Method for controlling charging device, and charging device

Abstract

Provided is a method for controlling a charging device (40) provided with: an AC / DC converter (50) in which an AC power supply or AC load is connected to an AC-side terminal (51) and in which a first battery (20) is connected to a DC-side terminal (52), the AC / DC converter (50) charging or discharging the first battery (20); and a DC / DC converter (60) in which one terminal (66) is connected to a connection line (53) for connecting the AC / DC converter (50) and the first battery (20) and in which the other terminal (67) is connected to a second battery (30) or a DC machine, the method comprising transmitting, to a conversion control unit (65) of the DC / DC converter (60) on the basis of current in the DC-side terminal (52) of the AC / DC converter (50), a signal for absorbing ripple current in the connection line (53), and causing the conversion control unit (65) to implement control for absorbing the ripple current in the DC / DC converter (60).

Description

CHARGER CONTROL METHOD AND CHARGER

[0001] The present invention relates to a control method for a charging device and a charging device.

[0002] Charging devices that convert AC supplied from an AC power source into DC and charge a battery are known (see, for example, Patent Document 1). The charging device described in Patent Document 1 has a circuit configuration based on a two-stage charging circuit that performs power factor correction and power adjustment involving conversion to high-frequency AC in two stages to suppress current ripple, which is a fluctuation in the output current to the battery. When charging multiple batteries with different voltages using a charging device such as that described in Patent Document 1, a DC / DC converter is used in combination with the charging device.

[0003] International Publication No. 2012 / 029101

[0004] The charging device described in Patent Document 1 has a circuit configuration based on a two-stage charging circuit, which has more components than a one-stage charging circuit, and requires additional components such as switches and relays to switch the circuit from a one-stage charging circuit to a two-stage charging circuit, which leads to increased costs.

[0005] An object of the present invention is to provide a control method for a charging device and a charging device that can suppress current ripple while suppressing an increase in cost.

[0006] One aspect of the present invention is to send a signal to a conversion control unit of a DC / DC converter based on the current at the DC side terminal of the AC / DC converter to absorb ripple current in a connection line connecting the AC / DC converter and a first battery, and to cause the conversion control unit to perform control to absorb the ripple current in the DC / DC converter.

[0007] FIG. 1 is a schematic diagram showing the general configuration of a charging system including a charging device according to a first embodiment. FIG. 2 is a control block diagram of a controller. FIG. 3 is a diagram showing waveforms of an AC power supply, a first battery, a ripple current absorption signal, and a DC / DC converter. FIG. 4 is a diagram showing switching waveforms of the DC / DC converter. FIG. 5 is a diagram showing the relationship between the amount of ripple current absorbed by the DC / DC converter and loss due to ripple current. FIG. 6 is a diagram showing waveforms of an AC power supply, a first battery, a ripple current absorption signal, and a DC / DC converter. FIG. 7 is a diagram showing switching waveforms of the DC / DC converter. FIG. 8 is a flowchart of a control method executed by a controller. FIG. 9 is a schematic diagram showing the general configuration of a charging system including a charging device according to a second embodiment.

[0008] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the second and subsequent embodiments, components that are the same as those in the previously described embodiments will be assigned the same numbers as those components or will not be shown in the drawings, and their description will be simplified or omitted.

[0009] 1 is a schematic diagram showing a general configuration of a charging system 10 according to a first embodiment. The charging system 10 is mounted on a vehicle such as an electric vehicle or a hybrid vehicle, and charges the vehicle with power supplied from an external AC power source and supplies the charged power to an external AC load.

[0010] The charging system 10 includes a first battery 20, a second battery 30, and a charging device 40.

[0011] The first battery 20 is a so-called high-power battery, and is made of nickel-metal hydride, lithium ion, etc. The voltage of the first battery 20 is, for example, 200 V.

[0012] The second battery 30 is a battery having a lower voltage than the first battery 20, and is configured as a lead battery or the like. The voltage of the second battery 30 is, for example, 12 [V] or 24 [V].

[0013] The charging device 40 includes an AC / DC converter 50 , a DC / DC converter 60 , sensors 70 A, 70 B, and 70 C, and a controller 80 .

[0014] An external AC power supply or an AC load is detachably connected to an AC side terminal 51 of the AC / DC converter 50 via a charging port (not shown), and the first battery 20 is connected to a DC side terminal 52. The AC / DC converter 50 converts one of AC and DC into the other, and charges or discharges the first battery 20. In this embodiment, the AC / DC converter 50 includes a single-stage charging circuit that performs, in a single stage, power factor correction involving switching operation and power adjustment involving conversion to high-frequency AC.

[0015] DC / DC converter 60 has one terminal 66 connected to connection line 53 that connects DC side terminal 52 of AC / DC converter 50 and first battery 20, and the other terminal 67 connected to second battery 30 or a DC device, to convert DC voltage. In this embodiment, DC / DC converter 60 is a bidirectional type that, when absorbing ripple current, which is a fluctuating current output from AC / DC converter 50, can allow current to flow in DC / DC converter 60 in a direction from first battery 20 to second battery 30 and a direction from second battery 30 to first battery 20.

[0016] The DC / DC converter 60 includes a first switching circuit 61 , a first smoothing capacitor 62 , a second switching circuit 63 , a second smoothing capacitor 64 , and an isolation transformer 65 .

[0017] The first switching circuit 61 is connected to the DC side terminal 52 of the AC / DC converter 50 and the first battery 20 via a connection line 53, and performs DC / AC conversion. The first switching circuit 61 includes switching elements Q1, Q2, Q3, and Q4, and diodes D1, D2, D3, and D4.

[0018] The switching elements Q1, Q2, Q3, and Q4 are connected in a full bridge configuration to form a so-called full bridge circuit. The switching elements Q1, Q2, Q3, and Q4 function as switches in response to control signals input from the controller 80. Examples of the switching elements Q1, Q2, Q3, and Q4 include an insulated gate bipolar transistor (IGBT), a metal-oxide-semiconductor field effect transistor (MOSFET), and a bipolar transistor.

[0019] The diodes D1, D2, D3, and D4 are provided corresponding to the switching elements Q1, Q2, Q3, and Q4, and are connected in parallel to the switching elements Q1, Q2, Q3, and Q4 so as to pass a current in a direction opposite to the direction of the current flowing through the corresponding switching elements Q1, Q2, Q3, and Q4.

[0020] The first smoothing capacitor 62 smoothes the voltage input from the DC side terminal 52 of the AC / DC converter 50. The first smoothing capacitor 62 is connected in parallel with the first switching circuit 61 to the connection line 53 between the AC / DC converter 50 and the first battery 20.

[0021] The second switching circuit 63 is connected to the second battery 30 and performs AC / DC conversion. The second switching circuit 63 includes switching elements Q5, Q6, Q7, and Q8 and diodes D5, D6, D7, and D8. The switching elements Q5, Q6, Q7, and Q8 and diodes D5, D6, D7, and D8 are configured similarly to the switching elements Q1, Q2, Q3, and Q4 and diodes D1, D2, D3, and D4 of the first switching circuit 61, and the description of the first switching circuit 61 is applicable, so a description thereof will be omitted.

[0022] The second smoothing capacitor 64 smoothes the voltage input from the second battery 30. The second smoothing capacitor 64 is connected in parallel with the second switching circuit 63 to the second battery 30 and the DC device.

[0023] The current sensor 70A detects the current flowing through the DC side terminal 52 of the AC / DC converter 50. Since the current flowing through the DC side terminal 52 includes a ripple current output from the AC / DC converter 50, the current sensor 70A also detects the ripple current.

[0024] The voltage sensor 70B detects the voltage across the first battery 20 .

[0025] The temperature sensor 70C detects the internal temperature of the first battery 20.

[0026] 2 is a control block diagram of the controller 80. The controller 80 controls the DC / DC converter 60. The controller 80 is realized by, for example, a microcomputer including a processor such as a central processing unit (CPU) or a central graphics processing unit (GPU), a storage unit 81 such as a read-only memory (ROM) or a random access memory (RAM), and an input / output unit such as an input / output interface. The controller 80 is electrically connected to a current sensor 70A, a voltage sensor 70B, a temperature sensor 70C, a first switching circuit 61, and a second switching circuit 63.

[0027] The controller 80 includes a storage unit 81 , an SOC calculation unit 82 , a ripple absorption necessity determination unit 83 , a ripple current absorption signal generation unit 84 , and a conversion control unit 85 .

[0028] The storage unit 81 stores a computer program for causing the controller 80 to function, various maps used for control, various parameter values, etc. The map stored in the storage unit 81 includes, for example, a map showing the relationship between the amount of ripple current absorbed by the DC / DC converter 60 and the loss due to the ripple current. The parameter values ​​stored in the storage unit 81 include, for example, various threshold values ​​such as a threshold value for the State of Charge (SOC), which is the charging rate of the first battery 20, and a threshold value for the internal temperature of the first battery 20.

[0029] The SOC calculation unit 82 calculates the SOC of the first battery 20. In the present embodiment, the SOC calculation unit 82 calculates the SOC of the first battery 20 based on the voltage across the first battery 20 and the internal temperature of the first battery 20.

[0030] The ripple absorption necessity determination unit 83 determines whether or not it is necessary to absorb the ripple current in the DC / DC converter 60. In the present embodiment, the ripple absorption necessity determination unit 83 determines whether or not it is necessary to absorb the ripple current based on the SOC of the first battery 20 and the internal temperature of the first battery 20.

[0031] The ripple current absorption signal generation unit 84 generates a signal (hereinafter referred to as a ripple current absorption signal) for absorbing the ripple current in the connection line 53 based on the current at the DC side terminal 52 of the AC / DC converter 50 and the target temperature of the first battery 20, and transmits the signal to the conversion control unit 85. The target temperature of the first battery 20 is received from a battery controller (not shown) of the first battery 20. In this embodiment, the ripple current absorption signal generation unit 84 generates the ripple current absorption signal based on the difference between the ripple current and the target temperature of the first battery 20. Furthermore, the ripple current absorption signal generation unit 84 of this embodiment switches between transmitting and not transmitting the ripple current absorption signal based on the SOC and internal temperature of the first battery 20.

[0032] The conversion control unit 85 controls the switching elements Q1 to Q8 based on the determination result of the ripple absorption necessity determination unit 83 and the ripple current absorption signal, and absorbs the ripple current in the DC / DC converter 60. The conversion control unit 85 also performs conversion control to perform voltage conversion based on the reference voltage of the DC / DC converter 60 and the output voltage of the DC / DC converter 60.

[0033] 3 is a diagram showing waveforms of the AC power supply, the first battery 20, the ripple current absorption signal, and the DC / DC converter 60. Note that V of the AC power supply waveform in FIG. 3 is the voltage of the AC power supply, and I of the AC power supply waveform is the current of the AC power supply.

[0034] When the AC / DC converter 50 is configured as a single-stage charging circuit, unlike a two-stage charging circuit, there is no large-capacity decoupling capacitor in the circuit to absorb ripples. Therefore, if the ripple current absorption signal is not transmitted, the current at the DC side terminal 52 will have an AC waveform as shown in Figure 3, causing ripples. In this case, the AC current generated by the AC / DC converter 50 flows to the first battery 20.

[0035] Ideally, the load current to first battery 20 is direct current. Since the load current is the sum of the alternating current generated by AC / DC converter 50 and the current absorbed by DC / DC converter 60, the alternating current can be made closer to direct current by having DC / DC converter 60 absorb current at the peaks of the ripple current and discharge current at the valleys of the ripple current.

[0036] 3 , the ripple current absorption signal generation unit 84 generates a ripple current absorption signal based on the difference between the current of the first battery 20 and the target current, and transmits the signal to the conversion control unit 85. The conversion control unit 85 controls the first switching circuit 61 and the second switching circuit 63 based on the ripple current absorption signal, thereby absorbing the ripple current generated at the DC side terminal 52 of the AC / DC converter 50 and preventing the ripple current from being sent to the first battery 20.

[0037] 4 is a diagram showing switching waveforms of the DC / DC converter 60. The conversion control unit 85 of the controller 80 alternately turns on and off two diagonally arranged switching elements Q1 and Q4 and the other two diagonally arranged switching elements Q2 and Q3 in the first switching circuit 61 with a duty of 50%, as shown in FIG. 4 . The conversion control unit 85 also alternately turns on and off two diagonally arranged switching elements Q5 and Q8 and the other two diagonally arranged switching elements Q6 and Q7 in the second switching circuit 63 with a duty of 50%. The conversion control unit 85 controls the phase difference θ1-2 between the switching elements Q1 and Q4 and the switching elements Q5 and Q8, and the phase difference θ1-2 between the switching elements Q2 and Q3 and the switching elements Q6 and Q7, thereby controlling the direction and magnitude of the current flowing through the DC / DC converter 60 to absorb ripple current. When the phase difference θ1-2 is greater than 0, a current flows from the first battery 20 to the second battery 30, and the larger the value of the phase difference θ1-2, the larger the current flows into the DC / DC converter 60. When the phase difference θ1-2 is less than 0, a current flows from the second battery 30 to the first battery 20, and the larger the value of the phase difference θ1-2, the larger the current flows out of the DC / DC converter 60. Therefore, the DC / DC converter 60 generates an AC current that absorbs the ripple current, and can therefore absorb the ripple current that would otherwise flow into the first battery 20.

[0038] 5 is a diagram showing the relationship between the amount of ripple current absorbed by the DC / DC converter 60 and the loss due to the ripple current. When the AC / DC converter 50 generates a ripple current and the DC / DC converter 60 absorbs the ripple current, increasing the amount of ripple current absorbed by the DC / DC converter 60 increases its own loss, and decreasing the amount of ripple current absorbed decreases its own loss. On the other hand, when the DC / DC converter 60 increases the amount of ripple current absorbed, the ripple current flowing into the first battery 20 decreases, so the loss in the first battery 20 decreases. On the other hand, when the DC / DC converter 60 decreases the amount of ripple current absorbed, the ripple current flowing into the first battery 20 increases, so the loss in the first battery 20 increases.

[0039] As shown in Figure 5, with the vertical axis representing loss due to ripple current and the horizontal axis representing the amount of ripple current absorption, the loss in the first battery 20 and the loss in the DC / DC converter 60 have the characteristics shown in the figure, and the sum of the two, i.e., the total loss, reaches a minimum at a certain absorption amount. In Figure 5, the minimum loss point occurs when the loss in the first battery 20 is equal to the loss in the DC / DC converter 60. By setting this point as the operating point, the ripple current absorption signal generator 84 can cause the conversion control unit 85 to absorb the ripple current at the maximum efficiency point where loss is minimized. Therefore, the ripple current absorption signal generator 84 of the controller 80 changes the ripple current absorption signal based on the comparison result between the loss due to the ripple current flowing through the first battery 20 and the loss due to ripple current absorption in the DC / DC converter 60, causing the conversion control unit 85 to control the amount of ripple current absorption in the DC / DC converter 60.

[0040] For example, if the loss in first battery 20 is smaller than the loss in DC / DC converter 60, ripple current absorption signal generator 84 reduces the amplitude of the ripple current absorption signal, as shown in Fig. 6. This causes conversion control unit 85 to reduce phase difference θ1-2, as shown in Figs. 6 and 7, and reduce the magnitude of the current flowing through DC / DC converter 60, i.e., the amount of ripple current absorbed by DC / DC converter 60.

[0041] On the other hand, if the loss in first battery 20 is greater than the loss in DC / DC converter 60, ripple current absorption signal generator 84 increases the amplitude of the ripple current absorption signal, as shown in Fig. 3. This causes conversion control unit 85 to increase phase difference θ1-2, as shown in Figs. 3 and 4, and increase the magnitude of the current flowing through DC / DC converter 60, i.e., the amount of ripple current absorbed by DC / DC converter 60.

[0042] The loss in the first battery 20 is calculated based on the internal resistance of the first battery 20 and the ripple current flowing to the first battery 20. The internal resistance of the first battery 20 is estimated from the internal temperature of the first battery 20. The ripple current flowing to the first battery 20 is detected by a current sensor 70A. The loss in the DC / DC converter 60 is calculated from the difference between the input power and the output power of the DC / DC converter 60. The input power and the output power of the DC / DC converter 60 are calculated based on the detected values ​​of a voltage sensor and a current sensor provided at the input / output terminals of the DC / DC converter 60, for example.

[0043] 8 is a flowchart of a control method executed by the controller 80. The control routine shown in the flowchart is pre-programmed, and this program is installed or controlled in the controller 80. The controller 80 repeatedly executes the following control routine in a cycle of, for example, several milliseconds to 10 milliseconds in accordance with the program or control circuit.

[0044] In step S1 of FIG. 6, the controller 80 acquires the outputs of the sensors 70A, 70B, and 70C, i.e., the current at the DC side terminal 52 of the AC / DC converter 50, the voltage across the first battery 20, and the internal temperature of the first battery 20.

[0045] In step S2, the ripple absorption necessity determination unit 83 determines whether the first battery 20 is being charged. If it is determined in step S2 that the first battery 20 is being charged, the ripple absorption necessity determination unit 83 determines in step S3 whether the SOC of the first battery 20 exceeds a first threshold. The first threshold is set to, for example, a value slightly (for example, about several percent) lower than the SOC target value at the time of completion of charging of the first battery 20. If it is determined in step S3 that the SOC of the first battery 20 exceeds the first threshold, the process proceeds to step S6.

[0046] On the other hand, if it is determined in step S2 that the first battery 20 is being charged, the ripple absorption necessity determination unit 83 determines in step S4 whether the first battery 20 is being discharged. If it is determined in step S4 that the first battery 20 is being discharged, the ripple absorption necessity determination unit 83 determines in step S5 whether the SOC of the first battery 20 is less than a second threshold. The second threshold is set to, for example, a value slightly (for example, about several percent) higher than the SOC target value at the completion of discharging of the first battery 20. If it is determined in step S5 that the SOC of the first battery 20 is less than the second threshold, the process proceeds to step S6.

[0047] In step S6, the ripple absorption necessity determination unit 83 determines whether the internal temperature of the first battery 20 is below a threshold value. This threshold value is set in advance by experimentally determining the relationship between the ripple current and the internal temperature of the first battery 20, and is set to a value that allows for the influence of the ripple current on the target value of the SOC of the first battery 20. If it is determined in step S6 that the internal temperature of the first battery 20 is below the threshold value, the ripple current absorption signal generation unit 84 generates a ripple current absorption signal and transmits it to the conversion control unit 85 in step S7.

[0048] On the other hand, if it is determined in step S3 that the SOC of the first battery 20 does not exceed the first threshold, if it is determined in step S4 that the first battery 20 is not discharging, or if it is determined in step S5 that the internal temperature of the first battery 20 is not below the threshold, the process proceeds to step S8. In step S8, the ripple current absorption signal generation unit 84 does not transmit a ripple current absorption signal to the conversion control unit 85.

[0049] In step S9 following steps S7 and S8, the conversion control unit 85 performs DC / DC conversion control by controlling the switching elements Q1 to Q8. When the conversion control unit 85 receives a ripple current absorption signal from the ripple current absorption signal generation unit 84, the conversion control unit 85 performs first conversion control in which the ripple current is absorbed using the ripple current absorption signal, and otherwise performs second conversion control in which the ripple current is not absorbed using the ripple current absorption signal.

[0050] According to the embodiment described above, the controller 80 transmits a ripple current absorption signal to the conversion control unit 85 to absorb the ripple current in the connection line 53 based on the current at the DC side terminal 52 of the AC / DC converter 50, causing the conversion control unit 85 to control the DC / DC converter 60 to absorb the ripple current. This eliminates the need for additional components such as switches or relays to switch the circuit from a single-stage charging circuit to a two-stage charging circuit, thereby suppressing current ripple while minimizing costs. Furthermore, using an AC / DC converter 50 with a single-stage charging circuit can further reduce costs.

[0051] According to this embodiment, the controller 80 transmits a signal to the conversion control unit 85 to absorb the ripple current when charging of the first battery 20 starts and the SOC of the first battery 20 exceeds the first threshold, or when discharging of the first battery 20 starts and the SOC of the first battery 20 falls below the second threshold. That is, the controller 80 determines whether the SOC of the first battery 20 reaches the threshold for charging or discharging and turns on or off transmission of the ripple current absorption signal depending on the determination result. Since highly accurate determination of charge completion or discharge stop is not required during the period immediately after the start of charging or discharging of the first battery 20 until immediately before the completion of charging or discharging, the power consumption required for absorbing the ripple current is reduced by not transmitting the ripple current absorption signal and stopping the DC / DC converter 60. On the other hand, since highly accurate determination of charge completion or discharge stop is required during the period immediately before the completion of charging or discharging, the ripple current absorption signal is transmitted and the ripple current is absorbed, thereby enabling accurate determination of charge completion or discharge stop.

[0052] According to the embodiment, when the internal temperature of the first battery 20 falls below the threshold, the controller 80 transmits a ripple current absorption signal to the conversion control unit 85. Therefore, when the internal temperature of the first battery 20 is high, that is, when the internal resistance is small due to the temperature characteristics, the ripple voltage caused by the ripple current flowing into the internal resistance is small, and the impact on the accuracy of charge / discharge completion is small, the ripple current absorption operation is stopped, thereby reducing the power consumption required for the ripple current absorption operation.

[0053] According to the embodiment, the controller 80 controls the amount of ripple current absorption in the DC / DC converter 60 based on the result of comparing the loss caused by the ripple current flowing in the first battery 20 with the loss caused by absorbing the ripple current in the DC / DC converter 60. Therefore, the power consumption in the DC / DC converter 60 due to the ripple current absorption operation is optimally controlled in accordance with the loss caused by the ripple current in the first battery 20, so that when charging or discharging the first battery 20, charging or discharging can be performed in consideration of the charging efficiency or discharging efficiency of the entire charging system 10.

[0054] [Second embodiment] Fig. 9 is a schematic diagram showing the general configuration of a charging system 10A including a charging device 40A according to a second embodiment. As shown in Fig. 9, the charging system 10A and charging device 40A of this embodiment differ from those of the first embodiment in that the DC / DC converter 60A is a unidirectional type that can only allow current to flow in a direction from the first battery 20 to the second battery 30 when absorbing ripple current.

[0055] The DC / DC converter 60A includes a first switching circuit 61 , a first smoothing capacitor 62 , a second switching circuit 63A, a second smoothing capacitor 64 , and an isolation transformer 65 .

[0056] The second switching circuit 63A includes diodes D9 and D10 instead of the switching elements Q5, Q6, Q7, and Q8 and the diodes D5, D6, D7, and D8 of the first embodiment.

[0057] In the above-described charging system 10A and charging device 40A, if the ripple current output by AC / DC converter 50 exceeds the target current, the current supplied to first battery 20 is excessive, and DC / DC converter 60A absorbs the current to reduce the current to first battery 20. On the other hand, if the ripple current output by AC / DC converter 50 is below the target current, DC / DC converter 60A is stopped. Even in this case, DC / DC converter 60 can absorb the ripple current.

[0058] According to this embodiment, there is no need for additional components such as switches or relays for switching the circuit from a one-stage charging circuit to a two-stage charging circuit, so current ripple can be suppressed while preventing an increase in costs.

[0059] As described above, the best configurations, methods, and the like for implementing the present invention have been disclosed in the above description, but the present invention is not limited thereto. That is, although the present invention has been particularly illustrated and described mainly with reference to specific embodiments, those skilled in the art can make various modifications to the above-described embodiments in terms of shape, material, quantity, and other detailed configurations without departing from the scope of the technical idea and purpose of the present invention. Furthermore, the above-disclosed descriptions limiting the shape, material, and the like are provided as examples to facilitate understanding of the present invention and are not intended to limit the present invention. Therefore, descriptions using names of components that are free from some or all of the limitations on shape, material, and the like are included in the present invention.

[0060] The charging system 10, 10A and the charging device 40, 40A may be used in, for example, a train, an airplane, or a ship, or may be installed in a building.

[0061] The AC / DC converter 50 may include a two-stage charging circuit.

[0062] Controller 80 may be configured integrally with DC / DC converters 60, 60A, or may be configured separately from DC / DC converters 60, 60A. Controller 80 may be configured with one or more of memory unit 81, SOC calculation unit 82, ripple absorption necessity determination unit 83, ripple current absorption signal generation unit 84, and conversion control unit 85 separated from the remaining elements; for example, memory unit 81, SOC calculation unit 82, ripple absorption necessity determination unit 83, and ripple current absorption signal generation unit 84 may be configured collectively separately from DC / DC converters 60, 60A, and conversion control unit 85 may be configured integrally with DC / DC converters 60, 60A.

[0063] 20...first battery, 30...second battery, 40, 40A...charging device, 50...AC / DC converter, 51...AC side terminal, 52...DC side terminal, 53...connection line, 60, 60A...DC / DC converter, 66...one terminal, 67...other terminal, 80...controller, 85...conversion control section

Claims

1. A control method for a charging device comprising: an AC / DC converter having an AC side terminal connected to an AC power source or an AC load and a DC side terminal connected to a first battery, for charging or discharging the first battery; and a DC / DC converter having one terminal connected to a connection line connecting the AC / DC converter and the first battery, and the other terminal connected to a second battery or a DC device, the control method comprising: transmitting a signal to a conversion control unit of the DC / DC converter to absorb ripple current in the connection line based on the current at the DC side terminal of the AC / DC converter; and causing the conversion control unit to control the DC / DC converter to absorb the ripple current.

2. A control method according to claim 1, wherein a signal to absorb the ripple current is sent to the conversion control unit when charging of the first battery starts and the SOC of the first battery exceeds a first threshold, or when discharging of the first battery starts and the SOC of the first battery falls below a second threshold.

3. A control method according to claim 1 or 2, wherein a signal to absorb the ripple current is sent to the conversion control unit when the internal temperature of the first battery falls below a threshold.

4. A control method according to claim 1 or claim 2, wherein the amount of ripple current absorbed by the DC / DC converter is controlled based on a comparison result between the loss caused by the ripple current flowing to the first battery and the loss caused by absorbing the ripple current by the DC / DC converter.

5. A charging device comprising: an AC / DC converter having an AC side terminal connected to an AC power source or an AC load and a DC side terminal connected to a first battery, for charging or discharging the first battery; a DC / DC converter having one terminal connected to a connection line connecting the AC / DC converter and the first battery, and the other terminal connected to a second battery or a DC device; and a controller that sends a signal to a conversion control unit of the DC / DC converter to absorb ripple current in the connection line based on the current at the DC side terminal of the AC / DC converter, and causes the conversion control unit to control the DC / DC converter to absorb the ripple current.

Images