JPH0340062Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] This invention relates to a power supply device for an artificial satellite.

[Conventional technology]

In artificial satellites, solar cells are generally used as the main power source, and secondary batteries such as nickel cadmium (NiCd) storage batteries are used as storage batteries.

During sunshine, power is supplied from the solar cell and the storage battery is charged, and during shade, power is supplied by discharging from the storage battery. In artificial satellites such as communication satellites, which use almost the same amount of power regardless of whether it is sunny or in the shade, there is a limit to the capacity of each storage battery, so multiple storage batteries are generally used in parallel to meet the required power. It's covered. Furthermore, when the satellite load is a large amount of power, a method is often adopted in which the discharged power of the storage battery is directly supplied to the power bus line without going through a converter or regulator due to advantages such as efficiency and weight.

An example of the configuration of a conventional power supply device for this type of satellite is shown in FIG. For convenience of explanation, an example in which two storage batteries are used is shown.

In the figure, 1 is a solar cell that generates electricity by converting solar energy into electrical energy during sunlight, 2 is a power bus line that supplies electricity, and 3
4 is a satellite load, 4 is a return line, and 5 is an upper limiter for the voltage of the power bus line (bus voltage), and is a shunt regulator that stabilizes the bus voltage during sunshine. 6 and 7 are for example
It is a secondary battery storage battery such as a NiCd storage battery.
8 and 9 are cells (unit batteries), and the storage battery 6 is
and 7 are usually the same number of cells 8 of the same type.
and a cell 9 are connected in series. Reference numerals 10 and 11 indicate backflow prevention diodes connected to the discharge paths of the storage battery 6 and storage battery 7, respectively. 12 is a charging control circuit that supplies charging current to the storage battery 6 and the storage battery 7.

The conventional satellite power supply device is configured as described above, and during sunshine, power is supplied from the solar cell 1 to the satellite load 3, and the bus voltage of the power bus line 2 at that time is equal to Guilulator 5
stabilized by Further, the storage battery 6 and the storage battery 7 are charged by controlling a part of the electric power generated by the solar cell 1 to a required charging current by a charging control circuit 11. When the sun enters the shade, power is no longer supplied from the solar cell 1, and instead, power is supplied from the storage battery 6 and the storage battery 7.
The discharge current from diode 10 and diode 1
1 to the power supply bus line 2, and the discharged power is supplied to the satellite load 3. The bus voltage of the power supply bus line 2 in the shade follows the storage battery voltage when the storage batteries 6 and 7 are discharged. Since the storage battery voltage is the product of the average cell voltage and the number of series cells, normally, in order to keep the storage battery in a sufficiently charged state during sunshine, the storage battery voltage during charging should exceed the upper limit of the output voltage of the charging control circuit 11. cell 8 so as not to exceed
The number of series stages of cells 9 is determined.

[Problem that the invention attempts to solve]

Generally, secondary batteries used in artificial satellites have a lifespan that deteriorates like NiCd batteries. In particular, the discharge capacity of a storage battery is a major factor that affects its lifespan. For example, the relationship between the depth of discharge (percentage of the discharged capacity relative to the rated capacity) and the lifespan of NiCd storage batteries is shown in FIG. 3, and it is widely known that the longer the depth of discharge becomes, the shorter the lifespan becomes. Therefore, in general, the allowable depth of discharge is determined according to the design life of the artificial satellite, and storage batteries are operated so as not to exceed the allowable depth of discharge. Therefore, when using multiple storage batteries in parallel, it is important to balance the discharge current of each storage battery so that it is approximately the same so that the load does not concentrate on a specific storage battery and prematurely deteriorate its life. .

However, in the conventional configuration shown in FIG. 2, when the storage batteries 6 and 7 are normal, almost equal discharge currents flow from both storage batteries and the balance is maintained, but when a cell of one storage battery suffers a short-circuit failure. This had the disadvantage of causing a large imbalance in the discharge current. This is, for example, 1 of the storage battery 6.
If a short-circuit failure occurs in a cell, the terminal voltage of the storage battery 6 will be lower than the terminal voltage of the storage battery 7 by one cell equivalent, so the bus voltage of the power supply bus line 2 will be lower than normal, and the bus voltage will decrease. The potential difference between the storage battery 7 and the storage battery 7 becomes larger than normal, and the discharge current from the storage battery 7 increases excessively.On the other hand, the discharge current from the storage battery 6, which is short-circuited by one cell, decreases, resulting in an unbalanced discharge current. occurs. This unbalance of discharge current causes a large difference in discharge current even if there is a voltage difference between one cell (approximately 1.0 to 1.4 V for a NiCd cell). Figure 4 shows discharge current characteristic data when two 20-cell series NiCd storage batteries are configured in the conventional manner as shown in Figure 2, and one cell of one of the batteries suffers a short-circuit failure. This is an example. The ratio of discharge current during normal operation is approximately 1
On the other hand, in the example shown in Figure 4, the ratio of the discharge currents of a normal storage battery and a storage battery with a one-cell short-circuit failure has increased to about 9:2 on average.
Additionally, the results show that the depth of discharge is 55% in normal conditions, 85% in a normal storage battery, and 23% in a storage battery with one cell short-circuited, indicating a large imbalance between the two storage batteries.

In this way, in conventional configurations, if a cell failure occurs in one storage battery, if parallel use continues, a large discharge current will flow from the normal storage battery, resulting in more discharge than permissible, and a rise in temperature. As a result, there was a risk that a normal storage battery would suffer performance deterioration and shorten its lifespan. For this reason, in the event of a short-circuit failure in a cell, there was a drawback that part of the mission equipment had to be turned off and part of the operation had to be halted in order to use the storage battery within the permissible depth of discharge. . In addition, for artificial satellites that cannot partially suspend mission operations in the shade, extra storage batteries are installed from the beginning, so that even if a cell short-circuit failure occurs, the remaining normal storage batteries can be used in parallel within the allowable depth of discharge. Although it has been made operational, the drawback is that the weight increases due to the increased number of storage batteries.

This invention was made with the purpose of improving such drawbacks, and the purpose is to obtain a power supply device for an artificial satellite that does not cause a large imbalance in discharge current between storage batteries even if a cell short-circuit failure occurs. shall be.

[Means for solving problems]

The power supply device for an artificial satellite according to this invention is provided with relay switches connected in parallel to the required number of cells of each storage battery.

[Effect]

In this invention, even if a short-circuit failure occurs in one storage battery cell, the relay switch installed in the other storage battery is closed.
To cancel a voltage difference between storage batteries caused by a cell short-circuit failure to prevent a large imbalance in discharge current from occurring.

〔Example〕

FIG. 1 is an explanatory diagram of a configuration showing an embodiment of this invention. 1 to 12 are exactly the same as the above-mentioned conventional device. 13 is an end cell 8-N of the storage battery 6
The relay switch 14 connected in parallel to the battery 7 is also a relay switch connected in parallel to the negative end cell 9-N of the storage battery 7. Relay switches 13 and 14 are "opened" and "closed" by commands.

In the satellite power supply system configured as described above, the relay switches 13 and 14 are in the "open" state during normal operation, which is the same as in the conventional system. The operation when a cell short-circuit failure occurs in one of the storage batteries, which is a drawback of the conventional device, will be explained. For example, cells 8-1 to 8-N of storage battery 6
If one of the batteries causes a short-circuit failure, then the storage battery 7
The relay switch 14 is closed by a command at the end of discharge. As a result, the voltage of the storage battery 6 decreases by one cell due to the cell short-circuit failure, but the voltage of the storage battery 7 also decreases by one cell because the relay switch 14 is closed and the cell 9-N is short-circuited. The voltage will drop and both battery voltages will be approximately equal. Therefore, even if a cell short-circuit failure occurs, a large unbalance of discharge current can be prevented. Conversely, if one cell of the storage battery 7 suffers from a short-circuit failure, the relay switch 13 of the storage battery 6 is closed to obtain the same effect.

In addition, although the above description described the parallel use of two storage batteries, it goes without saying that it can also be applied to the parallel use of three or more storage batteries. In addition, in the above explanation, the embodiment was shown assuming a short-circuit failure of one cell, but it can be similarly applied to a short-circuit failure of more cells by connecting relays and switches to the necessary number of cells in parallel. can.

[Effect of idea]

As described above, according to this invention, by using a simple configuration in which a relay/switch is connected in parallel to the cells of storage batteries that are used in parallel, the unbalance of discharge current can be prevented in the event of a cell short-circuit failure when storage batteries are used in parallel. It has the effect of effectively suppressing it.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the configuration of a power supply device for an artificial satellite according to an embodiment of this invention, FIG. 2 is an explanatory diagram of a typical configuration of a power supply device for a conventional satellite, and FIG.
FIG. 4 is a diagram showing an example of the relationship between the depth of discharge and the life of a NiCd storage battery. FIG. 4 is a diagram showing an example of discharge characteristic data when a normal NiCd storage battery and a NiCd storage battery with one cell shorted are used in parallel. In the figure, 1 is a solar cell, 2 is a power bus line, and 3
is a satellite load, 4 is a return line, 5 is a shunt regulator, 6 is a storage battery, 7 is a storage battery, 8 is a cell, 9 is a cell, 10 is a diode, 11 is a diode, 12 is a charging control circuit, 13 is a relay - Switch 14 is a relay switch. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Scope of utility model registration request] In a satellite power supply device that uses multiple storage batteries in parallel to supply power to a common power bus line, each of the storage batteries is connected in parallel to the cells (unit cells) that make up the storage battery. An artificial satellite power supply device comprising: