DC power supply system and DC power control method

Abstract

To provide a DC power supply system and a DC power control method capable of appropriately setting a characteristic value in droop characteristics when controlling at least one of an input and an output of a plurality of power supply units by the droop characteristics.SOLUTION: A DC power supply system 100 includes: power storage units 21 and 22; power conversion units 31 and 32; and a control unit 60 that controls DC power output by each of the power conversion units 31 and 32 based on droop characteristics representing a relation between an output and a voltage of the DC power using a predetermined characteristic value. The control unit 60 is configured to adjust a characteristic value of the droop characteristics in at least one of the power conversion units 31 and 32 based on a voltage measurement value on a DC bus 10 side such that the voltage measurement value is included in a predetermined range.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a DC power supply system and a DC power control method. [Background technology]

[0002] BACKGROUND ART DC power supply systems are known in the art (see, for example, Patent Document 1 and Non-Patent Document 1).

[0003] The above-mentioned Patent Document 1 describes a DC power supply system having two batteries connected to a DC bus. A converter that boosts or lowers voltage is connected between each of the two batteries and the DC bus. The converter boosts or lowers the voltage based on a droop characteristic that reduces the output voltage in response to an increase in output current. The DC power supply system described in the above-mentioned Patent Document 1 also performs control to change the droop characteristic so as to reduce the power burden of the battery with the smaller remaining battery charge.

[0004] Furthermore, Non-Patent Document 1 above describes a battery storage system that controls input / output to and from two batteries connected to a DC bus by droop control. In this battery storage system, in order to balance the SOC (State Of Charge) between the two batteries, a droop coefficient for setting the output voltage in droop control is set based on the difference between the SOC value of each of the two batteries and the average value of the two SOCs. In the battery storage system of Non-Patent Document 1 above, the droop coefficient of the droop characteristics is set based on the SOC, so that the battery with a higher SOC supplies more power and the battery with a lower SOC supplies less power, thereby balancing the SOCs between the batteries. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 7233825 [Non-patent literature]

[0006] [Non-Patent Document 1] Jianmin Wang, "SoC-Based Dynamic Droop Control for Battery Energy Storage Systems in DC Microgrids Feeding CPLs", Journal of Physics: Conference Series, 2021, vol.1754 Summary of the Invention [Problem to be solved by the invention]

[0007] Here, when a characteristic value such as a droop coefficient in the droop characteristic is changed as in the DC power supply system described in Patent Document 1 and the battery storage system described in Non-Patent Document 1, the voltage on the DC bus may deviate from a predetermined range due to a large degree of change in the characteristic value. Therefore, when at least one of the input and output of a plurality of batteries (power sources) is controlled by the droop characteristic, it is desired to appropriately set the characteristic value in the droop characteristic.

[0008] The present invention has been made to solve the above-mentioned problems, and one object of the present invention is to provide a DC power supply system and a DC power control method that are capable of appropriately setting a characteristic value in the droop characteristic when at least one of the input and output of a plurality of power supply units is controlled using the droop characteristic. [Means for solving the problem]

[0009] In order to achieve the above object, a DC power supply system according to a first aspect of the present invention includes a plurality of power supply units that at least one of supplying power to a common DC bus to which DC power is applied and receiving power from the common DC bus; a plurality of power conversion units provided for each of the plurality of power supply units, converting input power between each of the plurality of power supply units and the DC bus and outputting the converted power; and a control unit that controls the power output by each of the plurality of power conversion units based on a droop characteristic that represents the relationship between the output of DC power and voltage using a predetermined characteristic value, and the control unit is configured to adjust the characteristic value of the droop characteristic of at least one of the plurality of power conversion units based on a voltage measurement value on the DC bus side so that the voltage measurement value falls within a predetermined range.

[0010] In the DC power supply system according to the first aspect of the present invention, as described above, the control unit is configured to adjust the characteristic value of the droop characteristic of at least one of the plurality of power conversion units, based on a voltage measurement value on the DC bus side, so that the measured voltage falls within a predetermined range. This adjusts the characteristic value of the droop characteristic based on the voltage measurement value on the DC bus side so that the measured voltage falls within the predetermined range, thereby preventing the voltage on the DC bus from deviating from the predetermined range. Therefore, the characteristic value of the droop characteristic can be changed to an appropriate value while maintaining the voltage on the DC bus within the predetermined range. As a result, when at least one of the input and output of the plurality of power supply units is controlled using the droop characteristic, the characteristic value of the droop characteristic can be set appropriately.

[0011] In the DC power supply system according to the first aspect, the control unit is preferably configured to adjust a characteristic value of a droop characteristic of at least one of the plurality of power conversion units based on a charged energy amount indicating an energy charging state of each of the plurality of power supply units and a voltage measurement value. With this configuration, the characteristic value of the droop characteristic is adjusted based on the charged energy amount and the voltage measurement value, so that the characteristic value of the droop characteristic can be adjusted to balance the charged energy amounts and the voltage of the DC bus can be prevented from deviating from a predetermined range. Therefore, the characteristic value of the droop characteristic can be adjusted to quickly complete balancing of the charged energy amounts of the plurality of power supply units while preventing the voltage of the DC bus from deviating from the predetermined range. As a result, the charged energy amounts of the plurality of power supply units can be more quickly balanced while preventing the operation of the DC power supply system from becoming unstable due to the voltage of the DC bus deviating from the predetermined range.

[0012] In this case, the characteristic value preferably includes a characteristic coefficient representing the relationship between the DC power output and the voltage in the droop characteristic, and the control unit is configured to acquire a coefficient adjustment amount for adjusting the characteristic coefficient based on the energy charging amount, and acquire an adjustment index for adjusting the coefficient adjustment amount based on the voltage measurement value so that the voltage measurement value falls within a predetermined range, and adjust the characteristic coefficient of the droop characteristic in at least one of the multiple power conversion units based on the acquired coefficient adjustment amount and adjustment index. With this configuration, the characteristic coefficient can be adjusted using the coefficient adjustment amount acquired based on the energy charging amount, and the coefficient adjustment amount can be adjusted using the adjustment index acquired based on the voltage measurement value. Therefore, while the characteristic coefficient of the droop characteristic can be adjusted using the coefficient adjustment amount to balance the energy charging amounts, the coefficient adjustment amount can be adjusted using the adjustment index so that the voltage on the DC bus side falls within a predetermined range. Therefore, by acquiring the coefficient adjustment amount and the adjustment index, it is possible to easily and quickly achieve balancing of the energy charging amounts in the multiple power supply units while easily preventing the DC power supply system from becoming unstable in operation.

[0013] In the DC power supply system that adjusts the characteristic coefficient based on the coefficient adjustment amount and the adjustment index, the control unit preferably acquires the coefficient adjustment amount based on the difference between an average energy charging amount, which is the average of the energy charging amounts of the multiple power supply units, and the energy charging amount of one of the multiple power supply units, and acquires the adjustment index based on the ratio of the measured voltage to a preset voltage range that is set so that the measured voltage falls within a predetermined range. With this configuration, the coefficient adjustment amount is acquired based on the difference between the average energy charging amount and the energy charging amount of the one power supply unit, so the characteristic coefficient can be adjusted so that the measured energy charging amount of the one power supply unit approaches the average value of the multiple power supply units. Furthermore, the adjustment index is acquired based on the ratio of the measured voltage to the preset voltage range, so the degree of adjustment of the coefficient adjustment amount can be changed depending on the ratio of the measured voltage to the set voltage range. This allows the coefficient adjustment amount to be more appropriately adjusted depending on the magnitude of the measured voltage. As a result, the characteristic coefficient can be more appropriately adjusted so that the energy charging amount of each of the multiple power supply units approaches the average value of the multiple power supply units.

[0014] In this case, preferably, the control unit calculates the characteristic coefficient m by the following equation (5), where m0 is a preset reference value of the characteristic coefficient, C is a coefficient adjustment amount, and n is an adjustment index. i Calculate.

number

number

[0015] The characteristic coefficient m i In the DC power supply system that calculates the above, preferably, the control unit calculates the adjustment index n by the following equation (7), where a preset reference index is n0 and an adjustment term k is a value between 0 and 1 that is obtained based on the ratio of the measured voltage value to the set voltage range.

number

[0016] In this case, preferably, the control unit calculates the adjustment term k using the following equation (8), where m is a real number greater than 1 and x is a value indicating the ratio of the measured voltage value to the set voltage range.

number

[0017] In the DC power supply system that adjusts the characteristic value based on the energy charge amount and the voltage measurement value, the control unit is preferably configured to adjust the characteristic value of the droop characteristic for each of the multiple power conversion units based on the energy charge amount and the voltage measurement value using a common arithmetic expression. This configuration allows the characteristic value to be appropriately set for each of the multiple power conversion units, thereby more reliably preventing the voltage on the DC bus from deviating from a predetermined range than when the characteristic values ​​are adjusted for only some of the multiple power conversion units. Therefore, the characteristic value of the droop characteristic can be set to a more appropriate value. Furthermore, adjusting the characteristic value for each of the multiple power conversion units using a common arithmetic expression prevents the control process for adjusting the characteristic value from becoming complicated.

[0018] In the DC power supply system according to the first aspect, preferably, the plurality of power supply units include a plurality of power storage units that charge and discharge DC power, and the control unit, when controlling the power conversion unit to convert the DC power output from the plurality of power storage units, adjusts the characteristic value based on the voltage measurement value and a predetermined lower limit voltage value so that a voltage measurement value falls within a predetermined range, and when controlling the power conversion unit to convert the DC power input to the plurality of power storage units, adjusts the characteristic value based on the voltage measurement value and a predetermined upper limit voltage value so that the voltage measurement value falls within the predetermined range. With this configuration, it is possible to prevent the voltage on the DC bus from falling below the predetermined range when the power storage units are discharging, and to prevent the voltage on the DC bus from rising above the predetermined range when the power storage units are charging. Therefore, when the DC power from the power storage units is output to an external load via the DC bus, it is possible to effectively prevent a drop in the voltage of the DC power supplied to the load and thereby cause instability in operation, and it is possible to effectively prevent an abnormality in charging operation due to overvoltage when the power storage units are being charged.

[0019] In the DC power supply system according to the first aspect, preferably, when controlling the power converter to convert DC power output from the plurality of power supply units, the control unit adjusts the characteristic value based on the minimum value of voltage measurements on the DC bus side of each of the plurality of power conversion units, and when controlling the power converter to convert DC power input to the plurality of power supply units, the control unit adjusts the characteristic value based on the maximum value of voltage measurements on the DC bus side of each of the plurality of power conversion units. With this configuration, even when there is a difference in the voltage measurements due to line resistance or the like when outputting from the plurality of power supply units, adjusting the characteristic value based on the minimum value of voltage measurements on the DC bus side can more reliably prevent the voltage on the DC bus side from falling below a predetermined range. Furthermore, when inputting to the plurality of power supply units, adjusting the characteristic value based on the maximum value of voltage measurements on the DC bus side can more reliably prevent the voltage on the DC bus side from rising above a predetermined range. As a result, the characteristic value can be more appropriately set when outputting from the power supply units and when inputting to the power supply units.

[0020] A DC power control method according to a second aspect of the present invention includes the steps of: acquiring voltage measurements on the DC bus sides of a plurality of power conversion units provided for each of a plurality of power supply units that at least one of supplying DC power to a common DC bus to which DC power is applied and receiving DC power from the common DC bus, the power conversion units converting input power between each of the plurality of power supply units and the DC bus and outputting the converted power; and controlling the power output by each of the plurality of power conversion units based on a droop characteristic that represents the relationship between the output of DC power and voltage, using a predetermined characteristic value, wherein the step of controlling the power output by each of the plurality of power conversion units includes a step of adjusting, based on the voltage measurement on the DC bus side, the characteristic value of the droop characteristic of at least one of the plurality of power conversion units so that the voltage measurement falls within a predetermined range.

[0021] As described above, the DC power control method according to a second aspect of the present invention adjusts the characteristic value of the droop characteristic of at least one of the plurality of power conversion units based on a voltage measurement value on the DC bus side so that the measured voltage falls within a predetermined range. This adjusts the characteristic value of the droop characteristic based on the voltage measurement value on the DC bus side so that the measured voltage falls within the predetermined range, thereby preventing the voltage on the DC bus from deviating from the predetermined range. Therefore, the characteristic value of the droop characteristic can be changed to an appropriate value while maintaining the voltage on the DC bus within the predetermined range. As a result, a DC power control method can be provided that can appropriately set the characteristic value of the droop characteristic when controlling at least one of the input and output of the plurality of power supply units using the droop characteristic. [Effects of the Invention]

[0022] According to the present invention, as described above, when at least one of the input and output of a plurality of power supply units is controlled using the droop characteristic, the characteristic value of the droop characteristic can be appropriately set. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is a block diagram showing an overall configuration of a DC power supply system according to an embodiment. [Figure 2] FIG. 10 is a diagram for explaining droop control. [Figure 3] FIG. 10 is a diagram for explaining adjustment of a characteristic coefficient of a droop characteristic in droop control. [Figure 4] FIG. 10 is a diagram for explaining acquisition of an adjustment index. [Figure 5] FIG. 10 is a diagram showing the relationship between a voltage measurement value and an adjustment term. [Figure 6] FIG. 3 is a flowchart illustrating a DC power control method performed by the DC power supply system of the present embodiment. [Figure 7] 10A and 10B are diagrams showing an example of time-dependent changes in voltage measurement values, adjustment indexes, and SOC. [Figure 8]FIG. 10 is a diagram for explaining droop characteristics during charging. [Figure 9] FIG. 10 is a diagram for explaining acquisition of an adjustment index during charging. [Figure 10] FIG. 10 is a diagram for explaining acquisition of an adjustment term according to a first modified example of the present embodiment. [Figure 11] FIG. 10 is a diagram for explaining acquisition of an adjustment term according to a second modified example of the present embodiment. [Figure 12] FIG. 10 is a diagram for explaining control according to a third modified example of the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0024] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described with reference to the accompanying drawings.

[0025] The configuration of a DC power supply system 100 according to one embodiment of the present invention will be described with reference to FIGS.

[0026] (Configuration of DC power supply system) 1 , the DC power supply system 100 includes a DC bus 10, power storage units 21 and 22, power conversion units 31 and 32, current measurement units 41 and 42, voltage measurement units 51 and 52, and a control unit 60. The DC power supply system 100 supplies DC power from the power storage units 21 and 22 to a load 101 via the DC bus 10, and charges the power storage units 21 and 22 by inputting DC power from a power supply device 102 to the power storage units 21 and 22 via the DC bus 10. The power storage units 21 and 22 are examples of a "power supply unit" in the claims.

[0027] The DC bus 10 is a DC bus provided in common to the power storage unit 21 and the power conversion unit 31, and the power storage unit 22 and the power conversion unit 32. The power storage units 21 and 22 are electrically connected in parallel to the DC bus 10. DC power is applied to the DC bus 10. That is, the DC bus 10 includes a DC conductor through which the DC power output from the power storage units 21 and 22 and the DC power input to the power storage units 21 and 22 flow. The DC bus 10 is also electrically connected to an external load 101 and an external power supply device 102.

[0028] The power storage units 21 and 22 at least either supply (output) DC power to the common DC bus 10 or receive (input) DC power from the common DC bus 10. In the present embodiment, the power storage units 21 and 22 charge and discharge DC power. The power storage units 21 and 22 include, for example, lithium-ion batteries. Each of the power storage units 21 and 22 has a plurality of battery cells. The power storage units 21 and 22 also have a common configuration. For example, the power storage units 21 and 22 have the same rated output and rated capacity. During discharge, in which DC power is output from the power storage units 21 and 22, the DC power output from the power storage unit 21 is output to the DC bus 10 via the power conversion unit 31, and the DC power output from the power storage unit 22 is output to the DC bus 10 via the power conversion unit 32. Furthermore, during charging when DC power is input to the power storage units 21 and 22, DC power from the DC bus 10 is input to the power storage unit 21 via the power conversion unit 31, and DC power from the DC bus 10 is input to the power storage unit 22 via the power conversion unit 32.

[0029] Furthermore, the power storage unit 21 and the power storage unit 22 have a BMS 21a and a BMS 22a, respectively. The BMSs (Battery Management Systems) 21a and 22a control the operation of the power storage units 21 and 22, respectively. The BMSs 21a and 22a also transmit and receive signals to and from the control unit 60. The BMSs 21a and 22a acquire operating conditions of the power storage units 21 and 22, such as the temperature, output voltage, and number of charge / discharge cycles. The BMSs 21a and 22a also acquire energy charge amounts indicating the energy charge states of the power storage units 21 and 22, respectively, and output signals indicating the acquired energy charge amounts to the control unit 60. In this embodiment, the BMSs 21a and 22a acquire SOCs (State Of Charge) as the energy charge amounts of the power storage units 21 and 22. BMSs 21a and 22a measure the SOC as the amount of charged energy in power storage units 21 and 22, for example, by a voltage method that measures the SOC based on the voltage of power storage units 21 and 22, or a current integration method (coulomb counting) that performs time integration of the current output from power storage units 21 and 22. The SOC is expressed as a percentage (%), with a fully charged state being 100. BMSs 21a and 22a each have, for example, a calculation device such as a CPU (Central Processing Unit) and a storage device such as a memory.

[0030] The power conversion unit 31 and the power conversion unit 32 are provided for each of the power storage units 21 and 22, and convert input DC power between each of the power storage units 21 and 22 and the DC bus 10, and output the converted DC power. When the power storage unit 21 is discharging, the power conversion unit 31 converts the DC power from the power storage unit 21 and outputs it to the DC bus 10, and when the power storage unit 21 is charging, the power conversion unit 31 converts the DC power from the DC bus 10 and outputs it to the power storage unit 21. When the power storage unit 22 is discharging, the power conversion unit 32 converts the DC power from the power storage unit 22 and outputs it to the DC bus 10, and when the power storage unit 22 is charging, the power conversion unit 32 converts the DC power from the DC bus 10 and outputs it to the power storage unit 22. That is, the power conversion unit 31 and the power conversion unit 32 include bidirectional DC-DC converters. The power conversion units 31 and 32 convert the voltage of the input DC power so as to increase or decrease the voltage. Specifically, the power conversion units 31 and 32 have switching elements that perform switching operations based on control signals from the control unit 60. The power conversion units 31 and 32 include, for example, chopper circuits having switching elements as bidirectional DC-DC converters. The power conversion units 31 and 32 have, for example, MOS-FETs (Metal-Oxide-Semiconductor Field-Effect Transistors) or IGBTs (Insulated Gate Bipolar Transistors) as switching elements.

[0031] The power conversion units 31 and 32 each have a controller 31a and a controller 32a. The controllers 31a and 32a control the operation of the power conversion units 31 and 32, respectively. The controllers 31a and 32a convert a voltage command V ref The controllers 31a and 32a control the switching operations of the power conversion units 31 and 32, respectively, based on a voltage command V ref The controllers 31a and 32a each include a gate driver circuit that generates a gate signal to be input to the gate terminal of the switching element based on the signal. The controllers 31a and 32a each include a calculation device such as a CPU and a storage device such as a memory.

[0032] The current measuring units 41 and 42 are connected to the DC bus 10 sides of the power conversion units 31 and 32, respectively. Specifically, the current measuring units 41 and 42 are connected to electric paths branching from the DC bus 10 toward the power conversion units 31 and 32, respectively. The current measuring unit 41 is connected to the DC bus 10 side of the power conversion unit 31, and measures the current of the DC power output from the power conversion unit 31 to the DC bus 10 and the current of the DC power input from the DC bus 10 to the power conversion unit 31. The current measuring unit 42 is connected to the DC bus 10 side of the power conversion unit 32, and measures the current of the DC power output from the power conversion unit 32 to the DC bus 10 and the current of the DC power input from the DC bus 10 to the power conversion unit 32. Each of the current measuring units 41 and 42 transmits a signal indicating the detection result of the measured current to the control unit 60.

[0033] The voltage measurement units 51 and 52 are connected to the DC bus 10 sides of the power conversion units 31 and 32, respectively. Specifically, the voltage measurement units 51 and 52 are connected to electric paths branching from the DC bus 10 toward the power conversion units 31 and 32, respectively. The voltage measurement unit 51 is connected to the DC bus 10 side of the power conversion unit 31, and measures the voltage of the DC power output from the power conversion unit 31 to the DC bus 10 and the voltage of the DC power input from the DC bus 10 to the power conversion unit 31. The voltage measurement unit 52 is connected to the DC bus 10 side of the power conversion unit 32, and measures the voltage of the DC power output from the power conversion unit 32 to the DC bus 10 and the voltage of the DC power input from the DC bus 10 to the power conversion unit 32. Each of the voltage measurement units 51 and 52 transmits a signal indicating the detection result of the measured voltage to the control unit 60.

[0034] The control unit 60 controls the DC power output by each of the power storage units 21 and 22. The control unit 60 includes, for example, a calculation device such as a CPU and a storage device such as a memory. The control unit 60 may be configured by a combination of multiple processors and circuits. The control unit 60 transmits and receives signals to and from the BMSs 21a and 22a of the power storage units 21 and 22 and the controllers 31a and 32a of the power conversion units 31 and 32. The control unit 60 receives signals indicating the SOC of the power storage unit 21 and a signal indicating the SOC of the power storage unit 22 from the BMSs 21a and 22a, respectively. The control unit 60 also receives signals indicating the current detection results from the current measurement units 41 and 42. The control unit 60 also receives signals indicating the voltage detection results from the voltage measurement units 51 and 52. The control unit 60 also outputs a voltage command V to the controllers 31a and 32a of the power conversion units 31 and 32 to control the voltage of the DC power output from each of the power conversion units 31 and 32. ref Output.

[0035] (Droop control) As shown in FIG. 2, in this embodiment, the control unit 60 controls the predetermined characteristic coefficient m i The DC power output from each of the power conversion units 31 and 32 is controlled based on the droop characteristic that represents the relationship between the DC power output and the voltage using a predetermined characteristic coefficient m i In this embodiment, the control unit 60 performs calculations according to a preset program using preset parameters, the SOC values ​​acquired from the BMSs 21a and 22a, and the signals acquired from the voltage measurement units 51 and 52, to obtain a characteristic coefficient m i Set the characteristic coefficient m i is a proportional constant that represents the ratio of the amount of change in voltage to the amount of change in current in droop control, which is a control that uses droop characteristics, and is also called the droop coefficient or droop gain. i is an example of a "characteristic value" in the claims.

[0036] For example, when DC power is output from the power storage units 21 and 22, the control unit 60 performs droop control to control the operation of the power conversion units 31 and 32 so that the voltage decreases in accordance with an increase in the current output to the DC bus 10. In the DC power supply system 100, the rated voltage V Rate is set in advance. The control unit 60 calculates a current measurement value I i and a predetermined characteristic coefficient m i and the set rated voltage V Rate The difference between these values ​​is used as a voltage command V ref where the measured current I i is a value acquired based on a signal indicating the current detection result acquired from each of the current measuring units 41 and 42, and is a measurement value indicating the magnitude of the current of the DC power output from each of the power conversion units 31 and 32. For example, in FIG. 2, in the droop control, the current measurement value I i The value of "i a ", the rated voltage V Rate Smaller than "V a " is the voltage command V ref The following shows an example of the value:

[0037] 3, in the DC power supply system 100 of this embodiment, the control unit 60 performs control to balance the SOC values ​​of the power storage units 21 and 22. That is, the control unit 60 balances the SOC values ​​of the power storage units 21 and 22 based on the energy charge amount E i The energy charge amount E, which indicates the obtained SOC value, is also obtained. i Based on this, the characteristic coefficient m is used to balance the SOC value. i The term "balancing" means reducing and equalizing the difference between the SOC values ​​of power storage units 21 and 22. Specifically, control unit 60 calculates the energy charge amount E i Based on the SOC value, the characteristic coefficient m iThe control unit 60 acquires a coefficient adjustment amount C for adjusting the energy charge amount E i The average energy charge E ave and the energy charge amount E in one of the power storage units 21 and 22. i Based on the difference between the coefficient adjustment amount C and the coefficient adjustment amount C, the coefficient adjustment amount C is calculated by the following equation (9).

number

[0038] Then, the control unit 60 calculates the characteristic coefficient m of the droop characteristic by the following equation (10): i Calculate.

number

[0039] In the DC power supply system 100 of this embodiment, the voltage measurement value V out (see FIG. 4 ) to control the power conversion units 31 and 32 so that the DC voltage applied to the DC bus 10 falls within a predetermined range. The control unit 60 adjusts the value of the adjustment index n to adjust the characteristic coefficient m i The predetermined range is, for example, when power is output from power storage units 21 and 22, the value of rated voltage V Rate In Figure 4, the voltage measurement value V outThe measured voltage on the DC bus 10 side of the power conversion unit 31 corresponding to the power storage unit 21 is V out1 , the measured voltage of the power conversion unit 32 corresponding to the power storage unit 22 on the DC bus 10 side is V out2 is illustrated and explained as follows.

[0040] Specifically, as shown in FIGS. 3 and 4, in this embodiment, the control unit 60 calculates the voltage measurement value V out and the SOC of the power storage units 21 and 22, the voltage measurement value V out The characteristic coefficient m of the droop characteristic in at least one of the power conversion units 31 and 32 is set so that it is within a predetermined range. i The control unit 60 is configured to adjust the voltage measurement value V on the DC bus 10 side measured by the voltage measurement units 51 and 52. out The control unit 60 obtains the adjustment index n based on the voltage measurement value V on the DC bus 10 side measured by the voltage measurement units 51 and 52. out Based on the voltage measurement V out The voltage measurement value V for the preset voltage range is set so that it is within the specified range. out In this embodiment, control unit 60 obtains an adjustment index n based on the ratio of rated voltage V Rate The voltage range may be set to a range different from the above-mentioned predetermined range. out A range smaller than the predetermined range may be set as the set voltage range so that the measured voltage V out is the rated voltage V Rate The rated voltage V is set as a preset voltage range so that it is within 90% or more and 100% or less of Rate The range is set to 92% or more and 100% or less of the rated voltage V Rate Voltage measurement value V for the range of 92% to 100% out The adjustment index n may be obtained based on the ratio of

[0041] In detail, when controlling the conversion of DC power output from the power storage units 21 and 22 by the power conversion units 31 and 32, the control unit 60 controls the rated voltage V Rate , lower limit voltage value V LL , and the voltage measurement V out By calculating the adjustment index n based on i Adjust the rated voltage V Rate is the set rated voltage V base The unit [pu] is converted from [V] to [pu]. For example, the rated voltage V base It is a number expressed as a ratio with the magnitude of V being 1. Rate is 1.0 [pu]. Lower limit voltage value V LL is the voltage measurement V out The lower limit of the voltage range is set in advance so that the voltage falls within a predetermined range, and the unit is set in [pu]. For example, the lower limit voltage value V LL The upper limit of the set voltage range during discharge is, for example, the rated voltage V Rate Similarly, the current value is expressed in units of [pu] as a ratio of the rated current applied to the DC bus 10 to 1. The characteristic coefficient m i Regarding this, when the units of voltage and current are expressed in [pu], the reference value m0 is, for example, −0.1 or −0.05.

[0042] Furthermore, when controlling the conversion of DC power output from the power storage units 21 and 22 by the power conversion units 31 and 32, the control unit 60 converts the voltage measurement value V out1 and the voltage measurement V out2 The minimum value V out_min Based on the characteristic coefficient m i That is, when power storage units 21 and 22 are discharging, control unit 60 adjusts the voltage measurement values ​​V out1 and V out2 The minimum value V out_minBy acquiring the voltage measurement value V on the DC bus 10 side, out Characteristic coefficient m based on i The control unit 60 adjusts the voltage measured value V from the voltage measuring unit 51. out1 and the voltage measurement value V from the voltage measurement unit 52 out2 and the two voltage measurements V out1 and V out2 By comparing the minimum value V out_min Then, to calculate the adjustment index n, the control unit 60 obtains this minimum value V out_min By converting the unit of [pu], the voltage measurement value V on the DC bus 10 side out Voltage measurement V out_a Get.

[0043] During discharge, the measured voltage V out_a is the lower limit voltage value V LL is the minimum value, and the rated voltage V Rate That is, the voltage measurement value V out_a is the lower limit voltage value V LL If it is lower, the lower limit voltage V LL and the rated voltage V Rate If higher, the rated voltage V Rate Therefore, the control unit 60 sets the minimum value V out_min Obtain the rated voltage V base The unit is converted to [pu] as a percentage of the lower limit voltage V LL is the lower limit, and the rated voltage V Rate By using a limiter with an upper limit of out_a Get.

[0044] Then, the control unit 60 calculates the obtained voltage measurement value V out_a and the lower limit voltage V that is preset as the set voltage range. LL and rated voltage V Rate Using the above, the set voltage range (lower limit voltage VLL Rated voltage V Rate (below) to the voltage measurement V out Calculate the value x that indicates the ratio of

number

number

[0045] Therefore, as shown in FIG. 5, the adjustment term k is a value between 0 and 1. When the value of x increases, the value of the adjustment term k also increases. In this embodiment, the value of the adjustment term k is the m-th root of x, so when the value of x approaches 0, the value decreases rapidly. In addition, the voltage measurement value V out_a is the lower limit voltage value V LL is acquired as the lower limit, the value of k cannot be a negative value, and the values ​​measured by the voltage measurement units 51 and 52 are the lower limit voltage value V LL If it is lower, the value of k will be 0.

[0046] Then, the control unit 60 calculates the adjustment index n by using the adjustment term k and the reference index n0 according to the following equation (13).

number

[0047] As shown in FIG. 3, the control unit 60 calculates the characteristic coefficient m of the droop characteristics in each of the power conversion units 31 and 32 based on the coefficient adjustment amount C and the adjustment index n obtained as described above. i When controlling the output from the power conversion unit 31, the control unit 60 adjusts the energy charge amount E which indicates the SOC of the power storage unit 21. i and the average energy charge E ave and the characteristic coefficient m i In the case where the droop control is performed by calculating the amount of charged energy E i and the average energy charge E ave and the characteristic coefficient m i In this case, the control unit 60 calculates the energy charge amount E , which indicates the acquired SOC value, for each of the power conversion units 31 and 32 using a common calculation formula. i and the voltage measurement V out and the characteristic coefficient m of the droop characteristics based on i When controlling the outputs of either of the power conversion units 31 and 32, the control unit 60 performs the calculations of the above equations (9) to (13) using parameters such as the reference value m0 and the reference exponent n0 as common set values, thereby adjusting the characteristic coefficient m of the droop characteristics of each of the power conversion units 31 and 32. i The method is configured to calculate

[0048] (DC power control method) Next, the control process of the DC power control method by the DC power supply system 100 in this embodiment will be described based on a flowchart with reference to Figures 6 and 7. The control process from step S1 to step S7 in the DC power control method shown in Figure 6 is executed by the control unit 60. The control process from step S1 to step S7 in the DC power control method is repeatedly executed at predetermined control intervals while the DC power supply system 100 is operating.

[0049] First, in step S1, the voltage measurement value V out Specifically, based on the signals from the voltage measuring units 51 and 52, the voltages on the DC bus 10 side of the power conversion units 31 and 32 are measured as voltage measurement values ​​V out1 and V out2 The control unit 60 calculates the voltage measurement value V out1 and V out2 The minimum value V out_min Convert the unit to [pu] and set the lower limit voltage V LL is the minimum value, and the rated voltage V Rate By converting it so that it has a maximum value, the characteristic coefficient m i Voltage measurement value V for calculating out_a Next, in step S2, an adjustment index n is obtained. Specifically, the voltage measurement value V obtained in step S1 is out Based on this, the calculation process is performed using equations (11) to (13) to calculate the adjustment index n.

[0050] Next, in step S3, the energy charge amount E of each of the power storage units 21 and 22 is calculated as a value indicating the SOC of the power storage units 21 and 22. i The control unit 60 acquires the energy charge amount E of each of the power storage units 21 and 22 based on the signals from the BMSs 21a and 22a. iNext, in step S4, the coefficient adjustment amount C is obtained. Specifically, the energy charging amount E obtained in step S3 is i Based on this, the calculation process according to equation (9) is performed to calculate the coefficient adjustment amount C.

[0051] Next, in step S5, the characteristic coefficient m i Specifically, the calculation process according to the formula (10) is performed using the adjustment index n obtained in step S2 and the coefficient adjustment amount C obtained in step S4, and the characteristic coefficient m i is calculated.

[0052] Next, in step S6, the current measurement value I i Specifically, a current measurement value I obtained by measuring the current on the DC bus 10 side of each of the power conversion units 31 and 32 based on the signals from each of the current measurement units 41 and 42 is obtained. i is obtained.

[0053] Next, in step S7, the voltage command V ref Specifically, the characteristic coefficient m i and the current measurement value I obtained in step S6 i and a voltage command V that controls the voltage output from each of the power conversion units 31 and 32. ref will be output.

[0054] As shown in Fig. 7, the control process from step S1 to step S7 is repeatedly performed, so that the SOC of power storage unit 21 and the SOC of power storage unit 22 become close to each other and are balanced. For example, Fig. 7 shows an example in which, at the start of control, SOC1, which is the SOC of power storage unit 21, is higher than SOC2, which is the SOC of power storage unit 22. In this way, as time passes, the difference between the SOCs of power storage units 21 and 22 becomes smaller, and the measured voltage V out The increase in increases the value of the adjustment index n.

[0055] (Droop control during charging) Next, droop control during charging of power storage units 21 and 22 will be described with reference to FIGS. 8 and 9. FIG.

[0056] As shown in FIG. 8, control unit 60 controls power storage units 21 and 22 by using a predetermined characteristic coefficient m i The control unit 60 controls the DC power output by each of the power conversion units 31 and 32 based on the droop characteristics that represent the relationship between the output of DC power and the voltage using the above formula. When DC power is input to the power storage units 21 and 22, the control unit 60 performs droop control that controls the operation of the power conversion units 31 and 32 so that the voltage increases as the input current increases. Note that in FIG. 8, the current input to the power storage units 21 and 22 is shown as a negative value. For example, in FIG. 8, in the droop control, the measured current I i The value of "i b ", the rated voltage V Rate Larger than "V b " is the voltage command V ref The following shows an example of the value:

[0057] As shown in FIG. 9, control unit 60 also calculates the voltage measurement value V out Based on the voltage reading V out In this embodiment, when controlling the power conversion units 31 and 32 to convert the DC power input to the power storage units 21 and 22, the control unit 60 calculates the adjustment index n so that the rated voltage V Rate , upper limit voltage value V UL , and the voltage measurement V out By calculating the adjustment index n based on i The set voltage range is different when charging power storage units 21 and 22 than when discharging power storage units 21 and 22. When charging power storage units 21 and 22, the upper limit of the set voltage range is adjusted to the upper limit voltage value V UL The lower limit is the rated voltage V Rate The upper limit voltage V UL is the voltage measurement V outis the upper limit value of the set voltage range that is set in advance so that it is included in a predetermined range, and the unit is [pu]. In addition, when controlling the conversion of DC power input to the power storage units 21 and 22 by the power conversion units 31 and 32, the control unit 60 converts the voltage measurement value V out1 and V out2 The maximum value of V out_max Based on this, the adjustment index n is calculated and the characteristic coefficient m i That is, during charging, the control unit 60 adjusts the voltage measurement values ​​V of the voltage measurement units 51 and 52. out1 and V out2 The maximum value of V out_max Based on this, the voltage measurement value V on the DC bus 10 side out Voltage measurement value V expressed in units [pu] out_b Get.

[0058] During charging, the voltage measurement value V out_b is the rated voltage V Rate is the minimum value, and the upper voltage value V UL That is, the voltage measurement value V out_b is the rated voltage V Rate If lower, the rated voltage V Rate and the upper voltage value V UL If it is higher, the upper voltage limit V UL Therefore, during charging, the control unit 60 sets the maximum value V out_max and obtain the rated voltage V base The unit is converted to [pu] as a percentage of the rated voltage V Rate is the lower limit, and the upper limit voltage V UL By using a limiter with an upper limit of out_b Get.

[0059] Then, the control unit 60 calculates the obtained voltage measurement value V out_b and the upper limit voltage V ULand rated voltage V Rate Using the above, the set voltage range (rated voltage V Rate Upper limit voltage value V UL (below) to the voltage measurement V out Calculate the value x that indicates the ratio of

number

[0060] [Effects of this embodiment] In this embodiment, the following effects can be obtained.

[0061] In this embodiment, as described above, the control unit 60 calculates the voltage measurement value V on the DC bus 10 side. out Based on the voltage measurement V out The characteristic coefficient m of the droop characteristic in at least one of the power conversion units 31 and 32 is set so that the i (characteristic value). As a result, the voltage measurement value V on the DC bus 10 side is adjusted. out Based on the voltage reading V out The droop characteristic coefficient m is set so that it falls within a specified range. i is adjusted, it is possible to prevent the voltage on the DC bus 10 from deviating from a predetermined range. Therefore, it is possible to adjust the characteristic coefficient m of the droop characteristic while keeping the voltage on the DC bus 10 within the predetermined range. i As a result, when at least one of the input and output of the power storage units 21 and 22 (plurality of power supply units) is controlled by the droop characteristic, the characteristic coefficient m i can be set appropriately.

[0062] For example, in order to balance the SOCs of the two power storage units 21 and 22 during discharge, the characteristic coefficient m i When changing the characteristic value, the characteristic coefficient m i 2 becomes larger, and the slope of the straight line in FIG. 2 becomes larger. In this case, even if the maximum value of current is output from the power storage unit 21 or 22 with the larger SOC value so that the sum of the outputs from the power storage units 21 and 22 satisfies a predetermined rated capacity (rated power), a certain amount of current must be output from the power storage unit with the smaller SOC value. This may cause the voltage of the DC power output from the power storage unit with the lower SOC to drop significantly in accordance with the droop characteristic. In this case, the voltage at the DC bus 10 becomes lower than the predetermined range. In contrast, in this embodiment, the voltage measurement value V on the DC bus 10 side out Based on the characteristic coefficient m of the droop characteristic i is adjusted, it is possible to prevent the voltage on the DC bus 10 from falling below a predetermined range. Similarly, during charging, the voltage measurement value V on the DC bus 10 side is out Based on the characteristic coefficient m of the droop characteristic i is adjusted, it is possible to prevent the voltage on the DC bus 10 from becoming higher than a predetermined range.

[0063] In this embodiment, as described above, the control unit 60 calculates the energy charge amount E i and the measured voltage V out Based on this, a characteristic coefficient m of the droop characteristic in at least one of the plurality of power conversion units 31 and 32 is calculated. i (characteristic value). This adjusts the energy charging amount E i and the voltage measurement V out and the characteristic coefficient m of the droop characteristics based on i is adjusted, so the energy charge amount E i The characteristic coefficient m of the droop characteristic is set to balance iTherefore, it is possible to adjust the amount of energy charged E of power storage units 21 and 22 while preventing the voltage of DC bus 10 from deviating from the predetermined range. i The characteristic coefficient m of the droop characteristic is set so that the equilibrium of i As a result, it is possible to adjust the energy charge amount E in the power storage units 21 and 22 while suppressing the operation of the DC power supply system 100 from becoming unstable due to the voltage of the DC bus 10 deviating from a predetermined range. i can be equilibrated more quickly.

[0064] In this embodiment, as described above, the control unit 60 determines the energy charging amount E i Based on the characteristic coefficient m i (characteristic value) and obtain the coefficient adjustment amount C for adjusting the voltage measurement value V out Based on the voltage reading V out The control unit 60 then acquires an adjustment index n for adjusting the coefficient adjustment amount C so that the coefficient m of the droop characteristic in at least one of the power conversion units 31 and 32 is within a predetermined range based on the acquired coefficient adjustment amount C and adjustment index n. i This adjusts the amount of energy charged E i The characteristic coefficient m is calculated using the coefficient adjustment amount C obtained based on i and voltage measurement V out Since the coefficient adjustment amount C can be adjusted using the adjustment index n obtained based on i The characteristic coefficient m of the droop characteristic is set to balance. i While adjusting the coefficient adjustment amount C, the coefficient adjustment amount C can be adjusted so that the voltage on the DC bus 10 side falls within a predetermined range using the adjustment index n. Therefore, by acquiring the coefficient adjustment amount C and the adjustment index n, it is possible to easily prevent the operation of the DC power supply system 100 from becoming unstable while adjusting the energy charging amount E in the power storage units 21 and 22 (plurality of power supply units). i Equilibration can be achieved easily and quickly.

[0065] In this embodiment, as described above, the control unit 60 determines the amount of energy charged E i The average energy charge E ave and the energy charge amount E in one of the power storage units 21 and 22. i The control unit 60 then obtains the coefficient adjustment amount C based on the difference between the voltage measurement value V out The voltage measurement value V for the preset voltage range is set so that it is included in the specified range. out The adjustment index n is obtained based on the ratio of the coefficient adjustment amount C to the average energy charging amount E ave and the energy charge amount E in one of the power storage units 21 and 22. i Since the energy charge amount E i The characteristic coefficient m i In addition, the adjustment index n is used to adjust the voltage measurement value V out The voltage measurement value V for the set voltage range is obtained based on the ratio of out The degree of adjustment of the coefficient adjustment amount C can be changed according to the ratio of the voltage measurement value V out As a result, the coefficient adjustment amount C can be adjusted more appropriately according to the magnitude of the energy charge amount E i The characteristic coefficient m i can be more appropriately adjusted.

[0066] In this embodiment, as described above, the control unit 60 controls the predetermined characteristic coefficient m i The reference value is m0, the coefficient adjustment amount is C, and the adjustment index is n. The characteristic coefficient m is calculated by the following equation (15). i Calculate.

number

number

[0067] In this embodiment, as described above, the control unit 60 sets the preset reference index n0 and calculates the voltage measurement value V for the set voltage range using a value between 0 and 1. out The adjustment term obtained based on the ratio is defined as k, and the adjustment index n is calculated using the following equation (17).

number

[0068] In this embodiment, as described above, the control unit 60 sets m to a real number greater than 1, and calculates the voltage measurement value V for the set voltage range. out The value indicating the ratio is set as x, and the adjustment term k is calculated by the following equation (18).

number

[0069] In this embodiment, as described above, the control unit 60 calculates the energy charging amount E for each of the plurality of power conversion units 31 and 32 using a common calculation formula. i and the voltage measurement V out and the characteristic coefficient m of the droop characteristics based on i (characteristic value). As a result, the characteristic coefficient m i can be appropriately set, the characteristic coefficient m i Therefore, the voltage at the DC bus 10 can be more reliably prevented from deviating from the predetermined range compared to when the characteristic coefficient m of the droop characteristic is adjusted. i Furthermore, it is possible to set the characteristic coefficient m to a more appropriate value by using a common calculation formula for each of the plurality of power conversion units 31 and 32. i By adjusting the characteristic coefficient m i This can prevent the control process for the adjustment from becoming complicated.

[0070] In this embodiment, as described above, the DC power supply system 100 includes a plurality of power storage units 21 and 22 that charge and discharge DC power. When controlling the power conversion units 31 and 32 to convert the DC power output from the plurality of power storage units 21 and 22, the control unit 60 converts the measured voltage V out The lower limit voltage V is set in advance so that it falls within a specified range. LL and the measured voltage V out and based on the characteristic coefficient m i When controlling the conversion of DC power input to the plurality of power storage units 21 and 22 by the power conversion units 31 and 32, the control unit 60 adjusts the voltage measurement value V out The upper limit voltage V is set in advance so that it falls within a predetermined range. UL and the measured voltage V out and based on the characteristic coefficient m iThis can prevent the voltage on DC bus 10 from becoming lower than a predetermined range when power storage units 21 and 22 are discharging, and can prevent the voltage on DC bus 10 from becoming higher than a predetermined range when power storage units 21 and 22 are charging. Therefore, when DC power from power storage units 21 and 22 is being output to external load 101 via DC bus 10, it is possible to effectively prevent the voltage of DC power supplied to load 101 from decreasing and causing unstable operation of load 101, and it is also possible to effectively prevent abnormalities in the charging operation due to overvoltage when power storage units 21 and 22 are being charged.

[0071] In addition, in this embodiment, as described above, when the control unit 60 controls the power conversion units 31 and 32 to convert the DC power output from the power storage units 21 and 22 (plurality of power supply units), the control unit 60 converts the voltage measurement value V out The minimum value V out_min Based on the characteristic coefficient m i Furthermore, when controlling the conversion of DC power input to the power storage units 21 and 22 by the power conversion units 31 and 32, the control unit 60 adjusts the voltage measurement value V on the DC bus 10 side of each of the plurality of power conversion units 31 and 32. out The maximum value of V out_max Based on the characteristic coefficient m i As a result, when power storage units 21 and 22 are outputting, the measured voltages V out Even if there is a difference in the voltage measured value V on each DC bus 10 side, out The minimum value V out_min Based on the characteristic coefficient m i By adjusting the voltage V, it is possible to more reliably prevent the voltage on the DC bus 10 side from becoming lower than the predetermined range. Also, even when power is being input to the power storage units 21 and 22, the voltage measurement values ​​V on the DC bus 10 side of each of the power storage units 21 and 22 are out The maximum value of V out_max Based on the characteristic coefficient m iBy adjusting the characteristic coefficient m i can be set more appropriately.

[0072] [Variations] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims rather than the description of the above embodiments, and further includes all modifications (variations) within the meaning and scope of the claims.

[0073] For example, in the above embodiment, the adjustment term k is the voltage measurement V out In the above example, the adjustment term k is calculated as the m-th root of x, where x is a real number m greater than 1, based on the value x indicating the ratio of the measured voltage to the set voltage range. However, the present invention is not limited to this. In the present invention, as in the first modification shown in FIG. 10, the adjustment term k may be set to monotonically increase linearly with respect to the value x indicating the ratio of the measured voltage to the set voltage range. That is, k = x. Furthermore, as in the second modification shown in FIG. 11, the adjustment term k may be set to monotonically increase linearly with respect to the value x indicating the ratio of the measured voltage to the set voltage range, with the slope changing and bending midway. Here, if the slope of the increase or decrease in the value of the adjustment term k changes in a bending manner midway, oscillations may occur in the control process at the point where the slope changes. Therefore, it is preferable to make the graph representing the increase or decrease in the value of the adjustment term k a smooth curve. Furthermore, the adjustment term k may be an inverse trigonometric function or a hyperbolic function of the value x indicating the ratio of the measured voltage to the set voltage range.

[0074] In the above embodiment, the characteristic coefficient m of the droop characteristic is used for inputting and outputting DC power from the power storage units 21 and 22 (plurality of power supply units). iAlthough an example of adjusting the characteristic value has been described, the present invention is not limited to this. In the present invention, the characteristic value of the droop characteristic may be adjusted when DC power is output from a fuel cell serving as a power supply unit. In this case, the state of charge of a fuel, such as hydrogen, in the fuel cell may be acquired as the energy charge amount instead of the SOC. Furthermore, three or more power supply units may be provided. Furthermore, the characteristic value may be adjusted either when the power supply unit outputs DC power or when DC power is input to the power supply unit. Furthermore, an AC power supply such as a flywheel may be provided as the power supply unit. In this case, when AC power from the power supply unit serving as an AC power supply is converted into DC power by a power conversion unit and output to a DC bus, the characteristic value of the droop characteristic may be adjusted in controlling the DC power output from the power conversion unit.

[0075] In the above embodiment, the characteristic coefficient m i Although an example has been shown in which control is performed to adjust (characteristic values), the present invention is not limited to this. In the present invention, control to adjust the characteristic values ​​may be performed in at least one of the multiple power conversion units.

[0076] In the above embodiment, the power storage units 21 and 22 (plurality of power supply units) have a common configuration, but the present invention is not limited to this. In the present invention, the plural power supply units may have different configurations. For example, the values ​​of rated output and rated capacity may be different for the plural power supply units (power storage units). In this case, control may be performed to adjust the characteristic coefficients (characteristic values) of the outputs of the plural power conversion units connected to the plural power supply units, respectively, using different arithmetic expressions or parameters. Furthermore, control may be performed to adjust the characteristic values ​​using different arithmetic expressions or parameters when discharging and charging the power storage unit.

[0077] In the above embodiment, the voltage measurement value V out Based on the characteristic coefficient mi The value of the adjustment index n, which is the power of the coefficient adjustment amount C that adjusts the voltage measurement value V out Characteristic coefficient m based on i Although an example in which the characteristic coefficient is adjusted using the coefficient adjustment amount has been shown, the present invention is not limited to this. In the present invention, the characteristic coefficient may be adjusted based on the voltage measurement value by calculating a value to be integrated into the coefficient adjustment amount based on the voltage measurement value. Also, the characteristic coefficient may be adjusted based on the voltage measurement value by calculating a value to be added to the coefficient adjustment amount based on the voltage measurement value. Also, the coefficient adjustment amount may be adjusted based on the voltage measurement value using other calculation methods. Also, the adjustment of the characteristic coefficient using the coefficient adjustment amount may be performed by combining calculations other than integration.

[0078] In the above embodiment, a plurality of voltage measurement values ​​V out1 and V out2 The minimum value of V out_min and multiple voltage measurements V out1 and V out2 The maximum value of V out_max By obtaining the characteristic coefficient m i Voltage measurement value V for adjusting (characteristic value) out Voltage measurement V out_a and V out_b Although an example has been shown in which a characteristic value is acquired, the present invention is not limited to this. In the present invention, an average value, a median value, or a mode value of a plurality of voltage measurement values ​​may be acquired to adjust the characteristic value. Furthermore, instead of separately measuring the voltage on the DC bus side of each of a plurality of power conversion units, a voltage measurement value on the DC bus side for adjusting the characteristic value may be acquired by measuring the voltage on the DC bus.

[0079] In the above embodiment, the control unit 60 determines the energy charging amount E i The control unit 60 obtains the SOC value indicating the characteristic coefficient m iAlthough an example in which a voltage command V (characteristic value) is acquired has been shown, the present invention is not limited to this. In the present invention, a control unit that performs control processing for adjusting the characteristic value may acquire a measured value such as a current value or a voltage value and calculate an energy charge amount such as SOC. Also, control devices such as controllers arranged for each of a plurality of power conversion units may calculate the characteristic value by transmitting and receiving signals to each other. For example, the voltage command V in the above embodiment may ref The control process of steps S1 to S7 for obtaining the characteristic coefficient m i The control unit 60 executes the control process from steps S1 to S5 for adjusting the (characteristic value), and the adjusted characteristic coefficient m i The voltage command V ref The control processes of steps S6 and S7, in which the characteristic coefficient m i The control cycle of the control process for obtaining the voltage command V ref The control period may be longer than the control period of the control process for acquiring the value.

[0080] 12, the control unit 60 and the controller 31a according to the third modification are also used to calculate the adjustment index n and the average energy charging amount E ave The control unit 60 calculates the characteristic coefficient m i (characteristic value) and voltage command V based on the droop characteristics ref The calculation of may be performed by the controllers 31a and 32a of the power conversion units 31 and 32. That is, a combination of the control unit 60 and the controllers 31a and 32a may be an example of the "control unit" in the claims of the present application.

[0081] In the above embodiment, the control unit 60 determines the predetermined characteristic coefficient m iAlthough the above example shows the case where the DC power output by each of the power conversion units 31 and 32 is controlled based on the droop characteristic that expresses the relationship between the current and voltage of the DC power using a predetermined characteristic value, the present invention is not limited to this. In the present invention, the droop characteristic may express the relationship between the output of the DC power and the voltage using a predetermined characteristic value. In other words, the control unit may be configured to control the DC power output by each of the multiple power conversion units based on the droop characteristic that expresses the relationship between the voltage and either the current or the power of the DC power using a predetermined characteristic value.

[0082] In the above embodiment, as shown in FIG. 3, the control unit 60 calculates the current measurement value I i The voltage command V ref to the controllers 31a and 32a of the power conversion units 31 and 32, but the present invention is not limited to this. In the present invention, a current command may be generated based on the droop characteristics by inputting a voltage measurement value acquired from a voltage measurement unit, and the generated current command may be transmitted to each controller of the multiple power conversion units. In this case, the power conversion units control the switching operation based on the acquired current command.

[0083] In the above embodiment, the energy charge amount E i To balance the SOC, the droop characteristic coefficient m i Although an example in which the characteristic value is changed has been shown, the present invention is not limited to this. i The droop characteristics may be changed so that the state of charge (SOC) reaches the target energy charging amount values ​​set separately for power storage units 21 and 22.

[0084] In the above embodiment, the characteristic coefficient m iIn the above example, V is a droop coefficient, which is a proportional constant that represents the ratio of the amount of change in voltage to the amount of change in current, but the present invention is not limited to this. In the present invention, the characteristic value may be an initial setting value that represents the relationship between DC power and voltage in the droop characteristic. For example, in the case of the rated voltage V in FIG. Rate (Rated voltage V base ) may be adjusted as a characteristic value. That is, the "characteristic value" includes at least one of the "slope (proportionality constant)" and the "intercept" in the droop characteristic expressed by a linear function. [Explanation of symbols]

[0085] 10 DC bus 21, 22 Power storage unit (power supply unit) 31, 32 Power conversion section 60 Control Unit 100 DC power supply system

Claims

1. a plurality of power supply units that perform at least one of supplying power to a common DC bus to which DC power is applied and receiving power from the common DC bus; a plurality of power conversion units provided for each of the plurality of power supply units, the power conversion units converting input power between each of the plurality of power supply units and the DC bus and outputting the converted power; a control unit that controls the power output by each of the plurality of power conversion units based on a droop characteristic that indicates a relationship between the output of DC power and a voltage using a predetermined characteristic value, the control unit is configured to adjust, based on a voltage measurement value on the DC bus side, the characteristic value of the droop characteristic in at least one of the plurality of power conversion units so that the voltage measurement value falls within a predetermined range.

2. 2. The DC power supply system according to claim 1, wherein the control unit is configured to adjust the characteristic value of the droop characteristic of at least one of the plurality of power conversion units based on an energy charge amount indicating an energy charge state in each of the plurality of power supply units and the voltage measurement value.

3. the characteristic value includes a characteristic coefficient that represents a relationship between the output of DC power and the voltage in the droop characteristic; The control unit obtaining a coefficient adjustment amount for adjusting the characteristic coefficient based on the energy charging amount, and obtaining an adjustment index for adjusting the coefficient adjustment amount based on the voltage measurement value so that the voltage measurement value falls within the predetermined range; 3. The DC power supply system according to claim 2, wherein the DC power supply system is configured to adjust the characteristic coefficient of the droop characteristic in at least one of the plurality of power conversion units based on the acquired coefficient adjustment amount and the adjustment index.

4. The control unit acquiring the coefficient adjustment amount based on a difference between an average energy charging amount, which is an average of the energy charging amounts in the plurality of power supply units, and the energy charging amount in one of the plurality of power supply units; 4. The DC power supply system according to claim 3, wherein the adjustment index is obtained based on a ratio of the measured voltage to a preset voltage range that is set so that the measured voltage falls within the predetermined range.

5. The control unit sets the predetermined reference value of the characteristic coefficient m ０ The coefficient adjustment amount is C, the adjustment index is n, and the characteristic coefficient m is calculated by the following equation (1): ｉ The DC power supply system according to claim 4 , wherein the following is calculated: [Equation 1] The average energy charge amount is E ａｖｅ and the amount of energy charged in one of the plurality of power supply units is E ｉ The coefficient adjustment amount C is calculated by the following equation (2). [Equation 2]

6. The control unit sets a preset reference index to n ０ 6. The DC power supply system according to claim 5, wherein an adjustment term k is obtained based on a ratio of the measured voltage value to the set voltage range and has a value between 0 and 1, and the adjustment index n is calculated by the following equation (3): [Equation 3]

7. 7. The DC power supply system according to claim 6, wherein the control unit calculates the adjustment term k by the following equation (4), where m is a real number greater than 1 and x is a value indicating a ratio of the measured voltage value to the set voltage range: [Equation 4]

8. 3. The DC power supply system according to claim 2, wherein the control unit is configured to adjust the characteristic value of the droop characteristic for each of the plurality of power conversion units based on the charged energy amount and the measured voltage value using a common arithmetic expression.

9. the plurality of power supply units include a plurality of power storage units that charge and discharge DC power, The control unit when controlling the conversion of the DC power output from the plurality of power storage units by the power conversion unit, adjusting the characteristic value based on the voltage measurement value and a lower limit voltage value that is set in advance so that the voltage measurement value falls within the predetermined range; 2. The DC power supply system according to claim 1, wherein, when controlling conversion of the DC power input to the plurality of power storage units by the power conversion unit, the characteristic value is adjusted based on the voltage measurement value and a preset upper limit voltage value such that the voltage measurement value falls within the predetermined range.

10. The control unit adjusting the characteristic value based on a minimum value of the voltage measurement values ​​at the DC bus side of each of the plurality of power conversion units when controlling the conversion of the power output from the plurality of power supply units by the power conversion unit; 2. The DC power supply system according to claim 1, wherein, when controlling conversion of power input to the plurality of power supply units by the power conversion unit, the characteristic value is adjusted based on a maximum value among the voltage measurement values ​​on the DC bus side of each of the plurality of power conversion units.

11. a step of acquiring a voltage measurement value on the DC bus side of a plurality of power conversion units that are provided for each of a plurality of power supply units that perform at least one of supplying DC power to a common DC bus to which DC power is applied and receiving DC power from the common DC bus, and that convert input power between each of the plurality of power supply units and the DC bus and output the converted power; and controlling the power output by each of the plurality of power conversion units based on a droop characteristic that represents a relationship between the output of DC power and the voltage using a predetermined characteristic value, a step of adjusting, based on the voltage measurement value on the DC bus side, the characteristic value of a droop characteristic in at least one of the plurality of power conversion units so that the voltage measurement value falls within a predetermined range, said step of controlling the power output by each of the plurality of power conversion units including:

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