Power system

Abstract

To provide a power system that can continue to perform appropriate energy management even when the number of power devices changes. [Solution] The power system S1 includes a processing unit A1 which includes a command value calculation unit 21 that calculates an induction command value for setting the connection point power at the connection point with the power grid D to the target power, and a plurality of power control devices B1 to which power equipment Y can each be connected. Each of the plurality of power control devices B1 controls the output power of the connected power equipment Y based on a common induction command value input from the processing unit A1. In calculating the induction command value, the command value calculation unit 21 uses a value obtained by multiplying the difference between the value of the connection point power and the target power by a control gain. The processing unit A1 further includes an update unit 22 which updates the control gain according to the number of devices, which is the total number of power equipment Y connected to the plurality of power control devices B1. The update unit 22 updates the control gain when the number of devices rises from a state where it was below a first threshold to a state where it was above a first threshold.

Description

[Technical Field]

[0001] This disclosure relates to a power system for controlling connection point power at connection points with a power grid. [Background technology]

[0002] Power systems that manage multiple power devices (distributed power sources) connected to a power grid and control the reception of power from the power grid are becoming widespread. For example, Patent Document 1 discloses an example of a power system comprising a processing unit and multiple power control devices. The processing unit calculates an induction command value for controlling the connection point power to a target power. The connection point power is the power at the connection point between the power system and the power grid. Each power control device is connected to a corresponding power device (distributed power source). Each power control device controls the output power of the connected power device. Power devices include, for example, solar cells, storage batteries, and electric vehicles. Each power control device controls the output power in a distributed manner using the induction command value calculated by the processing unit. At this time, each power control device calculates a target value for the output power based on an optimization problem using the induction command value. Then, it controls the output power so that the output power becomes the target value. In such a power system, compared to a configuration in which the processing unit controls multiple power control devices collectively, the processing load on the processing unit does not increase significantly even if the number of power devices increases. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-150690 [Patent Document 2] Japanese Patent Publication No. 2015-166901 [Patent Document 3] Japanese Patent Publication No. 2018-121189 [Overview of the project] [Problems that the invention aims to solve]

[0004] In the power system described in Patent Document 1, the processing unit has a set value for calculating the induction command value. This set value is set in advance when the power system starts operation. Therefore, in conventional power systems, if the number of power devices changes, it may affect the energy management performed by the power system and may not be possible to perform optimal energy management.

[0005] This disclosure was conceived in view of the above circumstances, and its purpose is to provide a power system that can continue to perform appropriate energy management even when the number of power devices changes. [Means for solving the problem]

[0006] The power system provided by this disclosure is a power system for controlling connection point power at a connection point with a power grid, comprising: a processing unit including a command value calculation unit that calculates an induction command value for making the connection point power a target power; and a plurality of power control devices, each capable of connecting power equipment, wherein each of the plurality of power control devices controls the output power of the connected power equipment based on a common induction command value input from the processing unit, the command value calculation unit uses a value obtained by multiplying the difference between the value of the connection point power and the target power by a control gain in calculating the induction command value, the processing unit further includes an update unit that updates the control gain according to the number of devices, which is the total number of power equipment connected to the plurality of power control devices, and the update unit updates the control gain when the number of devices rises from a state below a first threshold to a state above the first threshold.

[0007] In a preferred embodiment of the power system, the update unit updates the control gain when the number of devices falls below a second threshold, which is smaller than the first threshold, from a state where the number of devices exceeds a second threshold that is smaller than the first threshold.

[0008] In a preferred embodiment of the power system, if the number of devices falls below the first threshold from a state where it was above the first threshold, the update unit does not update the control gain for a predetermined period after the number of devices falls below the first threshold, even if the number of devices falls below the second threshold.

[0009] In a preferred embodiment of the power system, the update unit includes a calculation unit that calculates a new control gain in updating the control gain using a number of calculation units corresponding to the number of devices, wherein the calculation unit uses the maximum number of power devices that can be connected to the plurality of power control devices as the number of calculation units when the number of devices goes from being below a first threshold to being above the first threshold, and uses a value smaller than the maximum number as the number of calculation units when the number of devices goes from being above a second threshold to being below the second threshold.

[0010] In a preferred embodiment of the power system, the control gain is defined as the control gain ε and the gain coefficient of the control gain ε is defined as ε Gain , the limit value of the induction command value is the induction command value limit pr lmt The total power control width is the sum of the individual power control widths, which are the maximum power outputtable power of the power equipment connected to each of the plurality of power control devices, and dP total The update interval of the induction command value is set to T S The calculation is performed according to the following formula (1), and the calculation unit uses the value obtained by multiplying the number of calculation units by the individual power control width as the total power control width if the individual power control width is the same, which is the maximum power that each power device connected to each of the plurality of power control devices can output.

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[0011] In the power system of the present disclosure, the processing device includes an update unit that updates the control gain. The update unit updates the control gain when the number of devices changes from a state below the first threshold to a state equal to or greater than the first threshold. According to this configuration, the control gain can be changed depending on whether the number of devices is large or small. As a result, if all conditions other than the number of devices are the same, the calculated induction command value can be changed depending on whether the number of devices is large or small. Therefore, the power system can continue to perform appropriate energy management even when the number of power devices changes.

Brief Description of Drawings

[0012] [Figure 1] It is a functional block diagram showing a power system according to an embodiment. [Figure 2] It is a flowchart showing the update process of the control gain performed by the update unit of the processing device of the power system shown in FIG. 1. [Figure 3] It is an image diagram showing an example of change in the control gain in the power system shown in FIG. 1. [Figure 4] It is an image diagram showing an example of change in the control gain in the power system according to a modification. [Figure 5] It is an image diagram showing an example of change in the control gain in the power system according to a modification. [Figure 6] It is a flowchart showing the update process of the control gain according to a modification.

Modes for Carrying Out the Invention

[0013] Preferred embodiments of the power system of the present disclosure will be described below with reference to the drawings. Hereinafter, the same or similar components will be denoted by the same reference numerals, and redundant descriptions will be omitted.

[0014] Figure 1 shows an example configuration of a power system S1 according to one embodiment of the present disclosure. As shown in the figure, the power system S1 comprises a power line 90, a processing unit A1, a plurality of power control devices B1, and a detection device C1. In Figure 1, thick lines represent the power network, and dashed lines represent the communication network.

[0015] Power system S1 controls power so that the connection point power becomes the target power through the coordinated operation of processing unit A1 and multiple power control devices B1. The target power is the target value (adjustment target value) of the connection point power. In power control of power system S1, processing unit A1 calculates an induction command value to control the connection point power to the target power (adjustment target value). The induction command value is common to all multiple power control devices B1. Each power control device B1 calculates the output target value of the controlled object (connected power equipment Y) based on the induction command value calculated by processing unit A1. Then, each power control device B1 controls the output power of the controlled object based on the calculated output target value. In this way, power system S1 controls the connection point power to the target power (adjustment target value) by having multiple power control devices B1 control the output power in a distributed manner. The induction command value is also used by each power control device B1 to calculate the output target value.

[0016] The power load L is supplied with power from the power system D and each power control device B1. The power load L includes general loads and critical loads. General loads include, for example, electrical equipment that is relatively unaffected even if the power is cut off during a disaster. Critical loads are important loads that need to be supplied with power continuously even during a disaster, and include, for example, emergency elevators, electrical equipment that requires continuous operation, and building lighting and air conditioning equipment. The power load L may also consist of either general loads or critical loads only.

[0017] The power line 90 is appropriately connected to the power system D, the power load L, and multiple power control devices B1. The power line 90 forms the power network in the power system S1.

[0018] The detection device C1 detects the connection point power. The detection device C1 includes a detection unit 81 and a communication unit 82. The detection unit 81 is installed between the connection point K and the power system D and detects the connection point power. The detection unit 81 is, for example, a power transducer. The detection unit 81 can communicate with the communication unit 82 and outputs the detected value of the connection point power to the communication unit 82. The communication unit 82 includes an AD converter that converts the detected value (analog value) of the connection point power input from the detection unit 81 into a digital value, and transmits the converted detected value (digital value) of the connection point power to the processing unit A1. The detection device C1 may also be equipped with various protective devices (e.g., reverse current relays, ground fault relays, reverse power relays, etc.) for connecting the power system S1 to the power system D, as appropriate.

[0019] Each of the multiple power control devices B1 is connected to connection point K. Each of the multiple power control devices B1 controls the output power of its own device based on an optimization problem using an induced command value. Each of the multiple power control devices B1 can be connected to a power device Y. Each of the multiple power control devices B1 controls the output power of its own device by controlling the output power or input power of the connected power device Y. Note that the input power corresponds to a negative value of output power. In the illustrated example, one power device Y is connected to one power control device B1, but multiple power devices Y may be connected to one power control device B1.

[0020] In the example shown in Figure 1, each power control device B1 is an EV station to which an electric vehicle is connected as a power device Y, and it charges and discharges the connected electric vehicle (specifically, the battery installed in the electric vehicle). In this disclosure, an electric vehicle refers to a vehicle that can run using an electric motor as a power source, and includes vehicles equipped with an internal combustion engine (e.g., plug-in hybrid vehicles). The electric motor operates using the power stored in the battery installed in the electric vehicle. Each power control device B1 (EV station) charges the electric vehicle by supplying power input from the connection point K to the power device Y (electric vehicle). In addition, each power control device B1 discharges the electric vehicle by outputting the power stored in the power device Y (electric vehicle) to the connection point K.

[0021] In this disclosure, each power control device B1 is not limited to an EV station to which an electric vehicle is connected as power equipment Y. For example, it may be a solar power PCS (Power Conditioning System) to which solar cells are connected as power equipment Y, a battery PCS to which a storage battery is connected as power equipment Y, a generator control device to which a generator is connected as power equipment Y, or a load control device to which a power load L is connected as power equipment Y. The solar power PCS controls the amount of power generated by the solar cells. The battery PCS controls the charging and discharging of the storage battery. The storage battery may be a secondary battery such as a lithium-ion battery, nickel-metal hydride battery, nickel-cadmium battery, or lead-acid battery, or a capacitor such as an electric double-layer capacitor. The generator control device controls the amount of power generated by the generator. The generator is, for example, one that converts the thermal energy of a fuel such as oil, coal, or gas into mechanical energy and generates electricity using that mechanical energy. The generator may also be a power generation device that utilizes renewable energy other than solar power (for example, wind power, hydropower, biomass, geothermal energy, etc.). While solar cells directly convert solar energy into electrical energy, generators first convert energy other than electrical energy into mechanical energy, and then convert that mechanical energy into electrical energy. A load control device controls the power load L connected to a detection device C1, and is used in, for example, a Building Energy Management System (BEMS) or a Factory Energy Management System (FEMS). Furthermore, the paired power control device B1 and power equipment Y may be covered by a common enclosure (not shown) and provided as a single device. For example, a battery as power equipment Y and an inverter device as power control device B1 may be provided in the body of an electric vehicle.

[0022] As shown in Figure 1, each of the multiple power control devices B1 includes a signal processing unit 11 and a power conversion unit 12. The signal processing unit 11 and power conversion unit 12 described below are common to each of the multiple power control devices B1 unless otherwise specified.

[0023] The signal processing unit 11 can communicate with the processing unit A1 and the connected power equipment Y (electric vehicle). The signal processing unit 11 receives an induction command value from the processing unit A1 and calculates the output target value of the power equipment Y based on an optimization problem using the received induction command value. This optimization problem includes an evaluation function and constraints. The evaluation function is the same as, for example, the one described in Patent Document 1. In this embodiment, the signal processing unit 11 performs the calculations of equations (2) and (3) below, which are derived from the evaluation function, similar to the description in Patent Document 1. In equations (2) and (3) below, P ref is the output target value of power control device B1, pr is the induction command value, pr lmt The `pr` parameter represents the induction command value limit, and `a1` to `a4` represent the design parameters. lmt The design parameters a1 to a4 are the same as those described in Patent Document 1. Then, similar to the description in Patent Document 1, the output target value is calculated by correcting the calculation result with constraints. Alternatively, the signal processing unit 11 may calculate the output target value by solving an evaluation function under constraints. The constraints are the same as those described in Patent Document 1. In this embodiment, the constraints set for the EV stand described in Patent Document 1 are set in the signal processing unit 11. The constraints set in the signal processing unit 11 may be changed as appropriate depending on the power equipment Y connected (for example, depending on the power equipment Y, they may be changed to the constraints set for the solar PCS described in Patent Document 1, the constraints set for the battery PCS described in Patent Document 1, etc.). The signal processing unit 11 outputs the calculated output target value to the power conversion unit 12.

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[0024] Furthermore, the signal processing unit 11 obtains the current individual power control width of the connected power equipment Y. The individual power control width is the power information that power equipment Y can output, and corresponds to the maximum output power of power equipment Y. If power equipment Y is a storage battery or an electric vehicle, for example, the individual power control width corresponds to the rated capacity. When power equipment Y is not degraded, the individual power control width will be, for example, the rated output specified for power equipment Y. On the other hand, when power equipment Y is degraded, it will be a value smaller than the rated output. Also, in the example where the power control device B1 is an EV station, the individual power control width will increase or decrease depending on the connected electric vehicle (power equipment Y). The signal processing unit 11 transmits the obtained individual power control width to the processing unit A1.

[0025] The power conversion unit 12 controls the output power or input power of the power device Y based on the output target value input from the signal processing unit 11. In this embodiment, the power conversion unit 12 controls the charging power or discharging power of the electric vehicle as the power device Y. In this disclosure, the power conversion unit 12 discharges the electric vehicle when the received output target value is positive, and charges the electric vehicle when the received output target value is negative.

[0026] The processing unit A1 can communicate with each of the multiple power control devices B1 and with the detection device C1. The processing unit A1 monitors the connection point power and calculates an induction command value to control the connection point power to a target power (adjustment target value). The target power (adjustment target value) is set to a value corresponding to the set control mode. The control mode is a setting that determines the system function of the power system S1. Control modes in the power system S1 include, for example, an output suppression mode that suppresses the output of connection point power, a schedule mode that controls connection point power at predetermined time intervals, a peak cut mode that suppresses power supplied from the power grid D, and a reverse power flow avoidance mode that controls connection point power to prevent reverse power flow. Control modes are not limited to these examples. For example, the target power may be set to a value pre-set in the processing unit A1, a value set by user operation, or a value instructed by a higher-level device (e.g., a power company), depending on the control mode. In addition, the connection point power may be a detected value detected by the detection device C1, or an estimated value calculated from the values ​​of each output power obtained by communication from each power control device B1. Furthermore, depending on the control mode set in the processing unit A1, either a detected value or an estimated value may be used as the connection point power. As shown in Figure 1, the processing unit A1 includes a command value calculation unit 21, an update unit 22, and a communication unit 24.

[0027] The communication unit 24 communicates with each of the multiple power control devices B1 and with the detection device C1. The communication unit 24 receives connection point power from the detection device C1 and individual power control widths from each power control device B1. The communication unit 24 also transmits induction command values ​​to each power control device B1.

[0028] The command value calculation unit 21 calculates the induction command value by performing calculations, for example, the following equations (4) and (5). In the following equations (4) and (5), pr is the induction command value, λp is the state variable, and P C∫ is the target power (active power), P is the current connection point power (active power), pr(t) is the induction command value, ε is the control gain, and Ts is the induction command value update interval. Note that equations (4) and (5) below are equivalent to the calculation formulas described in Patent Document 1. The command value calculation unit 21 uses the control gain ε input from the update unit 22 for the calculation of equations (4) and (5) below. In addition, for the calculation of equations (4) and (5) below, it receives the detected value of the connection point power from the detection device C1 via the communication unit 24 and reads the setting value stored in the aforementioned storage or the like. The setting value read by the command value calculation unit 21 includes the target power (adjustment target value), etc. The command value calculation unit 21 transmits the calculated induction command value to each power control device B1 via the communication unit 24.

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[0029] The update unit 22 updates the control gain according to the number of power control devices B1 that can participate in power control. The update unit 22 outputs the updated control gain to the command value calculation unit 21. As shown in Figure 1, the update unit 22 includes a device count detection unit 221 and a calculation unit 222.

[0030] The device number detection unit 221 detects the number of power devices Y connected to the power system S1. The power devices Y connected to the power system S1 are the power devices Y connected to the power control device B1 that can participate in power control. Hereinafter, this number may be referred to as the "device number". The device number detection unit 221 is, for example, one of the plurality of power control devices B1 that can communicate, and detects the number of those to which the power device Y (electric vehicle in this embodiment) is connected, thereby detecting the device number. In an example different from this configuration, at least one of the plurality of power control devices B1 may detect the device number, and the device number detection unit 221 may receive the device number information from the power control device B1 that has detected the device number. In this example, at least one of the plurality of power control devices B1 detects the device number by, for example, the method described in Patent Document 3. Specifically, each power control device B1 generates an internal value for calculating the number, and performs a consensus operation using the internal value, so that the internal value converges to the reciprocal of the number of the plurality of power control devices B1. The initial value of the internal value is set to "1" for any one of the plurality of power control devices B1, and "0" for the others. Thereby, in each of the plurality of power control devices B1, the internal value converges to the reciprocal of the number of the plurality of power control devices B1. Then, by taking the reciprocal of the converged internal value, the number of power devices Y (device number) connected to the plurality of power control devices B1 is calculated. Alternatively, at least one of the plurality of power control devices B1 may determine the number of the plurality of power control devices B1 from the number of those that can communicate with the other power control devices B1.

[0031] The calculation unit 222 calculates a control gain according to the device number. In this embodiment, the calculation unit 222 calculates the control gain when the device number is either greater than or equal to the first threshold value and less than or equal to the second threshold value, and does not calculate the control gain when the device number is greater than the second threshold value and less than the first threshold value. Here, the second threshold value is smaller than the first threshold value. The control gain ε is calculated, for example, by the following formula (6). In the following formula (6), ε Gain is a gain coefficient for adjusting the control gain ε, pr lmt is the induction command value limit, dP totaldP is the total power control width, and Ts is the update interval for the induced command value. total The value used is calculated by the following calculation. In the example where the individual power control width of each power device Y is the same, it is the value obtained by multiplying the number of calculation units by the individual power control width of each power device Y. The total power control width may also be the value obtained by multiplying the number of calculation units by the average value of the individual power control width of each power device Y. This average value of the individual power control width can be obtained, for example, by a consensus calculation using internal values ​​for the individual power control width by the calculation unit 222, or it may be calculated from the individual power control width received via the communication unit 24. For a consensus calculation using internal values ​​for the individual power control width, for example, the technical concept described in Patent Document 2 can be applied. The number of calculation units is a value used to calculate the total power control width and is a value corresponding to the number of devices. In this embodiment, when the number of devices is equal to or greater than the first threshold, the calculation unit 222 uses the maximum number of power devices Y that can be connected to the multiple power control devices B1 as the number of calculation units. When the number of devices is equal to or less than the second threshold, the first threshold is used as the number of calculation units. The examples of the number of calculation units are not limited to these. For example, when the number of devices is below the second threshold, the number of calculation units is not limited to the first threshold; it may be the second threshold, or a value different from the first and second thresholds (but less than the first threshold). Also, the first and second thresholds are not limited in any way, but if the maximum number of power devices Y that can be connected to multiple power control devices B1 is about 100, the first threshold is about 50 and the second threshold is about 40. Note that the total power control width dP when the number of devices is above the first threshold. total This value is not the product of the number of calculation units mentioned above and the individual power control width of each power device Y, but may also be the sum of the individual power control widths of each power device Y.

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[0032] In this embodiment, when the number of devices increases from below the second threshold to above the first threshold, the number of calculation units used by the calculation unit 222 changes, for example, from the first threshold to the maximum number of power devices Y. Therefore, the calculated control gain changes, and the update unit 22 updates the control gain. In this update, the overall power control width dP total As can be seen from the calculation example, as the number of calculation machines increases, the total power control width dP total As the value increases, the control gain ε is updated to a smaller value, as can be understood from equation (6) above. Also, when the number of devices decreases from above the first threshold to below the second threshold, the number of calculation units used by the calculation unit 222 changes from, for example, the maximum number of power devices Y to the first threshold. As a result, the calculated control gain changes, and the update unit 22 updates the control gain. In this update, the overall power control width dP total As can be seen from the calculation example, when the number of calculation machines decreases, the overall power control width dP total As this becomes smaller, the control gain ε is updated to a larger value, as can be understood from equation (6) above.

[0033] Figure 2 shows the control gain update process performed by the update unit 22. The update unit 22 repeatedly performs the update process shown in Figure 2. The period for performing the update process is not limited in any way. Before the update process is performed for the first time, the update unit 22 is pre-set with an initial value for the control gain. This initial value is not limited in any way, but for example, it is a value calculated with the number of calculation machines as the first threshold. In this disclosure, "less than a certain value A" means smaller than a certain value A, and "greater than a certain value A" means larger than a certain value A.

[0034] First, the update unit 22 determines whether the number of devices is equal to or greater than the first threshold (S101). If the update unit 22 determines in step S101 that the number of devices is equal to or greater than the first threshold (S101: YES), it calculates the control gain using the number of calculation units as the maximum number of connectable power devices Y (S102).

[0035] If the update unit 22 determines in step S101 that the number of devices is not equal to or less than the first threshold (i.e., it is below the first threshold) (S101: NO), it then determines whether the number of devices is equal to or less than the second threshold (S103). If the update unit 22 determines in step S103 that the number of devices is not equal to or less than the second threshold (i.e., it is above the second threshold) (S103: NO), it terminates the process without performing any control gain calculations. On the other hand, if the update unit 22 determines in step S103 that the number of devices is equal to or less than the second threshold (S103: YES), it calculates the control gain using the number of calculation devices as the first threshold (S104).

[0036] As shown in Figure 2, when the number of devices is below the second threshold, step S104 calculates the control gain using the number of calculation units as the first threshold. When the number of devices is above the first threshold, step S102 calculates the control gain using the number of calculation units as the maximum number of power devices Y. Therefore, the update of the control gain from the value calculated using the number of calculation units as the first threshold to the value calculated using the maximum number of calculation units occurs when the number of devices increases from below the first threshold to above the first threshold. On the other hand, the update of the control gain from the value calculated using the maximum number of calculation units to the value calculated using the first threshold occurs when the number of devices decreases from above the second threshold to below the second threshold.

[0037] Note that the update process shown in Figure 2 is not limited to the illustrated example. For example, in step S104, the update unit 22 may calculate the control gain using the number of calculation units as the second threshold instead of the first threshold. Also, in steps S102 and S104, instead of calculating the control gain, a value that has been calculated in advance and stored in a storage unit (not shown) may be used as the control gain.

[0038] Figure 3 shows an example of the change in control gain in power system S1. Figure 3(a) shows an image of the change in control gain when the number of devices increases, and Figure 3(b) shows an image of the change in control gain when the number of devices decreases. In Figures 3(a) and (b), the solid line shows the period of the control gain calculated when the number of calculation units is the maximum number of connectable power devices Y (the period when the control gain is the first gain value), and the dashed line shows the period of the control gain calculated when the number of calculation units is the second threshold (the period when the control gain is the second gain value). As can be understood from equation (5) above, the first gain value is smaller than the second gain value.

[0039] When the number of devices increases, as shown in Figure 3(a), the control gain is updated from the second gain value to the first gain value when the number of devices rises from below the first threshold to above the first threshold. On the other hand, when the number of devices decreases, as shown in Figure 3(b), the control gain is updated from the first gain value to the second gain value when the number of devices falls below the second threshold from above the second threshold. Also, as can be seen from Figure 3, in power system S1, the change from the second gain value to the first gain value occurs when the number of devices rises to above the first threshold. On the other hand, the change from the first gain value to the second gain value occurs when the number of devices falls below the second threshold. Therefore, the first gain value and the second gain value are changed by different thresholds when the number of devices increases and when the number of devices decreases.

[0040] In the power system S1 configured as described above, the processing unit A1 includes an update unit 22 that updates the control gain. The update unit 22 updates the control gain when the number of devices (the total number of power devices Y connected to multiple power control devices B1 and capable of controlling the power at connection points) rises above a first threshold from a state below a first threshold. With this configuration, the control gain can be changed depending on whether the number of devices is large or small. In a configuration different from power system S1, where the control gain is not updated, the value of the control gain is the same regardless of whether the number of power devices Y is large or small. In this configuration, the larger the number of power devices Y (total number of devices) (i.e., the more power control devices B1 participating in power control), the larger the change in power at connection points in response to a change in the induction command value. Conversely, the smaller the number of power devices Y (total number of devices) (i.e., the fewer power control devices B1 participating in power control), the smaller the change in power at connection points in response to a change in the induction command value. Therefore, if the number of power devices Y is large, the power at the connection point may become unstable near the target power during power control, and if the number of power devices Y is small, the time it takes for the power at the connection point to converge to the target power may be long during power control. In contrast, power system S1 can calculate an induction command value corresponding to the number of devices by updating the control gain when the number of devices rises above the first threshold from a state below the first threshold. As a result, assuming all conditions other than the number of devices are the same, the calculated induction command value can be changed between the case where there are many devices and the case where there are few devices, thereby reducing the difference in the change of power at the connection point. In other words, it is possible to suppress the instability in power control that occurs when there are many power devices Y, while reducing the time it takes to converge when there are few power devices Y. Therefore, power system S1 can continue to perform appropriate energy management even when the number of power devices Y changes.

[0041] Furthermore, in configurations different from power system S1, it is possible to update the control gain each time the number of devices changes (or at predetermined intervals). However, if there are many power control devices B1 that can be connected to connection point K, the number of devices may change frequently. For example, if power system S1 is a large-scale EV charging station, it may be equipped with tens or hundreds of EV stands as power control devices B1. In such a charging station, electric vehicles as power devices Y are frequently connected and disconnected. In this case, the control gain changes frequently, and the induction command value also changes due to this change in control gain, which can make the power control of power system S1 unstable. On the other hand, in power system S1, the control gain is changed in stages (in this embodiment, in two stages: a first gain value and a second gain value) according to the number of devices, so frequent control of the control gain can be suppressed. In other words, power system S1 can suppress power control instability caused by frequent changes in the number of devices.

[0042] In the power system S1, the update unit 22 updates the control gain when the number of devices falls below the second threshold from a state where it exceeds the second threshold. With this configuration, the threshold for switching the control gain to the first gain value (first threshold) can be changed by an increase in the number of devices, and the threshold for switching the control gain to the second gain value (second threshold) can be changed by a decrease in the number of devices. As can be understood from equations (4) and (5) above, when the control gain changes, the induction command value also changes. In particular, in this embodiment, when the control gain increases, the induction command value increases. When the induction command value increases, as can be understood from equations (2) and (3) above, the device target (absolute value) calculated by each power control device B1 increases. In other words, when there are many devices, increasing the control gain can lead to large changes in connection point power, and power control that uses connection point power as the target power may become unstable. Therefore, in power system S1, when the number of devices decreases from a state where it is above the first threshold, the control gain is updated (increased) when it falls below the second threshold (a value smaller than the first threshold), rather than the first threshold. This ensures that the control gain is updated when the number of devices falls below the first threshold. This suppresses excessive changes in connection point power. In other words, in power system S1, by changing the threshold for updating the control gain due to an increase in the number of devices (first threshold) and the threshold for updating the control gain due to a decrease in the number of devices (second threshold), instability in connection point power control can be suppressed.

[0043] In the power system S1, the update unit 22 includes a calculation unit 222 that calculates a new control gain using a number of calculation units corresponding to the number of devices when updating the control gain. The calculation unit 222 uses the maximum number of power devices Y as the number of calculation units when the number of devices rises from below a first threshold to above a first threshold, and uses a value smaller than the maximum number of power devices Y (the first threshold in this embodiment) as the number of calculation units when the number of devices falls from above a second threshold to below a second threshold. With this configuration, the value of the control gain can be changed depending on whether the number of power devices Y (total number of devices) is large or small.

[0044] In the power system S1, the control gain ε is calculated by equation (6) above. The calculation unit 222 uses the value obtained by multiplying the number of calculation units by the individual power control width of each power device Y, if the individual power control width of each power device Y connected to each of the multiple power control devices B1 is the same, as the total power control width. With this configuration, the control gain can be made smaller when there are many devices and larger when there are few devices. In other words, the power system S1 can calculate a control gain that is appropriate for the number of devices.

[0045] In the above embodiment, the update unit 22 is shown to switch the control gain between a first gain value and a second gain value depending on the number of devices. Unlike this example, the update unit 22 may be configured to switch between three or more gain values ​​depending on the number of devices. For example, Figures 4 and 5 show examples of how the control gain changes when switching between three gain values. In Figures 4 and 5, the solid line indicates the period when the control gain is the first gain value, the dashed line indicates the period when the control gain is the second gain value, and the dashed line indicates the period when the control gain is the third gain value. Note that the first gain value is smaller than the second gain value, and the second gain value is smaller than the third gain value. The number of calculation units for each of the first gain value, second gain value, and third gain value is shown below.

[0046] In the example shown in Figure 4, the control gain is updated as follows. First, when the number of devices increases, as shown in Figure 4(a), when the value rises from below the second threshold to above the second threshold, the control gain is updated from the third gain value to the second gain value. Subsequently, when the value rises from below the first threshold to above the first threshold, the control gain is updated from the second gain value to the first gain value. On the other hand, when the number of devices decreases, as shown in Figure 4(b), when the value falls from above the second threshold to below the second threshold, the control gain is updated from the first gain value to the second gain value. Subsequently, when the value falls from above the third threshold to below the third threshold, the control gain is updated from the second gain value to the third gain value. In the example shown in Figure 4, the first gain value is calculated using the maximum number of power devices Y that can be connected to multiple power control devices B1, the second gain value is calculated using the first threshold (or second threshold) for the number of calculation devices, and the third gain value is calculated using the second threshold (or third threshold) for the number of calculation devices.

[0047] In the example shown in Figure 5, the control gain is updated as follows. First, when the number of devices increases, as shown in Figure 5(a), when the value rises from below the third threshold to above the third threshold, the control gain is updated from the third gain value to the second gain value. Then, when the value rises from below the first threshold to above the first threshold, the control gain is updated from the second gain value to the first gain value. On the other hand, when the number of devices decreases, as shown in Figure 5(b), when the value falls from above the second threshold to below the second threshold, the control gain is updated from the first gain value to the second gain value. Then, when the value falls from above the fourth threshold to below the fourth threshold, the control gain is updated from the second gain value to the third gain value. In the example shown in Figure 5, the first gain value is calculated using the maximum number of power devices Y that can be connected to multiple power control devices B1, the second gain value is calculated using the first threshold (or second threshold) for the number of calculation devices, and the third gain value is calculated using the third threshold (or fourth threshold) for the number of calculation devices.

[0048] In the example shown in Figure 4, the threshold for updating to the second gain value when the number of devices increases and the threshold for updating to the second gain value when the number of devices decreases are the same value (second threshold). In contrast, in the example shown in Figure 5, the threshold for updating to the second gain value when the number of devices increases and the threshold for updating to the second gain value when the number of devices decreases are different values ​​(third threshold and second threshold). Thus, in a configuration that switches the control gain using three or more gain values, the threshold for updating to a certain gain value may be the same when the number of devices increases and when the number of devices decreases, or different thresholds may be used.

[0049] In an example different from the above embodiment, if the update unit 22 (calculation unit 222) updates the control gain due to a decrease in the number of devices, the following process of suspending the calculation of the control gain may be added. Specifically, the update unit 22 (calculation unit 222) may refrain from calculating (suspend) the control gain for a predetermined period after the number of devices falls below the first threshold, even if the number of devices falls below the second threshold. For example, the calculation unit 222 can be provided with a counter, and the elapsed period can be determined by the counting process of the counter. By adding the process of suspending the calculation of the control gain, changes to the control gain in a short period of time can be suppressed. Figure 6 shows the update process of the update unit 22 in this modified example. The update process shown in Figure 6 has the counting process of the counter added compared to the update process shown in Figure 2. Specifically, step S105 is performed instead of step S103, and steps S111, S112, and S113 are added.

[0050] In the update process shown in Figure 6, if the update unit 22 determines in step S101 that the number of devices is equal to or greater than the first threshold (S101: YES), it sets the counter value to "0 (zero)" (S111). Then it proceeds to the process in step S102. On the other hand, if the update unit 22 determines in step S101 that the number of devices is not equal to or greater than the first threshold (below the first threshold) (S101: NO), it determines whether the number of devices is equal to or less than the second threshold and whether the counter (value) is equal to or greater than a certain value (S105). This certain value can be appropriately set according to the predetermined period described above. In the process in step S105, if the update unit 22 determines that the number of devices is not equal to or less than the second threshold (above the second threshold) or that the counter is less than a certain value (S105: NO), it adds "1" to the counter value (increments the counter by +1) (S113). As a result, after the number of devices falls below the first threshold, the counter increases by 1 until the number of devices falls below the second threshold and the counter reaches a certain value or higher. Therefore, until a predetermined period has elapsed since the number of devices fell below the first threshold, the control gain calculation is not performed even if the number of devices falls below the second threshold. On the other hand, in the process of step S105, if the number of devices is below the second threshold and the counter is above a certain value (S105: YES), the value of the counter is set to a preset value (S112). This preset value is, for example, a value larger than the constant value used in the judgment of step S105. After that, the process of step S104 is performed.

[0051] Note that the update process shown in Figure 6 is not limited to the illustrated example, and for example, the process in step S112 may be omitted. Also, the process of suspending the calculation of the control gain described above is not limited to cases where the control gain switches between two gain values, but can also be applied when it switches between three or more gain values ​​(see Figures 4 and 5).

[0052] In an example different from the above embodiment, the update unit 22 (calculation unit 222) may calculate the control gain ε by the calculation of equation (7) below. In equation (7) below, dP maxdP is the maximum power adjustment range, and α is the ratio of the number of computing units. max This value is obtained by multiplying the maximum number of connectable power devices Y by the individual power control width of each power device Y, in an example where the individual power control widths of power devices Y that can be connected to multiple power control devices B1 are the same. max This may be the sum of the individual power control widths of each power device Y. The number of calculation units ratio α is the value obtained by dividing the number of calculation units by the maximum number of power devices Y that can be connected. In the above embodiment, when the number of devices is equal to or greater than the first threshold, the number of calculation units becomes the maximum number of power devices Y that can be connected, so the number of calculation units ratio α becomes 1. Even with such calculations, the control gain ε can be changed according to the number of devices.

number

[0053] In the above embodiment, assuming that the individual power control width of each power device Y is the same, the update unit 22 (calculation unit 222) used a value obtained by multiplying the number of calculation units by the individual power control width of each power device Y as the overall power control width. Unlike this example, if there are multiple individual power adjustment widths for each connectable power device Y, the overall power control width dP total This may be calculated by the following calculation. The update unit 22 (calculation unit 222) may calculate it by formula (8) below, where power equipment Y has the same individual power adjustment range, and power equipment Yi (where i is a positive integer). Here, if the number of calculation units is the maximum number of power equipment Y, the maximum number of power equipment Yi may be used as the number of power equipment Yi. If the number of calculation units is the first threshold (or second threshold, etc.), the maximum number of power equipment Yi may be multiplied by the ratio of the first threshold (or second threshold, etc.) to the maximum number of power equipment Y, and this result may be used as the number of power equipment Yi. dP total =Σ(Number of power devices Yi × Individual power adjustment range of power devices Yi)···(8)

[0054] In the above embodiment, the update unit 22 outputs the updated control gain to the command value calculation unit 21 when it updates the control gain. However, the embodiment is not limited to this, and the update unit 222 may output the updated control gain to the command value calculation unit 21 each time it calculates the control gain.

[0055] In the above embodiment, the calculation formula for the control gain ε is not limited to equation (6) above. For example, in the calculation using equation (6) above, the control gain ε becomes small when there are many devices and large when there are few devices. However, a different calculation formula from equation (6) above may be used so that the control gain ε becomes large when there are many devices and small when there are few devices. In this example, equations (4) and (5) above may be modified so that the induction command value pr becomes larger as the control gain ε becomes smaller, and conversely, the induction command value pr becomes smaller as the control gain ε becomes larger.

[0056] The power system relating to this disclosure is not limited to the embodiments described above. The specific configuration of each part of the power system relating to this disclosure can be modified in various ways. [Explanation of Symbols]

[0057] S1: Power system, A1: Processing unit, B1: Power control unit, D: Power grid, K: Connection point, Y: Power equipment, 21: Command value calculation unit, 22: Update unit, 222: Calculation unit

Claims

1. A power system that controls the connection point power at the connection point with the power grid, A processing device including a command value calculation unit that calculates an induction command value to make the connection point power a target power, Multiple power control devices, each capable of connecting to a power device, Equipped with, Each of the plurality of power control devices controls the output power of the connected power equipment based on a common induction command value input from the processing device. The command value calculation unit uses a value obtained by multiplying the difference between the connection point power value and the target power by the control gain when calculating the induction command value. The processing apparatus further includes an update unit that updates the control gain according to the number of devices, which is the total number of power devices connected to the plurality of power control devices. The update unit is a power system that updates the control gain when the number of devices rises from a state below a first threshold to a state above a first threshold.

2. The power system according to claim 1, wherein the update unit updates the control gain when the number of devices falls below a second threshold, which is smaller than the first threshold, from a state where it exceeds a second threshold that is smaller than the first threshold.

3. The power system according to claim 2, wherein the update unit, when the number of devices falls below the first threshold from a state of being equal to or greater than the first threshold, does not update the control gain for a predetermined period after the number of devices falls below the first threshold, even if the number of devices falls below the second threshold.

4. The update unit includes a calculation unit that calculates the new control gain using a number of calculation units corresponding to the number of devices, in updating the control gain. The power system according to claim 2 or 3, wherein the calculation unit, when the number of devices falls below a first threshold, uses the maximum number of power devices that can be connected to the plurality of power control devices as the calculation unit, and when the number of devices falls below a second threshold, uses a value smaller than the maximum number as the calculation unit.

5. The control gain is defined as the control gain ε and the gain coefficient of the control gain ε. Ｇａｉｎ , the limit value of the induction command value is the induction command value limit pr ｌｍｔ dP ｔｏｔａｌ The update interval for the aforementioned induction command value is set to T Ｓ It is calculated using the following equation (1), The power system according to claim 4, wherein the calculation unit uses the value obtained by multiplying the number of calculation units by the individual power control width as the overall power control width when the individual power control width, which is the maximum power that can be output by the power equipment connected to each of the plurality of power control devices, is the same. [Math 1]

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