Distributed power supply system

Abstract

To provide a distributed power supply system capable of preventing power generation by a solar battery from being suppressed even when a power generation amount of the solar battery is reduced by variation in a power generation condition.SOLUTION: A distributed power supply system comprises: a storage battery; a current adjustment unit for adjusting charging current and discharging current flowing between an electric wire network and the storage battery; a solar battery capable of supplying DC power to the electric wire network; and a current control unit for referring to correspondence to control the current adjustment unit. When electric wire network voltage is higher than set voltage and a value of a parameter indicating a power generation condition of the solar battery becomes a value deviating from a reference range, which is a numerical range of the power generation condition to be a reference, and a value reducing a power generation amount of the solar battery, the current control unit changes the correspondence to control the current adjustment unit so that charging current larger than charging current made to be flow when the value of the parameter is within the reference range flows.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a distributed power supply system. [Background technology]

[0002] A distributed power supply system is a system in which power is supplied from multiple devices connected to an electric grid. For example, Patent Document 1 discloses a distributed power supply system in which generators using renewable energy, such as solar cells and wind power generators, as well as storage batteries and fuel cells for stabilizing power, are connected to an electric grid. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6923231 Summary of the Invention [Problem to be solved by the invention]

[0004] The amount of power generated by a solar cell varies depending on the power generation conditions. If the power generation conditions change and the amount of power generated by the solar cell decreases while the storage battery is collecting DC power from the power grid, the voltage of the power grid drops, making it difficult for the storage battery to collect DC power, which may result in reduced power generation by the solar cell. In such a case, solar energy, which is a renewable energy source, cannot be fully utilized to charge the storage battery. For this reason, there is room for improvement in technology that uses solar energy to charge the storage battery. In this regard, the distributed power generation system described in Patent Document 1 does not take into consideration the fact that a decrease in the amount of power generated by the solar cell will lead to reduced power generation by the solar cell.

[0005] The present invention has been made to solve at least some of the above-mentioned problems, and aims to provide a distributed power supply system that can prevent power generation by solar cells from being suppressed even when the amount of power generated by the solar cells decreases due to fluctuations in power generation conditions. [Means for solving the problem]

[0006] The present invention has been made to solve at least part of the above-mentioned problems, and can be realized in the following aspects.

[0007] (1) According to one aspect of the present invention, there is provided a distributed power system including: a storage battery capable of supplying and recovering DC power to and from an electric grid; a current adjusting unit that adjusts a current flowing between the electric grid and the storage battery to either a charging current recovered from the electric grid to the storage battery or a discharging current supplied from the storage battery to the electric grid; a solar cell capable of supplying DC power to the electric grid; and a current control unit that controls the current adjusting unit by referring to a correspondence relationship between a voltage difference between a set voltage set as the voltage of the storage battery and an electric grid voltage that is the voltage of the electric grid, the charging current, and the discharging current, wherein, when the electric grid voltage is higher than the set voltage, if a value of a parameter indicating a power generation condition of the solar cell falls outside a reference range that is a numerical range of the power generation condition and that reduces the amount of power generated by the solar cell, the current control unit controls the current adjusting unit to flow the charging current greater than the charging current that flows when the value of the parameter is within the reference range.

[0008] When the value of the parameter indicating the solar cell's power generation conditions falls outside the reference range and reduces the amount of power generated by the solar cell, the grid voltage drops due to the reduced power generation by the solar cell. In such a case, the voltage difference between the set voltage and the grid voltage decreases, reducing the charging current. This makes it difficult for the storage battery to recover power even if the solar cell generates power, resulting in reduced power generation by the solar cell. In such a case, this configuration changes the correspondence, thereby controlling the current adjustment unit to flow a charging current greater than the charging current that flows when the parameter indicating the solar cell's power generation conditions is within the reference range. This prevents the reduction in power generation by the solar cell even when the amount of power generated by the solar cell decreases due to fluctuations in the power generation conditions, allowing the storage battery to be charged by effectively utilizing sunlight.

[0009] (2) In the distributed power system of the above form, the parameter may be solar radiation intensity, and when the power grid voltage is higher than the set voltage and the value of the solar radiation intensity is smaller than the lower limit value of the reference range, the current control unit may control the current adjustment unit to change the correspondence so that the charging current flows that is larger than the charging current that flows when the value of the solar radiation intensity is within the reference range. Regarding the solar radiation intensity, one of the solar cell power generation conditions, the amount of power generated by the solar cell tends to decrease as the value decreases. Therefore, when the solar radiation intensity value is lower than the lower limit of the reference range, the amount of power generated by the solar cell decreases, causing a drop in the power grid voltage. In such a case, this configuration changes the correspondence to control the current adjustment unit so that a charging current greater than the charging current that flows when the solar radiation intensity value is within the reference range can be supplied. Therefore, even when the amount of power generated by the solar cell decreases due to a decrease in solar radiation intensity, suppression of power generation by the solar cell can be prevented, and sunlight can be effectively used to charge the storage battery.

[0010] (3) In the distributed power supply system of the above form, the parameter may be the temperature of the solar cell, and when the grid voltage is higher than the set voltage and the temperature value is greater than the upper limit of the reference range, the current control unit may control the current adjustment unit to change the correspondence so that the charging current flow is greater than the charging current flowing when the temperature value is within the reference range. Among the solar cell power generation conditions, the higher the solar cell temperature, the lower the amount of power generated by the solar cell. Therefore, when the solar cell temperature exceeds the upper limit of the reference range, the power generation by the solar cell decreases, causing the grid voltage to drop. In such a case, this configuration changes the correspondence to control the current adjustment unit so that a charging current greater than the charging current that flows when the solar cell temperature is within the reference range can be supplied. This prevents the increase in solar cell temperature from suppressing power generation, enabling the storage battery to be charged effectively using sunlight.

[0011] (4) In the distributed power supply system of the above aspect, when the grid voltage is higher than the set voltage and the grid voltage becomes lower than a reference voltage, the current control unit may control the current adjustment unit to change the correspondence so that the charging current flows that is larger than the charging current that flows when the grid voltage is higher than the reference voltage. The grid voltage may be lower than the reference voltage when a DC power supply from a DC power source other than the solar cell is reduced. In such a case, the current regulator is controlled to flow a charging current greater than the charging current flowing when the grid voltage is higher than the reference voltage by changing the correspondence. This prevents a drop in grid voltage from suppressing power generation by the solar cell, enabling the solar cell to be effectively used to charge the storage battery.

[0012] The present invention can be realized in various forms, for example, as a control method for a distributed power supply system, a computer program for controlling a distributed power supply system, a server device for distributing the computer program, a non-transitory storage medium on which the computer program is stored, etc. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is an explanatory diagram illustrating the configuration of a distributed power supply system according to a first embodiment; [Figure 2] FIG. 4 is an explanatory diagram for explaining switching between charging and discharging by a main engine control unit. [Figure 3] FIG. 1 is an explanatory diagram showing that the amount of power generated by a solar cell varies depending on the power generation conditions. [Figure 4] FIG. 1 is an explanatory diagram showing that the amount of power generated by a solar cell varies depending on the power generation conditions. [Figure 5] FIG. 10 is an explanatory diagram showing a decrease in charging current when the temperature of the solar cell becomes high. [Figure 6] FIG. 10 is an explanatory diagram of control performed when the amount of power generated by the solar cell decreases. [Figure 7] 10 is a flowchart showing a procedure for a charging current adjustment process. [Figure 8] FIG. 10 is an explanatory diagram showing a modified example of the correspondence relationship. [Figure 9] FIG. 10 is an explanatory diagram showing a modified example of the correspondence relationship. DETAILED DESCRIPTION OF THE INVENTION

[0014] First Embodiment FIG. 1 is an explanatory diagram illustrating the configuration of a distributed power supply system 1 according to one embodiment of the present invention. The distributed power supply system 1 is a system in which a main unit 10, an auxiliary unit 20, and one or more devices capable of recovering or supplying DC power through a chemical reaction are connected via an electric wire network NT. In the example of FIG. 1, the one or more devices include three devices, specifically, a first device 30, a second device 40, and a third device 60. The distributed power supply system 1 is a system in which the DC power to be supplied to a load 90 via the electric wire network NT is shared and output by the main unit 10, the auxiliary unit 20, the first device 30, and the third device 60. The distributed power supply system 1 also includes a storage unit 50 and a device control unit 70.

[0015] The main machine 10 is connected to the electric power network NT and is capable of supplying and recovering DC power to and from the electric power network NT. The main machine 10 includes a storage battery 12, a converter 14, and a main machine control unit 16. The storage battery 12, which is a secondary battery, is connected to the electric power network NT via the converter 14, which is a DC / DC converter. The main machine control unit 16, which controls the main machine 10, controls the switching of the converter 14 in accordance with the voltage difference between a set voltage set as the voltage of the storage battery 12 and an electric power network voltage, which is the voltage of the electric power network NT, thereby controlling the charging and discharging of the storage battery 12. The set voltage is a value set in accordance with the electromotive force of the storage battery 12 and is also a value used to control the converter 14. In other words, the converter 14 corresponds to a current adjustment unit that adjusts the current flowing between the electric power network NT and the storage battery 12 to either a charging current recovered from the electric power network NT to the storage battery 12 or a discharging current supplied from the storage battery 12 to the electric power network NT. Furthermore, the main engine control unit 16 corresponds to a current control unit that controls the converter 14, which is a current adjustment unit.

[0016] The auxiliary unit 20 is a device connected to the electric power network NT and capable of supplying DC power to the electric power network NT. The auxiliary unit 20 includes a converter 24 and an auxiliary unit control unit 26. The converter 24 converts the power supplied from a power source 80 and supplies the converted power to the electric power network NT. In this embodiment, the power source 80 is a wind power generator that generates AC power, and therefore the converter 24 is an AC / DC converter. In other words, the DC power supplied from the auxiliary unit 20 to the electric power network NT is derived from power generated using renewable energy. The auxiliary unit control unit 26, which controls the auxiliary unit 20, controls the switching of the converter 24.

[0017] The first device 30 is a device capable of supplying DC power to the electric wire network NT. The first device 30 includes a solar cell 32 and a converter 34. The solar cell 32 is connected to the electric wire network NT via the converter 34, which is a DC / DC converter. The converter 34 converts the DC power supplied from the solar cell 32 and supplies it to the electric wire network NT.

[0018] The second device 40 is a device capable of recovering DC power from the electric wire network NT through a chemical reaction. The second device 40 includes a water electrolysis unit 42 and a converter 44. The water electrolysis unit 42 is connected to the electric wire network NT via the converter 44, which is a DC / DC converter. The converter 44 converts the power recovered from the electric wire network NT and supplies the converted power to the water electrolysis unit 42. The water electrolysis unit 42 electrolyzes water using the DC power supplied from the electric wire network NT via the converter 44. In other words, the water electrolysis unit 42 is a production unit that recovers DC power from the electric wire network NT and produces reactants through a chemical reaction. Hydrogen produced by the electrolysis of water is stored in the storage unit 50.

[0019] The third device 60 is a device capable of supplying DC power to the electric wire network NT through a chemical reaction. The third device 60 includes a fuel cell 62 and a converter 64. The fuel cell 62 is connected to the electric wire network NT via the converter 64, which is a DC / DC converter. The fuel cell 62 generates DC power using hydrogen and oxygen stored in the storage unit 50. The converter 64 converts the DC power supplied from the fuel cell 62 and supplies it to the electric wire network NT. In other words, the fuel cell 62 is a power generation unit capable of supplying DC power generated using reactants to the electric wire network NT.

[0020] The equipment control unit 70 controls the first equipment 30, the second equipment 40, and the third equipment 60. The above-mentioned main equipment control unit 16 and auxiliary equipment control unit 26 are separate control units different from the equipment control unit 70. The equipment control unit 70 mainly controls the supply of DC power from the first equipment 30 and the third equipment 60 to the electric wire network NT, and the recovery of DC power from the electric wire network NT by the second equipment 40.

[0021] The output voltage from the first device 30 fluctuates depending on the irradiance of sunlight irradiating the solar cell 32 and the temperature of the solar cell 32. In the distributed power system 1, a main unit 10 equipped with a storage battery 12 is provided in parallel with the power grid NT. The main unit 10 switches between charging and discharging depending on fluctuations in the output voltage from the first device 30 (i.e., fluctuations in the power grid voltage), thereby maintaining the voltage of the power grid NT within a certain range. In other words, the main unit 10 is a device responsible for maintaining the voltage of the power grid NT. Typically, in the distributed power system 1, the DC power to be supplied to the load 90 via the power grid NT is shared and output mainly by the main unit 10 and the first device 30. At this time, the second device 40 appropriately recovers DC power from the power grid NT depending on the DC power supplied to the power grid NT, and generates hydrogen and stores the hydrogen in the storage unit 50. In this embodiment, while DC power is being supplied from the main unit 10 to the power grid NT, the supply of DC power from the third device 60 to the power grid NT is stopped.

[0022] FIG. 2 is an explanatory diagram illustrating switching between charging and discharging by the main machine control unit 16. When the main machine control unit 16 controls charging and discharging of the storage battery 12, the line segment Ln shown in FIG. 2 is used to determine whether to flow a charging current from the electric grid NT to the storage battery 12 or a discharging current from the storage battery 12 to the electric grid NT. In FIG. 2, the vertical axis represents voltage and the horizontal axis represents current. The current on the horizontal axis represents discharging in the positive direction, where the storage battery 12 supplies power to the electric grid NT, and charging in the negative direction, where the storage battery 12 recovers power from the electric grid NT. As described above, the electric grid voltage NV represents the voltage of the electric grid NT and moves along the line segment Ln according to its fluctuations. As described above, the set voltage Vs represents the voltage set as the voltage of the storage battery 12 according to the electromotive force of the storage battery 12 and is located at the intersection of the vertical axis and the line segment Ln. The voltage difference ΔV indicates the voltage difference between the set voltage Vs and the power grid voltage NV (ΔV=Vs-NV).

[0023] In FIG. 2, when the grid voltage NV is higher than the set voltage Vs (ΔV=Vs-NV<0, when ΔV is negative), the main machine control unit 16 controls the converter 14 to allow a charging current (negative current) to flow from the grid NT to the storage battery 12. Specifically, when the grid voltage NV is at the position shown in FIG. 2, the main machine control unit 16 uses the line segment Ln to control the converter 14 to allow a charging current Cc of a magnitude corresponding to the voltage difference ΔV to flow. In FIG. 2, when the grid voltage NV is lower than the set voltage Vs (ΔV=Vs-NV>0, when ΔV is positive), the main machine control unit 16 controls the converter 14 to allow a discharging current (positive current) to flow from the storage battery 12 to the grid NT. Specifically, when the grid voltage NV is at the right side of the vertical axis in FIG. 2, the main machine control unit 16 uses the line segment Ln to control the converter 14 to allow a discharging current of a magnitude corresponding to the voltage difference ΔV to flow. In this way, the line segment Ln, which is referenced when controlling the converter 14 (current regulator), shows the relationship between the voltage difference ΔV between the set voltage Vs and the grid voltage NV, and the charge current and discharge current. More specifically, the line segment Ln shows the relationship between the polarity and absolute value of the voltage difference ΔV between the set voltage Vs and the grid voltage NV, and the charge current and discharge current.

[0024] FIG. 3 is an explanatory diagram for explaining that the amount of power generated by the solar cell 32 varies depending on the power generation conditions. FIG. 3 explains that the amount of power generated by the solar cell 32 varies depending on the solar radiation intensity, which is one of the power generation conditions. In FIG. 3, the vertical axis on the left side indicates the output current, the vertical axis on the right side indicates the output power, and the horizontal axis indicates the output voltage. Curve Sr1 indicates the amount of power generated by the solar cell 32 when the solar radiation intensity is 1200 W / m 2 The curve Sr2 shows the relationship between the output current and the output voltage output from the solar cell 32 under the conditions of the solar radiation intensity of 1000 W / m 2 The curve Sr3 shows the relationship between the output current and the output voltage output from the solar cell 32 under the conditions of the solar radiation intensity of 700 W / m 2 1 shows the relationship between the output current and the output voltage output from the solar cell 32 under the above conditions.

[0025] Curve Pr1 is for a solar radiation intensity of 1200 W / m 2 The curve Pr1 shows the relationship between the output voltage and the output power output from the solar cell 32 under the conditions of the solar radiation intensity of 1200 W / m 2 It is shown that when the output voltage is V1 under the condition above, the output power becomes maximum power P1Max. The maximum power P1Max is the output power indicated by point r1 corresponding to the output voltage V1. The curve Pr2 indicates the maximum power P1Max when the solar radiation intensity is 1000 W / m 2 The curve Pr2 shows the relationship between the output voltage and the output power output from the solar cell 32 under the conditions of the solar radiation intensity of 1000 W / m 2 It is shown that when the output voltage is V2 under the condition, the output power becomes the maximum power P2Max. The maximum power P2Max is the output power indicated by the point r2 corresponding to the output voltage V2. The curve Pr3 shows the maximum power P2Max when the solar radiation intensity is 700 W / m 2 The curve Pr3 shows the relationship between the output voltage and the output power output from the solar cell 32 under the conditions of the solar radiation intensity of 700 W / m 2It is shown that when the output voltage is V3 under the above condition, the output power becomes maximum power P3Max. Maximum power P3Max is the output power indicated by point r3 corresponding to output voltage V3. As maximum power P1Max is the largest among maximum powers P1Max to P3Max, solar cell 32 tends to generate more power as the solar radiation intensity increases.

[0026] FIG. 4 is an explanatory diagram illustrating that the amount of power generated by solar cell 32 varies depending on the power generation conditions. FIG. 4 illustrates that the amount of power generated by solar cell 32 varies depending on the temperature of solar cell 32, which is one of the power generation conditions. In FIG. 4, the left and right vertical and horizontal axes are the same as those in FIG. 3. Curve Tm1, indicated by a two-dot chain line, shows the relationship between the output current and output voltage output from solar cell 32 when the temperature of solar cell 32 is 0°C. Curve Tm2, ​​indicated by a dashed line, shows the relationship between the output current and output voltage output from solar cell 32 when the temperature of solar cell 32 is 25°C. Curve Tm3, indicated by a solid line, shows the relationship between the output current and output voltage output from solar cell 32 when the temperature of solar cell 32 is 50°C.

[0027] Curve Pm1 shows the relationship between the output voltage and output power output from solar cell 32 when the temperature of solar cell 32 is 0°C. Curve Pm1 shows that when the temperature of solar cell 32 is 0°C and the output voltage is v1, the output power becomes maximum power P1max. Maximum power P1max is the output power corresponding to output voltage v1. Curve Pm2 shows the relationship between the output voltage and output power output from solar cell 32 when the temperature of solar cell 32 is 25°C. Curve Pm2 shows that when the temperature of solar cell 32 is 25°C and the output voltage is V2, the output power becomes maximum power P2max. Maximum power P2max is the output power corresponding to output voltage v2. Curve Pm3 shows the relationship between the output voltage and output power output from solar cell 32 when the temperature of solar cell 32 is 50°C. Curve Pm3 shows that when the temperature of solar cell 32 is 50°C and the output voltage is v3, the output power becomes maximum power P3max. Maximum power P3max is the output power corresponding to output voltage v3. As the maximum power P1max is the largest among the maximum powers P1max to P3max, the amount of power generated by the solar cell 32 tends to increase as the temperature decreases. In this embodiment, the device control unit 70 controls the converter 34 to adjust the output voltage of the solar cell 32 so that the amount of power generated (output power) by the solar cell 32 is maximized.

[0028] FIG. 5 is an explanatory diagram showing the decrease in charging current that occurs when the temperature of the solar cell 32 becomes high. In FIG. 5, the vertical and horizontal axes are the same as in FIG. 4. The grid voltage NVl represents the grid voltage NV when the solar cell 32 is relatively low temperature. The grid voltage NVh represents the grid voltage NV when the solar cell 32 is relatively high temperature. When the amount of power generation decreases due to the high temperature of the solar cell 32, the voltage of the grid NT decreases, as represented by the change from the grid voltage NVl to the grid voltage NVh. At this time, a state in which a charging current Cl flows, whose magnitude corresponds to the voltage difference ΔVl between the set voltage Vs and the grid voltage NVl, transitions to a state in which a charging current Ch flows, whose magnitude corresponds to the voltage difference ΔVh between the set voltage Vs and the grid voltage NVh. In other words, since |ΔVl| > |ΔVh|, |Cl| > |Ch|. || represents an absolute value. When the value of the charging current decreases in this way, it becomes difficult for the storage battery 12 to recover power even if the solar cell 32 generates power, resulting in suppression of power generation by the solar cell 32. In this embodiment, when the amount of power generated by the solar cell 32 decreases due to fluctuations in power generation conditions (solar radiation intensity and temperature of the solar cell 32), control is performed to prevent suppression of power generation by the solar cell 32. This control will be described using Figures 6 and 7.

[0029] FIG. 6 is an explanatory diagram of control performed when the amount of power generated by the solar cell 32 decreases. In FIG. 6, the line segment Ln is indicated by a dashed line. When the grid voltage NV is higher than the set voltage Vs, if the value of a parameter indicating the power generation conditions of the solar cell 32 falls outside a reference range, which is a numerical range of reference power generation conditions, and the value reduces the amount of power generated by the solar cell 32, the main machine control unit 16 changes the line segment Ln, which represents the correspondence relationship referenced when controlling the converter 14, to a line segment Ln1. If the value of the parameter indicating the power generation conditions of the solar cell 32 falls outside the reference range and reduces the amount of power generated by the solar cell 32, the grid voltage NV decreases due to the reduced amount of power generated by the solar cell 32. In such a case, the voltage difference V between the set voltage Vs and the grid voltage NV decreases, reducing the charging current. This makes it difficult for the storage battery 12 to recover power even if the solar cell 32 generates power, resulting in reduced power generation by the solar cell 32. In this regard, the main machine control unit 16 changes the line segment Ln to a line segment Ln1 to prevent suppression of power generation by the solar battery 32. Details will be explained below.

[0030] The parameters indicating the power generation conditions of the solar cell 32 are the solar radiation intensity and the temperature of the solar cell 32. First, control using the solar radiation intensity among the parameters will be described. In this embodiment, the reference range of the solar radiation intensity is 1000 to 1200 W / m 2 In this case, the value indicating the solar radiation intensity that falls outside the reference range and reduces the amount of power generated by the solar cell 32 is 1000 W / m 2 Therefore, when the power grid voltage NV is higher than the set voltage Vs, the main machine control unit 16 determines whether the value of the solar radiation intensity is lower than the lower limit of the reference range (1000 W / m in this embodiment). 2 ), the corresponding line segment Ln is changed to line segment Ln1.

[0031] Next, control using the temperature of the solar cell 32, one of the parameters, will be described. In this embodiment, the reference range for the temperature of the solar cell 32 is 0 to 25°C. In this case, a value indicating the temperature of the solar cell 32 that falls outside the reference range and reduces the amount of power generated by the solar cell 32 is a value greater than 25°C. Therefore, when the power grid voltage NV is higher than the set voltage Vs, if the temperature value of the solar cell 32 is greater than the upper limit of the reference range (25°C in this embodiment), the main machine control unit 16 changes the corresponding line segment Ln to line segment Ln1.

[0032] The main machine control unit 16 receives parameter values ​​indicating the power generation conditions of the solar cell 32 to determine whether the solar radiation intensity value is lower than the lower limit of the reference range and whether the temperature value of the solar cell 32 is higher than the upper limit of the reference range. The parameter values ​​used by the main machine control unit 16 as the basis for the determination may be current values ​​or predicted values, i.e., values ​​from the current time onward. The information received by the main machine control unit 16 may indicate the parameter values ​​themselves or may indicate the value of another parameter that can be used to estimate the parameter values. When the solar radiation intensity value is lower than the lower limit of the reference range or when the temperature value of the solar cell 32 is higher than the upper limit of the reference range, the main machine control unit 16 changes the correspondence from line segment Ln to line segment Ln1 and controls the converter 14 using line segment Ln1. When the solar radiation intensity value and the temperature value of the solar cell 32 are both within the reference ranges, the main machine control unit 16 controls the converter 14 using line segment Ln.

[0033] As shown in FIG. 6, line segment Ln1 has the same slope as line segment Ln, but its intersection with the vertical axis is lower than that of line segment Ln. Changing line segment Ln to line segment Ln1 means changing set voltage Vs to set voltage Vs1 (shown in FIG. 6). The change from line segment Ln to line segment Ln1 and the resulting change in charging current will be described in detail with reference to FIG. 6. If the value of a parameter indicating the power generation conditions of the solar cell 32 falls outside the reference range and decreases the amount of power generated by the solar cell 32, it is determined that the power grid voltage NV has decreased due to the influence of the parameter (the estimated change amount is assumed to be Vα). Therefore, the main machine control unit 16 changes the line segment Ln to refer to line segment Ln1, which lowers the set voltage Vs to set voltage Vs1 (Vs1 = Vs - Vα), instead of line segment Ln, so that a charging current that does not reflect the influence of the parameter flows. The main machine control unit 16 then references the line segment Ln1 and controls the converter 14 to flow a charging current CN1 based on the voltage difference ΔV1 (ΔV1 = Vs1 - NV1) between the set voltage Vs1 and the grid voltage NV (NV1) on the line segment Ln1, as shown in Fig. 6. When the line segment Ln is referenced, the converter 14 is controlled to flow a charging current Ch based on the voltage difference ΔV between the set voltage Vs and the grid voltage NV. However, the charging current CN1 is greater than the charging current Ch. That is, when the grid voltage NV is higher than the set voltage Vs, if the value of a parameter indicating the power generation condition of the solar cell 32 is outside the reference range and reduces the amount of power generated by the solar cell 32, the main machine control unit 16 controls the converter 14 to flow a charging current (charging current CN1 based on the line segment Ln1) that is greater than the charging current (charging current Ch based on the line segment Ln) that flows when the parameter (solar radiation intensity or temperature of the solar cell 32) is within the reference range.In other words, since the set voltage is different in the changed correspondence relationship (line segment Ln1) compared to the correspondence relationship before the change (line segment Ln) (set voltage Vs is different from set voltage Vs1), even under the same magnitude of electric grid voltage NV, the charging current (charging current CN1) flowing based on the electric grid voltage NV (NV1) with reference to the changed correspondence relationship (line segment Ln1) is greater than the charging current (charging current Ch) flowing based on the electric grid voltage NV with reference to the correspondence relationship before the change (line segment Ln).

[0034] 7 is a flowchart showing the procedure of the charging current adjustment process executed by the main machine control unit 16. The charging current adjustment process is a process that is repeatedly executed when the power line network voltage NV is higher than the set voltage Vs, and is a process that adjusts the magnitude of the charging current.

[0035] When the charging current adjustment process is started, the main machine control unit 16 receives the values ​​of parameters indicating the power generation conditions of the solar cell 32 (step S11). At this time, the main machine control unit 16 receives the values ​​of the solar radiation intensity and the temperature of the solar cell 32 as the values ​​of the parameters indicating the power generation conditions of the solar cell 32.

[0036] Next, the main machine control unit 16 determines whether the received parameter value is outside the reference range and is a value that reduces the amount of power generated by the solar cell 32 (step S13). Specifically, the main machine control unit 16 determines whether the value of the solar radiation intensity is below the lower limit of the reference range (for example, 1000 W / m 2 ) and whether the temperature value of the solar cell 32 is greater than the upper limit of the reference range (e.g., 25°C). If it is determined that the received parameter value is outside the reference range and is not a value that reduces the amount of power generated by the solar cell 32 (step S13: NO), the main machine control unit 16 controls the converter 14 by referring to the initial correspondence relationship (e.g., line segment Ln) (step S15). Note that a negative determination is made in step S13 when the value of the solar radiation intensity and the value of the temperature of the solar cell 32 are both within the reference range. After executing step S15, the main machine control unit 16 ends the charging current adjustment process.

[0037] On the other hand, if the main machine control unit 16 determines that the received parameter value is outside the reference range and reduces the amount of power generated by the solar cell 32 (step S13: YES), the main machine control unit 16 controls the converter 14 by referring to another correspondence relationship (e.g., line segment Ln1) obtained by changing the initial correspondence relationship (e.g., line segment Ln) (step S17). When changing from line segment Ln described in FIG. 6 to line segment Ln1, the estimated change amount Vα may be set larger as the parameter value indicating the power generation condition of the solar cell 32 deviates from the reference range, and the set voltage Vs1 (Vs1 = Vs - Vα) may be calculated. That is, the line segment Ln1 may be positioned lower than line segment Ln as the parameter value indicating the power generation condition of the solar cell 32 deviates from the reference range. A positive determination in step S13 refers to at least one of the following cases: the solar radiation intensity value is smaller than the lower limit of the reference range; or the temperature value of the solar cell 32 is larger than the upper limit of the reference range. After executing step S17, the main machine control unit 16 ends the charging current adjustment process. In this way, in the charging current adjustment process, the main machine control unit 16 adjusts the magnitude of the charging current by controlling the converter 14 with reference to the correspondence relationship selected according to the value of the parameter indicating the power generation condition of the solar battery 32.

[0038] As described above, according to the distributed power supply system 1 of the first embodiment, by changing the correspondence relationship, the converter 14 is controlled so that a charging current larger than the charging current that flows when the value of the parameter indicating the power generation condition of the solar cell 32 is within the reference range is passed. Therefore, even when the amount of power generated by the solar cell 32 decreases due to a change in the power generation conditions, suppression of power generation by the solar cell 32 can be prevented, and the storage battery 12 can be charged by effectively utilizing sunlight.

[0039] As described with reference to FIG. 3 , the amount of power generated by the solar cell 32 tends to decrease as the solar radiation intensity, which is one of the power generation conditions for the solar cell 32, decreases. Therefore, when the solar radiation intensity value is lower than the lower limit of the reference range, the power generation amount of the solar cell 32 decreases, causing the power grid voltage NV to decrease. In such a case, according to the distributed power supply system 1 of the first embodiment, the correspondence is changed to control the converter 14 so that a charging current greater than the charging current that flows when the solar radiation intensity value is within the reference range flows. Therefore, even when the amount of power generated by the solar cell 32 decreases due to a decrease in solar radiation intensity, suppression of power generation by the solar cell 32 can be prevented, and the storage battery 12 can be charged by effectively utilizing sunlight.

[0040] As described with reference to FIG. 4 , among the power generation conditions of the solar cell 32, the higher the temperature of the solar cell 32, the lower the amount of power generated by the solar cell 32 tends to be. Therefore, when the temperature of the solar cell 32 exceeds the upper limit of the reference range, the power generation amount of the solar cell 32 decreases, causing the power grid voltage NV to drop. In such a case, according to the distributed power supply system 1 of the first embodiment, the correspondence is changed to control the converter 14 to flow a charging current that is higher than the charging current that flows when the temperature of the solar cell 32 is within the reference range. This prevents the increase in the temperature of the solar cell 32 from suppressing power generation, thereby enabling the storage battery 12 to be charged by effectively utilizing sunlight.

[0041] Second Embodiment The distributed power supply system of the second embodiment differs from the distributed power supply system 1 of the first embodiment in that, in addition to controlling the charging current based on parameters indicating the power generation conditions of the solar cell 32 and a reference range, the distributed power supply system of the second embodiment controls the charging current based on the power grid voltage NV and a reference voltage.

[0042] In the distributed power system of the second embodiment, the correspondence relationship is also changed when the grid voltage NV is higher than the set voltage Vs and becomes lower than the reference voltage. The reference voltage is set to a voltage that is higher than the set voltage Vs and serves as a reference value indicating that the voltage difference between the grid voltage NV and the set voltage Vs has become sufficiently small. The grid voltage NV may become lower than the reference voltage when the value of a parameter indicating the power generation condition of the solar cell 32 falls outside a reference range, which is a numerical range of the reference power generation condition, and when the value reduces the amount of power generated by the solar cell 32. In addition, the grid voltage NV may become lower than the reference voltage when the amount of DC power supplied to the grid NT from a DC power supply source (the auxiliary device 20 and the third device 60) other than the first device 30 (the solar cell 32) is reduced. When the grid voltage NV is higher than the set voltage Vs and becomes lower than the reference voltage, the main machine control unit 16 controls the converter 14 to flow a charging current greater than the charging current that flows when the grid voltage NV is higher than the reference voltage by changing the correspondence, for example, as shown in FIG. 6 (changing from line segment Ln to line segment Ln1) described above. The charging current that flows when the grid voltage NV is higher than the reference voltage and the larger charging current here refer to the charging currents that flow when the grid voltage NV is the same.

[0043] According to the distributed power supply system of the second embodiment described above, not only when the value of the parameter indicating the power generation condition of the solar cell 32 becomes a value that reduces the amount of power generated by the solar cell 32, but also when the grid voltage becomes lower than the reference voltage, the correspondence is changed to control the converter 14 to flow a charging current that is greater than the charging current that flows when the grid voltage NV is higher than the reference voltage. This prevents the reduction in power generation by the solar cell 32 due to a drop in the grid voltage NV, and allows the storage battery 12 to be charged by effectively utilizing sunlight.

[0044] <Modification of this embodiment> The present invention is not limited to the above-described embodiment, and can be embodied in various forms without departing from the spirit of the invention. For example, the following modifications are also possible.

[0045] [Variation 1] In the above embodiment, the main engine 10 is equipped with the storage battery 12, which is a secondary battery, but this is not limited to this. For example, the main engine 10 may be equipped with an electric double layer capacitor, a capacitor, a flywheel battery, etc. instead of or in addition to the storage battery 12.

[0046] [Variation 2] In the above embodiment, the power supplied from the secondary unit 20 to the power grid NT is derived from power generated using renewable energy, but this is not limited to this. For example, the power supplied from the secondary unit 20 to the power grid NT may be derived from power supplied to the secondary unit 20 from another distributed power generation system.

[0047] [Variation 3] In the above embodiment, the auxiliary machine 20 itself does not have a power supply, and supplies power to the power grid NT using power supplied from an external power supply 80, but this is not limited to this. For example, the auxiliary machine 20 itself may have a power supply, similar to the main machine 10, the first device 30, and the third device 60. In this case, the power supply may be any power supply, such as a storage battery, a solar cell, or a fuel cell. Furthermore, the converter 24 is selected as desired depending on whether the power supplied from the power supply is DC or AC.

[0048] [Variation 4] In the above embodiment, the water electrolysis unit 42 is provided as the generator, but this is not limited thereto. For example, the generator may be a generator that generates alcohol by performing carbon dioxide reduction, or a generator that generates ammonia by reducing nitrogen. In other words, the generator may generate any reactant as long as it generates a reactant using electric power and the power generation unit can generate electric power using the reactant.

[0049] [Variation 5] In the above embodiment, the power generation unit includes the fuel cell 62 that uses hydrogen and oxygen, but this is not limiting. For example, the power generation unit may be a fuel cell that uses alcohol or the like, or a power generation unit that burns chemical substances (hydrogen, alcohol, ammonia, etc.) to rotate a turbine or the like.

[0050] [Variation 6] In the above embodiment, the system includes the equipment control unit 70, the main unit control unit 16, and the auxiliary unit control unit 26, but this is not limited to this. For example, the system may include only the equipment control unit 70, and all of the equipment connected to the power line network NT may be controlled by the equipment control unit 70. Alternatively, each equipment may have its own control unit that controls it individually. Furthermore, the system may include a control unit that simultaneously controls the main unit 10 and the auxiliary unit 20, and a control unit that controls equipment other than the main unit 10 and the auxiliary unit 20.

[0051] [Variation 7] In the above embodiment, the device control unit 70 controls the converter 34 to adjust the output voltage of the solar cell 32 so as to maximize the amount of power generated (output power) by the solar cell 32, but this is not limited to this. The device control unit 70 does not have to adjust the output voltage of the solar cell 32 so as to maximize the amount of power generated (output power) by the solar cell 32.

[0052] [Variation 8] In the above embodiment, the reference range of solar radiation intensity is 1000 to 1200 W / m 2 The reference range for the temperature of the solar cell 32 is 0 to 25°C, but is not limited to this. The upper and lower limits set as the reference range may be any values. Furthermore, the numerical range set as the reference range may be set as narrow as possible.

[0053] [Variation 9] In the above embodiment, the power generation conditions include the solar radiation intensity and the temperature of the solar cell 32, but are not limited to these. Of the parameters indicating the power generation conditions of the solar cell 32, parameters indicating power generation conditions other than the solar radiation intensity and the temperature of the solar cell 32 may be used as the criterion for determining whether to change the correspondence relationship, as long as the parameter tends to reduce the amount of power generated by the solar cell 32 in proportion to an increase or decrease in the value of the parameter.

[0054] [Variation 10] In the above embodiment, the correspondence relationship is changed by lowering the intersection with the vertical axis while maintaining the slope, as shown in the lines Ln and Ln1 in FIG. 7 . However, this is not limiting. For example, the correspondence relationship may be changed by maintaining the intersection with the vertical axis (the set voltage Vs) while making the slope gentler, as shown in the line Ln2 in FIG. 8 . Even in this case, as shown in FIG. 8 , when the voltage of the electric wire network NT is the electric wire network voltage NV, the converter 14 is controlled to flow a charging current CN2 based on the set voltage Vs and the electric wire network voltage NV (NV2) on the line segment Ln2 (corresponding to a charging current greater than the charging current flowing when the parameter value is within the reference range), rather than a charging current Ch based on the set voltage Vs and the electric wire network voltage NV on the line segment Ln (corresponding to a charging current flowing when the parameter value is within the reference range).

[0055] [Variation 11] In the above-described embodiment, as shown by the lines Ln1 and Ln2 in FIGS. 7 and 8, the charging current flowing based on the changed correspondence relationship (lines Ln1 and Ln2) was greater than the charging current flowing based on the previous correspondence relationship (line segment Ln) for any voltage difference as long as the grid voltage NV was higher than the set voltage Vs. However, this is not limited to this. For example, as shown by the line segment Ln3 in FIG. 9, the charging current flowing based on the changed correspondence relationship (line segment Ln3) may be greater than the charging current flowing based on the previous correspondence relationship (line segment Ln) only within a certain range of voltage differences. For example, referring to FIG. 9, in the range S, when a charging current is flowed based on the same grid voltage NVa (shown in FIG. 9), the charging current flowing based on the changed correspondence relationship (line segment Ln3) is smaller than the charging current flowing based on the previous correspondence relationship (line segment Ln). On the other hand, in range B, when a charging current is passed based on the same power grid voltage NVb (shown in FIG. 9 ), the charging current passed based on the changed correspondence relationship (line segment Ln3) is greater than the charging current passed based on the pre-change correspondence relationship (line segment Ln). In a distributed power system in which the occurrence frequency of voltage differences falling within range B is relatively high and the occurrence frequency of voltage differences falling within range S is relatively low, it is also possible to adopt line segment Ln3 as the changed correspondence relationship. In this way, the changed correspondence relationship that the distributed power system refers to may be any correspondence relationship, as long as, for at least some voltage differences, the charging current passed based on the changed correspondence relationship is greater than the charging current passed based on the pre-change correspondence relationship.

[0056] This aspect has been described above based on embodiments and modifications. However, the above-described embodiments are intended to facilitate understanding of this aspect and are not intended to limit this aspect. This aspect may be modified or improved without departing from the spirit and scope of the claims, and equivalents thereof are included in this aspect. Furthermore, if a technical feature is not described as essential in this specification, it may be deleted as appropriate.

[0057] The present invention can also be realized in the following forms. [Application example 1] A distributed power system, comprising: a storage battery capable of supplying and recovering DC power to the power grid; a current adjusting unit that adjusts a current flowing between the electric wire network and the storage battery to either a charging current recovered from the electric wire network to the storage battery or a discharging current supplied from the storage battery to the electric wire network; a solar cell capable of supplying DC power to the power grid; a current control unit that controls the current adjustment unit by referring to a correspondence relationship between a voltage difference between a set voltage that is set as a voltage of the storage battery and a grid voltage that is a voltage of the grid, and the charging current and the discharging current; When the power grid voltage is higher than the set voltage, and the value of a parameter indicating the power generation conditions of the solar cell is a value that falls outside a reference range, which is a numerical range of the reference power generation conditions, and that reduces the amount of power generation of the solar cell, the current control unit controls the current adjustment unit by changing the correspondence so that the charging current flows that is greater than the charging current that flows when the value of the parameter is within the reference range. [Application example 2] The distributed power supply system according to Application Example 1, The parameter is solar radiation intensity, When the power grid voltage is higher than the set voltage and the value of the solar radiation intensity is smaller than the lower limit of the reference range, the current control unit controls the current adjustment unit by changing the correspondence so that the charging current flows that is larger than the charging current that flows when the value of the solar radiation intensity is within the reference range. [Application example 3] The distributed power supply system according to Application Example 1 or Application Example 2, the parameter is the temperature of the solar cell; When the power grid voltage is higher than the set voltage and the temperature value is greater than an upper limit of the reference range, the current control unit controls the current adjustment unit to change the correspondence so that the charging current flows greater than the charging current that flows when the temperature value is within the reference range. [Application example 4] The distributed power supply system according to any one of Application Examples 1 to 3, and when the power grid voltage is higher than the set voltage and the power grid voltage becomes lower than a reference voltage, the current control unit controls the current adjustment unit by changing the correspondence so that the charging current flows greater than the charging current that flows when the power grid voltage is higher than the reference voltage. [Explanation of symbols]

[0058] 1. Distributed power supply system 10…Main engine 12...Storage battery 14...Converter 16…Main engine control section 20...auxiliary unit 24...Converter 26...Auxiliary machine control unit 30...1st device 32...Solar cell 34...Converter 40…Second device 42...Water electrolysis section 44...Converter 50...Storage section 60...Third device 62…fuel cell 64...Converter 70...Device control unit 80…Power supply 90...Load NT…Wire network

Claims

1. A distributed power system, comprising: a storage battery capable of supplying and recovering DC power to the power grid; a current adjusting unit that adjusts a current flowing between the electric wire network and the storage battery to either a charging current recovered from the electric wire network to the storage battery or a discharging current supplied from the storage battery to the electric wire network; a solar cell capable of supplying DC power to the power grid; a current control unit that controls the current adjustment unit by referring to a correspondence relationship between a voltage difference between a set voltage that is set as a voltage of the storage battery and a grid voltage that is a voltage of the grid, and the charging current and the discharging current; When the power grid voltage is higher than the set voltage, and the value of a parameter indicating the power generation conditions of the solar cell is a value that falls outside a reference range, which is a numerical range of the reference power generation conditions, and that reduces the amount of power generation of the solar cell, the current control unit controls the current adjustment unit by changing the correspondence so that the charging current flows that is greater than the charging current that flows when the value of the parameter is within the reference range.

2. 2. The distributed power supply system according to claim 1, The parameter is solar radiation intensity, When the power grid voltage is higher than the set voltage and the value of the solar radiation intensity is smaller than the lower limit of the reference range, the current control unit controls the current adjustment unit by changing the correspondence so that the charging current flows that is larger than the charging current that flows when the value of the solar radiation intensity is within the reference range.

3. 3. The distributed power supply system according to claim 1 or 2, the parameter is the temperature of the solar cell; When the power grid voltage is higher than the set voltage and the temperature value is greater than an upper limit of the reference range, the current control unit controls the current adjustment unit to change the correspondence so that the charging current flows greater than the charging current that flows when the temperature value is within the reference range.

4. 2. The distributed power supply system according to claim 1, and when the power grid voltage is higher than the set voltage and the power grid voltage becomes lower than a reference voltage, the current control unit controls the current adjustment unit by changing the correspondence so that the charging current flows greater than the charging current that flows when the power grid voltage is higher than the reference voltage.

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