Power generation system

Abstract

The present invention provides a power generation system that can suppress the increase in the heat load of power conversion equipment, which has a high heat load. [Solution] The power generation system 1 comprises multiple solar panels 10 and multiple power converters 20 that supply power from the solar panels 10 to a battery 70. The power generation system 1 further comprises a control device 60 that controls the power supply by the multiple power converters 20. When the power supplied to the battery 70 is reduced, the control device 60 performs an adjustment process which makes the rate of reduction in output power of power converters 20 with a high thermal load greater than the rate of reduction in output power of power converters 20 with a low thermal load.

Description

Technical Field

[0001] This invention relates to a power generation system.

Background Art

[0002] Patent Document 1 discloses a power generation system that supplies power generated by a solar panel to a battery.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a power generation system, a plurality of solar panels may be used in combination. Such a power generation system includes a plurality of power conversion devices that supply the power of each of the plurality of solar panels to a battery.

[0005] The heat load generated in the power conversion device when converting voltage is different for each power conversion device. When the heat load of the power conversion device becomes excessive, the operation of the power conversion device may be restricted or the durability performance of the power conversion device may decrease.

Means for Solving the Problems

[0006] The power generation system for solving the above problems includes a plurality of solar panels and a plurality of power conversion devices that supply the power of the solar panels to a battery respectively. The power generation system further includes a control device that controls the power supply by the plurality of power conversion devices. When reducing the power supplied to the battery, the control device executes an adjustment process, which is a process of making the reduction rate of the output power of the power conversion device with a large heat load larger than the reduction rate of the output power of the power conversion device with a small heat load. [Effects of the Invention]

[0007] The above power generation system can suppress the increase in the heat load of the power conversion device, which has a high heat load. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic diagram of the power generation system according to the embodiment. [Figure 2] Figure 2 is a flowchart showing the processing performed by the control device shown in Figure 1. [Modes for carrying out the invention]

[0009] <Embodiment> The following describes an embodiment of the power generation system with reference to Figures 1 and 2. <Overall Structure> The power generation system 1 shown in Figure 1 is mounted on a vehicle 100, for example. The power generation system 1 comprises multiple solar panels 10 and multiple power converters 20. The power generation system 1 further comprises a control device 60.

[0010] The solar panel 10 is constructed by arranging multiple solar cells that generate electricity from sunlight in a panel-like configuration. Examples of locations for installing multiple solar panels 10 on the vehicle 100 include the front of the roof, the rear of the roof, the engine roof, and the back door.

[0011] The power converter 20 supplies power generated by the solar panel 10 to the battery 70. The battery 70 is a secondary battery. The battery 70 stores the power supplied from the power converter 20. The battery 70 includes, for example, an auxiliary battery and at least one drive battery. The auxiliary battery supplies power to, for example, the auxiliary system installed in the vehicle 100. The auxiliary system of the vehicle 100 consists of one or more auxiliary devices. The auxiliary devices are, for example, an electric oil pump, a navigation system, and lighting. The drive battery supplies power to the drive system installed in the vehicle 100. The drive system of the vehicle 100 includes one or more motors for driving the vehicle 100. A relay circuit (not shown) is provided between the power converter 20 and the battery 70.

[0012] The power converter 20 steps down or steps up the DC voltage and outputs it. The power converter 20 is, for example, a DC-DC converter. The power converter 20 is connected to the solar panel 10. The power converter 20 converts the output voltage of the solar panel 10, which is the input voltage, into a voltage based on the instructions of the control device 60 and then outputs it. The type of power converter 20 may be set according to the type of battery 70.

[0013] Each of the multiple power converters 20 has a different configuration, including its electrical circuit and the amount of power it converts. The configuration of each of the multiple power converters 20 is determined, for example, by the installation location of the power converter 20 in the vehicle 100. For example, if the installation location of the power converter 20 is narrow, the circuit board of the power converter 20 will be smaller than that of a power converter 20 with a wider installation location.

[0014] The power generated by one solar panel 10 is supplied to the battery 70 via one power converter 20. For example, the multiple solar panels 10 include a first panel 11, a second panel 12, and a third panel 13. The multiple power converters 20 include a first device 21, a second device 22, and a third device 23. The first device 21 supplies the power generated by the first panel 11 to the battery 70. The second device 22 supplies the power generated by the second panel 12 to the battery 70. The third device 23 supplies the power generated by the third panel 13 to the battery 70. As a result, the battery 70 is supplied with the total output power of the multiple power converters 20.

[0015] The power generation system 1 further includes a measurement circuit 50. The measurement circuit 50 detects information regarding the status of each of the multiple power converters 20 and outputs this information to the control device 60. Examples of the information detected by the measurement circuit 50 are given below.

[0016] The information detected by the measurement circuit 50 is, for example, the current and voltage of the power converter 20. The current of the power converter 20 includes the input current to the power converter 20 and the output current of the power converter 20. The voltage of the power converter 20 includes the input voltage to the power converter 20 and the output voltage of the power converter 20.

[0017] The information detected by the measurement circuit 50 is, for example, the circuit temperature of the electrical circuit included in the power converter 20. The measurement circuit 50 is, for example, a temperature sensor that measures the circuit temperature of the power converter 20. The measurement circuit 50 may also measure, for example, the temperature around the power converter 20. If the temperature around the power converter 20 is high, the heat dissipated by the power converter 20 is large.

[0018] The information detected by the measurement circuit 50 is, for example, the operating status of the power converter 20. When the power converter 20 is operating, the measurement circuit 50 outputs to the control device 60 that the power converter 20 is operating. The measurement circuit 50 determines the operating status of the power converter 20 based on, for example, the output power of the power converter 20.

[0019] The control device 60 includes a CPU 61 and a memory 62. The memory 62 stores in advance various programs in which the processes to be executed by the CPU 61 are described. The CPU 61 controls a plurality of power conversion devices 20 by executing the programs stored in the memory 62.

[0020] The control device 60 controls the power supply by the plurality of power conversion devices 20. For example, when there is a start request, the control device 60 causes the power supply by the plurality of power conversion devices 20 to start. Also, for example, when there is an end request, the control device 60 causes the power supply by the plurality of power conversion devices 20 to end. The start request and the end request are, for example, signals output from the ECU of the vehicle 100. The control device 60 may be included in the ECU of the vehicle 100.

[0021] For example, the control device 60 controls the output power of each of the plurality of power conversion devices 20 by outputting an instruction signal regarding the output voltage of the power conversion device 20 to each of the plurality of power conversion devices 20. For example, the control device 60 controls the output voltage of each of the plurality of power conversion devices 20 by referring to the output power of each of the plurality of power conversion devices 20. For example, the control device 60 acquires the output voltage and output current of the power conversion device 20, and calculates the output power of the power conversion device 20 by multiplying these values. For example, the control device 60 calculates the output voltage at which the output power of the power conversion device 20 becomes maximum by using a known hill climbing method.

[0022] For example, when the circuit temperature of the power conversion device 20 is at or above a predetermined temperature, the control device 60 restricts the operation of the power conversion device 20. Specifically, when the circuit temperature of the power conversion device 20 is at or above a predetermined temperature, the control device 60 reduces the output power of the power conversion device 20 or stops the power supply. By restricting the operation of the power conversion device 20 when the circuit temperature of the power conversion device 20 is at or above a predetermined temperature, it is possible to prevent the thermal load of the power conversion device 20 from becoming excessive.

[0023] The control device 60 reduces the power supplied to the battery 70 by reducing the total output power of the multiple power converters 20 when a limiting request is received. The total output power of the multiple power converters 20 is the sum of the output powers of each of the multiple power converters 20. A limiting request is, for example, a signal requesting that the power supply to the battery 70 be limited. A limiting request is output, for example, from the ECU of the vehicle 100. A limiting request is output when the battery 70 is in a state where the acceptance of power by the battery 70 is limited, such as when the battery 70 is fully charged or when the battery 70 is hot. When the control device 60 reduces the power supplied to the battery 70, it controls the multiple power converters 20 so that the total output power of the multiple power converters 20 is less than or equal to the limiting power. The limiting power is determined, for example, based on the amount of power that the battery 70 can accept.

[0024] <Adjustment process by control device> When the control device 60 reduces the power supplied to the battery 70, it controls the rate of reduction in the output power of each of the power converters 20 based on the heat load of each power converter 20. The rate of reduction in output power is (W1-W2) / W1 for each of the power converters 20, where W1 is the output power before the reduction in the power supplied to the battery 70 and W2 is the output power after the reduction in the power supplied to the battery 70. If the output power of the power converters 20 is not reduced, W2 is equal to W1.

[0025] When reducing the power supplied to the battery 70, the control device 60 executes an adjustment process that makes the rate of decrease in the output power of the power conversion device 20 with a large heat load greater than the rate of decrease in the output power of the power conversion device 20 with a small heat load. Specifically, the adjustment process is a process in which when reducing the power supplied to the battery 70, the rate of decrease in the output power of the power conversion device 20 with a large heat load is set to x (0 < x ≤ 1), and the rate of decrease in the output power of the power conversion device 20 with a small heat load is set to y (0 ≤ y < x). The adjustment process is, for example, a process of supplying power by the power conversion device 20 with a small heat load and stopping the power supply by the power conversion device 20 with a large heat load when reducing the power supplied to the battery 70. The control device 60, for example, sets the rate of decrease in the output power of the power conversion device 20 with a small heat load to 0 and the rate of decrease in the output power of the power conversion device 20 with a large heat load to 1. When the total output power of the plurality of power conversion devices 20 does not decrease to the limit power even if the power supply to the power conversion device 20 with the largest heat load is stopped, the control device 60 then stops the power supply to the power conversion device 20 with the next largest heat load. The control device 60 repeats the above process until the total output power of the plurality of power conversion devices 20 becomes less than or equal to the limit power.

[0026] As a method for the control device 60 to determine the magnitude of the heat load of the power conversion device 20, the following first method to third method can be cited. The control device 60 determines the magnitude of the heat load of each of the plurality of power conversion devices 20 by any one of the first method to the third method.

[0027] [First method] In the first method, the control device 60 determines the magnitude of the heat load of each of the multiple power converters 20 based on the power efficiency, which is the magnitude of the output power relative to the magnitude of the input power of each of the multiple power converters 20. The power efficiency is W4 / W3, where W3 is the input power of a predetermined power converter 20 and W4 is the output power of a predetermined power converter 20. The lower the power efficiency, the greater the power loss in the power converter 20. The control device 60 may store the power generation efficiency of each of the multiple power converters 20, or it may calculate the power efficiency based on the input power and output power output from the measurement circuit 50.

[0028] The adjustment process of the first method is a process in which, when reducing the power supplied to the battery 70, the rate of reduction in the output power of the power converter 20 with low power efficiency is made greater than the rate of reduction in the output power of the power converter 20 with high power efficiency.

[0029] [Second method] In the second method, the control device 60 determines the magnitude of the thermal load of each of the multiple power converters 20 based on the circuit temperature of the electrical circuits contained in each of the multiple power converters 20. The control device 60 obtains the temperature of the electrical circuits output from the measurement circuit 50. The control device 60 calculates a larger thermal load as the circuit temperature increases.

[0030] The adjustment process of the second method is a process in which, when reducing the power supplied to the battery 70, the rate of reduction in the output power of the power converter 20 with a high circuit temperature is made greater than the rate of reduction in the output power of the power converter 20 with a low circuit temperature.

[0031] [Third Method] In the third method, the control device 60 determines the magnitude of the heat load of each of the multiple power converters 20 based on the operating frequency of each of the multiple power converters 20. The control device 60 sequentially stores the operating status of the power converters 20 output from the measurement circuit 50 as the operating history of the power converters 20. The operating history of the power converters 20 includes the number of times the power converters 20 supplied power during a predetermined period up to the time when the control device 60 determines the magnitude of the heat load of the power converters 20 by the third method. The start of the predetermined period is, for example, the most recent time when the main switch of the vehicle 100 was turned on. Alternatively, the start of the predetermined period may be the time when the power converters 20 were shipped from the factory. The control device 60 obtains the operating frequency of the power converters 20 based on the operating history of the power converters 20. The control device 60 calculates a larger heat load the higher the operating frequency of the power converters 20.

[0032] The third adjustment method involves reducing the power supplied to the battery 70 by making the rate of reduction in the output power of the power converter 20 that operates frequently greater than the rate of reduction in the output power of the power converter 20 that operates infrequently.

[0033] <Processing by the control device> The processing performed by the control device 60 will be explained with reference to Figure 2. When the power converter 20 is supplying power to the battery 70, the control device 60 executes the processing shown in Figure 2 if there is a limit request.

[0034] In step S11, the control device 60 determines whether the total output power of the multiple power converters 20 is greater than the limit power. If the total output power is greater than the limit power, the control device 60 proceeds to step S12. If the total output power is not greater than the limit power, that is, if the total output power is less than or equal to the limit power, the control device 60 terminates the process shown in Figure 2.

[0035] In step S12, the control device 60 performs an adjustment process and terminates the series of processes shown in Figure 2. Performing the adjustment process reduces the power supplied to the battery 70. While the control device 60 is performing the adjustment process, it continues the adjustment process until there are no more restriction requests.

[0036] <Operation and Effects of This Embodiment> (1) The power converter 20 generates a thermal load when it converts voltage. This thermal load can cause deterioration of solder due to temperature changes, and crack formation due to expansion and contraction of metal parts. The thermal load differs for each power converter 20 depending on factors such as the characteristics of the power converter 20 and the power generated by the solar panel 10. If the thermal load on the power converter 20 becomes excessive, the operation of the power converter 20 may be restricted, or the durability of the power converter 20 may decrease.

[0037] In this regard, when the control device 60 reduces the power supplied to the battery 70, it performs an adjustment process to make the rate of reduction in the output power of the power converter 20 with a high thermal load greater than the rate of reduction in the output power of the power converter 20 with a low thermal load. With this configuration, since the rate of reduction in the output power of the power converter 20 with a high thermal load is greater than the rate of reduction in the output power of the power converter 20 with a low thermal load, the temperature of the power converter 20 with a high thermal load is less likely to rise. Therefore, it is possible to suppress the increase in the thermal load of the power converter 20 with a high thermal load.

[0038] (2) The control device 60 restricts the operation of the power converter 20 when, for example, the circuit temperature of the power converter 20 is above a predetermined temperature. In the power generation system 1, the adjustment process suppresses the circuit temperature of the power converter 20 from rising, so the restriction of the operation of the power converter 20 due to the circuit temperature of the power converter 20 being above a predetermined temperature is unlikely to occur.

[0039] (3) If the power efficiency of the power converter 20 is low, the power loss in the power converter 20 will be large. The lost power is converted into heat. Therefore, the lower the power efficiency, the greater the heat load on the power converter 20. In this regard, when the control device 60 reduces the power supplied to the battery 70, it makes the rate of reduction in the output power of the power converter 20 with low power efficiency greater than the rate of reduction in the output power of the power converter 20 with high power efficiency. With the above configuration, since the rate of reduction in the output power of the power converter 20 with low power efficiency is greater than the rate of reduction in the output power of the power converter 20 with high power efficiency, the power loss in the power converter 20 with low power efficiency tends to be small. As a result, it is possible to suppress the increase in the heat load of the power converter 20 with low power efficiency.

[0040] (4) When the circuit temperature of the power converter 20 is high, the heat load on the power converter 20 increases. In this regard, when the control device 60 reduces the power supplied to the battery 70, it makes the rate of reduction in the output power of the power converter 20 with a high circuit temperature greater than the rate of reduction in the output power of the power converter 20 with a low circuit temperature. As a result, the output power of the power converter 20 with a high circuit temperature is easily suppressed. As a result, it is possible to suppress the increase in the heat load on the power converter 20 with a high circuit temperature.

[0041] Furthermore, if the circuit temperature of the power converter 20 is high, a large amount of heat is discharged from the power converter 20, which may place a thermal load on the components surrounding the power converter 20. With the above configuration, the output power of the power converter 20, which has a high circuit temperature, is easily suppressed, thus reducing the thermal load on the entire power generation system 1.

[0042] (5) When the operating frequency of the power converter 20 increases, cracks are likely to occur in the metal parts due to repeated expansion and contraction of the metal parts caused by temperature changes. In this regard, when the control device 60 reduces the power supplied to the battery 70, it makes the rate of reduction in the output power of the power converter 20 that operates frequently greater than the rate of reduction in the output power of the power converter 20 that operates infrequently. As a result, the output power of the power converter 20 that operates frequently is easily suppressed. Therefore, it is possible to suppress the operating frequency of the power converter 20 that operates frequently from increasing further.

[0043] (6) When the control device 60 reduces the power supplied to the battery 70, it supplies power using the power converter 20 with a low thermal load and stops supplying power using the power converter 20 with a high thermal load. As a result of stopping the power output of the power converter 20 with a high thermal load, the thermal load of the power converter 20 with a high thermal load can be reduced.

[0044] <Example of changes> This embodiment can be implemented with the following modifications. This embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0045] The adjustment process may also involve stopping the power output of the power converter 20 by comparing one of the following with a predetermined threshold when reducing the power supplied to the battery 70: the circuit temperature, power efficiency, and operating frequency of the power converter 20. The threshold is set to a value that can determine that the thermal load of the power converter 20 is high. If the thermal load is based on the circuit temperature of the power converter 20, the threshold is set to a value that can determine that the circuit temperature of the power converter 20 is above a predetermined temperature. When the control device 60 reduces the power supplied to the battery 70, it stops the power output of the power converter 20 whose circuit temperature exceeds the threshold. If the thermal load is based on the power efficiency of the power converter 20, the threshold is set to a value that can determine that the power efficiency of the power converter 20 is low. When the control device 60 reduces the power supplied to the battery 70, it stops the power output of the power converter 20 whose power efficiency is lower than the threshold. If the thermal load is based on the operating frequency of the power converter 20, the threshold is set to a value that can determine that the operating frequency of the power converter 20 is high. When the control device 60 reduces the power supplied to the battery 70, it stops the power output of the power converter 20 whose operating frequency exceeds a threshold.

[0046] The control device 60 may determine the magnitude of the heat load of each of the multiple power converters 20 by combining at least two of the first to third methods. For example, a priority order may be set for the first to third methods. The control device 60 first determines the magnitude of the heat load of each of the multiple power converters 20 using the method with the highest priority. If there is no difference in the magnitude of the heat load of each of the multiple power converters 20 using the method with the highest priority, the control device 60 then determines the magnitude of the heat load of each of the multiple power converters 20 using the method with the second highest priority.

[0047] The operating history of the power converter 20 may include the operating period during which the power converter 20 supplied power within a predetermined period. The longer the operating period of the power converter 20, the more likely it is that a heat load will occur due to the aging deterioration of the power converter 20. The control device 60 acquires the operating period of the power converter 20 based on the operating history of the power converter 20. The control device 60 calculates a heat load that is greater the longer the operating period of the power converter 20. The adjustment process in this modified example is a process in which, when reducing the power supplied to the battery 70, the rate of reduction in output power of the power converter 20 with a long operating period is made greater than the rate of reduction in output power of the power converter 20 with a short operating period. [Explanation of Symbols]

[0048] 1...Power generation system, 10...Solar panel, 20...Power converter, 50...Measurement circuit, 60...Control device, 61...CPU, 62...Memory, 70...Battery, 100...Vehicle.

Claims

1. The system comprises multiple solar panels and multiple power conversion devices that supply power from the solar panels to a battery. A power generation system further comprising a control device for controlling the power supply by a plurality of the aforementioned power conversion devices, When the control device reduces the power supplied to the battery, it performs an adjustment process that makes the rate of reduction in the output power of the power converter with a high thermal load greater than the rate of reduction in the output power of the power converter with a low thermal load. Power generation system.

2. The adjustment process is a process that, when reducing the power supplied to the battery, makes the reduction rate of the power converter with low power efficiency greater than the reduction rate of the power converter with high power efficiency. The power generation system according to claim 1.

3. The adjustment process is a process that, when reducing the power supplied to the battery, makes the reduction rate of the power converter with a high circuit temperature greater than the reduction rate of the power converter with a low circuit temperature. The power generation system according to claim 1.

4. The adjustment process is a process that, when reducing the power supplied to the battery, makes the reduction rate of the power converter with a high operating frequency greater than the reduction rate of the power converter with a low operating frequency. The power generation system according to claim 1.

5. The adjustment process involves reducing the power supplied to the battery by supplying power from the power converter with a low thermal load and stopping the power supply from the power converter with a high thermal load. A power generation system according to any one of claims 1 to 4.

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