Power System

Abstract

A power system is provided that can suppress node power from oscillating around a system target value. [Solution] A power system S1 is connected to a power grid and controls node power at a node with the power grid. The power system S1 includes a processing device A1 and multiple power control devices B1. Each of the multiple power control devices B1 calculates a induced command value from the difference between the node power and a system target value using control information generated by the processing device A1, and controls the output power of a corresponding power device using the calculated induced command value. The multiple power control devices B1 include a discrete control device B11 that switches between multiple control levels in response to changes in the induced command value, causing the output power of the corresponding power device to change discretely. When the discrete control device B11 detects the occurrence of chattering, which is repeated switching between two of the multiple control levels, it fixes the aforementioned difference to zero and calculates the induced command value.

Description

[Technical Field]

[0001] The present disclosure relates to an electric power system that is connected to an electric power grid and controls node power at a node with the electric power grid. [Background technology]

[0002] In recent years, power systems that manage multiple power devices connected to a power grid and control power transmitted and received between the power grid and the grid have become increasingly common. For example, Patent Document 1 discloses an example of a power system that includes a processing device and multiple power control devices and controls output power using an autonomous distributed cooperative control method. The processing device calculates a drivability command value for controlling the output power (connection point power) of the entire power system to a system target value. The multiple power control devices use the common drivability command value calculated by the processing device to calculate target values ​​for the output power of the power devices (solar cells, storage batteries, electric vehicles, generators, or power loads) based on their respective optimization problems. Then, the power control devices control the output power of the power devices to achieve the target values. Each power control device autonomously controls its output power based on the drivability command value, thereby controlling the output power (connection point power) of the entire power system to the system target value. In the power system described in Patent Document 1, the processing device simply calculates and transmits a drivability command value without understanding the status of each power control device, thereby reducing the computational and communication burden. Therefore, a high-performance, expensive processing device is not required, thereby reducing initial installation costs. Furthermore, when the power system is expanded, no major modifications to the processing equipment are required. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2020-150690 Summary of the Invention [Problem to be solved by the invention]

[0004] Power control devices whose controlled objects are solar cells or storage batteries use power conditioners to control output power. This allows for fine adjustment of output power, enabling the output power to be adjusted according to the equipment target value calculated from the induced command value. On the other hand, power control devices whose controlled objects are loads control output power by turning on and off at least one load. This results in discrete output adjustments based on the load's power consumption, making it impossible to adjust the output power in steps. This can lead to frequent switching between high and low output power states relative to the equipment target value, resulting in frequent on / off switching of the load. This can cause the node power to oscillate around the system target value. Furthermore, this oscillation also fluctuates the induced command value, affecting the entire power system. This is not limited to power control devices whose controlled objects are loads, but also applies to power systems equipped with power control devices that adjust output power discretely.

[0005] The present disclosure has been devised in view of the above circumstances, and has an object to provide a power system that can suppress node power from oscillating around a system target value. [Means for solving the problem]

[0006] A power system provided by a first aspect of the present disclosure is a power system connected to a power grid and controlling connection point power at a connection point with the power grid, comprising: a processing device that generates control information using the connection point power and a system target value that is a target for the connection point power; and a plurality of power control devices, each of which is associated with a power device and controls the output power of the corresponding power device, wherein each of the plurality of power control devices calculates an induction command value from the difference between the connection point power and the system target value using the control information generated by the processing device, and controls the output power of the corresponding power device using the calculated induction command value, and the plurality of power control devices include a discrete control device that switches between a plurality of control levels in accordance with changes in the induction command value, thereby causing the output power of the corresponding power device to change discretely, and when the discrete control device detects the occurrence of chattering, which is repeatedly switched between two of the plurality of control levels, it fixes the difference to zero and calculates the induction command value.

[0007] In a preferred embodiment of the power system, the discrete control device provides hysteresis to the criteria for switching the control levels when switching between the at least two control levels, and increases the width of the hysteresis when it detects the occurrence of chattering.

[0008] When the discrete control device detects the occurrence of chattering, it gradually changes the difference to zero.

[0009] In a preferred embodiment of the power system, the discrete control device detects the occurrence of chattering when the sign of the difference is reversed.

[0010] A power system provided by a second aspect of the present disclosure is a power system that is connected to a power grid and controls a connection point power at a connection point with the power grid, and includes a processing device that calculates an induced command value from the difference between the connection point power and a system target value that is a target for the connection point power, and a plurality of power control devices that are each associated with a power device and control the output power of the corresponding power device, wherein each of the plurality of power control devices controls the output power of the corresponding power device using the induced command value calculated by the processing device, and the plurality of power control devices includes a discrete control device that switches between a plurality of control levels in accordance with changes in the induced command value, thereby causing the output power of the corresponding power device to change discretely, and when the processing device detects the occurrence of chattering that repeatedly switches between two of the plurality of control levels, it fixes the induced command value. [Effects of the Invention]

[0011] According to the power system of the present disclosure, when chattering is detected, the discrete control device suppresses switching of the control level. For example, in the discrete control device, the difference between the node power and the system target value is fixed to zero, thereby fixing the induction command value and suppressing switching of the control level. Alternatively, the processor fixes the value of the induction command value to be transmitted, thereby suppressing switching of the control level in the discrete control device. Therefore, according to the power system of the present disclosure, chattering that may occur in the discrete control device can be suppressed, and oscillation of the node power around the system target value can be suppressed. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a diagram illustrating an example of the overall configuration of a power system according to a first embodiment. [Figure 2] 1 is a diagram illustrating an example of the configuration of a load control device of a power system according to a first embodiment. [Figure 3] FIG. 2 is a block diagram showing power control of the power system according to the first embodiment. [Figure 4]FIG. 4 is a diagram showing a simulation result when chattering control is not performed in the power system according to the first embodiment. [Figure 5] FIG. 4 is a diagram showing a simulation result when chattering control is performed in the power system according to the first embodiment. [Figure 6] 5 is a diagram showing an example of change when a differential value is changed to a set value in the power system according to the first embodiment. FIG. [Figure 7] FIG. 10 is a diagram illustrating another example of the configuration of a discrete control device. [Figure 8] FIG. 4 is a diagram showing a case where hysteresis is set for switching control levels in the power system according to the first embodiment. [Figure 9] FIG. 10 is a diagram illustrating an example of the overall configuration of a power system according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the power system of the present disclosure will be described below with reference to the accompanying drawings. In the following, identical or similar components will be designated by the same reference numerals, and redundant description will be omitted.

[0014] FIG. 1 shows an example of the overall configuration of a power system S1 according to the first embodiment. The power system S1 is connected to a power system E and can transmit and receive power from the power system E. The power system S1 controls output power using an autonomous distributed cooperative control method so that the power at the connection point between the power system S1 and the power system E (hereinafter referred to as "connection point power") becomes a system target value, which is the target of the connection point power. In the following description, when the power system S1 transmits power to the power system E (reverse power flow), the connection point power is taken to be a negative value. On the other hand, when the power system S1 receives power from the power system E, the connection point power is taken to be a positive value. As shown in FIG. 1, the power system S1 includes a processing device A1 and multiple power control devices B1. In FIG. 1, thick lines indicate power lines.

[0015] The power control performed by the power system S1 includes, for example, output reduction control, peak cutting control, reverse flow avoidance control, and schedule control. In output reduction control, the power output (power sold) from the power system S1 to the power grid E is reduced in accordance with an output reduction command issued by the power company. In peak cutting control, the peak value of the power supplied from the power grid E (power purchased) is reduced. In reverse flow avoidance control, the occurrence of reverse flow is reduced. In schedule control, the output power (connection point power) of the power system S1 is set to a power value set by the user. Note that the types of power control are not limited to these. The power system S1 performs one of these power controls depending on the control mode set in the processing device A1.

[0016] The processing device A1 can communicate with each of the multiple power control devices B1. This communication may be wireless or wired. The processing device A1 generates information (hereinafter referred to as "control information") for the multiple power control devices B1 to perform distributed power control. The processing device A1 transmits the generated information (control information) to each power control device B1. The control information is transmitted to the multiple power control devices B1 by multicast, for example, but may also be transmitted by broadcast (simultaneous transmission) or unicast. As shown in FIG. 1, the processing device A1 has a first acquisition unit 11, a second acquisition unit 12, and a generation unit 13.

[0017] The first acquisition unit 11 acquires the connection point power P(t). In this embodiment, the first acquisition unit 11 acquires the power value detected at the connection point (i.e., the measurement value of the connection point power) as the connection point power. Unlike this example, the first acquisition unit 11 may receive the detected values ​​of the output power of each power control device B1 and use an estimated value calculated from these detected values ​​as the connection point power.

[0018] The second acquisition unit 12 acquires the system target value Pc. For example, the second acquisition unit 12 acquires the system target value by receiving the system target value Pc from a computer (not shown) of a power company or a computer (not shown) that inputs settings of the processing device A1. Alternatively, the second acquisition unit 12 may acquire the system target value by reading out the system target value stored in a storage unit (not shown) provided in the processing device A1. The second acquisition unit 12 acquires the system target value according to the control mode set in the processing device A1.

[0019] The generation unit 13 generates control information using the connection point power P(t) acquired by the first acquisition unit 11 and the system target value Pc acquired by the second acquisition unit 12. In this embodiment, the generation unit 13 generates the difference between the connection point power and the system target value as control information. That is, the control information includes a difference value ΔP, which is the difference between the connection point power and the system target value. In this embodiment, the difference value ΔP is a value obtained by subtracting the system target value Pc from the connection point power P(t) (ΔP=P(t)−Pc). The generation unit 13 transmits the generated control information (difference value ΔP) to each power control device B1. Hereinafter, the difference value ΔP generated by the generation unit 13 (processing device A1) may be referred to as a “generated difference value ΔP′.”

[0020] Each of the power control devices B1 is associated with a power device X to be controlled. This association can be achieved by being connected by a power line (thick line in FIG. 1 ), or by being connected by wired or wireless communication. Each power control device B1 controls the power of the power device X to be controlled. Each of the power control devices B1 receives control information (generated differential value ΔP′) from the processing device A1, and calculates an induction command value using the received control information. Each power control device B1 calculates a target output power (hereinafter referred to as “device target value”) of the power device X to be controlled using the calculated induction command value. Then, the output power is controlled so that the output power of the power device X to be controlled becomes the device target value.

[0021] In the example shown in FIG. 1 , the multiple power control devices B1 include a photovoltaic power generation control device 20A connected to a solar cell SC as power equipment X, a storage battery control device 20B connected to a storage battery BT as power equipment X, and a load control device 20C connected to a customer facility L as power equipment X. The photovoltaic power generation control device 20A is, for example, a power conditioner, and controls the output power (generated power) of the solar cell SC connected via a power line. The storage battery control device 20B is, for example, a power conditioner, and controls the output power (charge / discharge power) of the storage battery BT connected via a power line. The load control device 20C controls the output power (power consumption) of the customer facility L connected via communication. Note that the power control device B1 is not limited to these, and for example, an electric vehicle control device connected to an electric vehicle as power equipment X, and a generator control device connected to a generator as power equipment X, etc. may be added to (or replaced by) the photovoltaic power generation control device 20A, the storage battery control device 20B, and the load control device 20C. The electric vehicle control device controls the output power (charging and discharging power) of the electric vehicle connected by the power line, and the generator control device controls the output power (generated power) of the generator (e.g., diesel generator, wind generator, hydroelectric generator, etc.) connected by the power line.

[0022] As shown in FIG. 1, each of the plurality of power control devices B1 (photovoltaic power generation control device 20A, storage battery control device 20B, and load control device 20C) includes a command value calculation unit 21, a target calculation unit 22, and a power control unit .

[0023] The command value calculation unit 21 receives control information and calculates a guiding command value using the received control information. The guiding command value is a value used by each power control device B1 to calculate an equipment target value. For example, the command value calculation unit 21 calculates the guiding command value pr by solving state equations (simultaneous differential equations) shown in the following equations (1) and (2). In the following equations (1) and (2), P(t) is the node power, Pc(t) is the system target value, λ is a state variable, pr is the guiding command value, and ε is a gradient coefficient. In this embodiment, the command value calculation unit 21 converts the generated differential value ΔP′ into a differential value ΔP used to calculate the guiding command value, and uses the converted differential value ΔP for P(t)-Pc(t) in the calculation of the following equations (1) and (2). Hereinafter, this converted differential value ΔP may be referred to as the “calculation differential value ΔP.” This state equation is set in each power control device B1. The command value calculation unit 21 of each power control device B1 commonly sets the following equations (1) and (2). Therefore, if the calculation difference value ΔP (=P(t)-Pc(t)) used in the following equations (1) and (2) is the same, the induced command value calculated in a distributed manner by each power control device B1 is common to the multiple power control devices B1. The command value calculation unit 21 calculates the induced command value every predetermined time (for example, 1 [sec]). The induced command value calculated by the command value calculation unit 21 is output to the target calculation unit 22.

number

[0024] The target calculation unit 22 calculates the equipment target value based on an optimization problem using the input guidance command value. This optimization problem includes an evaluation function and constraint conditions. The evaluation function is the same as that described in Patent Document 1, for example. In this embodiment, the target calculation unit 22 performs the calculations of the following equations (3) and (4) derived from the evaluation function, as described in Patent Document 1. In the following equations (3) and (4), P ref is the equipment target value of the power control device B1, pr is the induction command value, pr lmt is the induction command limit, and a1 to a4 are the design parameters. lmtand design parameters a1 to a4 are the same as those described in Patent Document 1. Then, as described in Patent Document 1, the calculation results are corrected using constraint conditions to calculate the equipment target values. The constraint conditions are the same as those described in Patent Document 1. Alternatively, the target calculation unit 22 may calculate the equipment target values ​​by solving an evaluation function under the constraint conditions. The induction command value calculated by the target calculation unit 22 is output to the power control unit 23.

number

[0025] The power control unit 23 controls the output power Pout of the power device X to be controlled so that the output power Pout of the power device X becomes equal to the input device target value. In the present disclosure, when the device target value is a negative value, power is output from the power device X to a power line connected to the power system E, and when the device target value is a positive value, power is output to the power device X from the power line connected to the power system E.

[0026] As described above, in the power system S1, the processing device A1 acquires the connection point power P(t) and the system target value Pc, and generates control information (the generated differential value ΔP′ in this embodiment). Then, the processing device A1 transmits the control information to each of the multiple power control devices B1. Each power control device B1 receives the control information (the generated differential value ΔP′) from the processing device A1, and uses the received control information to calculate a induced command value pr from the calculation differential value ΔP according to the preset state equations (the above equations (1) and (2)). Each power control device B1 uses the calculated induced command value pr to calculate the device target value P of the power device X to be controlled based on a preset optimization problem. ref Then, the output power Pout of the power device X to be controlled is calculated based on the device target value P ref Thus, the power system S1 performs power control so that the node power P(t) becomes the system target value Pc.

[0027] 2 shows an example configuration of the power control unit 23 of the load control device 20C and the customer facility L. As shown in FIG. 2, the customer facility L includes a distribution board L1 and a plurality of loads L2, and the power control unit 23 of the load control device 20C includes a comparison unit 231 and a control unit 232.

[0028] The distribution board L1 is connected to a power line connected to the power grid E and receives power via the power line. The power is then supplied to each load L2. The loads L2 are installed in buildings such as houses, apartments, stores, factories, warehouses, and buildings, and are, for example, air conditioning equipment and lighting equipment. Each load L2 is connected to the distribution board L1 and receives power from the distribution board L1. The operating state of each load L2 is individually adjusted by the load control device 20C. The output power (power consumption) Pout of the customer facility L is input to the load control device 20C. The output power Pout of the customer facility L may be detected collectively via the power line connected to the distribution board L1 (see FIG. 2), or may be calculated by detecting the power supplied to each load L2 individually and based on the detected values. The output power Pout of the customer facility L is a positive value when receiving power and a negative value when transmitting power. Because the customer facility L consumes (receives) power, the output power Pout of the customer facility L is a positive value. The customer facility L may include a power generation facility. In this case, the output power Pout of the customer facility L is the power consumed by each load L2 minus the power generated by the power generation facility.

[0029] The comparison unit 231 compares the device target value input from the target calculation unit 22 with the detected output power Pout at each predetermined control period, and outputs the comparison result to the control unit 232. ref The value obtained by subtracting the output power Pout from ref -Pout) as the comparison result. In this embodiment, the control period is set to, for example, 10 seconds. The set time of the control period is not limited. The control unit 232 adjusts the operating state of each load L2 based on the comparison result input from the comparison unit 231. The control unit 232 adjusts the operating state of each load L2 based on the comparison result input from the comparison unit 231. ref(if the comparison result is a negative value), the load L2 is turned off according to the difference. A priority order is set for each load L2. For example, loads L2 located in corridors, stairwells, or rooms that are not often used are set to a low priority order because turning them off does not have a significant impact. The control unit 232 sets the output power Pout to the device target value P in order of priority, starting from the load L2 with the lowest priority. ref The control unit 232 turns off the load L2 as much as necessary to increase the output power Pout (received power) to the device target value P ref (if the comparison result is a positive value), the load control device 20C turns on the loads L2 that are off, starting with the load L2 with the highest priority, according to the difference. Hereinafter, this operation will be referred to as a "reconnection operation." In other words, the load control device 20C controls the output power (power consumption) Pout of the customer facility L by adjusting the operating state of each load L2 through the disconnection or reconnection operation of multiple loads L2. In such processing by the load control device 20C, if the number of loads L2 to be turned on is defined as a control level, the load control device 20C controls the output power Pout of the customer facility L by switching the control level (the number of loads L2 that are on) in accordance with changes in the induction command value. For example, control level 0 means that no loads L2 are on, control level 1 means that one load L2 is on, and control level 3 means that three loads L2 are on. The higher the control level, the greater the number of loads L2 that are on, and therefore the greater the output power Pout (received power) of the customer facility L.

[0030] FIG. 3 is a block diagram showing power control in a power system S1. In the power control of the power system S1 shown in FIG. 3, the processing device A1 is the controller, each of the multiple power control devices B1 is the control target, the node power P(t) is the control variable, the system target value Pc is the set value, and the generated differential value ΔP′ (control information) is the manipulated variable. In this power control, as shown in FIG. 3, the processing device A1 transmits the generated differential value ΔP′ to each power control device B1. Each power control device B1 receives the generated differential value ΔP′ and controls the output power Pout of the power device X that is the control target based on the generated differential value ΔP′. The output power Pout output from each power control device B1 (each power device X) is summed at the node, and the sum is acquired by the processing device A1 as the node power P(t).

[0031] 3, in the power control of the power system S1, the multiple power control devices B1 (photovoltaic power generation control device 20A, storage battery control device 20B, and load control device 20C) are divided into a discrete control device B11 and a continuous control device B12. That is, the multiple power control devices B1 include the discrete control device B11 and the continuous control device B12.

[0032] The discrete control device B11 switches between multiple control levels in response to changes in the calculated induced command value pr, thereby causing the output power Pout of the power device X to change discretely. For example, the load control device 20C is a discrete control device B11. As described above, the load control device 20C controls the output power (power consumption) Pout of the customer facility L by adjusting the operating state of each load L2 through a shut-off operation or a restart operation, and therefore is unable to fine-tune the output power Pout. In other words, the load control device 20C causes the output power Pout of the power device X (customer facility L) to change discretely by switching the control level (the number of loads L2 that are on) in response to changes in the induced command value pr.

[0033] The continuous-type control device B12 changes the output power Pout of the power device X continuously (linearly) in accordance with the change in the calculated induction command value. For example, the photovoltaic power generation control device 20A and the storage battery control device 20B are each the continuous-type control device B12. The photovoltaic power generation control device 20A and the storage battery control device 20B each perform output power control using a power conditioner, and therefore can finely adjust the output power Pout of the corresponding power device X (solar cell SC or storage battery BT). For this reason, the device target value P calculated by the target calculation unit 22 ref In other words, in each of the photovoltaic power generation control device 20A and the storage battery control device 20B, the output power Pout of the power device X (photovoltaic battery SC or storage battery BT) to be controlled changes continuously in accordance with changes in the induction command value pr. Note that even if the photovoltaic power generation control device 20A, the storage battery control device 20B, the electric vehicle control device, and the generator control device are only capable of discretely controlling the output power Pout (for example, only capable of switching between on and off), they are configured as discrete-type control devices B11.

[0034] In the discrete control device B11, the output power Pout of the power device X to be controlled changes discretely, so that the output power Pout of the power device X to be controlled changes discretely. ref , and the output power Pout of the power device X to be controlled changes continuously. ref In other words, chattering does not occur in the continuous control device B12 as occurs in the discrete control device B11. Therefore, in the power system S1, the discrete control device B11 takes measures to suppress the occurrence of chattering.

[0035] As shown in FIG. 3, the command value calculation unit 21 of the discrete control device B11 includes an acquisition unit 211a, a countermeasure unit 212a, and a calculation unit 213a, and the command value calculation unit 21 of the continuous control device B12 includes an acquisition unit 211b and a calculation unit 213b.

[0036] In the command value calculation unit 21 of the continuous control device B12, the acquisition unit 211b receives the control information transmitted from the processing device A1 and acquires the control information (generated differential value ΔP′). Then, the acquired control information (generated differential value ΔP′) is output to the calculation unit 213b. The calculation unit 213b uses the input generated differential value ΔP′ as is as the calculation differential value ΔP to perform the calculations of the above equations (1) and (2). In this calculation, the calculation differential value ΔP is used for P(t)-Pc(t) in the above equation (1). The continuous control device B12 calculates the induced command value pr through such processing.

[0037] In response to this, in the command value calculation unit 21 of the discrete control device B11, the acquisition unit 211a receives the control information transmitted from the processing device A1 and acquires the control information (generated differential value ΔP′).Then, the acquired control information (generated differential value ΔP′) is output to the countermeasure unit 212a.

[0038] The countermeasure unit 212a monitors the generated differential value ΔP′ input from the acquisition unit 211a and detects the occurrence of chattering based on the generated differential value ΔP′. In this embodiment, the countermeasure unit 212a detects the occurrence of chattering when the positive / negative sign of the generated differential value ΔP′ is reversed. In this embodiment, the countermeasure unit 212a detects the occurrence of chattering when the positive / negative sign of the generated differential value ΔP′ is reversed for the first time. However, unlike this configuration, the countermeasure unit 212a may detect the occurrence of chattering when the positive / negative sign is reversed several times (for example, two or three times). Note that the method of detecting the occurrence of chattering is not limited to this. When the countermeasure unit 212a detects the occurrence of chattering, it outputs the calculation differential value ΔP having a value of 0 (zero) to the calculation unit 213a. After detecting the occurrence of chattering, the countermeasure unit 212a fixes the calculation differential value ΔP by setting the calculation differential value ΔP to 0 (zero) for a predetermined time (hereinafter referred to as the “difference value fixation time”). The difference value fixing time is set based on the demand time limit, for example, and is not limited to any specific value, but may be 30 minutes (for a single limit) or 15 minutes (half of the 30-minute single limit), etc. On the other hand, when the occurrence of chattering is not detected, the generated difference value ΔP′ input from the acquisition unit 211a is output to the calculation unit 213a as the calculation difference value ΔP as is.

[0039] The calculation unit 213a performs calculations of the above equations (1) and (2) using the input calculation difference value ΔP, similarly to the calculation unit 213b. When the countermeasure unit 212a detects the occurrence of chattering, the calculation difference value ΔP is fixed to 0 (zero), and therefore the induced command value pr calculated by the calculation unit 213a is fixed. This can be understood from the above equation (1). In other words, when the calculation difference value ΔP is fixed to 0 (zero), the calculation result of the above equation (1) becomes 0 (zero) (dλ / dt=0), and therefore the calculated induced command value pr does not change. As a result, the above chattering (when the output power Pout of the power device X to be controlled is equal to the device target value P refOn the other hand, when the countermeasure unit 212a does not detect the occurrence of chattering, the generated differential value ΔP′ acquired by the acquisition unit 211a is used as the calculation differential value ΔP as it is, and the guidance command value pr is calculated, as in the continuous type control device B12.

[0040] As described above, in the processing of the command value calculation unit 21 (i.e., calculation of the induced command value pr), the continuous control device B12 uses the generated differential value ΔP′ acquired from the processing device A1 as the calculation differential value ΔP without any change because chattering does not occur. However, the discrete control device B11 may experience chattering, so measures are taken to fix the calculation differential value ΔP depending on whether chattering occurs. Note that while the calculation differential value ΔP is fixed, the discrete control device B11 also fixes the induced command value. During this time, power control to match the node power P(t) to the system target value Pc is performed solely by the continuous control device B12. Therefore, the time for fixing the calculation differential value ΔP (difference value fixation time) represents a trade-off between suppressing chattering and the responsiveness required to match the node power P(t) to the system target value Pc. Therefore, the difference value fixation time is set within a range that suppresses frequent chattering while maintaining the aforementioned acceptable responsiveness. Furthermore, the difference value fixation time may be appropriately varied depending on the output status of the continuous control device B12 or the magnitude of the generated difference value ΔP′, etc. For example, the calculation difference value ΔP may be kept fixed until the absolute value of the generated difference value ΔP′ becomes equal to or greater than a certain value.

[0041] 4 and 5 show simulation results for the cases where the discrete control device B11 fixes the calculation difference value ΔP to 0 (zero) due to chattering (hereinafter referred to as "chattering control") and where it does not. FIG. 4 shows the simulation results without chattering control, and FIG. 5 shows the simulation results with chattering control. In each of FIGS. 4 and 5, (a) shows the time change of the node power P(t), (b) shows the time change of the control information (generated difference value ΔP') generated by the processing device A1 (generation unit 13), (c) shows the time change of the induction command value pr, and (d) shows the time change of the control level (the number of loads L2 turned on in the load control device 20C). The simulations in FIGS. 4 and 5 were performed under the following conditions. First, the power system in the simulation includes only one discrete control device B11. Therefore, changes in the output power Pout of the discrete control device B11 result in changes in the node power P(t). Second, the discrete control device B11 has four control levels 0 to 3, and the output power increases by 20 kW each time the control level increases. Third, from the start point until time t1, the uncontrollable output power (i.e., the output power at control level 0) is 120 kW, and after time t1, the uncontrollable output power (i.e., the output power at control level 0) is 130 kW. Therefore, until time t1, the output power Pout changes from 120 kW to 140 kW to 160 kW to 180 kW as the control levels are switched between 0, 1, 2, and 3, whereas after time t2, the output power Pout changes from 130 kW to 150 kW to 170 kW to 190 kW as the control levels are switched between 0, 1, 2, and 3. Fourth, the system target value Pc is 180 kW.

[0042] In the simulation shown in FIG. 4, at time t0, the control level is set to 3, the output power Pout is set to 180 kW, and the node power P(t) is set to 180 kW. As a result, this matches the system target value Pc, and the generation differential value ΔP' is set to 0. Thereafter, at time t1, when the uncontrollable output power (i.e., the output power at control level 0) changes, the output power Pout at control level 3 becomes 190 kW, and the node power P(t) also becomes 190 kW. As a result, the generation differential value ΔP' becomes 10 kW (190 kW - 180 kW), so in order to reduce the output power Pout (node ​​power P(t)), the control level is switched to 2 at time t2. However, when the control level is switched to 2, the output power Pout (node ​​power P(t)) becomes 170 kW, and the generation differential value ΔP' becomes -10 kW (170 kW - 180 kW). As a result, in order to increase the output power Pout (node ​​power P(t)), the control level is again switched to 3. In this way, after time t1, chattering occurs in which the control level repeatedly switches between 2 and 3.

[0043] In the simulation shown in FIG. 5, the simulation results from the start to time t2 are the same as those shown in FIG. 4, but the results after time t2 are different. In the simulation shown in FIG. 5, when the control level is switched to 2 at time t2, the positive / negative sign of the generated differential value ΔP′ is reversed (reversed from positive to negative). Therefore, in the discrete control device B11, the calculation differential value ΔP immediately after the positive / negative sign of the generated differential value ΔP′ is reversed is set to 0 (zero). In other words, at time t2, the calculation differential value ΔP is fixed to 0 (zero). As a result, the calculated induction command value pr does not change, and the connection point power P(t) does not change. Therefore, the generated differential value ΔP′ does not change from −10 kW (170 kW − 180 kW), and the state of control level 2 is maintained (the control level is not switched to 3). Therefore, it can be seen that the occurrence of chattering is suppressed in the power system S1.

[0044] The functions and effects of the power system S1 are as follows.

[0045] In the power system S1, the multiple power control devices B1 include a discrete control device B11. The discrete control device B11 switches between multiple control levels in response to changes in an induced command value, thereby discretely changing the output power of the corresponding power device X. For example, in the power system S1, the discrete control device B11 is a load control device 20C, and the output power of the customer facility L changes in response to the control level, with the number of loads L2 to be turned on being used as the control level. When the discrete control device B11 detects the occurrence of chattering, which repeatedly switches between two of the multiple control levels, it fixes the difference value ΔP used to calculate the induced command value (i.e., the calculation difference value ΔP) to 0 (zero) and calculates the induced command value. With this configuration, when chattering occurs, the calculation difference value ΔP is fixed to 0 (zero), and the calculated induced command value is fixed. This suppresses switching of the control level, thereby suppressing the occurrence of chattering. As mentioned above, this chattering is the cause of the node power P(t) oscillating around the system target value Pc. Therefore, the power system S1 can suppress the node power P(t) from oscillating around the system target value Pc.

[0046] In the power system S1, each power control device B1 calculates an induction command value from the difference (difference value ΔP) between the node power P(t) and the system target value Pc using control information received from the processing device A1, and controls the output power Pout of the power device X to be controlled. At this time, the discrete control device B11 adjusts the output power Pout by switching the control level in response to changes in the induction command value pr calculated from the calculation difference value ΔP. Therefore, in the discrete control device B11, chattering may occur when the control level is increased or decreased. This increase or decrease in the control level occurs when the positive or negative sign of the generated differential value ΔP' is reversed. Therefore, in the power system S1, the discrete control device B11 is configured to detect the occurrence of chattering when the positive or negative sign of the generated differential value ΔP' is reversed. In other words, in the power system S1, the discrete control device B11 can detect the occurrence of chattering by monitoring the generated differential value ΔP'.

[0047] In the power system S1, the multiple power control devices B1 include a continuous control device B12. With this configuration, if chattering occurs in the discrete control device B11 and the induction command value p r is fixed by the chattering control, the output power of the power device X, which is the control target of the discrete control device B11, becomes fixed. Therefore, if the power system is configured only with the discrete control device B11, the node power P(t) does not change during the fixed period, and power control to make the node power P(t) equal to the system target value Pc is temporarily interrupted. However, if the continuous control device B12 is included, the induction command value p r changes in the continuous control device B12, and the output power of the power device X, which is the control target of the continuous control device B12, is adjusted. This allows power control to be continuously performed to make the node power P(t) equal to the system target value Pc. In other words, in the power system S1 (configuration in which multiple power control devices B1 include a discrete control device B11 and a continuous control device B12), it is possible to set the connection point power P(t) to the system target value Pc even while suppressing the occurrence of chattering.

[0048] In the first embodiment, the processing device A1 transmits the differential value ΔP (generated differential value ΔP′) as the control information. However, unlike this configuration, the processing device A1 may transmit the node power P(t) (value) and the system target value Pc as the control information. In such a configuration, when each of the acquisition units 211a and 211b acquires the control information (node ​​power and system target value), it calculates the generated differential value ΔP′ using the acquired control information. Then, the acquisition unit 211a outputs the calculated generated differential value ΔP′ to the countermeasure unit 212a, while the acquisition unit 211b outputs the calculated generated differential value ΔP′ to the calculation unit 213b as the calculation differential value ΔP. This allows the above-mentioned chattering control to be performed, similarly to the power system S1.

[0049] In the first embodiment, when the countermeasure unit 212a detects the occurrence of chattering, it immediately sets the calculation difference value ΔP to 0 (zero) at the timing tx of the change, as shown in FIG. 6(a). Alternatively, as shown in FIG. 6(b), the calculation difference value ΔP may be gradually changed to 0 (zero) from the timing tx of the change. When the change is gradual, the change characteristic may be linear, as shown by the solid line in FIG. 6(b), or curved, as shown by the dashed-dotted line in FIG. 6(b) (the amount of change gradually decreases) or the dashed line in FIG. 6(b) (the amount of change gradually increases). Note that FIG. 6 illustrates a case in which the calculation difference value ΔP is changed from a value P1 greater than 0 (zero) to 0 (zero).

[0050] In the first embodiment, an example was shown in which the discrete control device B11 was the load control device 20C, but the discrete control device B11 is not limited to the load control device 20C. For example, FIG. 7 shows another configuration of the discrete control device B11. The discrete control device B11 shown in FIG. 7 controls the output power Pout by controlling a plurality of power devices X. Each of the plurality of power devices X switches between ON (a state in which power is output) and OFF (a state in which power is not output), and the output value cannot be controlled. Even with this configuration, the output power Pout changes discretely by switching the number of power devices X that are turned on as a control level.

[0051] In the first embodiment described above, the control level (the number of loads L2 to be turned on) is switched based on the difference between the calculated device target value and the output power Pout of the power device X (consumer facility L). However, the method of switching the control level is not limited to this and may be configured as follows. For example, the device target value may be associated with the control level, and the power control unit 23 may switch to the control level corresponding to the calculated device target value. In this example, the power control unit 23 of the discrete control device B11 may not include the comparison unit 231. For example, the control level may be switched so that the control level is set to 0 if the device target value is within a first range, and to 1 if the device target value is within a second range (the same applies to control level 2 and thereafter).

[0052] Alternatively, in another example of the control level switching method, since the equipment target value is calculated according to the induction command value, the induction command value and the control level may be associated with each other, and the power control unit 23 may switch to the control level corresponding to the calculated induction command value. In this example, the discrete control device B11 may not be provided with the target calculation unit 22. For example, the control level may be switched so that the control level is set to 0 if the induction command value is within a first range, and to 1 if the induction command value is within a second range (the same applies to control levels 2 and onward). For example, in an example in which the induction command value is associated with the control level, if there are four control levels 0, 1, 2, and 3, the induction command value pr may be set to a first threshold value pr th1 Less than (pr <pr th1 ), the control level is 0, and the guidance command value pr is equal to or greater than the first threshold value pr th1 Above second threshold pr th2 Less than (pr th1 ≦pr <pr th2 ), the control level is 1, and the guidance command value pr is equal to or greater than the second threshold value pr th2 Above the third threshold pr th3 Less than (pr th2 ≦pr <pr th3 ), the control level is 2, and the guidance command value pr is the third threshold value pr th3 End (pr th3 ≦pr), the control level is 3 (pr th1 <pr th2 <pr th3 ).

[0053] Furthermore, in a modified example of the control level switching method, hysteresis may be set when switching from a low control level to a high control level (when increasing the control level) and when switching from a high control level to a low control level (when decreasing the control level). For example, in an example in which the induction command value corresponds to the control level, as shown in FIG. 8(a), the switching threshold may be different when increasing the control level (thick solid line) and when decreasing the control level (thick dashed dotted line). Furthermore, in the power system S1 of the present disclosure, as shown in FIG. 8(b), the hysteresis width W may be increased when chattering is detected. This configuration further suppresses chattering, thereby further suppressing oscillation of the node power P(t) around the system target value Pc.

[0054] FIG. 9 shows a power system S2 according to the second embodiment. The power system S2 differs from the power system S1 in the following respects. First, in the power system S2, the processing device A1 calculates an induction command value. Second, in the power system S2, the processing device A1 detects the occurrence of chattering and takes measures to suppress the chattering.

[0055] The processing device A1 of the power system S2 calculates a guiding command value and transmits the calculated guiding command value to each power control device B1. The processing device A1 of the power system S2 includes a command value calculation unit 14 and a countermeasure unit 15.

[0056] The command value calculation unit 14 calculates the induced command value pr using the control information generated by the generation unit 13. The calculation method for the induced command value is the same as that of the command value calculation unit 21 of the power control device B1, and is calculated by the calculation of the above equations (1) and (2). At this time, the command value calculation unit 14 uses the generated differential value ΔP′ generated by the generation unit 13 for P(t)-Pc in the above equation (1). The command value calculation unit 14 outputs the calculated induced command value to the countermeasure unit 15 as a provisional value pr′.

[0057] The countermeasure unit 15 monitors the provisional value pr' of the induced command value input from the command value calculation unit 14 and detects the occurrence of chattering based on the provisional value pr' of the induced command value. In this embodiment, the countermeasure unit 15 detects the occurrence of chattering when the provisional value pr' of the induced command value changes from an increasing trend to a decreasing trend or from a decreasing trend to an increasing trend. Note that the method of detecting the occurrence of chattering is not limited to this. When the countermeasure unit 15 detects the occurrence of chattering, it transmits the provisional value pr' of the induced command value immediately before or immediately after the occurrence of chattering as the induced command value pr to each power control device B1. After detecting the occurrence of chattering, the countermeasure unit 15 fixes the induced command value pr by using the provisional value pr' immediately before or immediately after the occurrence of chattering as the induced command value pr for a predetermined time. The predetermined time is set based on, for example, a demand time limit. The specific value is not limited, but may be, for example, 30 minutes (one-time limit) or 15 minutes (half of the 30-minute one-time limit). Note that, since control of the connection point power P(t) is stopped while the induction command value is fixed, the time for fixing the induction command value (difference value fixation time) represents a trade-off between suppressing chattering and the time for which power control for setting the connection point power P(t) to the system target value Pc is stopped. Therefore, the time for fixing the induction command value is set so as to suppress frequent occurrence of chattering while keeping the stop time within an acceptable range. In this embodiment, the countermeasure unit 15 fixes the induction command value pr to the provisional value pr′ of the induction command value immediately before or immediately after the occurrence of chattering, but it may also be fixed to a preset value. On the other hand, if the countermeasure unit 15 does not detect the occurrence of chattering, it transmits the provisional value pr′ of the induction command value input from the command value calculation unit 14 to each power control device B1 as the induction command value pr.

[0058] In power system S2, when the occurrence of chattering is detected, the induced command value is fixed. As described above, in power system S1, countermeasure unit 212a fixes difference value ΔP for calculating the induced command value, thereby fixing the induced command value (this can be understood from the simulations shown in FIGS. 4 and 5). In other words, fixing the induced command value in power system S2 has the same purpose as fixing calculation difference value ΔP in power system S1.

[0059] In the power system S2, the processing device A1 calculates the induced command value, and therefore each power control device B1 does not include a command value calculation unit 21. In each power control device B1 of the power system S2, the target calculation unit 22 acquires (receives) the induced command value pr from the processing device A1 and calculates an equipment target value using the acquired induced command value. Then, the power control unit 23 controls the output power based on the equipment target value.

[0060] The functions and effects of the power system S2 are as follows.

[0061] In the power system S2, the processing device A1 fixes the induction command value when it detects the occurrence of chattering, which is repeated switching between two control levels among multiple control levels. With this configuration, when chattering occurs, the induction command value transmitted to each power control device B1 is fixed, thereby suppressing switching of the control level in the discrete control device B11. This suppresses the occurrence of chattering in the discrete control device B11. Therefore, the power system S2 can suppress oscillation of the node power P(t) around the system target value Pc.

[0062] In the power system S2, each power control device B1 controls the output power Pout of the power device X to be controlled in accordance with the induced command value received from the processing device A1. At this time, the discrete control device B11 adjusts the output power Pout by switching the control level in accordance with the received induced command value. Therefore, in the discrete control device B11, chattering may occur when the control level is increased or decreased. Such an increase or decrease in the control level occurs when the induced command value changes from an increasing trend to a decreasing trend or from a decreasing trend to an increasing trend. Therefore, in the power system S2, the processing device A1 detects the occurrence of chattering when the provisional value pr' of the induced command value changes from an increasing trend to a decreasing trend or from a decreasing trend to an increasing trend. In other words, the power system S2 can detect the occurrence of chattering in the discrete control device B11 by monitoring the induced command value calculated by the command value calculation unit 14.

[0063] In the above first and second embodiments, an example was shown in which the multiple power control devices B1 include both a discrete control device B11 and a continuous control device B12, but in the power systems S1 and S2, the multiple power control devices B1 do not have to include the continuous control device B12.

[0064] The power system according to the present disclosure is not limited to the above-described embodiment, and the specific configuration of each part of the power system according to the present disclosure can be freely designed in various ways. [Explanation of symbols]

[0065] S1, S2: power system, A1: processing device, B1: power control device, B11: discrete control device, X: power equipment

Claims

1. An electric power system connected to an electric power system and controlling a connection point power at a connection point with the electric power system, a processing device that generates control information using the connection point power and a system target value that is a target for the connection point power; a plurality of power control devices each associated with a power device and controlling the output power of the corresponding power device; Equipped with each of the plurality of power control devices calculates an induction command value from a difference between the connection point power and the system target value using the control information generated by the processing device, and controls an output power of the corresponding power device using the calculated induction command value; the plurality of power control devices include a discrete control device that switches between a plurality of control levels in response to a change in the induction command value, thereby causing the output power of the corresponding power device to change discretely; When the discrete control device detects occurrence of chattering in which the control levels repeatedly switch between two of the plurality of control levels, the discrete control device fixes the difference to zero and calculates the induction command value.

2. 2. The power system according to claim 1, wherein the discrete control device provides hysteresis to a criterion for switching the control levels when switching between the at least two control levels, and increases a width of the hysteresis when detecting occurrence of the chattering.

3. 3. The power system according to claim 1, wherein the discrete control device gradually changes the difference to zero when the discrete control device detects the occurrence of chattering.

4. 3. The power system according to claim 1, wherein the discrete control device detects the occurrence of chattering when a positive or negative sign of the difference is reversed.

5. An electric power system connected to an electric power system and controlling a connection point power at a connection point with the electric power system, a processing device that calculates a guidance command value from a difference between the node power and a system target value that is a target for the node power; a plurality of power control devices each associated with a power device and controlling the output power of the corresponding power device; Equipped with each of the plurality of power control devices controls an output power of the corresponding power device using the induction command value calculated by the processing device; the plurality of power control devices include a discrete control device that switches between a plurality of control levels in response to a change in the induction command value, thereby causing the output power of the corresponding power device to change discretely; When the processing device detects occurrence of chattering in which the control levels repeatedly switch between two of the plurality of control levels, the processing device fixes the induction command value.

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