Power generation system

Abstract

The present invention provides a power generation system that can suppress the decline in power conversion efficiency even when the amount of power generated decreases. [Solution] As shown in Figure 1, the power generation system 1 is generally configured to include a plurality of setting units that set the output power Pout for driving the battery 4 based on the generated power Pin output from the power generation device 3 that converts renewable energy into electrical energy, using different setting methods, and a control unit 20 that selects a setting unit from the plurality of setting units that is suitable for the generated current Iin of the generated power Pin. This power generation system 1 can suppress a decrease in power conversion efficiency even when the amount of power generated decreases.

Description

[[Technical Field]]

[0001] The present invention relates to a power generation system. [[Background Art]]

[0002] As a conventional technique, there is known a power converter for photovoltaic power generation that suppresses the output power of a power converter by an active power control unit when the amount of solar radiation decreases in a state where active power control for controlling the output power of the power converter by the active power control unit is performed (see, for example, Patent Document 1).

[0003] This power converter for photovoltaic power generation can suppress a decrease in the output voltage of a solar panel and continue operation even when the amount of solar radiation decreases while active power control is in operation. [[Prior Art Documents]] [[Patent Documents]]

[0004] [[Patent Document 1]] Japanese Unexamined Patent Application Publication No. 2018-036827 [[Summary of the Invention]] [[Problem to be Solved by the Invention]]

[0005] Conventional power converters for photovoltaic power generation have a problem that when the amount of power generation decreases, the proportion of power consumption of a circuit for power conversion relative to the amount of power generation increases, resulting in a decrease in power conversion efficiency.

[0006] Accordingly, an object of the present invention is to provide a power generation system that can suppress a decrease in power conversion efficiency even when the amount of power generation decreases. [[Means for Solving the Problem]]

[0007] One aspect of the present invention provides a power generation system comprising: a plurality of setting units that set the output power for driving a load based on the generated power output from a power generation device that converts renewable energy into electrical energy, using different setting methods; and a control unit that selects a setting unit from the plurality of setting units that is suitable for the generated current of the generated power. [Effects of the Invention]

[0008] According to the present invention, even if the amount of power generated decreases, the decrease in power conversion efficiency can be suppressed. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is an example of a block diagram of a power generation system according to the first embodiment. [Figure 2] Figure 2(a) shows an example of the power curve and current-voltage curve of a power generation device according to the first embodiment, and Figure 2(b) shows an example of the relationship between current and power conversion efficiency. [Figure 3] Figure 3 is a flowchart showing an example of the operation of the power generation system according to the first embodiment. [Figure 4] Figure 4 is an example of a block diagram of a power generation system according to the second embodiment. [Modes for carrying out the invention]

[0010] (Summary of the embodiment) The power generation system according to this embodiment is generally configured to include a plurality of setting units that set the output power for driving a load based on the generated power output from a power generation device that converts renewable energy into electrical energy, using different setting methods, and a control unit that selects a setting unit from the plurality of setting units that is suitable for the generated current of the generated power.

[0011] This power generation system selects a setting unit suitable for the generated current of the power output from the power generation device. Compared to systems that do not employ this configuration, it can generate appropriate output power according to the generated current and suppress the decrease in power conversion efficiency even when the amount of power generated decreases.

[0012] [First Embodiment] (Overview of Power Generation System 1) Figure 1 is an example of a block diagram of a power generation system according to the first embodiment. Figure 2(a) is a diagram showing an example of the power curve and current-voltage curve of a power generation device according to the first embodiment, and Figure 2(b) is a diagram showing an example of the relationship between current and power conversion efficiency. In Figure 2(a), the vertical axis is current (A) and power (W), and the horizontal axis is voltage (V). In Figure 2(b), the vertical axis is power conversion efficiency (%), and the horizontal axis is current (A). Figure 2(b) shows the first current curve I CU1 , the second current curve I CU2 and the third current curve I CU3 This shows the power conversion efficiency at different power bus voltages, and the first current curve I CU1 , the second current curve I CU2 and the third current curve I CU3 The voltage increases in that order. Note that the power bus voltage is the voltage used when charging battery 4.

[0013] In the figures relating to the embodiments described below, the ratios and shapes of the graphs may differ from the actual ratios and shapes. Also, in Figure 1, the main power and signal flows are indicated by arrows. First, the overview of the power generation system 1 will be described below.

[0014] As shown in Figure 1, the power generation system 1 is generally configured to include a plurality of setting units that set the output power Pout for driving the battery 4 based on the generated power Pin output from the power generation device 3 that converts renewable energy into electrical energy, using different setting methods, and a control unit 20 that selects a setting unit from the plurality of setting units that is suitable for the generated current Iin of the generated power Pin.

[0015] Specifically, as shown in FIG. 1, the plurality of setting units include a first setting unit 24 and a setting unit other than the first setting unit 24. As an example, as shown in FIGS. 2(a) and 2(b), the control unit 20 is configured such that the generated current Iin is equal to a predetermined first current threshold I Th1 which is greater than the first current threshold, the optimum operating point OP on the first current-voltage curve IV1 of the generated power Pin M the first setting unit 24 having a setting method for setting the output power Pout by tracking is selected, and when the generated current Iin is equal to the first current threshold I Th1 when the generated current Iin is equal to or less than the first current threshold, a setting unit other than the first setting unit 24 is selected in accordance with the generated current Iin to set the output power Pout.

[0016] More specifically, the plurality of setting units include, but are not limited to, a second setting unit 25 and a third setting unit 26 as setting units other than the first setting unit 24. The control unit 20 is configured such that a predetermined second current threshold I Th2 is provided, and the generated current Iin is equal to the first current threshold I Th1 or less, and the second current threshold I Th2 which is greater than the second current threshold, the second setting unit 25 is selected, and when the generated current Iin is equal to the second current threshold I Th2 or less, the third setting unit 26 is selected. The second setting unit 25 has a setting method for setting the output power Pout based on a predetermined operating point OP2. The third setting unit 26 is configured such that the output power Pout serves as a battery current I which is a load current of a battery 4 as a load B the third setting unit has a setting method for setting an output current Iout in accordance with the battery current.

[0017] As shown in Figure 1, the power generation system 1 of this embodiment includes a power conditioner 2 having a control unit 20, a voltage measurement unit 21, a current measurement unit 22, a switch unit 23, a first setting unit 24, a second setting unit 25, a third setting unit 26, a charge control unit 27, and a storage unit 28. This power generation system 1 is configured to output output power Pout to the battery 4 via the power conditioner 2, which is obtained by adjusting the generated power Pin generated by the power generation device 3 to an optimal combination of current and voltage. This power conditioner 2 is configured as an IC (Integrated Circuit) chip in which the control unit 20 and other components are integrated.

[0018] The power generation device 3 in this embodiment is, for example, a solar cell, but is not limited to that; any device that converts renewable energy, such as a wind power generator, a tidal power generator, or a geothermal power generator, into electrical energy is acceptable. Furthermore, the power generation device 3 is, for example, a small and highly flexible perovskite solar cell.

[0019] The load in this embodiment is, for example, a battery 4, but is not limited to this. The load may also be, for example, an actuator or a motor.

[0020] (Configuration of Power Conditioner 2) The control unit 20 of the power conditioner 2 is a microcomputer composed of, for example, a CPU (Central Processing Unit) that performs calculations and processing on acquired data according to a stored program, and semiconductor memories such as RAM (Random Access Memory) and ROM (Read Only Memory). The control unit 20 comprehensively controls the power conditioner 2.

[0021] The control unit 20 sets a first current threshold I Th1 and the second current threshold I Th2Based on this, the first setting unit 24 to the third setting unit 26 are switched. In other words, the control unit 20 selects the first setting unit 24 to the third setting unit 26 that are electrically connected to the power generation device 3 and the charging control unit 27 based on the generated power Pin and the generated current Iin.

[0022] First current threshold I Th1 For example, the maximum power point OP, which is the power generation characteristic of power generator 3, is one such example. MB It is determined as one-tenth of the output power Pout and the output current Iout, based on the formula, but is not limited to this.

[0023] Second current threshold I Th2 For example, this is used when the generated power Pin is small, and the battery current I of battery 4 B It is predetermined based on, but is not limited to, the following criteria.

[0024] The control unit 20 performs MPPT control by the first setting unit 24 when the generated power Pin is large, and PWM (Pulse Width Modulation) control by the third setting unit 26 when the generated power Pin is small. Between MPPT (Maximum Power Point Tracking) control and PWM control, it performs MPPC (Maximum Power Point Control) control by the second setting unit 25.

[0025] As an example, the voltage measurement unit 21 measures the generated power Pin, the generated voltage Vin, and the open-circuit voltage V, as shown in Figures 2(a) and 2(b). OC1 , open-circuit voltage V OC2 and open-circuit voltage V OC3 The voltage measurement unit 21 also measures the output voltage Vout of the output power Pout output from the first setting unit 24 to the third setting unit 26.

[0026] As an example, the current measuring unit 22 measures the generated power Pin, the generated current Iin, and the short-circuit current I, as shown in Figures 2(a) and 2(b). SC1 and short-circuit current I SC2The current measurement unit 22 also measures the output power Pout output from the first setting unit 24 to the third setting unit 26, and the output current Iout.

[0027] The switch unit 23 switches the first setting unit 24, the second setting unit 25, and the third setting unit 26, which are electrically connected to the power generator 3 and the charge control unit 27, based on the control signal S of the control unit 20.

[0028] The first setting unit 24 controls the optimal operating point OP using MPPT control. M The calculation is performed. For example, as shown by the solid line in Figure 2(a), the first setting unit 24 sets the operating point OP1 of the first current-voltage curve IV1 corresponding to the peak MP1 of the first power curve P1 based on the generated power Pin to the optimal operating point OP M Let's assume that.

[0029] The first setting unit 24 calculates the optimal operating point OP. M The output power Pout is set based on the first voltage V1 and the first current I1. The first setting unit 24 sets the optimal operating point OP for each update cycle. M Calculate.

[0030] The second setting unit 25 performs MPPC control, which is different from MPPT control. The second setting unit 25 acquires the power generation characteristics of the power generator 3 based on the profile information 280 stored in the storage unit 28.

[0031] Figure 2(a) shows the power generation characteristics of power generator 3, specifically the second power curve P2, the second current-voltage curve IV2, and the open-circuit voltage V. OC2 , short-circuit current I SC1 Peak MP B and maximum power point OP MB The measurements were taken under the following specified conditions. These specified conditions include, for example, an illuminance (radiance) of 1000 W / m². 2The measurement conditions (STC: Standard Test Conditions) were a cell temperature of 25°C and a spectral distribution of AM1.5. Therefore, the power generation characteristics depend on the number of cells in the solar cell, the type of connection (series connection, parallel connection, and connections combining these), etc.

[0032] As an example, the second setting unit 25 sets the peak MP of the second power curve P2 based on the profile information 280, as shown by the dashed line in Figure 2(a). B The maximum power point corresponding to OP MB The output power Pout is set based on a second voltage V2, which is the voltage of the first voltage, and a second current I2 corresponding to the second voltage V2. This second voltage V2 is the maximum power point OP of the generator 3. MB The voltage is a fixed value that does not fluctuate. The second current I2 is the current at the operating point OP2 on the second current-voltage curve IV2, which changes according to the generated power Pin, and therefore fluctuates. The second voltage V2, which is a fixed value, is at the maximum power point OP2. MB It is not limited to the voltage that corresponds to it.

[0033] As a variation, power conditioner 2 has a maximum power point OP. MB In addition to the second setting unit 25 that sets the second voltage V2 to a fixed value, there may be at least one setting unit that performs MPPC control with a voltage other than the second voltage V2 set to a fixed value.

[0034] The third setting unit 26 performs PWM (Pulse Width Modulation) control, which is different from MPPT control and MPPC control. As an example, the third setting unit 26 measures the battery current I of the battery 4 measured by the current measurement unit 22. B Based on this, a third current I3 is determined so that the power conversion efficiency remains constant at around 80%. The third setting unit 26 sets the output power Pout based on the third current I3 and the third voltage V3 corresponding to this third current I3.

[0035] As a variation, the power conditioner 2 may include at least one setting unit that performs PWM control with a different power conversion efficiency than the third setting unit 26.

[0036] In Figure 2(a), as an example, a third power curve P3 and a third current-voltage curve IV3 based on the generated power Pin are shown by dashed lines, and the operating point OP3 corresponding to the third current I3 and third voltage V3 in the third current-voltage curve IV3 is illustrated.

[0037] The charging control unit 27 is electrically connected to the first setting unit 24 to the third setting unit 26. The charging control unit 27 generates the output power Pout set in the first setting unit 24 to the third setting unit 26 by performing conversion control such as DC (Direct Current) to DC conversion to convert the generated power Pin into power or voltage. The charging control unit 27 also controls the charging of the battery 4. The charging control unit 27 may also perform rectification control to rectify the generated power Pin according to the load, and DC to AC conversion control to convert the generated power Pin from DC to AC.

[0038] The storage unit 28 is, for example, a semiconductor memory, but is not limited thereto. This storage unit 28 contains profile information 280 and a first current threshold I Th1 And the second current threshold I Th2 It has.

[0039] (Regarding the switching between the first setting section 24 and the third setting section 26) As an example, as shown in Figure 2(b), the power conversion efficiency has a smaller range of variation when the generated current Iin is sufficiently large, i.e., when the amount of power generated is sufficiently large. Also, as indicated by the arrow in Figure 2(a), when the current is high, the peak of the current-voltage curve shifts towards the higher voltage, as an example, the optimal operating point OP M The calculation of is suitable. Therefore, within this range, the optimal operating point OP is determined by MPPT control. M By calculating and tracking this, a more stable and higher power conversion efficiency can be obtained.

[0040] Furthermore, as shown in Figure 2(b), the power conversion efficiency fluctuates more significantly when the generated current Iin is close to zero compared to other cases. Also, as indicated by the arrow in Figure 2(a), the short-circuit current I SC1 The short-circuit current I SC2 In cases where the voltage drops to this level, for example, it could be due to insufficient power, meaning the power generation is low and the optimal operating point OP is low. M It is not possible to calculate this. Therefore, within this range, a higher power conversion efficiency can be obtained by outputting an output power Pout that results in a power conversion efficiency of approximately 80% using PWM control.

[0041] Furthermore, as shown in Figure 2(b) as an example, power conversion efficiency has an intermediate range where the fluctuation range is not small when the generated current Iin is large, and not large when the generated current Iin is small. As indicated by the arrow in Figure 2(a), when the operating point moves towards higher voltage, as an example, the calculated power consumption becomes larger compared to the amount of power generated, and the optimal operating point OP M It is not suitable for calculation. Therefore, within this range, higher power conversion efficiency can be obtained by outputting an output power Pout based on a fixed voltage using MPPC control.

[0042] The control unit 20 uses the generated current Iin measured by the current measurement unit 22 and a first current threshold I Th1 and the second current threshold I Th2 Based on this, the first setting unit 24 to the third setting unit 26 are switched to switch between MPPT control, MPPC control, and PWM control, thereby obtaining high power conversion efficiency over a wide range of generated current Iin.

[0043] An example of the operation of the power generation system 1 of this embodiment will be described below with reference to the flowchart in Figure 3.

[0044] (operation) The current measuring unit 22 of the power conditioner 2 of the power generation system 1 measures the generated current Iin of the generated power Pin of the power generation device 3 (Step 1).

[0045] The control unit 20 controls the generated current Iin and the first current threshold ITh1 The control unit 20 compares the generated current Iin with the first current threshold I. Th1 If the value is greater than (Step 2: Yes), the control signal S is output to the switch unit 23, electrically connecting the power generator 3 and the first setting unit 24, and MPPT control by the first setting unit 24 is started (Step 3).

[0046] The control unit 20 drives the battery 4 based on the selected control (Step 4) and proceeds to Step 1. The control unit 20 may continuously measure the generated current Iin, or it may measure it according to a predetermined period.

[0047] In step 2, the control unit 20 determines that the generated current Iin is equal to the first current threshold I Th1 The following conditions apply (Step 2: No), and the second current threshold I Th2 If the value is greater than (Step 5: Yes), the control signal S is output to the switch unit 23, electrically connecting the power generator 3 and the second setting unit 25, and MPPC control by the second setting unit 25 is started (Step 6), and the process proceeds to step 4.

[0048] Furthermore, in step 5, the control unit 20 determines that the generated current Iin is equal to the second current threshold I Th2 If the value is smaller (Step 5: No), the control signal S is output to the switch unit 23, electrically connecting the power generator 3 and the third setting unit 26, and PWM control by the third setting unit 26 is started (Step 7), and the process proceeds to Step 4.

[0049] (Effects of the first embodiment) The power generation system 1 according to this embodiment can suppress a decrease in power conversion efficiency even when the amount of power generated decreases. Specifically, since the power generation system 1 selects MPPT control, MPPC control, and PWM control based on the generated power Pin and the generated current Iin, it can suppress a decrease in power conversion efficiency even when the amount of power generated decreases and the generated current Iin changes, compared to when this configuration is not adopted.

[0050] In MPPT control, when the amount of power generated decreases, the proportion of power consumption by power conditioner 2 relative to the amount of power generated increases, thus reducing power generation efficiency. Power generation system 1 switches from MPPT control to MPPC control or PWM control when the amount of power generated decreases, so compared to a configuration that does not employ this, the power consumption of power conditioner 2 is reduced and the overall power generation efficiency is increased.

[0051] Power generation system 1 employs PWM control as a control method that improves charging efficiency in the range where the amount of power generated is small and the fluctuation range of the generated current Iin is large. Therefore, the overall charging efficiency is improved compared to when this configuration is not adopted.

[0052] The power generation system 1 performs MPPC control, which generates output power Pout based on a fixed voltage operating point in a range where the amount of power generated is small. Therefore, unlike MPPT control, which tracks and optimizes the operating point OP, the power generation system 1 performs MPPC control. M This eliminates the step of calculating power consumption, thus reducing overall power consumption.

[0053] In power generation system 1, if the characteristics of the current-voltage curve change depending on the environment, the output power Pout may become very low due to MPPC control. Therefore, switching to PWM control can suppress the decrease in power conversion efficiency.

[0054] The power generation system 1 appropriately selects MPPT control, MPPC control, and PWM control according to changes in power generation, so compared to a configuration that does not employ this system, it can stably obtain a high power conversion efficiency even when there are changes in weather or changes in illumination due to shading by obstacles.

[0055] The power generation system 1 has a generated current Iin and a first current threshold I Th1 and the second current threshold I Th2 By comparing these options and appropriately selecting MPPT control, MPPC control, and PWM control, it generates appropriate output power Pout in response to environmental changes and exhibits higher responsiveness compared to using only MPPT control.

[0056] Since the power generation system 1 uses a perovskite solar cell with a high open-circuit voltage as the power generation device 3, it can control the charging of the battery 4 with good power conversion efficiency not only in MPPT control but also in MPPC control and PWM control, not only in series connection but also in parallel connection.

[0057] [Second Embodiment] The second embodiment differs from the first embodiment in that each setting unit is integrated into an IC.

[0058] Figure 4 is an example of a block diagram of a power generation system according to the second embodiment. Figure 4 shows some of the configurations of power conditioners 2a, 2b, and 2c. In the embodiments described below, parts having the same function and configuration as in the first embodiment will be denoted by the same reference numerals as in the first embodiment, and their descriptions will be omitted.

[0059] The power generation system 1 of this embodiment is equipped with a power conditioner for each setting unit. Specifically, power conditioner 2a is configured to include a first setting unit 24 and at least a charge control unit 27a, similar to power conditioner 2 of the first embodiment. Power conditioner 2b is configured to include a second setting unit 25 and at least a charge control unit 27b. Furthermore, power conditioner 2c is configured to include a third setting unit 26 and at least a charge control unit 27c. Power conditioners 2a to 2c are each integrated into an IC.

[0060] The charging control unit 27a is configured to operate within a voltage, current, and voltage range suitable for MPPT control. The charging control unit 27b is configured to operate within a voltage, current, and voltage range suitable for MPPC control. The charging control unit 27c is configured to operate within a voltage, current, and voltage range suitable for PWM control.

[0061] As an alternative, the setting unit and the charging control unit may not be individually integrated into an IC, but rather the entire unit may be integrated into an IC.

[0062] (Effects of the second embodiment) The power generation system 1 of this embodiment has charge control units 27a to 27c corresponding to the first setting unit 24 to the third setting unit 26. Compared to a configuration that does not employ this setup, it can operate within the respective voltage, current, and voltage ranges, and can suppress malfunctions and errors caused by exceeding the usable range.

[0063] The power generation system 1 according to the above-described embodiments and modifications may, for example, be partially implemented by a computer program, an ASIC (Application Specific Integrated Circuit), and an FPGA (Field Programmable Gate Array), depending on the application.

[0064] Although several embodiments and modifications of the present invention have been described above, these embodiments and modifications are merely examples and do not limit the invention as defined in the claims. These novel embodiments and modifications can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. Furthermore, not all combinations of features described in these embodiments and modifications are necessarily essential for solving the problem of the invention. Moreover, these embodiments and modifications are included in the scope and spirit of the invention, as well as in the invention described in the claims and its equivalents. [Explanation of Symbols]

[0065] 1...Power generation system, 2,2a~2c Power conditioner, 3...Power generation device, 4...Battery, 20...Control unit, 21...Voltage measurement unit, 22...Current measurement unit, 23...Switch unit, 24~26...First setting unit~Third setting unit, 27,27a~27c...Charging control unit, 28...Storage unit, 280...Profile information, I1~I3...First current~Third current, I B ...Battery current, I CU1 ~I CU3 ...the first current curve to the third current curve, ISC1 ,I SC2 ...short circuit current, I Th1 ...the first current threshold, I Th2 ...Second current threshold, IV1~IV3...First current-voltage curve~Third current-voltage curve, Iin...Generated current, Iout...Output current, MP1, MP B ...Peak, OP1~OP3...Operating point, OP M ...Optimal operating point, OP MB ...Maximum power point, P1~P3...First power curve~Third power curve, Pin...Generated power, Pout...Output power, S...Control signal, V1~V3...First voltage~Third voltage, V OC1 ~V OC3 ...Open circuit voltage, Vin...Generated voltage, Vout...Output voltage

Claims

1. Multiple setting units that set the output power for driving a load based on the generated power output from a power generation device that converts renewable energy into electrical energy, using different setting methods, A control unit that selects a setting unit from among the plurality of setting units that is suitable for the power generation current of the generated power, A well-equipped power generation system.

2. The plurality of setting units include a first setting unit and setting units other than the first setting unit. The control unit selects a first setting unit having a setting method for setting the output power in accordance with the optimal operating point on the current-voltage curve of the generated power when the generated current is greater than a predetermined first current threshold, and selects a setting unit other than the first setting unit according to the generated current to set the output power when the generated current is less than or equal to the first current threshold. The power generation system according to claim 1, comprising:

3. The plurality of setting units include a second setting unit and a third setting unit as setting units other than the first setting unit. The control unit has a predetermined second current threshold, and when the generated current is less than or equal to the first current threshold and greater than the second current threshold, it selects the second setting unit, and when the generated current is less than or equal to the second current threshold, it selects the third setting unit. The second setting unit has a setting method for setting the output power based on a predetermined operating point, The third setting unit has a setting method for setting the output power to have an output current corresponding to the load current of the load. The power generation system according to claim 2.

Images