Power smoothing device, power smoothing method, and power smoothing program

Abstract

To smooth the output power of renewable energy more easily while using a small-capacity power storage device.SOLUTION: A control device 30 as a power smoothing device smoothing power output from a power supply system 1 including a power generation device generating power using renewable energy and a power storage device, includes: an acquisition unit which acquires information related to the power generated by the power generation device; a calculation unit which calculates a combined output target value related to the power output from the power supply system by smoothing the generated power without a phase delay, and calculates charging / discharging power from the power storage device on the basis of the combined output target value; and an output unit which outputs an operation command specifying the charge / discharge power to the power storage device on the basis of the calculation result of the charge / discharge power.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a power smoothing device, a power smoothing method, and a power smoothing program. [Background technology]

[0002] In recent years, the introduction of power generation equipment using renewable energy has progressed in order to overcome the problem of global warming and realize a carbon-free society. However, renewable energy often generates power with large fluctuations. For this reason, methods have been studied for smoothing the output fluctuations of renewable energy power generation equipment by using charging and discharging of power storage devices such as storage batteries. Here, when calculating the target value for the combined output from the renewable energy power generation equipment and the power storage device, a phase lag (shift) occurs with respect to the amount of power generated by the power generation equipment. In response to this, Patent Documents 1 and 2 study methods for reducing this time lag.

[0003] Specifically, Patent Document 1 considers a method of calculating a composite output target value by preparing the photovoltaic power generated on a clear day as a standard power generation, extracting a shadow fluctuation component by dividing the photovoltaic power generation power by the standard power generation power, smoothing the shadow fluctuation component, and multiplying the smoothed shadow fluctuation component by the standard power generation power. Also, Patent Document 2 considers a method of applying a second-order delay transfer function filter K(s) as a method of calculating the charge / discharge power of a storage battery from the output of a power generation device. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-140121 [Patent Document 2] Japanese Patent Publication No. 2020-198702 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the method described in Patent Document 1 may still cause a phase lag when smoothing the shadow fluctuation component, so it is thought that it will be necessary to adjust charging and discharging using a power storage device to a certain extent. Furthermore, Patent Document 1 requires that the standard power generation be calculated in advance, but it is not easy to accurately determine the power generated by solar power generation on a clear day. Specifically, when calculating the power generated by solar power generation on a clear day, in addition to the incident angle of sunlight, which is determined by latitude, longitude, date and time, there are various influences that may be present, such as the temperature of the solar panel, deterioration or dirt on the panel, surrounding topography (mountains and valleys) and buildings (skyscrapers, chimneys, etc.). On the other hand, the method described in Patent Document 2 uses three adjustment parameters K as parameters for setting the transfer function filter of renewable energy. p , b1, and b0 must be set, but the adjustment work is not easy. In particular, depending on b1 and b0, the poles of the transfer function filter K(s) may have imaginary parts, which may cause the combined output target value (or battery command) to oscillate even when the power generated by renewable energy is constant. As such, the methods described in Patent Documents 1 and 2 have room for further improvement in terms of achieving both a smaller capacity for the power storage device and smoothing of the output power of renewable energy.

[0006] The present disclosure aims to provide a technology that makes it possible to more easily smooth the output power of renewable energy while using a small-capacity power storage device. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, a power smoothing device according to one embodiment of the present disclosure is a power smoothing device that smooths the power output from a power supply system that includes a power generation device that generates power using renewable energy and a power storage device, and includes an acquisition unit that acquires information related to the power generated by the power generation device, a calculation unit that calculates a composite output target value related to the power output from the power supply system by smoothing the generated power with suppressed phase delay, and calculates the charge / discharge power from the power storage device based on the composite output target value, and an output unit that outputs an operation command specifying the charge / discharge power to the power storage device based on the calculation result of the charge / discharge power.

[0008] A power smoothing method according to one embodiment of the present disclosure is a power smoothing method for smoothing power output from a power supply system including a power generation device that generates power using renewable energy and a power storage device, and includes the steps of: acquiring information related to the power generated by the power generation device; calculating a composite output target value related to the power output from the power supply system by smoothing the generated power with suppressed phase delay; calculating charge / discharge power from the power storage device based on the composite output target value; and outputting an operation command specifying the charge / discharge power to the power storage device based on the calculation result of the charge / discharge power.

[0009] A power smoothing program according to one embodiment of the present disclosure is a power smoothing program that causes a computer to smooth the power output from a power supply system that includes a power generation device that generates power using renewable energy and a power storage device, and causes the computer to acquire information related to the power generated by the power generation device, calculate a composite output target value related to the power output from the power supply system by smoothing the generated power with suppressed phase delay, calculate charge / discharge power from the power storage device based on the composite output target value, and output an operation command specifying the charge / discharge power to the power storage device based on the calculation result of the charge / discharge power.

[0010] According to the above-described power smoothing device, power smoothing method, and power smoothing program, a composite output target value for power output from a power supply system is calculated by smoothing the power generated by a power generation device with suppressed phase delay. Then, charging / discharging power from a power storage device is calculated based on the composite output target value. By using such a method, a composite output target value that has been smoothed with suppressed phase delay is obtained, and charging / discharging power based on the composite output target value is commanded to the power storage device. When the composite output target value is smoothed with suppressed phase delay, the difference between the composite output target value and the power generated by the power generation device can be reduced, thereby making it possible to smooth the output power of renewable energy while using a smaller-capacity power storage device. Furthermore, smoothing with suppressed phase delay can be achieved by simpler parameter adjustment than previously considered methods, making it easier to smooth the output power of renewable energy while using a smaller-capacity power storage device.

[0011] The smoothing with suppressed phase lag may be performed by combining smoothing with phase lead compensation. By performing smoothing in combination with phase lead compensation, the phase lag is substantially suppressed, and it is possible to reduce the difference between the combined output target value and the power generated by the power generation device.

[0012] The calculation unit may further correct the calculated combined output target value based on the capacity of the power storage device to calculate the charge / discharge power from the power storage device. As described above, by further correcting the calculated combined output target value based on the capacity of the power storage device, it is possible to prevent a command from being issued to charge / discharge power under conditions that exceed the capacity of the power storage device. Therefore, it is possible to perform control taking the capacity of the power storage device into consideration.

[0013] The calculation unit may calculate the combined output target value based on the power generation capacity of the power generation device. With the above configuration, it is possible to perform control taking into account the power generation capacity of the power generation device.

[0014] The calculation unit may calculate the target value of the combined output power so that the rate of change of the target value of the combined output power is within a predetermined range. When it is necessary to control the rate of change of the target value of the combined output power, the above configuration makes it possible to perform control taking into account the power generation capacity of the power generation device. [Effects of the Invention]

[0015] According to the present disclosure, a technique is provided that makes it possible to more easily smooth the output power of renewable energy while using a small-capacity power storage device. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a schematic diagram of a power supply system according to an embodiment. [Figure 2] FIG. 2 is a diagram illustrating a conventional smoothing process. [Figure 3] FIG. 3 is a block diagram illustrating the control unit. [Figure 4] FIG. 4 is a diagram showing an example of fluctuations in photovoltaic power generation used in the simulation. [Figure 5] FIG. 5 is a diagram illustrating the simulation results. [Figure 6] FIG. 6 is a diagram illustrating the simulation results. [Figure 7] FIG. 7 is a diagram illustrating the simulation results. [Figure 8] FIG. 8 is a diagram illustrating the simulation results. [Figure 9] FIG. 9 is a block diagram illustrating a control unit according to a modified example. [Figure 10] FIG. 10 is a diagram illustrating an example of a hardware configuration of the control device. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and duplicated explanations will be omitted.

[0018] [Power supply system] First, a schematic configuration of a power supply system 1 will be described with reference to Fig. 1. Fig. 1 is a schematic diagram of a power supply system according to an embodiment. The power supply system 1 includes a microgrid 2.

[0019] The microgrid 2 is connected to an external power grid 90 (external power supply system). The microgrid 2 is capable of transmitting and receiving power to and from the external power grid 90. When the grid power has a positive value, the microgrid 2 receives power from the external power grid 90, and when the grid power has a negative value, the microgrid 2 transmits power to the external power grid 90. The microgrid 2 includes a power generation system 21 (power generation device), a power storage system 23 (power storage device), a connection unit 24, a received power measurement unit 26, a transmitted power measurement unit 27, and a control device 30 (power smoothing device).

[0020] The power generation system 21 is a system that generates power using renewable energy. In this embodiment, the power generation system 21 is a photovoltaic (PV) power generation system and includes a solar panel 21a and a power conditioning system (PCS) (not shown). The power conditioner is a power conversion device that converts power generated by the solar panel 21a. The power conditioner converts DC power from the solar panel 21a into AC power and outputs the AC power to the connection unit 24. Note that the power generation system 21 may also be a system that generates power using renewable energy other than solar power. For example, the power generation system 21 may be a wind power generation system, a geothermal power generation system, a biomass power generation system, a waste-to-energy generation system, or other power generation system.

[0021] The power conversion capacity and AC power output capacity of the power conditioner (PCS) in the power generation system 21 relate to the power generation capacity of the power generation system 21. Therefore, the capacity of the PCS (PCS capacity) is used as an index related to the power generation capacity in the control device 30 described later. Therefore, information related to the PCS capacity can also be held in the control device 30.

[0022] The power storage system 23 is a system capable of charging and discharging power. The power storage system 23 includes a power storage device (power storage device) and a power conditioner. The power storage device may be a secondary battery such as a lithium-ion battery, a lead-acid battery, or a redox flow battery. It may also be a power storage device other than a secondary battery, such as a large-capacity capacitor, a flywheel, or a compressed air energy storage system. The power conditioner is a power conversion device that converts power between the power storage device and the connection unit 24. The power conditioner converts DC power from the power storage device into AC power and outputs the AC power to the connection unit 24. The power conditioner converts AC power from the connection unit 24 into DC power and outputs the DC power to the power storage device. The power conversion capacity and DC power output capacity of the power conditioner (PCS) in the power storage system 23 relate to the output performance from the power storage system 23. The power storage system 23 may also include a charge / discharge control device, a device for monitoring the remaining battery capacity, etc.

[0023] The connection unit 24 distributes power to each unit including the external power system 90. The connection unit 24 is, for example, a distribution board. The connection unit 24 has a function of notifying the control device 30 of the control content of the own device. The connection unit 24 also has a function of collecting the power generated in the power generation system 21, the charging / discharging power in the power storage system 23, and the measurement results of the received power measurement unit 26 and the transmitted power measurement unit 27. The connection unit 24 also has a function of notifying the control device 30 of this collected information from the connection unit 24.

[0024] Received power measuring unit 26 measures the power received from external power system 90. Transmitted power measuring unit 27 measures the power transmitted to external power system 90. Received power measuring unit 26 and transmitted power measuring unit 27 are, for example, power meters.

[0025] The control device 30 acquires operating conditions related to power within the microgrid 2. Furthermore, the control device 30 acquires, via the connection unit 24, the power generated in the power generation system 21, the charging / discharging power in the power storage system 23, and the measurement results in the received power measurement unit 26 and the transmitted power measurement unit 27, as described above. The control device 30 can also issue commands related to charging and discharging (charge / discharge commands) to the power storage system 23. Functionally, the control device 30 is configured to include a communication unit 31 and a control unit 32.

[0026] The communication unit 31 is, for example, a functional unit that communicates with the connection unit 24. The communication unit 31 may communicate with the connection unit 24 via a communication network, for example. The communication network may be configured as either a wired or wireless network. The communication unit 31 acquires information about the above-mentioned units from the connection unit 24. In other words, the communication unit 31 functions as an acquisition unit that acquires information related to the power generated by the renewable energy power generation device.

[0027] The control unit 32 is a functional unit that performs calculations for the output power of renewable energy from the microgrid 2 and transmits charge / discharge commands to the power storage system 23 based on the calculation results. In other words, the control unit 32 has a function as a calculation unit that calculates the charge / discharge power in the power storage device based on the generated power, and a function as an output unit that outputs an operation command to the power storage device based on the calculation result by the calculation unit. The operation command includes information that specifies the charge / discharge power in the power storage device. Note that the control unit 32 may be configured as a separate unit consisting of a calculation unit and an output unit.

[0028] Here, smoothing of the output power of renewable energy will be explained with reference to Figure 2. Renewable energy, typified by solar power generation, is known to have large fluctuations in the power generated depending on the time of day, weather, and season, and is sometimes referred to as variable renewable energy. When a large number of power generation systems using renewable energy, which has large fluctuations in power generation, are introduced, there is a possibility that this will have a negative impact on the quality of power, such as voltage or frequency. In response to this, technologies for smoothing output using power storage devices such as storage batteries have been studied. Generally, a process can be performed in which a target value for the combined output, which is the sum of the charging and discharging power of the storage battery and the power generated by renewable energy, is first calculated, and then the output corresponding to the difference between this target value for the combined output and the current power generated by renewable energy is adjusted using the storage battery.

[0029] However, when using this method to perform stronger smoothing, it is possible to increase the time constant of the first-order lag filter or the number of samples in the moving average process. However, using the above method can result in a time lag (phase lag) in the composite output target value. Figure 2 shows an example of a time lag in the composite output target value. In Figure 2, the horizontal axis represents the time of day (from 4:00 to 20:00), and the vertical axis represents power. Figure 2 also shows the power generated by solar power generation and the composite output target value smoothed using a first-order lag filter with a one-hour time constant. As shown in Figure 2, when smoothed using the above method, the composite output target value is smoother than solar power generation, but it is still confirmed that there is a time lag of about one hour in the rise and fall. If the composite output target value has a time lag relative to the power generated by renewable energy, the difference between the composite output target value and the power generated by renewable energy becomes larger. As a result, the charging and discharging power of the storage battery increases. Therefore, if power adjustment is to be performed in accordance with the combined output target value, a storage battery with a larger capacity and output will be required, which may increase equipment costs.

[0030] In contrast to this, in the power supply system 1 according to this embodiment, the time delay is reduced by changing the smoothing method used by the control unit 32 of the control device 30. This will be described in detail later. In this manner, the control device 30 may have a function as a so-called energy management system (EMS) that controls the charging and discharging power of the power storage system 23.

[0031] The control device 30 may acquire power information individually by individually connecting to the devices that make up each part, instead of acquiring the power information of each part from the connection unit 24. The control device 30 may also be incorporated into the power storage system 23, for example.

[0032] In addition to the above-mentioned components, the microgrid 2 may also include power load devices. For example, the control device 30 in FIG. 1 and facility lighting devices and EV charging stations (not shown) correspond to power load devices in the microgrid 2. However, in the following explanation, they are not described here. This is because the power load caused by the power load devices is sufficiently small compared to the power generated in the microgrid 2 and can be ignored. Instead of ignoring the power load caused by the power load devices, for example, fluctuations in the power generated in the power generation system 21 may be processed in a state where the power load caused by the power load devices is included.

[0033] [Control content by the control device] Energy smoothing performed in the control unit 32 of the control device 30 will be described with reference to Fig. 3. Fig. 3 is a block diagram for energy smoothing control performed by the control device 30 shown in Fig. 1. As shown in Fig. 3, the control unit 32 is configured to include a smoothing filter 41, a phase lead filter 42, a saturator 43, and a change rate limiter 44.

[0034] The smoothing filter 41 is a filter that smooths data, and is expressed by, for example, the following equation (1).

[0035]

number

[0036] In equation (1), T1 is a time constant and is a positive value, and s is a complex number.

[0037] The phase lead filter 42 is a filter that performs phase lead compensation, and is expressed by, for example, the following equation (2).

[0038]

number

[0039] In the formula (2), T2 is a time constant and a positive value, and a is an adjustment parameter and a positive value.

[0040] The saturator 43 has a function of setting upper and lower limits based on the PCS capacity D1 of the power generation system 21. If the input signal is within the set upper and lower limits, the saturator 43 outputs that value; if it is below the lower limit, the saturator 43 outputs the lower limit value; and if it is above the upper limit, the saturator 43 outputs the upper limit value. The upper limit value may be set to the PCS capacity (rated capacity), for example, to prevent the combined output target value from exceeding the PCS capacity (i.e., transmitting power greater than the rated power of the photovoltaic power generation due to discharging). The lower limit value may be set to 0 to prevent the combined output target value from becoming a negative value (i.e., receiving power due to charging). Furthermore, although using the phase lead filter 42 may make the combined output target value more likely to overshoot the generated power, applying the saturator 43 can suppress the overshoot.

[0041] The rate limiter 44 has a function of setting the rate of change of the combined output target value to a certain value or less. As a technical requirement for mitigating output fluctuations in the microgrid 2, a contract with the power transmission and distribution company may have a clear standard for the rate of fluctuation of the combined output. In such cases, the rate limiter 44 is used to limit the rate of change so that the combined output target value does not exceed the standard. A commonly known technical requirement for mitigating output fluctuations is "1% or less of the power plant rated output per minute." Therefore, the rate limiter 44 can be set based on the above technical requirements.

[0042] In the control unit 32, first, the renewable energy generated power y re When you get the renewable energy generated power y re A smoothing filter 41 is applied to the result of applying the smoothing filter 41. Furthermore, a phase lead filter 42 is applied to the result of applying the smoothing filter 41. By applying these two filters, a calculated value of the combined output target value calculated based on the two filters is obtained. Furthermore, by applying a saturator 43 based on the PCS capacity D1 and a change rate limiter 44 to the calculated value of the combined output target value output from the phase lead filter 42, a combined output target value r that takes into account the PCS capacity D1 and technical requirements related to mitigating output fluctuations is obtained. sys is obtained.

[0043] Furthermore, the composite output target value r sys and renewable energy power generation re By calculating the difference between bat The charge / discharge power command value r is calculated. bat If it is positive, it indicates that the power storage system 23 needs to be discharged, and if it is negative, it indicates that the power storage system 23 needs to be charged.

[0044] Charge / discharge power command value r to the power storage system 23 bat is transmitted, the power storage system 23 receives the charge / discharge power command value r bat Charge and discharge power y according to batAs a result, the renewable energy generated power y re and the charge / discharge power y in the power storage system 23 bat The sum of these is the output power of microgrid 2, which is the composite output y sys The composite output y sys When the value is positive, it indicates that power is transmitted from the microgrid 2 to the outside, and when the value is negative, it indicates that power is received from the microgrid 2.

[0045] [About smoothing filters and phase lead filters] In the above-described power supply system 1, the control unit 32 of the control device 30 combines the smoothing filter 41 and the phase lead filter 42 to determine the composite output target value, thereby performing smoothing with suppressed phase delay. This point will be described in detail.

[0046] As described above, the phase lead filter 42 is expressed by the above-mentioned formula (2). In this case, T2 is a time constant and is a positive value. Furthermore, a is an adjustment parameter and is a positive value. As the adjustment parameter a increases, the phase lead increases. Looking at formula (2), when a=1, the denominator and numerator become equal, and F forward (s)=1. Therefore, the adjustment parameter a is usually set to be greater than 1.

[0047] Here, smoothing can be performed more appropriately if the time constant T2 and adjustment parameter a in the phase lead filter 42 satisfy the relationship of the following equations (3) and (4), which are set based on the time constant T1 in the smoothing filter 41 as well.

[0048]

number

[0049] In particular, when T2=T1 and a=2, the smoothing filter 41 and the phase lead filter 42 have a special relationship. This point will be explained below.

[0050] For the sake of analysis, it is assumed that the control unit 32 does not include the saturator 43 and the change rate limiter 44. re From the battery charge / discharge power command value r bat The transfer function to is defined as R(s). The transfer function R(s) is given by the following equation (5).

[0051]

number

[0052] According to the above formula (5), it can be seen that for any a, T1, T2 (where a>1, T1>0, and T2>0), the poles of the transfer function R(s) (values ​​of s where the denominator is 0, i.e., -1 / T1 and -1 / T2) have no imaginary parts. This means that even if the renewable energy generated power, which is the input signal to the transfer function R(s), undergoes a step change, the charge / discharge command to the power storage system 23, which is the output signal from the transfer function R(s), does not contain any oscillatory fluctuating components. Since the command value in the charge / discharge command does not contain any oscillatory fluctuating components, parameter adjustment is easier than with the method described in Patent Document 2.

[0053] Renewable energy generation electricity re is a unit step signal, the charge / discharge power command value r bat The value of at time infinity can be found using the final value theorem. In this case, it can be seen that it is 0 for any a, T1, and T2, as shown in the following formula (6).

[0054]

number

[0055] The relationship shown in the above formula (6) is that for any a, T1, and T2, the renewable energy generated power y reThis shows that if there is no change (if it is constant), the charging and discharging of the storage battery will be gradually stopped. In other words, this characteristic is preferable because the storage battery is installed in order to suppress fluctuations in solar power generation.

[0056] In addition, renewable energy power generation re Consider the case where the command value r of the storage battery is a ramp signal (a signal with a constant slope c [kW / s]). bat When the value of at infinity is calculated from the final value theorem, the relationship shown in the following formula (7) is obtained.

[0057]

number

[0058] In the above equation (7), when aT2-T1-T2=0, the command value for the storage battery ultimately becomes 0 (when time becomes infinite). There are various possible combinations of a, T1, and T2 that satisfy aT2-T1-T2=0, and one example is the relationship T2=T1, a=2. There may be other conditions besides this relationship that satisfy aT2-T1-T2=0. However, the above relationship T2=T1, a=2 can be considered one of the simple conditions when adjusting the parameters included in both the smoothing filter 41 and the phase lead filter 42 so that aT2-T1-T2=0 is satisfied.

[0059] According to the above analysis, when the smoothing filter 41 and the phase lead filter 42 satisfying the relationship aT2-T1-T2=0 are selected, the charging and discharging power of the energy storage system 23 is gradually reduced if the rate of change of the renewable energy power generation power is constant. Furthermore, it can be seen that the characteristic is that the charging and discharging operation of the energy storage system 23 is eventually stopped, i.e., the energy storage system 23 no longer performs charging and discharging operations. This corresponds to the combined output target value from the microgrid 2 gradually approaching the renewable energy power generation power, which can be said to result in a reduced time delay. Since the capacity of the storage battery in the energy storage system 23 is generally limited, controlling the charging and discharging operation of the energy storage system 23 to be smaller when the rate of change of the renewable energy power generation power is constant suggests that smoothing is possible without increasing the storage battery capacity. In the case of solar power generation, a situation in which the rate of change of the renewable energy power generation power is constant can be exemplified by the rise and fall of solar power generation at sunrise or sunset. In the case of wind power generation, this can be considered as a trend component of the wind power generation power. Furthermore, even when the output control by the PCS in the power generation system 21 is changed gradually, the rate of change can be made substantially constant.

[0060] In addition, under the condition that the phase lead filter 42 is not used, that is, under the condition that only the smoothing filter 41 is used, the command value r bat The value of (aT2-T1-T2)c at infinite time is not "(aT2-T1-T2)c" as shown in the above formula (7), but "-T1c." In other words, even if the time is set to infinity, charging and discharging will continue for the amount of time equal to the product of the rate of change c and the time constant T1. However, since the capacity of a storage battery is limited, it is possible that the storage battery will fall into a fully charged or over-discharged state over time, making it impossible to continue charging and discharging control.

[0061] It should be noted that the above considerations are based on an analysis assuming an infinite time period, and in reality, a, T1, and T2 do not necessarily have to be selected to satisfy the relational expression aT2-T1-T2=0. However, if a, T1, and T2 are selected such that aT2-T1-T2 is sufficiently small, it is expected that practically the same effect as when the relational expression aT2-T1-T2=0 is satisfied can be achieved. In other words, if the rate of change in power generated from renewable energy is constant, it is expected that the amount of charge and discharge by the power storage system 23 will be controlled to gradually decrease.

[0062] [Verification by simulation] Next, a description will be given of the results of a simulation relating to the control by the control unit 32 of the control device 30. In the following simulation, a case will be described in which the power generated from renewable energy is solar power generation.

[0063] Figure 4 shows the change in the amount of power generated by solar power generation over time, which is the premise of the simulation. In this simulation, the rated output of the PCS in the solar power generation system is set to 1000 kW. Generally, the rated output of a PCS is set to be 10 to 20 percent lower than the rated output of the solar panels. Therefore, as shown in Figure 4, there are cases where the maximum output remains constant during the day. In the example shown in Figure 4, it is slightly cloudy in the morning (especially from around 7:00 to 10:00), and the generated power fluctuates dramatically, with a fluctuation of about 40% of the rated output.

[0064] Meanwhile, the configuration of each part of the microgrid 2 assumed in the simulation is as follows: Specifically, the battery capacity of the power storage system 23 is 2000 kWh, the rated output is ±500 kW, and the initial capacity at the start of the simulation is 300 kWh.

[0065] The smoothing filter 41 used in the control unit 32 of the control device 30 is a first-order lag system, with a time constant T1 of 3600 seconds. The phase lead filter 42 is set to satisfy the conditions T2=T1 and a=2. The upper and lower limits of the saturator 43 are set to 1000 kW (corresponding to the rated capacity of the PCS in the power generation system 21) and 0 kW. The fluctuation range of the change rate limiter 44 is set to ±9 kW / min. This corresponds to 0.9% / min, since the rated capacity of the PCS is 1000 kW.

[0066] On the other hand, for comparison, a device that performs smoothing used in the conventional method was assumed to perform processing according to a block diagram that does not include the phase lead filter 42, saturator 43, and change rate limiter 44, as compared to the block diagram shown in Fig. 3. The function of the power storage system 23 and the time constant of the smoothing filter 41 are the same.

[0067] Using the smoothing method (proposed method) shown in the above embodiment and the smoothing method (conventional method) under conditions where only the smoothing filter 41 is used for comparison, a composite output target value was calculated from the photovoltaic power generation shown in Figure 4, and further, the charge / discharge power of the storage battery, the storage battery capacity, and the composite output from the microgrid were calculated.

[0068] First, the calculation results of the combined output target value are shown in Figure 5. Figure 5 also shows the solar power generation power. Comparing the results shown in Figure 5, the proposed method using the phase lead filter 42 has a smaller phase lag with respect to the solar power generation power than the conventional method.

[0069] FIG. 6 shows the charge / discharge power of the storage batteries in the energy storage system 23 calculated based on the composite output target value. It can be seen that the method proposed in this embodiment using the phase lead filter 42 has a smaller maximum absolute value of the charge / discharge power compared to the conventional method not using a phase lead filter. This result indicates that the use of the phase lead filter reduces the difference between the composite output target value and the amount of power generated in the power generation system 21. It can also be said that this suggests that the method proposed in this embodiment using the phase lead filter 42 can achieve smoothing of the output power even when using a storage battery with a smaller rated output.

[0070] Figure 7 shows the transition of the remaining capacity of the storage battery in the energy storage system 23. It can be seen that the proposed method using the phase-lead filter 42 in this embodiment exhibits less change in storage capacity than the conventional method. This result indicates that the method using the phase-lead filter 42 in this embodiment enables smoothing with a storage battery of a smaller capacity than the conventional method. Furthermore, this method reduces the amount of charge and discharge power of the storage battery, thereby reducing energy loss (charge and discharge loss) due to the storage battery. This means that the proposed method can increase the amount of transmitted power compared to the conventional method, i.e., improve operating profits from selling electricity. Note that because this series of evaluations was a simulation rather than using an actual system, the storage battery capacity was set to 2000 kWh. However, this capacity is excessive compared to the rated output of a typical solar power generation system. In practice, by changing the solar power generation pattern and repeating this simulation, an appropriate storage battery capacity that is practically feasible can be calculated. Because storage battery capacity significantly affects the price of a storage battery, selecting a storage battery with an appropriate capacity can reduce initial investment costs.

[0071] Figure 8 shows the combined output from the microgrid 2 (the sum of the output from photovoltaic power generation and the output from the storage battery). The proposed method described in this embodiment, which uses the phase-lead filter 42, achieves a value that is nearly in line with the combined output target value. It also satisfies the requirement of a "fluctuation rate of 1% / min," which may be set as a technical requirement for mitigating output fluctuations. On the other hand, the conventional method, which does not use the phase-lead filter 42, fluctuates the combined output during the time period from 3:00 PM to 4:00 PM, and does not satisfy the requirement of a "fluctuation rate of 1% / min" during this time period. This is related to the results shown in Figure 6. In other words, with the conventional method, the discharge power of the storage battery peaks at the rated power of 500 kW, and it is not possible to discharge more than 500 kW. In other words, under the conditions of this simulation, the conventional method cannot achieve a stable combined output unless the rated output of the storage battery is increased.

[0072] [Variations] The above-described embodiment is one embodiment of the present disclosure. The present disclosure is not necessarily limited to the above-described embodiment, and various modifications are possible without departing from the spirit of the present disclosure. Modifications will be described below.

[0073] For example, in the above embodiment, the block diagram ( FIG. 3 ) of the control unit 32 shows a configuration using the saturator 43 and the change rate limiter 44, but these may be omitted depending on the conditions of the power output from the microgrid 2, etc. For example, if the upper and lower limits of the combined output target value do not need to be considered, the saturator 43 can be omitted. Also, for example, if the change rate of the output power does not need to be considered, the change rate limiter 44 can be omitted. In this way, the saturator 43 and the change rate limiter 44 may be omitted depending on the operating status of the microgrid 2, the characteristics of each unit constituting the microgrid 2, etc.

[0074] When arranging the smoothing filter 41, the phase lead filter 42, the saturator 43, and the change rate limiter 44, the order may be changed. For example, the saturator 43 may be arranged after the phase lead filter 42, from the viewpoint of adjusting the saturator 43 so that the calculation result by the phase lead filter 42 is appropriate for the PCS capacity. On the other hand, the smoothing filter 41 may be arranged after the saturator 43 and the change rate limiter 44. In this way, the arrangement may be changed depending on the function of each section.

[0075] Furthermore, the order of the smoothing filter 41 and the phase lead filter 42 in the block diagram of the control unit 32 (FIG. 3) may be reversed. Alternatively, the smoothing filter 41 and the phase lead filter 42 may be combined into a single filter and implemented in the control unit 32. All of these are equivalent. A Butterworth filter, a Chebyshev filter, an elliptic filter, or the like may be designed and used as a filter having the same characteristics as a single filter combining a smoothing filter and a phase lead filter.

[0076] In the above embodiment, a configuration has been described assuming the continuous time domain, but the design may also be based on the discrete time domain. In the case of the discrete time domain, the phase lead filter of the continuous time domain described above may be converted so that it can be used in the discrete time domain. Specific conversion methods include, for example, bilinear transform (also called Tustin transform) and ZOH (Zero Order Hold) transform.

[0077] A moving average is often used as a smoothing filter in the discrete time domain, but the smoothing method is not particularly limited, and for example, a weighted moving average that places weight on the most recent sample or an exponential moving average may be used. Also, other known filters such as a low-pass FIR filter or a low-pass IIR filter may be used.

[0078] In the block diagram of the control unit 32 shown in FIG. 3, control (e.g., feedback control) that takes into account the storage battery capacity is not performed. If the calculation shown in FIG. 3 is continued under such circumstances, the storage battery capacity may become inappropriate (e.g., over-discharge or over-charge), and the storage battery may operate abnormally. Therefore, for example, in the case of a power generation system related to solar power generation, control may be added to reset the SOC (State of Charge) of the storage battery to a target value (e.g., 100%) during sunset. In this way, when actually operating for a long period of time, various controls may be added to ensure stable operation of the power storage system (storage battery).

[0079] The control unit 32 may be configured to perform feedback of the battery capacity as needed. The block diagram shown in FIG. 9 is an example of a block diagram of a control unit 32X that performs feedback control of the battery capacity. The block diagram of the control unit 32X shown in FIG. 9 differs from the block diagram of the control unit 32 shown in FIG. 3 in the following respects. That is, an SOC target calculation unit 45 is provided after the smoothing filter 41 to the change rate limiter 44, and calculates a target value of the SOC of the battery based on the calculation result by the change rate limiter 44 (the combined output target value before the battery capacity correction). A difference between the target value calculated by the SOC target calculation unit 45 and the actual SOC of the power storage system 23 (the battery) is calculated, and a proportional gain 46 is applied to the result. This result is used as the combined output value after the battery capacity correction. Then, a saturator 47 that sets upper and lower limits based on the PCS capacity D1 and a change rate limiter 48 are applied again to the combined output value after the battery capacity correction, thereby obtaining a combined output target value r sys Calculate the combined output target value r sys The flow after calculation is the same as in Figure 3. That is, the combined output target value r sys , the charge / discharge power command value r bat is calculated, and based on this, the charge / discharge power command value r bat Charge and discharge power y according to bat As a result, the renewable energy generated power y reand the charge / discharge power y in the power storage system 23 bat The sum of these is the output power of microgrid 2, which is the composite output y sys This becomes:

[0080] Based on the block diagram shown in Figure 9, the composite output target value r sys When the target SOC calculation unit 45 is configured to calculate the target SOC, it is possible to adjust the combined output target value according to the SOC of the storage battery. For example, when the current SOC of the storage battery is 90%, it is desirable to avoid further charging of the storage battery. Therefore, by setting the target SOC calculated by the SOC target calculation unit 45 to, for example, 70%, and lowering the combined output target value based on the difference from the target SOC, it is possible to prevent further charging of the storage battery (correcting it in the direction of discharging) as much as possible. In this way, when feedback control according to the capacity of the storage battery is added, it is possible to use a storage battery with a smaller capacity and perform the operation described in the above embodiment.

[0081] In the example of the block diagram shown in Fig. 9, similarly to Fig. 3, the arrangement of the smoothing filter 41, the phase lead filter 42, the saturators 43 and 47, and the change rate limiters 44 and 48 may be partially changed or omitted. As described above, appropriate changes can be made from the viewpoint of calculating the uncorrected combined output target value and then correcting it according to the SOC of the storage battery. In this case, the saturators 43 and 47 and the change rate limiters 44 and 48 may be partially omitted.

[0082] Furthermore, in the above embodiment, the power generation system 21 and the power storage system 23 are connected by AC, but these parts may be connected by DC and controlled.

[0083] Furthermore, in the above embodiment, smoothing of power generation from renewable energy in a microgrid connected to an external grid was considered, but connection to an external grid is not necessarily required. For example, in an isolated environment isolated from the external grid, such as a remote island or rural area, a microgrid may be configured with an unstable generator (variable renewable energy generator) using renewable energy such as solar power and a stable generator such as a gas engine or diesel engine. In such cases, fluctuations in the power generated by the variable renewable energy generator must be absorbed by changing the output of the stable generator. In this case, frequent changes in the load on the stable generator can lead to equipment deterioration and failure. Furthermore, frequent changes in the load can reduce combustion efficiency and increase fuel consumption. Therefore, introducing a storage battery into the microgrid can be considered to smooth the power generated by the variable renewable energy generator. The smoothing process described in the above embodiment can be suitably used in the above-mentioned situation (equipment configuration).

[0084] [Hardware configuration] The hardware configuration of the control device 30 will be described with reference to Fig. 10. Fig. 10 is a diagram showing an example of the hardware configuration of the control device 30. The control device 30 includes one or more computers 100. The computer 100 has a CPU (Central Processing Unit) 101, a main memory unit 102, an auxiliary memory unit 103, a communication control unit 104, an input device 105, and an output device 106. The control device 30 is configured by one or more computers 100 configured by these pieces of hardware and software such as programs.

[0085] When the control device 30 is configured by multiple computers 100, these computers 100 may be connected locally or via a communication network such as the Internet or an intranet. This connection logically constructs a single control device 30.

[0086] The CPU 101 executes an operating system, application programs, etc. The main memory 102 is composed of a ROM (Read Only Memory) and a RAM (Random Access Memory). The auxiliary memory 103 is a storage medium composed of a hard disk, flash memory, etc. The auxiliary memory 103 generally stores a larger amount of data than the main memory 102. The communication control unit 104 is composed of a network card or a wireless communication module. At least a part of the communication unit 31 may be realized by the communication control unit 104. The input device 105 is composed of a keyboard, a mouse, a touch panel, a microphone for voice input, etc. The output device 106 is composed of a display, a printer, etc.

[0087] The auxiliary storage unit 103 stores in advance the program 110 and data necessary for processing. The program 110 causes the computer 100 to execute each functional element of the control device 30. The program 110 causes, for example, the processing related to the above-mentioned power adjustment method to be executed in the computer 100. For example, the program 110 is read by the CPU 101 or the main storage unit 102, and causes at least one of the CPU 101, the main storage unit 102, the auxiliary storage unit 103, the communication control unit 104, the input device 105, and the output device 106 to operate. For example, the program 110 reads and writes data from and to the main storage unit 102 and the auxiliary storage unit 103.

[0088] The program 110 may be provided in the form of being recorded on a tangible storage medium such as a CD-ROM, a DVD-ROM, a semiconductor memory, etc. The program 110 may also be provided as a data signal via a communication network.

[0089] [Effect] According to the power smoothing device (control device 30), power smoothing method, and power smoothing program described in the above embodiments, a composite output target value for the power output from the power supply system 1 is calculated by smoothing the power generated by the power generation system 21 as a power generation device with suppressed phase delay. Then, the charge / discharge power from the power storage device is calculated based on the composite output target value. By using this method, a composite output target value smoothed with suppressed phase delay is obtained, and charge / discharge power based on the composite output target value is commanded to the power storage device. Smoothing the composite output target value with suppressed phase delay reduces the difference between the composite output target value and the power generated by the power generation device. As a result, it becomes possible to smooth the output power of renewable energy while using a smaller-capacity power storage device. Furthermore, smoothing with suppressed phase delay can be achieved by simpler parameter adjustment than previously considered methods, making it easier to smooth the output power of renewable energy while using a smaller-capacity power storage device.

[0090] As described above, conventionally, studies have been conducted to smooth the power output from the power supply system 1 by setting a composite output target value in advance and correcting the phase lag when using the charging and discharging power of the power storage system 23. However, as described above, the use of a small-capacity, small-output power storage device can make adjustments difficult when smoothing the output power of renewable energy. Therefore, there is room for further improvement in achieving both a smaller capacity power storage device and smoothing the output power of renewable energy. In contrast, the method described in the above embodiment calculates the composite output target value by smoothing with a small phase lag itself. Therefore, the difference between the composite output target value and the power generated by the power generation device is reduced, thereby reducing the charging and discharging operation of the power storage device. Furthermore, smoothing with a small phase lag can be performed by simpler parameter adjustment than the method used in Patent Document 2. Therefore, the output power of renewable energy can be smoothed more easily using a smaller-capacity power storage device.

[0091] Smoothing with suppressed phase lag may be performed by combining smoothing and phase lead compensation. As an example, a smoothing filter 41 may be combined with a phase lead filter 42. By performing smoothing in this manner in combination with phase lead compensation, the phase lag is substantially suppressed, making it possible to reduce the difference between the combined output target value and the power generated by the power generation device.

[0092] Furthermore, the control unit 32 as a calculation unit may further correct the calculated combined output target value based on the capacity of the power storage device to calculate the charge / discharge power from the power storage device. Specifically, for example, as in the example of the block diagram in FIG. 9, a correction may be made using the difference between the target value calculated by the SOC target calculation unit 45 and the actual SOC of the power storage system 23 (storage battery). In this way, by further correcting the calculated combined output target value based on the capacity of the power storage device, it is possible to prevent commands from being issued to charge / discharge power under conditions that exceed the capacity of the power storage device. Therefore, it is possible to perform control taking the capacity of the power storage device into consideration.

[0093] The control unit 32 as a calculation unit may calculate the combined output target value based on the power generation capacity of the power generation device. For example, as described above, the saturator 43 may be used to perform correction taking into account the PCS capacity. With the above configuration, it is possible to perform control taking into account the power generation capacity of the power generation device.

[0094] The control unit 32 as a calculation unit may calculate the composite output target value so that the rate of change of the composite output target value falls within a predetermined range. For example, the rate of change of the composite output target value may be adjusted by applying the change rate limiter 44 as described above. When it is necessary to control the rate of change of the power output from the power supply system 1, the above configuration makes it possible to adjust the composite output target value and adjust the output power based on this.

[0095] [Note] This invention demonstrates a technology that can reduce variability, a problem with renewable energy, at low cost, and contributes to the widespread adoption and expansion of renewable energy. Therefore, this invention contributes to Goal 7 of the Sustainable Development Goals (SDGs) led by the United Nations, "Ensure access to affordable, reliable, sustainable and modern energy for all," and Goal 13, "Take urgent action to combat climate change and its impacts." [Explanation of symbols]

[0096] 1. Power supply system 2. Microgrid 21 Power generation system (power generation equipment) 23 Energy storage system (power storage device) 24 Connection 26. Received power measurement unit 27 Transmission power measurement unit 30 Control device (power smoothing device) 31 Communications Department 32,32X control unit 41 Smoothing Filter 42 Phase Lead Filter 43 Saturator 44 Change Rate Limiter 45 SOC target calculation department 46 Proportional Gain 47 Saturator 48 Change Rate Limiter 90 External power system

Claims

1. A power smoothing device that smooths power output from a power supply system including a power generation device that generates power using renewable energy and a power storage device, an acquisition unit that acquires information related to power generation by the power generation device; a calculation unit that applies one of a smoothing filter and a phase lead filter to the generated power, and further applies the other of the smoothing filter and the phase lead filter to the result of the application, thereby calculating a composite output target value for power to be output from the power supply system, and calculates a charge / discharge power command value for the power storage device by determining a difference between the composite output target value and the generated power; an output unit that outputs, to the power storage device, an operation command that specifies charge / discharge power according to the charge / discharge power command value based on a calculation result of the charge / discharge power command value; A power smoothing device having:

2. The power smoothing device according to claim 1 , wherein the calculation unit further corrects the calculated combined output target value based on a capacity of the power storage device to calculate the charge / discharge power from the power storage device.

3. The power smoothing device according to claim 1 , wherein the calculation unit calculates the combined output target value based also on a rated capacity of the power generation device.

4. 4. The power smoothing device according to claim 1, wherein the calculation unit calculates the combined output target value so that a rate of change of the combined output target value falls within a predetermined range.

5. A power smoothing method for smoothing power output from a power supply system including a power generation device that generates power using renewable energy and a power storage device, comprising: acquiring information related to power generation by the power generation device; applying one of a smoothing filter and a phase lead filter to the generated power, and further applying the other of the smoothing filter and the phase lead filter to the result of applying the smoothing filter to calculate a composite output target value for power to be output from the power supply system, and calculating a charge / discharge power command value for the power storage device by determining a difference between the composite output target value and the generated power; outputting, to the power storage device, an operation command specifying charge / discharge power according to the charge / discharge power command value based on a calculation result of the charge / discharge power command value; A power smoothing method comprising:

6. A power smoothing program that causes a computer to smooth power output from a power supply system including a power generation device that generates power using renewable energy and a power storage device, acquiring information related to power generation by the power generation device; applying one of a smoothing filter and a phase lead filter to the generated power, and further applying the other of the smoothing filter and the phase lead filter to the result of applying the smoothing filter to calculate a composite output target value for power to be output from the power supply system, and calculating a charge / discharge power command value for the power storage device by determining a difference between the composite output target value and the generated power; outputting, to the power storage device, an operation command specifying charge / discharge power according to the charge / discharge power command value based on a calculation result of the charge / discharge power command value; A power smoothing program that causes the computer to execute the above.

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