Photovoltaic power generation system, power conversion device and control method for power conversion device

Abstract

To provide a photovoltaic power generation system, a power conversion device, and a control method for the power conversion device that are able to improve the followability of a maximum power point.SOLUTION: A photovoltaic power generation system includes: a solar cell device having a solar cell cluster 101 and a bypass circuit; and a power conversion device 20 that performs MPPT control for changing an operating voltage value of the solar cell device for each predetermined step width so as to increase output power of the solar cell device. The power conversion device 20 changes the predetermined step width to a second step width greater than a first step width, when one of an increase and a decrease in the operating voltage value continues a predetermined number of times while the MPPT control using the first step width as the predetermined step width is being performed.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a solar power generation system, a power conversion device, and a control method for a power conversion device. [Background technology]

[0002] When using solar panels, it is commonly known to perform MPPT (Maximum Power Point Tracking), which tracks the maximum power point at which the output power is maximized as the amount of solar radiation changes from moment to moment. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-153284 A Summary of the Invention [Problem to be solved by the invention]

[0004] Currently, when MPPT control is performed, the operating voltage value is changed in a predetermined step width to search for the maximum power point. However, even though the maximum power point changes as the amount of solar radiation changes, the predetermined step width remains constant. Therefore, if the amount of solar radiation changes after MPPT control is started, the tracking ability of the maximum power point may deteriorate.

[0005] Therefore, an object of the present disclosure is to provide a solar power generation system capable of improving the tracking ability of the maximum power point. [Means for solving the problem]

[0006] A solar power generation system according to a first aspect of the present disclosure includes a solar cell device having a plurality of solar cell clusters connected in series, and a bypass circuit provided for each of the solar cell clusters to electrically bypass a solar cell cluster where partial shading is occurring, and a power conversion device that performs Maximum Power Point Tracking (MPPT) control to change an operating voltage value of the solar cell device in predetermined step widths so as to increase the output power of the solar cell device, wherein when performing the MPPT control using a first step width as the predetermined step width, if either an increase or decrease in the operating voltage value occurs consecutively a predetermined number of times, the power conversion device changes the predetermined step width to a second step width wider than the first step width.

[0007] A power conversion device according to a second aspect of the present disclosure is a power conversion device connected to the output side of a solar cell device having a plurality of solar cell clusters connected in series and a bypass circuit provided for each of the solar cell clusters to electrically bypass a solar cell cluster where partial shading is occurring, and is equipped with a control unit that performs Maximum Power Point Tracking (MPPT) control that changes the operating voltage value of the solar cell device in predetermined step widths so as to increase the output power of the solar cell device, and when performing the MPPT control using a first step width as the predetermined step width, the control unit changes the first step width to a second step width wider than the first step width when either an increase or decrease in the operating voltage value occurs consecutively a predetermined number of times.

[0008] A control method for a power conversion device according to a third aspect of the present disclosure is a control method for a power conversion device connected to an output side of a solar cell device having a plurality of solar cell clusters connected in series and a bypass circuit provided for each of the solar cell clusters to electrically bypass a solar cell cluster where partial shading is occurring, the control method comprising a step of performing Maximum Power Point Tracking (MPPT) control for changing an operating voltage value of the solar cell device at predetermined step widths so as to increase the output power of the solar cell device, the step of performing the MPPT control including changing the first step width to a second step width wider than the first step width when the MPPT control is performed using a first step width as the predetermined step width and one of an increase and a decrease in the operating voltage value occurs consecutively a predetermined number of times. Effect of the Invention

[0009] According to one aspect of the present disclosure, it is possible to provide a solar power generation system, a power conversion device, and a control method for a power conversion device that are capable of improving the tracking ability of a maximum power point. [Brief description of the drawings]

[0010] [Figure 1] 1 is a diagram illustrating an example of the configuration of a solar power generation system according to a first embodiment. [Diagram 2] 2 is a perspective view showing an example of a mode in which the solar cell module of FIG. 1 is mounted on a vehicle as a moving body. [Diagram 3] 3 is a diagram showing an example of a solar cell cluster in a solar cell module installed on each surface of the vehicle in FIG. 2. [Figure 4] 4 is a diagram showing a detailed configuration example of the solar cell module of FIG. 3. [Diagram 5] 2 is a diagram illustrating a detailed configuration example of the power conversion device of FIG. 1. [Figure 6] 2 is a diagram showing an example of a predetermined step width of an operating voltage value in a PV curve of the solar cell module of FIG. 1. [Figure 7]2 is a diagram showing an example of a predetermined step width of an operating voltage value after exceeding a maximum power point in a PV curve of the solar cell module of FIG. 1. FIG. [Figure 8] 1. FIG. 4 is a diagram showing another example of a predetermined step width of an operating voltage value after exceeding a maximum power point in a PV curve of the solar cell module of FIG. [Figure 9] 4 is a flowchart illustrating an operation example of the solar power generation system according to the first embodiment. [Figure 10] 13 is a diagram showing an example of changes in solar radiation, operating voltage value, and current during the same time period in a solar power generation system according to a second embodiment. FIG. [Figure 11] FIG. 11 is a diagram showing an example of a PV curve illustrating an example of MPPT control near a maximum power point according to the second embodiment. [Figure 12] 10 is a flowchart illustrating an example of operation of a solar power generation system according to a second embodiment. [Figure 13] FIG. 11 is a diagram showing an example of an IV curve of a solar cell module according to a third embodiment. [Figure 14] 13 is a flowchart illustrating an example of operation of a solar power generation system according to a third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] A solar power generation system according to an embodiment will be described with reference to the drawings. In the description of the drawings, the same or similar parts are denoted by the same or similar reference numerals.

[0012] (1) First embodiment The first embodiment will be described with reference to FIGS.

[0013] (1.1) Configuration Example 1 is a diagram showing an example of the configuration of a solar power generation system 1 according to a first embodiment. The solar power generation system 1 can be mounted on a mobile object. When the solar power generation system 1 is mounted on the mobile object, power can be supplied from the solar power generation system 1 to the mobile object. As shown in FIG. 1, the solar power generation system 1 includes solar cell modules 10-1 to 10-N (N≧1), power conversion devices 20-1 to 20-N (N≧1), a control unit 30, a battery 40, and a storage unit 50.

[0014] In addition, when any of the solar cell modules 10-1 to 10-N is not particularly limited, each of the solar cell modules 10-1 to 10-N is referred to as a solar cell module 10. Here, in Fig. 1, an example in which the solar power generation system 1 includes N solar cell modules 10 is shown, but the number of the solar cell modules 10 is not particularly limited.

[0015] Furthermore, when any of the power electronics devices 20-1 to 20-N is not particularly limited, each of the power electronics devices 20-1 to 20-N will be referred to as a power electronics device 20.

[0016] In addition, in Fig. 1, solid lines connecting each functional block are shown as power lines for supplying power. In addition, in Fig. 1, dashed lines are shown as signal lines for transmitting control commands or various information, for example, at least one of the operating current value and the operating voltage value of the solar cell module 10. The fact that solid lines are shown as power lines and dashed lines are shown as signal lines also applies to Fig. 5 described later.

[0017] An example of a moving object on which the solar power generation system 1 is mounted will be described later with reference to FIG.

[0018] The solar cell module 10 has solar cell clusters 101-1 to 101-M (M≧2). When any of the solar cell clusters 101-1 to 101-M is not particularly limited, each of the solar cell clusters 101-1 to 101-M is referred to as a solar cell cluster 101. Here, Fig. 1 shows an example in which each solar cell module 10 has M solar cell clusters 101, but the number of solar cell clusters 101 is not particularly limited.

[0019] The solar cell cluster 101 generates DC power from sunlight. A total output power obtained by integrating the DC powers generated by the solar cell clusters 101 is output as the output power of the solar cell module 10. Details of the solar cell cluster 101 will be described later with reference to FIG. 4.

[0020] The solar cell module 10 is electrically connected to the power conversion device 20. Therefore, the output power output from the solar cell module 10 is supplied to the power conversion device 20.

[0021] The power conversion device 20 converts the voltage value of the DC power as the output power output from the solar cell module 10 into a preset voltage value. The DC power whose voltage value has been converted by the power conversion device 20 is supplied to the battery 40. The power conversion device 20 performs MPPT (Maximum Power Point Tracking) control based on the control of the control unit 30. For example, when performing MPPT control by the hill climbing method, the power conversion device 20 changes the operating voltage value by a predetermined step width, checks the increase or decrease in the output power, and always increases or decreases the operating voltage value in the direction that increases the output power, searching for the maximum power point. By such MPPT control, the power generation of the solar cell module 10 can be maximized.

[0022] The battery 40 has a function capable of charging with a direct current supplied from the power conversion device 20. Note that, although Fig. 1 shows an example in which the output power output from the solar cell module 10 is charged to the battery 40 via the power conversion device 20, the present invention is not particularly limited to this. For example, if an air conditioner is installed in a mobile object, the output power output from the solar cell module 10 may be supplied to an electric compressor of the air conditioner. Also, for example, if the mobile object on which the solar power generation system 1 is installed is an electric vehicle, the output power output from the solar cell module 10 may be supplied to an electric motor.

[0023] The control unit 30 is composed of a ROM (Read Only Memory), a RAM (Random Access Memory), a CPU (Central Processing Unit), etc. The control unit 30 has a function of controlling the entire solar power generation system 1. The control unit 30 controls the power conversion device 20 based on various information acquired by the power conversion device 20. The control of the power conversion device 20 by the control unit 30 will be described later with reference to FIG. 9.

[0024] The storage unit 50 is configured with a non-volatile memory. The non-volatile memory is, for example, a hard disk drive (HDD). The non-volatile memory may be, for example, a semiconductor memory such as an SD card or a solid state drive (SSD). The storage unit 50 stores information used for various processes of the solar power generation system 1. The storage unit 50 also stores processing contents that realize various functions of the solar power generation system 1.

[0025] (1.2) Usage example Fig. 2 is a perspective view showing an example of a mode in which the solar cell module 10 of Fig. 1 is mounted on a vehicle as a moving body. In the example of Fig. 2, the front side, roof side, rear side, right side side, and left side side of the vehicle correspond to surface A, surface B, surface C, surface D, and surface E, respectively. Each solar cell module 10 is installed on each of surfaces A to E. Note that Fig. 2 shows an example in which each solar cell module 10 is installed on each of surfaces A to E, but is not particularly limited to this. For example, the solar cell module 10 may be installed only on surface B.

[0026] Fig. 3 is a diagram showing an example of the solar cell cluster 101 in the solar cell module 10 installed on each of the faces A to E of the vehicle in Fig. 2. In the example in Fig. 3, the sizes of the solar cell modules 10-A to 10-E are different depending on the areas of the faces A to E of the vehicle. Note that the size of the solar cell module 10 may be increased as the area of ​​the face increases.

[0027] For example, the solar cell module 10-A includes solar cell clusters A1 to A4. The solar cell clusters A1 to A4 are connected in series. For example, the solar cell module 10-B includes solar cell clusters B1 to B6. The solar cell clusters B1 to B3 are connected in series. The solar cell clusters B4 to B6 are connected in series. The series connection of the solar cell clusters B1 to B3 and the series connection of the solar cell clusters B4 to B6 are connected in parallel. For example, the solar cell module 10-C includes solar cell clusters C1 and C2. The solar cell clusters C1 and C2 are connected in series. For example, the solar cell module 10-D includes solar cell clusters D1 to D3. The solar cell clusters D1 to D3 are connected in series. For example, the solar cell module 10-E includes solar cell clusters E1 to E3. The solar cell clusters E1 to E3 are connected in series.

[0028] In addition, even when the solar cell modules 10-A to 10-E are not particularly distinguished from each other, each of the solar cell modules 10-A to 10-E is referred to as the solar cell module 10. In addition, even when the solar cell clusters A1 to A4, solar cell clusters B1 to B6, solar cell clusters C1 and C2, solar cell clusters D1 to D3, and solar cell clusters E1 to E3 are not particularly distinguished from each other, each of the solar cell clusters A1 to A4, solar cell clusters B1 to B6, solar cell clusters C1 and C2, solar cell clusters D1 to D3, and solar cell clusters E1 to E3 is referred to as the solar cell cluster 101.

[0029] (1.3) Example of the configuration of the solar cell module 10 Next, a detailed configuration example of the solar cell module 10 will be described with reference to Fig. 4. Fig. 4 is a diagram showing a detailed configuration example of the solar cell module 10 of Fig. 3. As shown in Fig. 4, the solar cell module 10 further includes bypass circuits 103-1 to 103-3 in addition to solar cell clusters 101-1 to 101-3.

[0030] In addition, in Fig. 4, even when any of the solar cell clusters 101-1 to 101-3 is not particularly limited, it is referred to as the solar cell cluster 101. Furthermore, when any of the bypass circuits 103-1 to 103-3 is not particularly limited, it is referred to as the bypass circuit 103. Fig. 4 shows an example in which the solar cell module 10 has three bypass circuits 103, but is not particularly limited to this. It is sufficient that the solar cell module 10 has a circuit configuration that can electrically bypass each solar cell cluster 101. In other words, it is sufficient that a circuit that electrically bypasses the solar cell cluster 101 is provided for each solar cell cluster 101.

[0031] Further, the solar cell module 10 is provided with a positive electrode terminal P1 and a negative electrode terminal P2. The positive electrode terminal P1 is connected to the negative electrode terminal P2 of one of the solar cell modules 10 that are connected in series among the solar cell modules 10. The negative electrode terminal P2 is connected to the positive electrode terminal P1 of the other of the solar cell modules 10 that are connected in series among the solar cell modules 10.

[0032] The solar cell clusters 101 are connected in series between a positive terminal P1 and a negative terminal P2. Each solar cell cluster 101 has a plurality of solar cells 111. The solar cell cells 111 are connected in series. Although Fig. 4 shows an example in which each solar cell cluster 101 has 16 solar cells 111, the number of the solar cell cells 111 is not particularly limited to this.

[0033] The solar cell 111 has a function of converting light energy into electrical energy by utilizing the photovoltaic effect. The material of the solar cell 111 is, for example, a silicon semiconductor such as a silicon-based polycrystalline solar cell or a silicon-based single crystal solar cell. In addition, for example, a perovskite solar cell, specifically, an organic-inorganic hybrid material having a perovskite structure may also be used. With this configuration, the solar cell 111 converts the energy of sunlight as light energy into direct current power as electrical energy.

[0034] There is no particular limitation on the material of each solar cell 111. The material of each solar cell 111 may be, for example, a compound semiconductor.

[0035] The bypass circuit 103 is connected in parallel to the solar cell cluster 101. The bypass circuit 103 has a bypass diode BD. The bypass diode BD is a semiconductor element through which a current flows when a forward voltage is applied.

[0036] For example, when all the solar cell clusters 111 in the solar cell cluster 101 are generating power, a voltage rises between the solar cell clusters 101, and a reverse voltage is applied to the bypass diode BD. Therefore, no generated current flows through the bypass diode BD from the other solar cell clusters 101 other than the solar cell cluster 101 connected in parallel to the bypass diode BD. On the other hand, when some of the solar cell clusters 111 included in the solar cell cluster 101 cannot generate power, the solar cell 111 that cannot generate power becomes a resistor. Therefore, the solar cell cluster 101 consumes the generated current from the other solar cell clusters 101. For this reason, a voltage drop occurs in the solar cell cluster 101 including the solar cell cell 111 that cannot generate power. At this time, a forward voltage is applied to the bypass diode BD. Therefore, the generated current flows through the bypass diode BD from the other solar cell clusters 101.

[0037] For example, when the solar cell cluster 101 does not generate power normally, the bypass circuit 103 becomes a circuit that electrically bypasses the abnormal solar cell cluster 101. As a result, the current flowing due to the power generation of the normally generating solar cell cluster 101 electrically bypasses the abnormal solar cell cluster 101.

[0038] Furthermore, when any of the solar cell clusters 101 is not generating power normally, the voltage value of the output power of the solar cell module 10 increases, and the current value of the output power of the solar cell module 10 decreases.

[0039] Specifically, when each solar cell cluster 101 is generating power normally, the output voltage output from the solar cell module 10 increases linearly according to the number of solar cell clusters 101. That is, the output power continues to increase until it reaches the maximum power point. On the other hand, when there is a solar cell cluster 101 that is not generating power normally among the solar cell clusters 101, the output voltage output from the solar cell module 10 is as follows. That is, the voltage of the solar cell cluster 101 that is generating power normally increases linearly, and the voltage of the solar cell cluster 101 that is not generating power normally does not increase and maintains an equilibrium state. Therefore, for example, when three solar cell clusters 101 are connected in series and only the middle solar cell cluster 101 of the three solar cell clusters 101 is not generating power normally, the output of the solar cell module 10 is as follows. That is, the voltage increases linearly, remains in an equilibrium state, and then increases linearly again. Also, in the equilibrium state, power is consumed by the solar cell cluster 101 that serves as a resistor. Therefore, the output power increases, then decreases, and then increases again.

[0040] In other words, after passing through the bypass diode BD, the voltage value of the output power of the solar cell module 10 increases, but the current value of the output power of the solar cell module 10 decreases because the solar cell cluster 101 connected in parallel to the bypass diode BD acts as a resistor.

[0041] The configuration including the solar cell cluster 101 and the bypass circuit 103 is called a solar cell device 104.

[0042] The DC power generated by the solar cell module 10 fluctuates according to the intensity of the sunlight. In particular, even on a sunny day with sufficient sunlight intensity, if there is a sudden change in the solar radiation, such as a sudden decrease in the solar radiation due to the movement of clouds, the PV curve and IV curve of the solar cell module 10 will fluctuate. The PV curve of the solar cell module 10 is the power-voltage characteristic curve of the solar cell module 10. The IV curve of the solar cell module 10 is the current-voltage characteristic curve of the solar cell module 10.

[0043] On the premise of the above-mentioned configuration of the solar cell module 10, the power conversion device 20 performs MPPT control. The solar cell module 10 has a maximum power point (local maximum point) on a PV curve that indicates a power value versus an operating voltage value. The power conversion device 20 can operate the solar cell module 10 at the maximum operating point by performing MPPT control.

[0044] One solar cell cluster 101 is made up of a solar cell panel group. A solar cell panel is made up of a plurality of solar cells 111. Therefore, the solar cell cluster 101 may be rephrased as a solar cell panel group.

[0045] (1.4) Configuration example of power conversion device 20 Fig. 5 is a diagram showing a detailed configuration example of the power conversion device 20 of Fig. 1. As shown in Fig. 5, the power conversion device 20 has a coil 210, a capacitor 211, a switching element 212, a diode 213, a capacitor 214, a voltage measurement unit 220, a current measurement unit 221, a voltage measurement unit 222, a communication unit 230, a control unit 231, and a storage unit 232.

[0046] The switching element 212 may have a function of switching between an on state and an off state in response to control by the control unit 231. The switching element 212 may be, for example, a semiconductor element such as an IGBT (Insulated Gate Bipolar Transistor) or a FET (Field Effect Transistor).

[0047] The diode 213 is connected so that a current does not flow back from the output side to the input side of the power conversion device 20. In other words, the anode side of the diode 213 is connected so as to face the input side of the power conversion device 20, and the cathode side of the diode 213 is connected so as to face the output side of the power conversion device 20.

[0048] 5, the power conversion device 20 is provided with input terminals P4 and P5, output terminals P6 and P7, and a connection terminal P8. The input terminals P4 and P5 are connected to the output side of the solar cell module 10. That is, the input terminals P4 and P5 are connected to the positive terminal P1 and the negative terminal P2 of the solar cell module 10, respectively. The output terminals P6 and P7 are connected to the input side of the battery 40. The connection terminal P5 is connected to the control unit 30.

[0049] When switching element 212 is in the on state, coil 210 stores magnetic energy by the current from solar cell module 10. When switching element 212 switches from the on state to the off state, an induced electromotive force is generated in coil 210. As a result, the voltage of the DC power from solar cell module 10 is boosted. The boosted DC power is supplied to the input side of battery 40 via diode 213 for preventing reverse current.

[0050] The capacitor 211 smoothes the voltage of the DC power on the input side of the power conversion device 20. The capacitor 214 smoothes the voltage of the DC power on the output side of the power conversion device 20.

[0051] The voltage measurement unit 220 measures the operating voltage value of the solar cell module 10. The voltage measurement unit 220 supplies the measured operating voltage value to the control unit 231. The current measurement unit 221 measures the operating current value of the solar cell module 10. The current measurement unit 221 supplies the measured operating current value to the control unit 231. The voltage measurement unit 222 measures the voltage value of the boosted DC power. The voltage measurement unit 222 supplies the measured voltage value to the control unit 231.

[0052] The communication unit 230 receives a control signal and the like from the control unit 30. The control signal is, for example, an initialization signal for starting the power conversion device 20. The communication unit 230 functions as a communication device in the present disclosure, and may receive, for example, vehicle speed information indicating the vehicle speed of the vehicle from the vehicle.

[0053] After the power conversion device 20 receives a control signal from the control device 30 and performs a predetermined initialization process to start up, the control device 231 searches for the maximum power point of the solar cell module 10 by MPPT control. For example, when increasing or decreasing the operating voltage value during MPPT control, the control device 231 changes the duty ratio of a pulse signal that alternately switches the switching element 212 between the on state and the off state.

[0054] The power conversion device 20 may be controlled from the outside. For example, the control unit 231 may be provided outside the power conversion device 20. When the control unit 231 is provided outside the power conversion device 20, the control unit 231 may be virtually configured on an external server.

[0055] The storage unit 232 is composed of a non-volatile memory. The non-volatile memory is, for example, a hard disk drive (HDD). The non-volatile memory may be, for example, a semiconductor memory such as an SD card or a solid state drive (SSD). The storage unit 232 stores data obtained by experimentally determining a voltage value based on the number of photovoltaic clusters 101 as an assumed voltage value. Here, the assumed voltage value is a voltage value that may be a peak of power in a curve showing the characteristics of power and voltage in the photovoltaic device 104 when MPPT control is performed. For example, the storage unit 232 stores a value that is set many times as the assumed voltage value when the number of photovoltaic clusters 101 is large. The data of the voltage value stored in the storage unit 232 is read out from the control unit 231, and at least one of the voltage values ​​is set as the assumed voltage value when MPPT control is performed.

[0056] (1.5) Effect of partial shadow Depending on the surrounding environment of the destination of the vehicle equipped with the photovoltaic power generation system 1, partial shading may occur. For example, if an object that blocks sunlight is installed above the place where the vehicle is parked or stopped, partial shading may occur on the solar cell module 10. Such partial shading may also cause the PV curve and IV curve of the solar cell module 10 to change in various ways. For example, if partial shading causes a drop in power generation efficiency due to partial shading of a part of the solar cell cluster 101, the maximum power point on the PV curve may change. In this case, even if the operating voltage is changed by a certain predetermined step width to search for the maximum power point, the maximum power point has changed compared to when the MPPT control was started, so the tracking ability of the maximum power point may be poor.

[0057] Therefore, in the present disclosure, an operation for varying the predetermined step width in MPPT control is performed as follows.

[0058] (1.6) An example of a PV curve Fig. 6 is a diagram showing an example of the predetermined step width of the operating voltage value in the PV curve 301 of the solar cell module of Fig. 1. ΔVm indicates the predetermined step width. The example in Fig. 6 mainly shows the following two points. First, MPPT control is started with a first step width as the predetermined step width. Second, after the operating voltage value increases continuously a predetermined number of times with the first step width, the predetermined step width of the operating voltage value is changed to a second step width wider than the first step width.

[0059] The first step width is, for example, ΔVm=0.25 [V]. The second step width is, for example, ΔVm=1 [V]. The predetermined number of times that serves as a threshold for determining the number of increases in the operating voltage value is, for example, 5 times.

[0060] In other words, the power conversion device 20 performs MPPT control by changing the operating voltage value of the solar cell device 104 by a predetermined step width so as to increase the output power of the solar cell device 104. Specifically, when performing MPPT control using a first step width as the predetermined step width, if the operating voltage value increases a predetermined number of times in succession, the power conversion device 20 changes the predetermined step width to a second step width that is wider than the first step width.

[0061] In FIG. 6, an example is shown in which the predetermined step width is changed to a second step width wider than the first step width when the operating voltage value increases a predetermined number of times, but the present invention is not limited to this example. When the operating voltage value decreases a predetermined number of times, the predetermined step width may be changed to a second step width wider than the first step width. That is, when the power conversion device 20 is performing MPPT control using the first step width as the predetermined step width, if either the increase or decrease in the operating voltage value occurs a predetermined number of times, the power conversion device 20 changes the predetermined step width ΔVm to a second step width wider than the first step width. According to this operation, the second step width can be made wider than the first step width, so that it is possible to shorten the time required to reach the vicinity of the maximum power point. Therefore, it is possible to improve the tracking ability of the maximum power point.

[0062] FIG. 7 is a diagram showing an example of a predetermined step width ΔVm of the operating voltage value after exceeding the maximum power point on the PV curve 302 of the solar cell module 10 in FIG. 1. The maximum power point is a local maximum value on the PV curve 302. Therefore, it is possible to determine that the operating voltage value has exceeded the maximum power point on the PV curve 302 when the output power of the solar cell device 104 changes from an increase to a decrease. FIG. 7 shows an example in which the power conversion device 20 changes the predetermined step width ΔVm to a third step width narrower than the second step width when the output power of the solar cell device 104 changes from an increase to a decrease while performing MPPT control using the second step width. After changing the predetermined step width ΔVm to the third step width, the power conversion device 20 gradually reduces the third step width in the MPPT control. According to this operation, the predetermined step width of the operating voltage value is widened by setting the predetermined step width to the second step width, so that reverse hill climbing can be noticed early, and by changing the predetermined step width from the second step width to the third step width, it is possible to shorten the time required to reach the vicinity of the maximum power point. Furthermore, since the third step width is gradually decreased, the range for searching the maximum power point in the vicinity of the maximum power point in the hill climbing method can be gradually narrowed, so that it is possible to further improve the tracking ability of the maximum power point.

[0063] Here, gradually decreasing the third step width not only means gradually decreasing the third step width by a predetermined step width ΔVm, but also means maintaining the same third step width multiple times and then narrowing the third step width. For example, in the example of Fig. 7, the power conversion device 20 gradually decreases the third step width such as ΔVm = 0.5 [V], 0.2 [V], 0.2 [V], 0.1 [V], 0.1 [V].

[0064] Specifically, the second step width ΔVm=1.0 [V] was set as the predetermined step width, but when the output power of the solar cell device 104 changes from increasing to decreasing, the third step width is set as the predetermined step width. At this time, in the hill climbing method, the direction of moving the operating voltage value is changed from ΔVm to -ΔVm. For example, the third step width including the direction of moving the operating voltage value is -0.5V. Thereafter, when the current output power of the solar cell device 104 is greater than the output power immediately before the current output power, the direction of moving the operating voltage value is maintained. On the other hand, when the current output power of the solar cell device 104 is equal to or less than the output power immediately before the current output power, the direction of moving the operating voltage value is reversed. As a result, as shown in FIG. 7, the third step width including the direction of moving the operating voltage value is changed to -0.2 [V], +0.2 [V], +0.1 [V], -0.1 [V]. By such an operation, the vicinity of the maximum power point on the PV curve 301 is quickly achieved.

[0065] The sum of the absolute values ​​of the third step widths is set to be equal to or greater than the second step width. Specifically, if the threshold for the predetermined number of consecutive occurrences of the operating voltage value is five, the sum of the five third step widths is set to be equal to or greater than the second step width. For example, FIG. 7 shows an example where 0.5+0.2+0.2+0.1+0.1=1.1[V]>1.0[V].

[0066] Fig. 8 is a diagram showing another example of the predetermined step width of the operating voltage value after exceeding the maximum power point in the PV curve of the solar cell module of Fig. 1. Fig. 8 shows an example in which, even if the maximum power point is greatly exceeded by the second step width, the predetermined step width is set to the third step width, making it possible to reach the vicinity of the maximum power point in a short time.

[0067] Specifically, the third step width including the direction in which the operating voltage value is moved is changed to −0.5 [V], −0.2 [V], −0.2 [V], −0.1 [V], and −0.1 [V]. By such an operation, the PV curve 301 can be brought close to the maximum power point.

[0068] (1.7) Operation FIG. 9 is a flowchart illustrating an example of operation of the solar power generation system 1 according to the first embodiment.

[0069] In step S11, the power conversion device 20 starts detecting solar radiation. For example, when sunlight is irradiated onto each solar cell 111, the solar cell 111 converts the solar radiation energy as light energy into DC power as electrical energy. Through such an operation, the solar cell module 10 supplies power to the power conversion device 20. Therefore, the power conversion device 20 can start detecting solar radiation using the power supplied from the solar cell module 10. For example, the power conversion device 20 may start detecting solar radiation on the condition that the power supplied from the solar cell module 10 reaches a power equivalent to a preset amount of solar radiation. Specifically, the power conversion device 20 can start detecting solar radiation based on at least one measurement result of the current measurement unit 221 and the voltage measurement unit 220.

[0070] In step S12, the power conversion device 20 performs a full scan. The power conversion device 20 can identify an operating voltage value at the time of maximum power supplied from the solar cell module 10 by performing a full scan.

[0071] In step S13, the power conversion device 20 determines an operating voltage value when starting MPPT control. For example, the power conversion device 20 sets an operating voltage value at the time of maximum power supplied from the solar cell module 10 by full scan as the operating voltage value when starting the hill-climbing method.

[0072] In step S14, the power conversion device 20 performs MPPT control. For example, the power conversion device 20 changes the operating voltage value by a first step width as a predetermined step width, checks the increase or decrease in the output power of the solar cell module 10, and increases or decreases the operating voltage value in a direction that always increases the output power. At this time, the power conversion device 20 increments a consecutive increase / decrease counter every time the operating voltage value increases. Note that the power conversion device 20 may also increment the consecutive increase / decrease counter every time the operating voltage value decreases. In other words, when performing MPPT control, the power conversion device 20 times whether one of an increase or decrease in the operating voltage value continues a predetermined number of times.

[0073] In step S15, the power conversion device 20 determines whether or not one of the increases and decreases in the operating voltage value has occurred five consecutive times. If the power conversion device 20 determines that one of the increases and decreases in the operating voltage value has occurred five consecutive times, the process of step S15 proceeds to the process of step S16. On the other hand, if the power conversion device 20 determines that one of the increases and decreases in the operating voltage value has not occurred five consecutive times, the process of step S15 returns to the process of step S14. Note that, although an example in which one of the increases and decreases in the operating voltage value has occurred five consecutive times has been described above, the present invention is not particularly limited to this.

[0074] In step S16, the power conversion device 20 changes the predetermined step width to ΔVm=1.0 [V]. Specifically, the power conversion device 20 changes the predetermined step width to ΔVm=1.0 [V] as a second step width that is wider than the first step width.

[0075] In step S17, the power conversion device 20 performs MPPT control. For example, the power conversion device 20 changes the operating voltage value by a second step width as a predetermined step width, checks the increase or decrease in the output power of the solar cell module 10, and increases or decreases the operating voltage in a direction that always increases the output power.

[0076] In step S18, the power conversion device 20 determines whether ΔP<0. If the power conversion device 20 determines that ΔP<0, the process of step S18 proceeds to the process of step S19. Here, ΔP<0 means that the output power of the solar cell device 104 at the current predetermined step width is smaller than the output power of the solar cell device 104 at the predetermined step width immediately before the current predetermined step width. In other words, ΔP<0 means that the output power of the solar cell device 104 has changed from an increase to a decrease. Therefore, the processes of steps S19 to S25 are processes for changing the predetermined step width to the third step width.

[0077] On the other hand, when the power conversion device 20 determines that ΔP is not less than 0, that is, when the power conversion device 20 determines that ΔP is ≧0, the process of step S18 returns to the process of step S17. Here, ΔP ≧0 means that the output power of the solar cell device 104 in the current predetermined step width is equal to or greater than the output power of the solar cell device 104 in the predetermined step width immediately before the current predetermined step width. In other words, ΔP ≧0 means that the output power of the solar cell device 104 is increasing.

[0078] In step S19, the power conversion device 20 changes the predetermined step width to ΔVm=0.5 [V]. Specifically, the power conversion device 20 changes the predetermined step width to ΔVm=0.5 [V] as a third step width narrower than the second step width.

[0079] In step S20, the power conversion device 20 performs MPPT control. For example, the power conversion device 20 changes the operating voltage value by a third step width as a predetermined step width, checks the increase or decrease in the output power of the solar cell module 10, and increases or decreases the operating voltage in a direction that always increases the output power. Specifically, in the example of Figures 7 and 8, the output power increases in the negative direction, so the power conversion device 20 changes the operating voltage value by ΔVm=-0.5 [V].

[0080] In step S21, the power conversion device 20 changes the predetermined step width to ΔVm=0.2 [V]. Specifically, the power conversion device 20 changes the predetermined step width to ΔVm=0.2 [V] as a third step width narrower than the second step width.

[0081] In step S22, the power conversion device 20 performs MPPT control. For example, the power conversion device 20 changes the operating voltage value by a third step width as a predetermined step width, checks the increase or decrease in the output power of the solar cell module 10, and increases or decreases the operating voltage in a direction that always increases the output power. Specifically, in the example of Figures 7 and 8, the direction in which the output power increases is the negative direction, so the power conversion device 20 changes the operating voltage value by ΔVm = -0.2 [V].

[0082] In step S23, the power conversion device 20 changes the predetermined step width to ΔVm=0.2 [V]. Specifically, the power conversion device 20 maintains the predetermined step width at ΔVm=0.2 [V] as a third step width that is narrower than the second step width.

[0083] In step S24, the power conversion device 20 performs MPPT control. For example, the power conversion device 20 changes the operating voltage value by a third step width as a predetermined step width, checks the increase or decrease in the output power of the solar cell module 10, and always increases or decreases the operating voltage in the direction in which the output power increases. Specifically, in the example of Fig. 7, the direction in which the output power increases is the positive direction, so the power conversion device 20 maintains the operating voltage value at ΔVm = 0.2 [V]. On the other hand, in the example of Fig. 8, the direction in which the output power increases is the negative direction, so the power conversion device 20 maintains the operating voltage value at ΔVm = -0.2 [V].

[0084] In step S25, the power conversion device 20 changes the predetermined step width to ΔVm=0.1 [V]. Specifically, the power conversion device 20 changes the predetermined step width to ΔVm=0.1 [V] as a third step width narrower than the second step width.

[0085] In step S26, the power conversion device 20 resets the continuous increase / decrease counter. After that, the process in step S26 returns to the process in step S14.

[0086] Here, in the above description, an example has been described in which a continuous increment / decrement counter is used to count the number of consecutive increments or decrements of the operating voltage value, but the present invention is not limited to this. Any method may be used as long as it can determine that the sum of the absolute values ​​of the third step widths reaches the second step width.

[0087] (1.8) Effects As described above, when the power conversion device 20 performs MPPT control using the first step width as the predetermined step width, if either the increase or decrease in the operating voltage value occurs a predetermined number of times in succession, the power conversion device 20 changes the predetermined step width to a second step width that is wider than the first step width. According to this operation, the second step width can be made wider than the first step width, so that it is possible to shorten the time required to reach the vicinity of the maximum power point. Therefore, it is possible to improve the tracking ability of the maximum power point.

[0088] Furthermore, when the power conversion device 20 according to the first embodiment is performing MPPT control using the second step width and the output power changes from increasing to decreasing, the predetermined step width is changed to a third step width narrower than the second step width. According to this operation, by setting the predetermined step width to the second step width, reverse hill climbing can be noticed early, and by changing the predetermined step width from the second step width to the third step width, the time required to reach the vicinity of the maximum power point can be shortened.

[0089] Moreover, the power conversion device 20 according to the first embodiment gradually reduces the third step width in the MPPT control after changing the predetermined step width to the third step width. According to this operation, since the third step width is gradually reduced, the range in which the maximum power point is searched for in the vicinity of the maximum power point in the hill-climbing method can be gradually narrowed, so that the tracking ability of the maximum power point can be further improved.

[0090] (2) Second embodiment The second embodiment will be described with reference to FIGS.

[0091] (2.1) Differences from the First Embodiment The second embodiment differs from the first embodiment in that a configuration is added for changing an operating voltage value in conjunction with the vehicle speed when performing MPPT control.

[0092] (2.2) Configuration of the Second Embodiment FIG. 10 is a diagram showing an example of changes in solar radiation, operating voltage value, and current during the same time period in a solar power generation system according to the second embodiment. In one example of FIG. 10, the characteristic curve of the amount of solar radiation is shown by a solid line, the voltage of the first pattern is shown by a two-dot chain line, the voltage of the second pattern is shown by a one-dot chain line, and the current is shown by a dashed line. In one example in the range C on the time axis of FIG. 10, when the amount of solar radiation decreases and then recovers, an example is shown in which the current increases even if the operating voltage value is reduced as in the second pattern. Therefore, there is a problem that even if MPPT control is performed in the wrong direction, it may be delayed in determining that it is an error.

[0093] FIG. 11 is a diagram showing an example of a PV curve for explaining an example of MPPT control near the maximum power point according to the second embodiment. In the example of FIG. 11, when the predetermined step width of the operating voltage value is ΔVm, the operating voltage value per step is smaller than ΔVm'. In this case, the change in the operating voltage value becomes like the second pattern of FIG. 10, and the amount of change in the operating voltage value is small, but the current increases even if the operating voltage value decreases, so the power increases. On the other hand, in the example of FIG. 11, when the predetermined step width of the operating voltage value is ΔVm', the operating voltage value per step is larger than ΔVm. In this case, the change in the operating voltage value becomes like the first pattern of FIG. 10, the amount of change in the operating voltage value is large, and the operating voltage value changes from a decrease to an increase, making it possible to follow the change in the amount of solar radiation.

[0094] Therefore, a process of changing ΔVm, which is a predetermined step width of the operating voltage value, according to the vehicle speed is added to the power conversion device 20. The communication unit 230 of the power conversion device 20 receives vehicle speed information indicating the vehicle speed of the vehicle as a communication device. Here, it is assumed that a plurality of vehicle speed ranges are set as a criterion for determining the vehicle speed of the vehicle. In consideration of the setting of such a plurality of vehicle speed ranges, the power conversion device 20 changes the first step width and the second step width for each vehicle speed range according to the vehicle speed of the vehicle indicated in the vehicle speed information. Specifically, when the current vehicle speed belongs to a second vehicle speed range that is slower than the first vehicle speed range, the predetermined step width corresponding to the vehicle speed range is set narrower than the previous predetermined step width. That is, the predetermined step width according to the vehicle speed range is set. More specifically, when the vehicle speed is 0 km or more and less than 5 km, the predetermined step width is set to ΔVm=0.1 [V]. Also, for example, when the vehicle speed is 10 km or more and less than 60 km, the predetermined step width is set to ΔVm=0.5 [V]. Also, for example, when the vehicle speed is 60 km or higher, the predetermined step width is set to ΔVm=1 [V].

[0095] In other words, the predetermined step width is changed when the current vehicle speed range exceeds the immediately preceding vehicle speed range. Specifically, the power conversion device 20 sets at least one of the first step width and the second step width narrower for each vehicle speed range as the vehicle speed is slower. Also, the power conversion device 20 sets at least one of the first step width and the second step width wider for each vehicle speed range as the vehicle speed is faster.

[0096] The above-mentioned first step width and second step width are set on the assumption that the amount of solar radiation changes drastically according to the speed when the vehicle is moving, and changes slowly when the vehicle is stopped. In other words, when the vehicle speed is slow or when the vehicle is stopped, the amount of solar radiation changes slowly and partial shading is likely to occur, so the predetermined step width ΔVm is set to a narrower value than when the vehicle speed is fast. When MPPT control is performed on the assumption set in this way, the predetermined step width of the operating voltage value is fine, so the MPP can be approached more closely, but the overall power generation amount increases. On the other hand, when the vehicle speed is fast, the predetermined step width ΔVm is set to a wider value than when the vehicle speed is slow in order to be able to follow the change in the amount of solar radiation more quickly. When MPPT control is performed on the assumption set in this way, the MPP is reached more quickly, but the predetermined step width of the operating voltage value is coarse, so there is a possibility that the deviation from the MPP is large.

[0097] (2.3) Operation of the Second Embodiment Fig. 12 is a flowchart for explaining an example of the operation of the solar power generation system according to the second embodiment. In the example of Fig. 12, a process is shown in which the predetermined step width is set to any one of a first vehicle speed step width, a second vehicle speed step width, and a third vehicle speed step width depending on the vehicle speed.

[0098] In step S31, the power conversion device 20 acquires vehicle speed information. The vehicle speed information may be acquired, for example, from a vehicle speed signal transferred on a vehicle speed signal line provided in the vehicle.

[0099] In step S32, the power conversion device 20 determines whether the vehicle speed is within a first vehicle speed range. If the power conversion device 20 determines that the vehicle speed is within the first vehicle speed range, the process of step S32 proceeds to step S33. On the other hand, if the power conversion device 20 determines that the vehicle speed is not within the first vehicle speed range, the process of step S32 proceeds to step S34. Here, the first vehicle speed range is, for example, a range in which the vehicle speed is equal to or greater than 0 km and less than 5 km.

[0100] In step S33, the power conversion device 20 sets at least one of the first step width and the second step width to the first vehicle speed step width. After that, the process of step S33 returns to the process of step S31. Here, the first vehicle speed step width is a step width narrower than the second vehicle speed step width and the third vehicle speed step width.

[0101] In step S34, the power conversion device 20 determines whether the vehicle speed is within a second vehicle speed range that is faster than the first vehicle speed range. If the power conversion device 20 determines that the vehicle speed is within the second vehicle speed range that is faster than the first vehicle speed range, the process of step S34 proceeds to the process of step S35. On the other hand, if the power conversion device 20 determines that the vehicle speed is not within the second vehicle speed range that is faster than the first vehicle speed range, the process of step S34 proceeds to the process of step S36. Here, the second vehicle speed range is, for example, a range in which the vehicle speed is equal to or greater than 10 km and less than 60 km.

[0102] In step S35, the power conversion device 20 sets at least one of the first step width and the second step width to the second vehicle speed step width. After that, the process of step S35 returns to the process of step S31. Here, the second vehicle speed step width is a step width that is wider than the first vehicle speed step width and narrower than the third vehicle speed step width.

[0103] In step S36, the power conversion device 20 sets at least one of the first step width and the second step width to the third vehicle speed step width. After that, the process of step S36 returns to the process of step S31. Here, the third vehicle speed step width is a step width wider than the first vehicle speed step width and the second vehicle speed step width.

[0104] (2.4) Effects of the Second Embodiment As described above, in the power conversion device 20 according to the second embodiment, the communication unit 230 as a communication device in the present disclosure receives vehicle speed information indicating the vehicle speed of the vehicle. In addition, the power conversion device 20 according to the second embodiment changes at least one of the first step width and the second step width according to the vehicle speed of the vehicle indicated in the vehicle speed information. According to such an operation, the power conversion device 20 changes at least one of the first step width and the second step width according to the vehicle speed. Therefore, when the vehicle is moving, at least one of the first step width and the second step width can be appropriately changed even if the change in the amount of solar radiation is large. In addition, when the vehicle is stopped, at least one of the first step width and the second step width can be appropriately changed even if the change in the amount of solar radiation is small.

[0105] Furthermore, the slower the vehicle speed is, the narrower the power conversion device 20 sets at least one of the first step width and the second step width. With this operation, even in a situation where the vehicle speed is slow and the amount of solar radiation changes slowly, making it easy for partial shading to occur, at least one of the first step width and the second step width is set narrower, making it possible to search for a maximum power point among multiple power peaks by MPPT control.

[0106] Furthermore, the power conversion device 20 sets at least one of the first step width and the second step width wider as the vehicle speed increases. With this operation, even if the vehicle speed is high and the change in the amount of solar radiation is drastic, it is possible to perform MPPT control that follows the change in the amount of solar radiation more quickly.

[0107] (3) Third embodiment The third embodiment will be described with reference to FIGS.

[0108] (3.1) Differences from the First and Second Embodiments The third embodiment differs from the first and second embodiments in that a configuration for determining an operating voltage value at the start of MPPT control is added as a pre-process before MPPT control.

[0109] (3.2) Configuration of the third embodiment FIG. 13 is a diagram showing an example of an IV curve of the solar cell module 10 according to the third embodiment. In the example of FIG. 13, two current-voltage characteristic curves (hereinafter, IV curves) of the solar cell module 10 are shown. One is a first IV curve when the amount of solar radiation is strong. The other is a second IV curve when the amount of solar radiation is weak. In both the first IV curve and the second IV curve, the operating current value can vary in the range from zero to the short-circuit current. Here, the short-circuit current on the IV curve is the current that flows when the positive electrode terminal P1 and the negative electrode terminal P2 of the solar cell module 10 are short-circuited. During a short circuit, no voltage drop occurs, so the operating voltage value is zero. In addition, the magnitude of the short-circuit current on the IV curve is determined by the intensity of light irradiated to the solar cell module 10 and the area of ​​the solar cell module 10. On the other hand, the operating voltage value on the IV curve can vary in the range from zero to the open voltage. The open voltage on the IV curve is the voltage in an open state without connecting any load or the like between the positive electrode terminal P1 and the negative electrode terminal P2 of the solar cell module 10. Therefore, if no dielectric breakdown occurs at the open circuit voltage on the IV curve, no current flows and the operating current value is 0. The magnitude of the open circuit voltage on the IV curve is determined by the material of the solar cell 111 and the number of solar cell 111 connected in series.

[0110] Here, it is assumed that the amount of solar radiation changes from a weak state to a strong state during a scan to search for an operating voltage value to start MPPT control. In this case, the IV curve changes from the second IV curve to the first IV curve at the timing when the amount of solar radiation changes, and the operating voltage value to start MPPT control, for example, the hill climbing method, becomes a value indicated by a black star. In other words, if there is a fluctuation in solar radiation during scanning, the IV curve becomes discontinuous, and there is a problem that the operating voltage value at the time when the solar radiation is strong is erroneously recognized as the maximum value when the power is at its peak. In order to avoid such a problem of erroneous recognition, if ΔI / ΔV obtained by scanning is, for example, minus 1.0 or less, the default value and the actual measured value Vmax are compared after scanning to distinguish it from the IV curve in partial shade, and the larger one may be set as the operating voltage value to start the hill climbing method. The default value may be determined based on the number of series of the solar cell 111. In the example of FIG. 13, the default value is 25 [V]. Also, when the amount of solar radiation changes from a strong state to a weak state, there is no problem because the default value becomes the operating voltage value to start the hill climbing method.

[0111] (3.3) Operation of the Third Embodiment FIG. 14 is a flowchart illustrating an example of operation of the solar power generation system 1 according to the third embodiment.

[0112] In step S51, the power conversion device 20 starts scanning. The ranges of the operating voltage value and the operating current value to be scanned are as described above with reference to FIG.

[0113] In step S52, the power conversion device 20 determines whether or not the IV curve has become discontinuous. If the power conversion device 20 determines that the IV curve has become discontinuous, the process of step S52 proceeds to step S53. On the other hand, if the power conversion device 20 determines that the IV curve has not become discontinuous, the process of step S52 proceeds to step S54.

[0114] In step S53, the power conversion device 20 sets the operating voltage value at which the hill-climbing method is started to a default value, and ends the process.

[0115] In step S54, the power electronics device 20 determines whether or not the scan is to be completed. If the power electronics device 20 determines that the scan is to be completed, the process of step S54 proceeds to the process of step S55. On the other hand, if the power electronics device 20 determines that the scan is not to be completed, the process of step S54 returns to the process of step S52.

[0116] In step S55, power conversion device 20 sets the operating voltage value at which the hill-climbing method is started to the maximum value when the power is at its peak, and ends the process.

[0117] (3.4) Effects of the Third Embodiment As described above, the power conversion device 20 according to the third embodiment sets the operating voltage value at which MPPT control is started to a default value when the current-voltage characteristic curve showing the characteristics of the current and voltage in the solar cell device 104 becomes discontinuous during a scan to search for the operating voltage value at which MPPT control is started. With this operation, even if the operating voltage value at a time when the insolation is strong is erroneously recognized as the maximum value at the peak of power, it is possible to avoid setting the erroneously recognized maximum value as the operating voltage value at which the hill climbing method is started. This makes it possible to efficiently perform the hill climbing method.

[0118] Furthermore, the power conversion device 20 according to the third embodiment regards a discontinuity as occurring when a current change in the solar cell cluster 101 exceeds a threshold during scanning. This type of operation makes it possible to avoid erroneous recognition of the maximum operating voltage value when power is at its peak due to a sudden increase in solar radiation.

[0119] Furthermore, the power conversion device 20 according to the third embodiment executes a scan again if the current-voltage characteristic curve becomes discontinuous during a scan to search for an operating voltage value at which MPPT control is started. This operation provides an opportunity to scan again even if there is a temporary change in the amount of solar radiation, making it possible to avoid erroneous recognition of the maximum value when the power is at its peak.

[0120] (4) Other embodiments In the above embodiment, an example in which the solar power generation system 1 is mounted on a vehicle as a moving body has been described, but the location in which the solar power generation system 1 is mounted is not particularly limited to this. For example, the solar power generation system 1 may be mounted on a moving body such as a ship, an aircraft, a satellite device, or an air vehicle. By mounting the solar power generation system 1 on a moving body, it becomes possible to supply electric power from the solar power generation system 1 to the moving body.

[0121] In the above embodiment, an example in which the bypass diode BD functions as a circuit that bypasses the solar cell cluster 101 has been described, but the function of the bypass diode BD is not limited thereto. For example, the bypass circuit 103 may have a bypass diode BD connected in parallel to the solar cell cluster 101, and the power conversion device 20 may determine that partial shading has occurred when the bypass diode BD has a temperature higher than a specified temperature. If a current flows through the bypass diode BD, the bypass diode BD generates heat. Therefore, if the heat of the bypass diode BD can be detected, the occurrence of partial shading can be detected based on the heat of the bypass diode BD. According to the above-mentioned feature, the occurrence of partial shading can be detected more reliably. Note that, for example, a temperature sensor such as a resistance temperature detector or a thermistor may be used to detect the heat of the bypass diode BD. In addition, by making it possible to detect the temperature of the bypass diode BD in multiple stages, a failure of the bypass diode BD can also be detected.

[0122] In the above embodiment, as an example of setting at least one of the first step width and the second step width narrower as the vehicle speed is slower, a process example in which the first step width and the second step width are set in a stepped manner, i.e., in stages, is described, but there is no particular limitation on how to set the width narrower. For example, each of the first step width and the second step width may be set to be linearly narrower.

[0123] In the above embodiment, the first step width and the second step width are set to be wider as the vehicle speed increases, i.e., in a stepped manner. However, there is no particular limitation on how the widths are set to be wider. For example, each of the first step width and the second step width may be set to be linearly wider.

[0124] In the above embodiment, an example has been described in which if the current change in the solar cell cluster 101 exceeds a threshold during scanning of the operating voltage value at the start of the hill-climbing method, it is deemed to have become discontinuous, but the power conversion device 20 may execute a scan again. The power conversion device 20 may execute a scan again, and if the IV curve becomes discontinuous, determine that the solar cell device 104 has failed.

[0125] In addition, each of the above-mentioned operation flows is not limited to being performed separately and independently, but can be performed by combining two or more operation flows. For example, some steps of one operation flow may be added to another operation flow, or some steps of one operation flow may be replaced with some steps of another operation flow. In each flow, it is not necessary to perform all steps, and only some steps may be performed.

[0126] Moreover, the above-described embodiments are not limited to being implemented only as the solar power generation system 1. For example, the above-described embodiments may be implemented as a control method for a system such as the solar power generation system 1. Furthermore, for example, the above-described embodiments may be implemented as a program executed by a system such as the solar power generation system 1.

[0127] A program for causing a computer to execute the operations according to the above-described embodiments may be provided. The program may be recorded in a computer-readable medium. The computer-readable medium can be used to install the program in a computer. Here, the computer-readable medium on which the program is recorded may be a non-transient recording medium. The non-transient recording medium is not particularly limited, and may be, for example, a recording medium such as a CD-ROM or a DVD-ROM. In addition, circuits for executing the processes performed by each device according to the above-described embodiments may be integrated, and at least a part of the device may be configured as a semiconductor integrated circuit (chip set, SoC).

[0128] The terms "based on" and "depending on / in response to" used in this disclosure do not mean "based only on" or "depending only on", unless otherwise specified. The term "based on" means both "based only on" and "based at least in part on". Similarly, the term "depending on" means both "based only on" and "depending at least in part on". The terms "include", "comprise", and variations thereof do not mean including only the recited items, but may include only the recited items or may include additional items in addition to the recited items. Additionally, the term "or" used in this disclosure is not intended to be an exclusive or. Additionally, any reference to elements using designations such as "first", "second", etc., used in this disclosure is not intended to generally limit the quantity or order of those elements. These designations may be used herein as a convenient way to distinguish between two or more elements. Thus, a reference to a first and a second element does not imply that only two elements may be employed therein or that the first element must precede the second element in some manner. In this disclosure, where articles are added by translation, such as, for example, a, an, and the in English, these articles are intended to include the plural unless the context clearly indicates otherwise.

[0129] The above describes the embodiments in detail with reference to the drawings, but the specific configuration is not limited to that described above, and various design changes, etc. are possible without departing from the spirit of the invention.

[0130] (5) Additional Notes The following additional features relate to the above-described embodiment.

[0131] (Appendix 1) A plurality of solar cell clusters connected in series; a bypass circuit provided for each of the solar cell clusters to electrically bypass the solar cell cluster where partial shading occurs; a power conversion device that performs MPPT (Maximum Power Point Tracking) control to change an operating voltage value of the solar cell device in predetermined step widths so as to increase an output power of the solar cell device; When the power conversion device is performing the MPPT control using a first step width as the predetermined step width, if one of an increase and a decrease in the operating voltage value occurs a predetermined number of times, the predetermined step width is changed to a second step width that is wider than the first step width. Photovoltaic power generation system.

[0132] (Appendix 2) When the output power changes from increasing to decreasing during the MPPT control using the second step width, the power conversion device changes the predetermined step width to a third step width narrower than the second step width. 2. A solar power generation system as described in appendix 1.

[0133] (Appendix 3) The power conversion device gradually reduces the third step width in the MPPT control after changing the predetermined step width to the third step width. 3. A photovoltaic power generation system as described in appendix 2.

[0134] (Appendix 4) A communication device for receiving vehicle speed information indicating a vehicle speed of the vehicle, The power conversion device changes at least one of the first step size and the second step size in response to a vehicle speed of the vehicle indicated in the vehicle speed information received by the communication device. 2. A solar power generation system as described in appendix 1.

[0135] (Appendix 5) The power conversion device sets at least one of the first step width and the second step width to be narrower as the vehicle speed of the vehicle is slower. 5. A photovoltaic power generation system as described in appendix 4.

[0136] (Appendix 6) The power conversion device sets at least one of the first step width and the second step width to be wider as the vehicle speed of the vehicle increases. 5. A photovoltaic power generation system as described in appendix 4.

[0137] (Appendix 7) When a current-voltage characteristic curve showing characteristics of current and voltage in the solar cell device becomes discontinuous during a scan to search for the operating voltage value at which the MPPT control is started, the power conversion device sets the operating voltage value at which the MPPT control is started to a default value. 2. A solar power generation system as described in appendix 1.

[0138] (Appendix 8) The power conversion device determines that the discontinuity has occurred when a change in current of the solar cell cluster exceeds a threshold during the scan. 8. The solar power generation system according to claim 7.

[0139] (Appendix 9) When a curve showing the characteristics of power and voltage in the solar cell device becomes discontinuous during a scan to search for the operating voltage value at which the MPPT control is started, the power conversion device executes the scan again. 2. A solar power generation system as described in appendix 1.

[0140] (Appendix 10) The power conversion device executes the scan again, and if the curve becomes discontinuous, determines that the solar cell device is faulty. 10. The solar power generation system according to claim 9.

[0141] (Appendix 11) A plurality of solar cell clusters connected in series; a bypass circuit provided for each of the solar cell clusters, electrically bypassing the solar cell cluster where partial shading occurs; and a control unit that performs MPPT (Maximum Power Point Tracking) control to change an operating voltage value of the solar cell device in predetermined step widths so as to increase an output power of the solar cell device; When the MPPT control is performed using a first step width as the predetermined step width, if one of an increase and a decrease in the operating voltage value occurs a predetermined number of times in succession, the control unit changes the first step width to a second step width that is wider than the first step width. Power conversion equipment.

[0142] (Appendix 12) A plurality of solar cell clusters connected in series; A control method for a power conversion device connected to an output side of a solar cell device having a bypass circuit provided for each solar cell cluster and electrically bypassing a solar cell cluster where partial shading occurs, comprising: performing MPPT (Maximum Power Point Tracking) control to change an operating voltage value of the solar cell device at predetermined step widths so as to increase an output power of the solar cell device; The step of performing the MPPT control includes changing the first step width to a second step width wider than the first step width when one of an increase and a decrease in the operating voltage value occurs a predetermined number of times consecutively while the MPPT control is being performed using a first step width as the predetermined step width. A method for controlling a power conversion device. [Explanation of symbols]

[0143] 1 Photovoltaic power generation system, 10, 10-1, 10-N, 10-A to 10-E Solar cell module, 20, 20-1, 20-N Power conversion device, 30 Control unit, 40 Battery, 50 Memory unit, 101, 101-1, 101-M, A1 to A4, B1 to B6, C1, C2, D1 to D3, E1 to E3 Solar cell cluster, 103, 103-1 to 103-3 Bypass circuit, 104 Solar cell device, 111 Solar cell, 210 Coil, 211, 214 Capacitor, 212 Switching element, 213 Diode, 221 Current measurement unit, 230 Communication unit, 231 Control unit, 232 Memory unit, 301 PV curve, 401, 402 IV curve, A, B, C, D, E surface, BD, BD1 to BD3 Bypass diode, P1 positive terminal, P2 negative terminal, P4, P5 input terminals, P6, P7 output terminals, P8 connection terminal

Claims

1. A plurality of solar cell clusters connected in series; a bypass circuit provided for each of the solar cell clusters to electrically bypass the solar cell cluster where partial shading occurs; a power conversion device that performs MPPT (Maximum Power Point Tracking) control to change an operating voltage value of the solar cell device at predetermined step widths so as to increase an output power of the solar cell device; When the power conversion device is performing the MPPT control using a first step width as the predetermined step width, if one of an increase and a decrease in the operating voltage value occurs a predetermined number of times in succession, the predetermined step width is changed to a second step width that is wider than the first step width. Photovoltaic power generation system.

2. When the output power changes from increasing to decreasing during the MPPT control using the second step width, the power conversion device changes the predetermined step width to a third step width narrower than the second step width. The solar power generation system according to claim 1 .

3. The power conversion device gradually reduces the third step width in the MPPT control after changing the predetermined step width to the third step width. The solar power generation system according to claim 2 .

4. A communication device for receiving vehicle speed information indicating a vehicle speed of the vehicle, The power conversion device changes at least one of the first step size and the second step size in response to a vehicle speed of the vehicle indicated in the vehicle speed information received by the communication device. The solar power generation system according to claim 1 .

5. The power conversion device sets at least one of the first step width and the second step width to be narrower as the vehicle speed of the vehicle is slower. The solar power generation system according to claim 4.

6. The power conversion device sets at least one of the first step width and the second step width to be wider as the vehicle speed of the vehicle increases. The solar power generation system according to claim 4.

7. When a current-voltage characteristic curve showing characteristics of current and voltage in the solar cell device becomes discontinuous during a scan to search for the operating voltage value at which the MPPT control is started, the power conversion device sets the operating voltage value at which the MPPT control is started to a default value. The solar power generation system according to claim 1 .

8. The power conversion device determines that the discontinuity has occurred when a change in current of the solar cell cluster exceeds a threshold during the scan. The solar power generation system according to claim 7.

9. When a curve showing the characteristics of power and voltage in the solar cell device becomes discontinuous during a scan to search for the operating voltage value at which the MPPT control is started, the power conversion device executes the scan again. The solar power generation system according to claim 1 .

10. The power conversion device executes the scan again, and if the curve becomes discontinuous, determines that the solar cell device is faulty. The solar power generation system according to claim 9.

11. A plurality of solar cell clusters connected in series; a bypass circuit provided for each of the solar cell clusters, electrically bypassing the solar cell cluster where partial shading occurs; and a power conversion device connected to an output side of the solar cell device having the bypass circuit, a control unit that performs MPPT (Maximum Power Point Tracking) control to change an operating voltage value of the solar cell device at predetermined step widths so as to increase an output power of the solar cell device; When the MPPT control is performed using a first step width as the predetermined step width, if one of an increase and a decrease in the operating voltage value occurs a predetermined number of times, the control unit changes the first step width to a second step width that is wider than the first step width. Power conversion equipment.

12. A plurality of solar cell clusters connected in series; A method for controlling a power conversion device connected to an output side of a solar cell device having a bypass circuit provided for each solar cell cluster and electrically bypassing a solar cell cluster where partial shading occurs, comprising: A step of performing MPPT (Maximum Power Point Tracking) control for changing an operating voltage value of the solar cell device at predetermined step widths so as to increase an output power of the solar cell device, The step of performing the MPPT control includes changing the first step width to a second step width wider than the first step width when one of an increase and a decrease in the operating voltage value occurs a predetermined number of times in succession while the MPPT control is being performed using a first step width as the predetermined step width. A method for controlling a power conversion device.

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