Power supply and demand device, power generation system, and control method

Abstract

To provide a power supply device which can suppress the amount of change of an instantaneous power generated according to the difference between the system frequency and the standard frequency of a power system.SOLUTION: According to an embodiment, the power supply device includes a virtual synthesis inverter and a storage battery. The virtual synthesis inverter is connected to a power system. The charge and discharge of the storage battery are controlled by the virtual synthesis inverter. The virtual synthesis inverter is connected to the power system in parallel to another inverter. The virtual synthesis inverter calculates a first standby time of an arbitrary length when the virtual synthesis inverter receives an operation instruction which involves an output of power to the power system or an input of power into the power system, and can control the storage battery for the operation instruction after the first stand-by time has passed.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] FIELD Embodiments of the present invention relate to a power supply and demand device, a power generation system, and a control method. [Background technology]

[0002] Electric power supply and demand devices such as virtual synchronous generators, virtual synchronous inverters, and virtual synchronous power conditioners, which have the same power adjustment capability (synchronization capability) as synchronous generators, correct the output power instructed by the control device according to the difference between the system frequency of the power system and the system standard frequency, and operate by adjusting the output power based on the corrected power.

[0003] For this reason, in a power generation system consisting of multiple power supply and demand devices connected in parallel, the amount of regulated power (corrected power amount) increases according to the number of parallel devices, and the operation results in power fluctuations with large changes in output power. If the difference between the system frequency and the standard system frequency is large, the amount of corrected power becomes large, causing large power fluctuations at the start of operation, etc.

[0004] Large power fluctuations destabilize power generation systems. For example, if a surge that exceeds the rated capacity occurs, protective devices will be activated, causing the power supply to become unstable. As such, there is concern that large power fluctuations could lead to power outages in power generation systems.

[0005] In addition, in a power generation system in which multiple grid-connected inverters or grid-connected power conditioners are connected in parallel and operated in parallel, the operation of the entire power generation system is controlled by connecting control synchronization signal lines between each grid-connected inverter or grid-connected power conditioner to synchronize operation and link control, or by connecting a synchronization control signal between a power management device (uGMS) that controls the operation of the entire power generation system and each grid-connected inverter or grid-connected power conditioner to synchronize operation and link control.

[0006] In either power generation system method, the system is made up of one grid-connected inverter, grid-connected power conditioner, or power management device that acts as a master and is the center of operation for the entire system, and the remaining grid-connected inverters and grid-connected power conditioners that act as slaves that operate according to instructions from the master.By measuring the voltage and frequency of the power grid, the system is connected to the power grid and the power supply and demand device is operated. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-85412 Summary of the Invention [Problem to be solved by the invention]

[0008] In a power generation system consisting of one master and multiple slaves, such as a grid-connected inverter or a grid-connected power conditioner, if the control synchronization signal line is interrupted, the synchronous operation signal will no longer be transmitted. This will prevent the grid-connected inverter or grid-connected power conditioner from synchronizing, destabilizing the entire power generation system and causing a power outage.

[0009] Similarly, if the master grid-connected inverter, grid-connected power conditioner, or power management device fails, there will be nothing to control the devices that make up the system, and the entire power generation system will become unstable, causing a power outage.

[0010] In other words, in any of the power generation system methods described above, if the control synchronization signal line is disconnected or the master device fails, the propagation of the control synchronization signal will be interrupted, which will destabilize the entire power generation system and cause a power outage.

[0011] In a power generation system that uses a virtual synchronous generator, a virtual synchronous inverter, a virtual synchronous power conditioner, or the like instead of a grid-connected inverter or a grid-connected power conditioner, the amount of power generated by each power device changes depending on the state of the power grid. Therefore, when simultaneous operation instructions are issued by a control synchronization signal from the master, large instantaneous power changes occur when operation starts or when operation starts due to changes in the amount of power supplied and demanded.

[0012] Large instantaneous power fluctuations can cause fluctuations in the power generated, which can lead to unstable operation of the power generation system and its constituent power devices, causing the protective devices to operate. This operation of the protective devices can cause a power outage in the power generation system.

[0013] In this way, in a power generation system in which a master device sends a control synchronization signal via a control synchronization signal line to command simultaneous operation, if the control synchronization signal line is broken or the master device fails, the entire power generation system will become unstable and a power outage will occur. Also, if a power generation system is constructed using power supply and demand devices with synchronizing capabilities, large power fluctuations may occur at the start of operation, and if large power fluctuations occur, the entire power generation system will become unstable and a power outage will occur.

[0014] The embodiments of the present invention provide a power supply and demand device, a power generation system, and a control method that can suppress the amount of change in instantaneous power that occurs in response to the difference between the system frequency of a power grid and a standard frequency. [Means for solving the problem]

[0015] According to an embodiment, a power supply and demand device includes a virtual synchronous inverter and a storage battery. The virtual synchronous inverter is connected to a power grid. Charging and discharging of the storage battery are controlled by the virtual synchronous inverter. The virtual synchronous inverter is connected to the power grid in parallel with other inverters, and when receiving an operation instruction involving outputting power to the power grid or inputting power from the power grid, calculates a first standby time of any length, and after the first standby time has elapsed, controls the storage battery in accordance with the operation instruction. When a difference between the frequency of the power grid measured when the operation instruction is received and the frequency of the power grid measured during the first standby time is equal to or less than a predetermined value, the storage battery is controlled in accordance with the operation instruction after the first standby time has elapsed, and when the difference is greater than the predetermined value, a second standby time of any length is calculated, and when the second standby time has elapsed since the calculation of the second standby time, the storage battery is controlled in accordance with the operation instruction. . [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a diagram showing an example of the configuration of a power generation system according to an embodiment. [Figure 2] 2 is a diagram showing an example of the configuration of a virtual synchronous inverter included in a power supply and demand device in the power generation system of the embodiment; [Figure 3] 1 is a diagram showing an example of the configuration of a virtual synchronous power conditioner when a power supply and demand device in a power generation system of an embodiment has the virtual synchronous power conditioner; [Figure 4] FIG. 3 is a diagram showing an example of a transition of operating power in the power generation system of the embodiment. [Figure 5] 4 is a flowchart showing an example of an operation procedure of virtual synchronous inverters of a plurality of power supply and demand devices in the power generation system of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, embodiments will be described with reference to the drawings.

[0018] FIG. 1 is a diagram showing an example of the configuration of a power generation system 100 according to an embodiment.

[0019] As shown in FIG. 1, a power generation system 100 according to the embodiment includes a plurality of power supply and demand devices 1 and a power monitoring and control device (μGMS) 2.

[0020] The power supply and demand device 1 has a virtual synchronous inverter 11 and a storage battery 12. The virtual synchronous inverters 11 mounted on each of the power supply and demand devices 1 in the power generation system 100 are connected in parallel to the power grid 3. The virtual synchronous inverter 11 is an inverter having a pseudo-inertia function that simulates the inertia of a synchronous generator that autonomously reduces frequency changes. The virtual synchronous inverter 11 monitors the frequency of the power grid 3 to detect frequency changes, and in the synchronous generator, realizes the pseudo-inertia function by simulating, by software, the inertia generated by the behavior of hardware such as the rotor.

[0021] The power monitoring and control device 2 is responsible for the overall control of the power generation system 100, and transmits operation control commands simultaneously to the multiple virtual synchronous inverters 11. These operation control commands include starting charging / discharging of the storage batteries 12 that have stopped charging / discharging, stopping charging / discharging of the storage batteries 12 that are currently charging / discharging, changing the amount of charging / discharging power, and not charging / discharging (setting the amount of charging / discharging power to 0). The power monitoring and control device 2 transmits these operation control commands to the multiple virtual synchronous inverters 11 for the purpose of stabilizing the frequency of the power grid 3. Note that the operation control command to not charge / discharge the storage batteries 12 that are currently charging / discharging (setting the amount of charging / discharging power to 0) is different from the command to stop charging / discharging the storage batteries 12 that are currently charging / discharging, and is one of the commands required to stabilize the frequency of the power grid 3.

[0022] The frequency of the power grid 3 fluctuates when the balance between supply and demand is disrupted. Specifically, when the demand for electricity falls below the supply (a surplus), the frequency rises, and when the demand exceeds the supply (a shortage), the frequency falls.

[0023] For example, when the demand for power exceeds the supply and the frequency of the power grid 3 drops, the virtual synchronous inverter 11 in the power generation system 100 first operates with a pseudo-inertia function to reduce the rate of change of frequency (RoCoF) (response due to inertia). Next, the virtual synchronous inverter 11 autonomously performs an operation to compensate for the power shortage to the extent possible based on the frequency of the power grid 3 (primary regulation capability). After that, upon receiving an operation control command from the power monitoring and control device 2, the virtual synchronous inverter 11 performs an operation according to the command (secondary regulation capability). In other words, the multiple virtual synchronous inverters 11 in the power generation system 100 operate independently without coordinating with each other.

[0024] When operating in response to an operation control command from the power monitoring and control device 2, the virtual synchronous inverter 11 corrects the amount of power indicated by the operation control command in accordance with the difference between the system frequency and the system standard frequency of the power system 3. If the difference between the system frequency and the system standard frequency is large, the corrected amount of power also becomes large, and the amount of power output from the virtual synchronous inverter 11 becomes significantly different from the amount of power indicated by the operation control command.

[0025] Here, when a plurality of virtual synchronous inverters 11 are connected in parallel to the power grid 3 as in the power generation system 100 of the embodiment, the correction amount becomes multiplied by the number of virtual synchronous inverters 11. Therefore, when a plurality of virtual synchronous inverters 11 operate simultaneously upon receiving an operation control command from the power monitoring and control device 2, a large instantaneous change in the amount of power occurs, and in some cases, a protective device may be activated, causing a power outage.

[0026] Therefore, the power generation system 100 of the embodiment is provided with a mechanism for suppressing the amount of change in instantaneous power that occurs in accordance with the difference between the system frequency of the power system 3 and the standard frequency, and this will be described in detail below.

[0027] 1, the storage batteries 12 included in each of the plurality of power supply and demand devices 1 in the power generation system 100 may have different storage capacities. Although FIG. 1 shows an example in which all of the plurality of power supply and demand devices 1 in the power generation system 100 have virtual synchronous inverters 11, the power supply and demand devices 1 may also be virtual power conditioners. Power supply and demand devices 1 having virtual synchronous inverters 11 and power supply and demand devices 1 having virtual power conditioners may be mixed in the power generation system 100.

[0028] FIG. 2 is a diagram showing an example of the configuration of the virtual synchronous inverter 11. As shown in FIG.

[0029] As shown in FIG. 2, the virtual synchronous inverter 11 includes a power generation inverter 111 and a virtual synchronous power generation control device 112.

[0030] The power generation inverter 111 converts DC power supplied from the storage battery 12 into AC power under the control of the virtual synchronous power generation control device 112. The AC power obtained by the power generation inverter 111 is output to the power grid 3.

[0031] The virtual synchronous generation control device 112 controls the power generation inverter 111 based on an operation control command from the power monitoring and control device 2. For example, the virtual synchronous generation control device 112 controls the amount of output power of the power generation inverter 111. This output power amount includes zero. The virtual synchronous generation control device 112 can also control the start and stop of charging and discharging of the storage battery 12. The virtual synchronous generation control device 112 also controls the power generation inverter 111 to realize the pseudo-inertia function described above. The virtual synchronous generation control device 112 also controls the power generation inverter 111 to realize the autonomous operation described above that compensates for power shortages to the extent possible without relying on an operation control command.

[0032] The power supply and demand device 1 having the storage battery 12 can also handle cases where the demand for power falls below the supply and the frequency of the power grid 3 rises. In other words, it is possible to take in surplus power and charge the storage battery 12 so that the system frequency of the power grid 3 approaches the standard frequency.

[0033] FIG. 3 is a diagram showing an example of the configuration of a virtual synchronous power conditioner 13 when the power supply and demand device 1 has the virtual synchronous power conditioner 13 instead of the virtual synchronous inverter 11.

[0034] Similar to the virtual synchronous inverter 11 , the virtual synchronous power conditioner 13 includes a power generation inverter 131 and a virtual synchronous power generation control device 132 .

[0035] The power generation inverter 131 converts DC power supplied from a natural energy power generation device 14, such as a solar power generation panel, into AC power under the control of the virtual synchronous power generation control device 132. The AC power obtained by the power generation inverter 131 is output to the power grid 3.

[0036] The virtual synchronous generation control device 132 controls the power generation inverter 131 based on an operation control command from the power monitoring and control device 2. For example, the virtual synchronous generation control device 132 controls the amount of output power of the power generation inverter 131. This output power amount includes zero. The virtual synchronous generation control device 132 also controls the power generation inverter 131 to achieve the pseudo-inertia function described above. The virtual synchronous generation control device 132 also controls the power generation inverter 131 to achieve the autonomous operation described above that compensates for power shortages to the extent possible, without relying on an operation control command.

[0037] Next, a mechanism for suppressing the amount of change in instantaneous power that occurs in accordance with the difference between the system frequency of the power system 3 and the standard frequency, which is included in the power generation system 100 of the embodiment, will be described.

[0038] Here, it is assumed that the demand for power exceeds the supply, causing the frequency of the power grid 3 to drop. When the virtual synchronous inverter 11 in the power generation system 100 of this embodiment receives an operation control command from the power monitoring and control device 2 to output power to the power grid 3 (to discharge the storage battery 12), the virtual synchronous inverter 11 calculates a random operation standby time to control the operation start time. After calculating the operation standby time, the virtual synchronous inverter 11 waits until the operation standby time has elapsed before starting the operation corresponding to the operation control command. At this time, the virtual synchronous inverter 11 measures the frequency of the power grid 3 and stores the measured value. Furthermore, the virtual synchronous inverter 11 continues to control the storage battery 12 that was being performed at the time of receiving the operation control command during standby. In other words, the virtual synchronous inverter 11 maintains the state of the power supply and demand device 1 at the time of receiving the operation control command during standby. This prevents the frequency of the power grid 3 from being changed due to its own actions before the operation standby time has elapsed.

[0039] The virtual synchronous inverter 11 continuously measures the frequency of the power grid 3 even while in standby mode. The virtual synchronous inverter 11 compares the frequency of the power grid 3 measured and stored when receiving an operation control command with the frequency of the power grid 3 measured while in standby mode. If another virtual synchronous inverter 11 (which has calculated a shorter operation standby time than the virtual synchronous inverter 11) starts operating while the virtual synchronous inverter 11 is in standby mode, a difference will occur between these two frequencies. A difference will also occur between these two frequencies due to changes in the amount of power demand or supply.

[0040] The virtual synchronous inverter 11 starts operation in response to the operation control command when the standby time elapses without a difference between the two frequencies exceeding a predetermined value. Here, the predetermined value is a threshold value for preventing large changes in instantaneous power. If the difference is less than the predetermined value, the virtual synchronous inverter 11 can start operation even if another virtual synchronous inverter 11 has started operating during its standby state. The predetermined value may be set differently for each power supply and demand device 1 depending on performance, such as power input / output capacity. The predetermined value may also be dynamically set depending on the difference between the frequency of the power grid 3 measured when the operation control command is received and the standard frequency of the power grid 3. The predetermined value may also be dynamically updated depending on the difference between the frequency of the power grid 3 measured during standby and the standard frequency of the power grid 3. For example, the predetermined value may be set or updated to a smaller value as the measured frequency of the power grid 3 approaches the standard frequency of the power grid 3.

[0041] On the other hand, if a difference of a predetermined value or more occurs between the stored frequency of the power grid 3 and the frequency of the power grid 3 measured during standby, the virtual synchronous inverter 11 recalculates a random operation standby time, as in the case when an operation control command is received, and measures and stores the frequency of the power grid 3. In other words, the stored frequency of the power grid 3 is updated, and standby for the newly calculated operation standby time is restarted from the beginning.

[0042] As described above, the virtual synchronous inverter 11 continues to measure the frequency of the power grid 3 even during standby, and starts operation corresponding to the operation control command when the operation standby time has elapsed without a difference of a predetermined value or more occurring between these two frequencies. On the other hand, when a difference of a predetermined value or more occurs between these two frequencies, the virtual synchronous inverter 11 again calculates the operation standby time, measures and stores the frequency of the power grid 3, and starts standby for the operation standby time.

[0043] As described above, in the power generation system 100 of the embodiment, when each of the virtual synchronous inverters 11 of the plurality of power supply and demand devices 1 in the power generation system 100 receives an operation control command from the power monitoring and control device 2, the virtual synchronous inverters 11 do not all start operating at the same time, but instead calculate a random operation standby time and control the operation start time. In this way, the power generation system 100 of the embodiment suppresses the occurrence of large changes in instantaneous power amount.

[0044] Furthermore, even during standby, the virtual synchronous inverter 11 continuously measures the frequency of the power grid 3 and compares it with the frequency of the power grid 3 measured and stored when an operation control command is received. If there is a difference between these two frequencies that is equal to or greater than a predetermined value, the virtual synchronous inverter 11 again calculates the operation standby time, measures and stores the frequency of the power grid 3, and starts standby for the operation standby time.

[0045] Since the frequency of the power grid 3 can change from moment to moment, by performing the above-described operations during standby, the virtual synchronous inverter 11 prevents overcompensation of power and the like from occurring due to the effect of providing an operation standby time.

[0046] The virtual synchronous inverter 11 periodically measures the input / output power amount of the power supply and demand device 1 in order to control the storage battery 12 so as to stabilize the input / output power amount of the power supply and demand device 1. More specifically, the virtual synchronous inverter 11 controls the storage battery 12 through the periodic measurement so that the input / output power amount of the power supply and demand device 1 converges to an average value. Therefore, the virtual synchronous inverter 11 calculates the above-mentioned operation standby time to be longer than the control time of the storage battery 12 for stabilizing the input / output power amount of the power supply and demand device 1. This is because if the virtual synchronous inverter 11 calculates an operation standby time shorter than the control time of the storage battery 12 for stabilizing the input / output power amount of the power supply and demand device 1 and starts operation corresponding to the operation control command, it will have an adverse effect on the control of the storage battery 12 for stabilizing the input / output power amount of the power supply and demand device 1.

[0047] Furthermore, the virtual synchronous inverter 11 may use the amount of stored energy in the storage battery 12 as a variable as a method of calculating a random standby time for operation. For example, when an operation control command to output power to the power grid 3 (to discharge the storage battery 12) is received, a calculation formula may be applied that is more likely to calculate a shorter standby time for operation as the amount of stored energy in the storage battery 12 increases, and when an operation control command to input power from the power grid 3 (to charge the storage battery 12) is received, a calculation formula may be applied that is more likely to calculate a shorter standby time for operation as the amount of stored energy in the storage battery 12 decreases.

[0048] For example, if the standby for starting an operation is an operation of decrementing a counter, and the standby ends when the counter value becomes 0, and an operation corresponding to an operation control command is started, the value indicating the amount of stored power in the storage battery 12 is set to 0 when it is minimum and 1 when it is maximum, (1) When discharging the storage battery 12 Operation standby time = (1 - amount of stored power in storage battery 12) x [randomly generated standby time] + n (n: minimum value of standby time) ... Equation 1 (2) When charging the storage battery 12 Operation standby time = (amount of stored power in the storage battery 12) × [randomly generated standby time] + n (n: minimum value of standby time) ... Equation 2 Just use the two formulas below.

[0049] 4 is a diagram showing an example of the transition of operating power in the power generation system 100 of the embodiment. Here, it is assumed that the demand for power exceeds the supply, causing the frequency of the power grid 3 to drop, and that the power monitoring and control device 2 sends an operation control command to the virtual synchronous inverter 11 to output power to the power grid 3 (to discharge the storage battery 12). It is also assumed that the power generation system 100 has five power supply and demand devices 1 with the same performance. In other words, it is assumed that the same value is set for all five power supply and demand devices 1 as the predetermined value, which is a threshold value for preventing the occurrence of large changes in instantaneous power energy, as described above.

[0050] 4, the horizontal axis represents elapsed time, the vertical axis on the left represents the output power value of the power generation system 100 as a difference from the rated value, and the vertical axis on the right represents the frequency of the power grid 3 as a difference from the rated value.

[0051] Symbols a1 to a3 indicate the derivation points of the operation standby time. Upon receiving an operation control command from the power monitoring and control device 2, the virtual synchronous inverter 11 calculates the operation standby time (a1) and waits for the operation standby time before starting operation. The virtual synchronous inverter 11 also measures and stores the frequency of the power grid 3 at the time of symbol a1. Conventionally, the virtual synchronous inverters that received an operation control command from the power monitoring and control device all start operating at the same time, which results in a large power being output from the power generation system, and if the power output far exceeds the rated power, the protective device will be activated.

[0052] 4, first, the virtual synchronous inverter 11 that has calculated the shortest operation standby time starts operation in response to the operation control command, and starts power output from the first power supply and demand device 1. It is assumed that the start of power output from the first power supply and demand device 1 does not cause a difference of a predetermined frequency or more with respect to the frequency of the power grid 3 at the time point a1.

[0053] Next, the virtual synchronous inverter 11 that has calculated the second shortest operation standby time starts operation in response to the operation control command, and starts power output from the second power supply and demand device 1. When power output from the second power supply and demand device 1 starts in addition to the first power supply and demand device 1, it is assumed that a difference of a predetermined frequency or more occurs between the frequency of the power grid 3 at the time point a1.

[0054] The remaining three virtual synchronous inverters 11 on standby other than the two virtual synchronous inverters 11 that have started operation recalculate their operation standby times (a2), and measure and store the frequency of the power grid 3 at the time point a2. Thereafter, the virtual synchronous inverter 11 that calculated the shortest operation standby time at the time point a2 starts operation in response to the operation control command, and power output from the third power supply and demand device 1 begins. It is assumed that the start of power output from this third power supply and demand device 1 does not result in a difference of more than a predetermined frequency from the frequency of the power grid 3 at the time point a2.

[0055] Next, the virtual synchronous inverter 11 that has calculated the second shortest operation standby time starts operation in response to the operation control command, and starts power output from the fourth power supply and demand device 1. When power output from the fourth power supply and demand device 1 starts in addition to the third power supply and demand device 1, it is assumed that a difference of a predetermined frequency or more occurs between the frequency of the power grid 3 at time a2.

[0056] The remaining virtual synchronous inverter 11 on standby other than the four virtual synchronous inverters 11 that have started operation recalculates the operation standby time (a3), and measures and stores the frequency of the power grid 3 at the time point a3. Thereafter, at the time point a4, it is assumed that the operation standby time calculated by the virtual synchronous inverter 11 of the fifth power supply and demand device 1 has elapsed. The virtual synchronous inverter 11 of the fifth power supply and demand device 1 that has started operation at the time point a4 determines that it is unnecessary to output power to the power grid 3 based on the frequency of the power grid 3. The virtual synchronous inverter 11 controls the storage battery 12 so as not to charge or discharge (setting the amount of charging and discharging energy to 0).

[0057] In this way, in the power generation system 100 of the embodiment, the amount of output power increases stepwise after receiving an operation control command from the power monitoring and control device 2. In other words, the power generation system 100 of the embodiment can suppress the amount of change in instantaneous power that occurs according to the difference between the system frequency of the power system 3 and the standard frequency.

[0058] 4, it is assumed that the demand for power exceeds the supply, causing the frequency of the power grid 3 to drop, and that the power monitoring and control device 2 sends an operation control command to the virtual synchronous inverter 11 to output power to the power grid 3 (discharge the storage battery 12). Conversely, even if the demand for power falls below the supply, causing the frequency of the power grid 3 to rise, and that the power monitoring and control device 2 sends an operation control command to the virtual synchronous inverter 11 to input power to the power grid 3 (charge the storage battery 12), in the power generation system 100 of the embodiment, the input power amount after receiving the operation control command from the power monitoring and control device 2 continues to increase stepwise.

[0059] Furthermore, since the virtual synchronous inverter 11 monitors the frequency of the power grid 3 to realize the pseudo-inertia function, it may predict an operation control command that will likely be sent from the power monitoring and control device 2. If an operation control command contrary to this prediction is received from the power monitoring and control device 2, the virtual synchronous inverter 11 respects the operation control command from the power monitoring and control device 2 and immediately executes an operation corresponding to the operation control command. For example, if an operation control command instructing charging of the storage battery 12 is received contrary to prediction in a situation where the frequency of the power grid 3 is dropping (power is insufficient), the virtual synchronous inverter 11 starts charging control of the storage battery 12 without calculating the operation standby time or waiting. Such an operation control command is considered to be intended for a special purpose, so it is preferable to execute it immediately.

[0060] FIG. 5 is a flowchart showing an example of an operation procedure of the virtual synchronous inverters 11 of the plurality of power supply and demand devices 1 in the power generation system 100 of the embodiment.

[0061] The virtual synchronous inverter 11 waits for an operation control command from the power monitoring and control device (μGMS) (S101). Upon receiving the operation control command (S102: Yes), the virtual synchronous inverter 11 measures and stores the frequency of the power grid 3 (S103). The virtual synchronous inverter 11 also measures and stores the amount of power stored in the storage battery 12 (S104). Furthermore, the virtual synchronous inverter 11 generates a random standby time (S105). Here, the standby time generated in S105 is the variable ([randomly generated standby time]) in the above-mentioned formula (Equation 1, Equation 2) for calculating the operation standby time. Note that S103 to S105 may be executed in any order, or two or more may be executed in parallel.

[0062] Next, the virtual synchronous inverter 11 generates an operation standby time for waiting for the start of operation corresponding to the operation control command, using the standby time generated in S105 and the amount of stored power measured and stored in S104 (S106).The virtual synchronous inverter 11 then starts counting (counting down) the generated operation standby time (S107).

[0063] Thereafter, the virtual synchronous inverter 11 determines whether the operation standby time has elapsed (S108). If the operation standby time has not elapsed (S108: No), the virtual synchronous inverter 11 measures the frequency of the power grid 3 (S109). Then, the virtual synchronous inverter 11 calculates the frequency difference between the frequency of the power grid 3 measured in S109 and the frequency of the power grid 3 measured and stored in S103 (S110).

[0064] If the frequency difference calculated in S110 is less than the predetermined value (S111: No), the virtual synchronous inverter 11 returns to S108. On the other hand, if the frequency difference is equal to or greater than the predetermined value (S111: Yes), the virtual synchronous inverter 11 returns to S103. That is, if the frequency difference calculated in S110 is less than the predetermined value (S111: No), the virtual synchronous inverter 11 continues standby with the stored frequency of the power grid 3 unchanged, whereas if the frequency difference is equal to or greater than the predetermined value (S111: Yes), the virtual synchronous inverter 11 updates the stored frequency of the power grid 3 to the value at that time, regenerates the operation standby time, and starts standby from the beginning.

[0065] It is determined in S108 that the operation standby time has elapsed if the frequency difference between the frequency of the power grid 3 measured in S109 and the frequency of the power grid 3 measured and stored in S103 does not become equal to or greater than a predetermined value during the operation standby time generated in S106. When the operation standby time has elapsed (S108: Yes), the virtual synchronous inverter 11 starts controlling the storage battery 12 in response to the operation control command (S112).

[0066] As described above, in the power generation system 100 of the embodiment, when each of the virtual synchronous inverters 11 of the plurality of power supply and demand devices 1 in the power generation system 100 receives an operation control command from the power monitoring and control device 2, the virtual synchronous inverters 11 do not all start operating at the same time, but instead calculate a random operation standby time and control the operation start time. In this way, the power generation system 100 of the embodiment suppresses the occurrence of large changes in instantaneous power amount.

[0067] That is, the power generation system 100 of the embodiment can suppress the amount of change in instantaneous power that occurs in accordance with the difference between the system frequency of the power system 3 and the standard frequency.

[0068] In the above explanation, an example has been shown in which the power monitoring and control device 2 simultaneously transmits operation control signals to multiple virtual synchronous inverters 11. However, the method of the embodiment in which the virtual synchronous inverter 11 calculates an operation standby time upon receiving an operation control signal and waits for the operation standby time can also be applied to a configuration in which the power generation system 100 has a configuration in which any one of the multiple virtual synchronous inverters 11 acts as a master and supplies operation control signals to the other virtual synchronous inverters 11.

[0069] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0070] 1...power supply and demand device, 2...power monitoring and control device, 3...power system, 11...virtual synchronous inverter, 12...storage battery, 13...virtual synchronous power conditioner, 14...natural energy power generation device, 100...power generation system, 111...power generation inverter, 112...virtual synchronous power generation control device, 131...power generation inverter, 132...virtual synchronous power generation control device.

Claims

1. A virtual synchronous inverter connected to a power grid; a storage battery whose charging and discharging is controlled by the virtual synchronous inverter, The virtual synchronous inverter is connected in parallel with other inverters to the power grid; When receiving an operation instruction involving output of power to the power grid or input of power from the power grid, calculate a first standby time of an arbitrary length, and after the first standby time has elapsed, control the storage battery corresponding to the operation instruction; When a difference between the frequency of the power grid measured when the operation instruction is received and the frequency of the power grid measured during the first standby time is equal to or less than a predetermined value, control of the storage battery corresponding to the operation instruction is performed after the first standby time has elapsed; When the difference is greater than the predetermined value, a second standby time of an arbitrary length is calculated, and after the second standby time has elapsed since the calculation of the second standby time, the storage battery can be controlled in accordance with the operation instruction. Power supply and demand equipment.

2. A virtual synchronous inverter connected to a power grid; a storage battery whose charging and discharging is controlled by the virtual synchronous inverter, The virtual synchronous inverter is connected in parallel with other inverters to the power grid; When receiving an operation instruction involving output of power to the power grid or input of power from the power grid, calculate a first standby time of an arbitrary length, and after the first standby time has elapsed, control the storage battery corresponding to the operation instruction; generating the first standby time based on the amount of stored power in the storage battery; Power supply and demand equipment.

3. A virtual synchronous inverter connected to a power grid; a storage battery whose charging and discharging is controlled by the virtual synchronous inverter, The virtual synchronous inverter is connected in parallel with other inverters to the power grid; When receiving an operation instruction involving output of power to the power grid or input of power from the power grid, calculate a first standby time of an arbitrary length, and after the first standby time has elapsed, control the storage battery corresponding to the operation instruction; When an operation instruction different from an operation behavior predicted from the frequency of the power grid is received, calculation of the first standby time and standby are omitted, and control of the storage battery according to the operation instruction is immediately started. Power supply and demand equipment.

4. A virtual synchronous inverter connected to a power grid; a storage battery whose charging and discharging is controlled by the virtual synchronous inverter, The virtual synchronous inverter is connected in parallel with other inverters to the power grid; When receiving an operation instruction involving output of power to the power grid or input of power from the power grid, calculate a first standby time of an arbitrary length, and after the first standby time has elapsed, control the storage battery corresponding to the operation instruction; receiving the operation instruction from another inverter acting as a master among the other inverters; Power supply and demand equipment.

5. A power supply and demand device, a virtual synchronous inverter connected to a power grid; a storage battery whose charging and discharging is controlled by the virtual synchronous inverter, The virtual synchronous inverter is connected in parallel with other inverters to the power grid; When receiving an operation instruction involving output of power to the power grid or input of power from the power grid, calculate a first standby time of an arbitrary length, and after the first standby time has elapsed, control the storage battery corresponding to the operation instruction; periodically measuring the input / output power amount of the power supply and demand device and controlling the storage battery so as to stabilize the input / output power amount; the first standby time is longer than a control time of the storage battery for stabilizing the input / output power amount; Power supply and demand equipment.

6. a plurality of power supply and demand devices each including a virtual synchronous inverter and a storage battery; a control device that controls the plurality of power supply and demand devices; Equipped with Each of the plurality of virtual synchronous inverters included in the plurality of power supply and demand devices It is connected to the power grid in parallel with other virtual synchronous inverters, When an operation instruction involving output of power to the power grid or input of power from the power grid is received from the control device, a first standby time of an arbitrary length is calculated, and after the first standby time has elapsed, control of the storage battery in accordance with the operation instruction is performed; When a difference between the frequency of the power grid measured when the operation instruction is received and the frequency of the power grid measured during the first standby time is equal to or less than a predetermined value, control of the storage battery corresponding to the operation instruction is performed after the first standby time has elapsed; When the difference is greater than the predetermined value, a second standby time of an arbitrary length is calculated, and after the second standby time has elapsed since the calculation of the second standby time, the storage battery can be controlled in accordance with the operation instruction. Power generation system.

7. A control method for a power supply and demand device including a virtual synchronous inverter connected to a power grid in parallel with another inverter, and a storage battery whose charging and discharging is controlled by the virtual synchronous inverter, The virtual synchronous inverter is When receiving an operation instruction involving outputting power to a power grid or inputting power from the power grid, calculate a first standby time of an arbitrary length, and after the first standby time has elapsed, control the storage battery in accordance with the operation instruction; When a difference between the frequency of the power grid measured when the operation instruction is received and the frequency of the power grid measured during the first standby time is equal to or less than a predetermined value, control of the storage battery corresponding to the operation instruction is performed after the first standby time has elapsed; If the difference is greater than the predetermined value, a second standby time of an arbitrary length is calculated, and after the second standby time has elapsed since the calculation of the second standby time, the storage battery is controlled in accordance with the operation instruction. Control method.

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