JP5401366B2 - Control device for hybrid vehicle - Google Patents

Description

  The present invention relates to a control device for a hybrid vehicle equipped with a storage battery.

  As a countermeasure against environmental problems such as global warming, the spread of hybrid vehicles using storage batteries is progressing. As the storage battery, a lead storage battery, a nickel metal hydride battery, a lithium ion battery, or the like is used, but in particular, the use of a lithium ion battery that is particularly excellent in output density and energy density has been increasing.

  In general, a storage battery deteriorates by repeating a charge / discharge cycle. Especially in systems that charge large currents due to regenerative braking over a long period of time, such as railway hybrid vehicles, the battery life will be shorter than expected and adequate performance will be achieved unless appropriate current restrictions are taken into account. It may not be possible to perform, or the battery needs to be replaced sooner than expected.

  As a method for limiting the charge / discharge current, for example, there is a method described in Patent Document 1. The output is limited according to the state of charge of the battery. Moreover, as a control method for suppressing the deterioration of the battery, for example, there is a method described in Patent Document 2. When it is determined that the deterioration rate of the battery is larger than the reference, deterioration suppression control is performed.

JP 2007-151216 A JP 2007-323999 A

  In order to suppress the deterioration of the battery, it is necessary to limit the charging / discharging current. However, if the limitation is applied too much, a desired fuel consumption reduction effect cannot be exhibited as a hybrid vehicle. For this reason, it is desirable to apply the minimum necessary limit so that the battery performance can be exhibited as much as possible and the target life can be achieved. However, such a limiting method has not been sufficiently studied so far.

  For example, in the example in which the output restriction is provided according to the state of charge, a restriction is made to facilitate energy management based on the output characteristics of the battery, and the current restriction is not to suppress deterioration. In addition, the method of applying the deterioration suppression control according to the deterioration rate of the battery is also a restriction that suppresses the deterioration for an application in which the time for one charge / discharge is long and the battery capacity range to be used is wide like a railway vehicle. The method is not considered.

  An object of the present invention is to provide a storage battery control method in which, in a hybrid vehicle equipped with a storage battery, charging and discharging are performed as much as possible while exhibiting a fuel consumption reduction effect while satisfying the target life of the battery.

  In order to solve the above problems, in the control device for a hybrid vehicle, a charge current limit and a discharge current limit corresponding to the state of charge, which are smaller than the current limit value based on the output characteristics of the battery determined by the voltage upper and lower limits, are set. I made it.

  Further, the charge current limit value is smaller as the charge state is higher, and the discharge current limit value is smaller as the charge state is lower.

  In addition, an upper limit value is provided for the amount of charge to be charged in one deceleration operation, and charging is controlled so that the integrated charge value does not exceed the upper limit value.

  Further, the deterioration state of the storage battery is measured and compared with a deterioration characteristic assumed in advance, and the charge current limit value, the discharge current limit value, or the upper limit electric quantity of one charge is changed based on the comparison result. did.

  According to the present invention, for the purpose of suppressing battery deterioration, the charging current and the discharging current are limited according to the state of charge, or the amount of electricity in one charging operation is limited. There is.

1 is an overall configuration diagram of a hybrid vehicle. The block diagram of a battery controller. Explanatory drawing of charging current limitation. Explanatory drawing of discharge current restriction | limiting. Explanatory drawing of an assumed deterioration characteristic.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows an example of a hybrid railway vehicle to which the present invention is applied and its control device. The hybrid vehicle includes an engine 1, a generator 2, an inverter 3, a motor 4, a DC / DC converter 5, and a battery 6, and includes a hybrid controller 11 and a battery controller 12 as control devices.

  As a hybrid system, a series hybrid is assumed. The generator 1 is driven by the engine 1 to generate electric power, and the motor 4 is rotated by the electric power to drive the wheels. The generator 2 also includes a converter that converts AC power into DC power. The inverter 3 drives the motor 4 by converting DC power into AC power. When the vehicle decelerates, the motor 4 is switched to the power generation operation to operate as a regenerative brake.

  The DC / DC converter 5 converts a direct current voltage to control a charging current to the battery 6 or a discharging current from the battery 6. When the vehicle is driven, power is supplied from the battery 6 as needed to assist the output. Accordingly, the output of the engine 1 can be reduced, and the fuel consumption can be reduced. When the vehicle decelerates, the battery 6 is charged with regenerative power output from the motor 4 and the inverter 3.

  The battery 6 has a configuration in which battery cells are combined in multiple series and multiple parallel. For example, when a lithium ion battery is used, the voltage of one cell is about 3.6V, and a DC voltage of about 720V can be obtained by connecting 200 cells in series, for example. When the battery capacity is insufficient, a large-capacity battery can be configured by preparing a plurality of cells connected in series and connecting them in parallel.

  Based on the operation command from the driver and the battery state information (charge state, chargeable / dischargeable power, current limit value) from the driver, the hybrid controller 11 drives and regenerates the motor 4, outputs the engine 1, The charge / discharge output of the battery 6 is determined, and a command is issued to the engine 1, the generator 2, the inverter 3, and the DC / DC converter 5.

  Next, the role of the battery controller 12 will be described in detail. FIG. 2 shows the configuration of the battery controller 12 and the signal flow. The input processing unit 21, the output processing unit 22, the SOC calculation unit 23, the SOH calculation unit 24, the SOH storage unit 25, the current limit value calculation unit 26, and the possible power calculation unit 27 are configured.

  First, the input processing unit 21 receives sensor information such as voltage, current, and temperature installed in the battery 6 and performs necessary processing such as A / D conversion.

  The SOC calculation means 23 calculates a state of charge (SOC) of the battery based on information on voltage, current, and temperature. Various methods have been devised as calculation methods. For example, an open circuit voltage (OCV) of a battery is calculated from data of voltage, current, and internal resistance, and SOC is obtained from a table showing the relationship between OCV and SOC. Alternatively, there is a method of calculating a change in SOC from the ratio between the integrated current value and the battery capacity.

  The SOH calculation means 24 calculates the state of health (SOH) of the battery based on information on voltage, current, and temperature. The deterioration state is defined by an internal resistance increase rate and a capacity decrease rate. In general, it is often estimated by an internal resistance that is easy to measure. The internal resistance can be obtained from the voltage, current and OCV. Assuming that the initial internal resistance is 100%, if the resistance increases due to deterioration, 120% is indicated.

  The SOH storage unit 25 is for storing the deterioration state calculated by the SOH calculation unit 24 together with time information. Thus, it can be seen how the deterioration progresses with time.

  The current limit value calculating unit 26 calculates a current limit value for charging or discharging considering the life based on the state of charge calculated by the SOC calculating unit 23 and current information. Details will be described later.

  The possible power calculation means 27 calculates the maximum possible discharge power that can be output from the battery 6 at that time, or the maximum possible charge power that can be absorbed by the battery 6. When a discharge current is passed through the battery, the battery voltage is a value that is reduced from the OCV by a voltage determined by the product of the internal resistance and the current. In the case of charging, the voltage rises from the OCV by a voltage determined by the product of the internal resistance and current. The maximum and minimum voltages allowed for performance are determined for the battery, and it is necessary to limit the current so as not to exceed the maximum and minimum values. Since the maximum discharge current and the charging current that do not exceed the allowable voltage can be calculated from the OCV and the internal resistance at that time, the possible discharge power and the possible charge power can be calculated based on that.

  Depending on the application of the battery, the maximum current that may be passed may be determined in advance. If the predetermined maximum current is smaller than the above-described maximum current, the possible power is calculated using the smaller value.

  The possible power described above is a value indicating how far the battery can be produced or absorbed, but it is necessary to limit the power further in consideration of the lifetime. If power is calculated using the current limit value calculated by the current limit value calculating means 26, the maximum possible discharge power and possible charge power considering the life can be calculated.

  The output processing unit 22 uses a necessary means such as a communication means for the state of charge calculated by the SOC calculation unit 23, the current limit value calculated by the current limit value calculation unit 26, and the possible power calculated by the possible power calculation unit 27. To the hybrid controller 11.

  Next, the operation of the current limit value calculating means 26 will be described in detail. The current limit value calculating means 26 is for performing current limit in consideration of battery deterioration so as to satisfy the target life.

  The battery deteriorates by repeating charge and discharge. In general, the deterioration proceeds faster as the charge / discharge current increases. Therefore, in order to suppress deterioration, it is necessary to limit the current to a value smaller than the current value determined by the maximum / minimum voltage of the battery. If a cycle life test is performed in advance to determine how much current should be limited in order to achieve the target life, it is possible to limit the current considering the life. The charge / discharge current limit value thus determined is much smaller than the allowable charge / discharge current value determined by the maximum / minimum voltage allowed for the above-described battery performance.

  In general, a storage battery has a property that the lower the state of charge, the easier it is to accept the charge, and the higher the state of charge, the less likely the charge current will flow. Regarding degradation, degradation can be suppressed by reducing the current when the state of charge is high. Similarly, on the discharge side, the higher the state of charge, the larger the discharge current can flow, and the lower the state of charge, the lower the output of the discharge current. When the state of charge is low, it is less likely to deteriorate if the current is reduced.

  Therefore, for example, as shown in FIGS. 3 and 4, the current limit value is changed according to the state of charge SOC. The limit value of the charging current is set to a smaller value as the state of charge SOC is higher. Conversely, the limit value of the discharging current is set to a lower value as the state of charge SOC is lower. By providing a current limit with such characteristics, the progress of deterioration can be effectively suppressed.

  Next, in a method of charging a battery with a large amount of regenerative energy as in a railway, the amount of electricity in one charge / discharge cycle is large, and the capacity range of the battery to be used is also large. In general, it is known that the capacity range of the battery used in one cycle and the number of life cycles are greatly related, and in order to satisfy the target battery life, the electricity charged in one regenerative operation It is effective to limit the amount. Therefore, the charging current values after the start of the charging operation are integrated, and when the predetermined upper limit electricity amount is reached, the charging operation is stopped (the charging current limit value = 0). It is advisable to determine what value the upper limit electric quantity should be in order to achieve the target life by a prior cycle test or the like. Here, the predetermined upper limit electric quantity is a value smaller than the maximum electric quantity allowed in the capacity performance of the battery described above.

  As described above, by limiting the amount of electricity charged in one regenerative operation, it is possible to suppress deterioration of the battery in a charge / discharge cycle with a large amount of electricity, such as for railway use.

  In the above embodiment, the maximum current value and the upper limit electric quantity used in the current limit value calculating means 26 are determined in advance by a cycle test or the like. However, in actual operation, the battery is used under the same conditions as the cycle test. There is no guarantee that it will be used, and the expected degradation may differ from the actual degradation. Therefore, it is also effective to compare the assumed deterioration characteristic with the actual deterioration characteristic and to have the current limit value calculating means 26 have a function of changing the maximum current value and the upper limit electric quantity.

  The assumed deterioration characteristic is determined as shown in FIG. 5, for example, based on the result of a cycle test or the like. In the figure, the horizontal axis represents time (year and month), and the vertical axis represents the battery resistance increase rate. The resistance of the battery increases with time. For example, the time when the resistance reaches 200% is determined as the battery life. Assuming that the target life is 10 years, the expected deterioration characteristics are such that the resistance becomes 200% in 10 years.

  On the other hand, the actual deterioration state is plotted as shown in FIG. 5 using data from the SOH storage unit 25. When the actual deterioration is lower than the assumed deterioration characteristic, the maximum current value and the upper limit electric quantity are increased, and charging / discharging is actively performed to enhance the fuel consumption reduction effect. On the contrary, when the actual deterioration exceeds the assumed deterioration characteristic, the maximum current value and the upper limit electric quantity are reduced to delay the progress of the deterioration.

  Specifically, the difference between the assumed deterioration characteristic and the actual deterioration and the amount of time it has continued are integrated (shaded area in FIG. 5) and set in advance based on the integrated value. The maximum current value and the upper limit electricity amount are changed according to the coefficient.

  Alternatively, a function of presenting the characteristics shown in FIG. 5 may be provided, and the operator may change the value at a timing such as vehicle maintenance.

  In this way, by changing the upper limit value or upper limit electricity amount of the current limit according to the comparison between the assumed deterioration and the actual deterioration, the target life is satisfied in actual operation and the maximum fuel consumption reduction effect is exhibited. be able to.

  In the above embodiment, the railway vehicle is described as an example, but the present invention can also be applied to a hybrid vehicle or the like. Furthermore, it is applicable not only to series hybrids but also to parallel hybrid systems.

1 Engine 2 Generator 3 Inverter 4 Motor 5 DC / DC Converter 6 Battery 11 Hybrid Controller 12 Battery Controller

Claims (1)

A power storage device comprising a plurality of storage batteries; an engine; a generator driven by the engine; an inverter electrically connected to the power storage device and the generator; a motor driven by the inverter; In a hybrid vehicle equipped with
A charge current limit value according to the SOC of the storage battery, and a control device that controls charging / discharging of the power storage device based on a discharge current limit value;
The charging current limiting value, and the discharge current limit performance acceptable maximum voltage of the battery, and the allowable charging current value determined from the minimum voltage, and Ri value smaller der than allowable discharge current value,
The charging current limit value is set to a smaller value as the SOC of the storage battery is higher, and the discharge current limit value is set to a smaller value as the SOC of the storage battery is lower.
When a deterioration state detection device that detects a deterioration state of a storage battery that constitutes the power storage device is provided, a predetermined assumed deterioration characteristic is compared with a detected deterioration state, and the deterioration state is lower than the assumed deterioration characteristic Increasing the maximum current value of the charge current limit value and the discharge current limit value, and the maximum current value of the charge current limit value and the discharge current limit value when the deterioration state exceeds the assumed deterioration characteristic A hybrid vehicle comprising current limit value changing means for reducing the current limit value .

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