JP2008175556A - Device and method for detecting internal resistance of secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device and method capable of accurately detecting the internal resistance of a secondary battery with a simplified device constitution. <P>SOLUTION: A battery 10 is a secondary battery and each one is divided into n (n is a natural number) battery blocks B1-Bn, which are composed of several unit batteries connected in series, respectively. A battery monitoring part 30 receives battery voltage Vb1-Vbn of the battery blocks B1-Bn from a voltage sensor 12, and receives battery current Ib from a current sensor 14. Further, the battery monitoring part 30 receives a career frequency fc from a MGECU50 to turn on/off the switching element of the boosting converter inside of a power control unit 20. The battery monitoring part 30 acquires the frequency characteristics of the impedance of the battery blocks B1-Bn by an alternating current method based on these input signals, and calculates the internal resistance values R1-Rn of the battery blocks B1-Bn based on the acquired frequency characteristics. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a technique for detecting an internal resistance value of a secondary battery, and particularly to a technique for detecting an internal resistance value of a secondary battery included in a power supply device for driving an electric load.

  It is known that the state of deterioration of a secondary battery has a close relationship with its internal resistance value. Therefore, in order to accurately grasp the state of the secondary battery, it is required to detect the internal resistance value accurately and quickly.

For example, Japanese Patent Laying-Open No. 2004-28663 (Patent Document 1) discloses an electronic control circuit having an internal resistance measurement circuit that measures an internal resistance value of a battery by an alternating current method. According to this, since the electronic control circuit is configured to measure the frequency of the alternating current for measuring the battery internal resistance at a plurality of frequencies, it is accurately determined that the internal resistance varies depending on the frequency depending on the capacitor included in the battery. Can be measured.
JP 2004-28663 A

  In the above-mentioned Japanese Patent Application Laid-Open No. 2004-28663 (Patent Document 1), the alternating current method applied to the measurement of the internal resistance value of the battery is also called the alternating current impedance method, and as is well known, an alternating current signal is added to the measurement object. This is a method of measuring the AC resistance (impedance) of the measurement object when the frequency is changed. According to the alternating current method, more accurate measurement is possible as compared with the so-called direct current method in which the resistance value of the measurement object is calculated from the voltage and current between the terminals of the measurement object in direct current.

  However, in order to realize the AC method in the internal resistance measurement circuit in the above-mentioned Japanese Patent Application Laid-Open No. 2004-28663 (Patent Document 1), the circuit is configured to generate AC signals having a plurality of frequencies. An oscillating oscillator will inevitably be installed. As a result, there arises a problem that the internal resistance measurement circuit becomes large and expensive.

  Further, by mounting an oscillator inside the internal resistance measurement circuit, the oscillator becomes a source of noise, and there is a possibility that a system that operates using a battery as a power source malfunctions.

  Therefore, the present invention has been made to solve such a problem, and an object of the present invention is to provide a detection device capable of accurately detecting the internal resistance value of the secondary battery with a simple device configuration and the detection thereof. Is to provide a method.

  According to this invention, the internal resistance detection device of the secondary battery is a detection device that detects the internal resistance value of the secondary battery included in the power supply device for driving the electric load. The power supply device includes a secondary battery, a drive circuit that receives electric power from the secondary battery and drives an electric load, and a switching element, and a DC voltage is generated between the secondary battery and the drive circuit by a switching operation of the switching element. And a control device for controlling the voltage converter by changing a switching frequency for turning on / off the switching element. The detection device includes a current voltage acquisition unit that acquires a current value and a voltage value of the secondary battery, a switching frequency acquisition unit that acquires a switching frequency, and a secondary voltage based on the acquired current value, voltage value, and switching frequency. Internal resistance value calculating means for calculating the internal resistance value of the battery.

  According to the internal resistance detection device for a secondary battery described above, the internal resistance value of the secondary battery can be accurately calculated by an AC method without using an oscillator for applying an AC signal to the secondary battery. As a result, it is possible to accurately grasp the deterioration state of the secondary battery while maintaining the stability of the drive control of the electric load with a simple and inexpensive apparatus configuration.

  Preferably, the internal resistance value calculating means acquires the frequency characteristic of the impedance of the secondary battery based on the acquired current value, voltage value and switching frequency, and based on the acquired frequency characteristic of the impedance Calculate the internal resistance of the battery.

  According to the internal resistance detection device for a secondary battery, the frequency characteristics of the impedance of the secondary battery can be obtained without using an oscillator for giving an AC signal to the secondary battery. The internal resistance value can be calculated accurately.

  According to this invention, the detection method of the internal resistance value of the secondary battery is a detection method of detecting the internal resistance value of the secondary battery included in the power supply device for driving the electric load. The power supply device includes a secondary battery, a drive circuit that receives electric power from the secondary battery and drives an electric load, and a switching element, and a DC voltage is generated between the secondary battery and the drive circuit by a switching operation of the switching element. And a control device for controlling the voltage converter by changing a switching frequency for turning on / off the switching element. The detection method includes a current voltage acquisition step for acquiring a current value and a voltage value of a secondary battery, a switching frequency acquisition step for acquiring a switching frequency, and a secondary voltage based on the acquired current value, voltage value, and switching frequency. An internal resistance value calculating step for calculating an internal resistance value of the battery.

  According to the method for detecting the internal resistance value of the secondary battery, the internal resistance value of the secondary battery can be accurately calculated by the AC method without using an oscillator for giving an AC signal to the secondary battery. . As a result, it is possible to accurately grasp the deterioration state of the secondary battery while maintaining the stability of the drive control of the electric load with a simple and inexpensive apparatus configuration.

  Preferably, the internal resistance value calculating step acquires a frequency characteristic of the impedance of the secondary battery based on the acquired current value, voltage value and switching frequency, and based on the acquired frequency characteristic of the impedance, Calculating an internal resistance value of the secondary battery.

  According to the above-described method for detecting the internal resistance value of the secondary battery, the frequency characteristic of the impedance of the secondary battery can be obtained without using an oscillator for applying an AC signal to the secondary battery. The internal resistance value of the battery can be calculated accurately.

  According to the present invention, the internal resistance value of the secondary battery can be accurately detected with a simple device configuration.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same reference numerals indicate the same or corresponding parts.

  FIG. 1 is a schematic block diagram showing a configuration of a motor drive device to which an internal resistance detection device for a secondary battery according to an embodiment of the present invention is applied.

  Referring to FIG. 1, the motor drive device includes a battery 10, a power control unit (PCU) 20 that controls AC motor M <b> 1, voltage sensor 12, current sensor 14, and temperature sensor 16. The battery monitoring unit 30, the HVECU (Electric Control Unit) 40, and the MGECU 50 are provided.

  AC motor M1 is a drive motor for generating torque for driving drive wheels of a hybrid vehicle or an electric vehicle. The AC motor M1 is a motor that has a function as a generator driven by an engine (not shown) and that operates as an electric motor for the engine and can start the engine, for example. .

  The battery 10 is a chargeable / dischargeable secondary battery, and is made of, for example, nickel metal hydride or lithium ions. The battery 10 is an assembled battery formed by connecting a plurality of unit cells in series, and each of n (n is a natural number) battery blocks B1 to Bn each including several units connected in series. It is divided.

  The power control unit 20 is a drive system that drives the AC motor M1, and includes an inverter that drives the AC motor M1 and a boost converter (both not shown). When the DC power is supplied from the battery 10 through the boost converter, the inverter converts the DC power into AC power and drives the AC motor M1. Thereby, AC motor M1 generates torque for driving the drive wheels.

  Voltage sensor 12 detects DC voltage VB output from battery 10 and outputs the detected DC voltage VB to MGECU 50. The voltage sensor 12 detects battery voltages Vb1 to Vbn of the battery blocks B1 to Bn, respectively, and outputs the detected battery voltages Vb1 to Vbn to the battery monitoring unit 30. DC voltage VB indicates a voltage across terminals of battery 10 as a whole, and corresponds to the sum of battery voltages Vb1 to Vbn.

  Current sensor 14 detects battery current Ib flowing through n battery blocks B <b> 1 to Bn connected in series, and outputs the detected battery current Ib to battery monitoring unit 30. The temperature sensor 16 detects the battery temperature Tb of the battery blocks B <b> 1 to Bn and outputs the detected battery temperature Tb to the battery monitoring unit 30.

  When battery monitoring unit 30 receives battery voltages Vb1 to Vbn from voltage sensor 12, receives battery current Ib from current sensor 14, and receives battery temperature Tb from temperature sensor 16, battery monitoring unit 30 determines the SOC of battery 10 based on these input signals. Is estimated. As an example, the SOC of the battery 10 is estimated based on the integrated value of the battery current Ib. In addition to the method based on the integrated value of the battery current Ib, various known methods can be employed as the SOC estimation method. Battery monitoring unit 30 outputs the estimated SOC of battery 10 to HVECU 40 together with signals indicating the state of battery 10 (battery voltages Vb1 to Vbn, battery current Ib, and battery temperature Tb).

  Further, when battery monitoring unit 30 receives battery voltages Vb1 to Vbn from voltage sensor 12, receives battery current Ib from current sensor 14, and receives carrier frequency fc in power control unit 20 from MGECU 50, battery monitoring unit 30 is based on these input signals. Then, the internal resistance values R1 to Rn of the battery blocks B1 to Bn are detected by a method described later. Battery monitoring unit 30 outputs the detected internal resistance values R1 to Rn to HVECU 40.

  When the HVECU 40 receives the SOC of the battery 10 together with the state of the battery 10 from the battery monitoring unit 30, the HVECU 40 calculates the driving force necessary for traveling of the vehicle based on these input information and the request output from the driver, The AC motor M1 and the engine (not shown) are driven and controlled so that the calculated driving force is obtained.

  Specifically, the HVECU 40 calculates the driver's required output based on the accelerator depression amount, the shift position, and the like. Further, a charge request value for the battery 10 is calculated based on the SOC of the battery 10. Then, the HVECU 40 calculates the driving force necessary for traveling of the vehicle from the driver's requested output and the charging request value of the battery 10, and the engine and AC motor M1 rotation speeds so as to obtain the calculated driving force. And control amount such as torque distribution.

  Then, HVECU 40 outputs various required values to MGECU 50 and engine ECU (not shown) based on the determined control amount. To MGECU 50, torque command value TR and motor rotation speed MRN determined from the required output (rotation speed × torque) of AC motor M1 are output. The MGECU 50 performs current control for making the actual motor drive current coincide with the current command based on the current command of the motor drive current converted from the torque command value TR.

  Further, when receiving the internal resistance values R1 to Rn for each of the battery blocks B1 to Bn from the battery monitoring unit 30, the HVECU 40 determines a deterioration state for each of the battery blocks B1 to Bn based on the internal resistance values R1 to Rn. When any of the internal resistance values R1 to Rn exceeds a predetermined threshold value, the HVECU 40 generates a battery related warning signal and outputs it to a display unit (not shown).

[Drive control of AC motor M1]
FIG. 2 is a schematic block diagram for explaining the drive control of AC motor M1 in MGECU 50 and the operation of detecting internal resistance values R1 to Rn in battery monitoring unit 30.

  Referring to FIG. 2, power control unit 20 includes a boost converter 22, a capacitor C <b> 2, an inverter 24, a voltage sensor 23, and a current sensor 28.

  Boost converter 22 includes a reactor L1, IGBTs (Insulated Gate Bipolar Transistor) elements Q1, Q2, and diodes D1, D2.

  Reactor L1 has one end connected to the power supply line of battery 10, and the other end connected to an intermediate point between IGBT element Q1 and IGBT element Q2, that is, between the emitter of IGBT element Q1 and the collector of IGBT element Q2. .

  IGBT elements Q1, Q2 are connected in series between the power supply line and the earth line. The collector of IGBT element Q1 is connected to the power supply line, and the emitter of IGBT element Q2 is connected to the ground line. In addition, diodes D1 and D2 that allow current to flow from the emitter side to the collector side are arranged between the collectors and emitters of the IGBT elements Q1 and Q2, respectively.

  Inverter 24 includes a U-phase arm 25, a V-phase arm 26, and a W-phase arm 27. U-phase arm 25, V-phase arm 26, and W-phase arm 27 are provided in parallel between the power supply line and the earth line.

  U-phase arm 25 includes IGBT elements Q3 and Q4 connected in series. V-phase arm 26 includes IGBT elements Q5 and Q6 connected in series. W-phase arm 27 includes IGBT elements Q7 and Q8 connected in series. Further, diodes D3 to D8 that flow current from the emitter side to the collector side are connected between the collectors and emitters of the IGBT elements Q3 to Q8, respectively.

  An intermediate point of each phase arm is connected to each phase end of each phase coil of AC motor M1. In other words, AC motor M1 is a three-phase permanent magnet motor, and is configured such that one end of three coils of U, V, and W phases is commonly connected to the midpoint. The other end of the U-phase coil is at the intermediate point between the IGBT elements Q3 and Q4, the other end of the V-phase coil is at the intermediate point between the IGBT elements Q5 and Q6, and the other end of the W-phase coil is at the intermediate point between the IGBT elements Q7 and Q8. Each is connected.

  Switching elements included in boost converter 22 and inverter 24 are not limited to IGBT elements Q1 to Q8, but may be constituted by other power elements such as MOSFETs.

  Boost converter 22 boosts the DC voltage supplied from battery 10 and supplies the boosted voltage to capacitor C2. More specifically, when boost converter 22 receives signal PWMC from MGECU 50, boost converter 22 boosts the DC voltage according to the period during which IGBT element Q2 is turned on by signal PWMC and supplies it to capacitor C2.

  Further, when boost converter 22 receives signal PWMC from MGECU 30, it steps down DC voltage supplied from inverter 24 via capacitor C2 and charges battery 10.

  Capacitor C <b> 2 smoothes the DC voltage from boost converter 22 and supplies the smoothed DC voltage to inverter 24. Voltage sensor 23 detects the voltage across capacitor C2, that is, output voltage Vm of boost converter 22 (corresponding to the input voltage to inverter 24; the same applies hereinafter), and outputs the detected output voltage Vm to MGECU 50. To do.

  When the DC voltage is supplied from the capacitor C2, the inverter 24 converts the DC voltage into an AC voltage based on the signal PWMI from the MGECU 50 and drives the AC motor M1. Thereby, AC motor M1 is driven to generate the required torque specified by torque command value TR.

  Further, the inverter 24 converts the AC voltage generated by the AC motor M1 into a DC voltage based on the signal PWMI from the MGECU 50 at the time of regenerative braking of the hybrid vehicle or electric vehicle on which the motor driving device is mounted, and the converted DC voltage Is supplied to the boost converter 22 via the capacitor C2.

  Note that regenerative braking here refers to braking with regenerative power generation when the driver operating the hybrid vehicle or electric vehicle performs footbrake operation, or while not operating the footbrake, Including decelerating (or stopping acceleration) the vehicle while regenerating power.

  Current sensor 28 detects motor current MCRT flowing through AC motor M1, and outputs the detected motor current MCRT to MGECU 50.

  MGECU 50 receives torque command value TR and motor rotational speed MRN from HVECU 40, receives output voltage Vm from voltage sensor 23, receives DC voltage VB from voltage sensor 12, and receives motor current MCRT from current sensor 28. Based on output voltage Vm, torque command value TR and motor current MCRT, MGECU 50 generates signal PWMI for switching control of IGBT elements Q3 to Q8 of inverter 24 when inverter 24 drives AC motor M1. Then, the generated signal PWMI is output to the inverter 24.

  Further, when inverter 24 drives AC motor M1, MGECU 50 performs switching control of IGBT elements Q1, Q2 of boost converter 22 based on DC voltage VB, output voltage Vm, torque command value TR, and motor rotation speed MRN. Signal PWMC is generated and output to boost converter 22.

  Further, MGECU 50 adjusts carrier frequency fc for turning on / off IGBT elements Q1, Q2 of boost converter 22 by a method described later. At this time, MGECU 50 outputs adjusted carrier frequency fc to battery monitoring unit 30.

[Detection operation of internal resistance of secondary battery]
When battery monitoring unit 30 receives battery voltages Vb1 to Vbn from voltage sensor 12 and battery current Ib from current sensor 14, battery monitoring unit 30 determines internal resistance values R1 to Rn for battery blocks B1 to Bn based on these input signals. calculate.

  Specifically, the battery monitoring unit 30 calculates the internal resistance values R1 to Rn of the battery blocks B1 to Bn by a so-called AC method. The AC method is also called the AC impedance method, and measures the impedance of the measurement object based on the voltage between the terminals of the measurement object and the current flowing through the measurement object when an AC signal is applied to the measurement object and the frequency is changed. Is the method. According to this method, the resistance value can be measured more accurately than the so-called DC method, in which the resistance value of the measurement target is calculated from the voltage and current between the terminals of the measurement target in direct current.

FIG. 3 is a schematic diagram for explaining the measurement principle of the AC method.
Referring to FIG. 3, the AC signal generated by the oscillator is given to measurement target DUT. The current I flowing through the measurement target DUT at this time is detected by a current sensor. Further, the voltage V across the measurement target DUT is detected by a voltage sensor. A relationship of V = I · Z is established between these detected values and the impedance Z of the measurement target DUT according to Ohm's law.

  Here, the impedance Z of the measurement target DUT includes a real part (resistance component R) and an imaginary part (reactance component jX). In the AC method, it is possible to extract the resistance component R and the reactance component jX by measuring the time dependence of the impedance Z when the frequency of the AC signal is changed in the oscillator.

  Therefore, in order to calculate the internal resistance value of the secondary battery by the AC method, each battery block when the frequency is changed by giving an AC signal to each of the battery blocks B1 to Bn as the measurement target DUT. The internal resistance value can be extracted by measuring the flowing current and the voltage between terminals.

  However, in order to realize such a configuration, it is necessary to provide an oscillator for generating an AC signal as shown in FIG. As a result, problems such as an increase in the size of the motor drive device and an increase in device cost occur.

  Further, the AC signal output from the oscillator may cause noise to be superimposed on the signals PWMC and PWMI for performing switching control of the boost converter 22 and the inverter 24, thereby impairing the stability of the drive control of the AC motor M1. Sex will also emerge.

  Therefore, in order to maintain the stability of the drive control of the AC motor M1, the timing for calculating the internal resistance value of the secondary battery must be limited to when the vehicle system in which the drive of the AC motor M1 is stopped is stopped. Therefore, it becomes difficult to calculate the internal resistance value of the secondary battery as appropriate and to quickly determine the deterioration of the secondary battery.

  Therefore, the internal resistance detection device for a secondary battery according to the embodiment of the present invention, as will be described below, is a current (battery current Ib) that flows through battery blocks B1 to Bn when boost converter 22 performs a voltage conversion operation. ), Inter-terminal voltages of battery blocks B1 to Bn (corresponding to battery voltages Vb1 to Vbn), and carrier frequency fc for turning on / off IGBT elements Q1 and Q2 included in boost converter 22 The internal resistance values R1 to Rn of the battery blocks B1 to Bn are calculated.

  Such a configuration is based on the fact that the current flowing through the battery 10 includes an AC component that changes in a cycle equal to the control cycle in the boost converter 22 when the boost converter 22 performs a voltage conversion operation.

  With reference to FIG. 4, the relationship between the operation of boost converter 22 and the battery current Ib in the motor drive device of FIG. 1 will be described.

  FIG. 4 shows the transition of signal PWMC transmitted to boost converter 22. As shown in FIG. 4, the signal PWMC switches between an on state (ON) and an off state (OFF). The sum of the ON time and the OFF time at this time corresponds to one cycle (control cycle Tc) of the signal PWMC. The control period Tc can be obtained from the carrier frequency fc.

  When such a signal PWMC is output, the battery current Ib increases and decreases periodically. The cycle in which the battery current Ib increases or decreases matches the control cycle Tc of the boost converter 22.

  As described above, the battery current Ib is repeatedly increased and decreased at a cycle equal to the control cycle Tc, whereby the battery voltages Vb1 to Vbn also increase and decrease at a cycle equal to the control cycle Tc. The voltage fluctuation at this time is a value obtained by integrating the fluctuation of the battery current Ib and the impedance of the battery blocks B1 to Bn according to Ohm's law.

  The carrier frequency fc for determining the control cycle Tc is appropriately switched to an optimum frequency in the boost converter 22 in consideration of power loss, control stability, and the like.

  As an example, carrier frequency fc is set to a frequency that minimizes power loss in boost converter 22 in accordance with battery current Ib.

  Specifically, the loss in IGBT elements Q1 and Q2 of boost converter 22 increases as battery current Ib increases or carrier frequency fc increases. On the other hand, the loss in reactor L1 of boost converter 22 increases as battery current Ib increases or carrier frequency fc decreases. Therefore, for each battery current Ib, an optimum carrier frequency that minimizes the sum of the loss of IGBT elements Q1 and Q2 and the loss of reactor L1 is set in advance, and the optimum carrier frequency corresponding to battery current Ib received from current sensor 14 is set. By setting the carrier frequency to the carrier frequency fc, the boost converter 22 can be driven efficiently.

  Thus, switching of carrier frequency fc of boost converter 22 according to battery current Ib changes the cycle of the AC component included in battery current Ib and battery voltages Vb1 to Vbn. Therefore, the internal resistance values R1 to Rn of the battery blocks B1 to Bn are measured by measuring the frequency characteristics of the impedance of the battery blocks B1 to Bn based on the battery voltage Ib, the battery voltages Vb1 to Vbn, and the carrier frequency fc. Can be calculated.

  As described above, according to the embodiment of the present invention, based on the battery current Ib and the battery voltages Vb1 to Vbn and the carrier frequency fc of the boost converter 22, the internal resistance values of the battery blocks B1 to Bn are obtained by the AC method. Can be calculated. According to this, since it becomes unnecessary to install an oscillator for supplying an AC signal to the battery blocks B1 to Bn as shown in FIG. 3, it is possible to suppress an increase in the physique and device cost of the motor drive device. Can do. Further, since there is no problem such as noise superposition by the oscillator, the stability of drive control of AC motor M1 can be maintained. As a result, it is possible to quickly determine the deterioration of the secondary battery without limiting the timing for calculating the internal resistance value of the secondary battery.

  Hereinafter, a control structure for realizing detection of internal resistance values of battery blocks B1 to Bn according to the embodiment of the present invention will be described in more detail.

  FIG. 5 is a block diagram showing a control structure in MGECU 50 and battery monitoring unit 30.

  Referring to FIG. 5, MGECU 50 includes an inverter input voltage command calculation unit 52, a converter duty ratio calculation unit 54, and a converter PWM signal conversion unit 56.

  Inverter input voltage command calculation unit 52 calculates an optimum value (target value) of the inverter input voltage, that is, voltage command Vdc_com, based on torque command value TR and motor rotational speed MRN, and calculates the calculated voltage command Vdc_com as a duty for converter. It outputs to the ratio calculation part 54.

  The converter duty ratio calculation unit 54 calculates the output voltage Vm based on the DC voltage VB from the voltage sensor 12, the output voltage Vm from the voltage sensor 23, and the voltage command Vdc_com from the inverter input voltage command calculation unit 52. The duty ratio DR for setting the voltage command Vdc_com is calculated, and the calculated duty ratio DR is output to the converter PWM signal conversion unit 56.

  Converter PWM signal converter 56 sets the optimum carrier frequency corresponding to battery current Ib from current sensor 14 to carrier frequency fc. Specifically, converter PWM signal conversion unit 56 holds a map indicating the relationship between battery current Ib and the optimum carrier frequency that minimizes power loss of boost converter 22, and battery current from current sensor 14. The optimum carrier frequency corresponding to Ib is determined with reference to the map.

  Then, converter PWM signal conversion unit 56 turns on / off IGBT elements Q1, Q2 of boost converter 22 based on duty ratio DR from converter duty ratio calculation unit 54 and set carrier frequency fc. The signal PWMC is generated, and the generated signal PWMC is output to the IGBT elements Q1 and Q2 of the boost converter 22.

  Further, converter PWM signal conversion unit 56 outputs the set carrier frequency fc to internal resistance value calculation unit 32 included in battery monitoring unit 30.

  The internal resistance value calculation unit 32 performs an AC method based on the battery voltages Vb1 to Vbn from the voltage sensor 12, the battery current Ib from the current sensor 14, and the carrier frequency fc from the converter PWM signal conversion unit 56. The internal resistance values R1 to Rn of the battery blocks B1 to Bn are calculated. Then, the internal resistance value calculation unit 32 outputs the calculated internal resistance values R1 to Rn to the HVECU 40.

  The HVECU 40 determines the deterioration state of the battery blocks B1 to Bn based on the internal resistance values R1 to Rn from the internal resistance value calculation unit 32. At this time, if any of the internal resistance values R1 to Rn exceeds a predetermined threshold, the HVECU 40 generates a battery-related warning output signal and outputs it to a display means (not shown). For example, the display unit displays information indicating that an abnormality has occurred in the battery 10 on the instrument panel of the vehicle.

  FIG. 6 is a flowchart for realizing the detection operation of the internal resistance value of the secondary battery in the battery monitoring unit 30.

  Referring to FIG. 6, internal resistance value calculation unit 32 acquires battery current Ib from current sensor 14 (step S01), and acquires battery voltages Vb1 to Vbn of battery blocks B1 to Bn from voltage sensor 12 ( Step S02). Furthermore, internal resistance value calculation unit 32 acquires carrier frequency fc of boost converter 22 from MGECU 50 (step S03).

  And the internal resistance value calculating part 32 calculates internal resistance value R1-Rn of battery block B1-Bn by an alternating current method based on these input information (step S04). The internal resistance value calculation unit 32 outputs the calculated internal resistance values R1 to Rn to the HVECU 40 (step S05).

  As described above, according to the embodiment of the present invention, the internal resistance value of the secondary battery can be calculated by the AC method without using an oscillator for applying an AC signal to the secondary battery. As a result, it is possible to suppress an increase in the physique and device cost of the motor drive device equipped with the secondary battery, and it is possible to avoid the influence of noise caused by the oscillator and ensure the stability of the motor drive control.

  In addition, since the internal resistance value of the secondary battery can be calculated as appropriate when the motor driving device is operating, the deterioration state of the secondary battery can be quickly determined.

  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.

It is a schematic block diagram which shows the structure of the motor drive device to which the internal resistance detection apparatus of the secondary battery by embodiment of this invention is applied. It is a schematic block diagram for demonstrating the drive control of the alternating current motor in MGECU, and the detection operation of the internal resistance value in a battery monitoring part. It is the schematic for demonstrating the measurement principle of an alternating current method. It is a figure showing transition of signal PWMC transmitted to a boost converter. It is a block diagram which shows the control structure in MGECU and a battery monitoring part. It is a flowchart for implement | achieving the detection operation of the internal resistance value of a secondary battery in a battery monitoring part.

Explanation of symbols

  10 battery, 12, 23 voltage sensor, 14, 28 current sensor, 16 temperature sensor, 20 power control unit, 22 boost converter, 24 inverter, 25 U-phase arm, 26 V-phase arm, 27 W-phase arm, 30 battery monitoring unit 32 Internal resistance value calculation unit, 52 Inverter input voltage command calculation unit, 54 Converter duty ratio calculation unit, 56 Converter PWM signal conversion unit, B1 to Bn battery block, C2 capacitor, D1 to D8 diode, Q1 to Q8 IGBT Element, L1 reactor, M1 AC motor.

Claims (4)

A detection device for detecting an internal resistance value of a secondary battery included in a power supply device for driving an electric load,
The power supply device
The secondary battery;
A drive circuit that receives power from the secondary battery and drives the electrical load;
A voltage converter that includes a switching element and converts a DC voltage between the secondary battery and the drive circuit by a switching operation of the switching element;
A control device for controlling the voltage converter by changing a switching frequency for turning on / off the switching element;
The detection device includes:
Current voltage acquisition means for acquiring a current value and a voltage value of the secondary battery;
Switching frequency acquisition means for acquiring the switching frequency;
An internal resistance detection device for a secondary battery, comprising: an internal resistance value calculation means for calculating an internal resistance value of the secondary battery based on the acquired current value, voltage value and the switching frequency.   The internal resistance value calculating means acquires the frequency characteristic of the impedance of the secondary battery based on the acquired current value, voltage value and the switching frequency, and based on the acquired frequency characteristic of the impedance, The internal resistance detection device for a secondary battery according to claim 1, wherein the internal resistance value of the secondary battery is calculated. A detection method for detecting an internal resistance value of a secondary battery included in a power supply device for driving an electric load,
The power supply device
The secondary battery;
A drive circuit that receives power from the secondary battery and drives the electrical load;
A voltage converter that includes a switching element and converts a DC voltage between the secondary battery and the drive circuit by a switching operation of the switching element;
A control device for controlling the voltage converter by changing a switching frequency for turning on / off the switching element;
The detection method is:
A current voltage acquisition step of acquiring a current value and a voltage value of the secondary battery;
A switching frequency acquisition step of acquiring the switching frequency;
An internal resistance value calculating step of calculating an internal resistance value of the secondary battery based on the acquired current value, voltage value, and the switching frequency. The internal resistance value calculating step includes:
Obtaining a frequency characteristic of impedance of the secondary battery based on the acquired current value, voltage value and the switching frequency;
The internal resistance detection method of the secondary battery of Claim 3 including the step which calculates the internal resistance value of the said secondary battery based on the frequency characteristic of the said acquired impedance.

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