Adjustment power providing method, control program, and uninterruptible power supply

Abstract

To provide a method for providing adjustability with reduced response time.SOLUTION: A method for providing adjustability includes supplying a reverse flow power from an uninterruptible power supply which is connected to a commercial power system to the commercial power system when a frequency of the commercial power system is below a predetermined threshold.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for providing adjustment capability to a commercial power system, a control program, and an uninterruptible power supply. [Background technology]

[0002] In recent years, power generation methods using renewable energy such as solar power and wind power have become widespread. These power sources are connected to the power grid via inverters, so there is no inertia. Therefore, the greater the proportion of power supply generated using renewable energy in the total power supply in a power grid, the lower the inertia of the power grid.

[0003] The decrease in inertia force makes it difficult to maintain a constant frequency if the power supply suddenly drops due to a power grid accident. If the frequency drops significantly, it could develop into a large-scale power outage.

[0004] In order to prevent power outages and other disruptions, it is necessary to match supply and demand. The electricity required to match supply and demand at power plants and other facilities in response to changes in demand is called "adjustment capacity." Adjustment capacity is traded in a nationwide market known as the supply and demand adjustment market (Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2020-67919 Summary of the Invention [Problem to be solved by the invention]

[0006] The response time (the time required for the output to change from the issuance of a command to the command value) of the currently traded tertiary control reserve is 15 to 45 minutes. The shortest response time for the secondary control reserve and primary control reserve that will be traded in the future is also 10 seconds. The present invention aims to realize a control reserve provision method, control program, and uninterruptible power supply that shortens the response time to instantaneous. "Instantaneous" refers to a time shorter than the conventional response time, for example, less than 10 seconds. [Means for solving the problem]

[0007] A method for providing adjustment capability according to one aspect of the present application includes, when the frequency of a commercial power system is equal to or lower than a predetermined threshold, supplying reverse flow power to the commercial power system from an uninterruptible power supply device connected to the commercial power system. [Effects of the Invention]

[0008] In one aspect of the present application, it is possible to shorten the response time. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is an explanatory diagram showing an example of a power supply system diagram including a UPS system. [Figure 2] FIG. 1 is an explanatory diagram showing an example of a UPS circuit configuration diagram. [Figure 3] FIG. 10 is an explanatory diagram showing the operation of a frequency underload shedding method. [Figure 4] FIG. 2 is an explanatory diagram showing the operation of a UPS pseudo inertia force control method. [Figure 5] FIG. 2 is a block diagram showing an example of the hardware configuration of a UPS. [Figure 6] FIG. 2 is a block diagram showing an example of the hardware configuration of a UPS. [Figure 7] 10 is a flowchart illustrating an example of a procedure for adjusting power providing processing. [Figure 8] 10 is a flowchart illustrating an example of a procedure for adjusting power providing processing. [Figure 9] FIG. 10 is an explanatory diagram showing an example of setting a standby time. DETAILED DESCRIPTION OF THE INVENTION

[0010] (Embodiment 1) An embodiment will be described below with reference to the drawings. FIG. 1 is an explanatory diagram showing an example of a power supply system diagram including a UPS system. High-voltage AC power drawn from a commercial power supply system passes through a power receiving circuit and an extra-high voltage transformer (not shown) and is distributed via a feeder. A circuit breaker 2 is arranged in the upstream stage of the UPS system 1. The squares in FIG. 1 represent circuit breakers, with white boxes indicating a cut-off state and black boxes indicating a current-carrying state. The UPS system 1 includes a UPS input panel, a UPS transformer panel, a UPS main unit, a UPS output panel, etc.

[0011] The adjustable power proposed in this specification is characterized by the use of a UPS. The UPS in this specification is assumed to be a continuous inverter power supply UPS. A continuous inverter power supply UPS normally supplies input from the commercial power grid to connected devices via an inverter. By passing power through an inverter, it is possible to constantly supply regulated power stably regardless of the state of the commercial power grid. In a continuous inverter power supply UPS, the inverter circuit constantly supplies power, so it is called a continuous inverter power supply system.

[0012] Figure 2 is an explanatory diagram showing an example of a UPS circuit configuration. The UPS shown in Figure 2 is a UPS that uses the double conversion method, which is a type of continuous inverter power supply system. As shown in Figure 2, the input commercial power is converted to DC power by a converter, which is used to charge the storage battery, and is also converted back to AC via an inverter and supplied to the equipment. It is called a double conversion method because it performs two conversions, from AC to DC and from DC to AC. In the following explanation, the double conversion UPS will simply be referred to as the UPS.

[0013] The adjustment capability proposed in this specification provides adjustment capability by using three functions of the UPS: the first is a commercial synchronization function, the second is a cutoff function, and the third is a power supply function.

[0014] The utility synchronization function synchronizes with the commercial power supply and supplies constant voltage, constant frequency (CVCF) power. For example, if the frequency of the power supplied from the commercial power supply is within a specified range, e.g., a few percent (typically 1, 2, 3, 4, or 5%) of the rated frequency, the UPS will track the commercial power supply and output power at the same frequency. If the frequency of the power supplied from the commercial power supply is not within the specified range, the inverter will correct the frequency to the rated frequency and supply power to the equipment. To achieve this utility synchronization function, the UPS has the ability to monitor the frequency of the commercial power supply and change its control if the frequency exceeds or falls below a threshold. Here, the ability to change control if the frequency falls below the threshold is used to provide adjustment power.

[0015] If the commercial power supply becomes unstable or if the power supply is cut off (a power outage occurs), the UPS will supply the equipment with power stored in the storage battery for a certain period of time. At that time, the UPS will operate an uninterruptible switch to switch the power supply source from the commercial power system to the storage battery.

[0016] Needless to say, a UPS has a power supply function that uses a storage battery to supply power. This power supply function is used to achieve adjustment capability.

[0017] Next, we will explain how to provide regulation power using a UPS. In this specification, we propose two new methods of regulation power: under-frequency load shedding and UPS pseudo-inertia force control.

[0018] Figure 3 is an explanatory diagram showing the operation of underfrequency load shedding. In underfrequency load shedding, when the frequency of the commercial power system is low and below a predetermined threshold, circuit breaker 2 (breaker unit) is activated to cut off the power supply from the commercial power system to UPS system 1. This prevents UPS system 1 from consuming power from the commercial power system, providing adjustment capability through down DR. Power is supplied to various devices connected to UPS system 1 from a storage battery built into the UPS.

[0019] Figure 4 is an explanatory diagram showing the operation of the UPS pseudo-inertia force control method. In the pseudo-inertia force control method, when the frequency of the commercial power grid is low and below a predetermined threshold, the UPS 10 supplies power to various connected devices from its built-in storage battery and also reverse-flows a portion of the power that the storage battery can supply to the commercial power grid. This allows the UPS system 1 to supply power to the commercial power grid, providing power adjustment capability.

[0020] Next, the operation of the UPS 10 will be described in detail for both the underfrequency load shedding method and the pseudo inertia force control method. Figure 5 is a block diagram showing an example of the hardware configuration of the UPS. Figure 5 is a block diagram showing the normal state of the UPS 10 that executes the underfrequency load shedding method.

[0021] The UPS 10 includes a control unit 11, a detection element 12, a monitoring unit 13, a converter 14, an inverter 15, a storage battery 16, a switch 17, and a switch 18. The control unit 11 has one or more arithmetic processing devices such as a central processing unit (CPU), a micro-processing unit (MPU), a graphics processing unit (GPU), etc. The control unit 11 reads and executes a control program 1P (program, program product) (not shown) to perform various information processing, control processing, etc.

[0022] The detection element 12 is configured by, for example, a detection resistor, and detects the state (frequency, voltage level, etc.) of the commercial power system that is the input power source. The detection element 12 outputs the detection result to the monitoring unit 13.

[0023] Monitoring unit 13 monitors the state of the commercial power system based on the detection result of detection element 12 (detection unit), and outputs the monitoring result to control unit 11. For example, when monitoring unit 13 detects an abnormality in which the frequency of the commercial power system falls below a predetermined threshold, monitoring unit 13 generates information indicating the content of the abnormality and outputs it to control unit 11.

[0024] Converter 14 converts AC power supplied from a commercial power system into DC power of a predetermined level and supplies it to storage battery 16. Storage battery 16 is charged by the output from converter 14. Converter 14 also outputs the DC power to inverter 15.

[0025] Inverter 15 converts the DC power output by converter 14 into AC power of the same frequency (50 Hz north of Kanto, 60 Hz west of Kansai) and voltage level as the commercial power system, and outputs it.

[0026] The storage battery 16 is a backup power source that supplies power to external devices in the event of an abnormality in the commercial power system. The storage battery 16 is composed of a lithium ion battery, a nickel-cadmium battery, a lead storage battery, a nickel-metal hydride battery, or the like.

[0027] The switch 17 is a normally closed switch, i.e., its contacts are normally closed. In the normal state, it supplies AC input from the commercial power system to the UPS 10. If the monitoring unit 13 detects an abnormality in the commercial power system, the control unit 11 controls the switch 17 to transition from a closed state to an open state. This disconnects the UPS 10 from the commercial power system, and AC input from the commercial power system is no longer supplied to the UPS 10. This provides the commercial power system with regulation power through down DR.

[0028] The switch 18 is an uninterruptible switch that switches the power supply source from the commercial power system to the storage battery. Under normal conditions, the switch 18 energizes the converter 14 and the inverter 15. If the monitoring unit 13 detects an abnormality in the commercial power system, the contacts of the switch 18 are switched under the control of the control unit 11, and the output from the storage battery 16 is supplied to the inverter 15. The power supplied by the storage battery 16 also serves as the power source for operating the UPS 10.

[0029] Fig. 6 is a block diagram showing an example of the hardware configuration of a UPS. Fig. 6 is a block diagram showing an abnormal state of a UPS 10 that executes the pseudo-inertia force control method. The abnormal state refers to when the frequency of the commercial power system falls below a predetermined threshold. The components of the UPS 10 are the same as those in Fig. 5, so a description thereof will be omitted.

[0030] The operation of the UPS 10 will be described below. When the monitoring unit 13 detects an abnormality in the commercial power system, the contacts of the switch 18 are switched under the control of the control unit 11, and the output from the storage battery 16 is supplied to the inverter 15.

[0031] Also, the switch 17 maintains the contacts closed. Power from the storage battery 16 flows back to the converter 14. The converter 14 operates as an inverter because the input and output are reversed. The power converted to AC by the converter 14 operating as an inverter is supplied to the commercial power system. In other words, an adjustable step-up power is provided to the commercial power system. The storage battery 16 and the converter 14 operating as an inverter are an example of a supply unit.

[0032] Next, information processing performed by the UPS 10 will be described. Figures 7 and 8 are flowcharts showing an example of the procedure for adjustment capability provision processing. Figure 7 shows the procedure for adjustment capability provision processing in the underfrequency load shedding method. The control unit 11 of the UPS 10 acquires the frequency of the commercial power system from the monitoring unit 13 (step S1). The control unit 11 determines whether the acquired frequency is equal to or lower than a predetermined threshold (step S2). If the control unit 11 determines that the acquired frequency exceeds the predetermined threshold (NO in step S2), it executes step S1 again. If the control unit 11 determines that the acquired frequency is equal to or lower than the predetermined threshold (YES in step S2), it switches the switch 17 (step S3) and ends the processing. By switching the switch 17, the UPS 10 is disconnected from the commercial power system, and adjustment capability is provided.

[0033] 8 shows the procedure for the adjustment capability provision process in the pseudo inertial force control method. The control unit 11 of the UPS 10 acquires the frequency of the commercial power grid from the monitoring unit 13 (step S11). The control unit 11 determines whether the acquired frequency is equal to or lower than a predetermined threshold (step S12). If the control unit 11 determines that the acquired frequency exceeds the predetermined threshold (NO in step S12), it executes step S11 again. If the control unit 11 determines that the acquired frequency is equal to or lower than the predetermined threshold (YES in step S12), it switches the switch 18 (step S13). The control unit 11 starts reverse power flow from the storage battery 16 to the commercial power grid (step S14) and ends the process. The UPS 10 supplies power from the storage battery 16 to various connected devices and provides adjustment capability to the commercial power grid through reverse power flow.

[0034] 7 and 8 show processing in which the control unit 11 polls the frequency, but interrupt processing by the monitoring unit 13 may also be performed. An interrupt routine that executes step S3 in FIG. 7 and an interrupt routine that executes steps S13 and S14 in FIG. 8 are prepared. A threshold is set in the monitoring unit 13. When the monitoring unit 13 detects that the frequency of the commercial power system has fallen below a predetermined threshold, it executes an interrupt and runs the interrupt routine.

[0035] In the above explanation, the underfrequency load shedding method and the pseudo inertial force control method have been described as methods for providing adjustment capability. Both methods cannot be executed simultaneously by the same UPS 10. However, when multiple UPSs 10 are installed, a UPS 10 (second uninterruptible power supply) that operates using the underfrequency load shedding method and a UPS 10 (uninterruptible power supply) that operates using the pseudo inertial force control method may be mixed.

[0036] This embodiment has the following advantages. Adjustment capability using the underfrequency load shedding method is provided by switching switch 17. Adjustment capability using the pseudo-inertia force control method is provided by switching switch 18. The time required for switching switches 17 and 18 is approximately 200 milliseconds after monitoring unit 13 detects an abnormality in the commercial power system. Therefore, it is possible to provide adjustment capability with a shorter response time than conventional adjustment capability. Furthermore, there is no need to add new equipment to provide adjustment capability; it can be achieved simply by changing the control program of UPS 10. As a result, this contributes to the creation of safe and secure urban areas at low cost.

[0037] (Incentives provided) When the UPS system 1 provides adjustment capacity, an incentive may be given to the operator of the UPS system 1. It is reasonable to determine the amount of incentive to be given according to the amount of power provided as adjustment capacity and the duration of provision. The amount of power that can be provided as adjustment capacity and the duration of provision can be estimated from the performance and operating environment of the UPS 10, so the amount of incentive to be given may be determined based on the amount of power to be provided (estimated supply amount) and duration of provision (estimated supply duration) expected for each UPS system 1, and the determined amount of incentive may be given when adjustment capacity is provided.

[0038] Furthermore, the amount of power provided as adjustment capability (reverse flow power amount) and the duration of provision (supply duration) may be measured to provide an incentive. In this case, a power meter is installed near the UPS system 1 in the system connecting the UPS system 1 to the commercial power system. Although this requires the installation of a power meter, it is possible to more accurately determine the amount of incentive provided. Note that the degree of contribution to a stable power supply differs between providing adjustment capability by operating the UPS 10 using the underfrequency load shedding method and providing adjustment capability by operating the UPS 10 using the pseudo inertia force control method. Therefore, it is desirable to use a different method for calculating the incentive so that the amount of incentive is relatively larger in the case of the pseudo inertia force control method.

[0039] (Embodiment 2) In the first embodiment, when the UPS 10 detects that the frequency of the commercial power system has fallen below a threshold, the UPS system 1 immediately provides adjustment capability. This embodiment relates to a configuration in which a plurality of UPS systems 1 are installed at different positions in a power distribution network and provide adjustment capability.

[0040] In this embodiment, when multiple UPS systems 1 provide adjustment capability, the time (hereinafter referred to as the "standby time") from when it is detected that the frequency of the commercial power system has fallen below a predetermined threshold until the adjustment capability is provided varies depending on the location of each UPS system 1. FIG. 9 is an explanatory diagram showing an example of setting the standby time. In FIG. 9, UPS systems 1-1, 1-2, and 1-3 are located in order of proximity to a substation. Based on the assumption that a frequency drop propagates sequentially from the substation with a slight time difference, the UPS system 1-1 closest to the substation immediately provides adjustment capability upon detecting a frequency drop. The next-closest UPS system 1-2 waits 100 milliseconds after detecting the frequency drop before providing adjustment capability. The next UPS system 1-3 waits 200 milliseconds after detecting the frequency drop before providing adjustment capability. For simplicity of explanation, one UPS 10 is shown providing adjustment capability at each time, but multiple UPS systems may also be used. In other words, when the multiple UPSs 10 making up the first group detect a drop in frequency, they immediately provide adjustment power, and when the multiple UPSs 10 making up the second group detect a drop in frequency, they wait 200 milliseconds before providing adjustment power.

[0041] The standby time of each UPS 10 is planned based on the topology of the power distribution network, the power that each UPS 10 can provide as adjustment power, and the time of provision. The operators or owners of each UPS system 1 are not necessarily the same person. Therefore, it is desirable to have an aggregator that is responsible for adjusting the standby times of multiple UPS 10.

[0042] In this embodiment, since a plurality of UPSs 10 provide adjustment capacity with different standby times, it is possible to extend the time for which adjustment capacity is provided compared to when the UPSs 10 start providing adjustment capacity at the same time. This makes it possible to provide adjustment capacity that is required by the grid operator immediately after the frequency drops and until the provision of other adjustment capacity starts.

[0043] The technical features (constituent elements) described in each embodiment can be combined with each other, and by combining them, new technical features can be formed. The embodiments disclosed herein are to be considered as illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above meaning, and is intended to include all modifications within the meaning and scope of the claims. In addition, the claims are written in a format in which a claim cites two or more other claims (multiple claim format), but this is not limited to this. Multiple claims that cite at least one other claim (multi-multi claim format) may also be written. [Explanation of symbols]

[0044] 1: UPS system 10:UPS (Uninterruptible power supply) 11: Control section 12: Detector element 13: Monitoring Department 14: Converter 15: Inverter 16: Storage battery 17: Switch 18: Switch 1P: Control program 2: Circuit breaker

Claims

1. When the frequency of a commercial power grid is equal to or lower than a predetermined threshold, an uninterruptible power supply connected to the commercial power grid supplies reverse flow power to the commercial power grid; A plurality of the uninterruptible power supplies are connected to the commercial power system, and a waiting time from when the frequency becomes equal to or lower than the threshold until when the supply of the reverse flow power starts is set for each of the uninterruptible power supplies. How to provide adjustment force.

2. The uninterruptible power supply supplies the reverse flow power based on a pseudo-inertia force control method. The method for providing adjustment power according to claim 1 .

3. A second uninterruptible power supply is connected to the commercial power system, and the second uninterruptible power supply cuts off input from the commercial power system when the frequency is equal to or lower than the threshold value. The method for providing control power according to claim 1 or 2.

4. The expected value of the supply amount and supply time of the reverse flow power is determined in advance. The method for providing control power according to claim 1 or 2.

5. When the frequency of the commercial power grid is equal to or lower than a threshold, causing an uninterruptible power supply connected to the commercial power grid to supply reverse flow power to the commercial power grid; A plurality of the uninterruptible power supplies are connected to the commercial power system, and a waiting time from when the frequency becomes equal to or lower than the threshold until when the supply of the reverse flow power starts is set for each of the uninterruptible power supplies. Control program.

6. a detection unit that detects the frequency of a commercial power system; a supply unit that supplies reverse flow power to the commercial power grid when the frequency detected by the detection unit is equal to or lower than a threshold value; Equipped with A waiting time is set between when the frequency becomes equal to or lower than the threshold and when the supply of the reverse flow power starts. Uninterruptible power supply.

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