conditioner 3 is connected to the charge / discharge device 4 at a voltage higher than the AC power of the system power supply 1. Thus, a DC current of 300V to 400V flows through the wiring L1a. The DC / DC conversion unit 13 of the charge / discharge device 4 adjusts the voltage based on the charge current indication value from the vehicle V so that it falls within a determined voltage range. As a result, DC power at a voltage higher than the AC power of the system power supply 1 is transmitted between the power conditioner 3 and the charge / discharge device 4.

[0019] The power conditioner 3 is provided on the connection line L1 as a separate device from the charge / discharge device 4. Here, a separate device is a device that can operate independently of the charge / discharge device 4. The components of the power conditioner 3 are arranged outside the housing of the charge / discharge device 4. Therefore, as shown in FIG. 2, the state where the components of the power conditioner 3 are arranged inside the housing of the charge / discharge device 4 and operated by the control system of the charge / discharge device 4 does not correspond to the state where the power conditioner exists as a separate device from the charge / discharge device.

[0020] In the comparative example shown in FIG. 2, each component is wired inside the charge / discharge device 204, but in the charge / discharge system 100 according to the present embodiment, the power conditioner 3 is a separate device from the charge / discharge device 4 and is arranged outside the charge / discharge device 4. Therefore, in the comparative example, the AC / DC conversion unit 12 and the DC / DC conversion unit 13 were connected inside the device with a connector or the like, but in the present embodiment, a terminal block is required at any location between the AC / DC conversion unit 12 and the DC / DC conversion unit 13. Also, in the present embodiment, since the wiring length between the AC / DC conversion unit 12 and the DC / DC conversion unit 13 becomes long, a wiring protection member such as a wiring circuit breaker is provided at the output of the power conditioner 3 to prevent a short circuit or the like. Further, since the wiring length between the AC / DC conversion unit 12 and the DC / DC conversion unit 13 becomes long, lightning surge countermeasure components such as a surge absorber are incorporated in the input section of the DC / DC conversion unit 13.

[0021] Furthermore, the power conditioner 3 is installed on the distribution board 2 side of the connection line L1. The power conditioner 3 is installed closer to the distribution board 2 than the charge / discharge device 4. The length of the wiring L1b between the distribution board 2 and the power conditioner 3 is shorter than the length of the wiring L1a between the power conditioner 3 and the charge / discharge device 4. Although not particularly limited, when the total length of the connection line L1 is taken as 100%, the length of the wiring L1b may be in the range of 1% or more and less than 100%, and more preferably less than 50%. The length of the wiring L1a may be in the range of 1% or more and less than 100%, and more preferably 50% or more. However, the power conditioner 3 only needs to be located at any position on the connection line L1, and may also be located on the charge / discharge device 4 side.

[0022] Next, the operation of the charge / discharge system 100 during charging and discharging will be described. First, the charging of the automobile V will be described. First, the communication unit 14 of the charge / discharge device 4 communicates with the automobile V. The communication unit 14 obtains a charging current instruction value from the automobile V via communication. The communication unit 14 transmits the obtained charging current instruction value to the DC / DC conversion unit 13. The DC / DC conversion unit 13 increases (or decreases) the voltage of the input power to the DC / DC conversion unit 13 to match the charging current instruction value and to be within a predetermined voltage range. The charge / discharge device 4 outputs the adjusted DC power to charge the automobile V. Also, during charging, the AC / DC conversion unit 12 of the power conditioner 3 converts the 200V AC power from the grid power supply 1 into DC power of a preset voltage (for example, 300V) and supplies it to the charge / discharge device 4. Note that since the automobile V and the grid need to be isolated, the DC / DC conversion unit 13 may be used for isolation.

[0023] Next, we will explain the discharge process from the vehicle V. The communication unit 14 of the charge / discharge device 4 communicates with the vehicle V regarding the discharge. The vehicle V then discharges to the charge / discharge device 4. The DC / DC conversion unit 13 boosts (or lowers) the voltage to the power conditioner 3 so that the output voltage to the power conditioner 3 becomes a preset voltage (for example, 300V), and then supplies it to the power conditioner 3. Note that the power supply from the charge / discharge device 4 to the power conditioner may be controlled by either CC control or CV control.

[0024] Next, the operation and effects of the charge / discharge system 100 of this embodiment will be described.

[0025] In the charge / discharge system 100 according to this embodiment, during charging, the power conditioner 3 converts the AC power supplied from the grid power 1 via the distribution board 2 into DC power and transmits it to the charge / discharge device 4. The charge / discharge device 4 can charge the automobile V by adjusting the voltage of the DC power. During discharging, the charge / discharge device 4, which has been discharged from the automobile V, adjusts the voltage of the DC power and transmits it to the power conditioner 3. Here, DC power with a higher voltage than the AC power of the grid power 1 is transmitted between the power conditioner 3 and the charge / discharge device 4. Wiring loss is determined by the product of the square of the current value and the resistance value (I 2 ×R). Therefore, by increasing the voltage in the wiring L1a between the power conditioner 3 and the charge / discharge device 4, wiring loss at that point can be reduced. Furthermore, the power conditioner 3 is provided on the connecting line L1 as a separate device from the charge / discharge device 4. Therefore, compared to a configuration in which the components of the power conditioner 3 are incorporated inside the charge / discharge device 4 (see Figure 2), the wiring length of the wiring L1a, which has less wiring loss, can be increased. As a result, wiring loss in the charge / discharge system 100 can be reduced.

[0026] The power conditioner 3 may be installed on the distribution board 2 side of the connection line L1. In this case, the length of the wiring L1a, which has less wiring loss, can be increased.

[0027] Referring to Figure 2, the comparative example charge / discharge system 200 will be described. The comparative example charge / discharge system 200 has a charge / discharge device 204 that incorporates an AC / DC conversion unit 12, a grid connection unit 11, a DC / DC conversion unit 13, and a communication unit 14 as a single device. AC power of 200V, which is the voltage of the grid power supply 1, is transmitted through the connection line L1 between the distribution board 2 and the charge / discharge device 204. Thus, the connection line L1 does not have a section with low wiring loss, as shown in the wiring L1a in Figure 1.

[0028] The losses of the charge / discharge system 100 according to the embodiment and the charge / discharge system 200 according to the comparative example will be explained with specific examples. First, the total wiring length of the connecting wire L1 is set to 10m (20m round trip). The resistance value of the copper wire of the connecting wire L1 is 0.0172Ωmm 2 Let / m be the diameter, and the thickness be 8sq(mm 2 ) The power is set to 10kW. The AC is single-phase two-wire, and its power factor is 1. In the charge / discharge system 100 according to the embodiment, the wiring length of wiring L1b is 1m and the voltage is 200V, and the wiring length of wiring L1a is 9m and the voltage is 300V. In the charge / discharge system 200 according to the comparative example, the wiring length of connecting wire L1 is 10m and the voltage is 200V.

[0029] The wiring loss of the comparative example charge / discharge system 200 is calculated to be 107.5W using the following equations (1) to (3). ρ×(L / S)=0.0172×(10 / 8)=0.0215Ω…(1) P = VIcosθ, power factor cosθ = 1. 10000W ÷ 200V = 50A …(2) 2 × I 2 ×R=2×50 2 ×0.0215 ≈ 107.5W …(3)

[0030] The wiring loss of the charge-discharge system 100 according to the embodiment is calculated as 53.75 W by the following formulas (4) to (10). Thus, the charge-discharge system 100 according to the embodiment has 53.75 W less loss than the charge-discharge system 100 according to the comparative example. ρ×(L / S)=0.0172×(9 / 8)=0.01935Ω …(4) 10000W÷300V = 33.3A …(5) I 2 ×R=33.3 2 ×0.01935 ≒ 21.5W …(6) 21.5×2=43W (round trip) …(7) ρ×(L / S)=0.0172×(1 / 8)=0.00215Ω …(8) P=VIcosθ From power factor cosθ = 1 10000W÷200V = 50A …(9) 2×I 2 ×R=2×50 2 ×0.00215 ≒ 10.75W …(10) 43+10.75 ≒ 53.75W …(11)

[0031] The present invention is not limited to the above-described embodiments.

[0032] For example, a charge / discharge system 300 as shown in Figure 3 may be adopted. The charge / discharge system 300 is equipped with two or more (in this case, two) charge / discharge devices 4, and the two or more charge / discharge devices 4 are connected in parallel to the power conditioner 3 by branching connection lines L1. The wiring L1a connected to the power conditioner 3 is branched to wiring L1c at an intermediate point, and the second charge / discharge device 4 is connected to this wiring L1c. In this case, when increasing the number of charge / discharge devices 4, only the charge / discharge devices 4 need to be increased, and it is not necessary to increase the number of power conditioners 3. Therefore, the number of charge / discharge devices 4 can be increased in a space-saving and low-cost manner. In addition, if a charge / discharge device 4 does not have an AC / DC conversion unit 12, the number of items to be inspected and investigated is reduced, making it easier to identify the fault location and improving maintainability.

[0033] For example, if there are multiple vehicles V, there may be situations where it is necessary to transfer the charge from one vehicle V to another to avoid using grid power, depending on the planned use and charge status of each vehicle. In this case, in the charge / discharge system 400 related to the comparative example shown in Figure 4, power is transferred as follows: "Vehicle V1 (discharging vehicle) → DC / DC converter 13 → DC / AC converter 12 → grid → AC / DC converter 12 → DC / DC converter 13 → Vehicle V2 (charging vehicle)". In contrast, in the charge / discharge system 300 in Figure 3, power is transferred as follows: "Vehicle V1 (discharging vehicle) → DC / DC converter 13 → DC / DC converter 13 → Vehicle V2 (charging vehicle)". Since power is transferred without passing through the DC / AC converter or AC / DC converter, power conversion losses in the omitted parts are eliminated.

[0034] [Form 1] A charge / discharge device having a DC / DC converter that performs charging and discharging on an object to be charged and discharged, A distribution board connected to the grid power supply, A power conditioner having an AC / DC converter is connected to the aforementioned grid power supply, The charging / discharging device and the distribution board are connected by connecting wires, Between the power conditioner and the charging / discharging device, DC power with a voltage higher than the AC power of the grid power supply is transmitted. The power conditioner is a separate device from the charge / discharge device and is provided on the connecting line as part of the charge / discharge system. [Form 2] The power conditioner is provided on the distribution board side in the connection line, in the charge / discharge system according to Embodiment 1. [Form 3] Equipped with two or more of the aforementioned charging and discharging devices, A charge-discharge system according to Embodiment 1 or 2, wherein two or more charge-discharge devices are connected in parallel to the power conditioner by branched connection lines. [Explanation of Symbols]

[0035] 1...System power supply, 2...Distribution board, 3...Power conditioner, 4...Charging / discharging device, 100, 300...Charging / discharging system, L1...Connecting wire.

Claims

1. A charge / discharge device having a DC / DC conversion unit that performs charging and discharging on an object to be charged and discharged, A distribution board connected to the grid power supply, A power conditioner that is connected to the grid power supply and has an AC / DC conversion unit, The charging / discharging device and the distribution board are connected by connecting wires, Between the power conditioner and the charging / discharging device, DC power with a voltage higher than the AC power of the grid power supply is transmitted. The power conditioner is provided on the connecting line as a separate device from the charging and discharging device. The power conditioner is provided on the distribution board side in the connection line, The length of the wiring between the distribution board and the power conditioner is shorter than the length of the wiring between the power conditioner and the charge / discharge device. A wiring protection member is provided at the output of the power conditioner, and a lightning surge protection component is incorporated at the input of the charge / discharge device. A terminal block is provided at one of the locations between the AC / DC conversion unit and the DC / DC conversion unit. Charging and discharging system.

2. Equipped with two or more of the aforementioned charging and discharging devices, The charge-discharge system according to claim 1, wherein two or more of the charge-discharge devices are connected in parallel to the power conditioner by branched connection lines.

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