JP4017831B2 - Capacitor power storage device for vehicle - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a capacitor power storage device applicable to electric vehicles and hybrid vehicles that use a power storage device as a power source.
[0002]
[Prior art]
In recent years, development of hybrid vehicles including an internal combustion engine (engine) and a motor (motor generator) capable of generating electric power as a power source for vehicle travel has been promoted.
[0003]
2. Description of the Related Art A power storage device using a capacitor (capacitor power storage device) is attracting attention as a power supply device for a hybrid vehicle because it can be rapidly charged and has a long charge / discharge cycle life. In general, even if capacitors with the same rating are used in a capacitor power storage device, due to variations in capacitance, internal resistance, and leakage current, when the charge and discharge are repeated, there is an imbalance in the shared voltage (cell voltage) of each capacitor connected in series And some capacitors are overcharged and damaged. Therefore, a special device for charging up to the rated voltage while preventing damage to the capacitor has been required.
[0004]
Such an apparatus is disclosed in, for example, Japanese Patent Laid-Open No. 6-343225. This power storage device has a constant current source, and has a function of equalizing (initializing) capacitors with a constant voltage (either a rated voltage or a predetermined voltage lower than that) defined by circuit elements in the power storage device. I have.
[0005]
[Problems to be solved by the invention]
However, when this power storage device is used in a hybrid vehicle, periodic charging for equalizing the shared voltage is required, and time for equalization is taken before starting the vehicle. There is a risk of harm. In addition, there is a problem that charging equipment outside the vehicle is required.
[0006]
An object of the present invention is to provide a capacitor power storage device for a vehicle that corrects variations in the shared voltage of each capacitor cell in a normal running state without requiring a special device for equalizing the shared voltage or a special time. That is.
[0007]
[Means for Solving the Problems]
Therefore, a first invention is a capacitor power storage device for a vehicle including an electric motor functioning as a generator as a driving force source, and includes a plurality of capacitor cells connected in series using the electric motor, and each capacitor In the capacitor power storage device in which the variation in the shared voltage of the cell is corrected in the normal running state of the vehicle, a bypass circuit that is provided in parallel to the plurality of capacitor cells and bypasses a part of the charging current of the capacitor cells; Among the plurality of capacitor cells, a means for detecting the maximum voltage Vmax and the minimum voltage Vmin and calculating the voltage difference ΔV by ΔV = Vmax−Vmin, and a predetermined value determined by the calculated voltage difference ΔV A means for determining whether or not the voltage is within Vk, and when the voltage difference ΔV is larger than a specified value Vk , the total voltage Vt of the plurality of capacitor cells connected in series is detected, and the average voltage Vme means for calculating a Vmean = Vt / n with a number n of the plurality of series-connected capacitor cells to an, the determination reference voltage Va using the average voltage Vmean calculated and the specified value Vk Va = Vmean Means for calculating by + Vk / 2 ; means for detecting a capacitor cell having a cell voltage equal to or higher than the determination reference voltage Va among the plurality of capacitor cells; and a capacitor cell having the cell voltage equal to or higher than the determination reference voltage Va Voltage control means for bypassing a part of the charging current until a predetermined time elapses and equalizing the distribution range of the shared voltage of the plurality of capacitor cells to be equal to or less than the specified value Vk. It is provided.
[0008]
According to a second aspect of the present invention, the voltage control means further determines whether or not a predetermined time has elapsed since the bypass has ended, and starts the next bypass when the predetermined time has elapsed. .
[0009]
A third invention includes means for detecting a charge / discharge state of the capacitor power storage device, and the bypass circuit is connected to the capacitor cell only when the capacitor power storage device is in a charged state and the charge current is equal to or lower than a predetermined charge current. A part of the charging current is bypassed.
[0015]
【The invention's effect】
In the first aspect of the present invention, distribution of the shared voltage among the plurality of capacitor cells is performed by bypassing a part of the charging current for a certain period of time for the capacitor cell whose cell voltage is equal to or higher than the determination reference voltage Va. The voltage control means for equalizing the range to be equal to or less than the specified value Vk gradually reduces the cell voltage of the capacitor cell while minimizing the burden on the bypass circuit without requiring a special device or special time. Variations can be corrected.
[0016]
In the second invention, the heat generation and power consumption of the bypass circuit can be further suppressed.
[0017]
In the third invention, by avoiding the bypass process when charging with a large current, it is not necessary to increase the scale and capacity of the bypass circuit, and a simple bypass circuit can be used.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
A hybrid system for a hybrid vehicle according to an embodiment of the present invention will be described with reference to FIG.
[0024]
This hybrid system supplies electric power to an electric motor (motor generator) 1 that also functions as a generator, an inverter 2 for driving the motor generator 1, a hybrid electronic control unit (hybrid ECU) 3, and a vehicle electrical system (each in-vehicle device). A battery 4 and a capacitor power storage device 10 are provided.
[0025]
Motor generator 1 functions as a generator during deceleration operation of the vehicle, regenerates the inertia energy of the vehicle to generate power, and charges capacitor 30 in capacitor power storage device 10. The motor generator 1 functions as an electric motor using the capacitor power storage device 10 as a power source when the vehicle starts and accelerates, and supplies driving torque to the driving system of the vehicle.
[0026]
The hybrid ECU 3 performs overall control of the hybrid vehicle, and transmits acquired vehicle information to the capacitor power storage device 10 in addition to engine control and motor generator control.
[0027]
The capacitor power storage device 10 includes a plurality (m) of capacitor modules 11 (MDL1 to MDLm), a main circuit breaking contactor 14, a main circuit fuse 15, a total voltage detection amplifier 16, a main circuit power supply line (+) 17, a main circuit. A power line (−) 18 and a communication network 21 are provided.
[0028]
A plurality of capacitor modules 11 connected in series constitute a main power source of a power supply system, and a main circuit breaking contactor 14 is connected to a main circuit (from the capacitor module 11 to the inverter 2 by excitation and non-excitation of coils). Turn on / off the high-voltage circuit. The main power supply may be configured by connecting capacitor modules in series and parallel.
[0029]
The capacitor module 11 includes a plurality (n) of capacitor cells 30 and a voltage controller 40. When the main circuit cut-off contactor 14 is turned on by turning on the key switch 5 and the power from the main power supply is supplied to the inverter 2, the motor generator 1 can be driven. Further, when the key switch 5 is turned on, power is supplied from the battery 4 to each circuit such as the hybrid ECU 3.
[0030]
Information on each capacitor module 11 is sequentially transmitted to the hybrid ECU 3 via the communication network 21. Further, the hybrid ECU 3 sends various command signals and vehicle information to each capacitor module 11 via the communication network 21. The communication network 21 is provided with a termination resistor 22.
[0031]
The total voltage detection amplifier 16 converts the voltage of the main power supply (total voltage of the capacitor modules connected in series) into a total voltage signal insulated from the main circuit, and outputs the total voltage signal to the hybrid ECU 3. The hybrid ECU 3 makes various judgments based on the total voltage signal and the like, and gives various commands to each module.
[0032]
Next, a capacitor module according to an embodiment of the present invention will be described in detail with reference to FIG.
[0033]
The capacitor module 11 includes a plurality (n) of capacitor cells 30 (C1 to Cn) and a voltage controller 40 connected in series. Each capacitor cell 30 may be composed of one capacitor, or a plurality of capacitors connected in parallel may be regarded as one capacitor cell. As the capacitor, for example, a large-capacity electric double layer capacitor is used.
[0034]
The voltage controller 40 includes a bypass circuit 50 including a current limiting resistor 41 and a bypass transistor 42, an OR circuit 43, a comparator 44, a bypass reference voltage generating means 45, a cell voltage detection switching circuit 46, an insulation amplifier 47, and an AD conversion circuit 48. A bypass switching circuit 49, a switching signal output circuit 51, a data communication circuit 52, a central processing unit (CPU) 53, a read-only memory (ROM) 54, and a random access memory (RAM) 55.
[0035]
The comparator 44 compares the shared voltage of the capacitor cell with a constant bypass reference voltage. When the shared voltage of the capacitor cell 30 becomes equal to or higher than the voltage set by the bypass reference voltage generating means 45 by charging, a bypass command is output. The bypass reference voltage is set near the withstand voltage (maximum usable voltage) of the capacitor cell, for example, 2.7V.
[0036]
The bypass transistor 42 conducts the bypass circuit 50 when a base voltage is applied by the ON output of the OR circuit 43. The bypass command turns on the bypass transistor 42 via the OR circuit 43 and bypasses a part of the charging current of the capacitor cell. This bypass determination is made for each capacitor cell. In this way, the voltage of each capacitor cell can be limited and equalized to the maximum usable voltage.
[0037]
The capacitor power storage device of the present invention includes not only a circuit that equalizes the maximum voltage but also a circuit that equalizes the voltage of the capacitor cell with an arbitrary voltage. This will be described below.
[0038]
The cell voltage switching circuit 46 sequentially switches the capacitor cell whose voltage is read by the AD conversion circuit 48 based on the signal from the switching signal output circuit 51. A digitized voltage signal is taken into the CPU 53 from the AD conversion circuit 48. At this time, the main power supply system circuit including the capacitor cell and the AD conversion circuit 48 are insulated by the insulation amplifier 47.
[0039]
The CPU 53 determines bypass based on the vehicle information acquired from the data communication circuit 21 and the voltage of each capacitor cell in the module. Further, the CPU 53 sends a switching signal to the bypass switching circuit 49 via the switching signal output circuit 51. Based on this switching signal, the bypass switching circuit 49 outputs a bypass command to a cell that needs to be bypassed. The bypass command turns on the transistor 42 via the OR circuit 43 that takes an OR with the bypass command from the comparator 44. In this way, a bypass process in which a part of the charging current of the capacitor cell flows through the bypass circuit 50 is performed.
[0040]
A specific bypass control routine executed by the central processing unit CPU 53 in the voltage controller will be described below based on the flowcharts of FIGS. In addition,
This bypass control routine is executed based on a program stored in the ROM 54.
[0041]
First, a basic routine of bypass control will be described with reference to FIG. This routine is executed at predetermined time intervals by timer interrupt processing or the like.
[0042]
First, in step S <b> 1, the CPU 53 acquires information on the charge / discharge state of the capacitor power storage device 10 from the communication network 21. The information on the charge / discharge state can be detected by the hybrid ECU 3 via, for example, the inverter 2 and sent to the communication network 21.
[0043]
Next, in step S2, it is determined whether or not the capacitor power storage device 10 is in a charged state and the charging current is equal to or less than a predetermined current value. If it is determined that the charging state is not a large current (that is, the charging current is equal to or less than the predetermined current value), the bypass determination process and the bypass command process in step S3 are executed, and then the process ends. If it is not in a charged state, or if it is in a charged state with a charging current larger than a predetermined current value, the routine is terminated without performing bypass processing. By avoiding the bypass process at the time of charging with a large current, it is not necessary to increase the scale and capacity of the bypass circuit, and a simple bypass circuit can be used.
[0044]
With reference to FIG. 4, the subroutine of step S3 will be described. Here, bypass determination processing and bypass command processing are executed.
[0045]
First, in step S11, a determination reference voltage Va used when determining whether or not to perform bypass processing for each cell is determined. The determination reference voltage determination routine is shown in the flowchart of FIG.
[0046]
In step S12, when starting bypass determination of the first to nth capacitor cells (C1 to Cn), 1 is set to the variable i (1 (i (n)) indicating the capacitor cell number.
[0047]
When the voltage V (i) of the i-th capacitor cell is smaller than the determination reference voltage Va in step S13, the process proceeds to step S17, the bypass command output is turned off, and no bypass is performed. When the voltage V (i) of the capacitor cell is equal to or higher than the determination reference voltage Va, the process proceeds to step S14, and it is determined whether or not a predetermined time Ta has elapsed after the bypass of the i-th cell is completed. If the predetermined time Ta has elapsed, the process proceeds to step S15 to start bypassing.
[0048]
In this manner, the heat generation and power consumption of the bypass transistor 42 can be suppressed by setting the time interval for performing the bypass at a predetermined time Ta.
[0049]
If the determination is NO in step S14, bypass is not performed, the process proceeds to step S17, and the bypass command is turned off. Thereafter, in step S18, whether all the cells have been processed (that is, whether i = n) is determined. to decide.
[0050]
In step S15, on the basis of the bypass command from the bypass switching circuit 49, bypassing of the charging current of the i-th cell (Ci) is started.
[0051]
Next, in step S16, it is determined whether or not this bypass has been executed for a certain time Tb. If a certain time Tb has elapsed since the bypass started, the bypass command is turned off in step S17, and the bypass is terminated.
[0052]
If the predetermined time Tb has not elapsed in step S16, the process proceeds to step S18 to determine whether or not the processing of all cells has been completed. If the determination in step S18 is negative, the process proceeds to step S19, 1 is added to i indicating the cell number, and then the process returns to step S13 to determine whether the next (i + 1) -th cell is equal to or higher than the determination reference voltage Va. To do.
[0053]
FIG. 5 shows a bypass determination reference voltage determination routine. First, in step S21, 1 is set to the cell number i to determine the maximum voltage and the minimum voltage of the capacitor cell.
[0054]
Next, in step S22, detection processing of the minimum voltage Vmin and the maximum voltage Vmax of the capacitor cell is performed as follows.
[0055]
First, it is determined whether or not the cell voltage V (i) of the i-th capacitor cell is equal to or lower than the minimum voltage Vmin. When the voltage is equal to or lower than the minimum voltage, the minimum voltage Vmin is set as the cell voltage V (i) (that is, Vmin = V (i)). If it is not lower than the lowest voltage, it is determined whether or not the i-th cell voltage V (i) is higher than the highest voltage Vmax. When the voltage is equal to or lower than the maximum voltage, the maximum voltage Vmax is set as the cell voltage V (i) (that is, Vmax = V (i)). When i = 1, the lowest voltage Vmin and the highest voltage Vmax are both the first cell voltage V (1).
[0056]
Subsequently, in step S23, it is determined whether or not all cells have been completed. If not, the cell number i is incremented by 1 in step S24, and the process returns to step S22 to detect the lowest voltage and the highest voltage. When all the cells are completed, a difference ΔV between the highest voltage and the lowest voltage is calculated (ΔV = Vmax−Vmin) in step S25.
[0057]
Next, in step S26, it is determined whether or not the voltage difference ΔV is within a specified value Vk. If it is within the specified value Vk, this routine is terminated. If larger than the specified value Vk, the total voltage Vt of the module is detected in step S27, and then the average voltage Vmean of the cell is calculated by dividing the total voltage Vt of the module by the number n of capacitor cells in the capacitor module in step S28. (Vmean = Vt / n). In step S28, the average voltage Vmean of the capacitor cells may be obtained by dividing the total voltage of the capacitor power storage device detected by the hybrid ECU by the total number of capacitor cells in the capacitor power storage device.
[0058]
Next, in step S29, the cell reference voltage Va is added by adding half of the cell average voltage Vmean and the specified value Vk (Va = Vmean + Vk / 2). Thereafter, this routine is terminated.
[0059]
If the voltage difference ΔV is smaller than the specified value Vk in step S26, the routine returns.
[0060]
Next, a method for determining a capacitor cell to be corrected in the above bypass control will be described in more detail with reference to FIG. Before the bypass process is performed, the cell voltages of the capacitor cells in the module are distributed around the average voltage Vmean as shown in the lower diagram of FIG. However, in the above-described bypass processing, a charging current for a capacitor cell having a voltage higher than Vk / 2 with respect to the average voltage Vmean (that is, a cell having a voltage higher than Vmean + Vk / 2) partially passes through the bypass circuit. Flowing. Therefore, by repeatedly performing the bypass, the voltage of the cell is equalized with the passage of time during charging. Finally, as shown in the upper diagram of FIG. 6, the cell voltage variation ΔV (= Vmax−Vmin) can be maintained under a certain condition (within Vk).
[0061]
When the value of the specified value Vk is set to 0.1 V, for example, each capacitor cell can be charged to the maximum voltage almost simultaneously. Therefore, the capacitor power storage device can be used in the vicinity of the maximum voltage, and can be operated with high efficiency.
[0062]
FIG. 7 shows how voltage variations are corrected within a specified value Vk by performing correction by bypass. When the voltage of the capacitor cell reaches the determination reference voltage Va, part of the charging current starts to flow through the bypass circuit, and the increase in the voltage of the capacitor cell is suppressed.
[0063]
After a certain time Tb has elapsed, the bypass ends, and then the voltage of the capacitor cell rises with time, with the same slope as when no bypass is performed. Although the case where the bypass is performed only once is shown here, there is a case where a constant bypass time Tb and a bypass interval Ta are provided, and the variation in the shared voltage is gradually corrected.
[0064]
As described above, the capacitor power storage device of the present invention has a function of detecting the voltage of each capacitor cell and equalizing the voltage of the capacitor cell with an arbitrary voltage. Therefore, it is possible to charge the battery voltage by correcting the variation in the voltage shared by each capacitor cell at any time in the running state of the vehicle without requiring a special device or a special time. As a result, it is possible to charge up to the maximum usable voltage of the capacitor cell without flowing an excessive current through the bypass circuit, so that the stored energy proportional to the square of the voltage can be used effectively.
[0065]
In the present invention, a circuit for equalizing to one bypass reference voltage and two circuits for detecting a voltage for each cell and equalizing with an arbitrary voltage are provided, but only with a circuit for equalizing with an arbitrary voltage, Equalization may be performed. In other words, the circuit for limiting the voltage of the capacitor cell to the maximum voltage may be omitted, and the charge to the capacitor cell may be limited to the maximum voltage by performing normal charge / discharge control for the motor generator.
[0066]
The present invention is not limited to the above embodiment. It is obvious that various changes can be made within the scope of the technical idea.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a hybrid system according to an embodiment of the present invention.
FIG. 2 is a configuration diagram of a capacitor module of the capacitor power storage device according to the embodiment of the present invention.
FIG. 3 is a flowchart showing a basic routine of bypass control.
FIG. 4 is a flowchart showing a subroutine of bypass determination processing and bypass command processing.
FIG. 5 is a flowchart showing a determination reference voltage determination routine.
FIG. 6 is a diagram illustrating a method for determining a capacitor cell to be corrected in a charging bypass.
FIG. 7 is a diagram illustrating a state in which a variation in shared voltage is corrected.
[Explanation of symbols]
1 Motor generator 2 Inverter 3 Hybrid ECU
4 Battery 10 Capacitor power storage device 11 Capacitor module 21 Communication network 30 Capacitor cell 40 Voltage controller 45 Bypass reference voltage generating means 46 Cell voltage detection switching circuit 47 Insulation amplifier 48 AD conversion circuit 49 Bypass switching circuit 50 Bypass circuit 51 Switching signal output circuit 53 Central processing unit (CPU)

Claims (3)

A capacitor power storage device of a vehicle including an electric motor functioning as a generator as a driving force source , comprising a plurality of capacitor cells connected in series using the electric motor, and variations in the shared voltage of each capacitor cell in the capacitor power storage device to be corrected in the normal running state,
A bypass circuit that is provided in parallel to the plurality of capacitor cells and bypasses a part of the charging current of the capacitor cells;
Means for detecting the highest voltage Vmax and the lowest voltage Vmin among the plurality of capacitor cells, and calculating the voltage difference ΔV by ΔV = Vmax−Vmin ;
Means for determining whether or not the calculated voltage difference ΔV is within a predetermined value Vk ;
When the voltage difference ΔV is larger than the specified value Vk, the total voltage Vt of the plurality of capacitor cells connected in series is detected, and the average voltage Vmean is used using the number n of the plurality of capacitor cells connected in series. Means to calculate by Vmean = Vt / n ;
Means for calculating the determination reference voltage Va by Va = Vmean + Vk / 2 using the calculated average voltage Vmean and the specified value Vk ;
Means for detecting a capacitor cell having a cell voltage equal to or higher than the determination reference voltage Va among the plurality of capacitor cells ;
Said bypassing to said bypass circuit for the capacitor cell is the cell voltage is determined the reference voltage Va than predetermined time elapses part of the charging current, the distribution range of the shared voltage of the plurality of capacitor cells or less than the specified value Vk and voltage control means for equalizing the equalization so as to,
A capacitor power storage device.   2. The voltage control unit according to claim 1, wherein the voltage control unit further determines whether or not a predetermined time has elapsed since the bypass has ended, and starts the next bypass when the predetermined time has elapsed. Capacitor power storage device.   Means for detecting a charge / discharge state of the capacitor power storage device;
  2. The capacitor according to claim 1, wherein the bypass circuit bypasses a part of the charging current of the capacitor cell only when the capacitor power storage device is in a charged state and the charging current is equal to or lower than a predetermined charging current. Power storage device.

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