JP7325361B2 - Independent power supply system and its control method - Google Patents

Description

The present invention relates to an independent power supply system and its control method, and is suitable for application to, for example, a wireless sensor system.

Energy harvesting technology, which converts minute amounts of environmental energy into electrical energy using power generation elements such as solar cells and thermoelectric power generation elements, can be used in environments where power supply is difficult or where wiring work is required for power supply. It is used as an effective self-sustaining power supply technology when installing electronic equipment that operates on low power.

In a self-sustaining power generation system using such energy harvesting technology, the power output from the power generation element is very small, and the amount of power generated by the power generation element fluctuates greatly depending on the environmental conditions. It is common to store electric power to some extent in an electric storage element such as a capacitor before using it.

In this case, it is necessary to increase the capacity of the storage element in order to stably operate the electronic device. There is a problem that it takes a considerable amount of time before power supply can be started.

As one method for solving this problem, Patent Document 1 discloses a power generation control circuit that controls the power generation efficiency of the power generation elements, a storage element group that charges the power generated by the power generation elements, and a charging device for the power generation element group. A charge control circuit for controlling the discharge operation is provided, and the power generation element group is composed of at least a primary storage element that supplies power to the power generation control circuit and the charge control circuit, and a secondary storage element that supplies power to the load device. Then, the capacity of the primary storage element is made smaller than the capacitance value of the secondary storage element, and the power generated by the power generation element is preferentially charged to the primary storage element. A self-charging, self-contained power system is disclosed.

According to this self-sustaining power supply system, even if the power generation element generates power from minute and unstable environmental energy, it is possible to minimize the period until the power generation control circuit starts or stops. Therefore, it is possible to obtain the effect that the power supply to the load device can be started in a short time.

JP 2015-15848 A

により表される。 By the way, in the self-sustaining power generation system disclosed in Patent Document 1, the amount of energy loss when transferring electric charge from the primary storage element to the secondary storage element is V1 for the terminal voltage of the primary storage element, and V1 for the terminal voltage of the secondary storage element. With the terminal voltage of V2 and the capacitance of the secondary storage element as C2, the following equation

is represented by

As is clear from this formula (1), in the self-sustaining power generation system disclosed in Patent Document 1, the larger the capacity of the secondary storage element C2, the more the voltage between the primary storage element and the secondary storage element increases. There is a problem that the larger the difference (V1−V2), the greater the amount of energy loss when transferring charges from the primary storage element to the secondary storage element to charge the secondary storage element.

The present invention has been made in consideration of the above points, and aims to propose a self-sustaining power supply system capable of reducing the amount of energy loss and generating electricity with high efficiency, and a method of controlling the same.

In order to solve such problems, the present invention provides an independent power supply system that supplies power generated by a power generation element to a load, comprising a primary power storage element that stores the power generated by the power generation element, and a primary power storage element that stores the power generated by the power generation element, and supplies power to the load. and a power control unit for controlling charging from the primary storage element to the secondary storage element so that charging from the primary storage element to the secondary storage element is performed in stages. wherein the power control unit monitors the terminal voltage of the primary storage element, and when the terminal voltage exceeds a preset threshold voltage, the power stored in the primary storage element is The secondary storage element is charged by supplying power to the secondary storage element, and the terminal voltage of the secondary storage element is monitored, and when the terminal voltage exceeds the threshold voltage, the set voltage is detected. The threshold voltage is changed to the threshold voltage of the next stage having a higher voltage value than the current threshold voltage .

Further, according to the present invention, there is provided a control method for an autonomous power supply system that supplies electric power generated by a power generation element to a load, wherein the autonomous power supply system includes a primary storage element that stores the electric power generated by the power generation element; and a power supply control section for controlling charging from the primary storage element to the secondary storage element, wherein the power supply control section controls the terminal voltage of the primary storage element and a first step of monitoring the terminal voltage of the secondary storage element; and a second step of controlling charging from the storage element to the secondary storage element , wherein in the second step, the power control unit presets the terminal voltage of the primary storage element. When the threshold voltage is exceeded, the power stored in the primary storage element is supplied to the secondary storage element to charge the secondary storage element, and the terminal voltage of the secondary storage element increases to the The threshold voltage that is set when the threshold voltage is exceeded is changed to the threshold voltage of the next stage having a higher voltage value than the current threshold voltage.

According to the self-sustaining power supply system and the control method thereof of the present invention, the potential difference between the terminal voltage of the primary storage element and the terminal voltage of the secondary storage element can be suppressed within a certain range (within the difference between the voltage values at each stage).

ADVANTAGE OF THE INVENTION According to this invention, the amount of energy loss is reduced, and the self-sustaining power supply system which can be generated with high efficiency, and its control method can be implement|achieved.

Problems, configurations, and effects other than those described above will be clarified by the following description of the mode for carrying out the invention.

1 is a block diagram showing the configuration of a wireless sensor terminal according to this embodiment; FIG. FIG. 4 is a waveform diagram for explaining ON/OFF control of a switch by a voltage monitoring unit; 4 is a chart showing the configuration of a threshold voltage management table; FIG. 4 is a waveform diagram showing how the terminal voltage of the primary storage element changes in the present embodiment. FIG. 4 is a waveform diagram showing how the terminal voltage of the secondary storage element changes in the present embodiment. 4 is a flowchart showing a processing procedure of threshold voltage setting processing; It is a graph which shows an experimental result. It is a graph which shows an experimental result.

One embodiment of the present invention will be described in detail below with reference to the drawings.

It should be noted that the embodiments described below are examples for describing the present invention, and are appropriately omitted and simplified for clarity of description. The present invention can also be implemented in various other forms. Unless otherwise specified, each component may be singular or plural.

The position, size, shape, range, etc. of each component shown in the drawings may not represent the actual position, size, shape, range, etc., in order to facilitate understanding of the invention. As such, the present invention is not necessarily limited to the locations, sizes, shapes, extents, etc., disclosed in the drawings.

Examples of various types of information are described using expressions such as “table”, “list”, and “queue”, but various types of information may be expressed in data structures other than these. For example, various information such as "XX table", "XX list", and "XX queue" may be referred to as "XX information". When describing identification information, expressions such as “identification information”, “identifier”, “name”, “ID”, and “number” are used, but these can be replaced with each other.

When there are a plurality of components having the same or similar functions, they may be described with the same reference numerals and different suffixes. Further, when there is no need to distinguish between these constituent elements, the subscripts may be omitted in the description.

In the embodiments, processing performed by executing a program may be described. Here, a computer executes a program by means of a processor (for example, CPU (Central Processing Unit), GPU (Graphics)), uses storage resources (for example, memory), interface devices (for example, communication port), etc. process.

Therefore, the main body of the processing performed by executing the program may be the processor. Similarly, a main body of processing executed by executing a program may be a controller having a processor, a device, a system, a computer, or a node. The subject of the processing performed by executing the program may be an arithmetic unit, and may include a dedicated circuit for performing specific processing. Here, the dedicated circuit is, for example, FPGA (Field Programmable Gate Array), ASIC (Application Specific Integrated Circuit), CPLD (Complex Programmable Logic Device), or the like.

The program may be installed on the computer from a program source. The program source may be, for example, a program distribution server or a computer-readable storage medium. When the program source is a program distribution server, the program distribution server may include a processor and storage resources for storing the distribution target program, and the processor of the program distribution server may distribute the distribution target program to other computers. Also, in the embodiment, two or more programs may be implemented as one program, and one program may be implemented as two or more programs.

(1) Configuration of wireless sensor terminal according to this embodiment FIG. 1 shows the configuration of a wireless sensor terminal 1 according to this embodiment. The wireless sensor terminal 1 has an independent power supply system 2 and supplies the generated power and the power supplied from the primary battery 3 via the diode 4 to the sensor 6 and the communication device 7 constituting the load 5 .

In the case of this embodiment, the sensor 6 is assumed to be an ammeter that measures the motor current of the conveying device or cutting machine, but other sensors that measure various physical quantities other than the current may be used. The communication device 7 is composed of a wireless communication device. The communication device 7 wirelessly transmits the physical quantity measured by the sensor 6 to a receiving device (not shown) via the antenna 8 on a regular or irregular basis.

The independent power supply system 2 includes a power generation element 10 , a rectifier circuit 11 , a primary storage element C<b>1 , a secondary storage element C<b>2 , and a power control section 12 .

The power generating element 10 is composed of, for example, a current transformer. In the case of this embodiment, the power generating element 10 is installed so that the primary coil surrounds the cable 13 through which the target motor current flows. The power generation element 10 transmits generated power based on an electromagnetic induction current generated in the primary side coil in response to magnetic flux fluctuations around the cable 13 caused by the motor current flowing through the cable 13 to the rectifier circuit 11 from the secondary side coil. Output.

The rectifier circuit 11 is composed of four bridge-connected diodes D1 to D4. The rectifier circuit 11 rectifies the generated power output from the power generation element 10 and applies the rectified generated power to the primary storage element C1. The primary storage element C1 is composed of a capacitor having a capacity of several tens [μF] and stores the power generated by the rectifier circuit 11 .

The electric power stored in the primary storage element C1 is supplied to the secondary storage element C2 via a switch 20 of the power control unit 12, which will be described later. The secondary storage element C2 is composed of a capacitor having a capacity of several tens [mF], which is larger than that of the primary storage element C1, and stores the electric power supplied from the primary storage element C1.

As the capacitors forming the primary storage element C1 and the secondary storage element C2, it is preferable to use a laminated ceramic capacitor having a small leakage current and a small internal resistance. However, an electrolytic capacitor other than the laminated ceramic capacitor, a tantalum electrolytic capacitor, an electric double layer capacitor, or the like can also be used. Further, each of the primary storage element C1 and the secondary storage element C2 may be configured by one capacitor, or may be configured by connecting a plurality of capacitors in parallel.

The power control unit 12 is a functional unit that controls charging from the primary storage element C1 to the secondary storage element C2, and includes a switch 20, a voltage monitoring unit 21, and a control unit (hereinafter referred to as MCU (Micro Controller Unit)). 22.

The switch 20 is composed of a general switching element such as a field effect transistor that has a small resistance when turned on and a large resistance when turned off. The switch 20 is on/off controlled by the voltage monitoring unit 21 .

The voltage monitoring unit 21 monitors the terminal voltage V1 of the primary storage element C1, and on/off-controls the switch 20 according to the voltage value of the terminal voltage V1. Specifically, as shown in FIG. 2, the voltage monitoring unit 21 turns off the switch 20 when the terminal voltage V1 of the primary storage element C1 is lower than the first threshold voltage Va specified by the MCU 22 in advance. By doing so, the power generated by the rectifier circuit 11 is used to charge the primary storage element C1.

After that, when the terminal voltage V1 of the primary storage element C1 reaches the first threshold voltage Va, the voltage monitoring unit 21 turns on the switch 20 so that the charge accumulated in the primary storage element C1 is turned on. Secondary storage element C2 is charged by supplying it to secondary storage element C2 via Via.

Further, after that, when the terminal voltage V1 of the primary storage element C1 drops to a second threshold voltage Vb that is lower than the first threshold voltage Va by a predetermined voltage, the voltage monitoring unit 21 returns the switch 20 to the OFF state again. Thereafter, the same control operation as described above for turning on/off switch 20 in accordance with the magnitude of terminal voltage V1 of primary storage element C1 is repeated. As a result, the charging and discharging of the primary storage element C1 are repeated as the switch 20 is turned on and off, and the secondary storage element C2 is accordingly charged until it reaches the first threshold voltage Va.

At this time, the voltage monitoring unit 21 detects the terminal voltage V2 of the secondary storage element C2 and constantly notifies the MCU 22 of the detected terminal voltage V2 of the secondary storage element C2.

The MCU 22 is composed of a microprocessor with a CPU and memory. The MCU 22 initially starts operating with the power stored in the primary storage element C1, and after a certain amount of power has been stored in the secondary storage element C2, operates with the power stored in the secondary storage element C2. do.

The MCU 22 holds a threshold voltage management table 23 as shown in FIG. 3 in its memory. The threshold voltage management table 23 stores voltage values Vt (Vt1, Vt2, Vt3 , . . . ) are respectively registered, and as shown in FIG.

The step column 23A stores a numerical value representing each step, and the voltage value column 23B stores the voltage value Vt to be set as the first threshold voltage Va in the voltage monitoring unit 21 at the corresponding step. . In this case, the magnitude of the voltage value Vt at each stage is determined so that the voltage value Vt at the first stage (Vt1 in FIG. 3) is the smallest and gradually increases with each step.

At least three levels of voltage values Vt are registered in advance in the threshold voltage management table 23 . In this case, as the voltage value Vt (Vt1) of the first stage, a minimum voltage value at which the MCU 22 can start operating (hereinafter referred to as an operable voltage value) is registered. Also, as the voltage values Vt (Vt2, Vt3, . . . in FIG. 3) of the second and subsequent stages, voltage values selected so that the voltage difference from the voltage value Vt of the next stage does not exceed a certain level are registered. be done. Furthermore, as the voltage value Vt in the final stage, a voltage value Vt that is large enough to supply power to the load 5 is selected and registered.

Then, the MCU 22 starts operating when the terminal voltage V1 of the primary storage element C1 becomes the voltage at which the MCU 22 can operate. The value of Vt is obtained and set in the voltage monitoring unit 21 as the first threshold voltage Va.

As a result, the primary storage element C1 is charged by the voltage applied from the rectifier circuit 11 to the primary storage element C1, and eventually the terminal voltage V1 of the primary storage element C1 is set by the MCU 22 as the first threshold voltage Va. When the voltage value Vt is reached, voltage monitoring unit 21 starts on/off control of switch 20 as described above, thereby starting charging of secondary storage element C2.

The MCU 22 also monitors the terminal voltage V2 of the secondary storage element C2 notified from the voltage monitoring unit 21, and the terminal voltage V2 is the voltage value set as the first threshold voltage Va in the voltage monitoring unit 21 at that time. When reaching Vt, the voltage value Vt of the next stage is obtained from the threshold voltage management table 23, and the obtained voltage value Vt is set in the voltage monitoring unit 21 as a new first threshold voltage Va.

As a result, the voltage monitoring unit 21 keeps the switch 20 in the OFF state until the terminal voltage V1 of the primary storage element C1 reaches the voltage value Vt newly set as the first threshold voltage Va by the MCU 22 at this time. At the same time, when the terminal voltage V1 of the primary storage element C1 eventually reaches the voltage value Vt, the voltage monitoring unit 21 starts on/off control of the switch 20 as described above, thereby charging the secondary storage element C2. is resumed.

After that, the terminal voltage V1 of the primary storage element C1 is registered in the threshold voltage management table 23 as the voltage value Vt (Vt2) in the second stage, the voltage value Vt (Vt3) in the third stage, and so on. The same processing as described above is repeated between the MCU 22 and the voltage monitoring unit 21 each time.

As a result, the terminal voltage V1 of the first storage element C1 rises stepwise as shown in FIG. It gradually increases toward (the last voltage value Vt registered in the threshold voltage management table 23). Then, when the terminal voltage V2 of the secondary storage element C2 eventually reaches the final voltage value Vt, the voltage monitoring unit 21 controls the switch 20 to maintain the ON state. Voltage V2 is maintained at a voltage value around the final voltage value Vt.

In the process of raising the first threshold voltage Va toward the final voltage value Vt and after the first threshold voltage Va reaches the final voltage value Vt, the When the stored power is consumed by the load 5, the terminal voltage V2 of the secondary storage element C2 becomes the first threshold voltage Va, which is the voltage value one step before the voltage value Vt set in the voltage monitoring unit 21 at that time. There is a possibility that a situation in which the voltage drops below Vt may occur.

In such a case, the MCU 22 changes the voltage value Vt set as the first threshold voltage Va in the voltage monitoring unit 21 to the voltage value Vt of the previous stage. In this manner, the MCU 22 prevents the voltage difference between the terminal voltage V1 of the primary storage element C1 and the terminal voltage V2 of the secondary storage element C2 from exceeding a certain voltage (the difference between the voltage values Vt at each stage). By controlling the value of the threshold voltage Va of 1, it is possible to prevent an increase in energy loss when electric charges are transferred from the primary storage element C1 to the secondary storage element C2.

(2) Threshold Voltage Setting Processing FIG. 6 shows a specific processing procedure of the threshold voltage setting processing executed by the MCU 22 regarding the setting of the first threshold voltage Va as described above. The MCU 22 appropriately updates the voltage value Vt set as the first threshold voltage Va for the voltage monitoring unit 21 according to the processing procedure shown in FIG.

In practice, when the terminal voltage V1 of the first storage element C1 reaches the operating voltage and starts operating, the MCU 22 starts this threshold voltage setting process, and first registers it in the threshold voltage management table 23 (FIG. 3). The value of the voltage value Vt of the first stage is obtained, and is set in the voltage monitoring unit 21 as the first threshold voltage Va (S1).

Subsequently, the MCU 22 detects that the terminal voltage V2 of the secondary storage element C2 notified from the voltage monitoring unit 21 is equal to or higher than the operable voltage of the MCU 22 (the voltage value Vt of the first stage set in the voltage monitoring unit 21 in step S1). (S2).

Then, when the terminal voltage V2 of the secondary storage element C2 eventually becomes equal to or higher than the operable voltage of the MCU 22, the MCU 22 reads the voltage value Vt of the next stage (here, the voltage value Vt2 of the second stage) from the threshold voltage management table 23. , is set in the voltage monitoring unit 21 as a new first threshold voltage Va (S3).

Next, based on the terminal voltage V2 of the secondary storage element C2 notified from the voltage monitoring unit 21, the MCU 22 determines whether the terminal voltage V2 has reached the voltage value Vt currently set in the voltage monitoring unit 21. (S4). When the MCU 22 obtains a negative result in this determination, the MCU 22 determines whether or not the terminal voltage V2 of the secondary storage element C2 has decreased to less than the voltage value Vt immediately before the voltage value Vt currently set in the voltage monitoring unit 21. (S6).

When the MCU 22 obtains a negative result in the judgment of step S6, it returns to step S4, and thereafter repeats the loop of steps S4-step S6-step S4 until it obtains a positive result in step S4 or step S6.

Then, MCU 22 eventually obtains a positive result in step S4 because the terminal voltage of secondary storage element C2 reaches the voltage value Vt currently set in voltage monitoring unit 21. When MCU 22 obtains a positive result in step S4, voltage monitoring unit 21 sends the first A voltage value Vt one step higher than the voltage value Vt currently set as the threshold voltage Va of is read out from the threshold voltage management table 23, and is set in the voltage monitoring unit 21 as a new first threshold voltage Va ( S5). The MCU 22 then returns to step S4, and then repeats the processes after step S4 in the same manner as described above.

However, even if the MCU 22 obtains a positive result in step S4, the voltage value Vt currently set in the voltage monitoring unit 21 is changed from the final-stage voltage value Vt registered in the threshold voltage management table 23 ( If it is the highest voltage value Vt registered in the threshold voltage management table 23, the process of step S5 is omitted and the process returns to step S4, after which the processes after step S4 are repeated in the same manner as described above.

In addition, the MCU 22 makes an affirmative determination in step S6 when the terminal voltage V2 of the secondary storage element C2 becomes a value less than the voltage value Vt that is one step lower than the voltage value Vt currently set in the voltage monitoring unit 21. When the result is obtained, the voltage value Vt that is one step lower than the voltage value Vt currently set as the first threshold voltage Va in the voltage monitoring unit 21 is read from the threshold voltage management table 23, and is used as the new first threshold voltage Va. It is set in the voltage monitoring unit 21 as the threshold voltage Va (S7). The MCU 22 then returns to step S4, and then repeats the processes after step S4 in the same manner as described above.

However, even if a positive result is obtained in step S6, the MCU 22 determines that the voltage value Vt currently set in the voltage monitoring unit 21 is the first-step voltage value Vt registered in the threshold voltage management table 23. If it is (the smallest voltage value Vt registered in the threshold voltage management table 23), the process of step S7 is omitted, the process returns to step S4, and then the processes after step S4 are repeated.

(3) Effect of this embodiment As described above, in the wireless sensor terminal 1 according to this embodiment, the voltage monitoring unit 21 and the MCU 22 operate the switch 20 so as to increase the terminal voltage V2 of the secondary storage element C2 step by step. Since the on/off control is executed, the potential difference between the terminal voltage V1 of the primary storage element C1 and the terminal voltage V2 of the secondary storage element C2 can be suppressed within a certain range (within the difference between the voltage values Vt at each stage). Therefore, according to the wireless sensor terminal 1, it is possible to reduce the amount of energy loss during charge transfer from the primary storage element C1 to the secondary storage element C2 and to generate power with high efficiency.

In fact, according to the experiment, the result shown in FIG. 7 was obtained as a change in the terminal voltage of the secondary storage element C2 by the ON/OFF control of the switch 20 according to the present embodiment. As is clear from FIG. 7, the conventional method of charging the terminal voltage V2 of the secondary storage element C2 so as to increase stepwise (curve K1) as in the present embodiment does not cause a stepwise increase. It was confirmed that the secondary storage element C2 can be charged more efficiently than in the case of charging the secondary storage element C2 (curve K2).

Further, as shown in FIG. 8, the charging method (curve K3) of the secondary storage element C2 according to the present embodiment and the conventional charging method (curve K4) of the secondary storage element C2 are compared with each other. Taking the square of the terminal voltage V2 and comparing it in terms of energy, it was also confirmed that the former can charge the secondary storage element C2 with high efficiency (the self-sustained power supply system 2 can generate power with high efficiency).

(4) Other Embodiments In the above-described embodiment, the case where the self-sustaining power supply system 2 according to the present invention is applied to the wireless sensor terminal 1 was described, but the present invention is not limited to this. The invention can be widely applied to various devices other than the wireless sensor terminal 1 .

In the above-described embodiment, the voltage monitoring unit 21 and the MCU 22 are provided separately, but the present invention is not limited to this, and the voltage monitoring unit 21 and the MCU 22 are configured as one functional unit. You may make it

Furthermore, in the above-described embodiment, a case where a current transformer is applied as the power generation element 10 was described, but the present invention is not limited to this, and environmental energy such as light, vibration, heat, and radio waves is collected. Various power generating elements such as solar cells, thermoelectric elements, and piezoelectric elements can be widely applied as long as they are elements that convert into electric energy.

Furthermore, in the above-described embodiment, the case where the primary battery 3 is used in addition to the independent power supply system 2 has been described, but the present invention is not limited to this, and the present invention can be applied even when the primary battery 3 is not used. can do.

The present invention stores electric power generated by a power generation element in a primary storage element, charges the secondary storage element by transferring the charge stored in the primary storage element to the secondary storage element, and charges the secondary storage element. It can be widely applied to various configurations of independent power supply systems that supply the power stored in the load to the load.

Reference Signs List 1 wireless sensor terminal, 2 self-sustaining power supply system, 5 load, 10 power generation element, 11 rectifier circuit, 12 power control unit, 20 switch, 21 voltage monitoring unit, 22 -- MCU, 23 -- threshold voltage management table, C1 -- primary storage element, C2 -- secondary storage element, V1, V2 -- terminal voltage, Vt -- voltage value.

Claims (6)

In an independent power supply system that supplies the power generated by the power generation element to the load,
a primary storage element that stores the electric power generated by the power generation element;
a secondary storage element that supplies power to the load;
a power control unit that controls charging from the primary storage element to the secondary storage element so as to increase the terminal voltage of the secondary storage element in stages ,
The power control unit
By monitoring the terminal voltage of the primary storage element and supplying the power stored in the primary storage element to the secondary storage element when the terminal voltage exceeds a preset threshold voltage While charging the secondary storage element, the terminal voltage of the secondary storage element is monitored, and when the terminal voltage exceeds the threshold voltage, the set threshold voltage is increased from the current threshold voltage. change to the threshold voltage of the next stage with a larger voltage value
The self-contained power system according to claim 1, characterized by: The power control unit
2. The self-sustaining device according to claim 1 , wherein when the terminal voltage of the secondary storage element becomes less than the threshold voltage one step before, the terminal voltage is changed to the threshold voltage one step before. power system. The power control unit
a switch connecting between the primary storage element and the secondary storage element;
a voltage monitoring unit that monitors the terminal voltage of the primary storage element, controls on/off of the switch based on the terminal voltage, and detects the terminal voltage of the secondary storage element;
a control unit that sets a threshold voltage in the voltage monitoring unit based on the terminal voltage of the secondary storage element detected by the monitoring unit,
The voltage monitoring unit
turning on/off the switch so that the secondary storage element is charged from the primary storage element when the terminal voltage of the primary storage element reaches the threshold voltage set by the control unit;
The control unit
When the terminal voltage of the secondary storage element detected by the voltage monitoring unit reaches the threshold voltage set in the voltage monitoring unit, the threshold voltage set in the voltage monitoring unit is changed to the current threshold voltage. The self-sustaining power supply system according to claim 1, wherein the threshold voltage is updated to the next stage whose voltage value is higher than the voltage. In a control method for an independent power supply system that supplies power generated by a power generation element to a load,
The independent power supply system includes:
a primary storage element that stores the electric power generated by the power generation element;
a secondary storage element that supplies power to the load;
a power control unit that controls charging from the primary storage element to the secondary storage element,
a first step in which the power supply control unit monitors the terminal voltage of the primary storage element and the terminal voltage of the secondary storage element;
a second step in which the power supply control unit controls charging from the primary storage element to the secondary storage element so as to increase the terminal voltage of the secondary storage element in stages ;
In the second step, the power control unit
When the terminal voltage of the primary storage element exceeds a preset threshold voltage, power stored in the primary storage element is supplied to the secondary storage element to restore the secondary storage element. While charging, the threshold voltage set when the terminal voltage of the secondary storage element exceeds the threshold voltage is changed to the threshold voltage of the next stage having a higher voltage value than the current threshold voltage. change
A control method for an independent power supply system, characterized by: In the second step, the power control unit
5. The self-sustaining device according to claim 4 , wherein when the terminal voltage of the secondary storage element becomes less than the threshold voltage one step before, the terminal voltage is changed to the threshold voltage one step before. How to control the power system. The power control unit
a switch connecting between the primary storage element and the secondary storage element;
a voltage monitoring unit that monitors the terminal voltage of the primary storage element, controls on/off of the switch based on the terminal voltage, and detects the terminal voltage of the secondary storage element;
a control unit that sets a threshold voltage in the voltage monitoring unit based on the terminal voltage of the secondary storage element detected by the monitoring unit;
In the first and second steps,
The voltage monitoring unit
turning on/off the switch so that the secondary storage element is charged from the primary storage element when the terminal voltage of the primary storage element reaches the threshold voltage set by the control unit;
The control unit
When the terminal voltage of the secondary storage element detected by the voltage monitoring unit reaches the threshold voltage set in the voltage monitoring unit, the threshold voltage set in the voltage monitoring unit is changed to the current threshold voltage. 5. The control method of the self-sustaining power supply system according to claim 4 , wherein the threshold voltage is updated to the next stage having a higher voltage value than the voltage.

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