JP2023160595A - DC power supply system - Google Patents

Abstract

To provide a stable DC power supply system by suppressing stoppage of the operation of a conversion device and maintaining redundancy of the conversion device.SOLUTION: A DC power supply system includes a DC bus 2, a first power supply 4A, a second power supply 4B, a first conversion device 5A, a second conversion device 5B, and a control circuit 7. On the basis of a first physical quantity that changes depending on the remaining amount of energy stored in the first power supply 4A and a second physical quantity that changes depending on the remaining amount of energy stored in the second power supply 4B, the control circuit 7 determines a first output voltage command value for the first conversion device 5A and a second output voltage command value for the second conversion device 5B. On the basis of the first output voltage command value and a first voltage droop characteristic, the first conversion device 5A increases or decreases the first power supply voltage to a first output voltage. The second conversion device 5B increases or decreases the second power supply voltage to a second output voltage on the basis of the second output voltage command value and a second voltage droop characteristic.SELECTED DRAWING: Figure 1

Description

Embodiments of the present invention relate to DC power supply systems.

2. Description of the Related Art In a system that outputs power from batteries connected in parallel to a DC bus, a technique is known in which the output current output to the DC bus is controlled by a converter between each battery and the DC bus.

As a related technology, Patent Document 1 discloses a switching power supply system. In the switching power supply system described in Patent Document 1, a switching power supply having a droop characteristic in which the output voltage drops as the output current increases is arranged between the power generation device and the DC bus.

More specifically, in the switching power supply system described in Patent Document 1, conversion is performed so that the output current to the DC bus is appropriately shared according to the power supply capacity of each power generation device as a power supply source. A droop characteristic in which the output voltage decreases as the output current increases is added to each switching power supply as a device, and the droop characteristic is set in advance. When each conversion device operates, a shift in control timing, a control error, etc. may occur. Therefore, even if the target voltage, which is the target value of the output to the DC bus, is set to be the same among a plurality of converters, an error may occur in the actual output voltage of each converter. Therefore, in the switching power supply system described in Patent Document 1, by adding a droop characteristic to the converter, the output voltage of a specific converter becomes higher than the output voltage of other converters. Prevent concentrated current output from a specific conversion device.

FIG. 14 shows an example of a DC power supply system in the prior art. In FIG. 14, the DC power supply system includes a load 91, a DC bus 92, a first battery group 94A, a second battery group 94B, a first battery management unit 93A, a second battery management unit 93B, a first It has a conversion device 95A, a second conversion device 95B, a first current detector 96A, a second current detector 96B, a first droop control section 97A, and a second droop control section 97B.

In the DC power supply system shown in FIG. 14, the first droop control unit 97A has a droop characteristic in which the output voltage of the first conversion device 95A decreases when the output current detected by the first current detector 96A increases. The output voltage command value is transmitted to the first conversion device 95A so that the output voltage is realized. Further, the second droop control section 97B controls the second droop control section so that a droop characteristic is exhibited in which the output voltage of the second conversion device 95B decreases when the output current detected by the second current detector 96B increases. The output voltage command value is transmitted to the conversion device 95B. In this way, the output voltage of one of the first converter 95A and the second converter 95B is higher than the output voltage of the other of the first converter 95A and the second converter 95B. This prevents current from being intensively output from one of the first converter 95A and the second converter 95B.

JP2020-22331A

However, in the switching power supply system shown in Patent Document 1, when batteries with different capacities or discharge characteristics are combined, or when there are individual differences between batteries of the same type, the switching power supply system shown in Patent Document 1 does not allow the battery to run out of batteries first. occurs. In this case, a converter powered by an individual whose battery level is zero stops operating, and the load on the remaining unit increases in a stepwise manner. As a result, there is a risk that the remaining units will be overloaded and the system will stop. Redundancy is also compromised because the number of active converters arranged in parallel is reduced.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a stable DC power supply system by suppressing operation stoppage of the converter and maintaining redundancy of the converter.

In order to solve the above problems, a DC power supply system according to an embodiment of the present invention includes a DC bus to which one or both of a load and a charging power source are connected, and a DC power supply system that stores first energy and generates DC power from the first energy. a second power source that stores second energy and outputs DC power from the second energy; and a second power source that is arranged between the first power source and the DC bus, and that is located on the first power source side. a first converter that steps up or steps down a first power supply voltage to a first output voltage on the DC bus side; a second converter that steps up and down a second output voltage on the DC bus side; and a first physical quantity that changes depending on the remaining amount of the first energy stored in the first power source; a first output unit that outputs a signal indicating the second energy; and a second output unit that detects or calculates a second physical quantity that changes depending on the remaining amount of the second energy stored in the second power supply and outputs a signal indicating the second physical quantity. determining a first output voltage command value for the first conversion device and a second output voltage command value for the second conversion device based on the second output unit, the first physical quantity, and the second physical quantity; a control circuit that outputs the determined first output voltage command value to the first conversion device and outputs the determined second output voltage command value to the second conversion device, the first conversion device is configured to increase or decrease the first power supply voltage to the first output voltage based on the first output voltage command value and a first voltage droop characteristic, and the second conversion device increases or decreases the second output voltage command value. and a second voltage droop characteristic, the second power supply voltage is increased or decreased to the second output voltage.

In order to solve the above problems, a DC power supply system according to another embodiment of the present invention includes a DC bus to which one or both of a load and a charging power source are connected, and a DC bus that stores first energy and a first power source that outputs DC power from energy; a second power source that stores second energy and outputs DC power from the second energy; a first converter that steps up or steps down a first power supply voltage on the first power supply side to a first output voltage on the DC bus side; and a second converter that is arranged between the second power supply and the DC bus, and that a second conversion device that steps up or down the power supply voltage to a second output voltage on the DC bus side; a first physical quantity that changes depending on the remaining amount of the first energy stored in the first power supply; a first output unit that outputs a signal indicating a first physical quantity; and a first output unit that detects or calculates a second physical quantity that changes depending on the remaining amount of the second energy stored in the second power supply, and a signal indicating the second physical quantity. a first current detector that detects the first output current of the first conversion device and outputs a first current signal indicating the first output current to a first droop control section; a second current detector that detects a second output current of the second conversion device and outputs a second current signal indicating the second output current to a second droop control unit; and the first physical quantity and the second physical quantity. , a first droop control value for the first droop control unit and a second droop control value for the second droop control unit are determined, and the determined first droop control value is applied to the first droop control a control circuit that outputs the determined second droop control value to the second droop control unit; and a control circuit that outputs the determined second droop control value to the second droop control unit; the first droop control section that adjusts the first voltage droop characteristic; and the second droop control section that adjusts the second voltage droop characteristic of the second conversion device based on the second droop control value received from the control circuit. The first droop control unit determines a first output voltage command value for the first conversion device based on the adjusted first voltage droop characteristic and the first output current, The determined first output voltage command value is outputted to the first conversion device, and the second droop control section outputs the determined first output voltage command value to the first conversion device, and the second droop control unit outputs the first output voltage command value based on the adjusted second voltage droop characteristic and the second output current. The method is characterized in that a second output voltage command value for the second conversion device is determined, and the determined second output voltage command value is output to the second conversion device.

According to the present invention, a stable DC power supply system can be provided by suppressing operation stoppage of the converter and maintaining redundancy of the converter.

FIG. 1 is a diagram schematically showing an example of a circuit configuration of a DC power supply system in a first embodiment. FIG. 2 is a diagram for explaining voltage droop characteristics of the converter. FIG. 3 is a diagram illustrating an example of the relationship between the remaining battery power and the output voltage command value for the conversion device in a comparative example. FIG. 4 is a diagram illustrating an example of the relationship between the remaining battery power and the output voltage command value for the conversion device in the first embodiment. FIG. 5 is a diagram schematically showing how the first output voltage command value for the first converter is changed under conditions where the first converter has voltage droop characteristics. FIG. 6 is a diagram schematically showing an example of the circuit configuration of the DC power supply system in the first embodiment. FIG. 7 is a diagram illustrating an example of the relationship between the remaining battery power and the output voltage command value for the conversion device regarding the comparative example. FIG. 8 is a diagram illustrating an example of the relationship between the remaining battery power and the output voltage command value for the conversion device in the first embodiment. FIG. 9 is a diagram schematically showing an example of a circuit configuration of a DC power supply system in the second embodiment. FIG. 10 is a diagram schematically showing an example of a circuit configuration of a DC power supply system in the third embodiment. FIG. 11 is a diagram showing an example of the voltage droop characteristic of the converter of the DC power supply system in the third embodiment. FIG. 12 is a diagram schematically showing a state after the voltage droop characteristic of the first conversion device is changed. FIG. 13 is a diagram schematically showing an example of a circuit configuration of a DC power supply system in the third embodiment. FIG. 14 is a diagram schematically showing a circuit configuration of a conventional DC power supply system.

Hereinafter, a DC power supply system 100 in an embodiment will be described with reference to the accompanying drawings. In the following description, members and parts having the same functions are designated by the same reference numerals, and repeated explanations of members and parts designated by the same reference numerals will be omitted.

(First embodiment)
A DC power supply system 100A according to the first embodiment will be described with reference to FIGS. 1 to 8. FIG. 1 is a diagram schematically showing an example of a circuit configuration of a DC power supply system 100A in the first embodiment. FIG. 2 is a diagram for explaining voltage droop characteristics of the converter (5A, 5B). FIG. 3 is a diagram illustrating an example of the relationship between the remaining battery power and the output voltage command value for the conversion device (5A, 5B) in a comparative example. FIG. 4 is a diagram showing an example of the relationship between the remaining battery power and the output voltage command value for the conversion device (5A, 5B) in the first embodiment. FIG. 5 is a diagram schematically showing how the first output voltage command value for the first converter 5A is changed under conditions where the first converter 5A has voltage droop characteristics. FIG. 6 is a diagram schematically showing an example of the circuit configuration of the DC power supply system 100A in the first embodiment. Note that FIG. 6 shows how the batteries (40A, 40B) are being charged. FIG. 7 is a diagram illustrating an example of the relationship between the remaining battery power and the output voltage command value for the conversion device (5A, 5B) regarding the comparative example. FIG. 8 is a diagram showing an example of the relationship between the remaining battery power and the output voltage command value for the conversion device (5A, 5B) in the first embodiment.

(composition)
In the example shown in FIG. 1, the DC power supply system 100A includes at least one load 1A, a DC bus 2, a first power source 4A, a second power source 4B, and a first battery management unit 3A (hereinafter referred to as a battery management unit). management unit is referred to as a "BMU"), a second BMU 3B, a first conversion device 5A, a second conversion device 5B, a first output section 6A, a second output section 6B, and a control circuit 7. and. Note that one of the first BMU 3A and the second BMU 3B, or both the first BMU 3A and the second BMU 3B may be omitted.

Moreover, at least one load 1A may be replaced with at least one charging power source 1B. Alternatively, the DC power supply system 100A may include at least one charging power source 1B in addition to at least one load 1A. In other words, the DC bus 2 is connected to one or both of the load 1A and the charging power source 1B.

In the example shown in FIG. 1, the load 1A is configured by, for example, a DC load or a combination of a converter and an AC load, and consumes power supplied from the DC bus 2. In addition, in the example shown in FIG. 1, when the load 1A is replaced with the charging power source 1B, or when the DC power supply system 100A includes the charging power source 1B in addition to the load 1A, the charging power source 1B supplies power to the first power source 4A and/or the second power source 4B via the DC bus 2. In this way, the amount of energy stored in the first power source 4A and/or the second power source 4B increases.

The first power source 4A stores the first energy and outputs DC power from the first energy. The first power source 4A is, for example, a rechargeable first battery 40A (more specifically, a first battery group). The first rechargeable battery 40A is, for example, a chemical battery that generates DC power from first energy through a chemical reaction. The first rechargeable battery 40A may be a lithium ion battery.

In the first embodiment (or the second embodiment described later, or the third embodiment described later), the first power source 4A is a fuel cell (a fuel cell is a type of chemical cell). It doesn't matter if there is. The fuel cell generates DC power from the fuel as the first energy through a chemical reaction between a fuel such as hydrogen and oxygen. Alternatively, in the first embodiment (or the second embodiment described later, or the third embodiment described later), the first power source 4A is a power source that stores kinetic energy, such as a flywheel. Alternatively, it may be a power source that stores elastic energy or thermal energy. Further alternatively, the first power source 4A may be a power source that stores persistent current, such as a superconducting coil.

The second power source 4B stores second energy and outputs DC power from the second energy. The second power source 4B is, for example, a rechargeable second battery 40B (more specifically, a second battery group). The rechargeable second battery 40B is, for example, a chemical battery that generates DC power from second energy through a chemical reaction. The second rechargeable battery 40B may be a lithium ion battery.

In the first embodiment (or the second embodiment described later, or the third embodiment described later), the second power source 4B is a fuel cell (a fuel cell is a type of chemical cell). It doesn't matter if there is. The fuel cell generates DC power from the fuel as second energy through a chemical reaction between a fuel such as hydrogen and oxygen. Alternatively, in the first embodiment (or the second embodiment described later, or the third embodiment described later), the second power source 4B is a power source that stores kinetic energy, such as a flywheel. Alternatively, it may be a power source that stores elastic energy or thermal energy. Further alternatively, the second power source 4B may be a power source that stores persistent current, such as a superconducting coil.

The first power source 4A and the second power source 4B may be the same type of power source (for example, both may be rechargeable batteries). Alternatively, the first power source 4A and the second power source 4B may be different types of power sources (for example, the former may be a rechargeable battery and the latter may be a power source other than a rechargeable battery). ).

In the following, the first power source 4A is a rechargeable first battery 40A (for example, a first battery group), and the second power source 4B is a rechargeable second battery 40B (for example, a second battery group). An example will be explained below. However, in the first embodiment, at least one of the first power source 4A and the second power source 4B may be a power source other than a rechargeable battery.

In other words, in the description of the first embodiment below, "first battery 40A", "second battery 40B", "battery voltage", "first battery voltage", "second battery voltage", "battery "remaining amount", "first battery remaining amount", and "second battery remaining amount" are respectively "first power supply 4A", "second power supply 4B", "power supply voltage", "first power supply voltage", and " It can be read as "second power supply voltage", "remaining energy amount", "first remaining energy amount", and "second remaining energy amount".

The first BMU 3A monitors the state of the first battery 40A and/or protects the first battery 40A. In the example shown in FIG. 1, the first BMU 3A is installed in the first battery 40A. The second BMU 3B monitors the state of the second battery 40B and/or protects the second battery 40B. In the example shown in FIG. 1, the second BMU 3B is installed in the second battery 40B.

The first conversion device 5A is arranged between the first battery 40A and the DC bus 2, and converts the first battery voltage of the first battery 40A into the output voltage of the DC bus 2 (hereinafter referred to as "first output voltage"). ). More specifically, the first converter 5A converts the first voltage on the first battery 40A side based on the target voltage of the DC bus 2 (or the first output voltage command value described later) and the first voltage droop characteristic. 1 battery voltage is stepped up or down to the first output voltage on the DC bus 2 side.

In addition, in this specification, the first voltage droop characteristic refers to the change in the voltage droop characteristic of the first converter 5A as the output current (hereinafter referred to as "first output current") of the first converter 5A increases. 1 means the characteristic that the output voltage drops.

In the example shown in FIG. 1, the first battery 40A and the first converter 5A are connected via the first electric wire L1, and the first converter 5A and the DC bus 2 are connected via the second electric wire L2. ing. In this case, the first conversion device 5A increases or decreases the voltage on the first electric wire L1 to the voltage on the second electric wire L2.

With reference to FIG. 2, the first voltage droop characteristic of the first conversion device 5A will be described. In the example shown in FIG. 2, the target voltage of the DC bus 2 is voltage V1. In the example shown in FIG. 2, when the value of the first output current of the first converter 5A increases from the current value I1 to the current value I1', the value of the first output voltage of the first converter 5A increases. The voltage decreases from the value F1 to the voltage value F1' (see arrow AR1). On the other hand, in the example shown in FIG. 2, when the value of the first output current of the first converter 5A decreases from the current value I1' to the current value I1, the value of the first output voltage of the first converter 5A decreases. , increases from voltage value F1' to voltage value F1 (see arrow AR2).

In order for the first converter 5A to exhibit the first voltage droop characteristic, the DC power supply system 100A in the first embodiment has a first output current (more specifically, a second output current) of the first converter 5A. (current flowing through the electric wire L2) can be detected. The first conversion device 5A decreases (or increases) the first output voltage in accordance with the increase (or decrease) in the first output current. In the example shown in FIG. 1, the first current detector 9A that detects the first output current is incorporated in the first converter 5A, but the first current detector 9A and the first converter 5A are separate units. It may be.

The second conversion device 5B is arranged between the second battery 40B and the DC bus 2, and converts the second battery voltage of the second battery 40B into the output voltage of the DC bus 2 (hereinafter referred to as "second output voltage"). ). More specifically, the second conversion device 5B converts the second voltage on the second battery 40B side based on the target voltage of the DC bus 2 (or the second output voltage command value described below) and the second voltage droop characteristic. 2 battery voltage is increased or decreased to a second output voltage on the DC bus 2 side.

In addition, in this specification, the second voltage droop characteristic refers to the voltage droop characteristic of the second converter 5B as the output current (hereinafter referred to as "second output current") of the second converter 5B increases. 2 This means the characteristic that the output voltage drops.

In the example shown in FIG. 1, the second battery 40B and the second converter 5B are connected via the third electric wire L3, and the second converter 5B and the DC bus 2 are connected via the fourth electric wire L4. ing. In this case, the second conversion device 5B increases or decreases the voltage on the third electric wire L3 to the voltage on the fourth electric wire L4.

With reference to FIG. 2, the second voltage droop characteristic of the second conversion device 5B will be explained. In the example shown in FIG. 2, the target voltage of the DC bus 2 is voltage V1. In the example shown in FIG. 2, when the value of the second output current of the second converter 5B increases from the current value I1 to the current value I1', the value of the second output voltage of the second converter 5B increases. The voltage decreases from the value F1 to the voltage value F1' (see arrow AR3). On the other hand, in the example shown in FIG. 2, when the value of the second output current of the second converter 5B decreases from the current value I1' to the current value I1, the value of the second output voltage of the second converter 5B decreases. , increases from voltage value F1' to voltage value F1 (see arrow AR4).

In order for the second converter 5B to exhibit the second voltage droop characteristic, the DC power supply system 100A in the first embodiment has a second output current (more specifically, a fourth output current) of the second converter 5B. (current flowing through the electric wire L4) can be detected. The second conversion device 5B decreases (or increases) the second output voltage in accordance with the increase (or decrease) in the second output current. In the example shown in FIG. 1, the second current detector 9B that detects the second output current is incorporated in the second conversion device 5B, but the second current detector 9B and the second conversion device 5B are separate units. It may be.

In the example shown in FIG. 2, the second voltage droop characteristic of the second conversion device 5B is equal to the first voltage droop characteristic of the first conversion device 5A. Alternatively, the second voltage droop characteristic of the second conversion device 5B may be different from the first voltage droop characteristic of the first conversion device 5A.

As illustrated in FIG. 2, when each of the first converter 5A and the second converter 5B has a voltage droop characteristic, when the first converter 5A and the second converter 5B are operated in parallel, Cross currents are suppressed from occurring between the first converter 5A and the second converter 5B.

The first output unit 6A has a first output unit that changes depending on the remaining amount of first energy stored in the first power source 4A (more specifically, the first battery remaining amount that is the remaining battery amount of the first battery 40A). A physical quantity is detected or calculated, and a signal indicating the first physical quantity is output to the control circuit 7. The first physical quantity may be any physical quantity as long as it changes according to the first battery remaining amount of the first battery 40A. The first physical quantity may include a plurality of physical quantities that change depending on the first battery remaining amount of the first battery 40A. The first output section 6A is an arbitrary output section that outputs a signal indicating the first physical quantity to the control circuit 7. Note that it goes without saying that the signal may be output from the first output section 6A to the control circuit 7 through any element or configuration.

In the example shown in FIG. 1, the first physical quantity is the battery voltage of the first battery 40A (hereinafter referred to as "first battery voltage"), and the first output unit 6A is the first battery voltage of the first battery 40A. This is a first voltage detector 60A that detects a first battery voltage that changes depending on the remaining amount.

As the first voltage detector 60A, a voltage divider, an isolator, etc. are used. In the example shown in FIG. 1, the first voltage detector 60A detects the voltage in the first electric wire L1 between the first battery 40A and the first converter 5A as the first battery voltage.

Note that the first voltage detector 60A may be incorporated in a PLC (Programmable Logic Controller), the first conversion device 5A, the first BMU 3A, or the like.

The second output unit 6B has a second output unit that changes depending on the remaining amount of second energy stored in the second power source 4B (more specifically, the second battery remaining amount that is the remaining battery amount of the second battery 40B). A physical quantity is detected or calculated, and a signal indicating the second physical quantity is output to the control circuit 7. The second physical quantity may be any physical quantity that changes depending on the second battery remaining amount of the second battery 40B. The second physical quantity may include a plurality of physical quantities that change depending on the second battery remaining amount of the second battery 40B. The second output section 6B is an arbitrary output section that outputs a signal indicating the second physical quantity to the control circuit 7. Note that it goes without saying that the signal may be output from the second output section 6B to the control circuit 7 via any element or any configuration.

In the example shown in FIG. 1, the second physical quantity is the battery voltage of the second battery 40B (hereinafter referred to as "second battery voltage"), and the second output unit 6B is the second battery voltage of the second battery 40B. This is a second voltage detector 60B that detects a second battery voltage that changes depending on the remaining battery level.

As the second voltage detector 60B, a voltage divider, an isolator, etc. are used. In the example shown in FIG. 1, the second voltage detector 60B detects the voltage in the third electric wire L3 between the second battery 40B and the second conversion device 5B as the second battery voltage.

Note that the second voltage detector 60B may be incorporated in a PLC (Programmable Logic Controller), the second conversion device 5B, the second BMU 3B, or the like.

The control circuit 7 determines a first output voltage command value for the first converter 5A and a second output voltage command value for the second converter 5B based on the first physical quantity and the second physical quantity. More specifically, the control circuit 7 receives a signal indicating the first physical quantity from the first output section 6A, receives a signal indicating the second physical quantity from the second output section 6B, and performs the control circuit 7 based on the first physical quantity and the second physical quantity. Then, a first output voltage command value for the first converter 5A and a second output voltage command value for the second converter 5B are determined.

When the first output section 6A is the first voltage detector 60A and the second output section 6B is the second voltage detector 60B, the control circuit 7 is detected by the first voltage detector 60A. The first battery voltage (in other words, the first signal indicating the first battery voltage received from the first voltage detector 60A), and the second battery voltage detected by the second voltage detector 60B (in other words, the first signal indicating the first battery voltage received from the first voltage detector 60A). A first output voltage command value for the first converter 5A and a second output voltage command value for the second converter 5B are determined based on the second signal indicating the second battery voltage received from the second voltage detector 60B. do.

Further, the control circuit 7 outputs the determined first output voltage command value (in other words, the first control command corresponding to the first output voltage command value) to the first conversion device 5A, and outputs the determined second output voltage command value to the first conversion device 5A. The output voltage command value (in other words, the second control command corresponding to the second output voltage command value) is output to the second conversion device 5B.

The first conversion device 5A converts the first voltage droop characteristic based on the first output voltage command value received from the control circuit 7 (in other words, the first control command corresponding to the first output voltage command value) and the first voltage droop characteristic. The first battery voltage on the 1 battery 40A side is increased or decreased to the first output voltage on the DC bus 2 side. Further, the second conversion device 5B converts the second output voltage command value received from the control circuit 7 (in other words, the second control command corresponding to the second output voltage command value) and the second voltage droop characteristic. , the second battery voltage on the second battery 40B side is increased or decreased to the second output voltage on the DC bus 2 side.

(Action: Power supply to DC bus 2)
In the example shown in FIG. 1, the control circuit 7 controls the first battery for the first converter 5A so that the power burden ratio of the first battery 40A and the second battery 40B, which has a smaller remaining battery level, is reduced. An output voltage command value and a second output voltage command value for the second conversion device 5B are determined. Further, the control circuit 7 outputs a first control command corresponding to the determined first output voltage command value to the first conversion device 5A, and outputs a second control command corresponding to the determined second output voltage command value. It outputs to the second conversion device 5B. As a result, the first output voltage of the first converter 5A and/or the second output voltage of the second converter 5B change, and the power burden ratio of the battery with the smaller remaining battery level is reduced. In this way, it is possible to prevent large variations in the timing at which the remaining battery power reaches zero for each battery.

More specifically, in the example shown in FIG. 1, the control circuit 7 receives a first signal indicating the first battery voltage of the first battery 40A from the first voltage detector 60A, and receives a first signal from the second voltage detector 60B. A second signal indicating a second battery voltage of second battery 40B is received. The control circuit 7 calculates the first battery remaining amount of the first battery 40A based on the first battery voltage of the first battery 40A and the discharge characteristics of the first battery 40A, and calculates the second battery voltage and the second battery level of the second battery 40B. The second battery remaining amount of the second battery 40B is calculated based on the discharge characteristics of the second battery 40B.

When the first battery remaining amount of the first battery 40A is lower than the second battery remaining amount of the second battery 40B, the control circuit 7 reduces the power burden ratio of the first battery 40A and reduces the power of the second battery 40B. A first output voltage command value for the first converter 5A and a second output voltage command value for the second converter 5B are determined so that the burden ratio is increased.

Further, the control circuit 7 outputs a first control command corresponding to the determined first output voltage command value to the first conversion device 5A, and outputs a second control command corresponding to the determined second output voltage command value. It outputs to the second conversion device 5B.

The first conversion device 5A that receives the first control command reduces the first output voltage based on the first output voltage command value. In this way, the power burden ratio of the first battery 40A is reduced, and the power burden ratio of the second battery 40B increases. Alternatively or additionally, the second conversion device 5B receiving the second control command may increase the second output voltage based on the second output voltage command value.

On the other hand, when the second battery remaining amount of the second battery 40B is less than the first battery remaining amount of the first battery 40A, the control circuit 7 reduces the power burden ratio of the second battery 40B, and the first battery 40A The first output voltage command value for the first converter 5A and the second output voltage command value for the second converter 5B are determined so that the power burden ratio of is increased.

Further, the control circuit 7 outputs a first control command corresponding to the determined first output voltage command value to the first conversion device 5A, and outputs a second control command corresponding to the determined second output voltage command value. It outputs to the second conversion device 5B.

The second conversion device 5B that receives the second control command reduces the second output voltage based on the second output voltage command value. In this way, the power burden ratio of the second battery 40B is reduced, and the power burden ratio of the first battery 40A increases.

Note that in this specification, the first battery remaining amount may mean the amount of charge of the first battery 40A with respect to the amount of full charge of the first battery 40A (i.e., the ratio to the amount of full charge), or alternatively, Specifically, the first battery remaining amount may mean the amount of energy stored in the first battery 40A (that is, the amount of charge itself). Further, the second battery remaining amount may mean the amount of charge of the second battery 40B with respect to the amount of full charge of the second battery 40B (that is, the ratio to the amount of full charge), or alternatively, the remaining amount of the second battery The battery remaining amount may mean the amount of energy stored in the second battery 40B (that is, the amount of charge itself).

With reference to FIGS. 3 and 4, an example of the relationship between the remaining battery power of each battery (40A, 40B) and the output voltage command value for each converter (5A, 5B) in the comparative example (FIG. 3), and An example (FIG. 4) of the relationship between the remaining battery capacity of each battery (40A, 40B) and the output voltage command value for each conversion device (5A, 5B) in the first embodiment will be described. 3 and 4, as illustrated in FIG. 1, a load 1A is connected to the DC bus 2, and the first battery 40A and the second battery 40B supply power to the load 1A via the DC bus 2. An example of a case is assumed.

3(a) and 4(a) show temporal changes in the first output voltage command value for the first converter 5A and temporal changes in the first battery remaining amount of the first battery 40A. . In addition, FIGS. 3(b) and 4(b) show changes over time in the second output voltage command value for the second converter 5B and changes over time in the second battery remaining amount of the second battery 40B. ing. It is assumed that the time lapse in FIG. 3(a) and the time lapse in FIG. 3(b) are progressing simultaneously and in parallel. Similarly, it is assumed that the time lapse in FIG. 4(a) and the time lapse in FIG. 4(b) are progressing simultaneously in parallel.

In the example shown in FIGS. 3 and 4, until time t2, the first output voltage command value for the first converter 5A is voltage V1, and the second output voltage command value for the second converter 5B is voltage V1. Yes, and the first output voltage command value and the second output voltage command value are the same value. Furthermore, in the examples shown in FIGS. 3 and 4, the battery capacity of the first battery 40A is assumed to be smaller than the battery capacity of the second battery 40B.

If the battery capacity of the first battery 40A is smaller than the battery capacity of the second battery 40B, and each battery equally shares the power supplied to the DC bus 2, the remaining first battery capacity of the first battery 40A is: Compared to the second battery remaining capacity of the second battery 40B, the second battery level decreases quickly. Therefore, in the examples shown in FIGS. 3 and 4, the first battery remaining amount of the first battery 40A at time t2 is the remaining amount P1, and the second battery remaining amount of the second battery 40B at time t2 is the remaining amount P2. When, P1<P2.

In this state, as illustrated in FIG. 3, if the first output voltage command value for the first converter 5A and the second output voltage command value for the second converter 5B are maintained at voltage V1, then At t4, the first battery remaining amount of the first battery 40A becomes zero, and the first conversion device 5A stops. Such a stoppage of the first converter 5A may lead to overpower generation in the second converter 5B or a reduction in the redundancy of the converter.

Therefore, as illustrated in FIG. 4, according to the first embodiment, the control circuit 7 changes the first output voltage command value for the first conversion device 5A to a voltage V2 lower than the voltage V1 at time t2. and outputs a first control command corresponding to the first output voltage command value to the first conversion device 5A. The first conversion device 5A that receives the first control command increases or decreases the first battery voltage to the first output voltage based on the reduced first output voltage command value. As a result, the power burden ratio of the first battery 40A is reduced, and the power burden ratio of the second battery 40B is increased. In this way, the timing at which the amount of charge of the first battery 40A becomes zero can be made later than time t4.

Alternatively, at time t2, the control circuit 7 determines the second output voltage command value for the second conversion device 5B to be a voltage higher than the voltage V1, and performs the second control corresponding to the second output voltage command value. The command may be output to the second conversion device 5B. The second conversion device 5B that receives the second control command increases or decreases the second battery voltage to the second output voltage based on the increased second output voltage command value. As a result, the power burden ratio of the second battery 40B is increased, and the power burden ratio of the first battery 40A is reduced. In this way, the timing at which the remaining battery level of the first battery 40A becomes zero can be made later than time t4.

In addition, in the first embodiment, if a DC power supply system is adopted in which the power load of each battery is proportionally distributed according to the battery capacity of each battery, theoretically, the remaining battery capacity will be It is possible to operate multiple batteries so that the ratio of amounts does not vary. However, depending on how each battery is used or when batteries are replaced, there may be a difference in the ratio of remaining battery power to battery capacity for each battery. In this case, the remaining battery power of one battery becomes zero before the remaining battery power of the other batteries.

The first embodiment is also applicable to such a case. More specifically, the control circuit 7 controls the output voltage for each conversion device so that, among the plurality of batteries (40A, 40B), the power burden ratio of the battery with a small ratio of remaining battery power to battery capacity is reduced. A command value is determined, and a control command corresponding to the determined output voltage command value is output to each conversion device (5A, 5B). As a result, the power burden ratio of the battery with a relatively low battery remaining capacity (%) is reduced. As a result, the remaining battery capacity of one battery is prevented or suppressed from becoming zero before the remaining battery capacity of another battery. Note that "prevention" here means that the remaining battery power of a plurality of batteries becomes zero substantially at the same time. Moreover, "suppression" here means that the timing at which the remaining battery capacity of one battery reaches zero before the remaining battery capacity of another battery is delayed.

In the example shown in FIG. 4, the timing at which the first output voltage command value is changed is based on the first battery remaining amount of the first battery 40A (for example, the first battery voltage of the first battery 40A and the first battery 40A). This is only the timing when the first battery remaining capacity of the first battery calculated from the discharge characteristics of the first battery reaches a predetermined remaining capacity P1.

Alternatively, a plurality of timings at which the first output voltage command value is changed may be set. For example, at the timing when the first battery remaining amount of the first battery 40A reaches a first predetermined value, the first output voltage command value for the first converter 5A changes from voltage V1 to voltage V2 lower than voltage V1. Then, at the timing when the first battery remaining amount of the first battery 40A reaches a second predetermined value that is lower than the first predetermined value, the first output voltage command value for the first converter 5A changes from voltage V2 to voltage V2. It may be changed to a voltage lower than V2.

Further alternatively, the timing at which the first output voltage command value is changed is determined not only depending on the first battery remaining amount of the first battery 40A, but also depending on the first battery remaining amount of the first battery 40A. and time (for example, the discharge time from the first battery 40A, or the time until the first battery remaining capacity of the first battery 40A becomes zero when the first output voltage command value is not changed, etc.). may be determined based on.

Further, after the first output voltage command value for the first converter 5A is changed from voltage V1 to voltage V2, the first battery remaining amount of the first battery 40A and the second battery remaining amount of the second battery 40B are changed. At the matching timing, the first output voltage command value of the first conversion device 5A may be returned from the voltage V2 to the voltage V1.

In the example shown in FIG. 1, the number of converters (5A, 5B) connected in parallel to the DC bus 2 is two; however, the number of converters connected in parallel to the DC bus 2 is , may be three or more.

In the first embodiment, the first output voltage command value and/or Alternatively, in addition to the second output voltage command value for the second conversion device 5B being changed, each of the first conversion device 5A and the second conversion device 5B has a voltage droop characteristic.

An example in which the output voltage command value of the converter (5A, 5B) is changed under conditions where the converter (5A, 5B) has voltage droop characteristics will be described with reference to FIGS. 2 and 5.

FIG. 2 shows the state before the control circuit 7 outputs the first control command and the second control command for reducing the power burden ratio of the first battery 40A and the second battery 40B, which has a lower battery remaining capacity. An example of the relationship between the first output current of the first converter 5A and the first output voltage of the first converter 5A at a time point (hereinafter referred to as "time t1"), and the relationship between the first output voltage of the first converter 5A and the relationship of the second converter 5B. It is a graph which shows an example of the relationship between the 2nd output current and the 2nd output voltage of the 2nd conversion device 5B. Note that time t1 is an arbitrary time between time t0 and time t2 in the example shown in FIG.

On the other hand, FIG. 5 shows that the control circuit 7 outputs a first control command and a second control command for reducing the power burden ratio of the first battery 40A and the second battery 40B, whichever has a smaller remaining battery level. An example of the relationship between the first output current of the first converter 5A and the first output voltage of the first converter 5A at a later time point (hereinafter referred to as "time t3"), and the second converter It is a graph which shows an example of the relationship between the 2nd output current of 5B, and the 2nd output voltage of 2nd converter 5B. Note that time t3 is an arbitrary time between time t2 and time t4 in the example shown in FIG.

In the example shown in FIG. 2, at time t1, the first output voltage command value that the first conversion device 5A receives from the control circuit 7 and the second output voltage command value that the second conversion device 5B receives from the control circuit 7 are The first output voltage command value and the second output voltage command value each match the value of the target voltage V1 of the DC bus 2. Since the first converter 5A has a first voltage droop characteristic, the value of the first output voltage of the first converter 5A at time t1 is the voltage value F1, and the first output of the first converter 5A at time t1 The value of the current is a current value I1. Since the second conversion device 5B has a second voltage droop characteristic, the value of the second output voltage of the second conversion device 5B at time t1 is the voltage value F1, and the second output voltage of the second conversion device 5B at time t1 is The value of the current is a current value I1. For simplicity, at time t1, the first voltage droop characteristic and the second voltage droop characteristic are the same, and the value of the first output voltage of the first converter 5A and the second output voltage of the second converter 5B are different. It is assumed that the values of the output voltages are the same, and the value of the first output current of the first converter 5A and the value of the second output current of the second converter 5B are the same.

At time t1, when the first output current of the first converter 5A increases, the first output voltage of the first converter 5A decreases (see arrow AR1), and the first output current of the first converter 5A decreases. When the voltage decreases, the first output voltage of the first conversion device 5A increases. Furthermore, at time t1, when the second output current of the second converter 5B increases, the second output voltage of the second converter 5B decreases (see arrow AR3), and the second output of the second converter 5B decreases (see arrow AR3). When the current decreases, the second output voltage of the second conversion device 5B increases. These voltage droop characteristics are exhibited regardless of the remaining battery level of each battery.

In the example shown in FIG. 5, at time t3 after time t2, the first conversion device The first output voltage command value that 5A receives from the control circuit 7 is lowered from the voltage V1 (more specifically, the value of the target voltage V1 of the DC bus 2) to the voltage V2 (see arrow AR5). The second output voltage command value that the second conversion device 5B receives from the control circuit 7 is maintained at the voltage V1 (more specifically, the value of the target voltage V1 of the DC bus 2).

Since the first converter 5A has a first voltage droop characteristic, the value of the first output voltage of the first converter 5A at time t3 is the second voltage value F, and the value of the first output voltage of the first converter 5A at time t3 is the second voltage value F. The value of one output current is the current value I2. Since the second converter 5B has a second voltage droop characteristic, the value of the second output voltage of the second converter 5B at time t3 is the second voltage value F, and the value of the second output voltage of the second converter 5B at time t3 is the second voltage value F. The value of the second output current is the current value I3.

In the example shown in FIG. 5, current value I2 is smaller than current value I3. Therefore, of the first battery 40A and the second battery 40B, the power burden ratio of the first battery 40A (see the hatched area with dots) is reduced, and the first battery 40A has a lower remaining battery power. Among the second batteries 40B, the power burden ratio (see the hatched area) of the second battery 40B with a larger remaining battery level is increased.

At time t3, when the first output current of the first converter 5A increases, the first output voltage of the first converter 5A decreases (see arrow AR6), and the first output current of the first converter 5A decreases. When the voltage decreases, the first output voltage of the first converter 5A increases (see arrow AR7). Furthermore, at time t3, when the second output current of the second converter 5B increases, the second output voltage of the second converter 5B decreases (see arrow AR8), and the second output of the second converter 5B decreases (see arrow AR8). When the current decreases, the second output voltage of the second conversion device 5B increases (see arrow AR9). These droop characteristics are exhibited even after the output voltage command value of the conversion device (5A, 5B) is changed based on the remaining battery level of each battery.

(Action: Power reception from DC bus 2)
In the example shown in FIG. 6, the control circuit 7 controls the first battery 40A and the second battery 40B so that the ratio of receiving power to the first battery 40A and the second battery 40B, which has a higher remaining battery level, is reduced. An output voltage command value and a second output voltage command value for the second conversion device 5B are determined.

Further, the control circuit 7 outputs a first control command corresponding to the determined first output voltage command value to the first conversion device 5A, and outputs a second control command corresponding to the determined second output voltage command value. It is output to the second conversion device 5B. As a result, the first output voltage of the first converter 5A and/or the second output voltage of the second converter 5B change, and the proportion of power received by the battery with more remaining energy is reduced. In this way, it is possible to prevent the timing of full charging from varying greatly from battery to battery.

More specifically, in the example shown in FIG. 6, the control circuit 7 receives a first signal indicating the first battery voltage of the first battery 40A from the first voltage detector 60A, and receives a first signal from the second voltage detector 60B. A second signal indicating a second battery voltage of second battery 40B is received. The control circuit 7 calculates the first battery remaining amount of the first battery 40A based on the first battery voltage of the first battery 40A and the discharge characteristics of the first battery 40A, and calculates the second battery voltage and the second battery level of the second battery 40B. The second battery remaining amount of the second battery 40B is calculated based on the discharge characteristics of the second battery 40B.

When the first battery remaining amount of the first battery 40A is greater than the second battery remaining amount of the second battery 40B, the control circuit 7 reduces the power reception ratio of the first battery 40A, and reduces the power reception ratio of the second battery 40B. A first output voltage command value for the first converter 5A and a second output voltage command value for the second converter 5B are determined so that the power reception ratio is increased.

Further, the control circuit 7 outputs a first control command corresponding to the determined first output voltage command value to the first conversion device 5A, and outputs a second control command corresponding to the determined second output voltage command value. It is output to the second conversion device 5B.

The first conversion device 5A that receives the first control command increases the first output voltage based on the first output voltage command value. In this way, the power reception ratio of the first battery 40A is reduced, and the power reception ratio of the second battery 40B is increased.

With reference to FIGS. 7 and 8, an example of the relationship between the remaining battery power of each battery (40A, 40B) and the output voltage command value for each conversion device (5A, 5B) in the comparative example (FIG. 7), and An example (FIG. 8) of the relationship between the remaining battery capacity of each battery (40A, 40B) and the output voltage command value for each conversion device (5A, 5B) in the first embodiment will be described. 7 and 8, as illustrated in FIG. 6, the charging power source 1B is connected to the DC bus 2, and the first battery 40A and the second battery 40B are connected to the charging power source 1B via the DC bus 2. An example is assumed in which power is received from the power source 1B.

FIGS. 7(a) and 8(a) show changes over time in the first output voltage command value for the first converter 5A and changes over time in the first battery remaining amount of the first battery 40A. . Further, FIGS. 7(b) and 8(b) show changes over time in the second output voltage command value for the second converter 5B and changes over time in the remaining battery level of the second battery 40B. ing. It is assumed that the time lapse in FIG. 7(a) and the time lapse in FIG. 7(b) are progressing simultaneously and in parallel. Similarly, it is assumed that the time passage in FIG. 8(a) and the time passage in FIG. 8(b) are progressing simultaneously and in parallel.

In the examples shown in FIGS. 7 and 8, until time t2, the first output voltage command value for the first converter 5A is voltage V1, and the second output voltage command value for the second converter 5B is voltage V1. Yes, and the first output voltage command value and the second output voltage command value are the same value.

In the example shown in FIG. 7, at time t2, the first battery remaining amount P of the first battery 40A is greater than the second battery remaining amount P' of the second battery 40B. In the example shown in FIG. 7, when the proportion of power received from the DC bus 2 is maintained for each of the first battery 40A and the second battery 40B, at time t4, the first battery 40A is replaced by the second battery 40B. It will be fully charged first.

When the first battery 40A is fully charged, the first conversion device 5A stops. Such a stoppage of the first converter 5A may lead to overpower generation in the second converter 5B or a reduction in the redundancy of the converter.

Therefore, as illustrated in FIG. 8, according to the first embodiment, the control circuit 7 changes the first output voltage command value for the first conversion device 5A to a voltage V3 higher than the voltage V1 at time t2. and outputs a first control command corresponding to the first output voltage command value to the first conversion device 5A. The first conversion device 5A that receives the first control command increases or decreases the first battery voltage to the first output voltage based on the increased first output voltage command value. As a result, the power reception ratio of the first battery 40A is reduced, and the power reception ratio of the second battery 40B is increased. In this way, the timing at which the first battery 40A becomes fully charged can be delayed from time t4.

In the example shown in FIG. 8, the first output voltage command value is changed only when the first battery remaining amount of the first battery 40A reaches a predetermined remaining amount (P).

Alternatively, a plurality of timings at which the first output voltage command value is changed may be set. For example, at the timing when the first battery remaining amount of the first battery 40A reaches a first predetermined value, the first output voltage command value for the first converter 5A changes from voltage V1 to voltage V3 higher than voltage V1. Then, at the timing when the first battery remaining capacity of the first battery 40A reaches a second predetermined value that is higher than the first predetermined value, the first output voltage command value for the first converter 5A changes from voltage V3 to voltage V3. The voltage may be changed to a voltage higher than V3.

Further alternatively, the timing at which the first output voltage command value is changed is determined not only depending on the first battery remaining amount of the first battery 40A, but also depending on the first battery remaining amount of the first battery 40A. and time (for example, the charging time of the first battery 40A, or the time until the first battery 40A is fully charged when the first output voltage command value is not changed). Good too.

Further, after the first output voltage command value for the first converter 5A is changed from the voltage V1 to the voltage V3, the first battery remaining amount of the first battery 40A and the second battery remaining amount of the second battery 40B are changed. At the matching timing, the first output voltage command value of the first conversion device 5A may be returned from the voltage V3 to the voltage V1.

In the first embodiment, the first output voltage command value and/or Alternatively, in addition to the second output voltage command value for the second conversion device 5B being changed, each of the first conversion device 5A and the second conversion device 5B has a voltage droop characteristic. Since the voltage droop characteristic has already been explained using FIGS. 2, 5, etc., a repeated explanation of the voltage droop characteristic will be omitted.

(effect)
In the DC power supply system 100A in the first embodiment, when the energy capacity of each power source or the characteristics of each power source are different, the output voltage command value of at least one converter is changed according to the remaining energy amount of each power source. As a result, the power burden ratio of each power source is adjusted. In this way, the remaining energy of one power source is prevented or suppressed from becoming zero before the remaining energy of another power source. As a result, operation of the plurality of converters is maintained, overpowering of a particular converter is prevented, and redundancy of the converters is maintained. Thus, in the first embodiment, a stable DC power supply system is provided.

Further, in the DC power supply system 100A in the first embodiment, the output voltage command value of at least one converter is changed according to the remaining energy level of each power source, and the voltage droop characteristic of each converter is changed. and the output voltage of the converter is changed based on the conversion device. Therefore, even before changing the output voltage command value of at least one converter according to the remaining energy level of each power source, and after changing the output voltage command value of at least one converting apparatus according to the remaining energy level of each power source. Also, generation of cross current between the plurality of converters is suppressed.

Further, in the first embodiment, when power is supplied from the charging power source 1B to a plurality of power sources (4A, 4B) via the DC bus 2, the remaining energy of each power source (in other words, each power source By changing the output voltage command value of at least one converter according to the energy storage amount), the power reception ratio of each power source is adjusted. In this way, the energy storage amount of one power source is prevented or suppressed from becoming full before the energy storage amount of another power source. As a result, operation of the plurality of converters is maintained, overpowering of a particular converter is prevented, and redundancy of the converters is maintained. Thus, in the first embodiment, a stable DC power supply system is provided.

(Second embodiment)
With reference to FIG. 9, a DC power supply system 100B in the second embodiment will be described. FIG. 9 is a diagram schematically showing an example of a circuit configuration of a DC power supply system 100B in the second embodiment.

The second embodiment will be described with a focus on points that are different from the first embodiment. On the other hand, in the second embodiment, repetitive explanations of matters already explained in the first embodiment will be omitted. Therefore, it goes without saying that matters already explained in the first embodiment can be applied to the second embodiment even if they are not explicitly explained in the second embodiment.

(composition)
In the second embodiment, the first output section 6A is the "first estimated charge amount calculation section 62A", the second output section 6B is the "second estimated charge amount calculation section 62B", and the second output section 6B is the "second estimated charge amount calculation section 62B". The first physical quantity detected or calculated by the first output unit 6A (first estimated charge amount calculation unit 62A) is "estimated charge amount of the first battery 40A (hereinafter referred to as "first estimated charge amount")", The second physical quantity detected or calculated by the second output unit 6B (second estimated charge amount calculation unit 62B) is “estimated charge amount of the second battery 40B (hereinafter referred to as “second estimated charge amount”)”. This embodiment differs from the first embodiment in this point. In other respects, the second embodiment is similar to the first embodiment.

A DC power supply system 100B in the second embodiment includes a DC bus 2 to which one or both of a load 1A and a charging power source 1B are connected, a first battery 40A as a first power source 4A, and a second power source 4B as a second power source 4B. the second battery 40B, the first BMU 3A, the second BMU 3B, the first conversion device 5A, the second conversion device 5B, and the first estimated charge amount calculation unit 62A as the first output unit 6A. , a second estimated charge amount calculation section 62B as a second output section 6B, and a control circuit 7. Note that one of the first BMU 3A and the second BMU 3B, or both the first BMU 3A and the second BMU 3B may be omitted.

(effect)
In the second embodiment, the configuration or control associated with the first estimated charge amount calculation section 62A and the second estimated charge amount calculation section 62B will be mainly explained, and repetitive explanations of other matters will be omitted. do.

The first estimated charge amount calculation unit 62A calculates a first estimated charge amount (for example, SOC (State of Charge)) of the first battery 40A, and sends a third signal indicating the first estimated charge amount to the control circuit 7. Output to. Note that it goes without saying that the third signal may be output from the first estimated charge amount calculation unit 62A to the control circuit 7 via any element or any configuration.

The second estimated charge amount calculation unit 62B calculates a second estimated charge amount (for example, SOC (State of Charge)) of the second battery 40B, and sends a fourth signal indicating the second estimated charge amount to the control circuit 7. Output to. Note that it goes without saying that the output of the fourth signal from the second estimated charge amount calculating section 62B to the control circuit 7 may be performed via any element or any configuration.

In the example shown in FIG. 9, the first estimated charge amount calculation unit 62A calculates the first estimated charge amount of the first battery 40A based on the signal received from the first BMU 3A, and calculates the first estimated charge amount of the first battery 40A. The amount calculation unit 62B calculates the second estimated charge amount of the second battery 40B based on the signal received from the second BMU 3B. Alternatively, the first estimated charge amount calculation unit 62A may calculate the first estimated charge amount of the first battery 40A based on the signal received from the first conversion device 5A, and the second estimated charge amount may be calculated based on the signal received from the first conversion device 5A. The amount calculation unit 62B may calculate the second estimated charge amount of the second battery 40B based on the signal received from the second conversion device 5B. For example, the first estimated charge amount of the first battery 40A may be calculated based on the integrated value of the current passing through the first electric wire L1, or a combination of the integrated value and environmental conditions such as temperature. Further, the second estimated charge amount of the second battery 40B may be calculated based on the integrated value of the current passing through the third electric wire L3, or a combination of the integrated value and environmental conditions such as temperature.

Further alternatively, the first estimated charge amount calculation unit 62A calculates the amount of charge based on the first battery charge amount received from another control circuit other than the control circuit 7, a PLC, etc., or electricity amount information for estimating the first battery charge amount. , the estimated charge amount of the first battery 40A may be calculated. Similarly, the second estimated charge amount calculation unit 62B calculates the second battery charge amount received from another control circuit other than the control circuit 7, PLC, etc. or the amount of electricity information for estimating the second battery charge amount. The estimated charge amount of the two batteries 40B may be calculated.

Note that "calculating the estimated charge amount" includes the first BMU 3A, the second BMU 3B, the first conversion device 5A, the second conversion device 5B, another control circuit other than the control circuit 7, or a PLC, etc. This also includes using the estimated charge amount calculated by .

In the example shown in FIG. 9, the control circuit 7 provides a first output voltage command value for the first converter 5A and a second output for the second converter 5B based on the first estimated charge amount and the second estimated charge amount. Determine the voltage command value. More specifically, when the first estimated charge amount of the first battery 40A is smaller than the second estimated charge amount of the second battery 40B, the control circuit 7 reduces the power burden ratio of the first battery 40A, A first output voltage command value for the first converter 5A and a second output voltage command value for the second converter 5B are determined so that the power burden ratio of the second battery 40B is increased.

(effect)
The second embodiment has the same effects as the first embodiment.

(Third embodiment)
A DC power supply system 100C according to the third embodiment will be described with reference to FIGS. 10 to 13. FIG. 10 is a diagram schematically showing an example of a circuit configuration of a DC power supply system 100C in the third embodiment. FIG. 11 is a diagram showing an example of voltage droop characteristics of the converter (5A, 5B) of the DC power supply system 100C in the third embodiment. FIG. 12 is a diagram schematically showing a state after the voltage droop characteristic of the first conversion device 5A is changed. FIG. 13 is a diagram schematically showing an example of a circuit configuration of a DC power supply system 100C in the third embodiment. Note that FIG. 13 shows how the batteries (40A, 40B) are being charged.

The third embodiment will be described with a focus on points that are different from the first and second embodiments. On the other hand, in the third embodiment, repetitive explanations of matters already explained in the first embodiment or the second embodiment will be omitted. Therefore, it goes without saying that matters already explained in the first embodiment or the second embodiment can be applied to the third embodiment even if they are not explicitly explained in the third embodiment.

(composition)
The DC power supply system 100C in the third embodiment has a first droop control section 10A that adjusts the first voltage droop characteristic, and a second droop control section 10B that adjusts the second voltage droop characteristic. This is different from the DC power supply system 100A in the first embodiment and the DC power supply system 100B in the second embodiment. In other respects, the third embodiment is similar to the first embodiment or the second embodiment.

A DC power supply system 100C in the third embodiment, as illustrated in FIG. 1 battery 40A), a second power source 4B (e.g., second battery 40B), a first BMU 3A, a second BMU 3B, a first conversion device 5A, a second conversion device 5B, and a first output section. 6A, a second output section 6B, a first current detector 9A, a second current detector 9B, a first droop control section 10A, and a second droop control section 10B. Note that one of the first BMU 3A and the second BMU 3B, or both the first BMU 3A and the second BMU 3B may be omitted.

Load 1A, charging power source 1B, DC bus 2, first power source 4A (for example, first battery 40A), second power source 4B (for example, second battery 40B), first BMU 3A, second BMU 3B, first Since the converting device 5A, the second converting device 5B, the first output section 6A, and the second output section 6B have already been explained in the first embodiment or the second embodiment, these configurations will be repeated. Explanation will be omitted.

In the following, the first power source 4A is a rechargeable first battery 40A (for example, a first battery group), and the second power source 4B is a rechargeable second battery 40B (for example, a second battery group). An example will be explained below. However, in the third embodiment, at least one of the first power source 4A and the second power source 4B may be a power source other than a rechargeable battery.

In other words, in the description of the third embodiment below, "first battery 40A", "second battery 40B", "battery voltage", "first battery voltage", "second battery voltage", "battery "remaining amount", "first battery remaining amount", and "second battery remaining amount" are respectively "first power supply 4A", "second power supply 4B", "power supply voltage", "first power supply voltage", and " It can be read as "second power supply voltage", "remaining energy amount", "first remaining energy amount", and "second remaining energy amount".

The first output unit 6A detects or calculates a first physical quantity that changes depending on the first battery remaining amount of the first battery 40A, and outputs a signal indicating the first physical quantity to the control circuit 7. The first physical quantity may be any physical quantity as long as it changes according to the first battery remaining amount of the first battery 40A. The first physical quantity may include a plurality of physical quantities that change depending on the first battery remaining amount of the first battery 40A. The first output section 6A is an arbitrary output section that outputs a signal indicating the first physical quantity to the control circuit 7. Note that it goes without saying that the signal may be output from the first output section 6A to the control circuit 7 through any element or configuration. The first output unit 6A may include a first voltage detector 60A that detects a first battery voltage of the first battery 40A, and a first estimated charge that calculates a first estimated charge amount of the first battery 40A. It may include the amount calculation section 62A, or it may include both the first voltage detector 60A and the first estimated charge amount calculation section 62A.

The second output unit 6B detects or calculates a second physical quantity that changes depending on the second battery remaining amount of the second battery 40B, and outputs a signal indicating the second physical quantity to the control circuit 7. The second physical quantity may be any physical quantity that changes depending on the second battery remaining amount of the second battery 40B. The second physical quantity may include a plurality of physical quantities that change depending on the second battery remaining amount of the second battery 40B. The second output section 6B is an arbitrary output section that outputs a signal indicating the second physical quantity to the control circuit 7. Note that it goes without saying that the signal may be output from the second output section 6B to the control circuit 7 via any element or any configuration. The second output unit 6B may include a second voltage detector 60B that detects a second battery voltage of the second battery 40B, and a second estimated charge that calculates a second estimated charge amount of the second battery 40B. It may include the amount calculation section 62B, or it may include both the second voltage detector 60B and the second estimated charge amount calculation section 62B.

The first voltage detector 60A, the second voltage detector 60B, the first estimated charge amount calculation section 62A, and the second estimated charge amount calculation section 62B are described in the first embodiment or the second embodiment. Since these configurations have already been explained, repeated explanations regarding these configurations will be omitted.

The first current detector 9A detects the first output current that the first converter 5A outputs to the DC bus 2. More specifically, the first current detector 9A detects the first output current flowing through the second electric wire L2 between the first converter 5A and the DC bus 2. Further, the first current detector 9A outputs a first current signal indicating the first output current to the first droop control section 10A. As the first current detector 9A, for example, a CT (Current Transformer), a current probe, or the like is used. Note that the first current detector 9A may be incorporated in the PLC, the first conversion device 5A, the first BMU 3A, etc.

The second current detector 9B detects the second output current that the second conversion device 5B outputs to the DC bus 2. More specifically, the second current detector 9B detects the second output current flowing through the fourth electric wire L4 between the second conversion device 5B and the DC bus 2. Further, the second current detector 9B outputs a second current signal indicating the second output current to the second droop control section 10B. As the second current detector 9B, for example, a CT (Current Transformer), a current probe, or the like is used. Note that the second current detector 9B may be incorporated in the PLC, the second conversion device 5B, the second BMU 3B, etc.

The control circuit 7 determines a first droop control value for the first droop control section 10A and a second droop control value for the second droop control section 10B based on the first physical quantity and the second physical quantity. More specifically, the control circuit 7 outputs a signal indicating the first physical quantity (for example, a first signal indicating the first battery voltage and/or a third signal indicating the first estimated charge amount), and a second signal indicating the first physical quantity. A signal indicating a physical quantity (for example, a second signal indicating a second battery voltage and/or a fourth signal indicating a second estimated charge amount) is received, and a second signal indicating a second physical quantity is received based on the first physical quantity and the second physical quantity. A first droop control value for the first droop control section 10A and a second droop control value for the second droop control section 10B are determined.

The control circuit 7 also outputs a first droop control command corresponding to the determined first droop control value to the first droop control unit 10A, and outputs a second droop control command corresponding to the determined second droop control value. is output to the second droop control section 10B.

The first droop control unit 10A adjusts the first voltage droop characteristic of the first conversion device 5A. More specifically, the first droop control unit 10A adjusts the first voltage droop characteristic of the first conversion device 5A based on the first droop control value received from the control circuit 7.

Further, the first droop control unit 10A receives a first current signal indicating the first output current from the first current detector 9A, and outputs a first voltage droop characteristic adjusted based on the first droop control value and a first A first output voltage command value for the first conversion device 5A is determined based on the output current. Furthermore, the first droop control unit 10A outputs a first control command corresponding to the determined first output voltage command value to the first conversion device 5A.

The second droop control unit 10B adjusts the second voltage droop characteristic of the second conversion device 5B. More specifically, the second droop control unit 10B adjusts the second voltage droop characteristic of the second conversion device 5B based on the second droop control value received from the control circuit 7.

Further, the second droop control unit 10B receives a second current signal indicating the second output current from the second current detector 9B, and outputs the second voltage droop characteristic adjusted based on the second droop control value and the second A second output voltage command value for the second conversion device 5B is determined based on the output current. Further, the second droop control section 10B outputs a second control command corresponding to the determined second output voltage command value to the second conversion device 5B.

Note that part or all of the first droop control section 10A may be incorporated in the first conversion device 5A or the control circuit 7. Further, a part or the whole of the second droop control section 10B may be incorporated into the second conversion device 5B or the control circuit 7.

(Action: Power supply to DC bus 2)
In the example shown in FIG. 10, the control circuit 7 controls the first droop control unit 10A so that the power burden ratio of the first battery 40A and the second battery 40B, which has a smaller remaining battery level, is reduced. 1 droop control value and a second droop control value for the second droop control unit 10B are determined. The control circuit 7 also outputs a first droop control command corresponding to the determined first droop control value to the first droop control unit 10A, and outputs a second droop control command corresponding to the determined second droop control value. is output to the second droop control section 10B.

The first droop control unit 10A outputs a first output to the first converter 5A based on the first voltage droop characteristic adjusted based on the first droop control value and the first output current of the first converter 5A. Determine the voltage command value. Further, the first droop control unit 10A outputs a first control command corresponding to the determined first output voltage command value to the first conversion device 5A.

The second droop control unit 10B outputs a second output to the second converter 5B based on the second voltage droop characteristic adjusted based on the second droop control value and the second output current of the second converter 5B. Determine the voltage command value. Further, the second droop control unit 10B outputs a second control command corresponding to the determined second output voltage command value to the second conversion device 5B.

As a result, the first output voltage of the first converter 5A and/or the second output voltage of the second converter 5B change, and the power burden ratio of the battery with the smaller remaining battery level is reduced. In this way, it is possible to prevent large variations in the timing at which the remaining battery power reaches zero for each battery.

An example of adjusting voltage droop characteristics will be described with reference to FIGS. 11 and 12.

FIG. 11 shows that the control circuit 7 outputs a first droop control command and a second droop control command for reducing the power burden ratio of the first battery 40A and the second battery 40B, which has a smaller remaining battery level. An example of the relationship between the first output current of the first conversion device 5A and the first output voltage of the first conversion device 5A, and the relationship between the second output current of the second conversion device 5B and the second It is a graph which shows an example of the relationship between the 2nd output voltage of the converter 5B.

For simplification, it is assumed that at time t1, the voltage droop characteristic of the first converter 5A and the voltage droop characteristic of the second converter 5B are equal. Further, at time t1, the value of the first output voltage of the first conversion device 5A is equal to the value of the second output voltage of the second conversion device 5B, and the value of the first output voltage and the value of the second output voltage are as follows. Each has a voltage value F2. Moreover, at time t1, the value of the first output current of the first converter 5A is equal to the value of the second output current of the second converter 5B, and the value of the first output current and the value of the second output current are as follows. Each has a current value I1.

In the example shown in FIG. 11, the output power of the first conversion device 5A and the output power of the second conversion device 5B are both F2×I1. In the example shown in FIG. 11, it is assumed that the remaining battery capacity of the first battery 40A is smaller than the remaining battery capacity of the second battery 40B. In this case, as described in the first embodiment, if the output power of each converter is equal, the remaining battery level of the first battery 40A becomes zero first, and the first converter 5A stops. Such a stoppage of the first converter 5A leads to generation of overpower in the second converter 5B or a reduction in redundancy of the converter.

Therefore, according to the third embodiment, the control circuit 7 controls the first droop control unit so that the power burden ratio of the first battery 40A and the second battery 40B, which has a smaller remaining battery level, is reduced. A first droop control value for the droop control section 10A and a second droop control value for the second droop control section 10B are determined. Further, at least one of the first droop control unit 10A that receives the first droop control value and the second droop control unit 10B that receives the second droop control value changes the voltage droop characteristic of the corresponding conversion device ( In other words, it corrects the voltage droop characteristics of the corresponding converter).

This will be explained more specifically. In the example shown in FIG. 12, assume that the first battery remaining amount of the first battery 40A is smaller than the second battery remaining amount of the second battery 40B. In this case, the first droop control unit 10A that receives the first droop control command corresponding to the first droop control value controls the first droop control unit 10A so that the first voltage droop characteristic of the first conversion device 5A is strengthened (in other words, the first the first output voltage of the first converter 5A (so that the ratio of decrease (or increase) in the first output voltage of the first converter 5A to the increase (or decrease) in the first output current of the first converter 5A is large). 1 Correct the voltage droop characteristic (see arrow AR10).

In the example shown in FIG. 12, by strengthening the first voltage droop characteristic of the first converter 5A, the power burden ratio of the first battery 40A is reduced and the power burden ratio of the second battery 40B is increased. . More specifically, in the example shown in FIG. 12, the first voltage droop characteristic of the first converter 5A is strengthened, so that (1) the value of the first output voltage of the first converter 5A and the second The values of the second output voltage of the converter 5B are both changed from the voltage value F2 to the voltage value F3, and (2) the value of the first output current of the first converter 5A is changed from the current value I1 to the current value I2. (3) The value of the second output current of the second conversion device 5B is increased from the current value I1 to the current value I3. As a result, the output power of the first converter 5A changes to F3×I2, and the output power of the second converter 5B changes to F3×I3. Since current value I2<current value I3, the first converter The output power of the device 5A (F3×I2)<the output power of the second conversion device 5B (F3×I3). Note that the sum of the output power of the first conversion device 5A and the output power of the second conversion device 5B, “F3×(I2+I3)”, is the output of both before the first voltage droop characteristic of the first conversion device 5A is strengthened. It is equal to the total power "2 x F2 x I1".

As described above, in the example shown in FIG. 12, by strengthening the first voltage droop characteristic of the first converter 5A, the power burden ratio of the first battery 40A is reduced, and the power burden ratio of the second battery 40B is reduced. is increased. Alternatively or additionally, by weakening the second voltage droop characteristic of the second converter 5B, the power burden ratio of the first battery 40A is reduced and the power burden ratio of the second battery 40B is increased. It's okay.

Note that in the third embodiment, the voltage droop characteristic of the first battery 40A and the second battery 40B, which has a smaller remaining battery capacity, may be strengthened continuously or in stages. . Alternatively or additionally, in the third embodiment, the voltage droop characteristic of the first battery 40A and the second battery 40B, which has a larger remaining battery capacity, may be continuously weakened, It may be weakened in stages.

(Action: Power reception from DC bus 2)
In the example shown in FIG. 13, the control circuit 7 controls the first droop control unit 10A so that the power reception ratio of the first battery 40A and the second battery 40B, which has a higher battery level, is reduced. 1 droop control value and a second droop control value for the second droop control unit 10B are determined. The control circuit 7 also outputs a first droop control command corresponding to the determined first droop control value to the first droop control unit 10A, and outputs a second droop control command corresponding to the determined second droop control value. is output to the second droop control section 10B.

The first droop control unit 10A outputs a first output to the first converter 5A based on the first voltage droop characteristic adjusted based on the first droop control value and the first output current of the first converter 5A. Determine the voltage command value. Further, the first droop control unit 10A outputs a first control command corresponding to the determined first output voltage command value to the first conversion device 5A.

The second droop control unit 10B outputs a second output to the second converter 5B based on the second voltage droop characteristic adjusted based on the second droop control value and the second output current of the second converter 5B. Determine the voltage command value. Further, the second droop control unit 10B outputs a second control command corresponding to the determined second output voltage command value to the second conversion device 5B.

As a result, the first output voltage of the first converter 5A and/or the second output voltage of the second converter 5B change, and the proportion of power received by the battery with a higher remaining battery level is reduced. The proportion of power received by the battery with the smaller amount is increased. As a result, the timing at which each battery becomes fully charged can be prevented from varying greatly.

(effect)
In the DC power supply system 100C according to the third embodiment, when the energy capacity or characteristics of each power source are different, the voltage droop characteristic of at least one converter is changed according to the remaining energy amount of each power source. By doing so, the power burden ratio of each power source is adjusted. In this way, the remaining energy of one power source is prevented or suppressed from becoming zero before the remaining energy of another power source. As a result, operation of the plurality of converters is maintained, overpowering of a particular converter is prevented, and redundancy of the converters is maintained. Thus, in the third embodiment, a stable DC power supply system is provided.

Further, in the DC power supply system 100C in the third embodiment, the voltage droop characteristic of at least one converter is changed according to the remaining energy of each power source, and the voltage droop characteristic of the converter is changed based on the voltage droop characteristic. The output voltage is changed depending on the output current. Therefore, even before changing the voltage droop characteristic of at least one converter according to the remaining energy of each power source, and after changing the voltage droop characteristic of at least one converting device according to the remaining energy of each power source, Cross currents are suppressed from occurring between the plurality of converters.

Further, in the third embodiment, when power is supplied from the charging power source 1B to a plurality of power sources (4A, 4B) via the DC bus 2, the remaining energy of each power source (in other words, each power source By changing the voltage droop characteristic of at least one converter according to the energy storage amount), the power reception ratio of each power source is adjusted. In this way, the energy storage amount of one power source is prevented or suppressed from becoming full before the energy storage amount of another power source. As a result, operation of the plurality of converters is maintained, overpowering of a particular converter is prevented, and redundancy of the converters is maintained. Thus, in the third embodiment, a stable DC power supply system is provided.

It is clear that the present invention is not limited to the above-described embodiments or modified examples, and that each embodiment or modified example can be modified or changed as appropriate within the scope of the technical idea of the present invention. Further, various techniques used in each embodiment or each modification can be applied to other embodiments or other modifications as long as no technical contradiction occurs. Furthermore, any additional configurations in each embodiment or each modification can be omitted as appropriate.

1A...load, 1B...power supply for charging, 2...DC bus, 3A...first BMU, 3B...second BMU, 4A...first power supply, 4B...second power supply, 5A...first conversion device, 5B... Second conversion device, 6A...first output section, 6B...second output section, 7...control circuit, 9A...first current detector, 9B...second current detector, 10A...first droop control section, 10B... Second droop control unit, 40A...first battery, 40B...second battery, 60A...first voltage detector, 60B...second voltage detector, 62A...first estimated charge amount calculation unit, 62B...second Estimated charge amount calculation unit, 91... Load, 92... DC bus, 93A... First battery management unit, 93B... Second battery management unit, 94A... First battery group, 94B... Second battery group, 95A ...first conversion device, 95B...second conversion device, 96A...first current detector, 96B...second current detector, 97A...first droop control section, 97B...second droop control section , 100, 100A, 100B, 100C...DC power supply system, L1...first electric wire, L2...second electric wire, L3...third electric wire, L4...fourth electric wire

Claims (7)

A DC bus to which one or both of a load and a charging power source are connected;
a first power source that stores first energy and outputs DC power from the first energy;
a second power source that stores second energy and outputs DC power from the second energy;
a first conversion device that is disposed between the first power source and the DC bus, and increases or decreases the first power supply voltage on the first power source side to a first output voltage on the DC bus side;
a second conversion device that is disposed between the second power source and the DC bus, and increases or decreases the second power supply voltage on the second power source side to a second output voltage on the DC bus side;
a first output unit that detects or calculates a first physical quantity that changes depending on the remaining amount of the first energy stored in the first power source and outputs a signal indicating the first physical quantity;
a second output unit that detects or calculates a second physical quantity that changes depending on the remaining amount of the second energy stored in the second power source and outputs a signal indicating the second physical quantity;
A first output voltage command value for the first conversion device and a second output voltage command value for the second conversion device are determined based on the first physical quantity and the second physical quantity, and the determined first a control circuit that outputs an output voltage command value to the first conversion device and outputs the determined second output voltage command value to the second conversion device,
The first conversion device increases or decreases the first power supply voltage to the first output voltage based on the first output voltage command value and a first voltage droop characteristic,
The second converter is configured to increase or decrease the second power supply voltage to the second output voltage based on the second output voltage command value and the second voltage droop characteristic. The control circuit sets the first output voltage command value to the first conversion device so that the power burden ratio of the first power source and the second power source with less remaining energy is reduced; The DC power supply system according to claim 1, wherein the second output voltage command value for the second conversion device is determined. The first power source is a rechargeable first battery,
The second power source is a rechargeable second battery,
The first output unit includes a first voltage detector that detects a first battery voltage that changes depending on a first battery remaining amount of the first battery,
The second output section includes a second voltage detector that detects a second battery voltage that changes according to a second battery remaining amount of the second battery,
The control circuit calculates the remaining amount of the first battery based on the first battery voltage and the discharge characteristics of the first battery, and calculates the remaining amount of the first battery based on the second battery voltage and the discharge characteristics of the second battery. Calculate the remaining battery level of the second battery,
The control circuit is configured such that when the first battery remaining amount is less than the second battery remaining amount, the power burden ratio of the first battery is reduced and the power burden ratio of the second battery is increased. The DC power supply system according to claim 1, wherein the first output voltage command value for the first conversion device and the second output voltage command value for the second conversion device are determined. The first power source is a rechargeable first battery,
The second power source is a rechargeable second battery,
The first output unit includes a first estimated charge amount calculation unit that calculates a first estimated charge amount of the first battery,
The second output unit includes a second estimated charge amount calculation unit that calculates a second estimated charge amount of the second battery,
The control circuit is configured such that when the first estimated charge amount is less than the second estimated charge amount, the power burden percentage of the first battery is reduced and the power burden percentage of the second battery is increased. , determining the first output voltage command value for the first conversion device and the second output voltage command value for the second conversion device. The control circuit sets the first output voltage command value to the first converter so that the power reception ratio of the first power source and the second power source with a higher amount of remaining energy is reduced; and The DC power supply system according to claim 1, wherein the second output voltage command value for the second conversion device is determined. A DC bus to which one or both of a load and a charging power source are connected;
a first power source that stores first energy and outputs DC power from the first energy;
a second power source that stores second energy and outputs DC power from the second energy;
a first conversion device that is disposed between the first power source and the DC bus, and increases or decreases the first power supply voltage on the first power source side to a first output voltage on the DC bus side;
a second conversion device that is disposed between the second power source and the DC bus, and increases or decreases the second power supply voltage on the second power source side to a second output voltage on the DC bus side;
a first output unit that detects or calculates a first physical quantity that changes depending on the remaining amount of the first energy stored in the first power source and outputs a signal indicating the first physical quantity;
a second output unit that detects or calculates a second physical quantity that changes depending on the remaining amount of the second energy stored in the second power source and outputs a signal indicating the second physical quantity;
a first current detector that detects a first output current of the first conversion device and outputs a first current signal indicating the first output current to a first droop control unit;
a second current detector that detects a second output current of the second conversion device and outputs a second current signal indicating the second output current to a second droop control unit;
Based on the first physical quantity and the second physical quantity, a first droop control value for the first droop control section and a second droop control value for the second droop control section are determined, and the determined first droop control value is determined. a control circuit that outputs a droop control value to the first droop control unit and outputs the determined second droop control value to the second droop control unit;
the first droop control unit that adjusts a first voltage droop characteristic of the first conversion device based on the first droop control value received from the control circuit;
the second droop control unit that adjusts the second voltage droop characteristic of the second conversion device based on the second droop control value received from the control circuit;
The first droop control unit determines a first output voltage command value for the first conversion device based on the adjusted first voltage droop characteristic and the first output current, and 1 output voltage command value to the first conversion device,
The second droop control unit determines a second output voltage command value for the second conversion device based on the adjusted second voltage droop characteristic and the second output current, and A DC power supply system that outputs two output voltage command values to the second conversion device. The control circuit controls the first droop control value for the first droop control unit so that the power burden ratio of the first power source and the second power source with a smaller remaining energy level is reduced; and The DC power supply system according to claim 6, wherein the second droop control value for the second droop control unit is determined.

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