Power supply system

Abstract

This technology improves the efficiency of charging two batteries, which can be connected in series or parallel, using power from an onboard generator or an external power source. [Solution] The power supply system comprises a first battery, a second battery having the same configuration as the first battery, a voltage converter connected to an on-board power generator or an external power source, and a series-parallel switching circuit that can switch between a series connection of the first and second batteries and a parallel connection of the first and second batteries by switching multiple relays on and off. The system performs charge equalization control by alternately performing a first battery charging process that charges only the first battery by switching multiple relays on and off, and a charge equalization process that equalizes the charge storage ratio of the first battery and the charge storage ratio of the second battery.

Description

Technical Field

[0005]

[0001] The present disclosure relates to a power supply system, and more particularly to an in-vehicle power supply system including two batteries capable of charging and discharging by series connection and parallel connection.

Background Art

[0002] Conventionally, as this type of power supply system, a series-parallel battery system in which a plurality of batteries can be switched between series and parallel has been proposed (see, for example, Patent Document 1). In this system, the connection method at the start of charging is selected based on the temperature and SOC of the power supply device, and the charging current for the parallel connection method is controlled using an upper limit value larger than the upper limit value of the charging current for the series connection method input to the power supply device.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] As a method of charging two batteries, a method of connecting the two batteries in series and charging the two batteries simultaneously, a method of connecting the two batteries in parallel and charging the two batteries simultaneously, a method of alternately connecting the two batteries to a power source and charging them alternately, etc. can be considered. In the method of connecting the two batteries in series and charging them simultaneously, it is necessary to increase the power supply voltage. In the method of connecting the two batteries in parallel and charging them, it is necessary to increase the power supply current. In the method of alternately charging the two batteries, if the losses in the circuit for charging one battery and the losses in the circuit for charging the other battery are different, the charging efficiency will decrease.

[0005] The primary purpose of the power supply system disclosed herein is to improve the efficiency of charging two batteries, which can be connected in series or in parallel, using power from an onboard generator or an external power source. [Means for solving the problem]

[0006] The power supply system disclosed herein employs the following means to achieve the primary objectives described above.

[0007] The power supply system disclosed herein is The first battery and, A second battery having the same configuration as the first battery, A power converter connected to an on-board power generator and / or an external power source, A series-parallel switching circuit having multiple relays, which can switch between a series connection of the first battery and the second battery and a parallel connection of the first battery and the second battery by turning the multiple relays on and off, A control device for driving and controlling the plurality of relays in the series-parallel switching circuit, An in-vehicle power supply system equipped with, When the control device charges the first battery and the second battery with power from the power generator or the external power source, it performs a charge equalization control that alternately performs a first battery charging process, which involves switching the plurality of relays on and off to charge only the first battery with power from the power generator or the external power source, and a charge equalization process, which involves switching the plurality of relays on and off to charge the second battery with power from the first battery, thereby equalizing the charge ratio of the first battery and the charge ratio of the second battery. It is characterized by the following:

[0008] The power supply system of this disclosure is mounted in a vehicle and comprises a first battery, a second battery having the same configuration as the first battery, a power converter connected to a vehicle-mounted power generator or external power source, a series-parallel switching circuit having a plurality of relays that can switch between a series connection of the first battery and the second battery and a parallel connection of the first battery and the second battery by turning the plurality of relays on and off, and a control device that drives and controls the plurality of relays of the series-parallel switching circuit. When the control device charges the first battery and the second battery with power from the power generator or external power source, it performs charge equalization control, which alternately performs a first battery charging process, which turns on and off the plurality of relays to charge only the first battery with power from the power generator or external power source, and a charge ratio equalization process, which turns on and off the plurality of relays to charge the second battery with power from the first battery, thereby equalizing the charge ratio of the first battery and the charge ratio of the second battery. Since the equalization of the charge levels of the first and second batteries occurs in a relatively short time, both the first and second batteries can be charged in the same short time it would take to charge only the first battery using power from a power generator or external power source, thereby improving charging efficiency. In particular, when the losses in the circuit when charging the second battery using power from a power generator or external power source are greater than the losses in the circuit when charging the first battery, charging efficiency can be further improved.

[0009] In the power supply system of this disclosure, the control device may select the smaller of the losses when performing series connection charging control, which involves switching the plurality of relays on and off to connect the first battery and the second battery in series with power from the power generator or the external power source, and when performing charge equalization control, and charge the first battery and the second battery. This allows for more efficient charging of the first battery and the second battery.

[0010] In the power supply system of the present disclosure, the series-parallel switching circuit includes a series connection line connecting the negative terminal of the first battery and the positive terminal of the second battery, a series connection relay attached to the series connection line, a positive bus connected to the positive terminal of the first battery, a negative bus connected to the negative terminal of the second battery, an inverter connected to the positive bus and the negative bus, a three-phase AC motor driven by the inverter, a positive-side relay attached to the positive bus, a negative-side relay attached to the negative bus, and the series connection line from the series connection relay toward the first battery and in front of it. The power generation device and the external power supply may be connected via a power converter to a power line having a charging relay, with the positive terminal of [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic diagram showing the configuration of a power supply system 20 in one embodiment of the present disclosure. [Figure 2] This flowchart shows an example of a charging process performed by the electronic control unit 60. [Figure 3] This flowchart shows an example of charge equalization control performed by the electronic control unit 60. [Figure 4] This is an explanatory diagram showing an example of a circuit when charging only the first battery 26a. [Figure 5] This is an explanatory diagram showing an example of a circuit used in the equalization process. [Figure 6] This is an explanatory diagram showing an example of the charging process of the first battery 26a and the second battery 26b when the charge equalization control of the embodiment is performed and when the alternating charge control of the comparative example is performed. [Modes for carrying out the invention]

[0012] Next, embodiments for implementing this disclosure will be described. Figure 1 is a schematic diagram showing the configuration of an in-vehicle power supply system 20 as one embodiment of this disclosure. The power supply system 20 of this embodiment is mounted on an electric vehicle as a device that exchanges power between a battery 26 and an inverter 24 that drives a motor 22, and charges and discharges the battery 26 using the motor 22 and inverter 24 as needed. The power supply system 20 comprises a battery 26, a motor 22, an inverter 24, a main power supply circuit 30, an AC charging circuit 40, a DC charging circuit 50, and an electronic control unit 60. The motor 22 functions as an electric motor for driving the electric vehicle.

[0013] The motor 22 is configured as a well-known three-phase AC motor, comprising, for example, a rotor with permanent magnets attached to its outer surface and a stator around which three-phase coils are wound. The inverter 24 is composed of six transistors T1 to T6 as switching elements and six diodes D1 to D6 connected in parallel to the transistors T1 to T6 in the opposite direction. The transistors T1 to T6 are arranged in pairs such that the inverter 24 is on the source side and the sink side with respect to the positive bus 31B and negative bus 31G of the battery 26. Each of the three-phase coils (U-phase, V-phase, W-phase) of the motor 22 is connected to each of the connection points between the pairs of transistors T1 to T6. The inverter 24 rotates the motor 22 by controlling the ratio of the on-times of the pairs of transistors T1 to T6 while a voltage is acting between the positive bus 31B and the negative bus 31G, thereby forming a rotating magnetic field in the three-phase coils. A first smoothing capacitor 32 is installed between the positive busbar 31B and the negative busbar 31G.

[0014] The battery 26 comprises a first battery 26a and a second battery 26b configured similarly to the first battery 26a. The first battery 26a and the second battery 26b are configured as, for example, lithium-ion secondary batteries or nickel-metal hydride secondary batteries. The positive terminal of the first battery 26a is connected to the positive busbar 31B, and the negative terminal of the second battery 26b is connected to the negative busbar 31G. The negative terminal of the first battery 26a is connected to the positive terminal of the second battery 26b by a series power line 35 to which a relay DCRNN, which is included in the configuration of the main power circuit 30, is attached. Therefore, by turning on the relay DCRNN, the first battery 26a and the second battery 26b function as a single battery connected in series.

[0015] The main power supply circuit 30 includes a positive busbar 31B, a negative busbar 31G, a series power line 35, a first parallel power line 36 connecting the negative terminal of the first battery 26a to the negative busbar 31G, and a second parallel power line 37 connecting the positive terminal of the second battery 26b to the neutral point of the motor 22. A positive-side relay SMRB is attached to the positive busbar 31B, and a negative-side relay SMRG is attached to the negative busbar 31G. In addition, a pre-charge circuit consisting of a pre-charge relay SMRP and a resistor R is provided in parallel with the negative-side relay SMRG on the negative busbar 31G. These positive-side relay SMRB, negative-side relay SMRG, and pre-charge circuit constitute the system main relay. Specifically, when the first battery 26a and the second battery 26b are connected in series, the positive side relay SMRB is turned on and the pre-charge relay SMRP is turned on to charge the first capacitor 32. When the charging of the first capacitor 32 is complete, the negative side relay SMRG is turned on and the pre-charge relay SMP is turned off, thereby enabling power from the battery 26, consisting of the first battery 26a and the second battery 26b connected in series, to be supplied to the inverter 24, or conversely, the battery 26 to be charged by regenerative power from the motor 22.

[0016] A relay DCRNG is attached to the first parallel power line 36. A relay DCRNB is attached to the second parallel power line 37 on the side of the second battery 26b, and a relay DCRN is attached to the neutral point side of the motor 22. A second capacitor 38 is attached between the relay DCRNB and the relay DCRN on the second parallel power line 37 and the negative busbar 31G.

[0017] The AC charging circuit 40 includes an AC charging power line 41 connected to the positive busbar 31B and the negative busbar 31G, an on-board charger (OBC) 43 connected to the AC charging power line 41 via a filter 42, an AC charging connector 45 connected to the on-board charger 43 by a power line 44, a DC / DC converter 46 connected to the AC charging power line 41 via the filter 42 in parallel with the on-board charger 43, an auxiliary battery or auxiliary equipment 48a connected to the DC / DC converter 46 by a power line 47, and a solar panel 49. A relay SSRB is attached to the positive side line of the AC charging power line 41, and a relay SSRG is attached to the negative side line.

[0018] The DC charging circuit 50 includes a DC charging power line 51 connected to the positive busbar 31B and the negative busbar 31G, and a DC charging connector 55 connected to the DC charging power line 51. A relay DCRB is attached to the positive side line of the DC charging power line 51, and a relay DCRG is attached to the negative side line.

[0019] The electronic control unit 60 is configured as a microcomputer centered around a CPU, although not shown in the figure. Signals from various sensors are input to the electronic control unit 60. Examples of the various sensors include a voltage sensor 33 that detects the voltage VH between the terminals of the first capacitor 32, a voltage sensor 39 that detects the voltage VD between the terminals of the second capacitor 38, a current sensor 31a that detects the current Ib1 flowing through the first battery 26a, a current sensor 37a that detects the current Id flowing through the second parallel power line 37, a phase current sensor (not shown) that detects the phase currents Iu, Iv, Iw flowing through the three phases of the motor 22, a voltage sensor (not shown) that detects the voltage Vb1 between the terminals of the first battery 26a, and a voltage sensor (not shown) that detects the voltage Vb2 between the terminals of the second battery 26b. Since the electronic control unit 60 also functions as a control device for driving the motor 22, drive commands and the like are also input. When the power system 20 is mounted on a vehicle and the motor 22 is used as a driving motor, the accelerator opening and vehicle speed may be input to the electronic control unit 60, and the electronic control unit 60 may generate a torque command for the motor 22.

[0020] Drive control signals to each relay, switching control signals to the inverter 24, and the like are output from the electronic control unit 60. Examples of each relay include a positive-side relay SMRB, a negative-side relay SMRG, a precharge relay SMRP, a relay DCRNN, a relay DCRNG, a relay DCRNB, a relay DCRN, a relay SSRB, a relay SSRB, a relay DCRB, a relay DCRG, and the like.

[0021] When the power system 20 of the embodiment configured in this way drives the motor 22 as a driving motor and is running, the positive-side relay SMRB, the negative-side relay SMRG, the relay SSRB, the relay SSRG, and the relay DCRNN are in an on state, the relays DCRB, DCRG, DCRN, DCRB, and DCRG are in an off state, and the six transistors T1 to T6 of the inverter 24 are switched and controlled by PWM control or the like based on a torque command corresponding to the accelerator opening and the vehicle speed V.

[0022] Next, we will describe the operation when an AC power supply is connected to the AC charging connector 45 and the battery 26 is charged using power from the AC power supply, or when the battery 26 is charged using power generated by the solar panel 49. Figure 2 is a flowchart showing an example of the charging process performed by the electronic control unit 60 when the battery 26 is charged using power from the AC power supply or the solar panel 49, and Figure 3 is a flowchart showing an example of charge equalization control performed by the electronic control unit 60. Charge equalization control will be described later.

[0023] When the charging process is executed, the electronic control unit 60 determines whether the battery 26 is being charged by power from an AC power source or a solar panel 49 (step S100). If it is determined that the battery 26 is not being charged by power from an AC power source or a solar panel 49, for example, if an external DC power source is connected to the DC charging connector 55 and the battery 26 is being charged by power from the external DC power source, this process is not applicable, and the process is terminated.

[0024] In step S100, if it is determined that the battery 26 is being charged by power from an AC power source or a solar panel 49, the loss L1 is calculated when series connection charging control is performed to charge the first battery 26a and the second battery 26b in series, and the loss L2 is calculated when charge equalization control is performed to charge the first battery 26a and the second battery 26b by alternately repeating a first battery charging process that charges only the first battery 26a and an equalization process that equalizes the storage rate SOC1 of the first battery 26a and the storage rate SOC1 of the second battery 26b (step S110). In series connection charging control, relays SSRB, SSRG, and DCRNN are turned ON, and the positive side relay SMRB, negative side relay SMRG, relay DCRB, relay DCRG, relay DCRN, relay DCRNB, relay DCRB, and relay DCRG are turned OFF, and the battery 26 is charged by power from an AC power source or a solar panel 49. Loss L1 is the charging loss in series connection charging control, and is the loss in the circuit that returns from filter 42 through relay SSRB to positive bus 31B, first battery 26a, relay DCRNN, second battery 26b, negative bus 31G, relay SSRG, and back to filter 42. Charging equalization control and its loss L2 will be described later.

[0025] Next, the loss L1 when series connection charging control is performed is compared with the loss L2 when charge equalization control is performed (step S120). If it is determined that the loss L1 when series connection charging control is performed is less than the loss L2 when charge equalization control is performed, the series connection charging control is performed (step S130) and the process ends. On the other hand, if it is determined in step S120 that the loss L1 when series connection charging control is performed is greater than or equal to the loss L2 when charge equalization control is performed, the charge equalization control is performed (step S140) and the process ends.

[0026] In charge equalization control, as shown in the flowchart of Figure 3, the electronic control unit 60 first charges only the first battery 26a (step S200). This charging of only the first battery 26a is performed by turning on relays SSRB, SSRG, and DCRNG, while turning off the positive side relay SMRB, negative side relay SMRG, DCRNN, DCRB, DCRG, DCRN, DCRNB, DCRB, and DCRG, as shown in the explanatory diagram of Figure 4. This creates a circuit that returns from filter 42 to filter 42 via relay SSRB, then to positive bus 31B, the first battery 26a, relay DCRNG, the first parallel power line 36, the negative bus 31G, and relay SSRG.

[0027] Next, it is determined whether the difference between the charge storage ratio SOC1 of the first battery 26a and the charge storage ratio SOC1 of the second battery 26b (SOC1-SOC2) is greater than or equal to the threshold Sref (step S210). If it is determined that the difference between the charge storage ratio SOC1 of the first battery 26a and the charge storage ratio SOC1 of the second battery 26b (SOC1-SOC2) is greater than or equal to the threshold Sref, a process is performed to equalize the charge storage ratio SOC1 of the first battery 26a and the charge storage ratio SOC1 of the second battery 26b (step S220). This equalization process is performed by turning on the positive side relays SMRB, DCRNG, DCRN, and DCRNB, while turning off the relays SSRB, SSRG, positive side relay SMRB, negative side relay SMRG, DCRNN, DCRB, and DCRG. Furthermore, one, two, or all of the transistors T1, T2, and T3 of the inverter 24 are turned on, thereby forming a circuit from the positive terminal of the first battery 26a to the positive bus 31B, positive side relay SMRB, transistors T1, T2, and T3 of the inverter 24, motor 22, second parallel power line 37, relay DCRN, relay DCRNB, second battery 26b, negative bus 31G, first parallel power line 36, relay DCRNG, and the negative terminal of the first battery 26a. If, in step S210, it is determined that the difference between the charge level SOC1 of the first battery 26a and the charge level SOC1 of the second battery 26b (SOC1-SOC2) is less than the threshold Sref, then the equalization process is not performed.

[0028] Next, it is determined whether or not charging of battery 26 is complete (step S230). Completion of battery 26 charging includes when the first battery 26a and the second battery 26b are fully charged, or when preparations for starting driving are made. If it is determined that charging of battery 26 is not complete, the process returns to step S200, which charges only the first battery 26a. The process from step S200 to step S230 alternately repeats the process of charging only the first battery 26a until the difference between the charge level SOC1 of the first battery 26a and the charge level SOC2 of the second battery 26b is equal to or greater than the threshold Sref, and the process of equalizing the charge level SOC1 of the first battery 26a and the charge level SOC2 of the second battery 26b, until it is determined that charging is complete. Furthermore, the charge equalization control and its loss L2 are losses incurred when alternating between the process of charging only the first battery 26a and the process of equalizing the charge level SOC1 of the first battery 26a and the charge level SOC2 of the second battery 26b.

[0029] When it is determined in step S230 that charging is complete, an equalization process is performed (step S240) to terminate this process. The equalization process is performed at the end in order to make the charge level SOC1 of the first battery 26a and the charge level SOC2 of the second battery 26b the same.

[0030] Figure 6 is an explanatory diagram showing an example of the charging of the first battery 26a and the second battery 26b when the charge equalization control of the embodiment is performed and when the alternating charge control of the comparative example is performed. In the figure, the solid line represents the charge level SOC1 of the first battery 26a, and the dashed line represents the charge level SOC2 of the second battery 26b. The alternating charge control of the comparative example alternates between charging only the first battery 26a and charging only the second battery 26b. Furthermore, charging of only the second battery 26b is performed by turning on relays SSRB, SSRG, positive-side relay SMRB, relay DCRN, and relay DCRNB, while turning off negative-side relays SMRG, DCRNG, DCRNN, relay DCRB, and relay DCRG. Additionally, one, two, or all of transistors T1, T2, and T3 of inverter 24 are turned on, forming a circuit that returns from filter 42 via relay SSRB to positive bus 31B, positive-side relay SMRB, transistors T1, T2, and T3 of inverter 24, motor 22, second parallel power line 37, relay DCRN, relay DCRNB, second battery 26b, negative bus 31G, and relay SSRG, and returning to filter 42. In the comparative example's alternating charge control, charging only the second battery 26b involves significant losses because it passes through the inverter 24's transistors T1, T2, T3 and the motor 22. As a result, the charging time is longer and the charging efficiency decreases compared to charging only the first battery 26a. Therefore, when charging starts at time T1 when the battery 26's charge level SOC is value S1 and ends at time T2, the battery 26's charge level SOC becomes value S2. On the other hand, in the embodiment's charge equalization control, the equalization process also involves significant losses because it passes through the inverter 24's transistors T1, T2, T3 and the motor 22, similar to charging only the second battery 26b. However, since the equalization process is completed in a short time, the overall loss is small. When charging is primarily performed using only the first battery 26a, which has high charging efficiency, and charging begins at time T1 with the battery 26's state of charge (SOC) at value S1, and ends at time T2, the battery 26's SOC becomes a value S3, which is greater than the comparative example value S2.

[0031] In the power supply system 20 of the embodiment described above, when charging the battery 26 with power from an AC power source or a solar panel 49, if the loss L1 when performing series connection charging control is greater than or equal to the loss L2 when performing charge equalization control, charge equalization control is performed to charge the battery 26. Therefore, compared to the case where alternating charging control is performed, which alternately charges only the first battery 26a and only the second battery 26b, the charging time can be shortened and the charging efficiency can be increased.

[0032] In the power supply system 20 of this embodiment, when charging the battery 26 with power from an AC power source or a solar panel 49, the system selects the smaller of the loss L1 when series connection charging control is performed and the loss L2 when charge equalization control is performed to charge the battery 26. This makes it possible to further increase the charging efficiency.

[0033] The correspondence between the main elements of the embodiment and the main elements of the invention described in the section on means for solving the problem will be explained. In the embodiment, the first battery 26a corresponds to the "first battery," the second battery 26b corresponds to the "second battery," the solar panel 49 corresponds to the "power generation device," the onboard charger 43 and DC / DC converter 46 correspond to the "voltage converter," the main power supply circuit 30 corresponds to the "series-parallel switching circuit," the electronic control unit 60 corresponds to the "control device," and the power supply system 20 corresponds to the "power supply system."

[0034] Furthermore, the correspondence between the main elements of the embodiment and the main elements of the invention described in the section on means for solving the problem is merely an example to specifically explain the form in which the embodiment implements the invention described in the section on means for solving the problem, and does not limit the elements of the invention described in the section on means for solving the problem. In other words, the interpretation of the invention described in the section on means for solving the problem should be based on the description in that section, and the embodiment is merely one specific example of the invention described in the section on means for solving the problem.

[0035] Although the present disclosure has been described above using embodiments, the present disclosure is not limited in any way to these embodiments, and can of course be implemented in various forms without departing from the gist of the present disclosure. [Industrial applicability]

[0036] This disclosure can be used in industries such as the manufacturing of power supply systems. [Explanation of Symbols]

[0037] 20 Power system, 22 Motor, 24 Inverter, 26 Battery, 26a First battery, 26b Second battery, 30 Main power circuit, 31a Current sensor, 31B Blue busbar, 31G Negative busbar, 32 First capacitor, 33 Voltage sensor, 35 Series power line, 36 First parallel power line, 37 Second parallel power line, 37a Current sensor, 38 Second capacitor, 39 Voltage sensor, 40 AC charging circuit, 41 AC charging power line, 42 Filter, 43 Onboard charger, 44 Power line, 45 AC charging connector, 46 DC / DC converter, 47 Power line, 48 Auxiliary battery, 48a Auxiliary, 49 Solar panel, 50 DC charging circuit, 51 DC charging power line, 55 DC charging connector, 60 Electronic control unit.

Claims

1. The first battery and A second battery having the same configuration as the first battery, A power converter connected to an on-board power generator and / or an external power source, A series-parallel switching circuit having multiple relays, which can switch between a series connection of the first battery and the second battery and a parallel connection of the first battery and the second battery by turning the multiple relays on and off, A control device for driving and controlling the plurality of relays in the series-parallel switching circuit, An in-vehicle power supply system equipped with, When the control device charges the first battery and the second battery with power from the power generator or the external power source, it performs a charge equalization control that alternately performs a first battery charging process, which involves switching the plurality of relays on and off to charge only the first battery with power from the power generator or the external power source, and a charge equalization process, which involves switching the plurality of relays on and off to charge the second battery with power from the first battery, thereby equalizing the charge ratio of the first battery and the charge ratio of the second battery. An in-vehicle power supply system characterized by the following features.

2. An in-vehicle power supply system according to claim 1, The control device charges the first and second batteries by selecting the smaller of the losses when performing series connection charging control, which involves switching the plurality of relays on and off to connect the first and second batteries in series with power from the power generator or the external power source, and the losses when performing charge equalization control. A power supply system for vehicles.

3. A power supply system according to claim 1 or 2, The series-parallel switching circuit comprises a series connection line connecting the negative terminal of the first battery and the positive terminal of the second battery, a series connection relay attached to the series connection line, a positive bus connected to the positive terminal of the first battery, a negative bus connected to the negative terminal of the second battery, an inverter connected to the positive bus and the negative bus, a three-phase AC motor driven by the inverter, a positive-side relay attached to the positive bus, a negative-side relay attached to the negative bus, a first parallel connection line connecting the first battery side and the negative bus from the series connection relay on the series connection line, a first parallel connection relay attached to the first parallel connection line, a second parallel connection line connecting the positive terminal of the second battery and the neutral point of the three-phase AC motor, and a second parallel connection relay and a third parallel connection relay attached to the second parallel connection line in order from the second battery side. The power generator and the external power supply are connected via the power converter to a power line having a charging relay, from the positive side relay of the positive busbar to the first battery side and from the negative side relay of the negative busbar to the second battery side. Power supply system.

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