JP2024151778A - Output voltage adjustment device, power storage system, output voltage adjustment method, and program - Google Patents

Abstract

To provide an output voltage control device, a power storage system, an output voltage control method and a program in which, even if an unstable charging current is supplied, a fully charged state can be appropriately detected.SOLUTION: An output voltage control device for controlling an output voltage of a power conversion device disposed in a power storage system, includes an acquisition unit that acquires a battery voltage of a secondary battery, and a control circuit that controls the output voltage on the basis of the battery voltage so as to control a difference between the battery voltage and the output voltage of the power conversion device to be equal to or less than a prescribed voltage difference.SELECTED DRAWING: Figure 1

Description

This disclosure relates to an output voltage adjustment device, a power storage system, an output voltage adjustment method, and a program.

Conventionally, rechargeable secondary batteries such as nickel-hydrogen secondary batteries have been widely used as power sources for operating various devices. The voltage and current supplied to the secondary battery are usually controlled so that it is charged efficiently. For example, when the secondary battery is a nickel-hydrogen secondary battery, it is charged using a constant current charging method in which the charging current to the secondary battery is constant (see, for example, Patent Document 1).

A conventional power storage system that charges using a constant current charging method includes, for example, a DC-DC converter, a constant current circuit as a charging control circuit, and a secondary battery. In such a power storage system, when power for charging is supplied from the outside, the DC-DC converter converts the power to a predetermined voltage, generates an output voltage, and supplies it to the constant current circuit. The constant current circuit outputs a predetermined charging current based on the output voltage supplied from the DC-DC converter. The secondary battery is charged by the charging current output from the constant current circuit.

Japanese Patent Application Publication No. 7-236233

During charging, a voltage that is the difference between the output voltage of the DC-DC converter and the battery voltage of the secondary battery is applied to the constant current circuit, and the constant current circuit generates heat due to this applied voltage and the charging current. Since the battery voltage of a secondary battery charged using a constant current charging method changes depending on the charging state, the voltage difference between the output voltage of the DC-DC converter, which is a fixed value, and the battery voltage of the secondary battery also changes depending on the charging state. In other words, the voltage applied to the constant current circuit changes depending on the charging state of the secondary battery.

Therefore, when a large voltage is applied to the constant current circuit, the amount of heat generated in the constant current circuit also increases accordingly, which is a problem. Conventionally, in order to reduce heat generation in the constant current circuit, a heat dissipation means such as a heat sink is provided in the constant current circuit, but providing such a heat dissipation means results in an increase in the size of the power storage system.

The present disclosure has been made in consideration of the problems in the above-mentioned conventional technology, and aims to provide an output voltage adjustment device, a power storage system, an output voltage adjustment method, and a program that can reduce heat generation in a current control circuit.

The output voltage adjustment device for a secondary battery according to the present disclosure comprises:
An output voltage adjustment device that adjusts an output voltage of a voltage conversion device provided in a power storage system,
An acquisition unit for acquiring a battery voltage of the secondary battery;
The power supply includes a control circuit that controls the output voltage based on the battery voltage so that a difference between an output voltage of the voltage conversion device and the battery voltage is equal to or smaller than a predetermined voltage difference.

In addition, the power storage system according to the present disclosure includes:
A secondary battery that stores power;
a voltage conversion device that converts an externally supplied voltage into an output voltage;
a current control circuit for controlling a charging current for the secondary battery;
an acquisition unit that acquires a battery voltage of the secondary battery;
The power supply includes a control circuit that controls the output voltage based on the battery voltage so that a difference between the output voltage and the battery voltage is equal to or smaller than a predetermined voltage difference.

Further, the output voltage adjusting method according to the present disclosure includes:
An output voltage adjustment method for adjusting an output voltage of a voltage conversion device provided in a power storage system, comprising:
Obtain the battery voltage of the secondary battery,
The output voltage is controlled based on the battery voltage so that the difference between the output voltage and the battery voltage is equal to or smaller than a predetermined voltage difference.

Furthermore, the program according to the present disclosure is
The above output voltage regulation method is executed by a computer.

This disclosure makes it possible to reduce heat generation in the current control circuit.

1 is a block diagram showing an example of a configuration of a power storage system according to a first embodiment of the present invention; 2 is a circuit diagram showing an example of the configuration of the DC-DC converter of FIG. 1. 2 is a circuit diagram showing an example of the configuration of the constant current circuit of FIG. 1; 2 is a functional block diagram showing an example of the configuration of a control circuit in FIG. 1 . 5 is a flowchart showing an example of the flow of an output voltage adjustment process performed by the power storage system according to the first embodiment. FIG. 11 is a block diagram showing an example of a configuration of a power storage system according to a modified example of the first embodiment. FIG. 2 is a circuit diagram for explaining an example of a configuration for outputting a constant voltage and a constant current.

The following describes embodiments of the present disclosure with reference to the drawings. The present disclosure is not limited to the following embodiments, and various modifications are possible without departing from the spirit of the present disclosure. In addition, in each drawing, the same reference numerals are used to denote the same or equivalent parts, and this is common throughout the entire specification.

<First embodiment>
Hereinafter, a first embodiment of the present disclosure will be described. The power storage system according to the first embodiment is a system that charges a secondary battery with a constant charging current by using, for example, a constant current charging method.

[Configuration of power storage system 100]
Fig. 1 is a block diagram showing an example of the configuration of a power storage system 100 according to the first embodiment. Fig. 2 is a circuit diagram showing an example of the configuration of a DC-DC converter 20 of Fig. 1. Fig. 3 is a circuit diagram showing an example of the configuration of a constant current circuit 30 of Fig. 1. Fig. 4 is a functional block diagram showing an example of the configuration of a control circuit 10 of Fig. 1.

As shown in FIG. 1, the power storage system 100 includes a control circuit 10, a DC-DC converter 20, a constant current circuit 30, a secondary battery 40, and a detection unit 50. In the first embodiment, the control circuit 10 and the detection unit 50 constitute the output voltage adjustment device of the present disclosure.

The DC-DC converter 20 corresponds to the voltage conversion device of the present disclosure, and converts the voltage supplied from the outside into a predetermined voltage and outputs it. In the present embodiment 1, the DC-DC converter 20 converts the voltage supplied from the outside into an output voltage V1, which is a voltage indicated by a control signal supplied from the control circuit 10, and outputs it.

As shown in FIG. 2, the DC-DC converter 20 includes a constant voltage output circuit 21 and a voltage variable circuit 22.

The constant voltage output circuit 21 is, for example, a boost circuit, and boosts the voltage supplied from the outside to a given voltage. The constant voltage output circuit 21 has an inductor 211, a switching element 212, a diode 213, a capacitor 214, and a switching control unit 215.

The inductor 211 is connected to the input terminal of the constant voltage output circuit 21 (DC-DC converter 20). The diode 213 is a backflow prevention element for preventing reverse current flow, and is connected in series with the inductor 211.

The switching element 212 is configured using a semiconductor element such as a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor), and is connected between the inductor 211 and the diode 213. The switching element 212 performs a switching operation to be turned ON or OFF based on a switching signal supplied from the switching control unit 215.

Capacitor 214 is a smoothing capacitor that smoothes the voltage output from the constant voltage output circuit 21 and is connected to the output terminal of diode 213.

The switching control unit 215 controls the switching element 212 and has a PWM (Pulse Width Modulation) terminal and a feedback (FB) terminal. The switching control unit 215 receives a feedback signal (FB signal) supplied from the voltage variable circuit 22 at the FB terminal. Based on the input FB signal, the switching control unit 215 generates a switching signal, which is a PWM voltage, for controlling the switching element 212 so that the output voltage V1 from the constant voltage output circuit 21 is constant. The switching control unit 215 then outputs the generated switching signal from the PWM terminal and supplies it to the switching element 212.

In this example, the constant voltage output circuit 21 is described as a boost circuit, but this is not limited to this and may be a step-down type or a step-up/step-down type circuit. The constant voltage output circuit 21 may also be an asynchronous type or a synchronous rectification type.

The voltage variable circuit 22 converts the control signal received from the control circuit 10 into a feedback signal to be supplied to the constant voltage output circuit 21 and outputs it. The voltage variable circuit 22 has multiple elements including an operational amplifier 221.

The voltage variable circuit 22 amplifies the control signal received from the control circuit 10 using an operational amplifier 221 and outputs it as a feedback signal. The feedback signal output from the voltage variable circuit 22 is supplied to the switching control unit 215 of the constant voltage output circuit 21.

Here, as will be described in detail later, the control signal from the control circuit 10 supplied to the voltage variable circuit 22 changes according to the battery voltage of the secondary battery 40. Therefore, the FB signal supplied to the constant voltage output circuit 21 changes according to the battery voltage.

The PWM signal supplied to the switching control unit 215 is generated based on the FB signal. As a result, the PWM signal supplied to the switching control unit 215 changes according to the battery voltage. Therefore, the output voltage V1 output from the DC-DC converter 20 also changes according to the battery voltage.

That is, the switching control unit 215 outputs a switching signal and supplies it to the switching element 212 so that the voltage difference with the battery voltage is equal to or less than a predetermined voltage difference. Therefore, the DC-DC converter 20 outputs an output voltage V1 according to the battery voltage of the secondary battery 40 based on the control signal from the control circuit 10.

The constant current circuit 30 in FIG. 1 corresponds to the current control circuit of the present disclosure, and controls the charging current I to the secondary battery 40. In the present embodiment 1, the constant current circuit 30 outputs a constant charging current I based on the output voltage V1 output from the DC-DC converter 20, and supplies it to the secondary battery 40.

As shown in FIG. 3, the constant current circuit 30 includes a current sense resistor 301, an operational amplifier 302, a MOSFET 303, and a number of resistor elements. One end of the current sense resistor 301 is connected to the output terminal of the DC converter 20, and the other end is connected to the source terminal of the MOSFET 303.

The non-inverting input terminal and the inverting input terminal of the operational amplifier 302 are connected to both ends of the current sense resistor 301. In addition, the output terminal of the operational amplifier 302 is connected to the gate terminal of the MOSFET 303.

MOSFET 303 is provided to control the current to the secondary battery 40. The source terminal of MOSFET 303 is connected to the current sense resistor 301. The gate terminal of MOSFET 303 is connected to the output terminal of the operational amplifier 302, and the drain terminal is connected to the secondary battery 40.

The secondary battery 40 in FIG. 1 is composed of, for example, one or more secondary battery cells. When the secondary battery 40 is composed of multiple secondary battery cells, the secondary battery 40 is composed, for example, of the secondary battery cells connected in series. The secondary battery 40 is, for example, a nickel-hydrogen secondary battery. Note that the type of the secondary battery 40 is not limited to this example, and may be a secondary battery other than a nickel-hydrogen secondary battery, such as a lithium-ion secondary battery.

The secondary battery 40 is charged by a charging current I supplied from a constant current circuit 30, which is a current control circuit, and stores power. In the present embodiment 1, the secondary battery 40 is charged by a constant current charging method using a constant charging current I supplied from the constant current circuit 30.

In this example, one secondary battery 40 is provided, but this is not limited thereto, and two or more secondary batteries 40 may be provided. When multiple secondary batteries 40 are provided, the multiple secondary batteries 40 are connected in parallel, for example.

The detection unit 50 corresponds to the acquisition unit of the present disclosure, and is, for example, a sensor group composed of various sensors. The detection unit 50 periodically detects state quantities related to the secondary battery 40 and supplies the detected state quantities to the control circuit 10. In the present embodiment 1, the detection unit 50 detects the battery voltage V2 and charging current I of the secondary battery 40 as state quantities during a charging process for charging the secondary battery 40.

The control circuit 10 controls the entire energy storage system 100. The control circuit 10 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory), all of which are not shown. The CPU reads out a program corresponding to the processing content from the ROM and loads it into the RAM, and works with the loaded program to centrally control the operation of the energy storage system 100.

In the first embodiment, the control circuit 10 controls the DC-DC converter 20 based on the battery voltage V2 and charging current I of the secondary battery 40 detected by the detection unit 50, and performs an output voltage adjustment process to adjust the output voltage V1 output from the DC-DC converter 20. The output voltage adjustment process will be described in detail later.

As shown in FIG. 4, the control circuit 10 has a state quantity acquisition unit 11, a ΔV calculation unit 12, an output voltage determination unit 13, and a memory unit 14. Note that FIG. 4 shows only the processing unit for the function related to the output voltage adjustment process among the components of the control circuit 10.

The state quantity acquisition unit 11 acquires the battery voltage V2 and charging current I detected by the detection unit 50 as state quantities related to the secondary battery 40. The acquired battery voltage V2 is supplied to the output voltage determination unit 13. The acquired charging current I is supplied to the ΔV calculation unit 12.

The ΔV calculation unit 12 calculates the voltage difference ΔV such that the heat generation amount W in the constant current circuit 30 is equal to or less than the allowable heat generation amount, based on the charging current I acquired by the state quantity acquisition unit 11 and the allowable heat generation amount for the heat generation amount W in the constant current circuit 30 stored in the memory unit 14.

The allowable heat generation amount here indicates the maximum heat generation amount that can be tolerated in the constant current circuit 30, and is the heat generation amount obtained based on the absolute maximum ratings of the various circuit elements that make up the constant current circuit 30. Furthermore, the voltage difference ΔV is the voltage difference between the output voltage V1 of the DC-DC converter 20 and the battery voltage V2 of the secondary battery 40. This voltage difference ΔV essentially indicates the voltage applied to the constant current circuit 30.

The output voltage determination unit 13 determines the output voltage V1 of the DC-DC converter 20 so that the voltage difference ΔV calculated by the ΔV calculation unit 12 is equal to or less than a predetermined voltage difference. The voltage difference at this time is the voltage difference ΔV when the amount of heat generated in the constant current circuit 30 is the allowable amount of heat generation. The output voltage determination unit 13 outputs a control signal to the DC-DC converter 20 to cause the DC-DC converter 20 to output the determined output voltage V1.

The memory unit 14 stores various information used by the control circuit 10. In the present embodiment 1, the memory unit 14 stores in advance the allowable heat generation amount used when the ΔV calculation unit 12 calculates the voltage difference ΔV.

[Output voltage adjustment process]
Next, a description will be given of the output voltage adjustment process by the power storage system 100 according to the present embodiment 1. The output voltage adjustment process is a process for adjusting the output voltage V1 of the DC-DC converter 20 so that the heat generation amount W in the constant current circuit 30 is equal to or less than the allowable heat generation amount.

(Heat generation from constant current circuit 30)
As explained in the Background section, the constant current circuit 30 generally generates heat due to the applied voltage and charging current I. In the constant current circuit 30, an allowable heat generation amount indicating the maximum allowable heat generation amount is specified based on the absolute maximum ratings of the circuit elements constituting the constant current circuit 30. Therefore, when charging the secondary battery 40, it is necessary to ensure that the heat generation amount W in the constant current circuit 30 does not exceed the allowable heat generation amount.

1, the heat generation amount W in the constant current circuit 30 during charging is calculated based on the formula (1). The voltage difference ΔV in the formula (1) is calculated based on the formula (2).
Heat generation amount W=voltage difference ΔV×charging current I (1)
Voltage difference ΔV=output voltage V1−battery voltage V2 (2)

Furthermore, when the secondary battery 40 is charged using a constant current charging method, the charging current I to the secondary battery 40 is a constant value, so the heat generation amount W in the constant current circuit 30 changes depending on the voltage difference ΔV.

Here, the battery voltage V2 of the secondary battery 40 generally varies depending on the state of charge. For example, as the SOC (State Of Charge), which indicates the charging rate of the secondary battery 40, increases, the battery voltage V2 also increases accordingly. Furthermore, the DC-DC converter 20 normally operates to output a constant output voltage V1 regardless of the state of charge of the secondary battery 40.

In this way, when the output voltage V1 is a fixed value, the voltage difference ΔV changes in response to changes in the battery voltage V2, and the heat generation amount W in the constant current circuit 30 also changes. Therefore, when the battery voltage V2 is small, the voltage difference ΔV increases according to the relationship shown in equation (2), and the heat generation amount W in the constant current circuit 30 increases, which may exceed the allowable heat generation amount.

For example, in the constant current circuit 30 shown in FIG. 3, a voltage difference ΔV, which is the difference between the output voltage V1 from the DC converter 20 and the battery voltage V2 of the secondary battery 40, is constantly applied to the current sense resistor 301 and the MOSFET 303. In addition, the charging current I flowing through the current sense resistor 301 and the MOSFET 303 is constant.

Therefore, when the output voltage V1 is a fixed value and the battery voltage V2 is low, the voltage difference ΔV applied to the current sense resistor 301 and the MOSFET 303 is maximum, and because the charging current I is constant, the power is also maximum, and the heat generation amount W is also maximum. Therefore, if the heat generation amount W exceeds the allowable heat generation amount, it is necessary to dissipate the heat using a heat dissipation means such as a heat sink.

On the other hand, when the charging current I is a fixed value, the heat generation amount W in the constant current circuit 30 can be reduced by reducing the voltage difference ΔV according to the relationship in equation (1). Since the voltage difference ΔV is the difference between the output voltage V1 and the battery voltage V2 as shown in equation (2), in order to reduce the heat generation amount W, it is sufficient to change the output voltage V1 according to the battery voltage V2 so that the voltage difference ΔV is reduced.

At this time, if the output voltage V1 is changed according to the battery voltage V2 so that the voltage difference ΔV is equal to or less than a predetermined voltage difference, the heat generation amount W in the constant current circuit 30 can be kept equal to or less than the allowable heat generation amount. This makes it possible to prevent the heat generation amount W from increasing and exceeding the allowable heat generation amount of the constant current circuit 30.

The energy storage system 100 according to the first embodiment therefore performs an output voltage adjustment process to adjust the output voltage V1 from the DC-DC converter 20 in accordance with the battery voltage V2 of the secondary battery 40 so that the voltage difference ΔV is equal to or less than a predetermined voltage difference.

(Output voltage adjustment process)
5 is a flowchart showing an example of the flow of the output voltage adjustment process by the power storage system 100 according to the present embodiment 1. In FIG. 5, an operation of the control circuit 10 when the charging process for the secondary battery 40 is performed is shown.

First, in step S1, the state quantity acquisition unit 11 of the control circuit 10 acquires the battery voltage V2 of the secondary battery 40 as a state quantity detected by the detection unit 50. The state quantity acquisition unit 11 supplies the acquired battery voltage V2 to the output voltage determination unit 13.

In addition, in step S2, the state quantity acquisition unit 11 acquires the charging current I for the secondary battery 40 as a state quantity detected by the detection unit 50. The state quantity acquisition unit 11 supplies the acquired charging current I to the ΔV calculation unit 12. Note that the processing of step S2 may be performed prior to the processing of step S1, or may be performed simultaneously with the processing of step S1.

In step S3, the ΔV calculation unit 12 reads out the allowable heat generation amount from the memory unit 14. Then, based on the charging current I received from the state quantity acquisition unit 11 and the allowable heat generation amount read out from the memory unit 14, the ΔV calculation unit 12 calculates a voltage difference ΔV such that the heat generation amount W in the constant current circuit 30 is equal to or less than the allowable heat generation amount. The ΔV calculation unit 12 supplies the calculated voltage difference ΔV to the output voltage determination unit 13.

In step S4, the output voltage determination unit 13 determines the output voltage V1 of the DC-DC converter 20 based on the voltage difference ΔV received from the ΔV calculation unit 12 and the battery voltage V2 received from the state quantity acquisition unit 11. Here, since the voltage difference ΔV and the battery voltage V2 have the relationship shown in equation (2), the output voltage V1 of the DC-DC converter 20 is calculated by adding the battery voltage V2 to the voltage difference ΔV.

The output voltage V1 calculated at this time is calculated using the voltage difference ΔV based on the allowable heat generation amount. Therefore, the output voltage V1 is determined so that the voltage difference ΔV is equal to or less than a predetermined voltage difference.

The control circuit 10 periodically repeats the output voltage adjustment process described above, and controls the output voltage V1 of the DC-DC converter 20 so that the voltage difference ΔV is equal to or less than a predetermined voltage difference according to the battery voltage V2.

A specific example of adjusting the output voltage V1 by the output voltage adjustment process described above will be described. As an example, consider the case where the battery voltage V2 is 20V to 28V when the SOC of the secondary battery 40 is 0% to 100%, the charging current I output from the constant current circuit 30 is 0.3A, and the allowable heat generation is 0.3W.

If the battery voltage V2 is 20V when the SOC of the secondary battery 40 is 0% then the voltage difference ΔV calculated by the ΔV calculation unit 12 is 1V (=0.3W/0.3A) based on formula (1). Since the voltage difference ΔV is 1V and the battery voltage V2 is 20V, the output voltage V1 of the DC-DC converter 20 determined by the output voltage determination unit 13 is 21V (=20V+1V) based on formula (2). Therefore, in this case, the control circuit 10 outputs a control signal to the DC-DC converter 20 such that the output voltage V1 of the DC-DC converter 20 becomes 21V.

For example, even if the battery voltage V2 is 28 V when the SOC of the secondary battery 40 is 100%, the voltage difference ΔV calculated by the ΔV calculation unit 12 is 1 V based on formula (1). Since the voltage difference ΔV is 1 V and the battery voltage V2 is 28 V, the output voltage V1 of the DC-DC converter 20 determined by the output voltage determination unit 13 is 29 V (= 28 V + 1 V) based on formula (2). Therefore, in this case, the control circuit 10 outputs a control signal to the DC-DC converter 20 such that the output voltage V1 of the DC-DC converter 20 becomes 29 V.

In this way, by adjusting the output voltage V1 through the output voltage adjustment process, the voltage difference ΔV becomes 1 [V] regardless of the battery voltage V2 of the secondary battery 40, and the heat generation amount W in the constant current circuit 30 becomes 0.3 [W], which is the allowable heat generation amount. Therefore, the heat generation in the constant current circuit 30 can be reduced and the heat generation amount can be kept below the allowable heat generation amount.

On the other hand, if the output voltage V1 of the DC-DC converter 20 is a constant value of, for example, 30 [V], and the battery voltage V2 is 20 [V], the heat generation amount W in the constant current circuit 30 is 3 [W] (= (30 [V] - 20 [V]) x 0.3 [A]) based on formula (1).

In other words, in this case, the amount of heat generated W in the constant current circuit 30 exceeds the allowable amount of heat generated, and the constant current circuit 30 may be damaged. Therefore, in this case, in order to lower the temperature of the constant current circuit 30 and prevent damage to the constant current circuit 30, it is necessary to provide a heat dissipation means such as a heat sink in the constant current circuit 30, which results in an increase in the size of the energy storage system 100.

In this way, in the energy storage system 100, the output voltage V1 of the DC-DC converter 20 is adjusted so that the voltage difference ΔV is equal to or less than a predetermined voltage difference, and the heat generation amount W in the constant current circuit 30 is equal to or less than the allowable heat generation amount. Therefore, the heat generation in the constant current circuit 30 can be reduced.

In addition, by reducing the amount of heat generated W in the constant current circuit 30, heat dissipation means such as a fan or heat sink that were previously installed as a heat dissipation measure for the constant current circuit 30 are no longer necessary. This makes it possible to miniaturize the circuit (system).

<Modification>
The constant current circuit 30 as a current control circuit provided in the power storage system 100 according to the first embodiment is capable of outputting a constant current even when the input voltage changes. On the other hand, when a constant voltage is input, the constant current circuit 30 does not necessarily have to be used as a current control circuit that outputs a constant current, and a resistive element may be used instead of the constant current circuit. Hereinafter, a power storage system according to a modified example of the first embodiment will be described.

[Configuration of Power Storage System 100A]
Fig. 6 is a block diagram showing an example of a configuration of a power storage system 100A according to a modified example of the present embodiment 1. As shown in Fig. 6, the power storage system 100 includes a control circuit 10, a DC-DC converter 20, a resistive element 60, a secondary battery 40, and a detection unit 50. Note that the control circuit 10, the DC-DC converter 20, the secondary battery 40, and the detection unit 50 are similar to those in the power storage system 100 shown in Fig. 1, and therefore description thereof will be omitted here.

The resistive element 60 is, for example, a single element, and is provided to limit the flow of current. The value of the current output is determined by the voltage drop across the resistive element 60. In other words, the resistive element 60 outputs a charging current I to the secondary battery 40 based on the input output voltage V1 of the DC-DC converter 20. Note that the resistive element 60 is not limited to this example, and may be, for example, multiple elements connected in series or parallel.

In this way, even when the resistive element 60 is used as the current control circuit, the energy storage system 100A performs the output voltage adjustment process in the same manner as in the first embodiment, and adjusts the output voltage V1 of the DC-DC converter 20 so that the voltage difference ΔV is equal to or less than a predetermined voltage difference. This has the effect of reducing the amount of heat generated in the resistive element 60. In addition, because the current control circuit can be configured with a single resistive element 60, the number of parts in the energy storage system 100 can be reduced.

Note that repeated charging and discharging of the secondary battery 40 may cause degradation, such as a decrease in battery capacity. In this case, the energy storage system 100A may reduce the charging current I in the constant current charging method to a value smaller than normal.

When a resistive element 60 is used as a current control circuit as in the modified example, the charging current I can be changed, so it is also possible to accommodate cases where the charging current I needs to be reduced. For example, the control circuit 10 adjusts the output voltage V1 of the DC-DC converter 20 according to the degree of deterioration of the secondary battery 40. Specifically, the control circuit 10 determines the output voltage V1 based on the value of the charging current I to be supplied to the deteriorated secondary battery 40 and the allowable heat generation amount of the resistive element 60 so that the voltage difference ΔV is equal to or less than a predetermined voltage difference.

Although the above describes embodiment 1 and a modified version of embodiment 1, the present disclosure is not limited to the above-mentioned embodiment 1 and a modified version of embodiment 1, and various modifications and applications are possible without departing from the gist of the present disclosure.

In the first embodiment and the modified example of the first embodiment, the output voltage adjustment process is performed using the charging current I detected by the detection unit 50. However, this is not limited to this, and for example, the value of the charging current I may be set in advance. In this case, the charging current I for the secondary battery 40 can be determined based on the specifications of the secondary battery 40, such as the battery capacity.

In addition, in the first embodiment and the modified example of the first embodiment, the voltage conversion device outputs a constant voltage output voltage V1, and the current control circuit outputs a constant current charging current I, but the configuration of the energy storage system is not limited to this example. For example, as shown in FIG. 7, the voltage conversion device may output a constant voltage and a constant current.

Figure 7 is a circuit diagram for explaining an example of a configuration for outputting a constant voltage and a constant current. In the example shown in Figure 7, a voltage conversion device and a current control circuit are integrally configured, and a current sense resistor 231, an operational amplifier 232, and a Zener diode 233 are provided in the voltage variable circuit 22A, so that a constant voltage and a constant current are output from the voltage conversion device. Therefore, even when the voltage conversion device shown in this example is used, heat generation in the voltage conversion device can be reduced, as in the first embodiment and the modified example of the first embodiment.

10 Control circuit 11 State quantity acquisition unit 12 ΔV calculation unit 13 Output voltage determination unit 13
14 Memory unit 20, 20A DC-DC converter 21 Constant voltage output circuit 22, 22A Voltage variable circuit 30 Constant current circuit 40 Secondary battery 50 Detection unit 60 Resistance element 100, 100A Power storage system 211 Inductor 212 Switching element 213 Diode 214 Capacitor 215 Switching control unit 221, 232 Operational amplifier 231, 301 Current sense resistor 233 Zener diode 302 Operational amplifier 303 MOSFET

Claims (9)

An output voltage adjustment device that adjusts an output voltage of a voltage conversion device provided in a power storage system,
An acquisition unit for acquiring a battery voltage of the secondary battery;
an output voltage adjusting device comprising: a control circuit that controls the output voltage based on the battery voltage so that a difference between the output voltage of the voltage conversion device and the battery voltage is equal to or smaller than a predetermined voltage difference. the power storage system includes a current control circuit that outputs a charging current to the secondary battery,
The control circuit includes:
2. The output voltage adjusting device according to claim 1, wherein the output voltage is controlled so that the amount of heat generated in the current control circuit is equal to or less than an allowable amount of heat. The acquisition unit is
A charging current for the secondary battery is further obtained, the charging current being output from a constant current circuit;
The control circuit includes:
a ΔV calculation unit that calculates a voltage difference such that the amount of heat generated becomes the allowable amount of heat generated based on the charging current and an allowable amount of heat generated in the constant current circuit;
2. The output voltage adjusting device according to claim 1, further comprising an output voltage determining section that determines the output voltage based on the voltage difference and the battery voltage. A secondary battery that stores power;
a voltage conversion device that converts an externally supplied voltage into an output voltage;
a current control circuit for controlling a charging current for the secondary battery;
an acquisition unit that acquires a battery voltage of the secondary battery;
a control circuit that controls the output voltage based on the battery voltage so that a difference between the output voltage and the battery voltage is equal to or smaller than a predetermined voltage difference. The current control circuit includes:
5. The power storage system according to claim 4, which is a constant current circuit that outputs a constant current. The current control circuit includes:
The power storage system according to claim 4 , which is a resistive element. The control circuit includes:
The power storage system according to claim 6 , wherein the output voltage is adjusted in accordance with a degree of deterioration of the secondary battery. An output voltage adjustment method for adjusting an output voltage of a voltage conversion device provided in a power storage system, comprising:
Obtain the battery voltage of the secondary battery,
An output voltage regulating method for controlling the output voltage based on the battery voltage so that a difference between the output voltage and the battery voltage is equal to or smaller than a predetermined voltage difference. A program for causing a computer to execute the output voltage adjustment method according to claim 8.

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