An isolated network power replacement method, hierarchical control architecture and control system

Abstract

This application relates to an islanded grid power replacement method, a hierarchical control architecture, and a control system, belonging to the technical field of islanded grid control. The method includes: when the islanded grid real-time frequency enters a steady state, receiving a power replacement command issued by the power grid dispatching system and performing power replacement according to the command; when the islanded grid real-time frequency enters a quasi-steady state, executing a steady-state control strategy and applying the generated target power command to adjustable resources; when the islanded grid real-time frequency enters a transient state, executing a transient control strategy, updating the target power command, and applying the generated target power command to adjustable resources; continuing to monitor the steady-state status of the islanded grid real-time frequency until power replacement is completed and the islanded grid real-time frequency enters a steady state, at which point the islanded grid power replacement ends. This application effectively solves the problem of the disconnect and mutual interference between islanded grid power replacement and frequency control in the prior art.

Description

Technical Field

[0001] This application relates to the field of islanded grid control technology, and in particular to an islanded grid power replacement method, a hierarchical control architecture, and a control system. Background Technology

[0002] At present, the proportion of new energy sources such as wind power and photovoltaic power in remote areas and islands is continuously increasing. When the output of new energy sources increases or decreases significantly due to changes in weather conditions, it is necessary to replace the power changes with other power generation resources or adjustable loads in the system. However, the power replacement process is affected by the instability of real-time frequency, which affects the quality of power replacement and further leads to the problem of disconnection and mutual interference between power replacement and frequency control in isolated grids. Summary of the Invention

[0003] This invention provides an islanded grid power replacement method, a hierarchical control architecture, and a control system. In the case of the lack of a coordinated power replacement and frequency control method in islanded grid scenarios, it aims to effectively solve the problem of the disconnect and mutual interference between islanded grid power replacement and frequency control, and achieve stable control of islanded grid power replacement and process frequency.

[0004] Firstly, this application provides a method for islanded network power substitution, including: When the real-time frequency of the isolated grid enters a steady state, the power replacement control system receives the power replacement command issued by the grid dispatch and executes the power replacement according to the power replacement command. When the real-time frequency of the isolated network enters a quasi-steady state, a steady-state control strategy is executed, and the power substitution is then performed, with the generated target power command applied to the adjustable resources. When the real-time frequency of the isolated network enters a transient state, a transient control strategy is executed, the target power command is updated, the power replacement is executed again, and the generated target power command is applied to the adjustable resources. Continue to monitor the steady-state status of the isolated grid's real-time frequency, and when the isolated grid's real-time frequency enters a steady state, use the power replacement control system to receive the power replacement command issued by the power grid dispatch, execute the power replacement according to the power replacement command, until the power replacement is completed and the isolated grid's real-time frequency enters a steady state, and then end the isolated grid power replacement.

[0005] In some embodiments, it also includes: If the real-time frequency of the isolated network does not enter a quasi-steady state, power substitution will continue to be performed, and the generated target power command will be applied to the adjustable resources. If the isolated network real-time frequency has not entered a transient state, power substitution continues, and the generated target power command is applied to the adjustable resources. In some embodiments, the step of determining that the isolated network real-time frequency has entered a steady state includes: When the real-time frequency of the isolated network is between the preset steady-state lower limit and the preset steady-state upper limit, it is determined that the real-time frequency of the isolated network has entered a steady state.

[0006] In some embodiments, the step of determining that the real-time frequency of the isolated network has entered a quasi-steady state includes: When the real-time frequency is greater than the preset transient lower limit and less than or equal to the preset steady-state lower limit, or when the real-time frequency is greater than or equal to the preset steady-state upper limit and less than the preset transient upper limit, it is determined that the real-time frequency of the isolated network has entered a quasi-steady state, wherein the preset transient lower limit is less than the preset steady-state lower limit and the preset steady-state upper limit is less than the preset transient upper limit.

[0007] In some embodiments, the step of determining that the isolated network real-time frequency has entered a transient state includes: When the real-time frequency is less than or equal to the preset transient lower limit and the real-time frequency is greater than or equal to the preset transient upper limit, the real-time frequency of the isolated network enters a transient state.

[0008] In some embodiments, when the isolated network real-time frequency enters a quasi-steady state, a steady-state control strategy is executed, including: The rated frequency of the isolated grid is preset, the frequency deviation between the real-time frequency of the isolated grid and the rated frequency of the isolated grid is calculated, and the additional compensation power is calculated using the frequency deviation. The base power is superimposed on the additional compensation power to obtain the replacement power; Obtain the real-time power of each of the adjustable resources, superimpose the replacement power with the real-time power of each of the adjustable resources, and generate the target power command.

[0009] In some embodiments, when the isolated network real-time frequency enters a transient state, a transient control strategy is executed, including: The frequency modulation power increment is calculated based on the frequency deviation. A preset frequency modulation priority and frequency modulation allocation ratio are used to decompose the frequency modulation power increment into the frequency modulation power of each of the adjustable resources. If the sign direction of the frequency modulation power increment is the same as that of the replacement power, then the frequency modulation power increment is superimposed on the replacement power, and the target power command is updated. If the sign direction of the frequency modulation power increment is opposite to that of the displacement power, the displacement power is locked and the target power command is updated.

[0010] In some embodiments, updating the target power command and then continuing the power replacement includes: The updated target power command is issued to each of the adjustable resources; A preset steady-state region holding time is set. When the real-time frequency recovers to the steady state and the holding time of the real-time frequency reaches the steady-state region holding time, the lockout of the replacement power is automatically released, and the power replacement is performed again.

[0011] Secondly, this application provides a hierarchical control architecture for implementing the isolated network power replacement method as described above, including a co-control master station and a co-control substation; The co-control master station is used to collect the operating status information of the isolated grid, receive the power replacement command issued by the power grid dispatch, execute the steady-state control strategy and the transient control strategy, generate power commands, and send the power commands to each of the co-control substations; The co-control substation is set on each of the adjustable resources, and is used to receive power commands from the co-control master station and send them to each controlled device to execute the power commands, as well as to collect the operating data of each controlled device and send the operating data to the co-control master station to provide feedback on the execution status of the controlled devices.

[0012] In some embodiments, the master control station is provided with an IEC61850-MMS protocol communication link and an IEC61850-GOOSE protocol communication link, and the sub-control station is provided with a communication link based on the IEC61850-GOOSE protocol between itself and each of the controlled devices.

[0013] Thirdly, this application provides a multimodal islanded grid power displacement control system, comprising: The power replacement module is used to receive power replacement instructions issued by the power grid dispatching system when the real-time frequency of the isolated grid enters a steady state, and to execute the power replacement according to the power replacement instructions. The steady-state control strategy execution module is used to execute the steady-state control strategy when the real-time frequency of the isolated network enters a quasi-steady state, and then continue to execute the power replacement, and apply the generated target power command to the adjustable resources; The transient control strategy execution module is used to execute the transient control strategy and update the target power command when the real-time frequency of the isolated network enters a transient state, and then continue to execute the power replacement and apply the generated target power command to the adjustable resources. The feedback adjustment module is used to continue monitoring the steady-state status of the isolated grid's real-time frequency. When the isolated grid's real-time frequency enters a steady state, it uses the power replacement control system to receive the power replacement command issued by the power grid dispatching system, executes the power replacement according to the power replacement command, and continues until the power replacement is completed and the isolated grid's real-time frequency enters a steady state, at which point the isolated grid power replacement ends.

[0014] The islanded power replacement method, hierarchical control architecture, and control system disclosed in this application coordinate power replacement and frequency fluctuation control. They set steady-state control strategies and transient control strategies in the multi-modal frequency range, effectively avoiding the impact of frequency fluctuations and frequency interference on the power replacement quality, and further improving the islanded power replacement efficiency and the stability of process frequency control. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] To gain a more complete understanding of this application and its beneficial effects, the following description will be provided in conjunction with the accompanying drawings, wherein the same reference numerals in the following description denote the same parts.

[0017] Figure 1 A flowchart of the islanded grid power replacement method provided in an embodiment of the present invention; Figure 2 This is a flowchart of the steady-state control strategy in the islanded power replacement method provided in this embodiment of the invention; Figure 3 This is a flowchart of the transient control strategy in the islanded power replacement method provided in this embodiment of the invention; Figure 4 This is a hierarchical control architecture diagram for implementing the islanded grid power replacement method provided in an embodiment of the present invention; Figure 5 This is a system block diagram for implementing the islanded grid power replacement method according to an embodiment of the present invention. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0019] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the term "and / or" in this document is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Furthermore, the character " / " in this document, unless otherwise specified, generally indicates that the preceding and following related objects have an "or" relationship.

[0020] Currently, with the rapid development of new energy power generation technologies, the proportion of wind power, photovoltaic power, and other new energy sources in isolated power grid systems in remote areas and islands continues to increase. However, the output of new energy sources is intermittent and fluctuates. When the output of new energy sources increases or decreases significantly due to changes in weather conditions, other power generation resources or adjustable loads in the system need to take over the changed power to maintain the real-time balance of source and load power in the system. This power taking over process is called "power replacement," and power replacement needs to be carried out when the isolated grid system is in a steady state. It is a key link in the economic and safe operation of isolated grids.

[0021] However, the power replacement process has two different levels of frequency stability issues. First, small frequency fluctuations usually occur during the power replacement process of an isolated network. Second, large frequency over-limit issues can occur during the power replacement process of an isolated network.

[0022] Therefore, for isolated grid scenarios, especially those with a high proportion of renewable energy access and multiple types of adjustable source and load resources such as thermal power, energy storage, renewable energy and adjustable loads, existing technologies do not yet have a control method for coordinated power replacement and frequency control, which cannot meet the requirements for power replacement and process frequency stability control of isolated grids.

[0023] Therefore, in order to solve at least one of the above-mentioned problems, this application provides an islanded power replacement method, a hierarchical control architecture, and a control system to solve the above problems.

[0024] Figure 1 The diagram shows the islanded power replacement method provided in this embodiment, which specifically includes the following steps: Step S100: When the real-time frequency of the isolated grid enters a steady state, the power replacement control system receives the power replacement command issued by the grid dispatch and performs power replacement according to the power replacement command. Step S200: When the real-time frequency of the isolated network enters a quasi-steady state, execute the steady-state control strategy, then continue to execute power replacement, and apply the generated target power command to the adjustable resources; Step S300: When the real-time frequency of the isolated network enters a transient state, execute the transient control strategy, update the target power command, continue to execute power replacement, and apply the generated target power command to the adjustable resources. Step S400: Continue to monitor the steady-state status of the islanded grid's real-time frequency. Once the islanded grid's real-time frequency enters a steady state, use the power replacement control system to receive the power replacement command issued by the power grid dispatch center. Execute the power replacement according to the power replacement command until the power replacement is completed and the islanded grid's real-time frequency enters a steady state, then end the islanded grid power replacement.

[0025] Optionally, in this embodiment, the islanded grid includes: thermal power units, electrochemical energy storage equipment, wind power, photovoltaic power, and electrolytic aluminum industrial loads, etc., wherein the installed capacity of thermal power is 600MW, the installed capacity of wind power is 500MW, the installed capacity of photovoltaic power is 500MW, the energy storage is 200MW / 400MWh, and the total installed capacity of electrolytic aluminum industrial loads and residential loads is approximately 600MW. Meanwhile, the islanded grid voltage level is 220kV and the islanded grid rated frequency is 50Hz.

[0026] In step S100, the power replacement control system receives the power replacement command issued by the power grid dispatching system and performs power replacement according to the power replacement command, specifically as follows: Step S110: Receive the total system power change data from the power grid dispatch center, preset an allocation coefficient for the total system power change data, and decompose the total system power change data into the base power of each adjustable resource according to the allocation coefficient. The formula for the total system power change data is: ; Among them, P total Pci represents the total change in system power, Pci represents the base power of each adjustable resource, and N represents the total amount of adjustable resources.

[0027] Step S120: The power grid photovoltaic power prediction system predicts that the photovoltaic output will drop by 150MW in 15 minutes. The power grid dispatching system issues a 15MW replacement power command and replacement pulse every minute.

[0028] Step S130: The total system power change is preset with allocation coefficients, including allocation coefficients for thermal power units, energy storage and electrolytic aluminum loads. Based on the allocation coefficients, the total system power change is decomposed into the base power of each adjustable resource.

[0029] For example, in the first minute, the base power of each adjustable resource includes: thermal power unit Pc1=15MW, energy storage Pc2=0MW, and electrolytic aluminum load Pc3=0MW. The target power command includes: thermal power unit P1=195MW, energy storage P2=0MW, and electrolytic aluminum load P3=0MW. The load change rate of the thermal power unit is 1.5%Pe / min, and the active power regulation rate of the energy storage is 10%Pe / 20ms. At the end of the first minute, the output increment of the thermal power unit is 9MW, and the output increment of the energy storage is 0MW. Then, the power deficit of the isolated grid is 6MW.

[0030] In step S200, this embodiment adopts a steady-state control strategy to adapt to the power replacement and process frequency stability coordinated control in the isolated grid scenario when performing power replacement. This achieves coordinated control of power replacement and frequency fluctuations at different scales. The steady-state control strategy that coordinates power replacement and frequency stability significantly improves the stability of the replacement process.

[0031] In step S300, this embodiment monitors and identifies possible transient situations during power replacement. By constructing a transient control strategy that includes a direction judgment mechanism, it takes into account both rapid frequency pullback and power replacement, avoiding frequent power replacement interruptions or increased frequency fluctuations caused by mutual interference between the two.

[0032] In some embodiments, it also includes: If the real-time frequency of the isolated network has not entered a quasi-steady state, continue to perform power substitution and apply the generated target power command to the adjustable resources; If the real-time frequency of the isolated network does not enter a transient state, power replacement continues, and the generated target power command is applied to the adjustable resources.

[0033] In this embodiment, after the adjustable resources receive the power replacement pulses and power replacement instructions issued by the power grid dispatch through the coordination control substation and the coordination control master station, the base power is allocated to each adjustable resource in a targeted manner to act on the controlled equipment, which can better improve the overall power transmission efficiency of the power grid and ensure the working safety performance of the power grid.

[0034] In some embodiments, step S100, determining that the islanded network real-time frequency has entered a steady state, includes: When the real-time frequency of the isolated network is between the preset steady-state lower limit and the preset steady-state upper limit, the real-time frequency of the isolated network is determined to have entered a steady state.

[0035] In this embodiment, the frequency range includes: a steady-state range, a quasi-steady-state range, and a transient range. The division of the frequency range includes: Steady-state range (49.95, 50.05); Quasi-steady-state interval (49.90, 49.95] ∪ [50.05, 50.10); The transient interval is (0, 49.90] ∪ [50.10, +∞).

[0036] Here, the preset steady-state region maintenance time is no less than 30 seconds, the initial frequency of the isolated grid is 50.02Hz, which is within the steady-state range (49.95, 50.05), and the real-time frequency maintenance time exceeds 30 seconds. Upon confirmation of entering steady state, the power replacement function is automatically activated, receiving power replacement pulses and power replacement commands from the grid dispatch center, and executing the power replacement command. At this time, the isolated grid load is 600MW, and the real-time power P of the thermal power unit is...a1 For 180MW, the real-time energy storage power P a2 It has a capacity of 0MW and an energy storage capacity of 50%.

[0037] Furthermore, in this embodiment, frequency ranges are divided to achieve power replacement in multi-mode situations, avoiding the impact of power issues within the isolated grid on the overall stability and quality of power replacement. Based on this, this embodiment automatically monitors the real-time frequency of the isolated grid and performs power replacement only when the real-time frequency of the isolated grid is in a steady-state region, so as to avoid power fluctuations affecting replacement efficiency and the overall safety of the power grid.

[0038] In some embodiments, step S200, determining that the islanded network real-time frequency has entered a quasi-steady state, includes: When the real-time frequency is greater than the preset transient lower limit and less than or equal to the preset steady-state lower limit, or when the real-time frequency is greater than or equal to the preset steady-state upper limit and less than the preset transient upper limit, the real-time frequency of the isolated network is determined to have entered a quasi-steady state, where the preset transient lower limit is less than the preset steady-state lower limit and the preset steady-state upper limit is less than the preset transient upper limit.

[0039] In this embodiment, a significant frequency overshoot can occur during the power replacement process of the isolated network. This is because the overall capacity of the isolated network is relatively small, and when a sudden large disturbance occurs during power replacement (e.g., a grounding fault in the isolated network's electrolytic aluminum load line), the real-time frequency of the isolated network can easily exceed the limit and enter a transient state, affecting the stability of the power replacement process. Therefore, this embodiment quickly and accurately identifies the transient region to facilitate rapid adjustment and processing, enabling the real-time frequency of the isolated network to quickly recover to a steady state and ensuring the smoothness of the power replacement process.

[0040] In some embodiments, step S300, determining that the real-time frequency of the isolated network has entered a transient state, includes: When the real-time frequency is less than or equal to the preset transient lower limit and the real-time frequency is greater than or equal to the preset transient upper limit, the real-time frequency of the isolated network enters the transient state.

[0041] Furthermore, when an isolated grid performs power replacement, the grid dispatch center issues a 15MW replacement power command and replacement pulse every minute. The current replacement power includes: thermal power units of P r1 =15MW, energy storage is P r2 =0MW and electrolytic aluminum load is P r3 =0MW, current real-time power P of thermal power unit a1 For 180MW, the real-time energy storage power P a2 The target power command is 195MW for thermal power units, 0MW for energy storage, 0MW for electrolytic aluminum load, and 0MW for islanded grid frequency.

[0042] At this time, a grounding fault occurred in the isolated electrolytic aluminum load line, the line switch was disconnected, and the 48MW electrolytic aluminum load was suddenly lost. The isolated grid frequency rapidly increased from 50Hz to 50.15Hz. At this time, the real-time frequency of the isolated grid entered a transient state.

[0043] In some embodiments, in step S200, when the real-time frequency of the isolated network enters a quasi-steady state, a steady-state control strategy is executed, including: Step S210: Preset the islanded grid rated frequency, calculate the frequency deviation between the islanded grid real-time frequency and the islanded grid rated frequency, and use the frequency deviation to calculate the additional compensation power. Step S220: Superimpose the base power onto the additional compensation power to obtain the replacement power; Step S230: Obtain the real-time power of each adjustable resource, superimpose the replacement power with the real-time power of each adjustable resource, and generate a target power command.

[0044] In step S210, steps S120 and S130 are repeated first, and the output of the thermal power unit and energy storage gradually increases. At this time, due to the continuous accumulation of power deficit in the isolated grid, the real-time frequency of the isolated grid gradually drops. At the 4th minute, the real-time frequency of the isolated grid drops to 49.95Hz, and the isolated grid enters a quasi-steady state. At this time, the steady-state control strategy is executed.

[0045] In step S220, the frequency deviation between the real-time frequency and the islanded grid's rated frequency is 0.05Hz. This frequency deviation is calculated using a PID controller, and an additional compensation power is quickly output based on the current power. The additional compensation power is Ps2 = 16MW. The calculated replacement power includes: thermal power units at Pr1 = 15MW, energy storage at Pr2 = 16MW, and electrolytic aluminum load at Pr3 = 0MW. The target power command is generated as follows: thermal power units at P1 = 222MW, energy storage at P2 = 16MW, electrolytic aluminum load at P3 = 0MW, and the islanded grid frequency is restored to 50Hz.

[0046] In step S230, steps 120, S130, S210 and S220 are executed in sequence until the power replacement of 150MW is completed and the islanded grid frequency reaches stability.

[0047] Figure 2As shown, the overall process of the steady-state control strategy in this embodiment includes: detecting and determining whether the real-time frequency of the isolated grid has entered a steady state; if so, the adjustable resources send power replacement input to the grid dispatch through the co-control master station and the co-control substation. The co-control master station waits to receive the power replacement pulse and replacement power command issued by the grid dispatch, and determines whether it has received the power replacement pulse; if not, it returns to the co-control master station to wait to receive the power replacement pulse and replacement power command issued by the grid dispatch; if so, it presets an allocation coefficient for the total system power change, and decomposes the total system power change into the base power of each adjustable resource according to the allocation coefficient. Determine whether the isolated grid frequency has entered a quasi-steady state. If not, the additional compensation power is 0, the replacement power is calculated directly, the real-time power of each adjustable resource is obtained, the replacement power is superimposed with the real-time power of each adjustable resource, and a target power command is generated. If so, the rated frequency of the isolated grid is preset, the frequency deviation between the real-time frequency and the rated frequency of the isolated grid is calculated, the additional compensation power is calculated using the frequency deviation, the base power is superimposed on the additional compensation power to obtain the replacement power, the real-time power of each adjustable resource is obtained, the replacement power is superimposed with the real-time power of each adjustable resource, and a target power command is generated. Then, return to the co-control master station to wait for the power replacement pulse and replacement power command issued by the power grid dispatch.

[0048] Thus, in this embodiment, slight frequency fluctuations typically occur during the power replacement process of an isolated grid. This is because, in actual operation, the entities undertaking power replacement are generally large-capacity power generation resources (e.g., thermal power units, gas turbine units, etc.). Due to their mechanical inertia and thermal characteristics, the output adjustment rate of these entities is often lower than the rate of change in the output of new energy sources. This will result in a small power gap during the gradual ramp-up of the entities to replace the power of new energy sources, causing small frequency fluctuations. Therefore, a steady-state control strategy needs to be added during the power replacement process of an isolated grid to achieve dynamic and stable changes in the replacement power.

[0049] In some embodiments, in step S300, when the real-time frequency of the isolated network enters a transient state, a transient control strategy is executed, including: Step S310: Calculate the frequency modulation power increment based on the frequency deviation; Step S320: Preset frequency modulation priority and frequency modulation allocation ratio, and use the frequency modulation priority and frequency modulation allocation ratio to decompose the frequency modulation power increment into the frequency modulation power of each adjustable resource. Step S330: If the signs of the frequency modulation power increment and the replacement power are in the same direction, then the frequency modulation power increment is superimposed on the replacement power, and the target power command is updated. Step S340: If the signs of the frequency modulation power increment and the replacement power are opposite, then the replacement power is locked and the target power command is updated.

[0050] Here, the formula for the frequency modulation power increment in this embodiment is: ; Among them, P fi Let N be the frequency modulation power of each adjustable resource, and N be the total number of adjustable resources.

[0051] Step S350: If the sign directions are the same, then the frequency modulation power increment is superimposed on the replacement power, and the target power command is updated, using the following formula: ; Among them, P i To update the target power command, P ai For the real-time power of each adjustable resource, P fi P represents the frequency modulation power of each adjustable resource. ri For replacement power; Step S360: When the sign direction is opposite, the replacement power is blocked, and the target power command is updated, using the following formula: ; Among them, P i To update the target power command, P ai For the real-time power of each adjustable resource, P fi For the frequency modulation power of each adjustable resource, The frequency deviation is 0.15Hz. After PID calculation, the required frequency modulation power increment P is... f =-48MW.

[0052] Within a preset transient frequency control range of ±0.2Hz, a preset frequency regulation allocation ratio is established, including: a thermal power unit allocation coefficient of 0.5, an energy storage allocation coefficient of 0.5, and an electrolytic aluminum load allocation coefficient of 0. Using frequency regulation priority and the frequency regulation allocation ratio, the frequency regulation power increment is decomposed into the frequency regulation power of each adjustable resource. The thermal power unit requires a frequency regulation power P. f1 =-24MW, energy storage requires output frequency regulation power P f2 =-24MW.

[0053] The replacement power of the thermal power unit is P r1 =15MW, energy storage is P r2 =0MW. At this time, the power replacement of thermal power units and energy storage is reversed with the frequency regulation power. The replacement power is locked and the target power command is updated to P1=156MW for thermal power units and P2=-24MW for energy storage.

[0054] The steady-state region is maintained for 30 seconds after the real-time frequency of the isolated grid is 50.05Hz. Once the real-time frequency is maintained for more than 30 seconds, the steady-state region is reached. The power replacement permission is sent to the grid dispatch again. The grid dispatch sends a 15MW replacement power instruction and replacement pulse every minute until the power replacement of 150MW is completed and the isolated grid frequency reaches stability.

[0055] Figure 3 As shown, the overall process of the transient control strategy in this embodiment includes: determining whether the isolated grid frequency has entered a transient state; if so, calculating the frequency regulation power increment based on the frequency deviation; presetting the frequency regulation priority and frequency regulation allocation ratio; using the frequency regulation priority and frequency regulation allocation ratio to decompose the frequency regulation power increment into the frequency regulation power of each adjustable resource; determining whether the sign direction of the frequency regulation power increment and the replacement power are in the same direction; if so, superimposing the frequency regulation power increment on the replacement power and updating the target power command; if not, blocking the replacement power and updating the target power command; after the signs are reversed and the target power command is updated, determining whether the real-time frequency of the isolated grid continues to enter a steady state; if so, investing the replacement power and receiving the grid dispatch replacement power command.

[0056] Thus, in order to avoid mutual interference between power substitution and frequency control, this embodiment further determines the sign direction of the frequency modulation power increment and the substitution power. When the directions are the same, the frequency modulation power increment is superimposed on the substitution power. When the directions are opposite, the substitution power is blocked to avoid conflict between power substitution and frequency control.

[0057] In some embodiments, in step S300, updating the target power command and then continuing to perform power replacement includes: Issue updated target power commands to each adjustable resource; The preset steady-state region holding time is used. When the real-time frequency recovers to the steady state and the holding time of the real-time frequency reaches the steady-state region holding time, the power replacement lockout is automatically released and the power replacement is performed again.

[0058] In this embodiment, determining whether the isolated network frequency continuously enters a steady state specifically involves setting a steady-state region holding time. When the real-time frequency recovers to a steady state and the holding time of the real-time frequency reaches the steady-state region holding time, the power replacement lockout is automatically released, and power replacement is performed again.

[0059] Meanwhile, this embodiment further avoids the problem that if power replacement is directly blocked when the frequency exceeds the limit, the power replacement will not be able to be executed; if power replacement is not restricted, the signs of the frequency modulation power increment and the replacement power are opposite, which will cause the output commands of each adjustable resource to contradict each other and interfere with frequency stability.

[0060] Secondly, this embodiment also provides a hierarchical control architecture for implementing the so-called isolated network power replacement method, including a co-control master station and a co-control substation; The main control station is used to collect the operating status information of the isolated grid, receive power replacement instructions issued by the power grid dispatch, execute steady-state control strategies and transient control strategies, generate power instructions, and send the power instructions to each control substation. The co-control substation is set up on each adjustable resource. It is used to receive power commands from the co-control master station and send them to each controlled device to execute the power commands. It also collects the operating data of each controlled device and sends the operating data to the co-control master station to provide feedback on the execution status of the controlled devices.

[0061] Figure 4 As shown, this embodiment implements a multi-modal collaborative power replacement control method for multiple types of source and load in isolated networks by deploying a collaborative control master station, a collaborative control substation, a dual-link communication system based on IEC61850, and computer programs deployed on the collaborative control master station and the collaborative control substation.

[0062] In this embodiment, the hierarchical control architecture of the islanded power replacement method consists of the power grid, the co-control master station, multiple co-control substations, and various adjustable resources, from top to bottom. The power grid and the co-control master station communicate bidirectionally via the IEC61850-MMS protocol for power replacement signals, while the power grid transmits its frequency signals unidirectionally to the co-control master station via the IEC61850-GOOSE protocol. The co-control master station executes steady-state and transient control strategies and establishes communication links with co-control substations 1, 2, ..., n (where n is a positive integer) via a high-speed internal real-time bus. The co-control substations communicate bidirectionally with adjustable resources 1, 2, ..., n (where n is a positive integer) via the IEC61850-GOOSE protocol for controlled equipment status signals and control commands.

[0063] In this embodiment, a co-control master station is deployed to execute steady-state and transient control strategies to ensure the stability of multi-mode power replacement control in the isolated network. At this time, the co-control substation is used to apply status signals and control commands to the controlled equipment to improve the power control response speed and the transmission reliability of control commands.

[0064] In some embodiments, the master control station is connected to the power grid via an IEC61850-MMS protocol communication link and an IEC61850-GOOSE protocol communication link, and the sub-control station is connected to each controlled device via a communication link based on the IEC61850-GOOSE protocol.

[0065] In this embodiment, the master control station consists of a distributed controller and its associated power supply and network modules. It is capable of network communication and logical operations, and is responsible for interacting with the power grid, deploying steady-state and transient control strategies, and generating target power commands. The substation in this embodiment consists of a distributed controller, I / O modules, and their associated power supply and network modules. It can achieve rapid real-time communication with the master control station via a high-speed internal real-time bus between controllers. It can also perform bidirectional interaction with controlled devices via hardwiring and the GOOSE protocol, and is responsible for collecting status information of controlled devices and issuing target power commands to them.

[0066] Furthermore, in this embodiment, two communication links are set up between the actual control master station and the power grid: an IEC61850-MMS protocol communication link for high-capacity data communication, used for exchanging power replacement plans and other power grid data; and an IEC61850-GOOSE protocol communication link for millisecond-level fast communication, used for exchanging power grid frequency, voltage, and current. A communication link based on the IEC61850-GOOSE protocol is set up between the control substation and the controlled equipment for millisecond-level fast communication, used for transmitting power commands and controlled equipment status signals.

[0067] Thirdly, this embodiment also provides a multimodal islanded grid power displacement control system, including: The power replacement module is used to receive power replacement instructions from the power grid dispatching system and perform power replacement according to the instructions when the real-time frequency of the isolated grid enters a steady state. The steady-state control strategy execution module is used to execute the steady-state control strategy when the real-time frequency of the isolated network enters a quasi-steady state, and then continue to execute power replacement and apply the generated target power command to the adjustable resources. The transient control strategy execution module is used to execute transient control strategies and update target power commands when the real-time frequency of the isolated network enters a transient state, and then continue to execute power replacement and apply the generated target power commands to adjustable resources. The feedback adjustment module is used to continue monitoring the steady-state status of the islanded grid's real-time frequency. When the islanded grid's real-time frequency enters a steady state, it uses the power replacement control system to receive the power replacement command issued by the power grid dispatch center, and executes the power replacement according to the power replacement command until the power replacement is completed and the islanded grid's real-time frequency enters a steady state, at which point the islanded grid power replacement ends.

[0068] Specifically, the multi-mode islanded grid power replacement process in this embodiment includes: detecting and determining whether the real-time frequency of the islanded grid has entered a steady state; if so, sending a power replacement activation signal to the grid dispatch center via the coordinating master station, and waiting to receive the power replacement pulse and replacement power command P from the grid dispatch center. totalThe system determines whether the control master station has received the power replacement pulse. If not, it returns to the state where it is waiting to receive the power replacement pulse and replacement power command P from the power grid dispatching system. total If so, then calculate the base power P of each adjustable resource according to the preset allocation coefficient. ci During power replacement, the system detects and determines whether the real-time frequency of the isolated grid has entered a quasi-steady state. If so, it calculates the additional compensation power for each regulating resource based on the frequency deviation, then calculates the replacement power, collects the real-time power of each adjustable resource, and finally calculates and sends the target power command to each adjustable resource. If not, it directly calculates the replacement power, collects the real-time power of each adjustable resource, and finally calculates and sends the target power command to each adjustable resource. The status signals of each adjustable resource are fed back to the system waiting to receive the power replacement pulse and replacement power command P from the grid dispatch. total The system detects and determines whether power replacement is complete and the islanded frequency has entered a steady state. If not, the real-time frequency of the adjusted islanded network is used as the islanded frequency to be adjusted, and the system continues to determine whether the islanded frequency to be adjusted has entered a steady state. If yes, the islanded power replacement ends.

[0069] Thus, as Figure 5 As shown in this embodiment, the multimodal islanded power replacement control system executes power replacement and steady-state control strategies, and executes transient control strategies when the islanded grid enters a transient state. After updating the target power command, the updated target power command is sent to the adjustable resources, and power replacement is executed again. This can smooth the power change curve of the islanded grid power replacement process and greatly improve the anti-disturbance capability of the islanded grid power replacement process, thereby achieving real-time source-load balance of the islanded grid.

[0070] In the several embodiments provided in this application, it should be understood that the disclosed apparatus and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of modules is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple modules or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or modules may be electrical, mechanical, or other forms.

[0071] The modules described as separate components may or may not be physically separate. The components shown as modules may or may not be physical modules; that is, they may be located in one place or distributed across multiple network modules. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs.

[0072] Furthermore, the functional modules in the various embodiments of the present invention can be integrated into one processing module, or each module can exist physically separately, or two or more modules can be integrated into one module. The integrated modules described above can be implemented in hardware or as software functional modules.

[0073] If the integrated module is implemented as a software functional module and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention.

[0074] It should be noted that, for the sake of simplicity, the foregoing method embodiments are all described as a series of actions. However, those skilled in the art should understand that the present invention is not limited to the described order of actions, because according to the present invention, some steps can be performed in other orders or simultaneously. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and modules involved are not necessarily essential to the present invention.

[0075] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0076] In summary, although the present invention has been disclosed above with reference to preferred embodiments, the above preferred embodiments are not intended to limit the present invention. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the scope defined in the claims.

Claims

1. An isolated power replacement method, characterized by, include: When the real-time frequency of the isolated grid enters a steady state, the power replacement control system receives the power replacement command issued by the grid dispatch and executes the power replacement according to the power replacement command. When the real-time frequency of the isolated network enters a quasi-steady state, a steady-state control strategy is executed, and the power substitution is then performed, with the generated target power command applied to the adjustable resources. When the real-time frequency of the isolated network enters a transient state, a transient control strategy is executed, the target power command is updated, the power replacement is executed again, and the generated target power command is applied to the adjustable resources. Continue to monitor the steady-state status of the isolated grid's real-time frequency, and when the isolated grid's real-time frequency enters a steady state, use the power replacement control system to receive the power replacement command issued by the power grid dispatch, execute the power replacement according to the power replacement command, until the power replacement is completed and the isolated grid's real-time frequency enters a steady state, and then end the isolated grid power replacement.

2. The islanded power replacement method of claim 1, wherein, Also includes: If the real-time frequency of the isolated network does not enter a quasi-steady state, power substitution will continue to be performed, and the generated target power command will be applied to the adjustable resources. If the real-time frequency of the isolated network does not enter a transient state, power substitution will continue to be performed, and the generated target power command will be applied to the adjustable resources.

3. The islanded grid power replacement method according to claim 1, characterized in that, The steps for determining that the real-time frequency of the isolated network has entered a steady state include: When the real-time frequency of the isolated network is between the preset steady-state lower limit and the preset steady-state upper limit, it is determined that the real-time frequency of the isolated network has entered a steady state.

4. The islanded grid power replacement method according to claim 3, characterized in that, The steps for determining that the real-time frequency of the isolated network has entered a quasi-steady state include: When the real-time frequency is greater than the preset transient lower limit and less than or equal to the preset steady-state lower limit, or when the real-time frequency is greater than or equal to the preset steady-state upper limit and less than the preset transient upper limit, it is determined that the real-time frequency of the isolated network has entered a quasi-steady state, wherein the preset transient lower limit is less than the preset steady-state lower limit and the preset steady-state upper limit is less than the preset transient upper limit.

5. The islanded grid power replacement method according to claim 4, characterized in that, The steps for determining that the real-time frequency of the isolated network has entered a transient state include: When the real-time frequency is less than or equal to the preset transient lower limit and the real-time frequency is greater than or equal to the preset transient upper limit, the real-time frequency of the isolated network enters a transient state.

6. The islanded grid power replacement method according to claim 1, characterized in that, When the real-time frequency of the isolated network enters a quasi-steady state, a steady-state control strategy is implemented, including: The rated frequency of the isolated grid is preset, the frequency deviation between the real-time frequency of the isolated grid and the rated frequency of the isolated grid is calculated, and the additional compensation power is calculated using the frequency deviation. The base power is superimposed on the additional compensation power to obtain the replacement power; Obtain the real-time power of each of the adjustable resources, superimpose the replacement power with the real-time power of each of the adjustable resources, and generate the target power command.

7. The islanded grid power replacement method according to claim 6, characterized in that, When the real-time frequency of the isolated network enters a transient state, a transient control strategy is executed, including: The frequency modulation power increment is calculated based on the frequency deviation. A preset frequency modulation priority and frequency modulation allocation ratio are used to decompose the frequency modulation power increment into the frequency modulation power of each of the adjustable resources. If the sign direction of the frequency modulation power increment is the same as that of the replacement power, then the frequency modulation power increment is superimposed on the replacement power, and the target power command is updated. If the sign direction of the frequency modulation power increment is opposite to that of the displacement power, the displacement power is locked and the target power command is updated.

8. The islanded grid power replacement method according to claim 7, characterized in that, The updated target power instruction, followed by the continued execution of the power replacement, includes: The updated target power command is issued to each of the adjustable resources; A preset steady-state region holding time is set. When the real-time frequency recovers to the steady state and the holding time of the real-time frequency reaches the steady-state region holding time, the lockout of the replacement power is automatically released, and the power replacement is performed again.

9. A hierarchical control architecture for implementing the islanded power replacement method as described in any one of claims 1-8, characterized in that, Including the main control station and the sub-control stations; The co-control master station is used to collect the operating status information of the isolated grid, receive the power replacement command issued by the power grid dispatch, execute the steady-state control strategy and the transient control strategy, generate power commands, and send the power commands to each of the co-control substations; The co-control substation is set on each of the adjustable resources, and is used to receive power commands from the co-control master station and send them to each controlled device to execute the power commands, as well as to collect the operating data of each controlled device and send the operating data to the co-control master station to provide feedback on the execution status of the controlled devices.

10. The hierarchical control architecture according to claim 9, characterized in that, The master control station is connected to the power grid via an IEC61850-MMS protocol communication link and an IEC61850-GOOSE protocol communication link. The substation is connected to each of the controlled devices via a communication link based on the IEC61850-GOOSE protocol.

11. A multimodal islanded grid power displacement control system, characterized in that, include: The power replacement module is used to receive power replacement instructions issued by the power grid dispatching system when the real-time frequency of the isolated grid enters a steady state, and to execute the power replacement according to the power replacement instructions. The steady-state control strategy execution module is used to execute the steady-state control strategy when the real-time frequency of the isolated network enters a quasi-steady state, and then continue to execute the power replacement, and apply the generated target power command to the adjustable resources; The transient control strategy execution module is used to execute the transient control strategy and update the target power command when the real-time frequency of the isolated network enters a transient state, and then continue to execute the power replacement and apply the generated target power command to the adjustable resources. The feedback adjustment module is used to continue monitoring the steady-state status of the isolated grid's real-time frequency. When the isolated grid's real-time frequency enters a steady state, it uses the power replacement control system to receive the power replacement command issued by the power grid dispatching system, executes the power replacement according to the power replacement command, and continues until the power replacement is completed and the isolated grid's real-time frequency enters a steady state, at which point the isolated grid power replacement ends.

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