JP7746945B2 - Vehicle power supply unit - Google Patents

Description

This disclosure relates to a vehicle power supply device.

Patent Document 1 discloses a battery system in which multiple battery packs are connected to a power conversion device (hereinafter referred to as a PCU (Power Control Unit)). This technology equalizes the voltages of multiple battery packs based on the voltage of the battery packs.

JP 2014-103804 A

However, when multiple PCUs with battery packs of different voltages are connected in parallel, it is possible that an inrush current will flow from the higher-voltage PCU to the lower-voltage PCU when the power is turned on. This inrush current could cause system malfunctions or failures.

One objective of this disclosure is to provide technology that can prevent the occurrence of inrush current when the power supply is started.

The first aspect relates to a vehicle power supply device. The vehicle power supply device includes a first capacitor, a plurality of PCUs connected in parallel to the first capacitor, and a power storage device provided on the input side of each of the plurality of PCUs via a first relay. The output terminals of each of the plurality of PCUs are connected to a first positive power line connected to one end of the first capacitor and a first negative power line connected to the other end of the first capacitor. Each of the plurality of PCUs includes a boost converter, a multi-phase inverter, second positive power lines and second negative power lines connecting the boost converter and the multi-phase inverter, a second capacitor and a discharge resistor connected in parallel between the second positive power line and the second negative power line, and a second relay connected to the second positive power line and the second negative power line, respectively, and connected to the first positive power line and the first negative power line, respectively. The boost converter includes a first switching element having one end connected to the second positive power line, a second switching element having one end connected to the first switching element and the other end connected to the second negative power line, and a reactor having one end connected between the first switching element and the second switching element and the other end open. The output terminal of at least one of the multiple PCUs is connected to the first positive power line via a diode connected to the other end of the reactor.

According to the present disclosure, the vehicle power supply device has a feature in which the output terminal of at least one of the multiple PCUs is connected to the first positive power line via a diode connected to the other end of the reactor. This equalizes the voltages of the multiple PCUs when the power supply is started, preventing the generation of inrush current.

1 is a diagram illustrating an example of the configuration of a vehicle power supply device according to an embodiment; 3A and 3B are diagrams illustrating an example of operation of the vehicle power supply device according to the embodiment. 3A and 3B are diagrams illustrating an example of operation of the vehicle power supply device according to the embodiment.

A vehicle power supply device according to an embodiment of the present disclosure will be described with reference to the accompanying drawings.

Embodiment 1. Configuration Example of a Vehicle Power Supply Device Fig. 1 is a diagram showing a configuration example of a vehicle power supply device 1 according to an embodiment. The vehicle power supply device 1 is mounted on a vehicle. The vehicle on which the vehicle power supply device 1 is mounted is an electric vehicle equipped with a drive motor driven by a battery (i.e., a power storage device 20). The vehicle may be a manually driven vehicle or an automatically driven vehicle.

As shown in FIG. 1, the vehicle power supply device 1 installed in the vehicle is connected to, for example, an external device called a PCS (Power Conditioning System). A PCS is a device that converts power obtained from a commercial power source or the like into power usable by the vehicle or the like. The vehicle power supply device 1 charges and discharges the energy stored in the power storage device 20 via the PCS.

The vehicle power supply device 1 is composed of multiple power supply units 1A, 1B, ..., 1N connected in parallel, each consisting of a power storage device 20, a first relay 30, and a PCU 40. The vehicle power supply device 1 also includes a first capacitor 10 connected to a first positive power line 12 and a first negative power line 13 on the output side of the branch point of the multiple PCUs 40.

The energy storage device 20 is a device in which multiple battery packs, each consisting of multiple cells connected in series, are connected in parallel.

The first relay 30 is configured as an SMR (system main relay). The first relay 30 is connected to the power storage device 20 and the PCU 40. The first relay 30 may also be connected to, for example, a control device not shown in FIG. 1, and the ON/OFF switching of the first relay 30 may be controlled by the control device. This makes it possible to connect or disconnect the power storage device 20 and the PCU 40.

The PCU 40 is a power conversion device that converts power between the power storage device 20 and an external device (such as a PCS) to which the vehicle power supply device 1 is connected. The PCU 40 includes a boost converter 41, a second capacitor 45, a discharge resistor 46, a multi-phase inverter 47, and a second relay 48. The PCU 40 may also be a bidirectional device that converts power between the power storage device 20 and the external device.

The boost converter 41 and multi-phase inverter 47 are connected to the second positive power line 14 and the second negative power line 15, respectively. The second capacitor 45 and discharge resistor 46 are connected in parallel between the second positive power line 14 and the second negative power line 15. The second capacitor 45 smooths the DC voltage and charges and discharges energy, and the discharge resistor 46 discharges the energy stored in the second capacitor 45. The multi-phase inverter 47 converts the voltage of the energy stored in the second capacitor 45 to an arbitrary voltage. The boost converter 41 converts it to a voltage higher than the input voltage.

The second relay 48 has one end connected to the first positive power line 12 and the first negative power line 13, and the other end connected to the second positive power line 14 and the second negative power line 15. By controlling the ON/OFF switching of the second relay 48, the charging and discharging of the energy stored in the second capacitor 45 is controlled. Like the first relay 30, the second relay 48 may be connected to a control device, and the ON/OFF switching of the second relay 48 may be controlled by the control device.

The discharge resistor 46 is provided as a safety measure to prevent the energy stored in the second capacitor 45 from being discharged to the body even if the power plug on the vehicle power supply unit 1 that connects to the external device is touched after the connection to the external device is cut off. The polyphase inverter 47 shown in Figure 1 is an example of a three-level inverter, and is composed of three inverters: a first single-phase inverter, a second single-phase inverter, and a third single-phase inverter.

The boost converter 41 further includes a reactor 42, a first switching element 43, and a second switching element 44. The first switching element 43 and the second switching element 44 are connected in parallel, with the end of the first switching element 43 connected to the second positive power line 14 and the end of the second switching element 44 connected to the second negative power line 15. The reactor 42 is connected to the connection point between the first switching element 43 and the second switching element 44, and is connected to the second negative power line 15 via a third capacitor 49.

The reactor 42 serves to remove at least harmonic components such as the power supply frequency. The first switching element 43 and the second switching element 44 serve to adjust the output voltage of the PCU 40 to a predetermined voltage (i.e., the boosted voltage). Specifically, the output voltage of the PCU 40 is adjusted to a predetermined voltage by controlling the time and number of times each of the first switching element 43 and the second switching element 44 is switched ON/OFF. The first switching element 43 and the second switching element 44 may be connected to a control device, similar to the first relay 30 and the second relay 48, and the ON/OFF switching of the first switching element 43 and the second switching element 44 may be controlled by the control device.

The vehicle power supply device 1 further includes at least one diode 11 on the output side of the PCU 40 (the PCS side shown in FIG. 1). Of the multiple PCUs 40, the output terminal of the PCU 40 of power supply unit 1A is connected to the first positive power line 12 via a diode 11 connected to the other end of the reactor 42. The output terminals of the PCUs 40 of the other power supply units 1B, ..., 1N are open.

2. Operational Example of Vehicle Power Supply Device FIGS. 2 and 3 are diagrams illustrating an operational example of the vehicle power supply device 1 according to the embodiment. FIG. 2 illustrates the first half of the operational example of the vehicle power supply device 1, and FIG. 3 illustrates the second half of the operational example of the vehicle power supply device 1. In STEP 1 shown in FIG. 2, the first relay 30 in power supply unit 1A of the multiple power supply units 1A, 1B, ..., 1N is switched ON. In this state, STEP 1 shown in FIG. 2 illustrates the voltage states when energy is stored in each second capacitor 45 and first capacitor 10. The voltages charged to the second capacitors 45 (voltages V1, V2, ..., Vn shown in FIG. 2) correspond to the voltages of the power storage devices 20 corresponding to each PCU 40. At this point, the voltage Vp of the first capacitor 10 remains at 0 V.

Next, in STEP 2 shown in FIG. 2, the multi-phase inverter 47 in power supply unit 1A boosts the voltage of the second capacitor 45 included in the PCU 40 of power supply unit 1A to a predetermined voltage. In the example of STEP 2 shown in FIG. 2, only the voltage V1 of the second capacitor 45 included in power supply unit 1A is boosted, while the voltages V2, ..., Vn of the second capacitors 45 of the other power supply units 1B, ..., 1N are maintained at the voltage state in STEP 1. Note that even at this point, the voltage Vp of the first capacitor 10 remains at 0 V.

In STEP 3 shown in Figure 3, the second relays 48 of the power supply units 1B, ..., 1N other than power supply unit 1A are switched ON. Furthermore, the first switching element 43 of the boost converter 41 in power supply unit 1A is repeatedly switched ON and OFF alternately. In this state, STEP 3 shown in Figure 3 shows the voltage state when energy is stored in each second capacitor 45 and first capacitor 10.

More specifically, the voltage V1 of the second capacitor 45 is connected to the voltage Vp of the first capacitor 10 and the voltages V2, ..., Vn of the second capacitors 45 via the diode 11. At this time, the voltage V1 of the second capacitor 45 is maintained at the voltage boosted in STEP 2 by the multi-phase inverter 47 and the boost converter 41. The voltages V2, ..., Vn of the second capacitors 45 are also transitioned to the same voltage as voltage V1. Furthermore, the voltage Vp of the first capacitor 10 is also transitioned to the same voltage as voltage V1. This makes it possible to make the voltages of all the second capacitors 45 and the first capacitors 10 the same voltage.

Next, in STEP 4 shown in Figure 3, the first switching element 43 of the boost converter 41 in the power supply unit 1A is switched OFF, and the boost operation of the multi-phase inverter 47 in the power supply unit 1A is stopped. Furthermore, the second relay 48 included in the power supply unit 1A is switched ON. In this state, STEP 4 shown in Figure 3 shows the voltage state when energy is stored in each of the second capacitors 45 and the first capacitor 10.

More specifically, in STEP 3, the voltage Vp of the first capacitor 10 and the voltages V2, ..., Vn of the second capacitor 45 were each in a charged state due to the voltage V1 of the second capacitor 45. However, in STEP 4, these voltages are discharged, causing all voltages to become slightly lower than the voltage states in STEP 3, and then all voltages are maintained at the same voltage state. This state is known as the completion state of power supply startup. For example, when the control device determines that the power supply has started normally, the vehicle power supply device 1 switches from startup mode to operating mode.

As described above, with the vehicle power supply device 1 according to this embodiment, steps 1 to 4 shown in FIGS. 2 and 3 are performed when the power supply is started. This equalizes the voltages of multiple PCUs 40, preventing the occurrence of inrush currents. Note that steps 1 to 4 described above may also be performed based on commands from a control device.

Other Embodiments In the vehicle power supply device 1 according to the embodiment, the first capacitor 10 is included in the vehicle power supply device 1, but the first capacitor 10 does not have to be included in the configuration of the vehicle power supply device 1. For example, the first capacitor 10 may be included in an external device (e.g., PCS). This provides the same effects as the vehicle power supply device 1 according to the above-described embodiment.

1...vehicle power supply device, 10...first capacitor, 11...diode, 12...first positive power line, 13...first negative power line, 14...second positive power line, 15...second negative power line, 20...electrical storage device, 30...first relay, 40...PCU, 41...boost converter, 42...reactor, 43...first switching element, 44...second switching element, 45...second capacitor, 46...discharge resistor, 47...multi-phase inverter, 48...second relay, 49...third capacitor

Claims (1)

A vehicle power supply device having a control device,
A first capacitor;
a plurality of PCUs connected in parallel to the first capacitor;
a plurality of power storage devices provided on the input sides of the plurality of PCUs;
a first relay provided between each PCU and each power storage device and controlled to be opened and closed by the control device;
Equipped with
an output terminal of each of the plurality of PCUs is connected to a first positive power line connected to one end of the first capacitor and a first negative power line connected to the other end of the first capacitor;
Each of the plurality of PCUs
a boost converter;
a multi-phase inverter controlled by the control device ;
a second positive power line and a second negative power line connecting the boost converter and the multi-phase inverter;
a second capacitor and a discharge resistor connected in parallel between the second positive power line and the second negative power line;
a second relay connected to the second positive power line and the second negative power line, and connected to the first positive power line and the first negative power line, respectively , and controlled to be opened and closed by the control device ;
Including,
The boost converter is
a first switching element having one end connected to the second positive power line and controlled to be opened or closed by the control device ;
a second switching element having one end connected to the other end of the first switching element and the other end connected to the second negative power line;
a reactor having one end connected between the first switching element and the second switching element and the other end open;
Including,
an output terminal of at least one PCU among the plurality of PCUs is connected to the first positive power line via a diode connected to the other end of the reactor ;
The control device, when power is turned on,
closing the first relay so that the voltage of the second capacitor is charged to the voltage of the power storage device;
controlling the multi-phase inverter provided in the at least one PCU so that the voltage of the second capacitor is boosted to a predetermined voltage;
and closing the second relay while opening and closing the first switching element of the boost converter provided in the at least one PCU so that the voltages of the first capacitor and the second capacitor become the same voltage.
A vehicle power supply device characterized by: