Control device and control method

Abstract

To provide a control device and a control method for controlling a power conversion device in consideration of fluctuations in solar radiation.SOLUTION: A control device 1 controls a power conditioner that generates AC power to be supplied to a load on the basis of DC power outputted by a solar power generation device. The control device 1 has a command value determination unit 143 that determines an output command value for controlling power to be generated by the power conditioner on the basis of power received from a power grid and an upper limit determination unit 142 that determines an upper limit value for the output command value on the basis of at least one of solar radiation received by the solar power generation device or output power of the power conditioner. When the determined output command value is less than or equal to an upper limit value, the command value determination unit notifies the power conditioner of the output command value. When the determined output command value is greater than the upper limit value, the command value determination unit notifies the power conditioner of the upper limit value.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a control device and a control method for controlling a power conversion device. [Background technology]

[0002] Conventionally, devices for controlling the power generated by solar cells have been known. Patent Document 1 discloses a power generation control system that avoids reverse power flow by controlling a power conversion device (power conditioner) so that the power generated is equal to or less than an upper limit value determined based on power consumption. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-161777 Summary of the Invention [Problem to be solved by the invention]

[0004] The power output by a power conversion device that converts DC power output by a solar power generation system into AC power fluctuates depending on the amount of solar radiation. Conventional power generation control systems do not take fluctuations in solar radiation into consideration, which has led to the problem that the power conversion device may be controlled based on an inappropriate upper limit value when the amount of solar radiation fluctuates.

[0005] The present invention has been made in consideration of these points, and has an object to enable control of a power conversion device taking into account fluctuations in the amount of solar radiation. [Means for solving the problem]

[0006] A control device of a first aspect of the present invention is a control device that controls a power conversion device that generates AC power to be supplied to a load based on DC power output by a solar power generation device, and has: a command value determination unit that determines an output command value for controlling the power to be generated by the power conversion device based on power received from a power grid; and an upper limit value determination unit that determines an upper limit value for the output command value based on at least one of the amount of solar radiation received by the solar power generation device or the output power of the power conversion device, and the command value determination unit notifies the power conversion device of the output command value if the determined output command value is equal to or less than the upper limit value, and notifies the power conversion device of the upper limit value if the determined output command value is greater than the upper limit value.

[0007] When the upper limit value determination unit determines the upper limit value based on the amount of solar radiation received by the solar power generation device, the upper limit value determination unit may determine the upper limit value based on the relationship between the rated capacity of the power conversion device and the maximum possible output value that the solar power generation device can generate under the current amount of solar radiation.

[0008] When determining the upper limit value based on the output power of the power conversion device, the upper limit value determination unit may determine the upper limit value to be a value obtained by adding a predetermined margin rate to an operation rate, which is the ratio of the current output power of the power conversion device to the rated capacity of the power conversion device.

[0009] The upper limit value determination unit may use the margin rate determined based on a difference between the target value of the received power and an actual measured value of the received power.

[0010] The upper limit value determination unit may reduce the margin rate as the fluctuation in the operation rate of the power electronics device within a predetermined period increases.

[0011] The upper limit value determination unit may use the margin rate corresponding to the current time or weather by referring to data in which the time or weather is associated with the margin rate.

[0012] The upper limit value determination unit may further have a reception unit that receives a selection of a method for determining the upper limit value, and when the reception unit receives a selection of a method using the current amount of solar radiation, the upper limit value determination unit may determine the upper limit value based on the relationship between the rated capacity of the power conversion device and the maximum possible output value that the solar power generation device can generate under the current amount of solar radiation, and when the reception unit does not receive a selection of the method using the current amount of solar radiation, the upper limit value determination unit may determine the upper limit value to a value obtained by adding a predetermined margin to the ratio of the current output power of the power conversion device to the rated capacity of the power conversion device.

[0013] The upper limit value determination unit may determine the upper limit value based on the relationship between the rated capacity of the power conversion device and the maximum possible output value that the solar power generation device can generate under the current solar radiation level, when the magnitude of fluctuation in the amount of solar radiation on the solar power generation device within a specified period is equal to or greater than a specified threshold, and may determine the upper limit value to a value obtained by adding a specified margin rate to the ratio of the current output power of the power conversion device to the rated capacity of the power conversion device, when the magnitude of fluctuation in the amount of solar radiation on the solar power generation device within a specified period is less than the specified threshold.

[0014] The command value determination unit may determine the output command value by referring to response performance data indicating the response performance of the power conversion device so that overshoot and undershoot when the output power of the power conversion device changes are equal to or less than a predetermined amount.

[0015] The command value determination unit may determine whether the output power of the power conversion device will increase or decrease based on the relationship between the actual measured value of the received power and the target value of the received power, and may refer to the response performance data selected based on the determination result from either first response performance data corresponding to the case where the output power increases or second response performance data corresponding to the case where the output power decreases.

[0016] The command value determination unit may determine whether the output power of the power conversion device will increase or decrease based on the amount of change in the received power, and refer to the response performance data selected based on the determination result from either first response performance data corresponding to an increase in the output power or second response performance data corresponding to a decrease in the output power.

[0017] The command value determination unit may use, as the response performance data, first response performance data corresponding to a case where the output power increases when the result of adding a first difference value obtained by subtracting a target value of the received power from the latest actual measurement value of the received power and a second difference value obtained by subtracting a previous actual measurement value of the received power from the latest actual measurement value of the received power, and, as the response performance data, when the result indicates a negative value, second response performance data corresponding to a case where the output power decreases.

[0018] When the power received from the power grid falls below a threshold, the command value determination unit may determine, based on an operating time limit of a relay for preventing power from being output to the power grid, whether to notify the power conversion device of an output command value smaller than the current output command value, or to notify the power conversion device of an instruction to stop output.

[0019] A control method of a second aspect of the present invention includes the steps of: determining, based on power received from a power grid, an output command value for controlling power to be generated in a power conversion device that generates AC power to be supplied to a load based on DC power output by a solar power generation device, executed by a computer; determining an upper limit value for the output command value based on at least one of the amount of solar radiation received by the solar power generation device or the output power of the power conversion device; and notifying the power conversion device of the output command value if the determined output command value is equal to or less than the upper limit value, and notifying the power conversion device of the upper limit value if the determined output command value is greater than the upper limit value. [Effects of the Invention]

[0020] The present invention provides an advantage in that it is possible to control a power conversion device taking into account fluctuations in the amount of solar radiation. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a diagram showing the configuration of a power generation system S. FIG. [Figure 2] FIG. 1 is a diagram illustrating a configuration of a control device 1. [Figure 3] 1 is a flowchart of the overall operation of the control device 1. [Figure 4] 10 is an operational flowchart of UPR processing. [Figure 5] 10 is an operational flowchart of a process for determining an upper limit of an output command value. [Figure 6] 10 is an operational flowchart of a process for calculating an output command value. DETAILED DESCRIPTION OF THE INVENTION

[0022] [Outline of Power Generation System S] 1 is a diagram showing the configuration of a power generation system S. The power generation system S is a system for generating power using solar light. The power generation system S includes a control device 1, a solar power generation device 2, a power conditioner 3, a digital power meter 4, an analog power meter 5, a reverse power relay 6, a circuit breaker 7, an actinometer 8, and a load L.

[0023] The control device 1 is a device that controls each component constituting the power generation system S, and is, for example, a computer having a processor. As an example, the control device 1 is installed in a building in which each component from the photovoltaic power generation device 2 to the load L is installed, but the control device 1 may be installed in a location different from the building. In this case, the control device 1 transmits and receives data to and from the photovoltaic power generation device 2, the power conditioner 3, the digital wattmeter 4, the analog wattmeter 5, and the actinometer 8 via a network.

[0024] The photovoltaic power generation device 2 has a solar cell, and outputs DC power generated by receiving sunlight to the power conditioner 3.

[0025] The power conditioner 3 is a power conversion device that generates AC power to be supplied to the load L based on the DC power output by the solar power generation device 2. The power conditioner 3 changes the magnitude of the AC power to be output (hereinafter referred to as "output power") based on an output command value input from the control device 1. The output command value is, for example, the ratio of the maximum possible output power to the rated power of the power conditioner 3, and is a value between 0 and 100%.

[0026] The digital power meter 4 and the analog power meter 5 measure the power supplied from the power system P to the load L and notify the control device 1 of the measured power value. In this embodiment, the power generation system S has the digital power meter 4 and the analog power meter 5, but the power generation system S may have only one of the digital power meter 4 or the analog power meter 5.

[0027] The reverse power relay 6 is provided between the load L and the power grid P that supplies power to the load L. When the reverse power relay 6 detects that a state has arisen in which a reverse power flow, in which the output power from the power conditioner 3 flows into the power grid P, may occur, the reverse power relay 6 controls the circuit breaker 7 to cut off the path between the power conditioner 3 and the load L. When the reverse power relay 6 detects that a state has arisen in which a reverse power flow, in which the output power from the power conditioner 3 flows into the power grid P, may send an instruction to the power conditioner 3 to stop output. For example, when the power supplied from the power grid P to the load L falls below a predetermined value, the reverse power relay 6 operates to prevent power from being supplied from the power conditioner 3 to the load L. When the reverse power relay 6 operates, it may notify the control device 1 of this.

[0028] The pyranometer 8 measures the amount of solar radiation that indicates the amount of sunlight received by the solar power generation device 2. The pyranometer 8 notifies the control device 1 of solar radiation amount data that indicates the measured amount of solar radiation. Note that if the control device 1 does not use the amount of solar radiation, the power generation system S does not need to include the pyranometer 8.

[0029] The load L is an electrical device that operates based on the output power supplied from the solar power generation device 2 or the commercial power supplied from the power grid P. During the daytime when the solar power generation device 2 is receiving sunlight, the load L operates mainly on the output power supplied from the solar power generation device 2, and during the nighttime when the solar power generation device 2 is not receiving sunlight, the load L operates mainly on the commercial power supplied from the power grid P.

[0030] However, if the output power generated by the photovoltaic power generation device 2 is greater than the power consumed by the load L, surplus power will be generated. As a result, if there is a possibility of reverse power flow occurring, the reverse power relay 6 cuts off the path between the power system P and the load L. When the reverse power relay 6 cuts off the path between the power system P and the load L, manual intervention may be required to restore the circuit breaker 7 that the reverse power relay 6 has cut off or the power conditioner 3 that the reverse power relay 6 has stopped to a state where they can operate normally, and it will take a long time for the power generation system S to return to a normal state. Therefore, the control device 1 operates so that the output command value for the photovoltaic power generation device 2 does not exceed an upper limit value.

[0031] To prevent reverse power flow, it is desirable to keep the upper limit low. However, if the upper limit is set too low, the output power supplied by the power conditioner 3 to the load L will be excessively limited. Therefore, the control device 1 is characterized by determining the upper limit of the output command value based on at least one of the amount of solar radiation received by the solar power generation device 2 and the output power of the power conditioner 3. By changing the upper limit of the output command value in this manner, the control device 1 can control the power conditioner 3 taking fluctuations in the amount of solar radiation into consideration, and can effectively utilize the power generated by the solar power generation device 2 while preventing reverse power flow.

[0032] [Configuration of control device 1] 2 is a diagram showing the configuration of the control device 1. The control device 1 has a communication unit 11, a reception unit 12, a storage unit 13, and a control unit 14. The control unit 14 has a data acquisition unit 141, an upper limit value determination unit 142, and a command value determination unit 143.

[0033] The communication unit 11 is a communication interface for transmitting and receiving various data between the power conditioner 3, the digital power meter 4, the analog power meter 5, and the actinometer 8. The communication unit 11 has a serial communication interface such as a USB (Universal Serial Bus) or an SPI (Serial Peripheral Interface). The communication unit 11 may have an analog-to-digital conversion circuit that receives an analog signal and converts the received analog signal into a digital signal.

[0034] The reception unit 12 is a user interface for receiving operations by an administrator of the control device 1. The reception unit 12 has an operation device such as a display and a touch panel or a switch. The reception unit 12 may be configured to receive setting values ​​transmitted from an external computer (e.g., a smartphone, a tablet, or a personal computer). The reception unit 12 receives, for example, an operation by the administrator to select a method by which the control device 1 determines the upper limit value of the output command value. The reception unit 12 notifies the control unit 14 of the content of the received operation.

[0035] The storage unit 13 has storage media such as a ROM (Read Only Memory) and a RAM (Random Access Memory). The storage unit 13 stores, for example, a program executed by the control unit 14. The storage unit 13 also stores various data used by the control unit 14 to perform various operations. As an example, the storage unit 13 stores data indicating a method by which the control device 1 determines an upper limit value of the output command value received by the reception unit 12. The storage unit 13 may store data indicating the power values ​​input from the digital power meter 4 and the analog power meter 5 as log data in association with time. The storage unit 13 may also store data indicating the characteristics of the power conditioner 3 in advance.

[0036] The control unit 14 has, for example, a CPU (Central Processing Unit). The control unit 14 executes the programs stored in the storage unit 13, thereby functioning as a data acquisition unit 141, an upper limit value determination unit 142, and a command value determination unit 143.

[0037] The data acquiring unit 141 acquires data notified from the power conditioner 3, the digital power meter 4, the analog power meter 5, and the actinometer 8 via the communication unit 11. The data acquiring unit 141 acquires, for example, output power data notified from the power conditioner 3, received power data output by the digital power meter 4 or the analog power meter 5, or solar radiation data output by the actinometer 8, and notifies the acquired output power data, received power data, or solar radiation data to the upper limit value determining unit 142. Note that the data acquiring unit 141 may acquire output power data from a power meter (not shown) that measures the output power of the power conditioner 3.

[0038] The upper limit value determination unit 142 determines the upper limit value of the output command value based on at least one of the amount of solar radiation received by the solar power generation device 2 and the output power of the power conditioner 3. When determining the upper limit value based on the amount of solar radiation received by the solar power generation device, the upper limit value determination unit 142 determines the upper limit value based on the relationship between the rated capacity of the power conditioner 3 and the maximum possible output value that the solar power generation device 2 can generate under the current amount of solar radiation. As an example, the upper limit determination unit 142 calculates the upper limit using the following (Equation 1). Upper limit of output command value = current solar radiation x PV capacity ÷ PCS rated capacity (Equation 1)

[0039] Here, the PV capacity is the rated power value that the photovoltaic power generation device 2 can output. The current amount of solar radiation is the ratio to the amount of solar radiation in a state where the photovoltaic power generation device 2 outputs rated power. The PCS rated capacity is the maximum power value that the power conditioner 3 can output. The upper limit value determination unit 142 determines the upper limit value based on (Equation 1), so that the upper limit value can be made larger when the amount of solar radiation is high than when the amount of solar radiation is low, allowing the power generation system S to effectively utilize the power generated by the photovoltaic power generation device 2.

[0040] When determining the upper limit value based on the output power of the power conditioner 3, the upper limit value determination unit 142 determines the upper limit value to be a value obtained by adding a predetermined margin rate to the ratio of the current output power of the power conditioner 3 to the rated capacity of the power conditioner 3. That is, the upper limit value determination unit 142 calculates the upper limit value using the following (Equation 2). Upper limit of output command value = PCS output ÷ PCS rated capacity + output margin rate (Equation 2) Here, the PCS output is the current output power value of the power conditioner 3, and "PCS output / PCS rated capacity" is the operation rate of the power conditioner 3 (hereinafter referred to as "PCS operation rate").

[0041] In the above (Equation 2), the upper limit value determination unit 142 uses, for example, an output margin rate determined based on the difference between the target value of the received power supplied from the power system P and the actual measured value of the received power. If the target value of the received power is, for example, 100 kW and the current received power is 150 kW, it is considered that no reverse power flow will occur even if the output power of the power conditioner 3 increases by the difference of 50 kW. In this case, the upper limit value determination unit 142 determines the value of the difference with respect to the rated power of the power conditioner 3 (i.e., the difference value divided by the rated power) as the output margin rate. By having the upper limit value determination unit 142 determine the upper limit value based on the output margin rate, it becomes possible to effectively utilize the power generated by the photovoltaic power generation device 2.

[0042] However, if the fluctuation in the operation rate is large, the output power currently generated by the power conditioner 3 is likely to suddenly increase, and therefore if the output margin rate is too large, reverse power flow may occur. Therefore, the upper limit value determination unit 142 may reduce the output margin rate as the fluctuation in the operation rate of the power conditioner 3 within a predetermined period of time becomes larger. The predetermined period of time is, for example, the past one month.

[0043] For example, the upper limit value determination unit 142 determines the output margin rate based on the amount of fluctuation in the operation rate of the power conditioner 3 by referring to a data table that associates the amount of fluctuation in the operation rate of the power conditioner 3 within a predetermined period with the output margin rate. By operating in this manner, the upper limit value determination unit 142 prevents the occurrence of reverse power flow even when the fluctuation in the operation rate of the power conditioner 3 is large, and effectively utilizes the power generated by the photovoltaic power generation device 2 when the fluctuation in the operation rate of the power conditioner 3 is small.

[0044] Furthermore, since the amount of fluctuation in solar radiation varies depending on the season or weather, if the output margin rate during a period or weather with high solar radiation fluctuation is the same as the output margin rate during a period or weather with low solar radiation fluctuation, reverse power flow may occur when the amount of solar radiation is high, or the power generated by the solar power generation device 2 may not be used effectively when the amount of solar radiation fluctuation is low. Therefore, the upper limit value determination unit 142 may use the margin rate corresponding to the current time by referring to data that associates the time or weather with the output margin rate. For example, the upper limit value determination unit 142 may set the output margin rate during a period with high solar radiation fluctuation to be smaller than the output margin rate during a period with low solar radiation fluctuation. The upper limit value determination unit 142 may estimate the magnitude of the amount of fluctuation in solar radiation based on a weather forecast and change the output margin rate based on the estimated result.

[0045] It should be noted that the method by which upper limit value determination unit 142 selects whether to determine the upper limit value based on solar radiation data or based on the output power of photovoltaic power generation device 2 is arbitrary. As an example, upper limit value determination unit 142 determines the upper limit value based on a method specified by the administrator of control device 1, which is input via reception unit 12. When a method for determining the upper limit value is specified via reception unit 12, upper limit value determination unit 142 stores information indicating the specified method in storage unit 13, and when determining the upper limit value, determines the upper limit value using the specified method by referring to the information.

[0046] Specifically, when the receiving unit 12 receives a selection of a method using the current amount of solar radiation, the upper limit value determination unit 142 determines the upper limit value based on the relationship between the rated capacity of the power conditioner 3 and the maximum possible output value that the photovoltaic power generation device 2 can generate under the current amount of solar radiation. On the other hand, when the receiving unit 12 does not receive a selection of a method using the current amount of solar radiation, the upper limit value determination unit 142 determines, as the upper limit value, a value obtained by adding a predetermined margin to the ratio of the current output power of the power conditioner 3 to the rated capacity of the power conditioner 3. By operating the upper limit value determination unit 142 in this manner, even when data transmission and reception between the actinometer 8 and the control device 1 is unstable or when the actinometer 8 breaks down, without the administrator of the control device 1 performing an operation to select a method for determining the upper limit value, the upper limit value determination unit 142 can determine the upper limit value based on the received power.

[0047] The upper limit value determination unit 142 may select a method for determining the upper limit value based on the magnitude of fluctuations in the amount of solar radiation. Specifically, when the magnitude of fluctuations in the amount of solar radiation on the solar power generation device 2 within a predetermined period is equal to or greater than a predetermined threshold, the upper limit value determination unit 142 determines the upper limit value based on the relationship between the rated capacity of the power conditioner 3 and the maximum possible output value that the solar power generation device 2 can generate under the current amount of solar radiation.

[0048] The predetermined threshold is determined, for example, based on the magnitude of the received power at that time, and the greater the received power, the greater the threshold. By setting the threshold in this manner, in a state where the received power is large and reverse power flow is unlikely to occur, the upper limit can be determined using the amount of solar radiation even if the amount of solar radiation fluctuates greatly, so that the power generated by the solar power generation device 2 can be used to the maximum.

[0049] On the other hand, when the magnitude of fluctuations in the amount of solar radiation on the photovoltaic power generation device 2 within a predetermined period is less than a predetermined threshold, the upper limit value determination unit 142 determines, as the upper limit value, a value obtained by adding a predetermined margin rate to the ratio of the current output power of the power conditioner 3 to the rated capacity of the power conditioner 3. By operating in this manner, the upper limit value determination unit 142 takes into consideration the risk of reverse power flow occurring due to an increase in the power output by the power conditioner 3, and therefore the upper limit value determination unit 142 can determine the upper limit value so that reverse power flow does not occur even if the amount of solar radiation fluctuates greatly.

[0050] Next, the operation of the command value determiner 143 will be described. The command value determiner 143 determines an output command value for controlling the power generated by the power conditioner 3 based on the received power from the power grid P. If the rate of change of the output command value does not match the response performance of the power conditioner 3, the power conditioner 3 will not be able to make the change in output power follow the change in the output command value. Therefore, the command value determiner 143 changes the output command value at a rate based on the response performance of the power conditioner 3. If the determined output command value is equal to or less than an upper limit value, the command value determiner 143 notifies the power conditioner 3 of the output command value, and if the determined output command value is greater than the upper limit value, the command value determiner 143 notifies the power conditioner 3 of the upper limit value. By operating in this manner, the command value determiner 143 can prevent reverse power flow from occurring.

[0051] Incidentally, there is a delay time between when the command value determination unit 143 notifies the power conditioner 3 of the output command value and when the output power of the power conditioner 3 changes. Therefore, if the command value determination unit 143 notifies the power conditioner 3 of an instruction to increase the output command value without considering the delay time, the output power will become too large if the delay time is long, causing a reverse power flow. On the other hand, if the operation of the power conditioner 3 is stopped even though the delay time is short, the power that could have been generated by the solar power generation device 2 will not be effectively utilized.

[0052] Therefore, the command value determination unit 143 may determine whether to notify the power conditioner 3 of an output command value smaller than the current output command value or to notify the power conditioner 3 of an instruction to stop output, based on the operation time limit of the reverse power relay 6, which is a relay for preventing power from being output to the power system P when the received power from the power system P becomes equal to or smaller than a threshold value. When the operation time limit is equal to or smaller than the time threshold, the command value determination unit 143 notifies the power conditioner 3 of an instruction to stop output, and when the operation time limit is greater than the time threshold, notifies the power conditioner 3 of an output command value smaller than the current output command value.

[0053] The time threshold is determined, for example, based on the maximum rate of change of the output power of the power conditioner 3 (i.e., the maximum amount of power increase per unit time), and is set so that the greater the maximum rate of change of the output power, the shorter the time threshold, but it may also be set by an administrator of the control device 1. Since the command value determination unit 143 determines the control method for the power conditioner 3 based on the operation time limit of the reverse power relay 6 in this way, it is not necessary to use a different control device 1 for each specification of the reverse power relay 6 used in the power generation system S, and therefore even if the reverse power relay 6 is changed, the occurrence of reverse power flow can be suppressed without changing the control device 1.

[0054] Furthermore, the response performance of the inverter 3 when increasing the output power of the inverter 3 differs from the response performance of the inverter 3 when decreasing the output power of the inverter 3. Therefore, if the processing when increasing and decreasing the output of the inverter 3 were the same, it would be easy for the rate of change of the output command value to not match the response performance of the inverter 3. As a result, the inverter 3 would not be able to change the output power in response to changes in the output command value, and overshoot or undershoot would easily occur in the output power of the inverter 3.

[0055] Therefore, the command value determiner 143 may determine an output command value such that overshoot and undershoot when the output power of the power conditioner 3 changes are equal to or less than a predetermined amount by referring to response performance data indicating the response performance of the power conditioner 3. Specifically, the command value determiner 143 may determine whether the output power of the power conditioner 3 needs to be increased or decreased, and calculate the output command value based on the response performance of the power conditioner 3 corresponding to the determination result.

[0056] As an example, the command value determiner 143 determines whether the output power of the power conditioner 3 should increase or decrease based on the relationship between the actual measured value of the received power and the target value of the received power. The relationship between the actual measured value of the received power and the target value of the received power is represented, for example, by a value (P1) obtained by subtracting the target value of the received power from the actual measured value of the received power. If this value is positive, the command value determiner 143 determines to increase the output power of the power conditioner 3, and if this value is negative, the command value determiner 143 determines to decrease the output power of the power conditioner 3.

[0057] The command value determiner 143 determines the output command value by referring to the response performance data selected based on the determination result from either the first response performance data corresponding to an increase in output power or the second response performance data corresponding to a decrease in output power. That is, the command value determiner 143 determines the output command value by referring to the first response performance data when it determines to increase the output power, and by referring to the second response performance data when it determines to decrease the output power.

[0058] The command value determination unit 143 may determine whether the output power of the power conditioner 3 will increase or decrease based on the amount of change in the received power. Then, the command value determination unit 143 may refer to the response performance data selected based on the determination result from either the first response performance data corresponding to the case where the output power increases or the second response performance data corresponding to the case where the output power decreases.

[0059] Specifically, the command value determination unit 143 determines that the output power of the power conditioner 3 is increasing when the value (P2) obtained by subtracting the previously acquired received power from the latest received power is a positive value, and determines that the output power of the power conditioner 3 is decreasing when the value is negative. When the command value determination unit 143 determines that the power conditioner 3 is increasing the output power, it refers to the first response performance data, and when it determines that the power conditioner 3 is decreasing the output power, it refers to the second response performance data to determine the output command value.

[0060] The command value determination unit 143 may use both a difference value (P1) between the actual measurement value of the received power and the target value of the received power and a change amount (P2) of the received power to determine whether the output power of the power conditioner 3 will increase or decrease. Specifically, if the result of adding a first difference value (P1) obtained by subtracting the target value of the received power from the latest actual measurement value of the received power and a second difference value (P2) obtained by subtracting the previous actual measurement value of the received power from the latest actual measurement value of the received power is a positive value, the command value determination unit 143 uses first response performance data corresponding to an increase in output power as the response performance data, and if the result is a negative value, uses second response performance data corresponding to a decrease in output power as the response performance data.

[0061] The command value determination unit 143 may determine whether to use the first response performance data or the second response performance data based on a value obtained by multiplying the first difference value (P1) and the second difference value (P2) by different weighting coefficients and then adding them together. That is, the command value determination unit 143 calculates a required change amount ΔC shown in the following (Equation 3), and calculates an output command value using (Equation 4). ΔC=k1×P1+k2×P2 (Formula 3) Output command value = Previous output command value + Response performance data × ΔC ÷ PCS rated capacity (Equation 4)

[0062] Here, k1 is a weighting coefficient for the first difference value, and k2 is a weighting coefficient for the second difference value. The command value determination unit 143 uses the first response performance data when ΔC indicates a positive value, and uses the second response performance data when ΔC indicates a negative value. By allowing the command value determination unit 143 to set the weighting coefficients via the reception unit 12, an administrator of the control device 1 can make adjustments so that the command value determination unit 143 can determine an optimal output command value according to the characteristics of the power conditioner 3.

[0063] [Processing flow in the control device 1] 3 to 6 are flowcharts showing the flow of processing in the control device 1. Fig. 3 is a flowchart of the overall operation of the control device 1. The control device 1 repeats the operation shown in Fig. 3 until an operation to end the operation is received.

[0064] The data acquisition unit 141 acquires received power data indicating the value of received power from the power grid P measured by the digital power meter 4 or the analog power meter 5 (S1). The data acquisition unit 141 monitors whether the received power value is equal to or less than a predetermined threshold (hereinafter referred to as the "UPR threshold") (S2). When the data acquisition unit 141 determines that the received power value is equal to or less than the UPR threshold (YES in S2), it causes the command value determination unit 143 to execute UPR processing to reduce the power output by the power conditioner 3 (S3). The UPR processing will be described in detail later.

[0065] If the data acquisition unit 141 determines that the received power value is greater than the UPR threshold and that there is no need to reduce the power output by the power conditioner 3 (NO in S2), it causes the upper limit value determination unit 142 to execute processing to determine an upper limit value (S4). Subsequently, the command value determination unit 143 executes output command processing to input an output command value to the power conditioner 3 so that the output command value becomes equal to or less than the upper limit value (S5). The control device 1 repeats the operations from S1 to S5, for example, until an end operation is performed in the reception unit 12 (NO in S6).

[0066] (UPR processing) 4 is an operational flowchart of the UPR process. In order to prevent reverse power flow from occurring, it is conceivable to reduce the power output by the power conditioner 3 when it is detected that a reverse power flow may occur. However, if the time required for the power conditioner 3 to change the power after receiving a new output command value is long compared to the operating time limit of the reverse power relay 6, there is a risk that reverse power flow will occur before the power output by the power conditioner 3 is reduced. Therefore, the command value determiner 143 determines the UPR process method based on the operating time limit of the reverse power relay 6, as an example.

[0067] The command value determination unit 143 identifies the operation time limit of the reverse power relay 6 by referring to data indicating the characteristics of the reverse power relay 6 stored in the storage unit 13 (S31). The command value determination unit 143 determines whether the identified operation time limit is equal to or greater than a predetermined time threshold (S32). As described above, the time threshold is a value determined based on, for example, the maximum rate of change in the output power of the power conditioner 3. The command value determination unit 143 may determine the time threshold corresponding to the model name of the power conditioner 3 or the model name of the power generation system S input by the reception unit 12 by referring to a time threshold data table stored in the storage unit 13 that associates information indicating the type of the power conditioner 3 (for example, model name) with the time threshold.

[0068] When the command value determination unit 143 determines that the operation time limit of the reverse power relay 6 is equal to or greater than the time threshold value (YES in S32), it notifies the power conditioner 3 of a new output command value obtained by changing the output command value to a smaller value (S33). By operating the command value determination unit 143 in this manner, the power conditioner 3 can prevent reverse power flow while outputting power without the reverse power relay 6 blocking the path, and therefore the power generated by the photovoltaic power generation device 2 can be used effectively.

[0069] On the other hand, when the command value determination unit 143 determines that the operation time limit of the reverse power relay 6 is less than the time threshold value (NO in S32), it notifies the power conditioner 3 of an output stop instruction (S34). By operating in this manner, the command value determination unit 143 can prevent the reverse power relay 6 from cutting off the path before the power conditioner 3 reduces the power, even if the operation time limit of the reverse power relay 6 is early.

[0070] In S31, the command value determination unit 143 may refer to an operation time limit data table that associates information indicating the type of the reverse power relay 6 (e.g., model name) with the operation time limit, which is stored in the storage unit 13, to identify the operation time limit of the reverse power relay 6 that corresponds to the model name of the reverse power relay 6 input in the reception unit 12 or the model name of the power generation system S. Furthermore, if the operation time limit of the reverse power relay 6 is variable, the command value determination unit 143 may identify the operation time limit of the reverse power relay 6 based on the operation time limit input in the reception unit 12 or the operation time limit stored in the storage unit 13. By the command value determination unit 143 identifying the operation time limit of the reverse power relay 6 in this manner, a common control device 1 can be used regardless of the type of the reverse power relay 6 used in the power generation system S.

[0071] (Upper limit determination process) 5 is an operational flowchart of a process for determining the upper limit of the output command value. Upper limit determination unit 142 first determines whether or not a method for determining the upper limit has been designated by the administrator of control device 1 (S41). Specifically, upper limit determination unit 142 refers to designation information, stored in storage unit 13, indicating the method designated by the administrator of control device 1. If no upper limit determination method has been designated (YES in S41), upper limit determination unit 142 proceeds to S42 and determines for itself whether or not to determine the upper limit using the amount of solar radiation.

[0072] In this case, the upper limit value determination unit 142 acquires historical data on the amount of solar radiation stored in the storage unit 13 (S42), and determines whether the amount of fluctuation in the amount of solar radiation over a predetermined period of time in the past (for example, 10 minutes) is equal to or greater than a threshold (S43). As described above, the threshold is a value determined based on, for example, the amount of received power at that time, but it may also be a value determined in advance by an administrator or designer of the control device 1. If the upper limit value determination unit 142 determines that the amount of fluctuation is equal to or greater than the threshold (YES in S43), it acquires solar radiation data from the actinometer 8 (S44), and calculates the upper limit value using the above-mentioned (Equation 1) (S45).

[0073] On the other hand, if an upper limit value determination method is specified (NO in S41), upper limit value determination unit 142 determines whether or not the designation information stored in storage unit 13 indicates that the amount of solar radiation is to be used (S46).If upper limit value determination unit 142 determines that the amount of solar radiation is to be used (YES in S46), it proceeds to S44 and calculates the upper limit value using (Equation 1) (S45).

[0074] When it is determined that use of the amount of solar radiation is not specified and use of the operation rate of the power conditioner 3 is specified (NO in S46), the upper limit value determination unit 142 calculates the value of the output power of the power conditioner 3 relative to the rated capacity of the power conditioner 3 as the PCS operation rate (S47). Furthermore, when the value obtained by subtracting the target value of the received power from the actual measured value of the received power is positive, the upper limit value determination unit 142 calculates the output margin rate by dividing this value by the rated power of the power conditioner 3 (S48). Then, the upper limit value determination unit 142 calculates the upper limit by adding the PCS operation rate and the output margin rate as shown in the above-mentioned (Equation 2) (S49).

[0075] (Calculation process of output command value) 6 is an operational flowchart of the process for calculating the output command value. First, the command value determination unit 143 calculates a difference value P1 between the target value of received power and the current received power (S51). The command value determination unit 143 also calculates a change amount P2 in the received power (S52). Next, the command value determination unit 143 calculates a required change amount ΔC shown in (Equation 3) (S53).

[0076] If ΔC is a positive value (YES in S54), the command value determination unit 143 determines to use, as the response performance data, the first response performance data corresponding to the case where the power conditioner 3 increases the output power (S55).If ΔC is a negative value (NO in S54), the command value determination unit 143 determines to use, as the response performance data, the second response performance data corresponding to the case where the power conditioner 3 decreases the output power (S56).

[0077] Next, the command value determination unit 143 calculates the value ΔC_m of output power that the power conditioner 3 can change by multiplying the response performance data by the rated capacity of the power conditioner 3 (S57). If the absolute value of ΔC is greater than ΔC_m (YES in S58), the command value determination unit 143 replaces the absolute value of ΔC used in calculating the output command value with the absolute value of ΔC_m (S59). On the other hand, if the absolute value of ΔC is equal to or less than ΔC_m (NO in S58), the command value determination unit 143 uses ΔC as is to calculate the output command value (S60). The command value determination unit 143 calculates the output command value using the ΔC determined in S59 or S60 using the above-mentioned (Equation 4) (S61).

[0078] [Effects of Power Generation System S] As described above, the control device 1 has an upper limit value determination unit 142 that determines the upper limit value of the output command value to be notified to the power conditioner 3 based on at least one of the amount of solar radiation received by the solar power generation device 2 and the output power of the power conditioner 3. By configuring the control device 1 in this way, it becomes possible to control the power conditioner 3 taking into account fluctuations in the amount of solar radiation, and it is possible to effectively utilize the power generated by the solar power generation device 2 while preventing reverse power flow.

[0079] Furthermore, the control device 1 has a command value determination unit 143 that determines whether to notify the power conditioner 3 of an output command value smaller than the current output command value or to notify the power conditioner 3 of an instruction to stop output, based on the operating time limit of the reverse power relay 6 that prevents output of power to the power system P when the received power from the power system P falls below a threshold. By configuring the control device 1 in this way, reverse power flow can be prevented regardless of the operating time limit of the reverse power relay 6, and the power generated by the photovoltaic power generation device 2 can be effectively utilized.

[0080] In the above description, the power generation system S has the reverse power relay 6 and the circuit breaker 7, but since the present invention reduces the probability of reverse power flow occurring, the power generation system S does not have to have the reverse power relay 6 and the circuit breaker 7. In this way, the present invention also makes it possible to reduce the cost of the equipment.

[0081] The present invention has been described above using embodiments, but the technical scope of the present invention is not limited to the scope described in the above embodiments, and various modifications and changes are possible within the scope of the gist of the present invention. For example, all or part of the device can be configured by functionally or physically distributing or integrating any unit. Furthermore, new embodiments resulting from any combination of multiple embodiments are also included in the embodiments of the present invention. The effects of the new embodiments resulting from the combination also have the effects of the original embodiments. [Explanation of symbols]

[0082] 1. Control device 2. Solar power generation equipment 3 Power conditioner 4 Digital power meters 5 Analog power meter 6 Reverse Power Relay 7 Circuit Breaker 8 Pyranometer 11 Communications Department 12 Reception 13 Storage section 14 Control Unit 141 Data Acquisition Unit 142 Upper limit value determination unit 143 Command value determination unit

Claims

1. A control device that controls a power conversion device that generates AC power to be supplied to a load based on DC power output from a solar power generation device, a command value determination unit that determines an output command value for controlling power generated by the power conversion device based on power received from a power grid; an upper limit value determination unit that determines an upper limit value of the output command value based on the amount of solar radiation received by the solar power generation device; and the command value determiner notifies the power electronics device of the output command value when the determined output command value is equal to or less than the upper limit value, and notifies the power electronics device of the upper limit value when the determined output command value is greater than the upper limit value. Control device.

2. the upper limit value determination unit determines the upper limit value based on a relationship between a rated capacity of the power conversion device and a maximum possible output value that the solar power generation device can generate power under a current amount of solar radiation. The control device according to claim 1 .

3. A control device for controlling a power conversion device that generates AC power to be supplied to a load based on DC power output from a solar power generation device, a command value determination unit that determines an output command value for controlling power generated by the power conversion device based on power received from a power grid; an upper limit value determination unit that determines an upper limit value of the output command value based on at least one of the amount of solar radiation received by the solar power generation device and the output power of the power conversion device; and when determining the upper limit value based on the output power of the power electronics device, the upper limit value determiner determines, as the upper limit value, a value obtained by adding a predetermined margin rate to an operation rate, which is a ratio of the current output power of the power electronics device to a rated capacity of the power electronics device; the command value determiner notifies the power electronics device of the output command value when the determined output command value is equal to or less than the upper limit value, and notifies the power electronics device of the upper limit value when the determined output command value is greater than the upper limit value. Control device.

4. the upper limit value determination unit uses the margin rate determined based on a difference between the target value of the received power and the actual measured value of the received power. The control device according to claim 3 .

5. the upper limit value determination unit reduces the margin rate as the fluctuation in the operation rate of the power electronics device within a predetermined period increases. The control device according to claim 3 or 4.

6. the upper limit value determination unit uses the margin rate corresponding to the current time or weather by referring to data in which the time or weather is associated with the margin rate; The control device according to any one of claims 3 to 5.

7. the upper limit value determination unit further includes a reception unit that receives a selection of a method for determining the upper limit value, The upper limit value determination unit when the reception unit receives a selection of a method using the current amount of solar radiation, determining the upper limit value based on a relationship between a rated capacity of the power conversion device and a maximum possible output value that the solar power generation device can generate under the current amount of solar radiation; When the reception unit does not receive a selection of a method using the current amount of solar radiation, the upper limit value is determined to be a value obtained by adding a predetermined margin to a ratio of the current output power of the power conversion device to a rated capacity of the power conversion device. The control device according to any one of claims 1 to 6.

8. The upper limit value determination unit when the magnitude of fluctuation in the amount of solar radiation on the solar power generation device within a predetermined period is equal to or greater than a predetermined threshold, determining the upper limit value based on a relationship between a rated capacity of the power conversion device and a maximum possible output value that the solar power generation device can generate under the current amount of solar radiation; when the magnitude of fluctuation in the amount of solar radiation on the solar power generation device within a predetermined period is less than a predetermined threshold, determining the upper limit value to be a value obtained by adding a predetermined margin rate to a ratio of the current output power of the power conversion device to a rated capacity of the power conversion device; The control device according to any one of claims 1 to 6.

9. the command value determiner determines the output command value by referring to response performance data indicating the response performance of the power conversion device so that overshoot and undershoot when the output power of the power conversion device changes are equal to or less than a predetermined amount. A control device according to any one of claims 1 to 8.

10. the command value determination unit determines whether the output power of the power conversion device will increase or decrease based on a relationship between the actual measured value of the received power and the target value of the received power, and refers to the response performance data selected based on the determination result from either first response performance data corresponding to a case where the output power increases or second response performance data corresponding to a case where the output power decreases. The control device according to claim 9.

11. the command value determination unit determines whether the output power of the power conversion device will increase or decrease based on the amount of change in the received power, and refers to the response performance data selected based on the determination result from either first response performance data corresponding to the case where the output power increases or second response performance data corresponding to the case where the output power decreases. The control device according to claim 9.

12. the command value determination unit uses, when a result of adding a first difference value obtained by subtracting a target value of the received power from the latest actual measurement value of the received power and a second difference value obtained by subtracting a previous actual measurement value of the received power from the latest actual measurement value of the received power, indicates a positive value, first response performance data corresponding to a case in which the output power increases as the response performance data, and when the result indicates a negative value, second response performance data corresponding to a case in which the output power decreases as the response performance data. A control device according to any one of claims 9 to 11.

13. the command value determination unit determines, when the received power from the power grid becomes equal to or less than a threshold, whether to notify the power electronics device of an output command value smaller than the current output command value or to notify the power electronics device of an instruction to stop output, based on an operation time limit of a relay for preventing power from being output to the power grid. A control device according to any one of claims 1 to 11.

14. The computer executes determining, based on power received from the power grid, an output command value for controlling power generated by a power conversion device that generates AC power to be supplied to a load based on DC power output from the solar power generation device; determining an upper limit value of the output command value based on the amount of solar radiation received by the solar power generation device; notifying the power electronics device of the output command value when the determined output command value is equal to or less than the upper limit value, and notifying the power electronics device of the upper limit value when the determined output command value is greater than the upper limit value; A control method comprising:

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