JP7320781B2 - power conversion system - Google Patents

Description

The present invention relates to power conversion systems.

2. Description of the Related Art Conventionally, a power conversion system capable of exchanging power with a plurality of batteries that are configured to switch between series connection and parallel connection is known.

For example, a battery system for industrial machinery disclosed in Patent Document 1 aims to enable rapid charging under high voltage and to enable the use of low-voltage components. This system comprises charging/discharging switching means for selectively switching a connection state between a battery unit and a charging input section or a power load, and an electrical connection between a plurality of battery units that can be selectively connected in parallel or in series. Parallel/serial switching means or the like for switching to .

In the discharge control flow of this system, a plurality of battery units are connected in parallel and discharged to a power load. In the charging control flow, the plurality of battery units are charged from the quick charger through the charging input section while the plurality of battery units are connected in series. After charging is completed, if the voltage difference between the plurality of battery units is equal to or greater than the threshold, the battery unit balancing process is performed to eliminate the voltage difference.

Japanese Patent No. 5611400

In the inter-battery unit balancing process of Patent Literature 1, current flows between the two battery units through a path provided with resistance, so loss due to resistance occurs. In addition, it takes time to achieve balance because the current is suppressed by the resistance. In the system of Patent Literature 1, after the completion of the inter-battery unit balancing process, the system is in a standby state, and it is presumed that the time required for balancing is not an issue.

Hereinafter, the term "battery" in this specification means a battery module including one or more storage cells, like the "battery unit" of Patent Document 1. By "batteries" is meant battery modules rather than storage cells. When the technology of Patent Document 1 is applied to external charging of an electric vehicle or a plug-in hybrid vehicle, after charging in series is completed, switching means such as a relay is operated to switch a plurality of batteries to parallel connection, and the main engine, which is a load, is switched. A situation is assumed in which the electric current is discharged to the motor for running. If a switch is made to parallel connection while the voltage difference between a plurality of batteries is still large, there is a risk that the service life of relays and the like will be shortened due to rush current.

Therefore, in order to improve the reliability and life of relays and the like, it is conceivable to perform a process of equalizing the voltage differences of a plurality of batteries to a predetermined value or less before switching to parallel connection. Hereinafter, in this specification, "equalizing the battery voltages" does not mean that the battery voltages are strictly matched, but that the voltage difference between the plurality of batteries is equal to or less than a predetermined value at which the influence of inrush current or the like does not pose a problem. means to reduce to Furthermore, in equalizing the battery voltage, it is required to improve the efficiency.

The present invention was created in view of the above problems, and its object is to provide a power conversion system that equalizes the voltages of a plurality of batteries when switching from series connection to parallel connection of a plurality of batteries. That's what it is.

The present invention is provided between an external power supply (150) capable of outputting electric power and a plurality of batteries (BT1, BT2) configured to be capable of switching between series connection and parallel connection. It is a power conversion system that can bi-directionally exchange power between The power conversion system comprises a multi-port isolated converter (300, 301, 302), a plurality of regulated converters (61-64) and a drive circuit (75).

One multi-port isolated converter is connected to an external power supply, or a plurality of multi-port isolated converters corresponding to a plurality of batteries are connected in parallel. Each multiport isolation converter has transformers (200, 201, 202), one primary side switching circuit (31, 32), and a plurality of secondary side switching circuits (41-44).

The transformer has one primary winding (211, 212) connected to primary ports (P11, P12) on the external power supply side and a plurality of secondary windings (211, 212) connected to a plurality of secondary ports (P21-P24) on the battery side. It has windings (221-224). A primary side switching circuit is provided between the primary port and the primary winding. A plurality of secondary side switching circuits are provided between the plurality of secondary ports and the plurality of secondary windings.

A regulating converter is connected between a regulating port, which is a portion of the plurality of secondary ports corresponding to each battery, and the battery, and is capable of regulating the voltage on the battery side. A drive circuit drives the multi-port isolated converter and the regulated converter and controls the operation of the regulated converter to regulate the voltage on the battery side. Before switching the plurality of batteries to parallel connection, the drive circuit drives the multiport isolation converter and the adjustment converter to transfer power so that the voltage difference between the plurality of batteries is equal to or less than a predetermined value.

The power conversion system of the present invention drives the multiport isolated converter and the regulating converter to transfer power between the batteries and equalize the voltages of the batteries before switching the batteries to parallel connection. As a result, it is possible to suppress the rush current or the like at the time of switching to the parallel connection, and improve the reliability and life of the relay and the like. Further, in the multi-port isolated converter, some of the plurality of secondary ports corresponding to each battery are adjustment ports, and non-adjustment ports are provided in addition to the adjustment ports. Therefore, the range of output adjustment by the adjustment converter can be narrowed by the amount shared by the non-adjustment side port with respect to the maximum battery voltage. Therefore, the withstand voltage level of the switching element of the adjustment converter can be lowered.

Furthermore, in a power conversion system that does not have a regulating converter between the secondary port and the battery, the drive circuit variably controls the duty ratio of the multiport isolated converter to equalize the voltages of multiple batteries. You need to adjust the output voltage so that Therefore, the efficiency may decrease depending on the range of duty ratios to be operated. On the other hand, in the present invention, by adjusting the output voltage of the adjustment converter according to the voltage change of the battery, the duty ratio of the multi-port isolated converter can be fixed to a value in the high efficiency region and can be driven without control. .

1 is an overall system configuration diagram of a vehicle equipped with a power conversion system according to each embodiment; FIG. The figure which shows the relationship between a charge infrastructure and a load drive voltage. FIG. 5 is a diagram for explaining a problem at the time of switching from series connection to parallel connection; The schematic diagram of the power conversion system of a comparative example. 1 is a schematic diagram of a power conversion system according to a first embodiment; FIG. FIG. 4 is a diagram showing open/closed states of relays in series connection and parallel connection; (a) Two-way power transfer by a converter, (b) Diagrams for explaining the action of power transfer between batteries. FIG. 4 is a diagram showing a specific configuration example of an external power supply, a multiport isolation converter, and a regulation converter in the power conversion system according to the first embodiment; FIG. 4 is a diagram for explaining voltage distribution of a secondary port in a configuration using a step-down converter as a regulating converter; (a) SOC-battery voltage characteristic diagram corresponding to FIG. 9, (b) SOC-battery voltage characteristic diagram for explaining the equalization action of the battery voltage. The schematic diagram of the power conversion system by 2nd Embodiment. The schematic diagram of the power conversion system by the modification of 2nd Embodiment. The schematic diagram of the power conversion system by 3rd Embodiment. The schematic diagram of the power conversion system by 4th Embodiment. The schematic diagram of the power conversion system by 5th Embodiment. FIG. 11 is a schematic diagram of a power conversion system according to a sixth embodiment, and is a diagram for explaining voltage distribution of a secondary port in a configuration using a boost converter as a regulation converter; FIG. 17 is an SOC-battery voltage characteristic diagram corresponding to FIG. 16; The schematic diagram of the power conversion system by 7th Embodiment. The block diagram of the power conversion system of a reference form. Schematic diagram of a power conversion system according to another embodiment. Schematic diagram of a power conversion system according to another embodiment. Schematic diagram of a power conversion system according to another embodiment.

A plurality of embodiments of the power conversion system will be described below with reference to the drawings. The same reference numerals are assigned to substantially the same configurations in multiple embodiments, and the description thereof is omitted. The first to seventh embodiments are collectively referred to as "this embodiment". The power conversion system of the present embodiment is provided between an external power supply capable of outputting electric power and a plurality of batteries configured to switch between series connection and parallel connection, and between the external power supply and the plurality of batteries It is a system that can transmit and receive power bi-directionally. In the present embodiment, an example applied to an overall system including two batteries BT1 and BT2 as "a plurality of batteries" will be described.

[Overall system configuration and background]
First, with reference to FIGS. 1 to 4, the overall system configuration of a vehicle equipped with the power conversion system of each embodiment and the background of this embodiment will be described. FIG. 1 shows a state in which a power supply cable 13 is connected from an external charger 10 to a charging port 14 of a vehicle stopped at a power supply facility such as a charging station. A "vehicle" in this specification means an electric vehicle or a plug-in hybrid vehicle, and is an example of a "moving object" using a battery as a power source. Two batteries BT1 and BT2, series-parallel switching relays RY1-RY3, other path switching relays RY4-RY7, a power conversion system 70, and the like are provided inside the vehicle.

The first battery BT1 and the second battery BT2 are chargeable/dischargeable high voltage battery modules, such as lithium ion batteries, of, for example, 400 V, and function as main batteries that are power sources of the vehicle. Hereinafter, "battery module" will be abbreviated as "battery". The auxiliary battery BTa used in the third embodiment is a low-voltage battery different from the main battery. Batteries BT1 and BT2 are provided between charging port 14 and load 80 . The load 80 includes inverters, motors, DC/DC converters, air conditioners, etc. that are generally used in electric vehicles and plug-in hybrid vehicles.

Among the series-parallel switching relays, the first relay RY1 is provided between the positive electrodes of the first battery BT1 and the second battery BT2. The second relay RY2 is provided between the negative electrode of the first battery BT1 and the positive electrode of the second battery BT2. The third relay RY3 is provided between the negative electrodes of the first battery BT1 and the second battery BT2.

Other load relays RY4 and RY5 open and close paths between the positive and negative electrodes of the second battery BT2 and the load 80, respectively. Charging port relay RY6 opens and closes a path between the positive electrode of first battery BT1 and positive electrode terminal 141 of charging port 14 . Charging port relay RY7 opens and closes the path between the negative electrode of second battery BT2 and negative electrode terminal 142 of charging port 14 .

Here, the significance of switching the connection state of the two batteries BT1 and BT2 between series and parallel will be described. FIG. 2 shows the relationship between the charging infrastructure for a vehicle battery and the load driving voltage. Assume that the battery voltage is typically in the 400V class. In addition, it is assumed that there are two types of charging infrastructure such as charging stations, one compatible with the 400V class and the other compatible with the 800V class, and there are two types of loads used, one driven by the 400V class and the other driven by the 800V class. do. There is no problem in charging a battery of a vehicle driving a 400V class load with a 400V class charging infrastructure, or charging a battery of a vehicle driving a 800V class load with an 800V class charging infrastructure.

On the other hand, consider the case where the vehicle battery is charged by a charging infrastructure with a voltage different from the load driving voltage. Then, if two batteries for driving a 400V class load are connected in series during charging, charging can be performed with an 800V class charging infrastructure. When driving a load, that is, when discharging, it can be switched to parallel connection and used in the 400V class. Conversely, if the batteries charged by the 400V class charging infrastructure in the parallel connection state are switched to the dual series connection when driving the load, they can be used in the 800V class. By making it possible to switch the connection state of a plurality of batteries between series and parallel in this way, it is possible to support many charging infrastructures.

Specifically, vehicle equipment such as main motors and auxiliary equipment of electric vehicles and plug-in hybrid vehicles and charging infrastructure are expected to shift from the current 400V class to the 800V class in the future in order to shorten the charging time. Then, especially in the transitional period, a situation may arise in which vehicle specifications and charging infrastructure specifications do not match. Therefore, it is required to be able to switch the series/parallel connection of the battery between when charging and when driving the load (during running in the case of driving the main motor). Therefore, a series-parallel switching relay is required.

Against this background, when using the 800V class external charger 10, series charging is performed with the first battery BT1 and the second battery BT2 connected in series. On the other hand, when using the 400V class external charger 10, parallel charging is performed with the first battery BT1 and the second battery BT2 connected in parallel.

In the following description of the relay opening/closing pattern, when "a certain relay among RY1 to RY7 is ON", it is assumed that "the other relays are OFF". During two-series charging, the second relay RY2 and charging port relays RY6 and RY7 are turned on. During two-parallel charging, the first relay RY1, the third relay RY3, and the charging port relays RY6 and RY7 are turned on. At the time of two parallel discharges in which 400V power is supplied from the parallel-connected batteries BT1 and BT2 to the load 80, the first relay RY1, the third relay RY3, and the load relays RY4 and RY5 are turned on. As indicated by the short dashed arrows in FIG. 1, the opening and closing of each of the relays RY1-RY7 is operated by the relay operating section 77. As shown in FIG.

By the way, as shown in FIG. 3, when switching from series connection to parallel connection, it is assumed that a voltage difference occurs between the first battery BT1 and the second battery BT2 due to variations in internal resistance and the like. Suppose. Assume that the voltage of the first battery BT1 and the second battery BT2 is 100% when the first battery BT1 and the second battery BT2 are connected in series, for example, the voltage of the first battery BT1 is 52% and the voltage of the second battery BT2 is 48%. It should be noted that the thick line arrow means that the voltage is higher than the thin line arrow. Then, when the relay is turned on to switch to parallel connection after series charging with an external charger, an inrush current flows due to the voltage difference between the first battery BT1 and the second battery BT2, and an arc is generated at the relay contact. .

In the prior art disclosed in Patent Document 1 (Japanese Patent No. 5611400), a current flows between two battery units through a path provided with a resistor, so loss due to resistance occurs. In addition, there is a problem that it takes time to achieve balance because the current is suppressed by the resistor. Therefore, it is required to equalize the voltages of the two batteries BT1 and BT2 in a short period of time while avoiding loss and shortening of contact life. In this specification, "equalizing the battery voltages" means reducing the voltage difference between the batteries BT1 and BT2 to a predetermined value or less at which the influence of inrush current or the like does not pose a problem.

Therefore, a configuration in which the first battery BT1 and the second battery BT2 are connected to the power conversion system 70 is assumed. The power conversion system 70 can bidirectionally exchange power between an external power supply 150 capable of outputting power and the batteries BT1 and BT2 configured to be capable of switching between series connection and parallel connection. The external power supply 150 converts the AC power of the AC power supply 15 by the AC/DC conversion circuit 19, for example, and outputs the DC power. The power conversion system 70 may also serve as a DC/DC converter such as an on-vehicle charger.

The power conversion system 70 detects the battery voltage Vb1 of the first battery BT1 and the battery voltage Vb2 of the second battery BT2, respectively, and monitors whether the voltage difference between the batteries BT1 and BT2 is equal to or less than a predetermined value. Then, if the voltage difference exceeds a predetermined value before the batteries BT1 and BT2 are connected in parallel, the power conversion system 70 transfers power between the batteries BT1 and BT2. That is, the power conversion system 70 lowers or raises the voltages Vb1 and Vb2 of the batteries BT1 and BT2 to reduce the voltage difference between the batteries BT1 and BT2 to a predetermined value or less.

Then, when the voltage difference is equal to or less than a predetermined value, the relay operation unit 77 turns on the first relay RY1 and the third relay RY3 for parallel connection. By turning on the contacts of the first relay RY1 and the third relay RY3 for parallel connection in this way without causing an excessive rush current, the occurrence of arcs can be prevented, and the reliability and life of the relays can be improved. can be done.

[Embodiment of power conversion system]
Next, a specific configuration of the power conversion system 70 will be described for each embodiment. The code|symbol of the power conversion system of each embodiment attaches the number of embodiment to the 3rd digit following "70." Before proceeding to the description of each embodiment, a power conversion system 709 of a comparative example will be described with reference to FIG. In the power conversion system 709 of the comparative example, substantially the same configurations as those of the power conversion system 701 of the first embodiment shown in FIG. The comparative example corresponds to the configuration disclosed in FIG. 11 of JP-A-2019-80473.

(Comparative example)
The transformer 209 that constitutes the multiport isolated converter 309 in the power conversion system 709 of the comparative example includes one primary winding 211 connected to the primary port P11 and two windings connected to the two secondary ports P21 and P23. Two secondary windings 221 , 223 are wound on core 239 . A primary side switching circuit 31 is provided between the primary port P11 and the primary winding 211 . Secondary side switching circuits 41 and 43 are provided between the two secondary ports P21 and P23 and the two secondary windings 221 and 223, respectively. The switching circuits 31 , 41 , 43 periodically alternate the direction of current flowing through the windings 211 , 221 , 223 . The secondary port P21 is connected to the first battery BT1 and the secondary port P23 is connected to the second battery BT2.

Before the relay operation unit 77 switches the two batteries BT1 and BT2 to parallel connection, the drive circuit 75 drives the multiport isolation converter 309 to transfer power between the batteries BT1 and BT2. That is, as indicated by thick arrows in FIG. 4, power is circulated between the batteries BT1 and BT2 along a path from one of the secondary side switching circuits 41 to the other secondary side switching circuit 43 .

At this time, the drive circuit 75 variably controls the duty ratios of the switching circuits 31, 41, and 43 in accordance with voltage changes of the batteries BT1 and BT2. Note that the duty ratio is a value that defines the ON/OFF time ratio of a plurality of switching elements forming each switching circuit. In this specification, "the ratio of the ON time of the upper arm switching element to the switching period" is defined as the duty ratio.

By the way, the efficiency of the multiport isolation converter 309 depends on the duty ratios of the switching circuits 31 , 41 and 43 . Basically, the efficiency is maximum when the duty ratio is around 0.5, and the efficiency decreases when the duty ratio is away from 0.5. Therefore, in a configuration in which the duty ratio is variably controlled, the efficiency may decrease depending on the range of the duty ratio to be operated. Therefore, in equalizing the voltages of the batteries BT1 and BT2 in this embodiment, it is required to further improve the efficiency.

(First embodiment)
A power conversion system 701 of the first embodiment will be described with reference to FIGS. 5 to 10. FIG. As schematically shown in FIG. 5, a power conversion system 701 is provided between an external power supply 150 capable of outputting power and two batteries BT1 and BT2. The first battery BT1 and the second battery BT2 are configured to be switchable between series connection and parallel connection by series-parallel switching relays RY1-RY3. Specifically, as shown in FIG. 6, during the series connection, the second relay RY2 is ON, and the first relay RY1 and the third relay RY3 are OFF. During parallel connection, the first relay RY1 and the third relay RY3 are turned ON, and the second relay RY2 is turned OFF.

The power conversion system 701 and the batteries BT1 and BT2 are mounted on a "mobile body" such as a vehicle, and the batteries BT1 and BT2 are used as power sources for the mobile body. The external power source 150 is envisioned as at least the power source itself being external to the vehicle. However, part of the circuit that converts the power of the external power supply 150 may be provided inside the mobile object.

The power conversion system 701 includes a multiport isolated converter 300 , two battery charge/discharge circuits 601 and 602 corresponding to the batteries BT1 and BT2, and a drive circuit 75. FIG. In FIG. 5, the description of the name “battery charging/discharging circuit” is omitted for the second battery charging/discharging circuit 602 . The same applies to the drawings of the second to fourth embodiments.

Two series-connected battery-side capacitors Cb1 and Cb2 are connected in parallel to the first battery BT1. High-potential-side battery-side capacitor Cb1 is directly connected to secondary port P21 of multi-port isolated converter 300 . Low-potential-side battery-side capacitor Cb2 is connected to secondary port P22 of multi-port isolation converter 300 via regulation converter 62 . The first battery charging/discharging circuit 601 is composed of these high potential side and low potential side circuits.

Similarly, two series-connected battery-side capacitors Cb3 and Cb4 are connected in parallel to the second battery BT2. High-potential-side battery-side capacitor Cb3 is directly connected to secondary port P23 of multi-port isolated converter 300 . Low-potential-side battery-side capacitor Cb4 is connected to secondary port P24 of multi-port isolated converter 300 via regulation converter 64. FIG. The second battery charging/discharging circuit 602 is composed of these high potential side and low potential side circuits.

Here, "directly connected" in the high-potential side circuits of the battery charging/discharging circuits 601 and 602 means "connected without an adjustment converter". It does not exclude the provision of such elements. In short, the circuits on the low potential side of the battery charging/discharging circuits 601 and 602 are adjusting circuits that adjust the voltage on the battery side by the adjusting converters 62 and 64, whereas the circuits on the high potential side do not adjust the voltage on the battery side. It is an "unregulated circuit".

Further, in the first embodiment, adjustment converters 62 and 64 are provided on the low potential side, but adjustment converters 61 and 63 may be provided on the high potential side as in a fourth embodiment described later. However, since the low potential side (that is, the ground side) is less susceptible to noise and is advantageous, the configuration in which the adjustment converters 62 and 64 are provided on the low potential side is the basic configuration except for the fourth embodiment. Specific configurations and operational effects of the adjustment converters 62 and 64 will be described later.

In the first embodiment, one multiport isolated converter 300 commonly corresponding to the two batteries BT1 and BT2 is connected to the external power supply 150 . The multiport isolated converter 300 has a total of five input/output ports, one on the external power supply 150 side and four on the battery BT1 and BT2 sides.

Transformer 200 constituting multiport isolated converter 300 has one primary winding 211 connected to primary port P11 and four secondary windings connected to four secondary ports P21, P22, P23, and P24. Wires 221 , 222 , 223 , 224 are wound on core 230 . A primary side switching circuit 31 is provided between the primary port P11 and the primary winding 211 . Secondary side switching circuits 41, 42, 43 and 44 are provided between the four secondary ports P21, P22, P23 and P24 and the four secondary windings 221, 222, 223 and 224, respectively. The switching circuits 31 , 41 , 42 , 43 , 44 periodically alternate the direction of current flow through the windings 211 , 221 , 222 , 223 , 224 .

A part of the secondary ports P21 and P22 of the two secondary ports P21 and P22 corresponding to the first battery BT1 corresponds to the "adjustment side port", and the secondary port P21 other than the adjustment side port P22 corresponds to the "non-adjustment side port". Equivalent to "Port". A part of the secondary ports P24 of the two secondary ports P23 and P24 corresponding to the second battery BT2 corresponds to the "adjustment side port", and the secondary port P23 other than the adjustment side port P24 corresponds to the "non-adjustment side port". Equivalent to "Port".

Drive circuit 75 drives multiport isolation converter 300 and adjustment converters 62 and 64, and controls the operation of adjustment converters 62 and 64 to adjust the voltages of batteries BT1 and BT2. Specifically, before relay operation unit 77 switches two batteries BT1 and BT2 to parallel connection, drive circuit 75 controls multiport isolated converter 300 and Power transfer is performed by driving the adjustment converters 62 and 64 .

In the present embodiment, when driving the multiport isolated converter 300 by the drive circuit 75, the duty ratios of the primary side switching circuit 31 and the secondary side switching circuits 41 to 44 are set to fixed values. As described above, the duty ratio is a value that defines the ON/OFF time ratio of a plurality of switching elements forming each switching circuit. In this specification, a converter that is driven with a fixed duty ratio of the switching circuit is referred to as an "uncontrolled converter".

As shown in FIG. 8 and the like, a switching circuit is generally configured including switching elements for upper and lower arms. Basically, the efficiency of the multiport isolated converter 300 is maximized when the duty ratio is 0.5. Therefore, the fixed value of the duty ratio is preferably set to approximately 0.5. Strictly speaking, a dead time is subtracted to prevent short-circuit current from flowing when the switching elements of the upper and lower arms are turned on at the same time.

In the power conversion system 709 of the comparative example shown in FIG. 4, the secondary ports P21, P23 of the multiport isolated converter 309 and the respective batteries BT1, BT2 are connected only by "non-regulating circuits". That is, since the power conversion system 709 of the comparative example does not include an adjustment converter, the drive circuit 75 variably controls the duty ratio of the multiport isolated converter 309 to equalize the voltages of the two batteries BT1 and BT2. output voltage should be adjusted to Therefore, the efficiency may decrease depending on the range of duty ratios to be operated.

In contrast, in the present embodiment, the output voltages of the adjustment converters 62 and 64 are adjusted according to the voltage changes of the batteries BT1 and BT2, thereby fixing the duty ratio of the multiport isolated converter 300 to a value in the high efficiency region. Can be driven uncontrolled. As described above, the power conversion system 701 of the first embodiment bidirectionally transfers power between the external power supply 150 and the two batteries BT1 and BT2 via the multiport isolated converter 300 and the battery charge/discharge circuits 601 and 602. It is possible to give and receive.

The power exchange action in the power conversion system 701 will be described with reference to FIGS. In FIGS. 7A and 7B, illustration of the series/parallel switching relays RY1 to RY3 and the driving circuit 75 is omitted. As shown in FIG. 7( a ), the power conversion system 701 is capable of bi-directional power exchange in each switching circuit of the multiport isolation converter 300 and the adjustment converters 62 and 64 . In addition, as shown in FIG. 7B, the power conversion system 701 transfers power between the batteries BT1 and BT2 via the multiport insulated converter 300 and the battery charge/discharge circuits 601 and 602, so that the battery voltage Vb1 and Vb2 can be equalized.

Next, FIG. 8 shows a specific configuration example of the external power supply 150, the multiport isolation converter 300, and the adjustment converter 62. As shown in FIG. 8 and subsequent drawings of specific configuration examples, only the upper half portion of FIG. 5 etc. corresponding to the first battery BT1 is shown, and the lower half portion of FIG. 5 etc. corresponding to the second battery BT2 is omitted. Also, illustration of the series-parallel switching relays RY1 to RY3 and the drive circuit 75 is omitted.

The external power supply 150 in the example of FIG. 8 is composed of the AC power supply 15 and the AC/DC conversion circuit 19 . The AC power supply 15 is a commercial power supply of 50 Hz or 60 Hz supplied from a 100V or 200V outlet. The AC/DC conversion circuit 19 is configured as, for example, a PFC (power factor correction) circuit, and may be provided on the side of a moving body such as a vehicle. Another example of the external power source 150 may be a DC power source such as a charger.

In the multiport isolated converter 300 in the example of FIG. 8, the primary side switching circuit 31 is composed of a half-bridge type DC/DC converter 51 . Further, the secondary side switching circuits 41 and 42 are composed of full-bridge DC/DC converters (no reference numerals).

Further, the regulating converter 62 of the first embodiment is composed of a step-down converter 67 functioning as a step-down circuit when charging the battery BT1 from the multi-port isolated converter 300. FIG. The step-down converter 67 is a chopper-type step-down circuit including switching elements 67a and 67b on upper and lower arms and a coil 67c. During charging of the battery BT1, the step-down converter 67 steps down the input voltage VH of the adjustment side port P22 and outputs it to the battery BT1 side.

A change in the battery voltage according to the SOC of the battery and adjustment of the battery side voltage by the step-down converter 67 will be described with reference to FIGS. 9 and 10. FIG. FIG. 9 shows the first battery BT1 as a representative, but the description is common to both batteries BT1 and BT2, so the battery voltage is simply denoted as "Vb". Further, as shown in FIG. 10, the voltage when the battery SOC is 0% is denoted as "minimum battery voltage Vmin", and the voltage when the battery SOC is 100% is denoted as "maximum battery voltage Vmax". The range from the battery maximum voltage Vmax to the battery minimum voltage Vmin is the voltage adjustment range of the step-down converter 67 .

FIG. 9 shows voltage distribution between the non-adjustment side port P21 and the adjustment side port P22 in the battery charging/discharging circuit 601. As shown in FIG. The voltage of the non-adjusted port P21 is set to the battery minimum voltage Vmin of the corresponding battery. However, in reality, in consideration of voltage detection errors, output errors of the multiport isolated converter 300, etc., the voltage of the non-adjusted port P21 is set to "a value equivalent to the minimum battery voltage Vmin" of the corresponding battery. be done. The range of "equivalent" may be determined in light of common technical knowledge in the relevant technical field.

Further, the voltage of adjustment side port P22 is set to the difference value (Vmax-Vmin) between the battery maximum voltage Vmax and the battery minimum voltage Vmin of the corresponding battery, and this value becomes input voltage VH of step-down converter 67. FIG. The step-down voltage VL output from the step-down converter 67 is the difference (Vb−Vmin) between the battery voltage Vb and the battery minimum voltage Vmin. This relationship is shown in FIG. 10(a).

FIG. 10(b) shows the effect of equalizing the voltages Vb1 and Vb2 of the two batteries BT1 and BT2. For example, when the first battery voltage Vb1 is higher than the second battery voltage Vb2, the drive circuit 75 drives the multiport isolated converter 300 and the regulation converter 62 to supply power from the first battery BT1 to the second battery BT2. As a result, the first battery voltage Vb1 is lowered, the second battery voltage Vb2 is raised, and the difference between the battery voltages Vb1 and Vb2 is equalized to a predetermined value or less.

As described above, the power conversion system 701 of the first embodiment drives the multi-port isolated converter 300 and the adjustment converters 62 and 64 before switching the two batteries BT1 and BT2 to the parallel connection. Electric power is exchanged between them to equalize the battery voltages Vb1 and Vb2. As a result, it is possible to suppress inrush current or the like at the time of switching to parallel connection, and improve the reliability and life of the relay.

In multiport isolated converter 300, some of the plurality of secondary ports corresponding to batteries BT1 and BT2 are adjustment side ports P22 and P24. is provided. Therefore, the range of output adjustment by the adjustment converters 62 and 64 can be narrowed by the amount shared by the non-adjustment side port with respect to the maximum battery voltage Vmax. Therefore, the withstand voltage level of the switching elements of adjustment converters 62 and 64 can be lowered.

Furthermore, in driving the multiport isolated converter 300 by the drive circuit 75, by setting the duty ratio of each switching circuit to about 0.5 as a fixed value, the efficiency in equalizing the battery voltage can be improved.

In addition, in the configuration using the step-down converter 67 for the adjustment converters 62 and 64, by setting the voltages of the non-adjustment side port P21 and the adjustment side port P22 as shown in FIG. Output adjustment by the step-down converter 67 can be efficiently performed.

(Second embodiment)
Next, with reference to FIG. 11, a power conversion system 702 according to the second embodiment will be described. In the second embodiment, two multiport isolated converters 301 and 302 corresponding to two batteries BT1 and BT2 are connected in parallel to an external power supply 150. FIG. Each of the multiport isolated converters 301 and 302 has a total of three input/output ports, one on the external power supply 150 side and two on the battery BT1 and BT2 side.

The transformer 201 constituting the first multiport isolated converter 301 has one primary winding 211 connected to the primary port P11 and two secondary windings 221 connected to two secondary ports P21 and P22. , 222 are wound on the core 231 . A primary side switching circuit 31 is provided between the primary port P11 and the primary winding 211 . Secondary side switching circuits 41 and 42 are provided between the two secondary ports P21 and P22 and the two secondary windings 221 and 222, respectively. The switching circuits 31 , 41 , 42 periodically alternate the direction of the current flowing through the windings 211 , 221 , 222 .

The transformer 202 constituting the second multiport isolated converter 302 has one primary winding 212 connected to the primary port P12 and two secondary windings 223 connected to two secondary ports P23 and P24. , 224 are wound on the core 232 . A primary side switching circuit 32 is provided between the primary port P12 and the primary winding 212 . Secondary side switching circuits 43 and 44 are provided between the two secondary ports P23 and P24 and the two secondary windings 223 and 224, respectively. Switching circuits 32 , 43 , 44 periodically alternate the direction of current flow through windings 212 , 223 , 224 .

The configuration in which the secondary ports P21 and P23 of the respective multiport isolated converters 301 and 302 are non-adjustment side ports and the secondary ports P22 and P24 are adjustment side ports, and the configuration of the battery charge/discharge circuits 601 and 602 are the first embodiment. Similar to morphology. A drive circuit 75 drives the multiport isolated converters 301, 302 and the regulating converters 62, 64. FIG.

The duty ratio of each multiport isolated converter 301, 302 is fixed at 0.5. In the second embodiment, the drive circuit 75 drives the multiport isolated converters 301, 302 and the adjustment converters 62, 64 to equalize the voltages of the two batteries BT1, BT2 as in the first embodiment. .

A modification of the second embodiment is shown in FIG. In the configuration in which the external power supply 150 includes the AC power supply 15 and the AC/DC conversion circuit, two AC/DC conversion circuits 191 and 192 are connected in parallel to the AC power supply 15 in a modification. The AC/DC conversion circuits 191 and 192 are connected to the primary port P11 of the first multiport isolation converter 301 and the primary port P12 of the second multiport isolation converter 302, respectively.

(Third embodiment)
13 differs from the power conversion system 701 of the first embodiment shown in FIG. 5 in that the fifth secondary winding 228 , a secondary side switching circuit 48, and a secondary port P28 are further provided. The auxiliary battery BTa and the auxiliary load 49 are connected to the secondary port P28. 13, illustration of the drive circuit 75 and its input/output in FIG. 5 is omitted. Reference numerals used only in FIG. 13 of the third embodiment are not described as reference numerals in the column of [Description of Codes] and claims.

Similarly, in the power conversion system 702 of the second embodiment, the auxiliary battery BTa or the auxiliary load 49 is connected to the secondary port of one of the two multiport isolated converters 301 and 302. It is good also as a structure.

When the power conversion system 703 is installed in a vehicle as a "moving body", the auxiliary battery BTa is a low-voltage battery different from the main batteries BT1 and BT2, and the auxiliary load 49 performs functions other than running of the vehicle. Equivalent to various in-vehicle equipment. In the third embodiment, the multiport isolated converter 300 also functions as a DC/DC converter for power supply to the auxiliary battery BTa and the auxiliary load 49 . Note that the “moving body” on which the power conversion system 703 is mounted is not limited to a vehicle driven by a driver, and may be an unmanned vehicle, a ship, an airplane, or the like powered by a battery. In that case, the accessory load 49 is responsible for various functions other than the movement of the moving body.

(Fourth embodiment)
In the power conversion system 704 of the fourth embodiment shown in FIG. 14, adjustment converters 61 and 63 are provided between the secondary ports P21 and P23 corresponding to the high potential sides of the batteries BT1 and BT2 and the battery-side capacitors Cb1 and Cb3. Connected. The secondary ports P22, P24 corresponding to the low potential sides of the batteries BT1, BT2 and the battery-side capacitors Cb2, Cb4 are directly connected. That is, in the fourth embodiment, the secondary ports P21 and P23 are adjusting ports, and the secondary ports P22 and P24 are non-adjusting ports. Even in this way, the same effects as those of the above-described embodiment can be obtained.

(Fifth to seventh embodiments)
In the fifth to seventh embodiments, the specific circuit configuration of the primary side switching circuit 31 of the multiport isolated converter 300 or the adjustment converter 62 is changed from the configuration example shown in FIG. . Similar to FIGS. 8 and 9, FIGS. 15, 16 and 18 show only the configuration of the side corresponding to the first battery BT1.

In the power conversion system 705 of the fifth embodiment shown in FIG. 15, the primary side switching circuit 31 is composed of a full-bridge DC/DC converter 52 . Therefore, the multi-port isolated converter 300 is a dual active bridge (DAB) scheme with full bridges on both the primary and secondary sides. By making the primary-side switching circuit 31 a full-bridge type, it is possible to lower the withstand voltage of the switching elements compared to the half-bridge type. Also in the fifth embodiment, by fixing the duty ratio of the multi-port insulated converter 300 to 0.5, high-efficiency driving becomes possible.

In the power conversion system 706 of the sixth embodiment shown in FIG. 16, the adjustment converter 62 is configured with a boost converter 68 that functions as a boost circuit when charging the battery BT1 from the multiport isolated converter 300. FIG. The boost converter 68 is a chopper booster circuit including upper and lower arm switching elements 68a and 68b and a coil 68c. When charging the battery BT1, the boost converter 68 boosts the input voltage VL of the adjustment side port P22 and outputs it to the battery BT1 side.

A change in the battery voltage according to the SOC of the battery and adjustment of the battery side voltage by the boost converter 68 will be described with reference to FIGS. 16 and 17. FIG. Notes on the description follow the notes on the step-down converter 67 referring to FIGS. 9 and 10 . In the case of the boost converter 68, in order to set the input voltage VL to a value greater than 0, the voltage distribution ratio of the adjustment side port P22 to the voltage sum of the non-adjustment side port P21 and the adjustment side port P22 is α (0<α<1). do. A range from “(1−α)×Vmin” to Vmax is the voltage adjustment range of the boost converter 68 .

FIG. 16 shows the voltage distribution between the non-adjustment side port P21 and the adjustment side port P22 in the battery charging/discharging circuit 601. As shown in FIG. The voltage of the non-adjusted port P21 is set to "(1−α)×Vmin" based on the minimum battery voltage Vmin of the corresponding battery. Also, the input voltage VL of the adjustment side port P22 is set to "α×Vmin". Boosted voltage VH output from boost converter 68 is “Vb−(1−α)×Vmin”. This relationship is shown in FIG.

In the power conversion system 707 of the seventh embodiment shown in FIG. 18, the regulating converter 62 is composed of an isolated converter 69 . The isolated converter 69 can be controlled to be a buck converter or a boost converter when charging the battery. For example, in a configuration that functions as a step-down converter when charging a battery, output adjustment can be performed efficiently by setting the voltages of the non-adjustment side port P21 and the adjustment side port P22 as shown in FIG.

(Reference form)
FIG. 19 shows a reference embodiment to which the configuration of this embodiment is applied. In the power conversion system 701R of the reference form, the connection state of the two batteries BT1 and BT2 is fixed in series, and is not configured to be switchable between series and parallel. Also, an auxiliary load 49 is connected in parallel with one of the batteries (for example, the second battery BT2). Due to power consumption of auxiliary load 49, voltage Vb2 of second battery BT2 becomes lower than voltage Vb1 of first battery BT1.

Therefore, the drive circuit 75 drives the multiport isolation converter 300 and the adjustment converters 62, 64 to transfer power between the two batteries BT1, BT2, thereby increasing the voltage Vb2 of the second battery BT2. In this case, the voltages Vb1 and Vb2 of the two batteries BT1 and BT2 do not necessarily have to be equal. For example, in anticipation of future power consumption of auxiliary load 49, power transfer may be performed such that voltage Vb2 of second battery BT2 is higher than voltage Vb1 of first battery BT1.

(Other embodiments)
(a) The power conversion system of the present invention may be applied to an overall system including three or more batteries configured to be switchable between series connection and parallel connection. In that case, three or more batteries may be connected to the power conversion system at the same time. Alternatively, two batteries may be sequentially connected to the power conversion system.

The overall system shown in FIG. 20 uses series-parallel switching relays RY1a-RY3a, RY1b-RY3b, and RY1c-RY3c to connect three batteries BT1, BT2, and BT3 in either two series or two parallel, or three series or three series. It is configured to be switchable in parallel. Relays RY1a-RY3a switch series-parallel between first battery BT1 and second battery BT2, and relays RY1b-RY3b switch series-parallel between second battery BT1 and third battery BT32. Also, relays RY1c-RY3c switch series/parallel between the third battery BT3 and the first battery BT1. For example, when the relays RY2a and RY2b are ON, 3 series are formed, and when the relays RY1a, RY1b, RY3a and RY3b are ON, 3 parallel are formed.

A power conversion system 708 applied to this overall system has, in addition to the configuration of the power conversion system 701 shown in FIG. 5, a configuration corresponding to the third battery BT3. The multi-port isolated converter 308 further comprises secondary side switching circuits 45, 46 between the secondary windings 225, 226 and the secondary ports P25, P26. The high potential side battery side capacitor Cb5 is directly connected to the non-adjusted side port P25. The low-potential-side battery-side capacitor Cb6 is connected to the adjustment-side port P26 via the adjustment converter 66 .

(b) In the above embodiment, one non-adjustment side port and one adjustment side port of the multi-port isolated converter are provided for one corresponding battery. In another embodiment, a plurality of adjustment-side ports may be provided for one corresponding battery like the multi-port isolated converter 3091 of the power conversion system 7091 shown in FIG. Alternatively, a plurality of non-adjustment side ports may be provided like the multiport isolated converter 3092 of the power conversion system 7092 shown in FIG.

The power conversion system 7091 shown in FIG. 21 has two sets of the elements of the code|symbol "222, 224, 42, 44, 62, 64, Cb2, Cb4" in the power conversion system 701 shown in FIG. In FIG. 21, "1" and "2" are added to the end of the reference numerals of the above elements. The power conversion system 7092 shown in FIG. 22 has two sets of elements of the code "221, 223, 41, 43, 61, 63, Cb1, Cb3" in the power conversion system 701 shown in FIG. In FIG. 22, "1" and "2" are added to the end of each element.

In the power conversion systems 7091 and 7092, the voltage setting of each secondary port in the configuration using the step-down converter for the regulating converter shown in FIGS. 9 and 10 is extended as follows. Both will be described using symbols on the side of the first battery voltage Vb1.

In the power conversion system 7091 having a plurality of adjustment-side ports, the sum of the voltages VH1 and VH2 of the plurality of adjustment-side ports P221 and P222 is set to the difference value between the maximum battery voltage Vmax and the minimum battery voltage Vmin of the corresponding battery. be. Further, the sum of the stepped-down voltages VL1 and VL2 of the plurality of adjustment converters 621 and 622 is the difference value (Vb-Vmin) between the battery voltage Vb and the battery minimum voltage Vmin. In the power conversion system 7092 having a plurality of non-adjustment side ports, the sum of the voltages V1 and V2 of the plurality of non-adjustment side ports P211 and P212 is set to the battery minimum voltage Vmin of the corresponding battery.

Reference numerals used only in FIGS. 20 to 22 of other embodiments are not described as reference numerals in the column of [Description of Codes] and claims.

(c) In the above embodiment, the duty ratio of the multiport isolation converter is set to a fixed value in the high efficiency region, but in other embodiments, the duty ratio of the multiport isolation converter may be variably controlled. In that case, for example, the variable range of the duty ratio may be limited to a high-efficiency range, combined with adjustment of the output voltage by the adjustment converter, and controlled at a fine adjustment level.

As described above, the present invention is by no means limited to the above embodiments, and can be embodied in various forms without departing from the spirit of the present invention.

150 External power supply,
200, 201, 202...transformers,
211, 212... primary windings, 221-224... secondary windings,
300, 301, 302...multiport isolated converters,
31, 32... primary side switching circuit,
41-44 ... secondary side switching circuit,
61-64 Regulating converter,
70 (701-707), power conversion system,
75 ... drive circuit,
BT1, BT2... battery,
P11, P12...Primary ports,
P21-P24--Secondary ports.

Claims (7)

provided between an external power supply (150) capable of outputting electric power and a plurality of batteries (BT1, BT2) configured to switch between series connection and parallel connection, and between the external power supply and the plurality of batteries A power conversion system capable of bidirectionally transmitting and receiving power in
One unit is connected to the external power supply, or a plurality of units corresponding to the plurality of batteries are connected in parallel, and each unit is connected to the primary port (P11, P12) on the external power supply side. a transformer (200, 201, 202) having one primary winding (211, 212) and a plurality of secondary windings (221-224) connected to a plurality of secondary ports (P21-P24) on the battery side; one primary side switching circuit (31, 32) provided between the primary port and the primary winding; and a primary switching circuit (31, 32) provided between the plurality of secondary ports and the plurality of secondary windings. a multi-port isolated converter (300, 301, 302) having a plurality of secondary side switching circuits (41-44);
a plurality of regulating converters (61-64) connected between a regulating port, which is a portion of the plurality of secondary ports corresponding to each of the batteries, and the battery and capable of regulating the voltage on the battery side; and,
a driving circuit (75) for driving the multi-port isolated converter and the regulating converter and controlling the operation of the regulating converter to regulate the voltage on the battery side;
with
Before switching a plurality of said batteries into parallel connection,
The power conversion system, wherein the drive circuit drives the multiport isolation converter and the adjustment converter to transfer power so that the voltage difference between the plurality of batteries is equal to or less than a predetermined value. In driving the multiport isolated converter by the driving circuit,
Duty ratio defining a ratio of ON / OFF time of a plurality of switching elements constituting the primary side switching circuit and a plurality of the secondary side switching circuit, power conversion according to claim 1 is set to a fixed value system. 3. The power conversion system according to claim 1, wherein the adjustment converter is a step-down converter (67) capable of stepping down the voltage of the adjustment side port and outputting it to the battery side when charging the battery. Assuming that the secondary ports other than the adjustment-side port are non- adjustment-side ports,
4. The power conversion according to claim 3, wherein the sum of the voltages of the non-regulated ports corresponding to each battery is set to a battery minimum voltage (Vmin) that is the voltage when the SOC of the corresponding battery is 0%. system.
The sum of the voltages of the adjustment-side ports corresponding to each of the batteries is a battery maximum voltage (Vmax) that is the voltage when the SOC of the corresponding battery is 100%, and the voltage when the SOC of the corresponding battery is 0%. 5. The power conversion system according to claim 3 or 4, wherein the voltage is set to a difference value from the battery minimum voltage (Vmin) which is the voltage of . The power conversion system according to any one of claims 1 to 5, wherein the power conversion system is mounted on a moving object powered by a plurality of said batteries. Assuming that the plurality of batteries in the moving object are main batteries,
At least one of the plurality of secondary ports of the isolated converter is further connected to an auxiliary battery, which is a battery different from the main battery, or to an auxiliary load that performs a function other than movement of the moving object. 7. The power conversion system of claim 6.

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