JP5407758B2 - Vehicle power supply - Google Patents

Description

  The present invention relates to a vehicle power supply device, and more particularly to a vehicle power supply device that uses a charge state estimated by estimating a charge state of a secondary battery for control of charge / discharge of the secondary battery.

  In hybrid vehicles, secondary batteries (hereinafter also referred to as batteries) are mainly used as power storage devices. The state of charge of the secondary battery (also referred to as SOC: State Of Charge, storage amount, remaining capacity, etc.) is calculated by correcting the integrated value of the charge / discharge current of the secondary battery based on the measured value of the terminal voltage. ing.

  For example, Japanese Patent Laying-Open No. 2009-5458 (Patent Document 1) discloses a charging state estimation method using current and voltage.

JP 2009-5458 A JP 2006-98135 A JP 2006-98134 A JP 2009-201197 A

  In the hybrid vehicle, the discharge from the secondary battery and the charge to the secondary battery are finely switched, and the state in which this fine switching continues when the user's operation time is long continues. In such a state, if the amount of increase / decrease (ΔSOC) in the state of charge is calculated using only the current integrated value, errors will accumulate.

  In order to reduce this error and improve the estimation accuracy of the state of charge, a method of estimating the SOC by estimating an open circuit voltage (OCV: Open Circuit Voltage) using a current-voltage plot, or a voltage using a battery model A method for calculating SOC from current and temperature has been proposed. However, regardless of the charge / discharge history, it is difficult to improve the SOC estimation accuracy uniformly, and there may be a moment when the error increases depending on the use conditions.

FIG. 8 is a diagram for explaining an example in which the error of the SOC estimated value increases.
Referring to FIG. 8, a situation where the discharge current IB from the secondary battery continues to be positive, that is, a situation where the discharge continues is shown. In such a situation, the SOC decreases monotonously. When the SOC increase / decrease amount (ΔSOC) is calculated based only on the integrated current value and the SOC is updated (SOCi), it matches the actual SOC. However, when the SOC is updated by correcting the voltage with respect to ΔSOC (SOCv), an error occurs at the initial stage of discharge, and the SOC changes temporarily as though the discharge has occurred.

  In recent years, plug-in hybrid vehicles that can be charged from the outside have been developed. In this plug-in hybrid vehicle, charging is performed when charging from the outside (external charging mode) or when preferentially using the energy of the battery that has been charged after stopping the engine (EV mode). Often, either one of the discharges simply continues. In such a region, the accuracy may be deteriorated by the conventional SOC estimation method.

  An object of the present invention is to provide a vehicle power supply apparatus in which ΔSOC is obtained by a method suitable for the charging / discharging process of a secondary battery and the estimation accuracy of the SOC is improved.

  In summary, the present invention is a power supply device for a vehicle, a chargeable / dischargeable secondary battery, a current sensor for detecting a current of the secondary battery, a charge state of the secondary battery, and an estimated charge. And a control device that controls charging and discharging of the secondary battery based on the state. The control device calculates first and second estimated values by the first and second estimation methods in a predetermined period, respectively, and calculates a charge amount to the secondary battery and a discharge amount from the secondary battery in the predetermined period. Observe and update the state of charge of the secondary battery based on one of the first and second estimated values based on the observation result. The first estimation method is a method of estimating the open circuit voltage of the secondary battery and determining the first estimated value based on a value obtained by correcting the open circuit voltage based on polarization. The second estimation method is an estimation method different from the first estimation method, and is a method for determining the second estimated value based on the result of integrating the current detected by the current sensor.

  Preferably, when the discharge is performed as a total within the predetermined period, the control device sets the first evaluation value indicating the degree of occurrence of charging in the predetermined period when the first evaluation value exceeds the first threshold value. The state of charge of the secondary battery is updated based on the estimated value of 1, and the state of charge of the secondary battery is updated based on the second estimated value when the first evaluation value does not exceed the first threshold value To do.

  Preferably, when the charging is performed as a total within the predetermined period, the control device sets the first evaluation value when the second evaluation value indicating the degree of occurrence of discharge in the predetermined period exceeds the second threshold value. The state of charge of the secondary battery is updated based on the estimated value of 1, and the state of charge of the secondary battery is updated based on the second estimated value when the second evaluation value does not exceed the second threshold value To do.

  Preferably, the vehicle is configured to be capable of external charging in which the secondary battery is charged from the outside of the vehicle. The case where charging is performed as a total within a predetermined period includes the time when external charging is performed.

  Preferably, the vehicle includes an engine and an electric motor capable of executing a power running operation and a regenerative operation. The case where the discharge is performed as a total within a predetermined period includes the time when the vehicle is driven by the electric motor while the engine is stopped.

  ADVANTAGE OF THE INVENTION According to this invention, the estimation precision of SOC of a secondary battery improves also in the vehicle which can take various charging / discharging states like a plug-in hybrid vehicle.

1 is a diagram illustrating a main configuration of a vehicle 1 according to an embodiment of the present invention. It is the figure which showed the relationship between the open circuit voltage (OCV: Open-Circuit Voltage) of a battery, and SOC. It is a wave form diagram for explaining the time change of the battery voltage at the time of charge, and the battery voltage at the time of discharge. It is a block diagram which shows the structure of the SOC estimation process which the control apparatus 30 performs. 5 is a flowchart for explaining a switching process related to a selection command unit 146 in FIG. 4. It is a figure for demonstrating the change of the switching determination parameter K. FIG. It is the figure which showed the example of SOC change when performing EV driving | running | working after plug-in charge, and HV driving | running | working. It is a figure for demonstrating the example which the error of a SOC estimated value expands.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

[Overall configuration of vehicle]
FIG. 1 is a diagram showing a main configuration of a vehicle 1 according to an embodiment of the present invention.

  Referring to FIG. 1, vehicle 1 includes batteries B1 and B2, boost converters 12-1 and 12-2, a smoothing capacitor CH, voltage sensors 10-1, 10-2, and 13, an inverter 14, Engine 4, motor generators MG <b> 1 and MG <b> 2, power split mechanism 3, and control device 30 are included.

  The batteries B1 and B2 mounted on the vehicle can be charged from the outside. For this purpose, vehicle 1 further includes a connector 6 that has a connector that can be connected to, for example, AC 100V or 200V commercial power supply 8, and is connected to positive line PL1 and negative line NL1. The charger 6 converts alternating current into direct current, regulates the voltage, and applies the voltage to the battery. In addition, in order to allow external charging, there are other methods such as connecting the neutral point of the stator coils of motor generators MG1 and MG2 to an AC power supply, and AC / DC converters including boost converters 12-1 and 12-2. A method of functioning as may be used.

  Smoothing capacitor CH smoothes the voltage boosted by boost converters 12-1 and 12-2. The voltage sensor 13 detects the inter-terminal voltage VH of the smoothing capacitor CH and outputs it to the control device 30.

  Inverter 14 converts DC voltage VH applied from boost converter 12-1 or 12-2 into a three-phase AC voltage and outputs the same to motor generators MG1 and MG2.

  Power split device 3 is a mechanism that is coupled to engine 4 and motor generators MG1 and MG2 and distributes power between them. For example, the power split mechanism 3 may be a planetary gear mechanism having three rotating shafts: a sun gear, a planetary carrier, and a ring gear. In the planetary gear mechanism, if rotation of two of the three rotation shafts is determined, rotation of the other one rotation shaft is forcibly determined. These three rotation shafts are connected to the rotation shafts of engine 4 and motor generators MG1, MG2, respectively. The rotation shaft of motor generator MG2 is coupled to the wheels by a reduction gear and a differential gear (not shown). Further, a reduction gear for the rotation shaft of motor generator MG2 may be further incorporated in power split device 3.

  Battery B1 has a positive electrode connected to positive electrode line PL1 and a negative electrode connected to negative electrode line NL1. Voltage sensor 10-1 measures voltage VB1 between the positive and negative electrodes of battery B1. In order to monitor the state of charge SOC1 of the battery B1 together with the voltage sensor 10-1, a current sensor 11-1 for detecting a current IB1 flowing through the battery B1 is provided. Further, the state of charge SOC1 of the battery B1 is detected by the control device 30. Control device 30 calculates state of charge SOC1 using a method which will be described later with reference to FIGS.

  Battery B2 has a positive electrode connected to positive electrode line PL2 and a negative electrode connected to negative electrode line NL2. Voltage sensor 10-2 measures voltage VB2 across the terminals of battery B2. In order to monitor the state of charge SOC2 of the battery B2 together with the voltage sensor 10-2, a current sensor 11-2 for detecting a current IB2 flowing through the battery B2 is provided. Further, the charging state SOC2 of the battery B2 is detected by the control device 30. Control device 30 calculates state of charge SOC2 using a method which will be described later with reference to FIGS.

  As the batteries B1 and B2, for example, a secondary battery such as a lead storage battery, a nickel metal hydride battery, or a lithium ion battery, a large capacity capacitor such as an electric double layer capacitor, or the like can be used.

  The battery B2 and the battery B1, for example, can output the maximum power allowed for the electric load (inverter 14 and motor generator MG2) connected between the main positive bus MPL and the main negative bus MNL by using them simultaneously. The chargeable capacity is set so that As a result, traveling at maximum power is possible in EV (Electric Vehicle) traveling without using the engine.

  And if the electric power of battery B2 is consumed, by using engine 4 in addition to battery B1, it is possible to run at maximum power without using battery B2. Alternatively, a plurality of batteries B2 may be mounted so that when the power of the first battery is consumed, the EV driving can be continued by switching to the second and third batteries with a switch or the like.

  Inverter 14 is connected to main positive bus MPL and main negative bus MNL. Inverter 14 receives the boosted voltage from boost converters 12-1 and 12-2 and drives motor generator MG 1 to start engine 4, for example. Inverter 14 returns the electric power generated by motor generator MG1 by the power transmitted from engine 4 to boost converters 12-1 and 12-2. At this time, boost converters 12-1 and 12-2 are controlled by control device 30 so as to operate as voltage conversion circuits for converting voltage VH into voltages VB1 and VB2, respectively.

  Inverter 14 converts the DC voltage output from boost converters 12-1 and 12-2 into a three-phase AC voltage and outputs the same to motor generator MG2 that drives the wheels. Inverter 14 returns the electric power generated in motor generator MG2 to boost converters 12-1 and 12-2 along with regenerative braking. At this time, boost converters 12-1 and 12-2 are controlled by control device 30 to operate as voltage conversion circuits that convert voltage VH into voltages VB1 and VB2, respectively.

  Control device 30 receives torque command values of motor generators MG1 and MG2, motor current values and rotational speeds, values of voltages VB1, VB2 and VH, and a start signal. Control device 30 then outputs a boost instruction, a step-down instruction, and an operation prohibition instruction to boost converters 12-1 and 12-2.

  Further, control device 30 provides drive instruction for inverter 14 to convert DC voltage VH, which is the output of boost converters 12-1 and 12-2, into AC voltage for driving motor generator MG1, and motor generator MG1. A regenerative instruction for converting the AC voltage generated in step S1 to the DC voltage VH and returning it to the boost converters 12-1, 12-2 side is output.

  Similarly, control device 30 provides a drive instruction for converting a DC voltage into an AC voltage for driving motor generator MG2 for inverter 14 and a boost converter by converting the AC voltage generated by motor generator MG2 into a DC voltage. A regeneration instruction to return to the 12-1, 12-2 side is output.

  Boost converter 12-1 includes a chopper circuit 40-1, a positive bus LN1A, a negative bus LN1C, a wiring LN1B, and a smoothing capacitor C1. Chopper circuit 40-1 includes transistors Q1A and Q1B, diodes D1A and D1B, and an inductor L1. Transistor Q1B and diode D1B constitute an upper arm. Further, the lower arm is constituted by the transistor Q1A and the diode D1A.

  Positive bus LN1A has one end connected to the collector of transistor Q1B and the other end connected to main positive bus MPL. Negative bus LN1C has one end connected to negative electrode line NL1 and the other end connected to main negative bus MNL.

  Transistors Q1A and Q1B are connected in series between negative bus LN1C and positive bus LN1A. Specifically, the emitter of transistor Q1A is connected to negative bus LN1C, the emitter of transistor Q1B is connected to the collector of transistor Q1A, and the collector of transistor Q1B is connected to positive bus LN1A. In the lower arm, the diode D1A is connected in parallel to the transistor Q1A. In the upper arm, the diode D1B is connected in parallel to the transistor Q1B. The forward direction of the diode D1A is a direction from the bus LN1C toward the inductor L1. The forward direction of the diode D1B is a direction from the inductor L1 toward the bus LN1A. One end of the inductor L1 is connected to a connection node between the transistor Q1A and the transistor Q1B.

  Wiring LN1B is connected between positive electrode line PL1 and the other end of inductor L1. Smoothing capacitor C1 is connected between line LN1B and negative bus LN1C, and reduces the AC component included in the DC voltage between line LN1B and negative bus LN1C.

  Positive electrode line PL1 and negative electrode line NL1 are connected to the positive electrode and the negative electrode of battery B1, respectively, by system main relay SMR1.

  Chopper circuit 40-1 boosts DC power (drive power) received from positive line PL 1 and negative line NL 1 in accordance with drive signal PWC 1 provided from control device 30 to increase main positive bus MPL and main negative bus MNL. In addition, the voltages of the main positive bus MPL and the main negative bus MNL can be stepped down and supplied to the battery B1.

  Boost converter 12-2 includes a chopper circuit 40-2, a positive bus LN2A, a negative bus LN2C, a wiring LN2B, and a smoothing capacitor C2. Chopper circuit 40-2 includes transistors Q2A and Q2B, diodes D2A and D2B, and an inductor L2. Transistor Q2B and diode D2B constitute an upper arm. Further, the lower arm is constituted by the transistor Q2A and the diode D2A.

  Positive bus LN2A has one end connected to the collector of transistor Q2B and the other end connected to main positive bus MPL. Negative bus LN2C has one end connected to negative electrode line NL2 and the other end connected to main negative bus MNL.

  Transistors Q2A and Q2B are connected in series between negative bus LN2C and positive bus LN2A. Specifically, the emitter of transistor Q2A is connected to negative bus LN2C, the emitter of transistor Q2B is connected to the collector of transistor Q2A, and the collector of transistor Q2B is connected to positive bus LN2A. In the lower arm, the diode D2A is connected in parallel to the transistor Q2A. In the upper arm, the diode D2B is connected in parallel to the transistor Q2B. The forward direction of diode D2A is the direction from bus LN2C to inductor L2. The forward direction of the diode D2B is a direction from the inductor L2 toward the bus LN2A. Inductor L2 is connected to a connection node between transistor Q2A and transistor Q2B.

  The transistors Q1B, Q1A, Q2A, and Q2B may be power switching elements such as IGBTs (Insulated Gate Bipolar Transistors), power MOSFETs (Metal-Oxide Semiconductor Field-Effect Transistors), and the like.

  Line LN2B has one end connected to positive line PL2 and the other end connected to inductor L2. Smoothing capacitor C2 is connected between wiring LN2B and negative bus LN2C, and reduces an AC component included in a DC voltage between wiring LN2B and negative bus LN2C.

  Positive electrode line PL2 and negative electrode line NL2 are connected to the positive electrode and the negative electrode of battery B2, respectively, by system main relay SMR2.

  Chopper circuit 40-2 boosts DC power (drive power) received from positive line PL2 and negative line NL2 in accordance with drive signal PWC2 provided from control device 30 in FIG. It can be supplied to negative bus MNL, and the voltage of main positive bus MPL and main negative bus MNL can be stepped down and supplied to battery B2.

[Explanation of open circuit voltage and state of charge]
FIG. 2 is a diagram showing the relationship between the open circuit voltage (OCV) of the battery and the SOC.

  There is a correlation that the OCV of the battery increases as the SOC increases. For example, a lithium ion battery has a correlation as shown in FIG. 2, with OCV = 3.0V and SOC = 0%, OCV = 4.1V and SOC = 100%. This correlation is measured in advance and stored as a map. Then, the OCV can be measured by a voltage sensor, and the SOC can be estimated by referring to a map based on the OCV.

  However, since it is necessary to pass a current through the circuit during running or external charging, the open circuit voltage cannot be measured. When a current is passed through the circuit, the battery voltage is affected by the voltage increase / decrease due to the internal resistance and the voltage increase / decrease due to polarization.

  FIG. 3 is a waveform diagram for explaining temporal changes in the battery voltage during charging and the battery voltage during discharging.

  With reference to FIG. 3, a case will be described in which the battery is charged from time t1 to t2, the battery is not charged / discharged from time t2 to t3, and the battery is discharged after time t3.

  First, charging of the battery is started at time t1. The battery current IB indicates discharging in the positive direction and charging in the negative direction. As charging progresses, the open circuit voltage OCV increases as the state of charge SOC increases. This open circuit voltage OCV cannot be directly measured during charging. A closed circuit voltage CCV (Closed Circuit Voltage) can be detected as a battery voltage VB by the voltage sensor during charging. The closed circuit voltage CCV is obtained by adding the change ΔV1 due to the battery internal resistance and the change ΔV2 due to polarization to the open circuit voltage OCV.

  The change ΔV1 can be obtained by the product of the charging current I and the internal resistance R. Since the internal resistance R of the battery has temperature dependence, the battery temperature may be measured and corrected based on the temperature.

  The change ΔV2 tends to increase as the charging time increases. Accordingly, the change ΔV2 gradually increases from time t1 to t2.

  When charging is stopped at time t2, the change ΔV1 becomes zero because no current flows. However, the change ΔV2 does not immediately become zero, but approaches zero as time passes. Therefore, the battery voltage VB is higher than the open circuit voltage OCV for a while, and coincides with the open circuit voltage OCV after a certain amount of time has passed.

  At the time of discharge after time t3, the changes ΔV1 and ΔV2 appear in the reverse direction, that is, in the direction of decreasing the measurement voltage. Even during discharging, ΔV1 is the product of internal resistance and current, and that ΔV2 is caused by polarization and increases with time, and is similar to that during charging, and therefore the description will not be repeated. Although not shown, when the discharge stops and the battery current becomes zero, the voltage increases for the change ΔV1, but the change ΔV2 does not immediately become zero, and a voltage lower than the open circuit voltage OCV is measured for a while. The After that, when a certain amount of time elapses, the measured voltage becomes equal to the open circuit voltage OCV.

  The voltage change ΔV2 caused by the polarization changes depending on the time from the start of charging and discharging. Therefore, as will be described later with reference to battery model MB in FIG. 4, in the SOC estimation process applied when the vehicle is traveling, a voltage change ΔV2 due to polarization ΔV2 (in accordance with the traveling pattern in which the regenerative and powering charge / discharge cycles are repeated. In FIG. 4, Vdyn) is determined, and using this, the open circuit voltage OCV is estimated from the closed circuit voltage CCV, and the SOC is finally estimated based on the estimated open circuit voltage OCV.

  That is, the voltage change ΔV2 (Vdyn in FIG. 4) is calculated based on a value that is matched during traveling in which charging and discharging are repeated.

  When it is known that only charging or discharging is performed, control device 30 mainly estimates the SOC by accumulating the charging or discharging current with respect to the initial value of SOC. On the other hand, when there is a possibility that the charging and discharging cycles are frequently repeated as in traveling, the estimation is performed mainly using the estimation OCV method which is a different estimation method. In this estimated OCV method, not only current integration, but also error accumulation is prevented when a battery usage method in which charging and discharging are repeated frequently reflecting the battery voltage and the internal resistance of the battery is performed. It is out.

  The switching of the SOC estimation process performed by the control device 30 will be described with reference to a block diagram.

FIG. 4 is a block diagram showing the configuration of the SOC estimation process executed by control device 30.
Referring to FIG. 4, control device 30 detects a change in SOC by applying a battery model MA that detects a change in SOC based on current integration, and a correction that uses a detected voltage value in addition to current integration. And battery model MB.

  The charge / discharge current of the battery is detected by the current detection unit 110. Further, the battery voltage at that time is detected by the voltage detector 112. The current detection unit 110 corresponds to the current sensors 11-1 and 11-2 in FIG. The voltage detection unit 112 corresponds to the voltage sensors 10-1 and 10-2 in FIG.

  During normal running (HV running) of a vehicle using both an engine and a motor, the SOC change amount ΔSOCv calculated by the ΔSOCv calculation unit 142 is selected by the selection command unit 146 by estimating the SOC using the battery model MB. The selection setting of the selection unit 136 is set to the B side. This amount of change ΔSOCv is integrated by SOC integrating section 148 and an estimated SOC value is output.

  The charge / discharge current value detected by the current detection unit 110 is integrated by the pseudo SOC estimation unit 114 and added to the previously determined initial value of the SOC of the battery to estimate the pseudo SOC which is a temporary value of the SOC. The The initial value of the SOC is set to the SOC upper limit value when fully charged immediately after external charging. When external charging is not performed, the estimated SOC value stored in the nonvolatile memory inside the control device 30 at the end of the previous use can be read and used as the initial value of the SOC.

  Based on the pseudo SOC thus obtained, the electromotive force estimation unit 116 estimates the battery voltage corresponding to the pseudo SOC. The battery voltage estimated by the electromotive force estimation unit 116 is an estimated value Voc of the open circuit voltage of the battery. Such an open circuit voltage Voc is estimated as an open circuit voltage Voc corresponding to the pseudo SOC given from the pseudo SOC estimation unit 114 by obtaining a map of the SOC and the open circuit voltage as shown in FIG. be able to.

Further, the voltage fluctuation estimation unit 118 estimates the voltage fluctuation due to the internal resistance of the battery from the charge / discharge current value of the battery detected by the current detection unit 110. The voltage fluctuation estimation unit 118 estimates the fluctuation of the battery voltage due to the internal resistance by the following equation.
Vr = −r × IB
Here, r represents the internal resistance, and IB represents the battery current value (discharge is positive). Vr is a voltage fluctuation due to an internal resistance estimated by the voltage fluctuation estimation unit 118. The internal resistance r of the battery is determined for each battery in advance. The current value IB is a charge / discharge current value detected by the current detection unit 110. This voltage variation Vr corresponds to ΔV1 in FIG.

  Further, the dynamic voltage fluctuation estimation unit 120 estimates the fluctuation of the battery voltage based on the change in the charge / discharge current of the battery. This dynamic voltage fluctuation is caused by the polarization of the battery. The dynamic voltage fluctuation estimation unit 120 gives a dynamic voltage fluctuation Vdyn of the battery determined based on a usage pattern in which charging and discharging are frequently repeated. This voltage variation Vdyn corresponds to ΔV2 in FIG. For example, it is possible to measure the polarization voltage at a set time suitable for traveling with respect to the battery current IB and define and use the voltage fluctuation Vdyn as a map for the current.

  Next, the output values of the electromotive force estimation unit 116, voltage fluctuation estimation unit 118, and dynamic voltage fluctuation estimation unit 120 described above are added by an adder 122 to obtain an estimated voltage Vest that is an estimated value of the battery voltage. That is, Vest = Voc + Vr + Vdyn.

  The pseudo SOC estimation unit 114, the electromotive force estimation unit 116, the voltage variation estimation unit 118, the dynamic voltage variation estimation unit 120, and the adder 122 described above constitute a battery model MB.

The estimated voltage Vest of the battery estimated by the battery model MB described above is compared with the actual measured voltage Vmes of the battery detected by the voltage detection unit 112 by the comparator 124, and the difference is input to the SOC correction amount calculation unit 126. Entered. The SOC correction amount calculation unit 126 and the adder 128 perform the calculation of the following expression, and the estimated value SOCv of the battery SOC is calculated.
SOCv = SOCp + Kp × (Vmes−Vest) + Ki × ∫ (Vmes−Vest) dt
Here, SOCp indicates pseudo SOC, and Kp and Ki indicate coefficients. In the above equation, pseudo SOC (SOCp) is an output value of pseudo SOC estimation unit 114. Further, in the SOC correction amount calculation unit 126, a component proportional to a difference (Vmes−Vest) between the estimated voltage Vest and the measured voltage Vmes obtained by the second and third terms of the above equation, that is, the comparator 124, and this The component proportional to the integral value of the difference is calculated. Here, the coefficients Kp and Ki are previously determined from the battery characteristics. Each of the components calculated by the SOC correction amount calculation unit 126 is added to the output value SOCp of the pseudo SOC estimation unit 114 by the adder 128 as shown in the above equation. Thereby, an estimated value of the SOC of the battery can be obtained.

  As described above, the battery electromotive force of the battery is estimated from the pseudo SOC by the battery model MB mainly used at the time of HV traveling, and the fluctuation due to the internal resistance of the battery voltage and the dynamic voltage fluctuation due to the change of the charge / discharge current are And estimate the battery voltage as the sum of these. That is, the battery voltage Vest is estimated from the battery model in consideration of the fluctuation of the state of the battery together with the pseudo SOC. Next, the pseudo SOC is corrected so that the estimated voltage Vest is equal to the actually measured battery voltage Vmes, and the battery SOC is estimated.

  As described above, if the battery model MB is used, the pseudo SOC is corrected so that the estimated voltage Vest is equal to the actually measured battery voltage Vmes. Even if a large error is included, it is possible to quickly converge to an accurate estimated SOC value.

  On the other hand, when only charging or discharging is performed, for example, when plug-in charging or pre-boarding air conditioning is performed, the SOC estimation result SOCi using the battery model MA is used. Then, the selection setting of the selection unit 136 is set to the A side so that the change amount ΔSOCi of SOCi is used for the integration of the SOC. The selection command unit determines which one of ΔSOCi and ΔSOCv should be used for SOC integration, and issues a command to selection unit 136.

  In the battery model MA, the initial SOC detection unit 132 determines the initial SOC based on the battery voltage detected by the voltage detection unit 112. As described with reference to FIG. 3, since the influence of polarization remains immediately after the charging or discharging is stopped, the SOC previously estimated by the battery models MA, MB, etc. is taken over. FIG. 2 shows that the battery voltage VB measured when the current zero control is executed is equal to the battery electromotive force after the time when the current is almost zero continues for a while after the charging or discharging is stopped. Obtain the SOC from the map.

  Then, the charging / discharging current value detected by the current detection unit 110 is integrated by the current integration processing unit 134 and added to the initial value of the SOC of the battery obtained by the initial SOC detection unit 132, and the SOC is estimated. .

  When plug-in charging or pre-ride air conditioning is performed, either charging or discharging is performed, and a large current such as a motor current during vehicle travel does not flow. Therefore, since the SOC estimation error is difficult to accumulate, the SOC may be estimated by such a current integration method. As a result, it is not affected by the increase in voltage fluctuation due to polarization, so that plug-in charging can be performed accurately up to the SOC management upper limit value. In addition, the power used from the battery in the air conditioning before boarding can be reliably returned by plug-in charging. For this reason, it is advantageous in extending the cruising distance of EV traveling.

  In the case of plug-in charging or air conditioning before boarding, only charging or discharging is performed, and a large current such as a motor current during vehicle travel does not flow. The current detection unit 110 may be divided into detection units having different ranges, such as current detection units 110A and 110B (not shown). When the battery model MA is used, the high-resolution current detection unit 110A is used in the low measurement range, and when the battery model MB is used, the low-resolution current detection unit in the measurement range capable of measuring a large current. The use of the current detection units 110A and 110B may be switched in conjunction with the selection setting of the selection unit 136 so that 110B is used. In FIG. 1, instead of the current sensors 11-1 and 11-2, high accuracy sensors 11-1 A and 11-2 </ b> A (not shown) can be measured at the same location, but a larger current can be measured. The sensors 11-1B and 11-2B (not shown) may be provided and used properly. By doing so, more accurate SOC estimation can be executed.

  The selection unit 136 may be switched based on whether a charging plug is inserted and charging is being performed, whether the engine is stopped, or the like. However, for example, even during EV traveling with the engine stopped, the secondary battery may be charged by regenerative braking during deceleration or downhill traveling. Further, even during plug-in charging, if an electric load such as a light or an air conditioner is operated, the secondary battery may be discharged. Therefore, since the frequency of repeating charging and discharging can be changed variously depending on the road on which the vehicle is driven and the operation of the driver, the accuracy is improved by frequently switching the selection unit 136 according to the state of the vehicle.

  FIG. 5 is a flowchart for explaining the switching process related to the selection command unit 146 of FIG.

Referring to FIGS. 4 and 5, ΔSOCv and ΔSOCi are first calculated by ΔSOCv calculation unit 142 and ΔSOCi calculation unit 144 in step S 1 and stored in selection command unit 146. Next, at step S2, the absolute value integrated value Σ | ΔSOCv | and the integrated value ΣΔSOCv during the time period T are calculated by the selection command unit 146, and the switching determination parameter K is calculated by the following equation at step S3.
K = | ΣΔSOCv | / Σ | ΔSOCv |
This parameter K indicates the frequency of charge / discharge repetition. Although ΔSOCv is used in steps S2 and S3, the parameter K may be obtained using ΔSOCi instead.

FIG. 6 is a diagram for explaining a change in the switching determination parameter K.
Referring to FIG. 6, the horizontal axis indicates time. The waveforms of SOC, ΔSOC, ΣΔSOC per period T, and parameter K are shown in order from the top.

  The period TA is an example when the SOC repeatedly increases and decreases. In this case, since ΔSOC alternately takes a positive value and a negative value, ΣΔSOC per period T initially takes a positive value for a moment but becomes zero all the time thereafter. At this time, since ΣΔSOC corresponding to the numerator of the parameter K becomes 0, the parameter K also becomes 0.

  The period TB is an example when the SOC monotonously increases. In this case, since ΔSOC takes a positive value, ΣΔSOC per period T takes a positive value. At this time, ΣΔSOC corresponding to the numerator of the parameter K and Σ | ΔSOC | corresponding to the denominator are the same, so the parameter K becomes 1.

  The period TC is an example when the SOC monotonously decreases. In this case, since ΔSOC takes a negative value, ΣΔSOC per period T takes a negative value. At this time, since ΣΔSOC corresponding to the numerator of parameter K and Σ | ΔSOC | corresponding to the denominator have the same magnitude and different signs, Σ | ΔSOCv | / ΣΔSOCv is −1. Since the parameter K is an absolute value of this value, the parameter K is 1.

  In FIG. 6, a simple waveform example has been described for easy understanding. As described above, the parameter K takes a value between 0 and 1, and the closer to 0, the more repeatedly charging / discharging is indicated, and the closer to 1, the charging or discharging is monotonically continuous.

  Referring to FIGS. 4 and 5 again, when the calculation of parameter K is completed in step S3, it is determined in step S4 whether or not parameter K is larger than threshold value Kt.

  If the parameter K is larger than the threshold value Kt in step S4, the process proceeds to step S5. That is, the selection unit 136 selects the route A, and the SOC accumulation unit 148 adds ΔSOCi to the current value and updates the estimated SOC value.

  If the parameter K is not greater than the threshold value Kt in step S4, the process proceeds to step S6. That is, the selection unit 136 selects the route B, and the SOC integration unit 148 adds ΔSOCv to the current value and updates the estimated SOC value.

  When the update of the SOC estimated value is completed in either step S5 or S6, the process proceeds to step S7, and the control returns to the main routine.

  Note that the unit time for calculating ΔSOC, the period T for calculating ΣΔSOC, and the determination threshold value Kt are adapted by experiments and simulations so that the estimation accuracy of SOC is improved.

  FIG. 7 is a diagram showing an example of SOC change when EV travel and HV travel after plug-in charging are executed.

Referring to FIG. 7, plug-in charging is performed at times t1 to t2. At this time, the SOC increases monotonously. The parameter K takes a value close to 1 and is larger than the threshold value Kt. For this reason, ΔSOCi is used in the calculation of the SOC from time t1 to time t2 as in the following equation.
SOC (t + Δt) = SOC (t) + ΔSOCi
From time t3 to t4, EV traveling is executed. Since the charged battery power is used, the SOC decreases. However, since the regenerative brake is activated during braking or downhill, and the battery is charged at that time, the parameter K decreases from near 1 to 0. In the example of FIG. 7, since charging and discharging are not repeated so frequently, the parameter K does not fall below the threshold value Kt. For this reason, ΔSOCi is used to calculate the SOC at times t3 to t4 in the same manner as described above.

After time t4, the power charged in the secondary battery is consumed by external charging, and HV traveling using the engine is executed. After a while since the start of the HV traveling, the parameter K becomes smaller than the threshold value Kt at time t5, so that ΔSOCv is used for calculating the SOC after time t5 as shown in the following equation.
SOC (t + Δt) = SOC (t) + ΔSOCv
Note that when the integration is started by replacing ΔSOCv and ΔSOCi, a filter process such as a gradual change may be applied so that the estimated SOC value gradually changes.

  As described above, in the present embodiment, the SOC estimation method is switched in the EV mode of the plug-in hybrid vehicle or the hybrid vehicle or the external charging mode of the plug-in hybrid vehicle. For this purpose, both the estimated SOC value by the estimation method using voltage correction and the estimated SOC value by the estimation method using only current integration are calculated.

  Then, when discharge is executed as a result in a predetermined period, an estimation method using only current integration is used when the proportion of charge in that period is smaller than the threshold value. Similarly, when charging is executed as a result in a predetermined period, an estimation method using only current integration is used when the proportion of discharge in that period is smaller than the threshold value. For example, the parameter K described with reference to FIG. 6 can be used as a parameter for evaluating the ratio of discharging during charging and the ratio of charging during discharging.

Finally, the present embodiment will be summarized with reference to FIG.
The power supply device for a vehicle shown in the present embodiment estimates charge and discharge batteries B1 and B2, current sensors 11-1 and 11-2 that detect battery current, and the state of charge of the battery. And a control device 30 that controls charging / discharging of the battery based on the charged state. Control device 30 calculates first and second estimated values SOCv and SOCi by the first and second estimation methods in a predetermined period, respectively, and calculates the charge amount to the battery and the discharge amount from the battery in the predetermined period. Observe and update the state of charge SOC of the battery based on one of the first and second estimated values based on the observation result. The first estimation method is a method for estimating an open circuit voltage of a battery and determining a first estimated value based on a value obtained by correcting the open circuit voltage based on polarization. The second estimation method is an estimation method different from the first estimation method, and is a method for determining the second estimated value based on the result of integrating the current detected by the current sensor.

  Preferably, when the discharge is performed as a total within a predetermined period, control device 30 has a first evaluation value indicating a degree of occurrence of charging in the predetermined period exceeding first threshold value Kt. The battery state of charge is updated based on the first estimated value, and the state of charge of the battery is updated based on the second estimated value when the first evaluation value does not exceed the first threshold value. For example, the parameter K described with reference to FIG. 6 increases and approaches 1 when the frequency of charging during discharging is low or when the frequency of discharging during charging is low. Therefore, when 1-K is used as the first evaluation value, the first threshold value can be set to 1-Kt.

  Preferably, when charging is performed as a total within a predetermined period, control device 30 determines that when the second evaluation value indicating the degree of occurrence of discharge in the predetermined period exceeds the second threshold value. The state of charge of the battery is updated based on the first estimated value, and the state of charge of the battery is updated based on the second estimated value when the second evaluation value does not exceed the second threshold value. For example, if 1-K is used as the second evaluation value, the second threshold value can be set to 1-Kt.

  Preferably, vehicle 1 is configured to be capable of external charging in which battery B1 is charged from the outside of the vehicle. The case where charging is performed as a total within a predetermined period includes the time when external charging is performed.

  Preferably, vehicle 1 is equipped with engine 4 and motor generator MG2 capable of executing a power running operation and a regenerative operation. The case where discharge is performed as a total within a predetermined period includes the time when the vehicle is driven by motor generator MG2 with engine 4 stopped.

  In the present embodiment, an example of a plug-in hybrid vehicle has been described. However, the SOC estimation method disclosed in the present embodiment is applicable to various vehicles other than plug-in hybrid vehicles such as electric vehicles and fuels. It can also be applied to battery cars.

  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.

  1 vehicle, 3 power split mechanism, 4 engine, 6 charger, 8 commercial power supply, 13 voltage sensor, 14 inverter, 30 control device, 110, 110A, 110B current detection unit, 112 voltage detection unit, 114 pseudo SOC estimation unit, 116 electromotive force estimation unit, 118 voltage variation estimation unit, 120 dynamic voltage variation estimation unit, 122,128 adder, 124 comparator, 126 SOC correction amount calculation unit, 132 initial SOC detection unit, 134 current integration processing unit, 136 Selection unit, 142 ΔSOCv calculation unit, 144 ΔSOCi calculation unit, 146 selection command unit, 148 SOC integration unit, B1, B2 battery, C1, C2, CH smoothing capacitor, D1A, D1B, D2A, D2B diode, L1, L2 inductor, LN1A, LN2A Positive bus, LN1B, LN2B wiring, L N1C, LN2C negative bus, MA, MB battery model, MG1, MG2 motor generator, MNL main negative bus, MPL main positive bus, NL1, NL2 negative wire, PL1, PL2 positive wire, Q1A, Q1B, Q2A, Q2B transistor, SMR1 , SMR2 system main relay.

Claims (3)

A secondary battery capable of charging and discharging;
A current sensor for detecting a current of the secondary battery;
A controller that estimates the state of charge of the secondary battery and controls charging and discharging of the secondary battery based on the estimated state of charge;
The control device calculates first and second values by a first estimation method and a second estimation method in a predetermined period, respectively.
The first estimation method is a method of estimating an open circuit voltage of the secondary battery and determining the first value based on a value obtained by correcting the open circuit voltage based on polarization.
The second estimation method is an estimation method different from the first estimation method, and is a method of determining the second value based on a result obtained by integrating the currents detected by the current sensor,
In a period shorter than the predetermined period, the control device calculates an absolute value integrated value Σ | ΔSOC | of the increase ΔSOC of the state of charge calculated by either the first estimation method or the second estimation method. An integrated value ΣΔSOC is calculated, one of the first and second values is selected based on whether | ΣΔSOC | / Σ | ΔSOC | exceeds a threshold value, and the selected value is added. To update the estimated value of the state of charge of the secondary battery ,
The control device selects the second value when | ΣΔSOC | / Σ | ΔSOC | is larger than a threshold value, and when | ΣΔSOC | / Σ | ΔSOC | A vehicle power supply that selects the value of . The vehicle is configured to allow external charging to charge the secondary battery from outside the vehicle,
The power supply device for a vehicle according to claim 1, wherein when the charging is performed as a total within the predetermined period, the external charging is performed. The vehicle is equipped with an engine and an electric motor capable of executing a power running operation and a regenerative operation,
2. The vehicle power supply device according to claim 1, wherein when the discharge is performed as a total within the predetermined period, the vehicle is driven by the electric motor while the engine is stopped.

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