JP4762505B2 - Battery warm-up control device - Google Patents

Description

  The present invention relates to a battery warm-up control device that controls charging / discharging of a battery at a low temperature to warm up the battery by internal heat generation.

  In general, since the capacity of a battery decreases when the temperature decreases, there is a possibility that starting failure or deterioration of controllability may be caused when the battery is used as a power source for traveling such as an electric vehicle or a hybrid vehicle. For this reason, conventionally, various techniques for warming up the battery at a low temperature by heat generation utilizing the internal resistance of the heater or the battery have been proposed.

  For example, in Patent Document 1, when the temperature of the battery is lower than a predetermined temperature, at least one of charging and discharging of the battery is performed, and at the time of discharging, discharge power is supplied by a resistor disposed on the side of the battery. And the technique of heating a battery from the outside is disclosed.

  In Patent Document 2, chargeable power or dischargeable power is calculated from the temperature, voltage, and current of the battery, and the warm-up of the battery is calculated based on the calculation result and each desired value of the predetermined charge power or discharge power. A technique for determining whether or not to drive is disclosed.

Further, in Patent Document 3, when the temperature of the battery is equal to or lower than a predetermined value, when the charge state of the battery is equal to or higher than a preset threshold value, charge / discharge is repeated within a predetermined region equal to or higher than the threshold value, and the charge state is lower than the threshold value. In some cases, a technique is disclosed in which charging and discharging are repeated within a predetermined region less than a threshold value.
JP 2000-40536 A JP 2003-23704 A JP 2003-272712 A

  However, since the technique disclosed in Patent Document 1 is based on a remaining capacity (charged state: SOC) of about 100% as a standard for charging / discharging at low temperatures, it is not desirable from the viewpoint of battery protection. Fine control is difficult. Moreover, when the internal resistance of the battery is large at low temperatures, it is assumed that charging with full capacity is difficult from the beginning. Furthermore, when a heater is used outside the battery, the battery body may be frosted.

  The technology disclosed in Patent Document 2 is charge / discharge control by a single motor of an electric vehicle, and when applied to a hybrid vehicle, the apparatus and control are complicated and difficult to apply. Furthermore, since the speed of the battery temperature increase greatly depends on the driving condition of the vehicle, the technique disclosed in Patent Document 3 is at a low temperature that requires a certain amount of rapid heat generation in a short time (for example, , 0 ° C. or less), heat is quickly taken away, and the efficiency may decrease.

  The present invention has been made in view of the above circumstances, and it is possible to efficiently control charging / discharging according to the state of the battery at a low temperature, promote a temperature increase due to internal heat generation, and recover the battery capacity early. An object is to provide a warm-up control device.

In order to achieve the above object, a battery warm-up control device according to the present invention is a battery warm-up control device that controls charging / discharging of a battery at a low temperature to warm up the battery due to internal heat generation. Remaining capacity calculation means for calculating the capacity based on the charge / discharge current and open circuit voltage of the battery, and power for calculating the input / output possible power amount of the battery based on the charge / discharge current and internal impedance of the battery Charge and discharge of the battery based on a battery state including a quantity calculation means, at least a temperature of the battery, a remaining capacity calculated by the remaining capacity calculation means, and an input / output possible power amount calculated by the power amount calculation means DOO alternating amplitude of charging and discharging of the charging and discharging pattern gradually increases repeating pulsed to and cycle A discharge pattern setting means for variably setting the charging and discharging pattern to be longer people, the limiter values of the limiter value for restricting the maximum amplitude value the voltage amplitude of the charging and discharging pattern is variably set according to the temperature of the battery When the temperature of the battery is lower than a specified temperature, the charging / discharging of the battery according to the charging / discharging pattern set by the charging / discharging pattern setting unit is executed within the range of the limiter value set by the limiter value setting unit. And a warm-up control means for raising the temperature of the battery.

  At this time, the charge / discharge pattern is preferably switched between a mode for charging the battery and a mode for discharging from the battery when at least one of the remaining capacity and the input / output power amount reaches a set value. At the start of charge / discharge, it is desirable to set the amplitude and period of the charge / discharge pattern to values based on the remaining capacity, and then gradually increase the amplitude and period of the charge / discharge pattern based on the battery state. The limiter value is preferably set as a value obtained by correcting the upper and lower limit voltages of the battery in consideration of the battery temperature and the degree of deterioration.

  The remaining capacity is determined by using a first weight that is set in accordance with the battery usage state, the first remaining capacity based on the integrated value of the charge / discharge current of the battery and the second remaining capacity based on the open circuit voltage of the battery. It is possible to calculate with high accuracy by weighted synthesis. In addition, the input / output power amount includes a first power amount based on the internal impedance and open circuit voltage of the battery, and a second power amount based on the internal impedance and charge / discharge current of the battery, depending on the use state of the battery. By performing weighted synthesis using the set second weight, it is possible to calculate with high accuracy.

  The battery warm-up control device according to the present invention can efficiently control charging / discharging according to the state of the battery at a low temperature to promote a temperature increase due to internal heat generation, and quickly recover the battery capacity that has decreased at a low temperature. be able to.

  Embodiments of the present invention will be described below with reference to the drawings. 1 to 12 relate to an embodiment of the present invention, FIG. 1 is a system configuration diagram showing an application example to a hybrid vehicle, FIG. 2 is a block diagram showing an estimation algorithm of remaining capacity, and FIG. 3 is a current capacity table. FIG. 4 is a circuit diagram showing an equivalent circuit model, FIG. 5 is an explanatory diagram of an impedance table, FIG. 6 is an explanatory diagram of a remaining capacity table, FIG. 7 is an explanatory diagram of a weight table, and FIG. FIG. 9 is a flowchart showing battery warm-up control processing, FIG. 10 is a flowchart showing pulse charging / discharging processing, FIG. 11 is an explanatory diagram showing an outline of pulse charging / discharging, and FIG. 12 is based on pulse charging / discharging. It is explanatory drawing which shows the raise of battery temperature.

  FIG. 1 shows an example in which the present invention is applied to a hybrid vehicle (HEV) that travels using both an engine and a motor. In the figure, reference numeral 1 denotes a HEV power supply unit. The power unit 1 includes, for example, a battery 2 configured by connecting a plurality of cells in series, calculation of the remaining capacity of the battery 2, cooling and charging control of the battery 2, abnormality detection, and abnormality detection An arithmetic unit (arithmetic ECU) 3 that performs energy management such as protection operation is packaged in one casing.

  The arithmetic ECU 3 is composed of a microcomputer or the like, and the terminal voltage V of the battery 2 measured by the voltage sensor 4, the charge / discharge current I of the battery 2 measured by the current sensor 5, and the temperature (cell) of the battery 2 measured by the temperature sensor 6. Based on the temperature (T), the remaining capacity SOC (t) indicated by the state of charge (SOC) of the battery 2 and the input / output possible power amount P (t) indicated by the maximum input / output power in the battery 2 Is calculated. Note that the remaining capacity SOC (t−1) and the input / output power amount P (t−1) before one calculation cycle are input to the calculation ECU 3 as base values in the cyclic calculation.

  The remaining capacity SOC and the input / output possible power amount P calculated by the calculation ECU 3 are output to the HEV control electronic control unit (HEV control ECU) 10 via, for example, CAN (Controller Area Network) communication or the like, and display of the control state And used as basic data for determining the control amount. The HEV control ECU 10 is similarly configured from a microcomputer or the like, and performs HEV operation and other necessary control based on a command from the driver. That is, the HEV control ECU 10 detects the state of the vehicle based on signals from the power supply unit 1 and signals from sensors and switches (not shown), and converts the DC power of the battery 2 into AC power to drive the motor 15. Starting with the inverter 20, the engine 30 connected to the motor 15, an automatic transmission (not shown), and the like are controlled via a dedicated control unit or directly.

  For example, from the remaining capacity SOC calculated by the calculation ECU 3, display data for battery capacity and warning data for warning the battery capacity decrease are generated and used as battery information for the driver. Further, from the input / output possible power amount P calculated by the arithmetic ECU 3, the driving torque that can be output from the motor 15, the charge / regeneration amount by the power generation of the motor 15, and the like are calculated, and the control amount necessary for the HEV operation is calculated. Used as a direct parameter above.

  Further, the arithmetic ECU 3 warms up the battery 2 at a low temperature so as to quickly recover the battery capacity that has been reduced due to the temperature drop, thereby preventing start-up failure and deterioration of controllability. In this embodiment, the battery warm-up employs a method in which the charging through the inverter 20 and the discharging through the discharging device 25 are repeated to generate heat due to the internal resistance, thereby increasing the cell temperature.

  Then, the calculation ECU 3 functions as a charge / discharge pattern setting means, and alternately charges and discharges in a pulsed manner based on the battery state including at least the cell temperature T, the remaining capacity SOC, and the input / output power amount P. The charge / discharge pattern to be repeated is variably set, and the limiter value setting means is used to variably set the limiter value that regulates the maximum amplitude of the charge / discharge pattern. When the battery temperature is lower than the specified temperature, the warm-up control means By this function, charging / discharging of the battery by the charging / discharging pattern is executed within the limit value range, and the temperature of the battery is raised. Thereby, charging / discharging can be controlled efficiently and the original capacity of the battery can be rapidly recovered.

  In this case, in order to efficiently warm up the battery, a highly accurate remaining capacity SOC and an input / output possible power amount P are required. In the present embodiment, the remaining capacity SOC and the input / output possible power amount P are calculated with high accuracy according to a specific algorithm. Next, the calculation process of the remaining capacity SOC and the input / output possible power amount P in the present embodiment will be described. To do.

  First, the remaining capacity SOC is calculated according to the estimation algorithm shown in FIG. In this SOC estimation algorithm, the remaining capacity as the first remaining capacity based on the current integration is obtained by using the parameters measurable by the battery 2, that is, the terminal voltage V, the current I, and the temperature T, and the function as the remaining capacity calculating means. The SOCc and the remaining capacity SOCv as the second remaining capacity based on the estimated value of the battery open voltage Vo are calculated in parallel, and the remaining capacity SOC synthesized by weighting each is output as the remaining capacity of the battery 2. .

  The remaining capacity SOCc obtained by integrating the current I and the remaining capacity SOCv obtained by estimating the open circuit voltage Vo have their merits and demerits, and the remaining capacity SOCc obtained by integrating the current tends to accumulate errors. On the other hand, it is strong against load fluctuations such as inrush current. On the other hand, the remaining capacity SOCv based on the open-circuit voltage estimation can be obtained as a substantially accurate value during normal use, but the value may oscillate when the load greatly fluctuates in a short time.

Therefore, in the present SOC estimation algorithm, the remaining capacity SOCc (t) obtained by integrating the current I and the remaining capacity SOCv (t) obtained from the estimated value of the battery open voltage Vo are determined according to the usage state of the battery 2. Thus, the weight w as a first weight (weighting coefficient) that is changed as needed is weighted and combined, so that the disadvantages of both of the remaining capacities SOCc and SOCv are canceled out and the mutual advantages are maximized. The weight w is changed between w = 0 and 1, and the final remaining capacity SOC (t) after synthesis is given by the following equation (1).
SOC (t) = w.SOCc (t) + (1-w) .SOCv (t) (1)

  The weight w needs to be determined using a parameter that can accurately represent the current battery usage. The parameters include the current change rate per unit time and the deviation between the remaining capacities SOCc and SOCv. Etc. can be used. The current change rate per unit time directly reflects the load fluctuation of the battery, but the mere current change rate is affected by a sudden change in current that occurs in a spike manner.

  Therefore, in this embodiment, in order to prevent the influence of a change in current that instantaneously stops, a current change rate that has been processed by a simple average, a moving average, a weighted average, or the like of a predetermined sampling number is used. In particular, when considering a delay in current, the weight w is determined using a moving average that can appropriately reflect the past history without excessively changing the charge / discharge state of the battery. I have to.

  By determining the weight w based on the moving average value of the current I, when the moving average value of the current I is large, the weight of the current integration is increased to lower the weight of the open circuit voltage estimation, and the influence of the load fluctuation is While accurately reflecting by integration, vibration during open circuit voltage estimation can be prevented. Conversely, when the moving average value of current I is small, the effect of error accumulation during current integration is avoided by reducing the current integration weight and increasing the open-circuit voltage estimation weight. The remaining capacity can be calculated.

  That is, the moving average of the current I becomes a low-pass filter with respect to the high frequency component of the current, and the moving average filtering can remove the spike component of the current generated by the load fluctuation during traveling without promoting the delay component. it can. As a result, the battery state can be grasped more accurately, the disadvantages of both the remaining capacities SOCc and SOCv can be canceled, the mutual advantages can be maximized, and the estimation accuracy of the remaining capacities can be greatly improved.

  Further, as a feature of the present SOC estimation algorithm, the internal state of the battery is electrochemically grasped based on the battery theory, and the calculation accuracy of the remaining capacity SOCv based on the battery open voltage Vo is improved. Hereinafter, the calculation of the remaining capacities SOCc and SOCv by the SOC estimation algorithm will be described in detail.

First, as shown in the following equation (2), the remaining capacity SOCc by current integration is obtained by integrating the current I every predetermined time with the remaining capacity SOC synthesized using the weight w as a base value.
SOCc (t) = SOC (t−1) −∫ [(100ηI / Ah) + SD] dt / 3600 (2)
Where η: current efficiency
Ah: Current capacity (variable depending on temperature)
SD: Self-discharge rate

  Although the current efficiency η and the self-discharge rate SD in the equation (2) can be regarded as constants (for example, η = 1, SD = 0), the current capacity Ah varies depending on the temperature. Therefore, when calculating the remaining capacity SOCc by this current integration, the current capacity Ah calculated by functionalizing the variation of the cell capacity with temperature is used.

  FIG. 3 shows an example of a current capacity table storing a capacity ratio Ah ′ with respect to a rated capacity with a temperature T as a parameter (for example, a rated current capacity with a predetermined number of cells as a reference unit). Since the current capacity decreases as the temperature becomes lower than the capacity ratio Ah ′ (= 1.00) at room temperature (25 ° C.), the value of the capacity ratio Ah ′ increases. Using the capacity ratio Ah ′ referred to from this current capacity table, the current capacity Ah at the temperature T for each measurement target can be calculated.

Further, the calculation of the remaining capacity SOCc (t) by the equation (2) is specifically executed by discrete time processing in the calculation ECU 3, and the combined remaining capacity SOC (t−1) one calculation cycle before is calculated as the current integration. It is input as a base value (delay operator Z ⁻¹ in the block diagram of FIG. 2). Therefore, errors do not accumulate or diverge, and even if the initial value is significantly different from the true value, it should converge to the true value after a predetermined time (for example, after several minutes). Can do.

  On the other hand, in order to obtain the remaining capacity SOCv based on the estimation of the open circuit voltage Vo, first, the internal impedance Z of the battery is obtained using the equivalent circuit model shown in FIG. This equivalent circuit is an equivalent circuit model in which parameters of resistance components R1 to R3 and capacitance components C1, CPE1, and CPE2 (where CPE1 and CPE2 are double layer capacitance components) are combined in series and in parallel. Each parameter is determined by curve fitting a well-known Cole-Cole plot in the method.

The impedance Z obtained from these parameters varies greatly depending on the temperature of the battery, the electrochemical reaction rate, and the frequency component of the charge / discharge current. Accordingly, the moving average value of the current I per unit time described above is used as a frequency component replacement as a parameter for determining the impedance Z, and impedance measurement is performed on the condition of the moving average value of the current I and the temperature T. After storing the data, a table of impedance Z is created based on the temperature T and the moving average value of the current I per unit time. Then, the impedance Z is obtained using this table, and the estimated value of the open circuit voltage Vo is obtained from the impedance Z, the measured terminal voltage V, and the current I using the following equation (3).
V = Vo-I · Z (3)

  Note that the moving average value of the current I is obtained, for example, by moving and averaging five pieces of data when the sampling of the current I is performed every 0.1 sec and the calculation cycle of current integration is performed every 0.5 sec. As described above, the moving average value of the current I is also used as a parameter for determining the weight w and facilitates the calculation of the weight w and the impedance Z. In detail, the internal impedance of the battery decreases as the temperature decreases. As will be described later, the weight w and the impedance Z are directly calculated using the corrected current change rate KΔI / Δt obtained by correcting the moving average value of the current I with temperature, as will be described later. decide.

  FIG. 5 shows the impedance Z of the equivalent circuit with the corrected current change rate KΔI / Δt obtained by correcting the temperature of the current change rate ΔI / Δt (moving average value of the current I per unit time) and the temperature T as parameters. An example of an impedance table is shown. Generally, when the corrected current change rate KΔI / Δt is the same, the impedance Z increases as the temperature T decreases, and at the same temperature, the corrected current change As the rate KΔI / Δt decreases, the impedance Z tends to increase.

  In the table shown in FIG. 5 and FIG. 6 to be described later, data in a range used under normal conditions is shown, and data in other ranges is omitted.

After the open circuit voltage Vo is estimated, the remaining capacity SOCv is calculated based on the electrochemical relationship in the battery. Specifically, a well-known Nernst equation describing the relationship between the electrode potential and the ion activity in an equilibrium state is applied, and the relationship between the open-circuit voltage Vo and the remaining capacity SOCv is expressed as the following (4). The formula can be obtained.
Vo = E + [(Rg · T / Ne · F) × lnSOCv / (100−SOCv)] + Y (4)
However, E: Standard electrode potential (E = 3.745 in the lithium ion battery of this embodiment)
Rg: Gas constant (8.314 J / mol-K)
T: temperature (absolute temperature K)
Ne: Ion valence (Ne = 1 in the lithium ion battery of this embodiment)
F: Faraday constant (96485 C / mol)

Note that Y in the equation (4) is a correction term and expresses the voltage-SOC characteristic at normal temperature as a function of SOC. If SOCv = X, it can be expressed by a cubic function of SOC as shown in the following equation (5).
Y = −10 ⁻⁶ X ³ + 9 · 10 ⁻⁵ X ² + 0.013X−0.7311 (5)

  From the above equation (4), it can be seen that the remaining capacity SOCv has a strong correlation not only with the open circuit voltage Vo but also with the temperature T. In this case, the remaining capacity SOCv can be calculated directly using the equation (4) using the open-circuit voltage Vo and the temperature T as parameters. Consideration of conditions is necessary.

  Therefore, when grasping the actual state of the battery from the relationship of the above equation (4), a charge / discharge test or simulation in each temperature range is performed based on the SOC-Vo characteristics at room temperature, and the measured data is obtained. accumulate. Then, a table of the remaining capacity SOCv that parameters the open circuit voltage Vo and the temperature T is created from the accumulated measured data, and the remaining capacity SOCv is obtained using this table. FIG. 6 shows an example of the remaining capacity table. Generally, the lower the temperature T and the open circuit voltage Vo, the smaller the remaining capacity SOCv, and the higher the temperature T and the open circuit voltage Vo, the remaining capacity. The capacity SOCv tends to increase.

  After calculating the remaining capacities SOCc and SOCv, as shown in the above equation (1), the remaining capacities SOCc and SOCv are weighted and synthesized using the weight w determined by referring to the table or the like, and the remaining capacities SOC are obtained. Is calculated. FIG. 7 shows an example of a weight table for determining the weight w, and is a one-dimensional table using the corrected current change rate KΔI / Δt as a parameter. This weight table generally indicates that the smaller the corrected current change rate KΔI / Δt, that is, the smaller the battery load fluctuation, the smaller the value of the weight w and the smaller the weight of the remaining capacity SOCc due to current integration. Have a tendency to

  On the other hand, the calculation of the input / output possible power amount P is executed according to the calculation algorithm shown in FIG. 8 similar to the SOC estimation algorithm. In this calculation algorithm, parameters that can be measured by the battery 2, that is, the terminal voltage V, the current I, and the temperature T are used, and the power amount PV based on the open voltage Vo of the battery 2 and the battery by the function as the power amount calculation means A power amount PC based on the current I of 2 is calculated in parallel, and a value obtained by weighting and combining each is output as the power amount P of the battery 2.

  That is, the power amount PV based on the open-circuit voltage Vo of the battery 2 can be obtained as a substantially accurate value during normal use, but the value may vibrate when the load greatly fluctuates in a short time. There is. On the other hand, the power amount PC based on the current I of the battery 2 tends to accumulate errors, and is particularly resistant to load fluctuations such as inrush currents, while the error during high load continuation is large. Therefore, in the present power amount calculation algorithm, the power amount PV obtained based on the open circuit voltage Vo and the power amount PC obtained based on the current I are used as second weights that change as needed depending on the usage state of the battery 2. The weights wp are combined and combined, and both disadvantages are canceled to maximize each other's advantages.

The weight wp is determined based on the moving average of the current I as in the case of the weight w used for the synthesis of the remaining capacity SOC (wp = 0 to 1). The final power amount P after the synthesis is as follows: (6).
P = wp * PC + (1-wp) * PV (6)

  By determining the weight wp based on the moving average value of the current I, when the moving average value of the current I is large, the weight of the power amount PC based on the open voltage Vo is increased by increasing the weight of the power amount PC based on the current I. , And the effect of load fluctuation can be accurately reflected by the current and vibration can be prevented. Conversely, when the moving average value of the current I is small, the weight of the power amount PC based on the current I is lowered, and the weight of the power amount PV based on the open circuit voltage Vo is increased, thereby avoiding the influence due to accumulation of current errors. In addition, an accurate power amount based on the open circuit voltage can be calculated.

  Specifically, the power amount P shown in the equation (6) is an input possible power amount Pcharge indicated by the maximum power amount that can be input (charged) to the battery 2 and a maximum power amount that can be output (discharged) from the battery 2. The output possible power amount Pdischarge shown is a generic name, and is calculated individually by the following equations (7) and (8) based on the equation (6).

That is, the input possible power amount Pcharge is obtained by the following equation (7), the power amount PVcharge as the first input possible power amount based on the open circuit voltage Vo and the second input possible power amount based on the moving average of the current I. As a value obtained by weighted synthesis of the power amount PCcharge. Further, the output possible power amount Pdischarge is expressed by the following equation (8), the second output possible power amount based on the power amount PVdischarge as the first outputable power amount based on the open circuit voltage Vo and the moving average of the current I. As a value obtained by weighting and combining the power amount PCdischarge.
Pcharge = wp / PCcharge + (1-wp) / PVcharge (7)
Pdischarge = wp / PCdischarge + (1-wp) / PVdischarge (8)

  Specifically, each of the power amounts PVcharge, PVdischarge, PCcharge, and PCdischarge includes the internal impedance Z of the battery 2, the open circuit voltage Vo, the upper limit voltage Vmax that is the upper and lower limit battery voltage that guarantees predetermined battery characteristics, and the lower limit. The calculation is performed using the moving average value of the voltage Vmin and the current I, the input power amount Pcharge (t) before the calculation cycle, and the output power amount Pdischarge (t) before the calculation period.

  The upper limit voltage Vmax and the lower limit voltage Vmin can be defined as a voltage that gives an upper limit (100%) and a voltage that gives a lower limit (0%), respectively, and changes depending on the temperature. It is obtained by referring to a table having T as a parameter. The table of the upper limit voltage Vmax and the lower limit voltage Vmin may be obtained by creating a dedicated table storing the upper limit voltage Vmax and the lower limit voltage Vmin using the temperature T as a parameter and referring to this dedicated table. The upper limit voltage Vmax and the lower limit voltage Vmin at the temperature T are known by using the remaining capacity table (see FIG. 6) used in the calculation of the capacity SOC and referring to the upper and lower limits of the open circuit voltage Vo at the predetermined temperature T. Can do.

The input possible power amount PVcharge is obtained by multiplying the current value obtained by dividing the difference between the upper limit voltage Vmax and the open circuit voltage Vo by the impedance Z by the upper limit voltage Vmax as shown in the following equation (9). As a quantity. Further, as shown in the following equation (10), the output possible power amount PVdischarge is a power obtained by multiplying the current value obtained by dividing the difference between the open circuit voltage Vo and the lower limit voltage Vmin by the impedance Z by the lower limit voltage Vmin. As a quantity.
PVcharge = [(Vmax−Vo) / Z] · Vmax (9)
PVdischarge = [(Vo−Vmin) / Z] · Vmin (10)

On the other hand, the power amounts PCcharge and PCdischarge based on the moving average of the current I use the combined power amount P (t−1) one cycle before the discrete time processing as a base value (delay calculation in the block diagram of FIG. 8). Child Z ^-1 ), errors do not accumulate or diverge, and even if the initial value is significantly different from the true value, the true value is reached after a predetermined time (for example, after several minutes). Can be converged to.

In other words, when the moving average value of the current I is I ′, as shown in the following equation (11), the combined input possible power amount Pcharge (t−1) before the calculation cycle and the moving average value I ′ have an impedance. Based on the input power amount I ′ ² Z multiplied by Z, the current input power amount PCcharge is obtained. Further, as shown in the following equation (12), the combined output possible power amount PCdischarge before one operation cycle and the output power amount I ′ ² Z obtained by multiplying the moving average value I ′ by the impedance Z The amount of output power PCdischarge is obtained.
PCcharge = Pcharge (t−1) −I ′ ² Z (11)
PCdischarge = Pdischarge (t-1) −I ′ ² Z (12)

  Then, as shown in the above equation (7), the input possible power amount PVcharge calculated by the equation (9) and the input allowable power amount PCcharge calculated by the equation (11) are weighted using the weight wp. Combining and calculating the input possible power amount Pcharge. Further, as shown in the above equation (8), the outputable power amount PVdischarge calculated by the equation (10) and the outputable power amount PCdischarge calculated by the equation (12) are weighted using the weight wp. Combining and calculating the output possible power amount Pdischarge.

  Next, battery warm-up control processing based on the above remaining capacity SOC and input / output possible power amount P will be described with reference to the flowchart shown in FIG.

  The warm-up control process shown in the flowchart of FIG. 9 is a process executed by the arithmetic ECU 3 of the power supply unit 1 every predetermined time at a low temperature. When this process starts, first, in step S1, data of each parameter indicating the battery state, that is, data of each parameter including the cell temperature T, the input / output possible power amount P, and the remaining capacity SOC are input.

  Next, it progresses to step S2 and it is investigated whether cell temperature T is more than regulation temperature. Below this specified temperature, there is a possibility that control problems may occur due to a decrease in battery capacity. For example, the specified temperature is set to 10 ° C. in advance from the characteristics shown in the current capacity table of FIG. ing. If the cell temperature T is equal to or higher than the specified temperature and the warm-up is not required, the process exits from step S2, and if the temperature is lower than the specified temperature, the process proceeds to step S3 to initialize the warm-up charge / discharge pattern. In step S4, warm-up is performed by the pulse charge / discharge process shown in FIG.

  The warm-up charging / discharging pattern is a pattern in which charging and discharging are alternately repeated in a pulse shape, and in this embodiment, CV (Constant Voltage) charging / discharging is adopted to promote efficient heat generation. The reason why this CV charging / discharging is adopted is that, as described above, the internal resistance (impedance) of the battery becomes larger when the current change rate becomes smaller at the same temperature, that is, when a direct current is passed rather than an alternating current. This is because a large current flows at the rise of charge / discharge, but converges to 0 with time.

  At the start of the first charge / discharge, as shown in FIG. 11, in order to reduce the burden on the battery cell, initialization is performed so that the amplitude value is reduced and the period is shortened with reference to the remaining capacity SOC at that time. After the pulse charge / discharge is started, the charge / discharge is gradually performed within the maximum amplitude value while monitoring parameters such as the cell temperature T, the remaining capacity SOC, the input / output power amount P, the current value I, and the voltage V. Increase the amplitude and lengthen the period.

  The maximum amplitude value is a limiter for protecting the battery by restricting the upper and lower limits of the voltage amplitude in pulse charge / discharge, and the upper limit voltage that is corrected in consideration of the degree of deterioration of the upper limit voltage Vmax that changes depending on the temperature. The maximum amplitude value is set by Vmax ′ and the lower limiter voltage Vmin ′ obtained by correcting the lower limit voltage Vmin that also varies depending on the temperature in consideration of the degree of deterioration.

  Here, the pulse charge / discharge process of FIG. 10 will be described. In this process, first, in step S11, the latest data representing the battery state such as the cell temperature T, the input / output possible power amount P, the remaining capacity SOC and the like are input, and in step S12, pulse charge / discharge is performed based on the battery state. In addition to updating the pattern such as the amplitude value and the period, the maximum amplitude value by the upper limiter voltage Vmax ′ and the lower limiter voltage Vmin ′ is updated based on the latest cell temperature T.

  In this embodiment, the voltage amplitude of pulse charging / discharging is increased by a set value for each control cycle, and switching between discharging and charging is performed based on the input / output possible power amount P and the remaining capacity SOC, and the input / output possible power amount P. And at least one of the remaining capacity SOC reaches a set value. The set value for switching charge / discharge is varied in a direction gradually approaching the upper limiter voltage Vmax ′ or the lower limiter voltage Vmin ′, whereby the voltage pulse width of the pulse charge / discharge is gradually increased (the period is gradually increased). Become).

  Next, the process proceeds from step S12 to step S13, and it is checked whether at least one of the input / output possible power amount P and the remaining capacity SOC is equal to or greater than a specified value in order to switch between the charge mode and the discharge mode in the charge / discharge pattern. As a result, when at least one of the input / output possible power amount P and the remaining capacity SOC exceeds the specified value, the process proceeds from step S13 to step S14, and shifts to a discharge mode in which the battery is discharged via the discharge device 25. When both the input / output possible power amount P and the remaining capacity SOC do not exceed the specified values, the process proceeds from step S13 to step S15, and the mode is changed to the charging mode in which the battery is charged via the inverter 20.

  The switching between the discharging mode and the charging mode may be performed based on the current current I. When the current value is substantially converged, switching from discharging to charging or switching from charging to discharging is performed. You may make it do.

  As described above, after the charge / discharge mode is determined and the pulse charge / discharge is performed, the process proceeds to step S5 of the warm-up control process, and it is determined whether the cell temperature has increased to the specified temperature due to the pulse charge / discharge. Investigate. As a result, when the cell temperature reaches the specified temperature, the process is terminated from step S5 and the warm-up is substantially ended.

  On the other hand, when the cell temperature does not reach the specified temperature, the process proceeds from step S5 to step S6, and whether or not the voltage amplitude of charge / discharge has reached the maximum amplitude value by the upper limiter voltage Vmax ′ and the lower limiter voltage Vmin ′. Check out. When the voltage amplitude of charging / discharging does not reach the maximum amplitude value, the process returns from step S6 to step S4, and the pulse charging / discharging is performed according to the monitoring results such as the cell temperature T, the input / output possible power amount P, the remaining capacity SOC. Continue to warm up while varying the voltage amplitude and period.

  When the voltage amplitude of charging / discharging reaches the maximum amplitude value, the process is temporarily exited from step S6. As a result, in step S3 of the next processing cycle, as shown by the broken line in FIG. 11, the charge / discharge pattern is returned to the initial charge / discharge pattern with a small amplitude value and a short cycle, and warm-up is continued while protecting the battery. .

  FIG. 12 shows the temperature rise of the battery due to the above-described pulse charge / discharge, and the cell temperature rises smoothly as if proportional to the amplitude and period of the pulse charge / discharge pattern that is gradually changed over time. It can be seen that the battery can be warmed up efficiently. In FIG. 12, the cell temperature indicates a relative temperature rise with the temperature at the start of warm-up being 2 ° C. as a reference (coordinate origin).

System configuration diagram showing an example of application to a hybrid vehicle Block diagram showing remaining capacity estimation algorithm Illustration of current capacity table Circuit diagram showing equivalent circuit model Illustration of impedance table Explanation of remaining capacity table Illustration of weight table A block diagram showing an algorithm for calculating the amount of power, Flow chart showing battery warm-up control process Flow chart showing pulse charge / discharge processing Explanatory drawing showing the outline of pulse charge / discharge Explanatory diagram showing rise in battery temperature due to pulse charge / discharge

Explanation of symbols

1 power supply unit 2 battery 3 calculation unit (remaining capacity calculation means, power amount calculation means, charge / discharge pattern setting means, limiter value setting means, warm-up control means)
I Charge / discharge current SOC Remaining capacity (Remaining capacity after synthesis)
SOCc remaining capacity (first remaining capacity)
SOCv remaining capacity (second remaining capacity)
P power amount (power amount after synthesis)
PV power amount (first power amount)
PC power amount (second power amount)
V terminal voltage Vo open circuit voltage Z impedance w weight (first weight)
wp weight (second weight)
Agent Patent Attorney Susumu Ito

Claims (6)

In the battery warm-up control device for controlling the charging / discharging of the battery at a low temperature to warm up the battery due to internal heat generation,
A remaining capacity calculating means for calculating the remaining capacity of the battery based on a charge / discharge current and an open-circuit voltage of the battery;
Power amount calculating means for calculating the input / output possible power amount of the battery based on the charge / discharge current and internal impedance of the battery;
The battery is alternately charged and discharged based on a battery state including at least the temperature of the battery, the remaining capacity calculated by the remaining capacity calculating means, and the input / output possible power amount calculated by the power amount calculating means. Charging / discharging pattern setting means for variably setting the charging / discharging pattern so that the charging / discharging amplitude of the charging / discharging pattern repeated gradually increases and the period gradually increases ;
A limiter value setting means for variably setting a limit value for restricting the maximum amplitude value the voltage amplitude of the charging and discharging pattern in accordance with the temperature of the battery,
When the temperature of the battery is lower than a specified temperature, the battery is charged / discharged by the charge / discharge pattern set by the charge / discharge pattern setting means within the limiter value set by the limiter value setting means, and the battery And a warm-up control means for raising the temperature of the battery. The charge / discharge pattern setting means includes:
2. The battery according to claim 1, wherein when at least one of the remaining capacity and the input / output power amount reaches a set value, a mode for charging the battery and a mode for discharging from the battery are switched. Warm-up control device. The charge / discharge pattern setting means includes:
At the beginning of charging / discharging of the battery, the amplitude and period of the charging / discharging pattern are set to values based on the remaining capacity, and then the amplitude and period of the charging / discharging pattern are gradually increased based on the battery state. The battery warm-up control device according to claim 1 or 2, The limiter value setting means is:
4. The battery warm according to claim 1, wherein the limiter value is set as a value obtained by correcting the upper and lower limit voltages of the battery in consideration of the temperature and the deterioration degree of the battery. Up control device. The remaining capacity calculating means is
The first remaining capacity based on the integrated value of the charge / discharge current of the battery and the second remaining capacity based on the open circuit voltage of the battery are weighted using a first weight set in accordance with the use state of the battery. The battery warm-up control device according to any one of claims 1 to 4, wherein the battery warm-up control device combines and calculates the remaining capacity of the battery. The power amount calculation means includes:
A first power amount based on the internal impedance and open circuit voltage of the battery and a second power amount based on the internal impedance and charge / discharge current of the battery are set in accordance with the usage status of the battery. The battery warm-up control apparatus according to claim 1, wherein weighted synthesis is performed using weights, and an input / output power amount of the battery is calculated.

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