Battery control device and battery control method

Abstract

In the primary adjustment power supply operation of grid-connected batteries in the supply and demand adjustment market, this invention provides a battery control device that avoids interruptions due to insufficient charge and enables continuous supply over a long period of time. [Solution] The system includes a frequency monitoring unit that monitors the frequency from the power grid, a charge rate monitoring unit that monitors the charge rate of the storage battery, a target output correction unit that corrects the target output of the droop characteristic, which is the amount of output change per unit of frequency change at frequencies other than the dead zone, within the range of the upper limit droop characteristic and the lower limit droop characteristic, according to the charge rate, and a control unit that controls the charging or discharging of the storage battery with the target output corrected by the target output correction unit, wherein the target output correction unit corrects the target output toward the lower limit droop characteristic when the charge rate falls below a threshold, and / or corrects the target output toward the upper limit droop characteristic when the charge rate exceeds a threshold.

Description

[Technical Field]

[0001] The present invention relates to a battery control device and a battery control method. [Background Art]

[0002] In primary frequency control in the power supply and demand adjustment market, during the agreed block time, the battery measures the frequency of the power grid. When the frequency is greater than the reference grid frequency (e.g., 50 Hz), it charges; when it is less than the reference grid frequency, it discharges. As a result, the frequency of the power grid approaches the reference grid frequency, and the frequency deviation is reduced. By many batteries implementing the same control, it becomes possible to stabilize the frequency of the entire grid.

[0003] Since there is energy loss associated with charging and discharging in the battery, as the primary frequency control operation is carried out, the state of charge (SOC), which is the charge amount of the battery, gradually decreases. When the charge amount drops below a predetermined value, the supply of primary frequency control is interrupted, and it becomes necessary to charge to recover the charge amount, which leads to a decrease in the profitability of the battery and a decrease in the flexibility of the operation plan. In order to use grid-connected batteries more efficiently, it is necessary to suppress the decrease in SOC during the supply of primary frequency control.

[0004] Conventionally, as a technique for suppressing the decrease in SOC during the operation of primary frequency control, there is, for example, the one described in Patent Document 1. Patent Document 1 aims to provide a control device that can effectively prevent the remaining amount of the battery from becoming empty or fully charged. According to the charging rate of the battery, it changes the slope of the droop characteristic, which is the output change amount per frequency change amount at frequencies other than the dead band, and performs SOC recovery by substantial charging during the supply of primary frequency control. [Prior Art Documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent No. 7174178 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] To use storage batteries more efficiently, it is necessary to suppress the decline in State of Charge (SOC) during the supply of primary adjustment power. However, the charge and discharge output values ​​from storage batteries are subject to technical requirements set by trading markets such as the supply and demand adjustment market, which specify the allowable output range. For example, in the pre-screening requirements for primary adjustment power in the supply and demand adjustment market, the storage battery output at frequencies other than the dead zone is allowed to be within plus or minus 10% of the available storage battery capacity, with the adjustment rate curve, which is defined as the charge and discharge output value corresponding to the frequency deviation, as the median value. It is necessary that more than 90% of the measurement data during the evaluation period falls within this allowable range. In other words, both SOC recovery and keeping the charge and discharge output values ​​within the market's allowed output range are required.

[0007] In actual battery control, it is necessary to take a control margin on the safe side from the upper and lower limits of the output tolerance range, taking into account frequency measurement errors and response delays due to communication delays. If this control margin becomes excessive, it becomes difficult to secure a sufficient charge / discharge amount to recover the state of charge (SOC).

[0008] The technology described in Patent Document 1 discloses changing the slope of the droop characteristic, which is the amount of output change per unit of frequency change of the storage battery. However, this results in an excessively large control margin being secured for the output tolerance range of the primary adjustment power, which is within plus or minus 10% of the amount of storage battery that can be supplied. As a result, if primary adjustment power is supplied over a long period of time, there is a risk that the deterioration of the State of Charge (SOC) will not be suppressed. Thus, the existing Patent Document 1 had the problem of difficulty in achieving both SOC recovery and compliance with technical requirements, taking into account the shape of the output tolerance range set by the market.

[0009] In view of the above problems, the object of the present invention is to provide a battery control device and a battery control method that maximize the amount of State of Charge (SOC) recovery while conforming to the output tolerance range set by the market. [Means for solving the problem]

[0010] To achieve the above objective, the battery control device of the present invention comprises: a frequency monitoring unit that monitors the frequency from the power grid; a charge rate monitoring unit that monitors the charge rate of the battery; a target output of the droop characteristic, which is the amount of output change per unit of frequency change at frequencies other than the dead zone, according to the charge rate, within the range of the upper limit droop characteristic and the lower limit droop characteristic; and a control unit that controls the charging or discharging of the battery with the target output corrected by the target output correction unit, wherein the target output correction unit corrects the target output toward the lower limit droop characteristic when the charge rate falls below a threshold, and / or corrects the target output toward the upper limit droop characteristic when the charge rate exceeds a threshold. Other embodiments of the present invention will be described in the embodiments described below. [Effects of the Invention]

[0011] According to the present invention, it is possible to maximize the amount of SOC recovery while conforming to the market-defined output tolerance range. [Brief explanation of the drawing]

[0012] [Figure 1] This figure shows an example of an overall configuration including a grid-connected battery in a conventional example. [Figure 2] This figure shows the droop characteristics of the primary adjustment force in a conventional supply and demand adjustment market. [Figure 3] This figure shows the frequency measurement results and charge / discharge output of the primary adjustment force in a conventional supply and demand adjustment market. [Figure 4] This figure shows the results of the primary adjustment force provided by the supply and demand adjustment market in a conventional example. [Figure 5] This figure shows the functional configuration of a battery control device according to the first embodiment of the present invention. [Figure 6] This flowchart shows an example of a battery control method when performing steady-state output correction according to the first embodiment of the present invention. [Figure 7] A table showing an example of the battery output value when performing steady-state output correction according to the first embodiment of the present invention. [Figure 8] A diagram showing the droop characteristics when performing steady-state output correction according to the first embodiment of the present invention. [Figure 9] A diagram showing the control margin when performing steady-state output correction according to the first embodiment of the present invention. [Figure 10] A flowchart showing an example of a battery control method when performing steady-state and transient output corrections according to the second embodiment of the present invention. [Figure 11] A diagram showing the droop characteristics when performing steady-state and transient output corrections according to the second embodiment of the present invention. [Figure 12] A diagram showing the control margin when performing steady-state and transient output corrections according to the second embodiment of the present invention. [Figure 13] A diagram showing the charge / discharge output when performing steady-state and transient output corrections according to the second embodiment of the present invention. [Figure 14] A diagram showing the effects according to the second embodiment of the present invention. [Figure 15] A diagram showing the charge / discharge output in the dead zone according to the third embodiment of the present invention. [Figure 16] A diagram showing the charge / discharge output near the outside of the dead zone according to the third embodiment of the present invention. [Figure 17] A diagram showing the charge / discharge output considering auxiliary machine losses according to the third embodiment of the present invention. [Figure 18] A diagram showing the charge / discharge output during power supply to other markets by the battery according to the third embodiment of the present invention. [Figure 19] A diagram showing the hardware configuration of the battery control device according to the embodiment. [Figure 20] A diagram showing an example of the functional configuration of the battery control device according to the embodiment.

Modes for Carrying Out the Invention

[0013] Hereinafter, embodiments for carrying out the present invention will be described with reference to the accompanying drawings. In this specification and drawings, components having substantially the same function or configuration are denoted by the same reference numerals, and redundant descriptions are omitted.

[0014] First, we will explain the conventional example by referring to Figures 1 to 4. Figure 1 shows an example of the overall configuration including a grid-connected battery in a conventional example. The power station 2 where the grid-connected battery is installed is equipped with a control device 3, a power conditioner 4, and a battery 5, and is connected to the power grid 1 via the power conditioner 4. The battery 5 consists of a battery module 5a that can achieve desired output characteristics by connecting multiple battery cells in series or in parallel, and a battery management system (BMS) 5b. A lithium-ion battery is an example of a battery module 5a. The power conditioner 4 is controlled by the control device 3 and converts the power discharged from the battery 5 into power and discharges it to the power grid 1, or converts the power taken in from the power grid 1 into power and charges the battery 5.

[0015] While the above is described as the components of the power storage station 2, power generation equipment and demand equipment may be installed within the scope that allows for charging and discharging of the electricity stored in the battery 5 to the power grid 1. For example, renewable energy power generation equipment such as solar power generation equipment and wind power generation equipment, as well as power generation equipment such as gas engines, may be installed within the power storage station. Furthermore, demand equipment such as production equipment and office air conditioning, as well as electric vehicle charging and discharging equipment, may be installed within the power storage station.

[0016] Figure 2 shows the droop characteristics of the primary adjustment force in a conventional supply and demand adjustment market. The horizontal axis represents the frequency of the power system, and the vertical axis represents the charge / discharge output of the battery. The charge / discharge output is defined as follows: the positive side represents discharge from battery 5 to power system 1, and the negative side represents charging from power system 1 to battery 5. The reference frequency is set to 50 Hz. In primary adjustment force, a dead zone is set around the reference frequency where no charge / discharge output is required, and measured values ​​at times when the frequency is within the dead zone are excluded from the evaluation of primary adjustment force. If the upper and lower limits of the dead zone are F_thre_max and F_thre_min, respectively, then F_thre_max is set to 50.01 Hz and F_thre_min is set to 49.99 Hz, for example.

[0017] When the frequency is outside the dead zone, the battery charges and discharges according to the adjustment rate curve of the charge / discharge output target value P_target. If the frequency is higher than the reference frequency, P_target becomes negative and charging is required. If the frequency is lower than the reference frequency, P_target becomes positive and discharging is required. The slope of the adjustment rate curve is determined by the adjustment rate; for example, if the adjustment rate is 5%, P_target is set so that it becomes the maximum output value of the battery when the frequency deviation deviates by 5% from the reference frequency.

[0018] For battery output at frequencies other than the dead zone, as mentioned above, an output tolerance range is set with an upper limit P_upper on the positive side and a lower limit P_lower on the negative side, using the adjustment rate curve, which is defined as the charge / discharge output value corresponding to the frequency deviation, as the median value. It is necessary that more than 90% of the measurement data during the evaluation period falls within this output tolerance range. The output tolerance range is set to within plus or minus 10% of the available battery supply, for example, as in Japan's supply and demand adjustment market. Alternatively, it may be set to within plus or minus 10% of the battery output at a certain frequency deviation, in which case the output tolerance range narrows as the frequency deviation approaches the dead zone.

[0019] Figure 3 shows the frequency measurement results and charge / discharge output of the primary adjustment force in a conventional supply and demand adjustment market. The upper part of Figure 3 shows the time change of the measured power frequency, which changes moment by moment due to fluctuations in power demand and supply. The lower part of Figure 3 shows the charge / discharge output from the storage battery based on the frequency measurement value and the adjustment rate curve. Charging occurs when the frequency in the upper part of Figure 3 is above 50Hz, and discharging occurs when it is below 50Hz. Note that when the frequency is near 50Hz, the charge / discharge output value becomes zero because it falls within the dead zone. Thus, excluding the dead zone, the frequency and charge / discharge output change values ​​in opposite phase relationships.

[0020] Figure 4 shows the results of primary adjustment power supply in a conventional supply and demand adjustment market. The horizontal axis represents frequency, and the vertical axis represents charge / discharge output. The y-axis values ​​of the upper and lower graphs in Figure 3 are plotted on a plane. The meaning of each parameter is the same as in Figure 2. The plotted measured values ​​do not match P_target due to frequency measurement errors and response delays caused by communication delays, but the fluctuation range of the plots is within the output tolerance range. In this figure, 100% of the plots outside the dead zone are within the output tolerance range, and the battery output results during this time period meet the technical requirements for primary adjustment power.

[0021] Furthermore, under the technical requirements known as Assessment II, the battery is required to have a slope sign that matches the slope sign of the approximation line on the plot. However, by keeping the charge / discharge output within the output tolerance range for 90% or more of the time, the slope requirement can generally be met. Therefore, here, whether or not the measured value plot falls within the output tolerance range is used to determine compliance with the technical requirements.

[0022] The following describes a battery control device according to an embodiment of the present invention. In each figure, common components are denoted by the same reference numeral.

[0023] <First Embodiment> Figure 5 shows the functional configuration of a battery control device 100 according to the first embodiment of the present invention. Similar to Figure 1, the power station 2 (see Figure 1) is equipped with a control device 3, a power conditioner 4, and a battery 5, and is connected to the power grid 1 via the power conditioner 4.

[0024] The battery storage system 5 consists of a battery module 5a and a battery management system (BMS) 5b. Inside the battery module 5a are an HV battery F14 (High Voltage battery) and a charge / discharge output unit F13 that performs charge / discharge output for the entire module. Inside the BMS 5b are a battery SOC measurement unit F16 that measures the current and voltage from the HV battery 14 to measure the state of charge (SOC), a battery SOC acquisition unit F1 that acquires the SOC measured by the battery SOC measurement unit F16, and a charge / discharge output control value receiving unit F15 (charge / discharge output control unit) that receives charge / discharge output control values ​​from the power conditioner 4 and causes the charge / discharge output unit F13 to perform charge / discharge.

[0025] Although not shown in the diagram, the HV battery F14 is equipped with a voltage measuring unit capable of detecting the voltage of the battery cells, a current measuring unit capable of detecting the current flowing through the battery cells, and a temperature measuring unit capable of detecting the temperature of the HV battery F14, in order to enable detection of its state. The voltage measuring unit is configured by attaching voltage lines between the battery cells so that the voltage of each terminal of the battery cell can be measured individually. The current measuring unit can detect the current by measuring the voltage of a shunt resistor, for example, but sensors such as Hall elements can also be used. Thermistors and thermocouples can be used for the temperature measuring unit.

[0026] Inside the power conditioner 4, there is a charge / discharge output command value receiving unit F11 that receives charge / discharge output command values ​​from the control device 3, and a charge / discharge output control value transmitting unit F12 that, considering the state of the battery based on the received command values, actually transmits the control value to the BMS 5b. The AC / DC power conversion unit F10 converts the DC output from the battery 5 to AC and provides AC output to the power system 1. The frequency measurement unit F9 measures the power frequency of the power system 1. Here, the frequency measurement unit F9 may measure the frequency at a point inside the power conditioner 4, or it may measure the frequency at the power receiving point of the power storage station 2. Furthermore, there is a frequency acquisition unit F2 that acquires the frequency, and a frequency change rate calculation unit F3 that calculates the rate of change of frequency over time.

[0027] The control device 3 is equipped with a base charge / discharge output calculation unit F4 that takes frequency as input, a steady-state output correction value calculation unit F5 that takes battery SOC and frequency as input, and a transient correction value calculation unit F6 that takes battery SOC, frequency and frequency change rate as input. It is further composed of a charge / discharge output command value calculation unit F7 that sums these three types of charge / discharge output values, and a charge / discharge output command value transmission unit F8 that sends this value to the power conditioner 4.

[0028] The battery control device 100 of this embodiment includes a frequency monitoring unit 31 that monitors the frequency from the power grid, a charge rate monitoring unit 32 that monitors the charge rate of the battery, a target output correction unit 33, and a control unit 34 that controls the charging or discharging of the battery based on the target output corrected by the target output correction unit 33. The target output correction unit 33 corrects the target output of the droop characteristic, which is the amount of output change per unit of frequency change at frequencies other than the dead zone, within the range of the upper limit droop characteristic and the lower limit droop characteristic, according to the charge rate.

[0029] The frequency monitoring unit 31 consists of a frequency measurement unit F9, a frequency acquisition unit F2, a frequency change rate calculation unit F3, and the like. The charge level monitoring unit 32 consists of a battery SOC measurement unit F16, a battery SOC acquisition unit F1, and the like. The target output correction unit 33 consists of a steady-state output correction value calculation unit F5, a transient correction value calculation unit F6, a charge / discharge output command value calculation unit F7, a charge / discharge output command value transmission unit F8, and the like. The control unit 34 consists of a charge / discharge output control value receiving unit F15.

[0030] Figure 19 is a diagram showing the hardware configuration of the battery control device 100 according to an embodiment. The control device 1200 shown in Figure 19 is one of the realization forms of the battery control device 100 shown in Figure 5. The control device 1200 includes a memory 1201, a processor 1202, a storage device 1203 such as an HD (Hard Disk), a communication unit 1204 such as a NIC (Network Interface Card), and a user interface unit 1205. As an example of a processor, a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit) can be considered, but other semiconductor devices may also be used as the main entity that performs predetermined processing.

[0031] Then, the program stored in the storage device 1203 is loaded into the memory 1201, and the loaded program is executed by the processor 1202. The control device 1200 may have a user interface unit 1205, which may include a display, touch panel, mouse, and keyboard.

[0032] Figure 20 shows an example of the functional configuration of the battery control device 100 according to the embodiment. As shown in Figure 20, the functions of each part, such as the frequency monitoring unit 31, the charge rate monitoring unit 32, the target output correction unit 33, and the control unit 34, are realized. In the following sections, a specific control method will be described using the battery control device 100 of this embodiment.

[0033] Figure 6 is a flowchart showing an example of a battery control method when performing steady-state output correction according to the first embodiment of the present invention. Here, the time step is set to 1 second, and is incremented by 1 second from the initial time t=0, so t=1, 2, 3, ... [seconds]. Each step will be described below.

[0034] In step S101, the battery control device 100 acquires the grid frequency f(t) and the remaining battery charge (SOC) (t) at time t. In step S102, the control device 3 determines whether the grid frequency f(t) is within the dead zone. If the result is No, the process proceeds to S103, where the base charge / discharge output value, which is the charge / discharge output value in the conventional example explained in Figures 2 to 4, is calculated based on the deviation between the grid frequency f(t) and the reference frequency. If the result of the determination in step S102 is Yes, the base charge / discharge output value is set to zero and the process proceeds to step S104.

[0035] In step S104, the battery control device 100 determines whether the remaining battery charge SOC(t) is within the SOC dead zone. Here, the SOC dead zone is the range in which the SOC is within a range suitable for primary adjustment power supply and no adjustment is required, and is set, for example, to SOC 45-55%. If the result of the determination in step S104 is No, the steady-state output correction value is calculated based on the deviation between the remaining battery charge SOC(t) and the reference SOC (step S105). If the result of the determination in step S104 is Yes, the steady-state output correction value is set to zero and the process proceeds to step S109.

[0036] In step S109, the battery control device 100 calculates the charge / discharge output value by adding the base charge / discharge output value (base value) and the steady-state output correction value (steady-state correction value), and then performs charging and discharging. If both the base charge / discharge output value and the steady-state output correction value are zero, it indicates that the battery will not operate. If the base charge / discharge output value is zero and the steady-state output correction value is not zero, it indicates that charging and discharging for adjusting the battery's SOC will be performed within the dead zone. In step S110, the battery control device 100 determines whether to continue supplying adjustment power at the next time step. If yes, it increments the time by one step and returns to step S101. If no, it terminates control.

[0037] Figure 7 is a table showing an example of battery output values ​​when steady-state output correction is performed according to the first embodiment of the present invention. This table shows charge and discharge output values ​​corresponding to frequency and battery SOC value. P_target is the base charge and discharge output value calculated in Figure 6, and is a value determined by the adjustment rate curve shown in Figure 4. α (α>0) and β (β>0) are steady-state output correction values ​​calculated in Figure 6, and are values ​​determined based on battery SOC as shown in this figure.

[0038] First, if the frequency is within the dead zone, the base charge / discharge output value is zero, as shown in the middle column. If the frequency is outside the dead zone, P_target is set as the base charge / discharge output value based on the adjustment rate curve in Figure 4. Next, if the battery SOC is within the dead zone, the steady-state output correction value is also zero, and the total charge / discharge output value is zero. If the battery SOC is slightly outside the dead zone, for example, SOC 30-45% or 55-70%, a steady-state output correction value α is set. Furthermore, if the deviation of the battery SOC widens to less than 30% or more than 70%, a steady-state output correction value β (β>α) is set. In other words, the larger the deviation of the battery SOC, the larger the steady-state output correction value is set to bring the battery SOC closer to 50% (threshold). Note that in the frequency dead zone, it is also possible to set the battery output value to zero regardless of the battery SOC value.

[0039] Here, the steady-state output correction value was changed in five stages based on the SOC value for the SOC dead zone. However, it is also possible to divide the SOC more finely and determine the steady-state output correction value more precisely. Alternatively, the divisions could be made coarser, so that if the battery SOC is outside the SOC dead zone, the same steady-state output correction value is always set regardless of the magnitude of the deviation from 50% (threshold) of the battery SOC.

[0040] Figure 8 shows the droop characteristics when steady-state output correction is performed according to the first embodiment of the present invention. It is an enlarged view of the area near the frequency of 49.92 Hz in Figure 4, and in this frequency band, the battery is required to discharge. Also, the frequency f(t) measured at time t is 49.92 Hz, and the battery SOC(t) is 40%, and since the battery SOC is below 50% (threshold), SOC recovery by charging is required.

[0041] First, P_target is set as the base charge / discharge output value based on the frequency, and is represented by point Pb in Figure 8. Next, a steady-state output correction value -α is set by referring to the battery SOC. The charge / discharge output value moves from Pb in the figure to point Ps, which is moved by the correction value ΔP1 (=-α).

[0042] In this case, since the battery is discharging, the downward movement of the output point within the allowable output range corresponds to reducing the amount of battery discharge while satisfying the technical requirements of the primary adjustment force, and leads to suppression of the decrease in battery SOC. Here, ΔP1 can be set to any value as long as Ps does not fall below P_lower, but considering frequency measurement errors and response delays due to communication delays, a control margin amount P_margin is set on the safe side from the upper and lower limits of the allowable output range. The method for determining the control margin is explained in Figure 9.

[0043] In this way, by setting the charge and discharge output values ​​based on frequency and battery SOC, so that the frequency approaches the reference frequency and the battery SOC approaches 50% (threshold), it is possible to suppress the decrease in battery SOC while providing primary adjustment power. This avoids interruptions due to insufficient charge in the primary adjustment power supply operation in the grid battery supply and demand adjustment market, and enables continuous supply over a long period of time.

[0044] In this control system, when a discharge request is made in the primary regulating power, the discharge amount is slightly reduced. While this may decrease the contribution to power system stabilization in the short term, it eliminates interruptions due to insufficient charge and provides stable regulating power over a long period, thus contributing to long-term power system stabilization. The aforementioned control system can also be applied to frequencies above 50Hz, i.e., when charging is required for the battery, using the same approach.

[0045] In other words, the battery control device 100 includes a frequency monitoring unit 31 that monitors the frequency from the power grid, a charge rate monitoring unit 32 that monitors the charge rate of the battery, a target output correction unit 33 that corrects the target output of the droop characteristic, which is the amount of output change per unit of frequency change at frequencies other than the dead zone, within the range of the upper limit droop characteristic and the lower limit droop characteristic, according to the charge rate, and a control unit 34 that controls the charging or discharging of the battery with the target output corrected by the target output correction unit. The target output correction unit 33 corrects the target output toward the lower limit droop characteristic if the charge rate falls below a threshold, and / or corrects the target output toward the upper limit droop characteristic if the charge rate exceeds a threshold.

[0046] The target output correction unit 33 corrects the target output towards the lower limit of the output droop characteristics if the charge rate falls below a threshold (e.g., 50%). Specifically, it increases the charge amount if the Hz is 50Hz or higher, and decreases the discharge amount if the Hz is below 50Hz. Furthermore, if the charge rate exceeds the threshold, the target output correction unit 33 corrects the target output towards the upper limit of the output droop characteristics. Specifically, it decreases the charge amount if the Hz is 50Hz or higher, and increases the discharge amount if the Hz is below 50Hz. This makes it possible to provide a charge / discharge control device that maximizes the SOC recovery amount while conforming to the output tolerance range set by the market. In other words, in the primary adjustment power supply operation in the supply and demand adjustment market for grid batteries, it is possible to avoid interruptions due to insufficient charge and enable continuous supply over a long period of time.

[0047] Figure 9 shows the control margin when performing steady-state output correction according to the first embodiment of the present invention. The control margin [%] is defined as the value obtained by dividing the control margin amount P_margin by the maximum available output P_contracted of the storage battery. Then, the minimum value of the control margin is 0%, in which case Ps lies on the boundary line of the output tolerance range (10%). The maximum value of the control margin is the same value as the width of the output tolerance range (10%), in which case Ps lies on the adjustment rate curve. The upper part of Figure 9 shows the time change of frequency, and the lower part of Figure 9 shows an example of setting the control margin for that. The control margin is set to a safety margin of 3% from the output tolerance range, regardless of frequency. This makes it possible to keep Ps stably within the output tolerance range even when the position of Ps, which is the charge / discharge output value, fluctuates due to frequency measurement errors or response delays due to communication delays. Furthermore, by determining the charge / discharge output value so as to secure a margin amount above a certain level from the boundary line of the output tolerance range, it becomes possible to perform optimal charge / discharge operation for any shape of output tolerance range defined by market technical requirements.

[0048] <Second Embodiment> Next, we will describe an embodiment that further enhances the effects of the present invention by performing transient output correction in addition to the steady-state output correction described above.

[0049] Figure 10 shows an example of the battery output value when performing steady-state and transient output correction according to the second embodiment of the present invention. The method for incrementing time t and steps S101 to S105 are the same as in Figure 6, so their explanation is omitted. In Figure 10, steps S106 to S108 are added compared to Figure 6. The control entity is the battery control device 100.

[0050] In step S106, the time variation of the system frequency Δf(t) = f(t) - f(t-1) is calculated. In step S107, it is determined whether the time variation of the system frequency Δf(t) is greater than a predetermined value. If the result of the determination in step S107 is Yes, the transient output correction value is calculated according to the method described later (step S108). If the result of the determination in step S107 is No, the transient output correction value is set to zero and the process proceeds to step S109A.

[0051] In step S109A, the charge / discharge output value is calculated by adding the base charge / discharge output value (base value), the steady-state output correction value (steady-state correction value), and the transient output correction value (transient correction value), and then charging and discharging are performed. In step S110, it is determined whether or not to continue supplying adjustment power at the next time step. If Yes, the time is incremented by one step and the process returns to step S101; if No, the control is terminated.

[0052] Figure 11 shows the droop characteristics when steady-state and transient output correction is performed according to the second embodiment of the present invention. It is an enlarged view of the vicinity of the frequency 49.92 Hz in Figure 4, and in this frequency band, the battery is required to discharge. Assume that the frequency f(t) measured at time t is 49.92 Hz and the battery SOC(t) is 40%. First, P_target is set as the base charge / discharge output value based on the frequency, and is represented by point Pb in Figure 11. Next, the steady-state output correction value -α is set by referring to the battery SOC. The charge / discharge output value moves from Pb in the figure to point Ps, which is moved by the correction value ΔP1 (=-α). Here, the time change amount of the grid frequency Δf(t)=f(t)-f(t-1) is calculated. Δf(t) may be the rate of change from the previous 1 second, or it may be the rate of change based on a time average over a period of about 30 seconds to 1 minute, depending on the rate of fluctuation of the grid frequency. If Δf(t)>0, the frequency is on an upward trend from time t-1 to time t.

[0053] Here, since many power devices are connected to the power grid, and there is a large inertia acting on the grid frequency, it is predicted that the frequency will continue to rise at the next time t+1. That is, in Figure 11, the lower output limit P_lower at time t is predicted to move towards the lower output limit corresponding to frequency f(t+1) over time t+1, and the allowable output range is predicted to change in the direction of expanding downwards. In the case of grid batteries, considering that there is a time delay of about 1 second from the transmission of command values ​​to the battery to the actual generation of battery output, it is possible to reduce the control margin at time t, perform transient output correction in the direction of decreasing the discharge amount by ΔP2, and move the charge / discharge output value to Pt, assuming an expansion of the allowable output range at time t+1.

[0054] Subsequently, the actual charge / discharge output reaches Pt around time t+1, and the lower limit of the output at that time, P_lower, has moved lower than at time t. Here, if we define the control margin P_margin as the difference between Ps, which is the steady-state output correction point at time t, and P_lower, which is expected to be the lower limit of the output at time t+1, and the dynamic control margin P_margin_dyn as the difference between Pt, which is the transient output correction point at time t, and P_lower, which is expected to be the lower limit of the output at time t+1, then it can be expressed as shown in equation (1).

[0055] ΔP2 = P_margin_dyn - P_margin … (1) The dynamic control margin P_margin_dyn is a realistic margin amount up to the lower limit of the output P_lower, taking into account the rate of change of frequency.

[0056] If the control margin P_margin is a constant 3% regardless of frequency, then when the rate of change of frequency is zero, the dynamic control margin P_margin_dyn and the control margin P_margin coincide and ΔP2 is zero. However, when the rate of change of frequency is positive, ΔP2 > 0. In the latter case, even if the charge / discharge output is corrected to a transient output correction point Pt ΔP2 lower than point Ps, the control margin P_margin is kept constant, thus reducing the risk of the charge / discharge output deviating from the output tolerance range.

[0057] In other words, by setting the control margin amount based not only on frequency and battery SOC, but also on the rate of change of frequency, it becomes possible to output the battery at a transient output correction Pt that further increases the charge amount (or decreases the discharge amount) compared to the steady-state output correction Ps that is performed based only on frequency and battery SOC.

[0058] In the battery control device 100 of this embodiment, the target output correction unit 33 predicts an increasing trend in frequency based on the rate of change of frequency and, if the charge level falls below a threshold, further corrects the target output toward the lower limit of the output droop characteristics, and / or predicts a decreasing trend in frequency based on the rate of change of frequency and, if the charge level exceeds a threshold, further corrects the target output toward the upper limit of the output droop characteristics.

[0059] In other words, the target output correction unit 33 predicts an increasing frequency trend based on the rate of change of frequency, and if the charge rate falls below a threshold (for example, 50%), it further corrects the target output toward the lower limit of the output droop characteristics. Specifically, it increases the charge amount if the frequency is 50Hz or higher, and decreases the discharge amount if it is below 50Hz. Furthermore, the target output correction unit 33 predicts a decreasing frequency trend based on the rate of change of frequency, and if the charge rate exceeds a threshold, it further corrects the target output toward the upper limit of the output droop characteristics. Specifically, it decreases the charge amount if the frequency is 50Hz or higher, and increases the discharge amount if it is below 50Hz.

[0060] In this way, by setting charge and discharge output values ​​based on frequency, battery SOC, and rate of change of frequency, it is possible to further suppress the decline in battery SOC while providing primary adjustment power. This avoids interruptions due to insufficient charge and enables continuous supply over long periods in the primary adjustment power supply operation in the grid battery supply and demand adjustment market.

[0061] Figure 12 shows the control margin when performing steady-state and transient output correction according to the second embodiment of the present invention. The dynamic control margin [%] is defined as the value obtained by dividing the dynamic control margin amount P_margin_dyn by the maximum available output P_contracted of the battery. The upper part of Figure 12 shows the time change of frequency, and the lower part of Figure 12 shows an example of setting the dynamic control margin for it. Here, a time average of 30 seconds is used as the rate of change of frequency. For the control margin amount (3%, fixed value) in the lower part of Figure 9, the dynamic control margin will exceed 3% during periods when the rate of change of frequency is positive. Transient output correction utilizes the portion of the control margin that exceeds 3% based on this rate of change of frequency to recover the state of charge of the battery.

[0062] Figure 13 shows the charge and discharge output when steady-state and transient output correction is performed according to the second embodiment of the present invention. Here, the battery SOC is around 40%, and the situation is such that charging is required. The figure also shows a time period in which the frequency gradually increases from below 50 Hz to above 50 Hz. The upper part of Figure 13 shows the time change of frequency, the middle part shows an example of setting the dynamic control margin for that frequency, and the lower part of Figure 13 shows Pb, the base value of the charge and discharge output, Ps, the value after steady-state correction, and Pt, the value after steady-state and transient correction. In the lower part of Figure 13, Pb ≥ Ps ≥ Pt, and by performing steady-state correction, steady-state correction, and transient correction, the charge and discharge output is corrected to the side where the battery is more charged.

[0063] Figure 14 shows the effects of the second embodiment of the present invention. It shows the time (operable time) from when the battery SOC is at 50% until it drops to 30% when primary adjustment power operation is performed. Compared to operation using Pb, which is the base value of charge / discharge output, the operable time increases when operation is performed using Ps, which is the value after steady-state correction. Furthermore, the operable time increases even further when operation is performed using Pt, which is the value after steady-state and transient correction. From this, it can be seen that the amount of SOC recovery can be maximized while conforming to the output tolerance range set by the market. In other words, in primary adjustment power supply operation in the supply and demand adjustment market for grid batteries, it is possible to avoid interruptions due to insufficient charge and enable continuous supply over a long period of time.

[0064] <Third Embodiment> Figure 15 shows the charge / discharge output in the dead zone according to the third embodiment of the present invention. As shown in Figure 2, in the primary adjustment power, a dead zone is set around the reference frequency where no charge / discharge output is required, and measured values ​​at times when the frequency is within the dead zone are excluded from the evaluation of the primary adjustment power. In this embodiment, the charge / discharge output is determined based on the battery SOC within the dead zone frequency range.

[0065] The charge / discharge output in the dead zone is set within a range of less than or equal to the upper output value P_upper and greater than or equal to the lower output value P_lower. Specifically, if the battery SOC is greater than 50% (threshold), the system operates to discharge in the dead zone to reduce the battery SOC. If the battery SOC is less than 50%, the system operates to charge in the dead zone to increase the battery SOC. The charge / discharge output in the dead zone may be determined solely by whether the battery SOC is greater than or less than 50%, as shown in Figure 15, or it may be set so that the correction value increases in steps as the deviation of the SOC from 50% increases. It is desirable that the maximum value of the charge / discharge output correction value be set to a value within the allowable range of the charge / discharge output on the dead zone boundary F_thre_max and F_thre_min in order to prevent the charge / discharge output from falling outside the allowable range even when the frequency suddenly changes from inside to outside the dead zone.

[0066] In other words, the battery control device of this embodiment is characterized in that, at dead-band frequencies, the target output correction unit 33 charges the battery if the charge rate falls below a threshold, and discharges the battery if the charge rate exceeds a threshold.

[0067] (Charge / discharge output near the outside of the dead zone) Figure 16 shows the charge / discharge output near the outside of the dead zone according to the third embodiment of the present invention. As a technical requirement for the primary adjustment force, when plotting frequency and charge / discharge output as shown in Figure 16 using measured values, the slope of the approximate line of the plot must be negative. That is, if quadrants 1 through 4 are defined as shown in Figure 16, the measured values ​​must mainly be located in the second and fourth quadrants.

[0068] However, if the frequency is higher than 50Hz and the battery SOC is higher than 50%, a positive correction may be applied to the reference value P_target, potentially causing the corrected battery output to be plotted in the first quadrant. Therefore, if the corrected battery output becomes positive when the frequency is higher than 50Hz and the battery SOC is higher than 50%, an additional correction is performed to make the battery output zero.

[0069] Furthermore, if the battery SOC is lower than 50%, a negative correction is applied to the reference value P_target, and the corrected battery output may be plotted in the third quadrant. Therefore, if the frequency is lower than 50Hz and the battery SOC is lower than 50%, and the corrected battery output becomes positive, an additional correction is applied so that the battery output becomes zero.

[0070] The battery control device 100 of this embodiment is characterized in that, when the power system frequency is lower than the reference frequency, the target output correction unit 33 does not perform charging if the charge / discharge output instruction value is for charging, and when the power system frequency is higher than the reference frequency, the charge / discharge output instruction value is for discharging if it does not perform discharging.

[0071] In this way, by avoiding plotting in the first and third quadrants in the frequency and charge / discharge output plot, the angle at which the slope of the approximate line of the plot becomes negative can be increased, making it possible to more reliably satisfy the technical requirements of the primary adjustment force.

[0072] (Charge / discharge output considering auxiliary equipment losses) Figure 17 shows the charge / discharge output considering auxiliary equipment losses according to the third embodiment of the present invention. Up to this point, the explanation has been based on the assumption that the power loss of the storage battery is zero. However, in reality, storage batteries have power losses due to charge / discharge losses, cable resistance losses, and auxiliary equipment losses. Therefore, in order to obtain the charge / discharge output results shown in Figure 16 at the measurement point, it is necessary to predict the power loss P_loss of the storage battery in advance and set the charge / discharge output command value to the charge / discharge output request value plus P_loss. In Figure 17, P_loss is added to the charge / discharge output diagram in Figure 4 so that the output of the storage battery becomes P_loss when the frequency is 50Hz.

[0073] In other words, the battery control device 100 of this embodiment is characterized in that the target output correction unit 33 predicts the amount of power loss of the battery system and auxiliary equipment and adds it to the charge / discharge output instruction value when calculating the charge / discharge output instruction value of the battery. As a result, by determining the charge / discharge output considering the actual power loss of the equipment, it becomes possible to control the charge / discharge output more accurately and to more reliably meet the technical requirements of primary adjustment power.

[0074] (Charge / discharge output while supplying power to other markets for storage batteries) Figure 18 shows the charge and discharge output of a battery according to the third embodiment of the present invention while it is supplying power to other markets. In addition to the supply and demand adjustment market, the battery may also discharge power to consumers installed at the same site as the battery, charge power from power generation equipment such as wind turbines and gas engines, and buy and sell power to the wholesale power market. This power supplied to markets other than the supply and demand adjustment market is called P_sell. In Figure 18, P_sell is added to the charge and discharge output diagram in Figure 4 so that the output of the battery becomes P_sell when the frequency is 50Hz.

[0075] The battery control device 100 of this embodiment is characterized in that, when the battery is simultaneously supplying power to a market other than the supply and demand adjustment market, the target output correction unit 33 sets the zero point of the charge and discharge output to the value of the amount of power supplied to a market other than the supply and demand adjustment market. This makes it possible to control the charge and discharge output more accurately by determining the charge and discharge output while taking into account the power supplied to a market other than the supply and demand adjustment market, and to more reliably meet the technical requirements of primary adjustment power.

[0076] Although lithium-ion batteries were described as an example in this embodiment, the method can also be applied to various other batteries such as lead-acid batteries, redox flow batteries, and all-solid-state batteries. It should be noted that the present invention is not limited to the embodiments described above, and various other applications and modifications can be taken as long as they do not deviate from the gist of the present invention as described in the claims. For example, the embodiments described above are detailed and specific explanations of the device configuration in order to clearly illustrate the present invention, and are not necessarily limited to having all the configurations described. Furthermore, it is possible to add, delete, or replace some of the configurations in these embodiments with other configurations. [Explanation of Symbols]

[0077] 1 Power system 2. Power storage station 3. Control device 4 Power Conditioner 5. Storage Battery 5a battery module 5bBMS(Battery Management System) 31 Frequency Monitoring Unit 32 Charging rate monitoring section 33 Target Output Correction Unit 34 Control Unit 100 Battery Control Device F1 Storage battery SOC acquisition department F2 frequency acquisition section F3 Frequency Change Rate Calculation Unit F4 Base Charge / Discharge Output Calculation Unit F5 Steady-state output correction value calculation unit F6 Transient Correction Value Calculation Unit F7 Charge / Discharge Output Command Value Calculation Unit F8 Charge / Discharge Output Command Value Transmission Unit F9 Frequency Measurement Section F10 AC / DC Power Conversion Unit F11 Charge / Discharge Output Command Value Receiving Unit F12 Charge / Discharge Output Control Value Transmission Unit F13 Charge / Discharge Output Section F14 HV battery F15 Charge / Discharge Output Control Value Receiving Unit (Charge / Discharge Output Control Unit) F16 Storage battery SOC measurement section P_target Charge / Discharge Output Target Value (Reference Value) P_upper Output upper limit P_lower Output lower limit P_margin: Control margin amount P_margin_dyn Dynamic control margin amount P_contracted Maximum deliverable output

Claims

1. A frequency monitoring unit that monitors frequencies from the power grid, A charge rate monitoring unit that monitors the charge rate of the storage battery, A target output correction unit corrects the target output of the droop characteristics, which is the amount of output change per unit of frequency change at frequencies other than the dead zone, according to the charge level, within the range of the upper limit droop characteristics and the lower limit droop characteristics. The system comprises a control unit that controls the charging or discharging of the battery based on the target output corrected by the target output correction unit, The target output correction unit corrects the target output toward the lower limit of the output droop characteristics if the charge rate falls below a threshold, and / or corrects the target output toward the upper limit of the output droop characteristics if the charge rate exceeds a threshold. A battery control device characterized by the following features.

2. A battery control device according to claim 1, The target output correction unit predicts an increasing trend in the frequency based on the rate of change of the frequency, and if the charge rate falls below a threshold, it further corrects the target output toward the lower limit of the output droop characteristics, and / or predicts a decreasing trend in the frequency based on the rate of change of the frequency, and if the charge rate exceeds a threshold, it further corrects the target output toward the upper limit of the output droop characteristics. A battery control device characterized by the following features.

3. A battery control device according to claim 1, At the frequency of the dead zone, The target output correction unit charges the battery if the charge level falls below a threshold, and discharges the battery if the charge level exceeds a threshold. A battery control device characterized by the following features.

4. A battery control device according to claim 2, The target output correction unit will not perform charging if the power system frequency is lower than the reference frequency and the charge / discharge output indication value is for charging, and will not perform discharging if the power system frequency is higher than the reference frequency and the charge / discharge output indication value is for discharging. A battery control device characterized by the following features.

5. A battery control device according to claim 1, The aforementioned target output correction unit predicts the amount of power loss from the battery system and auxiliary equipment when calculating the charge / discharge output instruction value of the storage battery, and adds it to the charge / discharge output instruction value. A battery control device characterized by the following features.

6. A battery control device according to claim 1, The aforementioned target output correction unit sets the zero point of the charge / discharge output to the value of the amount of electricity supplied to a market other than the supply and demand adjustment market when the battery is simultaneously supplying electricity to a market other than the supply and demand adjustment market. A battery control device characterized by the following features.

7. A frequency monitoring unit that monitors frequencies from the power grid, A charge rate monitoring unit that monitors the charge rate of the storage battery, A target output correction unit corrects the target output of the droop characteristics, which is the amount of output change per unit of frequency change at frequencies other than the dead zone, according to the charge level, within the range of the upper limit droop characteristics and the lower limit droop characteristics. A battery control method for a battery control device comprising: a control unit that controls the charging or discharging of the battery using the target output corrected by the target output correction unit; The target output correction unit corrects the target output toward the lower limit of the output droop characteristics if the charge rate falls below a threshold, and / or corrects the target output toward the upper limit of the output droop characteristics if the charge rate exceeds a threshold. A battery control method characterized by the following features.

8. A battery control method according to claim 7, The target output correction unit predicts an increasing trend in the frequency based on the rate of change of the frequency, and if the charge level falls below a threshold, it further corrects the target output toward the lower limit of the output droop characteristics, and / or predicts a decreasing trend in the frequency based on the rate of change of the frequency, and if the charge level exceeds a threshold, it further corrects the target output toward the upper limit of the output droop characteristics. A battery control method characterized by the following features.

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