Charging and discharging system

Abstract

To provide a charging and discharging system capable of suppressing the amount of hardware.SOLUTION: A charging and discharging system includes first DC-DC converters for charging and discharging first batteries, and at least one second DC-DC converter that is connected to the first DC-DC converters in parallel with the first batteries and charges and discharges at least one second battery. The first DC-DC converter discharges the first battery, and transmits, to at least one second DC-DC converter, the voltage of the first battery for discharging power to the at least one second battery. The at least one second DC-DC converter corrects its own output voltage from its own output voltage and the voltage of the first battery, and discharges the second battery based on its own output voltage after correction.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a charging / discharging system for charging / discharging a battery. [Background technology]

[0002] Patent Document 1 describes a charging device that includes a plurality of chargers that are capable of independent charging operations. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-140120 A Summary of the Invention [Problem to be solved by the invention]

[0004] In a charging / discharging system that charges / discharges multiple batteries, if there is a large voltage drop due to the wiring between one battery and the DC-DC converter of the other battery, the DC-DC converter of the other battery cannot accurately detect the voltage of the one battery. This can be solved by providing wiring for voltage detection between the one battery and the DC-DC converter of the other battery. However, with this method, if n DC-DC converters of other batteries are connected to one battery, n sets of wiring will also increase, and the amount of hardware will increase.

[0005] An object of the present invention is to provide a charge / discharge system capable of reducing the amount of hardware required. [Means for solving the problem]

[0006] A charging / discharging system according to one embodiment of the present invention comprises: A charging / discharging system for charging / discharging a first battery and at least one second battery, an AC-DC converter that converts an input AC voltage into a DC voltage and converts the DC voltage into an output AC voltage; a capacitor connected to the AC-DC converter for storing DC power output from the AC-DC converter; a first DC-DC converter connected to the capacitor, charging the first battery using DC power stored in the capacitor, and discharging the first battery to output DC power to the capacitor; at least one second DC-DC converter connected in parallel with the first battery to the first DC-DC converter, charging the at least one second battery using DC power output from the first DC-DC converter, and discharging the at least one second battery to output DC power to the first DC-DC converter; Equipped with The first DC-DC converter is In a case of a discharging operation, a voltage of the first battery is sent to the at least one second DC-DC converter to discharge the first battery and to discharge power to the at least one second battery for suppressing the discharge power of the first battery; Each of the at least one second DC-DC converter comprises: In the case of a discharging operation, an output voltage of the own device is corrected based on an output voltage of the own device and a voltage of the first battery, and the second battery is discharged based on the corrected output voltage of the own device. It is characterized by:

[0007] In the charging / discharging system, The first DC-DC converter is In a case of a discharging operation, a target current setting value, a target voltage setting value, and a voltage of the first battery are transmitted to the at least one second DC-DC converter to discharge the first battery and to discharge power for suppressing the discharge power of the first battery to the at least one second battery; Each of the at least one second DC-DC converter comprises: In the case of a discharging operation, a correction value is calculated by subtracting the voltage of the first battery from the output voltage of the own device, and a corrected output voltage of the own device is calculated by subtracting the correction value from the output voltage of the own device, and a constant voltage output control or a constant current output control is performed based on the corrected output voltage of the own device, the target voltage setting value, and the target current setting value. It is characterized by:

[0008] In the charging / discharging system, Each of the at least one second DC-DC converter comprises: When the output voltage of the own device after the correction is lower than the target voltage setting value, constant current output control is performed with priority over constant voltage output control; When the output voltage of the own device after the correction is higher than the target voltage setting value, constant voltage output control is performed with priority over constant current output control. It is characterized by:

[0009] In the charging / discharging system, Each of the at least one second DC-DC converter comprises: A filtering process is performed with a predetermined time constant on the output voltage of the own device and the voltage of the first battery. It is characterized by:

[0010] In the charging / discharging system, The first DC-DC converter is When the voltage of the first battery is increasing, the target voltage setting value is made to follow the voltage of the first battery with a delay time greater than the time constant. It is characterized by:

[0011] In the charging / discharging system, The first DC-DC converter is Calculating the target voltage setting value by adding a predetermined offset to the voltage of the first battery; It is characterized by: Effect of the Invention

[0012] The charge / discharge system according to one aspect of the present invention has an effect of making it possible to reduce the amount of hardware. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a diagram showing a schematic configuration of a charge / discharge system of a first comparative example. [Diagram 2] FIG. 2 is a diagram showing a schematic configuration of a charge / discharge system of a second comparative example. [Diagram 3] FIG. 3 is a diagram showing a schematic configuration of the charge / discharge system according to the embodiment. [Figure 4] FIG. 4 is a diagram showing a circuit configuration of the charge / discharge system according to the embodiment. [Diagram 5] FIG. 5 is a diagram illustrating an example of voltages detected in each of the DC-DC converters according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a charge / discharge system according to the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the embodiment.

[0015] An embodiment will be described below, but in order to facilitate understanding of the embodiment, a comparative example will be described first.

[0016] In the comparative example and the embodiment, the number of batteries is four in total, but the present disclosure is not limited to this. The number of batteries may be two or more in total.

[0017] <First Comparative Example> 1 is a diagram showing a schematic configuration of a charge / discharge system of a first comparative example. The charge / discharge system 101 receives an input AC voltage from an AC power source 7 and charges batteries BATT0 to BATT3. The charge / discharge system 101 also discharges batteries BATT0 to BATT3 and outputs an output AC voltage to a load 8.

[0018] The charging / discharging system 101 includes an AC-DC converter 2, a DC-DC converter 3, and DC-DC converters 102 to 105.

[0019] Each of AC-DC converter 2, DC-DC converter 3, and DC-DC converters 102 to 105 is a bidirectional converter.

[0020] One side (AC input / output side, right side in FIG. 1) of AC-DC converter 2 is electrically connected to AC power supply 7 via switch SW1 when charging batteries BATT0 to BATT3. In this case, AC-DC converter 2 converts the input AC voltage into a DC voltage and outputs it to DC-DC converter 3. That is, in this case, AC-DC converter 2 performs AC-DC conversion.

[0021] When discharging batteries BATT0 to BATT3, one side of AC-DC converter 2 is electrically connected to load 8 via switch SW2. In this case, AC-DC converter 2 converts the DC voltage output from DC-DC converter 3 into an output AC voltage and outputs it to load 8. That is, in this case, AC-DC converter 2 performs DC-AC conversion.

[0022] One side (right side in FIG. 1) of DC-DC converter 3 is electrically connected to the other side (DC input / output side, left side in FIG. 1) of AC-DC converter 2. The other side (left side in FIG. 1) of DC-DC converter 3 is electrically connected to DC-DC converters 102 to 105.

[0023] When charging batteries BATT0 to BATT3, DC-DC converter 3 converts the direct current voltage output from AC-DC converter 2 and outputs it to DC-DC converters 102 to 105.

[0024] When discharging batteries BATT0 to BATT3, DC-DC converter 3 converts the direct current voltages output from DC-DC converters 102 to 105 and outputs the converted voltages to AC-DC converter 2.

[0025] In addition, the DC-DC converter 3 is provided with reinforced insulation (JIS C 6950-1:2016) in order to ensure isolation between the AC power supply 7 and the batteries BATT0 to BATT3. The reinforced insulation is, for example, realized by a transformer.

[0026] One side (the right side in FIG. 1) from DC-DC converter 102 to DC-DC converter 105 is connected in parallel and electrically connected to DC-DC converter 3. The other side (the left side in FIG. 1) from DC-DC converter 102 to DC-DC converter 105 is electrically connected to batteries BATT0 to BATT3, respectively.

[0027] When charging batteries BATT0 to BATT3, DC-DC converters 102 to 105 respectively convert the direct current voltage output from DC-DC converter 3 and output the converted voltage to batteries BATT0 to BATT3, respectively.

[0028] When batteries BATT0 to BATT3 are discharged, DC-DC converters 102 to 105 convert the DC voltages output from batteries BATT0 to BATT3 and output the converted voltages to DC-DC converter 3.

[0029] The charging / discharging system 101 includes a total of six converters, namely, an AC-DC converter 2, a DC-DC converter 3, and DC-DC converters 102 to 105. The only converter that is provided with reinforced insulation is the DC-DC converter 3.

[0030] <Second Comparative Example> 2 is a diagram showing a schematic configuration of a charge / discharge system of Comparative Example 2. Note that, among the components of the charge / discharge system 111, the same components as those of the charge / discharge system 101 are denoted by the same reference numerals and description thereof will be omitted.

[0031] The charging / discharging system 111 includes an AC-DC converter 2 and DC-DC converters 112 to 115 .

[0032] Each of DC-DC converters 112 to 115 is a bidirectional converter.

[0033] One side (right side in FIG. 2) of the DC-DC converters 112 to 115 is connected in parallel and electrically connected to the other side (DC input / output side, left side in FIG. 2) of the AC-DC converter 2. The other sides (left side in FIG. 2) of the DC-DC converters 112 to 115 are electrically connected to batteries BATT0 to BATT3, respectively.

[0034] When charging batteries BATT0 to BATT3, DC-DC converters 112 to 115 respectively convert the DC voltage output from AC-DC converter 2 and output the converted voltage to batteries BATT0 to BATT3, respectively.

[0035] When batteries BATT0 to BATT3 are discharged, DC-DC converters 112 to 115 convert the DC voltages output from batteries BATT0 to BATT3, respectively, and output the converted voltages to AC-DC converter 2.

[0036] Each of DC-DC converters 112 to 115 is provided with reinforced insulation in order to ensure isolation between AC power supply 7 and batteries BATT0 to BATT3.

[0037] The charging / discharging system 111 includes a total of five converters, namely, the AC-DC converter 2, and DC-DC converters 112 to 115. The converters for which reinforced insulation is provided are the four in total, namely, the DC-DC converters 112 to 115.

[0038] <Embodiment Mode> (Summary configuration) 3 is a diagram showing a schematic configuration of a charge / discharge system according to an embodiment. Among the components of the charge / discharge system 1, the same components as those of the charge / discharge system 101 or 111 are denoted by the same reference numerals and description thereof will be omitted.

[0039] The charging / discharging system 1 includes an AC-DC converter 2, a DC-DC converter 3, and DC-DC converters 4 to 6.

[0040] The DC-DC converter 3 corresponds to an example of a "first DC-DC converter" of the present disclosure.

[0041] Each of DC-DC converters 4 to 6 is a bidirectional converter.

[0042] DC-DC converter 4 to DC-DC converter 6 correspond to an example of a "second DC-DC converter" of the present disclosure.

[0043] The battery BATT0 is electrically connected to the other side of the DC-DC converter 3 (the left side in FIG. 3).

[0044] The battery BATT0 corresponds to an example of a "first battery" in the present disclosure.

[0045] One side (right side in FIG. 3) from the DC-DC converter 4 to the DC-DC converter 6 is connected in parallel to the battery BATT0 and is electrically connected to the DC-DC converter 3. The other side (left side in FIG. 3) from the DC-DC converter 4 to the DC-DC converter 6 is electrically connected to the batteries BATT1 to BATT3, respectively.

[0046] The batteries BATT1 to BATT3 correspond to an example of "at least one second battery" in the present disclosure.

[0047] When charging batteries BATT0 to BATT3, DC-DC converter 3 converts the DC voltage output from AC-DC converter 2 and outputs it to battery BATT0, as well as to DC-DC converters 4 to 6.

[0048] When discharging batteries BATT0 to BATT3, DC-DC converter 3 converts the DC voltages output from battery BATT0 and DC-DC converters 4 to 6, and outputs the converted voltages to AC-DC converter 2.

[0049] When charging batteries BATT1 to BATT3, DC-DC converters 4 to 6 convert the DC voltage output from DC-DC converter 3 and output it to batteries BATT1 to BATT3, respectively.

[0050] When batteries BATT1 to BATT3 are discharged, DC-DC converters 4 to 6 convert the DC voltages output from batteries BATT1 to BATT3 and output them to DC-DC converter 3.

[0051] The charging / discharging system 1 includes a total of five converters, namely, an AC-DC converter 2, a DC-DC converter 3, and DC-DC converters 4 to 6. The only converter that is provided with reinforced insulation is the DC-DC converter 3.

[0052] Compared with the charge / discharge system 101, the charge / discharge system 1 can reduce the number of converters from six to five. Therefore, compared with the charge / discharge system 101, the charge / discharge system 1 can reduce costs, reduce size, and improve power conversion efficiency.

[0053] Compared with the charge / discharge system 111, the charge / discharge system 1 can reduce the number of converters with reinforced insulation from four to one. Therefore, compared with the charge / discharge system 111, the charge / discharge system 1 can reduce costs and size.

[0054] However, in the configuration of the charging / discharging system 1 shown in Fig. 3, the battery BATT0 and the DC-DC converters 4 to 6 are connected in parallel, so control becomes important. The control of the charging / discharging system 1 will be described later.

[0055] (Circuit configuration) FIG. 4 is a diagram showing a circuit configuration of the charge / discharge system according to the embodiment.

[0056] One side (AC input / output side, right side in FIG. 4) of the AC-DC converter 2 is electrically connected to an AC power source 7 or a load 8 (see FIG. 3) via a filter 11. The other side (DC input / output side, left side in FIG. 4) of the AC-DC converter 2 is electrically connected to a capacitor 12.

[0057] A full bridge circuit is exemplified as the AC-DC converter 2, but the present disclosure is not limited thereto. The AC-DC converter 2 may be any converter capable of bidirectional conversion between AC and DC and DC and AC.

[0058] When charging batteries BATT0 to BATT3, AC-DC converter 2 converts the input AC voltage into a DC voltage and outputs it to capacitor 12. That is, in this case, AC-DC converter 2 performs AC-DC conversion.

[0059] When discharging batteries BATT0 to BATT3, AC-DC converter 2 converts the DC voltage of capacitor 12 into an output AC voltage and outputs it to load 8 (see FIG. 3). That is, in this case, AC-DC converter 2 performs DC-AC conversion.

[0060] The DC-DC converter 3 includes a converter section 3a, a control section 3b, voltage sensors 3c and 3d, and a current sensor 3e.

[0061] The converter unit 3a is exemplified by a DAB (Dual Active Bridge) circuit. The converter unit 3a is not limited to a DAB circuit. The converter unit 3a may have a reinforced insulation function and may perform DC-DC conversion. For example, the converter unit 3a may be a step-up / step-down chopper circuit.

[0062] One side (the right side in FIG. 4) of the converter unit 3a is electrically connected to the capacitor 12.

[0063] The voltage sensor 3c detects the voltage on one side of the converter section 3a, that is, the voltage V of the capacitor 12. dc and outputs a detection signal to the control unit 3b.

[0064] The other side (the left side in FIG. 4) of the converter unit 3a is electrically connected to the battery BATT0.

[0065] The voltage sensor 3d detects the voltage on the other side of the converter unit 3a, that is, the voltage V0 of the battery BATT0, and outputs a detection signal to the control unit 3b.

[0066] The current sensor 3e detects a current A0 flowing between the other side of the converter unit 3a and the battery BATT0, and outputs a detection signal to the control unit 3b.

[0067] The control unit 3b controls the voltage V dc , and controls the converter unit 3a based on the voltage V0 and the current A0.

[0068] The power bus PBUS includes a high-potential side wiring PBUSa and a low-potential side wiring PBUSb. The wiring PBUSa is electrically connected to the high-potential side end of the other side of the converter unit 3a. The wiring PBUSb is electrically connected to the low-potential side end of the other side of the converter unit 3a via the switch SW3.

[0069] The control bus CBUS is electrically connected to the control unit 3b. The control bus CBUS is exemplified by a Controller Area Network (CAN, ISO 11898), but the present disclosure is not limited thereto.

[0070] The DC-DC converter 4 includes a converter unit 4a, a control unit 4b, a voltage sensor 4c, and a current sensor 4d.

[0071] The converter section 4a is exemplified by a bidirectional buck-boost chopper circuit, but the present disclosure is not limited thereto. The converter section 4a may be any circuit capable of DC-DC conversion. The converter section 4a does not need to have reinforced insulation.

[0072] One side (the right side in FIG. 4) of the converter unit 4a is electrically connected to the power bus PBUS, and the other side (the left side in FIG. 4) of the converter unit 4a is electrically connected to the battery BATT1.

[0073] The voltage sensor 4c detects the voltage V 1B and outputs a detection signal to the control unit 4b.

[0074] The current sensor 4d detects a current A flowing between one side of the converter unit 4a and the power bus PBUS. 1B and outputs a detection signal to the control unit 4b.

[0075] The control unit 4b controls the voltage V 1B and current A 1B Based on this, the converter unit 4a is controlled.

[0076] The DC-DC converter 5 includes a converter unit 5a, a control unit 5b, a voltage sensor 5c, and a current sensor 5d.

[0077] The converter section 5a is exemplified by a bidirectional buck-boost chopper circuit, but the present disclosure is not limited thereto. The converter section 5a may be any circuit capable of DC-DC conversion. The converter section 5a does not need to have reinforced insulation.

[0078] One side (the right side in FIG. 4) of the converter unit 5a is electrically connected to the power bus PBUS, and the other side (the left side in FIG. 4) of the converter unit 5a is electrically connected to the battery BATT2.

[0079] The voltage sensor 5c detects the voltage V 2B and outputs a detection signal to the control unit 5b.

[0080] The current sensor 5d detects a current A flowing between one side of the converter unit 5a and the power bus PBUS. 2B and outputs a detection signal to the control unit 5b.

[0081] The control unit 5b controls the voltage V 2B and current A 2B Based on this, the converter unit 5a is controlled.

[0082] The DC-DC converter 6 includes a converter unit 6a, a control unit 6b, a voltage sensor 6c, and a current sensor 6d.

[0083] The converter section 6a is exemplified by a bidirectional step-up / step-down chopper circuit, but the present disclosure is not limited thereto. The converter section 6a may be any circuit capable of DC-DC conversion. The converter section 6a does not need to have reinforced insulation.

[0084] One side (the right side in FIG. 4) of the converter unit 6a is electrically connected to the power bus PBUS, and the other side (the left side in FIG. 4) of the converter unit 6a is electrically connected to the battery BATT3.

[0085] The voltage sensor 6c detects the voltage V 3B and outputs a detection signal to the control unit 6b.

[0086] The current sensor 6d detects a current A flowing between one side of the converter unit 6a and the power bus PBUS. 3B and outputs a detection signal to the control unit 6b.

[0087] The control unit 6b controls the voltage V 3B and current A 3B Based on this, the converter unit 6a is controlled.

[0088] (Charging operation) The AC-DC converter 2 takes in power from an AC power source 7 (see FIG. 3) at a rated power (e.g., 1500 W) and outputs it to the capacitor 12. The DC-DC converter 3 charges the battery BATT0 using a part of the DC power output from the AC-DC converter 2 to the capacitor 12. For example, the DC-DC converter 3 charges the battery BATT0 at a rated current or lower and a rated voltage or lower of the battery BATT0. That is, the control unit 3b controls the converter unit 3a with CC (constant current) / CV (constant voltage). Note that the control unit 3b may prioritize CC control over CV control. The control unit 3b can appropriately control the charging current of the battery BATT0 because the DC-DC converter 3 includes a current sensor 3e.

[0089] The control unit 3b distributes the remaining power, that is, the power obtained by subtracting the charging power of the battery BATT0 from the power supplied by the AC-DC converter 2, to the DC-DC converters 4 to 6. For example, if the rated power of the battery BATT0 is 500 W, the remaining power is 1000 W (=1500 W-500 W).

[0090] For example, when the control unit 3b is to share the remaining power evenly among the DC-DC converters 4 to 6, it divides the remaining power (1000 W) by the number of DC-DC converters 4 to 6 (3) to obtain the power (1000 W ÷ 3 = 333 W) and transmits this as the target charging power setting value to the control units 4b, 5b, and 6b via the control bus CBUS (CP (constant power) control).

[0091] The control units 4b, 5b, and 6b charge the batteries BATT1 to BATT3, respectively, based on the target charging power setting value (333 W). That is, the control units 4b, 5b, and 6b perform CC / CV control of the converter units 4a, 5a, and 6a, respectively. The control units 4b, 5b, and 6b may prioritize CC control over CV control.

[0092] Note that the control unit 3b does not have to equally distribute the remaining power among the DC-DC converters 4 to 6. In other words, the control unit 3b may transmit a different target charging power setting value to each of the control units 4b, 5b, and 6b.

[0093] Alternatively, the control unit 3b may instruct the control units 4b, 5b, and 6b to discharge, charge, or stop charging / discharging the batteries BATT1 to BATT3, respectively.

[0094] (Discharge operation) [Normal Case] The DC-DC converter 3 discharges the battery BATT0 at a rated current or less of the battery BATT0. That is, the control unit 3b controls the converter unit 3a in a CC mode. The control unit 3b can appropriately control the discharge current of the battery BATT0 because the DC-DC converter 3 includes the current sensor 3e.

[0095] The control unit 3b also allocates the power consumption of the load 8 to the DC-DC converters 4 to 6. That is, the control unit 3b causes the batteries BATT1 to BATT3 to discharge power in order to suppress the power discharged from the battery BATT0.

[0096] Therefore, the control unit 3b sets the target A XB Current setting value, target V XB The voltage setting value and the master voltage V0 detection value are transmitted to the control units 4b, 5b and 6b via the control bus CBUS. XB The current setting value is the target current setting value of the output current of each of the DC-DC converters 4 to 6. XB The voltage set value is a target voltage set value for the output voltage of each of the DC-DC converters 4 to 6. The master voltage V0 detection value is the detection value of the voltage sensor 3d, that is, the voltage V0.

[0097] The control unit 4b controls the current A 1B Goal A XB The converter unit 4a is CC-controlled so that the current is set to a set value, and the voltage V 1B The goal is V XB The converter unit 4a is controlled in CV so as to achieve the voltage setting value, and the battery BATT1 is discharged. The control unit 4b may prioritize CC control over CV control. The control unit 4b uses the detected value of the master voltage V0 in a voltage correction operation described later.

[0098] The control units 5b and 6b perform the same control as the control unit 4b.

[0099] The control unit 3b does not have to discharge the DC-DC converters 4 to 6 evenly. In other words, the control unit 3b may set different targets A for each of the control units 4b, 5b, and 6b. XB Current setting and target V XB A voltage setting value may also be transmitted.

[0100] Alternatively, the control unit 3b may instruct the control units 4b, 5b, and 6b to discharge, charge, or stop charging / discharging the batteries BATT1 to BATT3, respectively.

[0101] [When the load power consumption suddenly decreases] An example of discharge control in the case where the power consumption of the load suddenly decreases (hereinafter, referred to as "sudden load decrease") will be described.

[0102] (A) When the load suddenly decreases, the voltage V of capacitor 12 dc increases. (B) Voltage V dc When increases, the control unit 3b controls the converter unit 3a to suppress discharging of the battery BATT0. (C) However, there is a time lag until the control units 4b, 5b, and 6b shift from CC control to CV control and suppress discharge. Therefore, the control unit 3b controls the converter unit 3a to output the power supplied from the DC-DC converters 4 to 6 to the capacitor 12. (D) Then, the voltage V dc becomes an overvoltage, the control unit 3b stops the operation of the converter unit 3a. Therefore, the power output from the DC-DC converters 4 to 6 unintentionally flows into the battery BATT0. At this time, the voltage of the power bus PBUS (voltage V 1B , V 2B and V 3B ) rises, which prompts the control units 4b, 5b, and 6b to shift from CC control to CV control. (E) Thereafter, the transition to CV control of the control units 4b, 5b and 6b is completed, and the outputs of the DC-DC converters 4 to 6 are suppressed.

[0103] As described in (D) above, it may happen that the power output from the DC-DC converters 4 to 6 unintentionally flows into the battery BATT0. Therefore, in the charge / discharge system 1, the following control (B') is performed instead of the above (B).

[0104] (B') Voltage V dc When the voltage V dc The converter unit 3a is controlled so that the power due to the increase in the voltage V is regenerated and the battery BATT0 is charged within the specification range (for example, the rated voltage). 1B , V 2B and V 3B ) rises, the transition from CC control to CV control of the control sections 4b, 5b and 6b is further promoted than in the above (D).

[0105] By configuring the converter unit 3a as a seamless bidirectional type, it is possible to seamlessly shift from charging the battery BATT0 to charging the capacitor 12, or from charging the capacitor 12 to charging the battery BATT0.

[0106] In this way, the DC-DC converter 3 outputs the voltage V dc By regenerating the power generated by the increase in the voltage of the power bus PBUS and charging the battery BATT0, the voltage of the power bus PBUS can be increased while the DC-DC converter 3 is controllable (before the operation is stopped). This further facilitates the transition of the DC-DC converters 4 to 6 from CC control to CV control.

[0107] The charging / discharging system 1, configured as shown in Fig. 3 and Fig. 4, can appropriately charge / discharge the batteries BATT0 to BATT3 and can also appropriately handle a sudden load drop. This allows the number of DC-DC converters and the number of reinforced insulators to be reduced compared to the first and second comparative examples. This makes it possible to reduce costs, reduce size, and improve power conversion efficiency.

[0108] [Voltage correction operation] As described above, the control unit 4b controls the current A 1B Goal A XB The converter unit 4a is CC-controlled so that the current is set to a set value, and the voltage V 1B The goal is V XBThe converter unit 4a is CV controlled so as to achieve a voltage setting value, and the battery BATT1 is discharged. However, as will be described below, the control unit 4b controls the voltage V detected by the voltage sensor 4c. 1B After correcting, the corrected voltage V 1B_corrected The goal is V XB It is preferable to perform CV control on the converter unit 4a so as to achieve a voltage setting value. The same is true for the control units 5b and 6b.

[0109] The voltage correction operation of the charge / discharge system 1 will be described below.

[0110] In order to cause the control units 4b, 5b, and 6b to prioritize CC control over CV control, the control unit 3b adds a predetermined offset α to the voltage V0 detected by the voltage sensor 3d, thereby setting the target V XB That is, the control unit 3b calculates the voltage setting value. XB Set the voltage setting value to (V0+α).

[0111] In addition, the control unit 3b sets the target V XB The voltage setting value is made to follow the voltage V0 at a relatively high speed when the voltage V0 is dropping, and to follow the voltage V0 at a relatively low speed when the voltage V0 is rising. XB It is preferable that the delay time of the voltage setting value is greater than the time constant of a filter described later. In this way, each of the control units 4b, 5b, and 6b adjusts the voltage V XB_corrected The goal is V XB Since the voltage becomes higher than the set value, the transition to CV operation is promoted.

[0112] FIG. 5 is a diagram illustrating an example of voltages detected in each of the DC-DC converters according to the embodiment.

[0113] 4 and 5, the voltage V of the power bus PBUS detected by the voltage sensor 4c 1B (Output voltage of DC-DC converter 4) is the voltage V due to voltage drop etc. in the wiring between DC-DC converter 3 and DC-DC converter 4. 1busis higher than the voltage V0 by just 1. In other words, the following equation (1) holds true. V 1B =V0+V 1bus (1)

[0114] Similarly, the voltage V of the power bus PBUS detected by the voltage sensor 5c 2B (Output voltage of DC-DC converter 5) is the voltage V due to voltage drop etc. caused by the wiring between DC-DC converter 4 and DC-DC converter 5. 2bus Only the voltage V 1B That is, the following formula (2) holds true: V 2B =V 1B +V 2bus (2)

[0115] Similarly, the voltage V of the power bus PBUS detected by the voltage sensor 6c 3B (Output voltage of DC-DC converter 6) is the voltage V due to voltage drop etc. caused by the wiring between DC-DC converter 5 and DC-DC converter 6. 3bus Only the voltage V 2B That is, the following formula (3) holds true: V 3B =V 2B +V 3bus (3)

[0116] Referring to Figure 5, the voltage V 2B and voltage V 3B is the target V XB The control units 5b and 6b therefore prioritize CV control over CC control, so that the target A XB On the other hand, in order to make the control units 5b and 6b give priority to CC control over CV control, the target V XBIf the voltage setting value is set higher, that is, if the offset α is set higher, the sensitivity of the CV control will decrease when the load suddenly decreases. In other words, the control units 5b and 6b will delay the transition from CC control to CV control when the load suddenly decreases. This causes current to flow from the DC-DC converters 5 and 6 to the battery BATT0. In other words, each of the control units 4b, 5b, and 6b needs to relatively and accurately obtain the fluctuation of the voltage V0.

[0117] Therefore, in the embodiment, each of the control units 4b, 5b, and 6b detects the voltage V of the power bus PBUS. XB The correction value V is obtained by subtracting the detected master voltage V0 from XA That is, each of the control units 4b, 5b, and 6b calculates the correction value V XA Calculate. V XA =V XB -V0···(4)

[0118] Each of the control units 4b, 5b, and 6b controls the voltage V XB It is preferable to perform a filter process with a time constant of about 1 sec on the detected values ​​of the master voltage V0 and the master voltage V1. That is, each of the control units 4b, 5b, and 6b calculates a filtered correction value V XA_filtered It is preferable to calculate V XA_filtered =V XB_filtered -V 0_filtered (4')

[0119] This is because the fluctuation in voltage V0 when a sudden load drop occurs is corrected by the correction value V XA_filtered This is to delay the change being reflected in the results.

[0120] That is, each of the control units 4b, 5b, and 6b calculates the corrected voltage V XB_corrected Calculate. V XB_corrected =V XB -V XA_filtered =VXB -(V XB_filtered -V 0_filtered ) ···(5)

[0121] Voltage V of the own machine after correction XB_corrected is the target V XB It is lower than the voltage setting value by approximately the offset α.

[0122] To summarize the above, the control unit 4b controls the current A 1B Goal A XB The converter unit 4a is CC-controlled so that the current is set to the set value, and the voltage V 1B_corrected The goal is V XB The converter unit 4a is subjected to CV control so as to reach the voltage setting value, and the battery BATT1 is discharged.

[0123] The control units 5b and 6b perform the same control as the control unit 4b.

[0124] During normal discharge, V XB_corrected <Goal V XB Since the voltage is a set value, each of the control units 4b, 5b, and 6b prioritizes CC control over CV control. XB_corrected While rising, the target V XB Since the voltage setting value (V0+α) follows the voltage V0 at a relatively slow speed, V XB_corrected >Goal V XB Therefore, each of the control units 4b, 5b, and 6b quickly shifts from CC control to CV control, and therefore it is possible to suppress a decrease in the sensitivity of the CV control.

[0125] (effect) Each of the control units 4b, 5b, and 6b prioritizes CC control during normal discharge, and can suppress a decrease in sensitivity of CV control during a sudden load drop. In addition, there is no need to provide wiring for voltage detection between the control unit 3b and the control units 4b, 5b, and 6b. This makes it possible to reduce the amount of hardware.

[0126] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope of the invention and its equivalents described in the claims, as well as in the scope and spirit of the invention. [Explanation of symbols]

[0127] 1, 101, 111 Charging and discharging system 2 AC-DC Converter 3, 4, 5, 6, 102, . . ., 105, 112, . . ., 115 DC-DC converters 3a, 4a, 5a, 6a Converter section 3b, 4b, 5b, 6b control section 3c, 3d, 4c, 5c, 6c Voltage Sensors 3e, 4d, 5d, 6d Current Sensors 7 AC power supply 8. Load 11 Filters 12 Capacitor BATT0, BATT1, BATT2, BATT3 batteries CBUS Control Bus PBUS Power Bus SW1, SW2, SW3 switches

Claims

1. A charging / discharging system for charging / discharging a first battery and at least one second battery, an AC-DC converter that converts an input AC voltage into a DC voltage and converts the DC voltage into an output AC voltage; a capacitor connected to the AC-DC converter for storing DC power output from the AC-DC converter; a first DC-DC converter connected to the capacitor, charging the first battery using DC power stored in the capacitor, and discharging the first battery to output DC power to the capacitor; at least one second DC-DC converter, each connected in parallel with the first battery to the first DC-DC converter, for charging the at least one second battery using DC power output from the first DC-DC converter, and for discharging the at least one second battery to output DC power to the first DC-DC converter; Equipped with The first DC-DC converter is In a case of a discharging operation, a voltage of the first battery is sent to the at least one second DC-DC converter to discharge the first battery and to discharge power to the at least one second battery for suppressing the discharge power of the first battery; Each of the at least one second DC-DC converter comprises: In the case of a discharging operation, an output voltage of the own device is corrected based on an output voltage of the own device and a voltage of the first battery, and the second battery is discharged based on the corrected output voltage of the own device. Charging and discharging system.

2. The first DC-DC converter is In a case of a discharging operation, a target current set value, a target voltage set value, and a voltage of the first battery are transmitted to the at least one second DC-DC converter to discharge the first battery and to discharge power for suppressing the discharge power of the first battery to the at least one second battery; Each of the at least one second DC-DC converter comprises: In the case of a discharging operation, a correction value is calculated by subtracting the voltage of the first battery from the output voltage of the own device, a corrected output voltage of the own device is calculated by subtracting the correction value from the output voltage of the own device, and a constant voltage output control or a constant current output control is performed based on the corrected output voltage of the own device, the target voltage setting value, and the target current setting value. The charging and discharging system according to claim 1 .

3. Each of the at least one second DC-DC converter comprises: When the output voltage of the own device after the correction is lower than the target voltage setting value, constant current output control is performed with priority over constant voltage output control; When the output voltage of the own device after the correction is higher than the target voltage setting value, constant voltage output control is performed with priority over constant current output control. The charging and discharging system according to claim 2 .

4. Each of the at least one second DC-DC converter comprises: filtering the output voltage of the vehicle and the voltage of the first battery with a predetermined time constant; The charging and discharging system according to claim 2 or 3.

5. The first DC-DC converter is When the voltage of the first battery is increasing, the target voltage setting value is made to follow the voltage of the first battery with a delay time greater than the time constant. The charging and discharging system according to claim 4 .

6. The first DC-DC converter is Calculating the target voltage setting value by adding a predetermined offset to the voltage of the first battery; The charge / discharge system according to claim 2 .

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