JP2005033954A - Battery charger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery charger at low cost capable of charging the battery of an own vehicle different in voltage by using a battery mounted in a wrecking car without the need for mounting an exclusive charger. <P>SOLUTION: The battery charger 1 comprises the high-voltage battery 10 that stores power; an inverter 12 that converts the power stored in the high-voltage battery 10 to an AC from a DC and outputs it; a motor generator 14 that is driven by AC power outputted from the inverter 12; a reactor 16 that temporarily stores electric energy fed from an external battery 24 when charging the high-voltage battery 10 by the external battery 24, and outputs the stored electric energy to the high-voltage battery 10 via the motor generator 14 and the inverter 12; and an ECU 30 that operates the inverter 12 so that an output voltage of the reactor 16 reaches a voltage necessary for charging the high-voltage 10 when charging. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a battery charging device for a vehicle.

  In a hybrid vehicle using both an engine and an electric motor, if the engine is started by an electric motor, the engine cannot be started if the high-voltage battery that supplies power to the electric motor is discharged. There is a possibility. Therefore, it is necessary to provide means capable of charging the high voltage battery separately from the normal charging system.

  Patent Document 1 below describes a battery charging device that charges a high-voltage battery using a 12V battery mounted in another vehicle (hereinafter referred to as “rescue vehicle”).

This battery charger operates as follows. That is, a booster cable or the like is used to connect the 12V system low voltage battery of the own vehicle and the 12V system battery of the rescue vehicle with the same polarity, and the charging switch is turned ON. Then, the DC voltage from the 12V system battery of the rescue vehicle input through the input filter is converted into AC by a bridge circuit using a transistor and boosted by a transformer. The AC output on the secondary side of the transformer is double-voltage rectified by a diode and a capacitor to become a DC high voltage. Therefore, the high voltage battery can be charged by the DC output from the voltage doubler rectifier circuit unit.
JP 2000-299902 A (page 3-6, FIG. 1)

  Conventionally, when charging a high-voltage battery of a host vehicle from a battery mounted on a rescue vehicle, it is necessary to provide a dedicated charging device as described above, and there is a problem that costs increase.

  The present invention has been made to solve the above-described problems, and can charge a battery of a host vehicle having a different voltage using a battery mounted in a rescue vehicle without providing a dedicated charging device. An object of the present invention is to provide a possible battery charger at a low cost.

  A battery charging apparatus according to the present invention includes a battery for storing electric power, an inverter for converting electric power stored in the battery from direct current to alternating current, an electric motor driven by alternating current power output from the inverter, an external When the battery is charged by the power source, the electric energy supplied from the external power source is temporarily stored, the reactor that outputs the stored electric energy to the battery via the electric motor and the inverter, and the output voltage of the reactor at the time of charging And a control means for operating the inverter so as to obtain a voltage necessary for charging the battery.

  According to the battery charging device of the present invention, since the electric energy accumulated in the reactor is released in the form of back electromotive force by the operation of the inverter, the voltage from the external power source is transformed to the voltage necessary for charging the battery. Can do. This makes it possible to charge the battery.

  In the battery charging apparatus according to the present invention, the electric motor is a three-phase AC motor, and the control means calculates the time for storing electric energy in the windings and reactors of each phase according to the voltage required for charging the battery. It is preferable to operate the inverter based on this time.

  The voltage transformation width changes in accordance with the amount of electrical energy accumulated in each winding and reactor of the three-phase winding. In this case, since the amount of electrical energy accumulated in each winding and reactor is adjusted according to the charging voltage of the battery, it is possible to adjust the output voltage of the reactor to a voltage required for charging the battery.

  The battery charging device according to the present invention preferably further comprises voltage detection means for detecting the voltage of the battery, and the voltage required for charging the battery is preferably set according to the battery voltage detected by the voltage detection means.

  In this way, the charging voltage can be adjusted appropriately according to the battery voltage.

  Moreover, it is preferable that the control means operates the inverter so that the timing for storing electric energy is shifted by 120 degrees between the phases.

  In this case, the timing of accumulating electric energy is shifted by 120 degrees, so that the increase and decrease in current cancel each other, so that the charging current ripple can be reduced.

  The battery charging device according to the present invention further includes a current detection means for detecting a charging current, and the control means supplies electric energy to each winding and the reactor so that the current value detected by the current detection means is a predetermined value or less. It is preferable to calculate a time for accumulating and to operate the inverter based on the time.

  In this case, since the charging current can be limited to a predetermined value or less, the reactor can be miniaturized.

  According to the present invention, the electric energy supplied from the external power source is temporarily stored, the reactor that outputs the stored electric energy to the battery, and the output voltage of the reactor becomes the voltage necessary for charging the battery during charging. In this way, by including the control means for operating the inverter, the battery of the host vehicle can be charged using the battery mounted on the rescue vehicle without providing a dedicated charging device.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the figure, the same reference numerals are used for the same or corresponding parts.

(First embodiment)
First, the configuration of the battery charger 1 according to the first embodiment will be described with reference to FIG.

  The positive electrode of the high voltage (for example, 36 V) battery 10 is connected to the inverter 12. On the other hand, the negative electrode of the high-voltage battery 10 is connected to the inverter 12 and grounded to a power ground such as a vehicle body. Here, a secondary battery such as a sealed lead battery or nickel hydride is used as the high voltage battery 10.

  The inverter 12 is composed of six switching elements (for example, power MOS FETs). More specifically, between the power supply line and the power ground, a U-phase arm composed of a series connection of power MOS FETs Q1, Q2, a V-phase arm composed of a series connection of power MOS FETs Q3, Q4, and a power MOS FET Q5, A W-phase arm composed of Q6 connected in series is arranged.

  An intermediate point of each phase arm of inverter 12 is connected to each end of each phase coil of motor generator 14 which is a three-phase AC motor. That is, one end of the three U, V, and W coils of the motor generator 14 is commonly connected at a neutral point 14n, and the other end of the U phase coil 14a is at the intermediate point between the power MOS FETs Q1 and Q2, and the V phase The other end of the coil 14b is connected to an intermediate point between the power MOS FETs Q3 and Q4, and the other end of the W-phase coil 14c is connected to an intermediate point between the power MOS FETs Q5 and Q6.

  Note that the motor generator 14 is driven by AC power output from the inverter 12 during normal traveling or the like. The motor generator 14 can also generate electric power by utilizing rotation of the engine or the like. On the other hand, the inverter 12 converts the electric power stored in the high-voltage battery 10 from direct current to alternating current and supplies the electric power generated by the motor generator 14 to the direct current from the alternating current during direct running or the like. And stored in the high-voltage battery 10.

  One end of a reactor 16 is connected to the neutral point 14 n of the motor generator 14. The other end of the reactor 16 is connected to a terminal of the charging connector 18. This charging connector 18 is for connecting a battery (external power source, hereinafter referred to as “external battery”) 24 of a rescue vehicle in an emergency such as when the high voltage battery 10 is discharged. A voltage sensor 20 </ b> A for detecting the voltage of the external battery 24 is connected in parallel with the charging connector 18. An output signal from the voltage sensor 20 </ b> A is input to an electronic control unit (hereinafter referred to as “ECU”) 30.

  In addition to the voltage sensor 20A, the ECU 30 is connected to a voltage sensor 20B that detects the voltage of the high-voltage battery 10, a charge switch (not shown) that gives a charge command to the ECU 30 when charging from a rescue vehicle, and the like. ing. Further, the ECU 30 includes an output circuit that outputs a switching signal for driving the power MOS FETs Q1 to Q6 of the inverter 12.

  The ECU 30 includes a microprocessor that performs calculations therein, a ROM that stores programs for causing the microprocessor to execute each process, a RAM that stores various data such as calculation results, and the high-voltage battery 10. A backup RAM or the like is held.

  As a result, the ECU 30 includes a power MOS that configures the inverter 12 so that the output voltage of the reactor 16 becomes a voltage necessary for charging the high-voltage battery 10 (for example, 42 V) when charging from the external battery 24. A control unit 30a for controlling the driving of the FETs Q1 to Q6 is constructed. That is, the ECU 30 functions as a control unit.

  Next, the operation of the battery charger 1 when the high voltage battery 10 is charged from the external battery 24 will be described with reference to FIG. FIG. 2 is a flowchart showing a processing procedure of a charging process using the external battery 24 by the battery charging device 1.

  In step S100, it is determined whether or not the charging switch is turned on. If the charge switch is off, it is determined that there is no charge request, and the process ends without performing the charge process. On the other hand, if the charge switch is on, the process proceeds to step S102.

  In step S102, it is determined whether or not the external battery 24 is securely connected to the charging connector 18. Specifically, it is determined whether or not a voltage equal to or higher than a predetermined value is detected from the charging connector 18. Here, when the voltage exceeding the predetermined value is not detected, it is determined that the external battery 24 is not securely connected, and this step is repeated until the voltage exceeding the predetermined value is detected from the charging connector 18. Execute. On the other hand, when a voltage of a predetermined value or more is detected from the charging connector 18, it is determined that the external battery 24 is securely connected, and the process proceeds to step S104.

  In step S104, the charging process by the battery charging device 1 is executed. Here, with reference to FIG. 3, the charge control of the battery charger 1 will be described in detail. FIG. 3 is a diagram for explaining switching control of the inverter 12 in the battery charging device 1.

  As shown in FIG. 3, the battery voltage Vb36 of the high voltage battery 10 detected by the voltage sensor 20B and the target charging voltage Vb36 * of the high voltage battery 10 are input to the subtractor 30b, and the difference between them is calculated. . The obtained deviation ΔVb36 between the target charging voltage Vb36 * and the actual battery voltage Vb36 is output to the control unit 30a. Based on the input deviation ΔVb36, the control unit 30a calculates feedback coefficients for the P term (proportional term), I term (integral term), and D term (differential term) in so-called PID control. Based on each feedback coefficient, the command value Vn is determined so that the battery voltage Vb36 of the high voltage battery 10 becomes the target charging voltage Vb36 *. In place of PID control, P control, PI control, or the like may be used.

  Further, command values Vu, Vv, Vw for each phase of motor generator 14 are obtained from command value Vn. However, in this embodiment, Vn = Vu = Vv = Vw.

  Next, in the comparator 30c, the switching signals Su, Sv, Sw of the upper power MOS FETs Q1, Q3, Q5 of each arm and the switching signals -Su, -Sv, -Sw of the lower power MOS FETs Q2, Q4, Q6 Is generated. The switching signals -Su, -Sv, -Sw are obtained by inverting the switching signals Su, Sv, Sw.

  Here, a method for generating the switching signal Su will be described using the U phase as an example. A sawtooth carrier signal Cu and a command value Vu are input to the comparator 30c. When “command value Vu ≦ carrier signal Cu”, the switching signal Su (for example, 5V) is set so that the upper power MOS FET Q1 is turned on. Is output. On the other hand, when “command value Vu> carrier signal Cu”, the switching signal Su (for example, 0 V) is output so that the upper power MOS FET Q1 is turned off. Further, as described above, the switching signal -Su of the lower power MOS FET Q2 is generated by inverting the switching signal Su.

  That is, switching control is performed so that when the upper power MOS FET Q1 is turned on, the lower power MOS FET Q2 is turned off, and when the upper power MOS FET Q1 is turned off, the lower power MOS FET Q2 is turned on. Note that the method for generating the switching signals Sv and Sw in the V-phase and the W-phase is the same as or similar to that in the U-phase, and the description thereof is omitted here.

  In the present embodiment, the neutral point voltage and the command value Vn are made different by changing the ratio of the ON time of the upper power MOSFETs Q1, Q3, Q5 of the inverter 12 and the ON time of the lower power MOSFETs Q2, Q4, Q6. Is controlled to match. The reason will be described next.

  When the upper power MOSFETs Q1, Q3, and Q5 are turned off and the lower power MOSFETs Q2, Q4, and Q6 are turned on, current flows in the phase coils 14a, 14b, and 14c of the reactor 16 and the motor generator 14, and energy is accumulated. Next, when the upper power MOSFETs Q1, Q3, Q5 are turned on and the lower power MOSFETs Q2, Q4, Q6 are turned off, the energy accumulated in the phase coils 14a, 14b, 14c of the reactor 16 and the motor generator 14 is reversed. Released as electromotive force. At this time, the voltage applied to the high voltage battery 10 is obtained by adding the back electromotive force to the battery voltage of the external battery 24. In this way, the voltage of the external battery 24 is boosted.

  Here, the voltage is boosted by adjusting the ratio between the on-time of the upper power MOSFETs Q1, Q3, and Q5, that is, the energy release time, and the on-time of the lower power MOSFETs Q2, Q4, and Q6, that is, the energy storage time. The width can be adjusted. That is, when the ratio of the on-time of the upper power MOSFETs Q1, Q3, Q5 and the on-time of the lower power MOSFETs Q2, Q4, Q6 is 1: 1, the voltage of the external battery 24 is boosted approximately twice. Is done. Further, when the ratio is 1: 2, the voltage is boosted about three times, and when the ratio is 1: 3, the voltage is boosted about four times. Therefore, for example, when the external battery 24 is a 12V battery (charging voltage 14V) and the high-voltage battery 10 is a 36V battery (charging voltage 42V), the ON time and lower side of the upper power MOS FETs Q1, Q3, Q5 The ratio of the power MOS FETs Q2, Q4 and Q6 to the on time is set to about 1: 2.5.

  Further, in the present embodiment, the phases of the carrier signal Cu, the carrier signal Cv, and the carrier signal Cw are set to be different from each other by 120 degrees. Next, referring to FIG. 4, switching signals Su, Sv, Sw generated from carrier signals Cu, Cv, Cw and command values Vu, Vv, Vw in each phase, and a charging current flowing through neutral point 14n The relationship with In (hereinafter referred to as “neutral point current”) will be described. FIG. 4 shows switching signals Su, Sv generated from carrier signals Cu, Cv, Cw and control signals Vu, Vv, Vw when the phases of carrier signals Cu, Cv, Cw of each phase are shifted by 120 degrees. , Sw and the neutral point current In.

  4A and 4B show the relationship between the switching signal Su generated from the carrier signal Cu and the command value Vu in the U phase. As shown in FIG. 4A, the carrier signal Cu is a sawtooth wave signal in which a predetermined triangular wave is repeated at a predetermined period. Further, as described above, when the command value Vu is equal to or lower than the carrier signal Cu, a switching signal Su (ON signal) that turns on the power MOS FET Q1 on the upper side of the arm is output. On the other hand, when the command value Vu is larger than the carrier signal Cu, a switching signal Su (off signal) that turns off the power MOS FET Q1 on the upper side of the arm is output.

  Similarly, FIGS. 4C and 4D show the relationship between the switching signal Sv generated from the carrier signal Cv and the command value Vv in the V phase. FIGS. 4E and 4F show the relationship between the switching signal Sw generated from the carrier signal Cw and the command value Vw in the W phase. Note that details of each signal in the V phase and the W phase are the same as or similar to those in the U phase, and thus the description thereof is omitted here.

  Here, as shown in FIGS. 4A, 4C, and 4E, the phases of the carrier signals Cu, Cv, and Cw are shifted by 120 degrees. As a result, the phases of the switching signals Su, Sv, Sw in each phase are also shifted by 120 degrees (see FIGS. 4B, 4D, and 4F).

  On the other hand, the neutral point current In decreases when the power MOSFETs Q1, Q3, and Q5 on the upper side of the arm are turned on, and is lower when the power MOSFETs Q1, Q3, and Q5 on the upper side of the arm are turned off. Increases when the power MOS FETs Q2, Q4, and Q6 are turned on. Note that the neutral point voltage also moves in the same manner as the neutral point current In. Here, when the phases of the carrier signals Cu, Cv, and Cw are shifted by 120 degrees from each other and the phases of the switching signals Su, Sv, and Sw are shifted by 120 degrees, the currents in the respective phases increase or decrease the charging current. Since they cancel each other, the ripple of the charging current can be reduced (see FIG. 4G).

  On the other hand, when the phases of the carrier signals Cu, Cv, Cw are the same, the switching signals Su, Sv, Sw generated from the carrier signals Cu, Cv, Cw and the control signals Vu, Vv, Vw, The relationship with the neutral point current In will be described with reference to FIG.

  5A and 5B show the relationship between the switching signal Su generated from the carrier signal Cu and the command value Vu in the U phase. Details are the same as those in FIGS. 4 (a) and 4 (b), and a description thereof will be omitted here. Similarly, FIGS. 5C and 5D show the relationship between the switching signal Sv generated from the carrier signal Cv and the command value Vv in the V phase. 5E and 5F show the relationship between the switching signal Sw generated from the carrier signal Cw and the command value Vw in the W phase. Note that details of each signal in the V phase and the W phase are the same as or similar to those in the U phase, and thus the description thereof is omitted here.

  Here, as shown in FIGS. 5A, 5C, and 5E, the phases of the carrier signals Cu, Cv, and Cw are set to be the same. Thereby, the phases of the switching signals Su, Sv, Sw in each phase are also the same (see FIGS. 5B, 5D, 5F).

  On the other hand, the charging current of the high voltage battery 10 decreases when the power MOS FETs Q1, Q3, and Q5 on the upper side of the arm are turned on, and the power MOS FETs Q1, Q3, and Q5 on the upper side of the arm are turned off, that is, the arm. It increases when the lower power MOSFETs Q2, Q4, Q6 are on. Here, since the phases of the carrier signals Cu, Cv and Cw in each phase are the same, the phases of the switching signals Su, Sv and Sw are also the same. In this case, since the current in each phase does not cancel out the increase or decrease in the charging current, the ripple of the charging current increases compared to the case where the phase is shifted by 120 degrees (FIG. 5 (g)). reference).

  Returning to FIG. 2 and continuing the description, in step S106, it is determined whether or not the charging is completed based on the charging current value, the voltage value of the high voltage battery 10, or the like. If it is determined that charging has not been completed, the process returns to step S104, and the charging process is continued until charging is completed. On the other hand, if it is determined that charging is complete, the process is terminated.

  According to the battery charger 1, energy is stored in the reactor 16 or the like when the lower power MOS FETs Q2, Q4, and Q6 are turned on, and when the upper power MOS FETs Q1, Q3, and Q5 are turned on. In addition, since the stored energy is released in the form of back electromotive force, the voltage of the external battery 24 can be boosted. Further, the boost width can be adjusted in accordance with the charging voltage of the high voltage battery 10 by adjusting the ratio of the on time of the power MOS FETs Q2, Q4, Q6 and the on time of the power MOS FETs Q1, Q3, Q5. Thereby, it becomes possible to charge the high voltage battery 10 different from the voltage of the external battery 24.

  In addition, by shifting the timing for storing and releasing energy, that is, the switching timing of the power MOS FET corresponding to each phase by 120 degrees, the currents flowing in each phase cancel each other, reducing the ripple of the charging current can do.

(Second Embodiment)
Next, the configuration of the battery charger 2 according to the second embodiment will be described with reference to FIG. The battery charging device 2 is different from the battery charging device 1 in that a current sensor 40 that detects a neutral point current is provided between the reactor 16 and the neutral point 14 n of the motor generator 14. Alternatively, each phase current of motor generator 14 may be detected, and the neutral point current may be obtained based on the detected phase current value. Since other configurations are the same as those of the battery charging device 1, the description thereof is omitted here.

  Next, the operation of the battery charging device 2 will be described with reference to FIG. FIG. 7 is a diagram for explaining switching control of the inverter 12 in the battery charging device 2.

  As shown in FIG. 7, the neutral point current In detected by the current sensor 40 and the target current value In * are input to the subtractor 30b, and the difference ΔIn is calculated. The obtained deviation ΔIn between the target current value In * and the actual neutral point current In is output to the control unit 30a. Based on the input deviation ΔIn, the control unit 30a calculates feedback coefficients for the P term (proportional term), I term (integral term), and D term (differential term) in so-called PID control. Based on each feedback coefficient, the command value Vn is determined so that the neutral point current In becomes the target current value In *. In place of PID control, P control, PI control, or the like may be used.

  Further, command values Vu, Vv, Vw for each phase of motor generator 14 are obtained from command value Vn. However, in this embodiment, Vn = Vu = Vv = Vw.

  Next, in the comparator 30c, the switching signals Su, Sv, Sw of the upper power MOS FETs Q1, Q3, Q5 of each arm and the switching signals -Su, -Sv, -Sw of the lower power MOS FETs Q2, Q4, Q6 Is generated. The switching signals -Su, -Sv, -Sw are obtained by inverting the switching signals Su, Sv, Sw. Note that the method of generating the switching signals Su, Sv, Sw is the same as or similar to that in the first embodiment, and therefore detailed description thereof is omitted here.

  According to the battery charger 2, the neutral point current In, that is, the charging current can be adjusted to the target current value In *, so that an excessive current can be prevented from flowing through the reactor 16. Therefore, the reactor 16 can be reduced in size.

  Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications can be made. For example, in the above embodiment, the phases of the carrier signals Cu, Cv, and Cw are shifted from each other by 120 degrees, but may be the same phase. Further, boosting may be performed using only one of the three phases of the U phase, the V phase, and the W phase. Further, a large capacity capacitor may be used instead of the high voltage battery 10.

It is a figure which shows the structure of the battery charging device which concerns on 1st Embodiment. It is a flowchart which shows the process sequence of the charging process by the battery charging device which concerns on 1st Embodiment. It is a figure for demonstrating switching control of the inverter in the battery charging device which concerns on 1st Embodiment. It is a figure which shows the relationship between the switching signal produced | generated from a carrier signal and a control signal, and a charging current when the phase of the carrier signal of each phase is shifted 120 degree | times. It is a figure which shows the relationship between the switching signal produced | generated from a carrier signal and a control signal, and a charging current when the phase of the carrier signal of each phase is made into the same phase. It is a figure which shows the structure of the battery charging device which concerns on 2nd Embodiment. It is a figure for demonstrating switching control of the inverter in the battery charging device which concerns on 2nd Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Battery charging device, 10 ... High voltage battery, 12 ... Inverter, 14 ... Motor generator, 14n ... Neutral point, 14a ... U-phase coil, 14b ... V-phase coil, 14c ... W-phase coil, 16 ... Reactor, 18 ... charging connector, 20A, 20B ... voltage sensor, 24 ... external battery, 30 ... ECU, 30a ... control unit, 40 ... current sensor, Q1, Q2, Q3, Q4, Q5, Q6 ... power MOS FET.

Claims (5)

A battery for storing power,
An inverter that converts the power stored in the battery from direct current to alternating current and outputs, and
An electric motor driven by AC power output from the inverter;
A reactor for temporarily storing electric energy supplied from the external power source when the battery is charged by an external power source, and outputting the stored electric energy to the battery via the electric motor and the inverter;
And a control means for operating the inverter so that an output voltage of the reactor becomes a voltage necessary for charging the battery during charging. The electric motor is a three-phase AC motor,
The control means calculates a time for accumulating electrical energy in each phase winding and the reactor according to a voltage required for charging the battery, and operates the inverter based on the time. The battery charger according to claim 1. Voltage detection means for detecting the voltage of the battery,
The battery charging apparatus according to claim 2, wherein a voltage necessary for charging the battery is set according to a battery voltage detected by the voltage detection unit. 4. The battery charging device according to claim 2, wherein the control unit operates the inverter so that the timing of storing electric energy is shifted by 120 degrees between the phases. 5. It further comprises current detection means for detecting the charging current,
The control means calculates a time for accumulating electric energy in the windings and the reactor so that a current value detected by the current detection means is a predetermined value or less, and operates the inverter based on the time. The battery charger according to any one of claims 2 to 4, wherein the battery charger is provided.

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