JP2011155737A - Battery charging device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve quick battery charging while suppressing power input into a charging system that quickly charges a plurality of batteries. <P>SOLUTION: A first charger 410 and second charger 420 output power in a mode selected form a first or second charging mode. In the first charging mode, an output power P1 of the first charger 410 is the same with an output power P2 of the second charger 420. In the second charging mode, an output power of the first charger 410 is increased. The second charger 420 outputs power where the output power P1 of the first charger 410 reduced from the largest power Pmax that the first charger 410 outputs. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a battery charging system, and more particularly to a technique for charging a plurality of batteries.

  Conventionally, an electric vehicle that travels with a driving force from an electric motor is known. Generally, a battery for storing electric power to be supplied to an electric motor is mounted on an electric vehicle. The battery is charged with electric power supplied from the outside of the electric vehicle, for example, at a charging station or at home. A predetermined time is required for charging the battery. Even when a quick charger is used, charging takes a longer time than when fossil fuel such as gasoline is supplied. Therefore, it is desirable to shorten the battery charging time. However, there are still many technical problems to be overcome in order to make the battery charging time equal to or shorter than the fueling time.

  Therefore, a business model has been proposed in which a battery with a small remaining capacity is replaced with a fully charged battery instead of charging the battery. A battery mounted on an electric vehicle is replaced at a battery exchange station or the like installed as an infrastructure. In the battery exchange station, the battery removed from the electric vehicle is recharged in place of the fully charged battery. In the battery exchange station, it is necessary to charge a plurality of batteries in order to prepare fully charged batteries for an unspecified number of electric vehicles. Therefore, there is a need for a charging system that charges a plurality of batteries.

  Japanese Patent Laid-Open No. 9-233710 (Patent Document 1) regenerates an AC power supply using a charging rectifier circuit that rectifies an AC power supply and a storage battery connected in reverse parallel to the charging rectifier circuit and divided into a plurality of storage batteries. A regenerative battery rectifier circuit and a plurality of step-up / down converters provided between the rechargeable rectifier circuit and the divided storage battery are disclosed. According to the storage battery formation charging / discharging device described in this publication, each buck-boost converter can individually charge or discharge the storage battery. Therefore, charging and discharging of a plurality of storage batteries can be performed simultaneously.

JP-A-9-233710

  However, in a charging system configured to charge a plurality of batteries, when a large amount of power is supplied to each battery in order to shorten the charging time, the sum of the supplied power, that is, input to the charging system. The power that is generated becomes very large. Therefore, it is necessary to set a large amount of power that can be supplied to the battery exchange station by the power company. As a result, when it is determined that the electricity charge becomes higher as the power that can be supplied is larger, the electricity charge becomes higher. Further, in order to handle large electric power, a lead wire and a circuit having a large capacity are required. Therefore, the cost of the charging system itself can increase.

  When the power input to the charging system is reduced in order to reduce the cost, the power supplied to each battery is reduced. Therefore, the charging time of the battery can be lengthened. As a result, it may not be possible to prepare a fully charged battery for a driver desiring to replace the battery.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to realize rapid charging of a battery while suppressing power input to a charging system that charges a plurality of batteries. .

  A battery charging system according to a first invention is a battery charging system capable of charging a plurality of batteries. In this charging system, a first charger to which a battery is connected and outputs power and a battery different from the battery connected to the first charger are connected, and the maximum power that can be output is the first power. And a second charger smaller than the maximum power that can be output. The first charger and the second charger have a first mode in which the output power of the first charger and the output power of the second charger are the same, and the output power of the first charger. In a mode selected from among the second modes in which the second charger outputs power obtained by subtracting the output power of the first charger from the maximum power that can be output by the first charger. Output power.

  According to this configuration, for example, when the quick charge of the battery is not requested, the first mode is selected. In the first mode, the output power of the first charger and the output power of the second charger are the same. Thereby, although the charging time is not short, a plurality of batteries can be charged simultaneously. When the battery is required to be quickly charged, the second mode is selected. In the second mode, the output power of the first charger is increased. By supplying large power to the battery from the first charger having a relatively large capacity, the charging time of the battery connected to the first charger can be shortened. The second charger outputs power obtained by subtracting the output power of the first charger from the maximum power that can be output by the first charger. Thereby, the electric power input / output as the entire charging system can be limited to the maximum electric power that the first charger can output. Therefore, the battery can be rapidly charged while suppressing the power input to the charging system.

  In the battery charging system according to the second invention, in addition to the configuration of the first invention, when the second mode is selected, the first charger is the maximum that the first charger can output. Output power.

  According to this configuration, the battery connected to the first charger can be charged as quickly as possible.

  In the battery charging system according to the third invention, in addition to the configuration of the second invention, the voltage of the battery connected to the first charger is selected for the first charger and the second mode is selected. Is lower than the predetermined upper limit voltage, the maximum power that the first charger can output is output, the second mode is selected, and the voltage of the battery connected to the first charger is the upper limit. When the voltage is higher than the voltage, the output voltage is made constant. The second charger stops the power output when the second mode is selected and the voltage of the battery connected to the first charger is lower than the upper limit voltage, and the second mode is selected, And when the voltage of the battery connected to the 1st charger is more than an upper limit voltage, the electric power which subtracted the output power of the 1st charger from the maximum electric power which the 1st charger can output is outputted.

  According to this configuration, when the voltage of the battery connected to the first charger is low, that is, when the remaining capacity is small, the battery is charged with the maximum power that the first charger can output. In this case, the second charger stops outputting power. Thereby, the battery connected to the first charger can be rapidly charged while limiting the power input / output as the entire charging system to be equal to or lower than the maximum power that can be output by the first charger. When the voltage of the battery connected to the first charger is high, that is, when the remaining capacity is large, the first charger makes the output voltage constant. Thereby, the battery can be fully charged. In this case, the second charger outputs power obtained by subtracting the output power of the first charger from the maximum power that can be output by the first charger. Thereby, in addition to the battery connected to the first charger, the battery connected to the second charger can be charged. Therefore, a plurality of batteries can be charged simultaneously.

  In the battery charging system according to the fourth aspect of the invention, in addition to the configuration of the third aspect of the invention, the second charger is the voltage of the battery connected to the first charger when the second mode is selected. Is equal to or higher than the upper limit voltage, the output power is limited to a predetermined value or less.

  According to this configuration, it is possible to prevent output of electric power exceeding the capacity of the second charger.

  In the battery charging system according to the fifth invention, in addition to the configuration of the fourth invention, a battery connected to the first charger and a battery different from the battery connected to the second charger are connected. And a third charger in which the maximum power that can be output is the same as the maximum power that the second charger can output. And when the first mode is selected, the third charger outputs the same power as the output power of the first charger and the output power of the second charger, the second mode is selected, and When the voltage of the battery connected to the first charger is lower than the upper limit voltage, the output of power is stopped, the second mode is selected, and the output power of the second charger is a predetermined value. In some cases, a power obtained by subtracting the output power of the first charger and the output power of the second charger from the maximum power that can be output by the first charger is output.

  According to this configuration, another battery can be charged by the third charger.

  In the battery charging system according to the sixth aspect of the invention, in addition to the configuration of the fifth aspect of the invention, the first charger has a function of discharging the battery connected to the first charger. The second charger has a function of discharging a battery connected to the second charger. The third charger has a function of discharging the battery connected to the third charger. When discharging the battery connected to the first charger, the battery connected to the second charger and the battery connected to the third charger, the first charger controls the output voltage, The second charger controls the output current, and the third charger controls the output current.

  According to this configuration, by discharging from the battery, the battery can be used as a power source for electric devices other than the vehicle. Therefore, for example, when power supply from an electric power company to a house or the like is interrupted, a battery can be used as an emergency power source. In such a case, only the first charger having the largest power capacity controls the output voltage, and the other chargers control the output current. Thereby, the 1st charger can output big electric power compared with the electric power outputted from other chargers. Therefore, when the required power fluctuates, the first battery charger having a large capacity can cope with the power fluctuation. As a result, power can be supplied stably.

  In the battery charging system according to the seventh invention, in addition to the configuration of any one of the first to fourth inventions, the first charger has a function of discharging the battery connected to the first charger. . The second charger has a function of discharging a battery connected to the second charger. When discharging the battery connected to the first charger and the battery connected to the second charger, the first charger controls the output voltage, and the second charger controls the output current.

  According to this configuration, the battery can be used as a power source for electric devices other than the vehicle by discharging from the battery. Therefore, for example, when power supply from an electric power company to a house or the like is interrupted, a battery can be used as an emergency power source. In such a case, only the first charger having the largest power capacity controls the output voltage, and the second charger controls the output current. Thereby, the 1st charger can output big electric power compared with the electric power outputted from the 2nd charger. Therefore, when the required power fluctuates, the first battery charger having a large capacity can cope with the power fluctuation. As a result, power can be supplied stably.

It is a schematic block diagram which shows an electric vehicle. It is a figure which shows the electric system of an electric vehicle. It is a figure which shows a battery exchange station. It is a figure (the 1) which shows a charging system. It is a figure (the 2) which shows a charging system. It is a flowchart which shows the control structure of a charger. It is a figure which shows 1st charge mode. It is a figure (the 1) which shows a 2nd charge mode. It is a figure (the 2) which shows a 2nd charge mode. It is a figure (the 3) which shows a 2nd charge mode. It is a figure which shows a charging system when discharging from a battery.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

  Referring to FIG. 1, an electric motor 100, a battery 110, and an ECU (Electronic Control Unit) 120 are mounted on the electric vehicle. The electric vehicle travels by the driving force from the electric motor 100. That is, the electric motor 100 is mounted on an electric vehicle as a drive source.

  Electric motor 100 is a three-phase AC rotating electric machine including, for example, a U-phase coil, a V-phase coil, and a W-phase coil. The electric motor 100 is driven by electric power stored in the battery 110. The driving force of the electric motor 100 is transmitted to the driving wheel 130.

  At the time of regenerative braking of the electric vehicle, the electric motor 100 is driven by the drive wheels 130, and the electric motor 100 operates as a generator. As a result, the electric motor 100 operates as a regenerative brake that converts braking energy into electric power. The electric power generated by the electric motor 100 is stored in the battery 110.

  The battery 110 is an assembled battery configured by connecting a plurality of battery modules in which a plurality of battery cells are integrated in series. The voltage of the battery 110 is about 200V, for example. In addition to the electric motor 100, the battery 110 is charged with electric power supplied from a power source external to the electric vehicle. Further, as will be described later, the battery 110 can be replaced with another battery.

  The electric system of the electric vehicle will be further described with reference to FIG. The electric vehicle is provided with a converter 200 and an inverter 210.

  Converter 200 includes a reactor, two npn transistors, and two diodes. One end of the reactor is connected to the positive electrode side of each battery, and the other end is connected to the connection point of the two npn transistors.

  Two npn-type transistors are connected in series. The npn type transistor is controlled by the ECU 120. A diode is connected between the collector and emitter of each npn transistor so that a current flows from the emitter side to the collector side.

  For example, an IGBT (Insulated Gate Bipolar Transistor) can be used as the npn transistor. Instead of the npn type transistor, a power switching element such as a power MOSFET (Metal Oxide Semiconductor Field-Effect Transistor) can be used.

  When the electric power discharged from the battery 110 is supplied to the electric motor 100, the voltage is boosted by the converter 200. Conversely, when the battery 110 is charged with the power generated by the electric motor 100, the voltage is stepped down by the converter 200.

  Inverter 210 includes a U-phase arm, a V-phase arm, and a W-phase arm. The U-phase arm, V-phase arm and W-phase arm are connected in parallel. Each of the U-phase arm, the V-phase arm, and the W-phase arm has two npn transistors connected in series. Between the collector and emitter of each npn-type transistor, a diode for passing a current from the emitter side to the collector side is connected. A connection point of each npn transistor in each arm is connected to an end portion different from a neutral point of each coil of electric motor 100.

  The inverter 210 converts a direct current supplied from the battery 110 into an alternating current and supplies the alternating current to the electric motor 100. Further, the inverter 210 converts the alternating current generated by the electric motor 100 into a direct current. Converter 200 and inverter 210 are controlled by ECU 120.

  With reference to FIG. 3, a battery exchange station 300 for exchanging a battery of an electric vehicle will be described. In the battery exchange station 300, for example, the battery 110 whose remaining capacity has decreased is automatically replaced with a fully charged battery 112. It may be replaced manually.

  In the battery exchange station 300, the battery is replaced for an unspecified number of electric vehicles. Therefore, in the battery exchange station 300, it is necessary to prepare a fully charged battery for an unspecified number of electric vehicles. Therefore, as shown in FIG. 4, the battery exchange station 300 is provided with a charging system 400 that can charge a plurality of batteries 114, 116, and 118. 4 shows a system that can charge three batteries 114, 116, and 118, the number of batteries is not limited to three. A system capable of charging two batteries may be provided. A system capable of charging four or more batteries may be provided. A plurality of charging systems may be provided.

  Charging system 400 is controlled by a computer, for example. The charging system 400 includes an AC / DC conversion circuit 402, a first charger 410, a second charger 420, and a third charger 430. A separate battery is connected to each charger 410, 420, 430. More specifically, the battery 114 is connected to the first charger 410. A battery 116 different from the battery 114 connected to the first charger 410 is connected to the second charger 420. A battery 118 other than the battery 114 connected to the first charger 410 and the battery 116 connected to the second charger 420 are connected to the third charger 430. In FIG. 4, three chargers 410, 420, and 430 are shown, but two or four or more chargers may be provided.

  In the present embodiment, the maximum power that can be output by second charger 420 is smaller than the maximum power that can be output by first charger 410. The maximum power that the third charger 430 can output is the same as the maximum power that the second charger 420 can output.

  The charging system 400 will be described in more detail with reference to FIG. The AC / DC conversion circuit 402 is composed of a single-phase bridge circuit. The AC / DC conversion circuit 402 converts AC power supplied from, for example, a facility (such as a power plant or substation) owned by an electric power company into DC power. The AC / DC conversion circuit 402 can also function as a boost chopper circuit that boosts the voltage by using a coil as a reactor.

  Chargers 410, 420, and 430 are connected between AC / DC conversion circuit 402 and the battery. Chargers 410, 420, and 430 output power for charging batteries 114, 116, and 118. The chargers 410, 420, and 430 are insulating chargers having an insulating transformer. It is not necessary to use an insulated charger.

  DC / DC converters are used as the chargers 410, 420, and 430. First charger 410 includes a DC / AC conversion circuit 412, an insulation transformer 414, and a DC / AC conversion circuit 416.

  The DC / AC conversion circuit 412 is a single-phase bridge circuit. When charging a battery using power supplied from an electric power company, the DC / AC conversion circuit 412 converts DC power into high-frequency AC power and outputs it to the isolation transformer 414. On the other hand, when discharging the battery, the DC / AC conversion circuit 412 rectifies the AC power output from the insulation transformer 414 into DC power.

  Insulating transformer 414 includes a core made of a magnetic material, and a primary coil and a secondary coil wound around the core. The primary coil and the secondary coil are electrically insulated and connected to the DC / AC conversion circuit 412 and the DC / AC conversion circuit 416, respectively. Insulation transformer 414 converts high-frequency AC power received from DC / AC conversion circuit 412 into a voltage level corresponding to the turn ratio of the primary coil and the secondary coil, and outputs the voltage level to DC / AC conversion circuit 416.

  The DC / AC conversion circuit 416 includes a single-phase bridge circuit. When charging the battery using the power supplied from the power company, the DC / AC conversion circuit 416 rectifies the AC power output from the insulation transformer 414 into DC power. On the other hand, when discharging the battery, the DC / AC conversion circuit 416 converts the DC power into high-frequency AC power and outputs it to the isolation transformer 414. That is, the first charger 410 has a function of discharging the battery 114 connected to the first charger 410.

  Similar to the first charger 410, the second charger 420 includes a DC / AC conversion circuit 422, an insulation transformer 424, and a DC / AC conversion circuit 426. Similar to the first charger 410 and the second charger 420, the third charger 430 includes a DC / AC conversion circuit 432, an isolation transformer 434, and a DC / AC conversion circuit 436. Note that these functions are the same as those of the first charger 410. Therefore, detailed description thereof will not be repeated here. Similarly to the first charger 410, the second charger 420 has a function of discharging the battery 116 connected to the second charger 420. The third charger 430 has a function of discharging the battery 118 connected to the third charger 430.

  As will be described later, each of chargers 410, 420, and 430 outputs power in a mode selected from the first charging mode and the second charging mode. In the first charging mode, the output power P1 of the first charger 410, the output power P2 of the second charger 420, and the output power P3 of the third charger 430 are the same. Therefore, the electric power input / output as the entire charging system 400 is three times the electric power Pc output by each charger 410, 420, 430 in the first mode. However, when the voltage of each battery 114, 116, 118 exceeds a predetermined threshold value, each battery 114, 116, 118 is charged with a constant voltage.

  In the second charging mode, the output power of the first charger 410 is increased. More specifically, the first charger 410 outputs the maximum electric power Pmax (Pmax> Pc) that the first charger 410 can output. The first charger 410 can output the first charger 410 when the second charging mode is selected and the voltage V1 of the battery 114 connected to the first charger 410 is lower than a predetermined upper limit voltage. Outputs maximum power. The first charger 410 makes the output voltage constant when the second charging mode is selected and the voltage V1 of the battery 114 connected to the first charger 410 is equal to or higher than the upper limit voltage.

  The second charger 420 stops outputting power when the second charging mode is selected and the voltage V1 of the battery 116 connected to the first charger 410 is lower than the upper limit voltage. In addition, the second charger 420 is configured to output the maximum voltage that the first charger 410 can output when the second charging mode is selected and the voltage V1 of the battery 116 connected to the first charger 410 is equal to or higher than the upper limit voltage. Power obtained by subtracting the output power P1 of the first charger 410 from the power Pmax.

  Further, the second charger 420 sets the output power P2 to be equal to or lower than a predetermined value when the second charging mode is selected and the voltage V1 of the battery 114 connected to the first charger 410 is equal to or higher than the upper limit voltage. Restrict to. In the present embodiment, output power P2 of second charger 420 is limited to be equal to or lower than power Pc output from second charger 420 in the first charging mode.

  Third charger 430 stops outputting power when second charging mode is selected and voltage V1 of battery 114 connected to first charger 410 is lower than the upper limit voltage. Further, the third charger 430 selects the second mode, and the output power P2 of the second charger 420 is a predetermined value (power Pc output from the second charger 420 in the first charge mode). In this case, the power obtained by subtracting the output power P1 of the first charger 410 and the output power P2 of the second charger 420 from the maximum power Pmax that can be output by the first charger 410 is output.

  When discharging the battery 114 connected to the first charger 410, the battery 116 connected to the second charger 420, and the battery 118 connected to the third charger 430, the first charger 410 outputs the output voltage. The second charger 420 controls the output current, and the third charger 430 controls the output current. That is, among the three chargers 410, 420, and 430, only the first charger 410 controls the output voltage, and the other chargers 420 and 430 control the output current.

  Output currents I 1, I 2, I 3 of each charger 410, 420, 430 are detected by current sensors 451, 452, 453 and input to a computer that controls the charging system 400. The voltages V1, V2, and V3 of the batteries 114, 116, and 118 are detected by the voltage sensors 461, 462, and 463, and input to the computer that controls the charging system 400.

A control structure of chargers 410, 420, and 430 will be described with reference to FIG.
In step (hereinafter, step is abbreviated as S) 100, it is determined whether or not discharge of batteries 114, 116, 118 is required. For example, when a predetermined operation such as pressing a predetermined switch provided in charging system 400 is performed by the user, it is determined that discharging of batteries 114, 116, and 118 is requested.

  If discharging of batteries 114, 116, and 118 is requested (YES in S100), the process proceeds to S200. If discharging of batteries 114, 116, and 118 is not requested (NO in S100), the process proceeds to S102.

  In S102, it is determined whether quick charging of the battery is requested. For example, when a predetermined operation such as pressing a predetermined switch provided in charging system 400 is performed by the user, it is determined that quick charging is requested.

  If quick charge is requested (YES in S102), the process proceeds to S110. If quick charge is not requested (NO in S102), the process proceeds to S104.

  In S104, the first charging mode is selected, and batteries 114, 116, and 118 are charged in the first charging mode. Therefore, the output power P1 of the first charger 410, the output power P2 of the second charger 420, and the output power P3 of the third charger 430 are power Pc.

  In S110, the second charging mode is selected, and batteries 114, 116, and 118 are charged in the second charging mode. Therefore, the first charger 410 outputs the maximum power Pmax (Pmax> Pc) that can be output by the first charger 410. The second charger 420 and the third charger 430 stop outputting power. Therefore, the output power P2 of the second charger 420 and the output power P3 of the third charger 430 are “0”.

  In S112, it is determined whether or not voltage V1 of battery 114 is equal to or higher than the upper limit voltage. If voltage V1 of battery 114 is equal to or higher than the upper limit voltage (YES in S112), the process proceeds to S114. If not (NO in S112), the process returns to S100. In S114, first charger 410 keeps the output voltage constant.

  In S116, second charger 420 outputs power obtained by subtracting output power P1 of first charger 410 from maximum power Pmax that can be output by first charger 410.

  In S118, it is determined whether or not output power P2 of second charger 420 is greater than power Pc output from second charger 420 in the first charging mode. If output power P2 of second charger 420 is greater than power Pc output from second charger 420 in the first charging mode (YES in S118), the process proceeds to S120. If not (NO at 118), the process returns to S100.

  In S120, second charger 420 is controlled to output the same electric power as electric power Pc output from second charger 420 in the first charging mode. Therefore, the output power P2 of the second charger 420 is the same as the power Pc output from the second charger 420 in the first charging mode. Therefore, the output power P2 of the second charger 420 is limited to the power Pc output by the second charger 420 in the first charging mode.

  In S122, third charger 430 subtracts power obtained by subtracting output power P1 of first charger 410 and output power P2 of second charger 420 from maximum power Pmax that can be output by first charger 410. Output.

  In S200, it is determined whether charging of batteries 114, 116, and 118 is stopped. If charging of batteries 114, 116, and 118 is stopped (YES in S200), the process proceeds to S202. If not (NO in S200), the process returns to S100.

  In S202, each charger 410, 420, 430 is controlled to discharge each battery 114, 116, 118. In this case, the first charger 410 controls the output voltage. The second charger 420 controls the output current. The third charger 430 controls the output current.

  A function of charging system 400 according to the present embodiment based on the above-described structure and flowchart will be described.

  If discharging of batteries 114, 116, and 118 is not requested (NO in S100) and rapid charging is not requested (NO in S102), as shown in FIG. The battery 114, 116, 118 is charged in the first charging mode (S104). Therefore, the output power P1 of the first charger 410, the output power P2 of the second charger 420, and the output power P3 of the third charger 430 are power Pc. When the voltage of each battery 114, 116, 118 exceeds a predetermined threshold value, each battery 114, 116, 118 is charged with a constant voltage. Thereby, the plurality of batteries 114, 116, 118 can be charged simultaneously.

  When there is no battery fully charged in the battery exchange station 300, it is desirable to charge the battery as soon as possible. Therefore, when quick charging is requested (YES in S102), as shown in FIG. 8, the second charging mode is selected, and batteries 114, 116, and 118 are charged in the second charging mode (S110). ). Therefore, the first charger 410 outputs the maximum power Pmax that can be output by the first charger 410. Thereby, the electric power supplied to the battery 114 connected to the first charger 410 can be increased. The second charger 420 and the third charger 430 stop outputting power. Thereby, electric power Ps input / output as the entire charging system can be limited to the maximum electric power Pmax that the first charger 410 can output. Therefore, the plurality of batteries 114, 116, 118 cannot be rapidly charged at the same time, but the charging time of the battery 114 connected to the first charger 410 can be shortened. As a result, the battery 114 can be rapidly charged while suppressing the power Ps input to the charging system.

  If voltage V1 of battery 114 is equal to or higher than the upper limit voltage (YES in S112), first charger 410 keeps the output voltage constant in order to fully charge battery 114 accurately (S114). As shown in FIG. 9, the second charger 420 outputs power obtained by subtracting the output power P1 of the first charger 410 from the maximum power Pmax that can be output by the first charger 410 (S116). Thereby, in addition to the battery 114 connected to the first charger 410, the battery 116 connected to the second charger 420 can be charged.

  When the remaining capacity of the battery 114 connected to the first charger 410 increases, the voltage of the battery 114 increases. As a result, the output power of the first charger 410 decreases and the output power P2 of the second charger 420 increases. If output power P2 of second charger 420 is greater than power Pc output from second charger 420 in the first charge mode (YES in S118), output power P2 of second charger 420 is the first charge. The power is limited to the electric power Pc output from the second charger 420 in the mode (S120). Thereby, the output power P <b> 2 of the second charger 420 can be limited to the capacity of the second charger 420 or less.

  As shown in FIG. 10, the third charger 430 subtracts the output power P1 of the first charger 410 and the output power P2 of the second charger 420 from the maximum power Pmax that can be output by the first charger 410. The generated power is output (S122). Thereby, in addition to the battery 114 connected to the first charger 410 and the battery 116 connected to the second charger 420, the battery 118 connected to the third charger 430 can be charged. The same operation is performed when four or more chargers are provided.

  By the way, when the power supply from the electric power company to the house or the like is cut off for some reason, it is conceivable to use the battery of the battery exchange station 300 as a power source.

  Therefore, when batteries 114, 116, and 118 are requested to be discharged (YES in S100) and charging of batteries 114, 116, and 118 is stopped (YES in S200), each battery 114, 116, and 118 is discharged. The chargers 410, 420, and 430 are controlled so as to discharge (S202). As shown in FIG. 11, the first charger 410 controls the output voltage. The second charger 420 controls the output current. The third charger 430 controls the output current. As a result, the three chargers 410, 420, and 430 operate as power generators, and power generation control (discharge control) can be realized in conjunction with them. Therefore, when the required power fluctuates, the first charger 410 having a large capacity can cope with the power fluctuation. As a result, power can be supplied stably.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 100 Electric motor, 110, 112, 114, 116, 118 Battery, 200 Converter, 210 Inverter, 300 Battery exchange station, 400 Charging system, 402 AC / DC conversion circuit, 410 1st charger, 412, 416 DC / AC conversion Circuit, 414 Insulation transformer, 420 Second charger, 422, 426 DC / AC conversion circuit, 424 Insulation transformer, 430 Third charger, 432, 436 DC / AC conversion circuit, 434 Insulation transformer, 451, 452, 453 Current Sensor, 461, 462, 463 Voltage sensor.

Claims (7)

A battery charging system capable of charging a plurality of batteries,
A first charger to which a battery is connected and outputs power;
A second battery connected to a battery different from the battery connected to the first charger, wherein the maximum power that can be output is smaller than the maximum power that the first charger can output; With
The first charger and the second charger have a first mode in which the output power of the first charger and the output power of the second charger are the same, and the first charger A second mode in which the second charger outputs power obtained by subtracting the output power of the first charger from the maximum power that can be output by the first charger when the output power of the charger is increased. A battery charging system that outputs power in a mode selected from the above.   2. The battery charging system according to claim 1, wherein, when the second mode is selected, the first charger outputs the maximum power that can be output by the first charger. 3. The first charger is
When the second mode is selected and the voltage of the battery connected to the first charger is lower than a predetermined upper limit voltage, the maximum power that can be output by the first charger is output. ,
When the second mode is selected and the voltage of the battery connected to the first charger is equal to or higher than the upper limit voltage, the output voltage is made constant,
The second charger is
When the second mode is selected and the voltage of the battery connected to the first charger is lower than the upper limit voltage, the output of power is stopped,
When the second mode is selected and the voltage of the battery connected to the first charger is equal to or higher than the upper limit voltage, the first power is output from the maximum power that can be output by the first charger. The battery charging system according to claim 2, wherein electric power obtained by subtracting the output electric power of the charger is output.   When the second mode is selected and the voltage of the battery connected to the first charger is equal to or higher than the upper limit voltage, the second charger reduces the output power to a predetermined value or less. The battery charging system according to claim 3, wherein the battery charging system is limited. In the charging system, a battery connected to the first charger and a battery different from the battery connected to the second charger are connected, and the maximum power that can be output is the second charge. A third charger that is the same as the maximum power that the charger can output
The third charger is
When the first mode is selected, output the same power as the output power of the first charger and the output power of the second charger,
When the second mode is selected and the voltage of the battery connected to the first charger is lower than the upper limit voltage, the output of power is stopped,
When the second mode is selected and the output power of the second charger is the predetermined value, the first charge is calculated from the maximum power that can be output by the first charger. The battery charging system according to claim 4, wherein electric power obtained by subtracting the output power of the charger and the output power of the second charger is output. The first charger has a function of discharging a battery connected to the first charger;
The second charger has a function of discharging a battery connected to the second charger,
The third charger has a function of discharging a battery connected to the third charger;
When discharging the battery connected to the first charger, the battery connected to the second charger, and the battery connected to the third charger, the first charger outputs an output voltage. 6. The battery charging system according to claim 5, wherein the second charger controls an output current, and the third charger controls an output current. The first charger has a function of discharging a battery connected to the first charger;
The second charger has a function of discharging a battery connected to the second charger,
When discharging a battery connected to the first charger and a battery connected to the second charger, the first charger controls an output voltage, and the second charger outputs an output current. The battery charging system according to claim 1, wherein the battery charging system is controlled.

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