JP3606779B2 - Electric vehicle power system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a power supply system for an electric vehicle or a hybrid electric vehicle using an electric double layer capacitor as a main power storage device.
[0002]
[Prior art]
Conventionally, chemical batteries have been applied to power storage devices for electric vehicles or hybrid electric vehicles. However, since chemical batteries have a short charge / discharge cycle life and poor efficiency during high output operation, electric double layer capacitor batteries are used. Has been.
FIG. 5 shows a basic configuration example of a power supply system in which an electric double layer capacitor is applied to a main power storage device of a hybrid electric vehicle. In the figure, 1 is an engine, 2 is a generator, 3 is a rectifier, 4 is a main power storage device, and 5 is an inverter that drives a vehicle drive motor 6. From the engine 1 to the vehicle drive motor 6 is a power train. 7 is a DC-DC converter for charging the auxiliary power storage device 8, and 9 is an auxiliary machine. The main power storage device 4 is configured by connecting a plurality of electric double layer capacitor cells 41, 42, 43,. In addition, illustration about the drive mechanism after the electric motor 6 is abbreviate | omitted.
[0003]
The illustrated system is a power supply system for a series hybrid electric vehicle, and charges part or all of the electric power generated by the engine 1 and the generator 2 to the main power storage device 4. The electric power generated by the engine 1 and the generator 2 and the electric power of the main power storage device 4 are used to drive the electric motor 6 through the inverter 5 to run the vehicle. At the time of acceleration, the electric motor 6 is accelerated and driven through the inverter 5 with the electric power of the generator 2 and the electric power of the main power storage device 4 or only the main power storage device 4. During regenerative braking, braking power generated in the electric motor 6 is regenerated to the main power storage device 4 via the inverter 5. The DC-DC converter 7 is a charger that charges the auxiliary power supply 8 from the main power storage device 4 of the powertrain system, and corresponds to an alternator of the engine vehicle.
[0004]
The power supply system for an electric vehicle not equipped with a generator has a system configuration in which the engine 1, the generator 2, and the rectifier 3 are removed from FIG. To do.
FIG. 6 shows a circuit configuration of the DC-DC converter 7 of FIG. In the figure, 70 and 71 are semiconductor switches, 72, 73, 74 and 75 are diodes, 76 is a transformer, 77 is a current smoothing reactor, and 78 and 79 are voltage smoothing capacitors. Since this circuit system is a known circuit system called a two-stone forward type, its operation description is omitted.
[0005]
As described above, the main power storage device 4 is repeatedly discharged during vehicle acceleration and charged during braking, and the number of times reaches tens of thousands of times. The main power storage device for electric vehicles must be able to withstand this number of charge / discharge cycles. The power storage device using the electric double layer capacitor described above has this performance, and can be said to be an excellent power storage device for an electric vehicle.
The electric double layer capacitor battery shown in FIG. 5 is also configured by connecting a large number of electric double layer capacitor cells in series in the same manner as an assembled battery in which a number of conventional chemical secondary batteries are connected in series. Is a system in which an electric double layer capacitor is replaced.
[0006]
The stored energy of the electric double layer capacitor is proportional to the square of the capacitor voltage. In other words, when used as a DC power supply, the voltage of the electric double layer capacitor decreases as the energy consumption increases. Using 75% of the energy, the voltage drops to ½. In the power supply system shown in FIG. 5, the input voltage of the inverter varies greatly depending on the power consumption. In particular, in the case of an electric vehicle, when the voltage is lowered, the vehicle performance in the middle and high speed range is greatly lowered. Therefore, in practice, as shown in FIG. 7, a method of making the input voltage to the inverter 5 constant by inserting a chopper 44 between the capacitor battery 4 which is the main power storage device and the inverter 5 or shown in FIG. As described above, a method has been proposed in which the capacitor battery is divided into a plurality of blocks, and the blocks are switched by switches to reduce the change in the input voltage of the inverter.
[0007]
That is, in FIG. 8, reference numerals 10, 11, and 12 denote capacitor battery blocks, each of which has a required number of capacitor cells 100, 110, and 120 connected in series. Reference numeral 13 denotes a capacitor block connection selector switch. FIG. 9 is a diagram showing details of the selector switch unit 13 of FIG. Reference numerals 130, 131, and 132 are bidirectional flow-type switches, and normally semiconductor switches are used. FIG. 10 shows the behavior of the inverter input voltage in the case of the power supply system of FIG. In the operation mode I, the switch 130 is closed and the switches 131 and 132 are opened. Then, the capacitor battery becomes the voltage of the capacitor battery block 10. In the operation mode II, the switch 131 is closed and the switches 130 and 132 are opened. Then, the capacitor battery becomes a series of capacitor battery blocks 10 and 12. In the operation mode III, the switch 132 is closed and the switches 130 and 131 are opened. Then, the capacitor battery becomes a series of capacitor battery blocks 10, 11 and 12.
[0008]
[Problems to be solved by the invention]
Incidentally, as described above, the electric double layer capacitor is different from the chemical battery in that the stored energy is proportional to the square of the voltage. That is, the capacitor voltage increases as the stored energy increases. Moreover, in the power supply system shown in FIGS. 5-9, the electric double layer capacitor is used similarly to the assembled battery of the conventional chemical secondary battery. That is, a capacitor battery in which a large number of capacitor cells are connected in series is used as one capacitor battery. A large number of electric double layer capacitors connected in series will cause variations in the capacitor cell voltage if they are left for a long time in a charged state or repeatedly charged and discharged, so when applied to an electric vehicle that repeatedly charges and discharges, this voltage Due to the variation, some of the capacitor cells become overvoltage, leading to failure of the capacitor battery.
[0009]
For an electric vehicle, a failure of a power storage device is a serious failure. Therefore, when an electric double layer capacitor battery is applied to an electric vehicle, it is highly required that the capacitor cell does not become overvoltage. Next, the voltage behavior of the electric double layer capacitor cells connected in series will be described. An internal equivalent circuit of the electric double layer capacitor cell shown in FIG. 5 is expressed as shown in FIG. FIG. 11 shows the capacitor cell 41 of FIG. The electric double layer capacitor cell 41 can be regarded as equivalently having capacitor elements 410a, 411a, 412a,... Connected in parallel via resistors 410b, 411b, 412b,. Further, it can be considered that discharge resistors 410c, 411c, 412c,... Equivalently representing self-discharge for each capacitor cell are connected in parallel to the capacitor elements 410a, 411a, 412a,.
[0010]
Here, when an electric double layer capacitor battery is applied to a main power storage device for an electric vehicle, a plurality of electric double layer capacitor cells are connected in series, but the circuit constants for each capacitor cell are not all the same. A problem occurs. The contents will be described below. If the capacitor battery is left in a charged state for a long time, each capacitor cell is self-discharged by an internal self-discharge resistor. The voltage behavior of this series-connected capacitor cell will be described with reference to FIG. In order to simplify the description, a case where two are connected in series will be described.
[0011]
In FIG. 12, at time t = T0 in a state where the two capacitor cells C1 and C2 are uniformly charged to the voltage V1 (the combined voltage is V0), the capacitor battery is left open and left. When the capacitor cell is self-discharged until time t = T1, the voltage values of the capacitor cells C1 and C2 at time t = T1 differ due to the difference in self-discharge resistance value. Next, charging is performed from time t = T1 until t = T2 at which the capacitor combined voltage reaches the specified value V0. Both capacitor cells rise to approximately the same voltage ΔV / 2. At time t = T2, the voltage of the capacitor cell C1 becomes higher than that of the capacitor cell C2, but does not reach the overvoltage level V2.
[0012]
At time t = T2, the capacitor battery is again opened and left. Both capacitor cells begin self-discharge. The variation in the capacitor cell voltage at time t = T3 is further enlarged than that at time t = T1. At time t = T3, charging is performed again until time t = T4 when the capacitor cell composite voltage reaches the specified value V1. In response to the variation in the capacitor cell voltage at the time t = T3, the voltage variation at the time t = T4 further expands compared to the voltage at the time t = T2, and the voltage of the capacitor cell C1 reaches the overvoltage level V2. And it will develop to the failure of the capacitor cell. Although FIG. 12 shows the case of opening and self-discharging at time t = T1, T2, the same phenomenon occurs when power is supplied to the load for discharge. In this case, the discharge time is shorter than in the case of self-discharge.
[0013]
[Means for Solving the Problems]
Therefore, as a countermeasure against these problems, conventionally, when a plurality of electric double layer capacitor cells are connected in series and used as a battery, a voltage equalization circuit is provided for each capacitor cell so that even one of the series capacitor cells does not become an overvoltage. A method is adopted in which the capacitor cell voltages are equalized at an appropriate timing before the capacitor cells are overvoltaged. FIG. 13 shows this method. As in the case of FIG. 12, the case of serial number 2 is shown. When the capacitor cell voltage V reaches the reference voltage V1, the voltage equalization circuits 4a and 4b are operated to divide a part of the charging current I0 as ib to the voltage equalization circuits 4a and 4b. As the capacitor cell voltage increases, the flow rate is increased by this amount. When the capacitor cell voltage reaches V2, the current ic to the capacitor cell is made zero.
[0014]
Thus, by monitoring the capacitor cell voltage and bypassing the charging current above the specified voltage, the voltage of the capacitor cell cannot be higher than V2. In the voltage equalization circuit, a power loss of the product of V2 and I0 occurs, but V2 is 2 to 3 V and I0 is set to several A, so the generated power is about several W. In FIG. 12, when the voltage of the capacitor cell C1 reaches V2, the voltage equalization circuit operates and the voltage is kept at V2. If the charging is further continued, the capacitor cell C2 similarly becomes V2 by the operation of the voltage equalizing circuit, the voltage variation of the capacitor cell becomes almost zero, and the charging voltage of all the series capacitor cells becomes the same V2.
[0015]
In this way, when the regular load power is discharged after all the capacitor cells have the same voltage, the variation in the capacitor voltage increases as the discharge cycle and time elapse. The above-described equal charge is performed later or after an appropriate discharge / charge cycle, and the variation in the capacitor cell voltage is corrected to almost zero. By using such a method, in the present invention, capacitor cells connected in series are not exposed to overvoltage, and a long-life capacitor battery is realized.
[0016]
That is, according to the present invention, a sufficient charge / discharge cycle can be obtained by charging serially connected electric double layer capacitor cells with a low-power external power source and aligning the cell voltages with a cell overvoltage protection circuit connected to each cell. In addition, the electric vehicle is made paying attention to an auxiliary power storage device for auxiliary equipment.
Specifically, the total number of capacitor cells is charged to a uniform voltage for each electric double layer capacitor battery divided into a plurality of blocks from the auxiliary power storage device via a DC-DC converter (hereinafter referred to as full charge). It is what I did. Further, the DC-DC converter for the auxiliary power storage device and the DC-DC converter for full charge are the same DC-DC converter and are of a bidirectional type.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a first embodiment of the present invention, which corresponds to claims 1 and 2 , and is a system that charges all capacitor cells using an auxiliary power storage device of an automobile as a power source. In FIG. 1, reference numeral 5 denotes an inverter that drives the vehicle drive motor 6. Reference numeral 7 denotes a DC-DC converter that charges the auxiliary power storage device 8, and reference numeral 13 denotes an electric double layer capacitor battery block connection switching circuit.
[0018]
Reference numerals 14, 15, and 16 are all-capacitor charging DC-DC converters that charge the capacitor battery blocks 10, 11, and 12 using the power of the auxiliary power storage device 8. Since the number of capacitor cells connected in series in the capacitor battery blocks 10, 11, and 12 are different from each other, the output (capacitor side) voltages of the DC-DC converters 14, 15, and 16 are also different from each other.
[0019]
FIG. 2 shows a circuit configuration example of the DC-DC converter 14 of FIG. The DC-DC converter 14 is an insulated chopper, and the same components as those in FIG. In FIG. 2, 140 is a semiconductor switch, 141, 142, 143, 144, and 145 are diodes, 146 is a transformer, 147 is a current smoothing reactor, and 148 and 149 are voltage smoothing capacitors. The voltage on the output side (capacitor side) is changed by changing the turns ratio of the transformer 146. Since the operation of the illustrated insulated chopper is known, the description thereof is omitted here. Further, since the DC-DC converters 15 and 16 of FIG.
[0020]
FIG. 3 shows a second embodiment of the present invention, which corresponds to the third aspect of the present invention. In other words, this is a circuit configuration example of a DC-DC converter having both the functions of the DC-DC converters 14, 15, 16 shown in the invention of FIG. 1 and the function of the DC-DC converter 7. In FIG. 3, the same components as those in FIG. In FIG. 3, 9 is an auxiliary machine driven by the auxiliary power storage device 8 , 17 , 18 , and 19 are bidirectional operation type DC-DC converters, and the capacitor battery blocks 10, 11, 12 are connected to the auxiliary power storage device 8. A charging function and a charging function from the auxiliary power storage device 8 to the capacitor battery blocks 10, 11, and 12 are provided.
[0021]
FIG. 4 is a circuit configuration example of the DC-DC converter 17 of FIG. In FIG. 4, the same components as those in FIG. In FIG. 4, 170, 171, 172, 173 are semiconductor switches, 170a, 171a, 172a, 173a, 174, 175 are diodes, and the semiconductor switches 170, 171, 172, 173 are diodes 170a, 171a, 172a, 173a is connected in reverse parallel as shown. 176 is a transformer, 177 is a current smoothing reactor, and 178 and 179 are voltage smoothing capacitors.
[0022]
Next, the operation of the DC-DC converter 17 of FIG. 4 will be described. When the auxiliary power storage device 8 is charged from the capacitor battery block 10, the semiconductor switches 170 and 171 are turned off and the switches 172 and 173 are switched. The circuit configuration in this case is equivalent to the conventionally known two-stone forward type shown in FIG. Next, when charging the capacitor battery 10 from the auxiliary power storage device 8, the semiconductor switches 172 and 173 are turned off, and 170 and 171 are switched. The circuit configuration in this case is equivalent to that shown in FIG. However, the semiconductor switch 171 performs the same operation as the diode 141 in FIG.
[0023]
3 is the same as that of the DC-DC converter 17 of FIG. 4 and the description thereof is omitted.
Although not shown, a cell overvoltage protection circuit (voltage equalization circuit) as shown in FIG. 13 is connected to each capacitor cell of the capacitor battery blocks 10, 11 and 12, and each capacitor cell is charged at the time of charging. The cell voltages are aligned.
[0024]
【The invention's effect】
As described above, the present invention divides a capacitor battery in which electric double layer capacitor cells are connected in series into a main power storage device of an electric vehicle or a hybrid electric vehicle into a plurality of blocks, and the blocks are connected in series with a bidirectional energization switch. In the power supply system in which the number is switched, the capacitor cell of each battery block is configured to be used by constantly charging the capacitor cell voltage from the in-vehicle auxiliary power storage device via the DC-DC converter. The following effects can be obtained.
[0025]
(1) Since the capacitor cells connected in series do not become overvoltage, they operate stably as a battery, and high reliability is obtained.
(2) Since the electric double layer capacitor battery can be applied to the main power storage device of the electric vehicle, the battery has a long life, and a practical electric vehicle and hybrid vehicle can be realized.
(3) The DC-DC converter combines the charging of the auxiliary power storage device from the main battery so that the auxiliary power storage device is charged from the capacitor battery block. Can be diverted. Thereby, a low-priced and practical electric vehicle or hybrid electric vehicle can be realized.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a power supply system showing a first embodiment of the present invention.
FIG. 2 is a detailed explanatory diagram of a main part of FIG. 1;
FIG. 3 is a configuration diagram of a power supply system showing a second embodiment of the present invention.
4 is a detailed explanatory diagram of a main part of FIG. 3;
FIG. 5 is a diagram showing a conventional power supply system.
6 is a detailed explanatory diagram of a main part of FIG. 5;
FIG. 7 is a diagram showing a conventional power supply system.
FIG. 8 is a diagram showing a conventional power supply system.
FIG. 9 is a detailed explanatory diagram of a main part of FIG. 8;
10 is an explanatory diagram of the operation in FIG. 9. FIG.
FIG. 11 is a diagram showing an equivalent circuit of an electric double layer capacitor.
FIG. 12 is an explanatory diagram showing a change in voltage of the electric double layer capacitor.
FIG. 13 is a diagram for explaining the operation of a series-connected electric double layer capacitor.
[Explanation of symbols]
1 Engine 2 Generator 3 Rectifier 4 Main power storage device (electric double layer capacitor battery)
4a, 4b Voltage equalization circuit 5 Inverter 6 Vehicle drive motor 7 Auxiliary power storage device charging DC-DC converter 8 Auxiliary power storage device 9 Auxiliary devices 10-12 Electric double layer capacitor battery block 13 Electric double layer capacitor battery block connection switching circuit 14 -16 Capacitor battery block charging DC-DC converter 17-19 Bidirectional DC-DC converters 41-43, 100, 110, 120 Electric double layer capacitor cell 44 Chopper 70, 71, 140, 170-173 Semiconductor switch 73- 75, 141-144 Diodes 170a-173a, 174, 175 Diodes 76, 146, 176 Transformers 77, 147, 177 Current smoothing reactors 78, 79, 147, 148, 178, 179 Voltage smoothing capacitors 130-132 Bidirectional energization type Sui H 410a to 412a Capacitor element 410b to 412b Internal resistance 410c to 412c Self-discharge resistance

Claims (7)

An electric vehicle that drives a vehicle with electric power from an in-vehicle engine generator or electric power from an in-vehicle main power storage device, and a plurality of capacitor battery blocks in which a plurality of electric double layer capacitor cells are connected in series or in series and parallel are combined through a switching circuit. A main power storage device, an auxiliary power storage device for vehicle auxiliary equipment, and a DC-DC converter connected between the main power storage device and the auxiliary power storage device to charge the auxiliary power storage device with the power of the main power storage device. In the electric vehicle power system,
Means for monitoring the capacitor cells of the capacitor battery block and determining whether or not it is the timing to start full charge;
A full-charging DC-DC converter that charges the capacitor cells using the power of the auxiliary power storage device until the total number or a predetermined number reaches a predetermined voltage when it is determined that the total charging start timing is reached. When,
Equipped with a,
A power supply system for an electric vehicle, characterized in that the DC-DC converter for full charge is provided for each capacitor battery block . In the electric vehicle power supply system according to claim 1,
A power system for an electric vehicle, characterized in that a DC-DC converter for an auxiliary power storage device and a DC-DC converter for full charge are the same DC-DC converter and are bidirectional . In the electric vehicle power supply system according to claim 1 or 2,
An all-electric charging start timing determining means determines the start timing when the voltage of the capacitor battery block falls below a predetermined value . In the electric vehicle power supply system according to claim 1 or 2 ,
The complete charging start timing determining means measures an elapsed time after the last complete charging of the capacitor battery block, and determines the start timing when a predetermined time is reached. . In the electric vehicle power supply system according to claim 1 or 2 ,
Start timing determining means for all assortment charging measures the number of charge-discharge cycles of the previous full assortment After charging the capacitor battery blocks, an electric vehicle, characterized in that determined to be in reach Once you start timing a predetermined number of times Power system. In the electric vehicle power supply system according to claim 1 or 2 ,
An all-electric charging start timing determining means determines based on a value obtained by combining an elapsed time after the last all-complete charging of a capacitor battery block and the number of charge / discharge cycles . In the electric vehicle power supply system according to any one of claims 1 to 6 ,
A power system for an electric vehicle, wherein a voltage equalization circuit is connected to each capacitor cell of the capacitor battery block .

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