Weakly connected wind-solar-storage microgrid operation optimization method and system

Abstract

The present invention relates to a weakly connected wind, solar and storage microgrid operation optimization method and system, the method comprising: obtaining data required for model construction; taking the minimum cost within the operation cycle as the goal, considering the constraints including power balance constraints, new energy operation constraints, energy storage operation constraints, and interconnection line transmission constraints, and establishing a wind, solar and storage microgrid grid-connected operation optimization model; taking the minimum power supply loss within the fault protection period as the goal, considering the constraints including power balance constraints, new energy operation constraints, energy storage operation constraints, and load constraints, and considering the new energy prediction deviation, establishing a wind, solar and storage microgrid off-grid operation optimization model; combining the above two models to construct a wind, solar and storage microgrid operation model that considers fault protection; calculating the operation decision within the operation cycle based on the constructed wind, solar and storage microgrid operation model, and executing the first-point decision result. The method and system combine the grid-connected operation model and the off-grid operation model, which is conducive to taking into account both the operation cost and reliability of the microgrid.

Description

Technical Field

[0001] The present invention belongs to the technical field of microgrid operation control, and specifically relates to a weakly connected wind-solar-storage microgrid operation optimization method and system. Background Art

[0002] A weakly connected microgrid refers to a microgrid that is connected to the distribution network only through a single-circuit tie line. Its structure is as follows: Figure 2 As shown. When the interconnection line is disconnected due to a fault, it is necessary to rely on wind, solar, and storage power sources within the microgrid for power supply. Affected by factors such as random fluctuations in renewable energy output, power supply reliability is a difficult point in the operation and scheduling of weakly connected microgrids. During the grid-connected operation phase, how to arrange the wind, solar, and storage operation strategy within the microgrid to achieve optimal economic efficiency and reserve sufficient energy storage capacity to meet the power supply demand in the event of a possible line failure is of great research significance. Traditional microgrid grid-connected operation methods focus more on studying how to control the charging and discharging of energy storage to obtain more economic benefits, without considering how to rely on wind, solar, and storage for reliable power supply after a fault; or by using a relatively rough method of retaining a fixed amount of energy storage to meet the electricity demand for a certain period of time in the future, failing to dynamically adjust according to the forecast results of renewable energy, and having poor flexibility. Summary of the Invention

[0003] The purpose of the present invention is to provide a method and system for optimizing the operation of a weakly connected wind-solar-storage microgrid, which is conducive to balancing the operating cost and reliability of the microgrid.

[0004] To achieve the above objectives, the present invention adopts a technical solution: a weakly connected wind-solar-storage microgrid operation optimization method, comprising:

[0005] Obtain the data required to build the model, including forecast data, measured data, equipment parameters, electricity price data, and forecast deviation data;

[0006] With the goal of minimizing cost within the operation cycle, a wind-solar-storage microgrid grid-connected operation optimization model is established by considering constraints including power balance constraints, renewable energy operation constraints, energy storage operation constraints, and interconnection line transmission constraints.

[0007] With the goal of minimizing power supply loss during the fault protection period, considering constraints including power balance constraints, renewable energy operation constraints, energy storage operation constraints, and load constraints, and considering renewable energy forecast deviations, an off-grid operation optimization model for wind, solar, and energy storage microgrids is established.

[0008] Combining the wind-solar-storage microgrid grid-connected operation optimization model and the wind-solar-storage microgrid off-grid operation optimization model, a wind-solar-storage microgrid operation model that takes fault protection into consideration is constructed;

[0009] Based on the constructed wind-solar-storage microgrid operation model, the operation decisions within the operation cycle are calculated and the first-point decision results are executed.

[0010] Furthermore, the forecast data includes short-term forecast results of new energy output on the same day and the next day, ultra-short-term forecast results of new energy output on the same day and the next day, important load forecast results on the same day and the next day, and general load forecast results on the same day and the next day; the measured data includes wind power generation power, photovoltaic power generation power, important load value, general load value and energy storage power at the current moment; the equipment parameters include the maximum transmission power of the interconnection line, the maximum charging and discharging power of energy storage, the maximum and minimum storage power of energy storage, energy storage charging and discharging efficiency and energy storage power self-loss coefficient; the electricity price data includes the electricity sales price within the microgrid, the electricity purchase price of the large power grid, the electricity sales price of the large power grid and the energy storage cost per kilowatt-hour; the forecast deviation data includes wind power forecast deviation and photovoltaic forecast deviation; the data required for calculation also includes peak, flat and valley time period information, fault supply duration, and the power required for black start after a fault.

[0011] Furthermore, the objective function of the wind-solar-storage microgrid grid-connected operation optimization model is:

[0012]

[0013] Where t0, t d2 Respectively represent the start and end time of the operation cycle; c load 、c out 、 c ES They are the price of electricity sold within the microgrid, the price of electricity sold by the microgrid to the large grid, the price of electricity purchased by the microgrid from the large grid, and the energy storage operation cost; are the forecast values of important load and general load respectively; P t out 、P t in P is the power sold to the large power grid and the power purchased from the large power grid respectively; t ES,c 、P t ES,d They are energy storage charging power and energy storage discharging power respectively;

[0014] The power balance constraint of the wind-solar-storage microgrid grid-connected operation optimization model is:

[0015]

[0016] Where, P t W 、P t S They are wind power generation power and photovoltaic power generation power respectively;

[0017] The new energy operation constraints of the wind-solar-storage microgrid grid-connected operation optimization model are:

[0018]

[0019]

[0020] Where, P t W,fore 、P t S,fore They are wind power forecast output and photovoltaic forecast output respectively;

[0021] The energy storage operation constraints of the wind-solar-storage microgrid grid-connected operation optimization model include energy storage charging and discharging power upper limit, energy storage power constraint, and energy storage charging and discharging state constraint, specifically:

[0022]

[0023]

[0024]

[0025]

[0026]

[0027]

[0028] Where, P ES,max is the upper limit of energy storage power generation and discharge power; γ t is the charge and discharge state constraint, 1 indicates energy storage charging, and 0 indicates energy storage discharging; is the energy storage capacity; η ES ,η c ,η d are the energy storage self-loss coefficient, charging efficiency, and discharging efficiency respectively; Δt is the time resolution; E t0 E is the energy storage capacity at the initial moment; ES,max is the maximum energy storage capacity;

[0029] The tie line transmission constraints of the wind-solar-storage microgrid grid-connected operation optimization model are:

[0030]

[0031]

[0032] Where, P line It is the maximum transmittable power of the line connecting the microgrid and the distribution network.

[0033] Furthermore, the objective function of the off-grid operation optimization model of the wind-solar-storage microgrid is:

[0034]

[0035] Where, δ 1 , δ 2 They are the penalty coefficient for loss of important loads and the reward coefficient for supply of general loads respectively; is the load shedding value for important loads; For general load supply value; set δ 1 Greater than δ 2 , so that important loads are supplied first during the off-grid operation phase;

[0036] The power balance constraint of the off-grid operation optimization model of the wind-solar-storage microgrid is:

[0037]

[0038] Where, are the wind power generation power, photovoltaic power generation power, energy storage discharge power, energy storage charging power, and important load supply value at time k after the tie line fault at time f;

[0039] The new energy operation constraints of the wind-solar-storage microgrid off-grid operation optimization model are:

[0040]

[0041]

[0042] Where, are the predicted output conversion coefficients of wind power and photovoltaic power respectively;

[0043] The energy storage operation constraints of the off-grid operation optimization model of the wind-solar-storage microgrid include the upper limit of energy storage charge and discharge power, energy storage capacity constraints, energy storage charge and discharge state constraints, and energy storage capacity transition constraints, specifically:

[0044]

[0045]

[0046]

[0047]

[0048]

[0049]

[0050] Where, γ f,k 、 They are the energy storage charging and discharging state and energy storage capacity under fault scenarios respectively; ΔE ESThe power required for a black start after a fault. After the tie line is disconnected, the power required for a black start after a fault is completely provided by energy storage. The energy storage capacity at time f before the fault is equal to the capacity at the same time in the grid-connected operation model; the energy storage capacity required after the fault is ΔE ES Used to achieve system black start, and then the energy storage capacity is Reduce to and enter off-grid operation;

[0051] The load constraints of the off-grid operation optimization model of the wind-solar-storage microgrid are:

[0052]

[0053]

[0054]

[0055] Where, It is the general load removal value.

[0056] Furthermore, the wind power and photovoltaic power forecast output conversion coefficient Select as follows:

[0057] Based on historical forecasts and operating data, the historical forecast positive deviation is calculated using the following formula:

[0058]

[0059] Where, P i fore 、P i real The historical output forecast and actual value of new energy;

[0060] The historical forecast deviation ΔP i After the sequence is sorted from small to large, the value at the 95% position is recorded as ΔP 95％ , select the conversion factor and 1-ΔP 95％ .

[0061] Furthermore, the objective function of the wind-solar-storage microgrid operation model is:

[0062]

[0063] Furthermore, a rolling optimization method is adopted to make operation decisions. For each moment, the wind-solar-storage microgrid operation model is executed, but only the first point, that is, the operation decision at the current moment, is executed, including new energy output, energy storage charging and discharging power, and interconnection line transmission power; after entering the next moment, the wind-solar-storage microgrid operation model is rebuilt to obtain a new decision-making plan, and the influence of uncertain factors is coped with by rolling updating the operation decision.

[0064] The present invention also provides a weakly connected wind-solar-storage microgrid operation optimization system for implementing the above method, comprising:

[0065] Data acquisition module, used to obtain the data required to build the model;

[0066] Grid-connected model construction module, used to build a wind, solar, and storage microgrid grid-connected operation optimization model;

[0067] Off-grid model construction module, used to build off-grid operation optimization model of wind, solar and storage microgrid;

[0068] A comprehensive model building module is used to combine the wind-solar-storage microgrid grid-connected operation optimization model and the wind-solar-storage microgrid off-grid operation optimization model to build a wind-solar-storage microgrid operation model that takes fault protection into account; and

[0069] The operation optimization module is used to calculate the operation decisions within the operation cycle based on the constructed wind, solar and storage microgrid operation model and execute the first-point decision results.

[0070] The present invention also provides a computer-readable storage medium on which computer program instructions that can be executed by a processor are stored. When the processor executes the computer program instructions, the above-mentioned method steps can be implemented.

[0071] The present invention also provides a weakly connected wind-solar-storage microgrid operation optimization device, comprising a memory, a processor, and computer program instructions stored in the memory and capable of being executed by the processor. When the processor executes the computer program instructions, the above-mentioned method steps can be implemented.

[0072] Compared with the existing technology, the present invention has the following beneficial effects: it provides a weakly connected wind-solar-storage microgrid operation optimization method and system. This method and system introduce an off-grid operation model on the basis of the traditional economically optimal grid-connected operation model, and constructs a wind-solar-storage microgrid operation model that takes fault protection into consideration, so that the obtained operation decision can take into account the economic goals of grid-connected operation and the power supply guarantee requirements of off-grid operation after a fault, thereby improving the economy and reliability of microgrid operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0073] Figure 1Flowchart for implementing the operation optimization method of a weakly connected wind-solar-storage microgrid according to an embodiment of the present invention;

[0074] Figure 2 Schematic diagram of the wind-solar-storage microgrid structure in an embodiment of the present invention;

[0075] Figure 3 Schematic diagram of microgrid operation decision-making in an embodiment of the present invention;

[0076] Figure 4 This is a schematic diagram of a new energy output prediction curve in an embodiment of the present invention;

[0077] Figure 5 This is a schematic diagram of a fault period in an embodiment of the present invention;

[0078] Figure 6 This is a load / wind power / photovoltaic curve diagram in an embodiment of the present invention;

[0079] Figure 7 The operation results of the grid-connected operation optimization model in the embodiment of the present invention;

[0080] Figure 8 Microgrid operation results in an embodiment of the present invention. DETAILED DESCRIPTION

[0081] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0082] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present application belongs.

[0083] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0084] Aiming at the difficulty in making grid-connected operation decisions for weakly-connected wind-solar-storage microgrids, this invention proposes an operation strategy optimization method for weakly-connected wind-solar-storage microgrids that takes fault-proof power supply into consideration. This method takes into account both the operation goal of maximizing economic benefits during the grid-connected period and the power supply demand of important loads during faults, optimizes microgrid operation decisions, and updates the operation plan in a rolling manner based on the new energy power forecast results to ensure that the operation plan is accurate and reasonable.

[0085] like Figure 1As shown, the operation optimization method of the weakly connected wind-solar-storage microgrid provided in this embodiment includes the following steps:

[0086] Step 1: Obtain the data required to build the model, including forecast data, measured data, equipment parameters, electricity price data, and forecast deviation data. Specifically,

[0087] 1) Forecast data: short-term forecast results of renewable energy output for the current day and the next day, ultra-short-term forecast results of renewable energy output, important load forecast results for the current day and the next day, and general load forecast results for the current day and the next day;

[0088] 2) Measured data: current wind power generation capacity, photovoltaic power generation capacity, important load value, general load value, and energy storage capacity;

[0089] 3) Equipment parameters: maximum transmission power of the tie line, maximum charging / discharging power of energy storage, maximum / minimum storage capacity of energy storage, energy storage charging / discharging efficiency, and energy storage power self-consumption coefficient;

[0090] 4) Electricity price data: electricity sales price within the microgrid, electricity purchase price from the main grid (differentiated between peak, flat, and off-peak periods), electricity sales price from the main grid, and energy storage cost per kilowatt-hour;

[0091] 5) Forecast deviation data: For wind power and photovoltaic forecast deviation, the forecast deviation at a 95% confidence level can be calculated based on historical operating data. When historical data is insufficient, typical values can be selected;

[0092] 6) Other data: Peak / flat / valley time period information, fault protection duration, power required for black start after a fault, etc.

[0093] Step 2: With the goal of minimizing the cost within the operation cycle, considering the constraints including power balance constraints, new energy operation constraints, energy storage operation constraints, and interconnection line transmission constraints, a wind-solar-storage microgrid grid-connected operation optimization model is established.

[0094] In this embodiment, the microgrid operation decision is as follows: Figure 3 To leverage the cross-period regulation capabilities of energy storage and dynamically adjust power consumption based on new energy forecast results, this embodiment selects the current time to midnight the following day as the operating cycle, denoted by T, with a time resolution of 15 minutes, to construct a grid-connected operation optimization model.

[0095] The objective function of the wind-solar-storage microgrid grid-connected operation optimization model is:

[0096]

[0097] Where t0, t d2 Respectively represent the start and end time of the operation cycle. In this embodiment, they represent the current time and 24:00 the next day; c load 、cout 、 c ES They are the price of electricity sold within the microgrid, the price of electricity sold from the microgrid to the large grid, the price of electricity purchased from the microgrid to the large grid, and the energy storage operation cost. The price of electricity sold from the microgrid to the large grid can be set according to peak, flat and valley periods. are the forecast values of important load and general load respectively; P t out 、P t in P is the power sold to the large power grid and the power purchased from the large power grid respectively; t ES,c 、P t ES,d They are energy storage charging power and energy storage discharging power respectively;

[0098] The power balance constraint of the wind-solar-storage microgrid grid-connected operation optimization model is:

[0099]

[0100] Where, P t W 、P t S They are wind power generation power and photovoltaic power generation power respectively.

[0101] The new energy operation constraints of the wind-solar-storage microgrid grid-connected operation optimization model are:

[0102]

[0103]

[0104] Where, P t W,fore 、P t S,fore They are wind power forecast output and photovoltaic forecast output respectively. Taking wind power forecast output as an example, Figure 4 As shown in the figure, the predicted output of renewable energy sources consists of three parts: 1) the actual power available at the current moment; 2) the ultra-short-term predicted output for 15 minutes to 4 hours after the current moment; this ultra-short-term predicted output is updated before each optimization run; and 3) the short-term predicted output for 4 hours to 24:00. By combining the actual and predicted output values of renewable energy sources at different stages, the predicted output is closer to the actual value, improving the feasibility of decision-making.

[0105] The energy storage operation constraints of the wind-solar-storage microgrid grid-connected operation optimization model include energy storage charging and discharging power upper limit, energy storage power constraint, and energy storage charging and discharging state constraint, specifically:

[0106]

[0107]

[0108]

[0109]

[0110]

[0111]

[0112] Where, P ES,max is the upper limit of energy storage power generation and discharge power; γ t is the charge and discharge state constraint, 1 indicates energy storage charging, and 0 indicates energy storage discharging; is the energy storage capacity; η ES ,η c ,η d are the energy storage self-consumption coefficient, charging efficiency, and discharging efficiency respectively; Δt is the time resolution, which is 15 minutes in this embodiment; E t0 E is the energy storage capacity at the initial moment; ES,max The maximum energy storage capacity.

[0113] The tie line transmission constraints of the wind-solar-storage microgrid grid-connected operation optimization model are:

[0114]

[0115]

[0116] Where, P line It is the maximum transmittable power of the line connecting the microgrid and the distribution network.

[0117] Step 3: With the goal of minimizing power supply loss during the fault protection period, considering the constraints including power balance constraints, new energy operation constraints, energy storage operation constraints, and load constraints, and considering the new energy prediction deviation, an off-grid operation optimization model of the wind, solar and energy storage microgrid is established.

[0118] Since the time of failure occurrence is uncertain, this embodiment adopts an exhaustive method to check the power supply capability after a failure occurs at all times in the operation cycle.

[0119] In this embodiment, the fault period diagram in the off-grid operation optimization model is as follows: Figure 5 When a transmission line failure occurs at each moment, the microgrid needs to rely on the internal wind, solar and storage equipment to maintain reliable power supply for a certain period of time (denoted as H). The fault time is denoted as f, and the guaranteed power supply interval is T f=[f,f+H]. For example, if a fault occurs at the fifth moment in the grid-connected operation cycle, the time interval for guaranteed power supply is T5 = [5,5+H]. During the guaranteed power supply period, it is necessary to ensure stable power supply to critical loads within the microgrid. If wind and solar resources are sufficient, general loads can be supplied as much as possible.

[0120] The goal of the off-grid operation optimization model of the wind-solar-storage microgrid is to minimize the loss of important loads in all fault intervals and maximize the supply of general loads. Its objective function is:

[0121]

[0122] Where, δ 1 , δ 2 They are the penalty coefficient for loss of important loads and the reward coefficient for supply of general loads respectively; is the load shedding value for important loads; For general load supply value; set δ 1 Greater than δ 2 , so that important loads can be supplied first during the off-grid operation phase.

[0123] The power balance constraint of the off-grid operation optimization model of the wind-solar-storage microgrid is:

[0124]

[0125] Where, They are respectively the wind power generation power, photovoltaic power generation power, energy storage discharge power, energy storage charging power and important load supply value at time k after the interconnection line fault at time f.

[0126] The new energy operation constraints of the wind-solar-storage microgrid off-grid operation optimization model are:

[0127]

[0128]

[0129] Where, are the predicted output conversion coefficients of wind power and photovoltaic power respectively.

[0130] Because future renewable energy output cannot be accurately predicted, there is often a discrepancy between predicted and actual output. If operational planning during a fault period is based solely on predicted output, the actual output may be less than the predicted value, and the total power output may be less than the load. Therefore, from a conservative perspective, the predicted output should be discounted and operational decisions made based on the lower value, such as 90% * predicted output.

[0131] The conversion factor can be calculated based on historical forecasts and operating data, for example, by referring to the 95% quantile of historical forecast deviations. The specific method is:

[0132] First calculate the historical forecast positive deviation:

[0133]

[0134] Where, P i fore 、P i real It is the historical output forecast and actual value of new energy.

[0135] The 95% quantile of the forecast deviation is: i After the sequence is sorted from small to large, the value at the 95% position is recorded as ΔP 95％ , select the conversion factor and 1-ΔP 95％ .

[0136] If historical forecasts and operational data are limited, typical values can be selected based on standards or operational experience. Conversion factors should be selected separately for wind power and photovoltaic power, and for short-term and ultra-short-term forecasts, respectively.

[0137] The energy storage operation constraints of the off-grid operation optimization model of the wind-solar-storage microgrid include the upper limit of energy storage charge and discharge power, energy storage capacity constraints, energy storage charge and discharge state constraints, and energy storage capacity transition constraints, specifically:

[0138]

[0139]

[0140]

[0141]

[0142]

[0143]

[0144] Where, γ f,k 、 They are the energy storage charging and discharging state and energy storage capacity under fault scenarios respectively; ΔE ES The power required for a black start after a fault. After the tie line is disconnected, the power required for a black start after a fault is completely provided by energy storage. The energy storage capacity at time f before the fault is equal to the capacity at the same time in the grid-connected operation model; the energy storage capacity required after the fault is ΔE ES Used to achieve system black start, and then the energy storage capacity is Reduce to And enter off-grid operation.

[0145] The load constraints of the off-grid operation optimization model of the wind-solar-storage microgrid are:

[0146]

[0147]

[0148]

[0149] Where, It is the general load removal value.

[0150] Step 4: Combine the wind-solar-storage microgrid grid-connected operation optimization model and the wind-solar-storage microgrid off-grid operation optimization model to construct a wind-solar-storage microgrid operation model that takes fault protection into consideration.

[0151] The objective function of the wind-solar-storage microgrid operation model is:

[0152]

[0153] Step 5: Calculate the operation decision within the operation cycle based on the constructed wind-solar-storage microgrid operation model and execute the first-point decision result.

[0154] In this embodiment, a rolling optimization approach is used to make operational decisions. At each moment, the wind-solar-storage microgrid operational model is executed, but only the operational decision for the first point (i.e., the current moment) is executed, including the renewable energy output, energy storage charging and discharging power, and tie-line transmission power. At the next moment, steps 1-4 are re-executed to construct the wind-solar-storage microgrid operational model and obtain a new decision solution. This rolling update of operational decisions addresses the impact of uncertainties such as renewable energy forecast deviations.

[0155] This embodiment also provides a weakly coupled wind-solar-storage microgrid operation optimization system for implementing the above method, including:

[0156] Data acquisition module, used to obtain the data required to build the model;

[0157] Grid-connected model construction module, used to build a wind, solar, and storage microgrid grid-connected operation optimization model;

[0158] Off-grid model construction module, used to build off-grid operation optimization model of wind, solar and storage microgrid;

[0159] A comprehensive model building module is used to combine the wind-solar-storage microgrid grid-connected operation optimization model and the wind-solar-storage microgrid off-grid operation optimization model to build a wind-solar-storage microgrid operation model that takes fault protection into account; and

[0160] The operation optimization module is used to calculate the operation decisions within the operation cycle based on the constructed wind, solar and storage microgrid operation model and execute the first-point decision results.

[0161] This embodiment further provides a computer-readable storage medium on which computer program instructions that can be executed by a processor are stored. When the processor executes the computer program instructions, the above-mentioned method steps can be implemented.

[0162] This embodiment also provides a weakly connected wind-solar-storage microgrid operation optimization device, which is characterized in that it includes a memory, a processor, and computer program instructions stored in the memory and capable of being executed by the processor. When the processor executes the computer program instructions, the above-mentioned method steps can be implemented.

[0163] The effectiveness of the present invention will be described below by way of examples.

[0164] A microgrid has 6MW of wind power, 2MW of photovoltaic power, and 2MW / 4MWh of energy storage. The key technical and economic parameters are shown in Table 1. The load, wind power, and photovoltaic conditions on the day and the next day of optimization operation are as follows: Figure 6 shown.

[0165] Table 1 Key technical and economic parameters

[0166]

[0167]

[0168] The grid-connected operation optimization model constructed in step 2 of this method is used to optimize the microgrid operation strategy moment by moment. The operation decision on the first day is as follows: Figure 7 As shown in the figure. It can be seen that before time 67 (i.e., 4:30 PM), the available wind and photovoltaic power generation within the microgrid exceeds the load. After meeting the microgrid's internal electricity needs, the excess power is transmitted to the main grid via the interconnection line. After 4:30 PM, wind and photovoltaic power generation falls short of the load, necessitating purchases from the main grid or energy storage discharge to supplement the load's power shortage. Since the main grid's electricity purchase costs decrease from peak to normal and off-peak hours, and energy storage capacity is limited, prioritizing energy storage during peak hours can reduce operating costs. Therefore, during peak hours, energy storage discharges, while during off-peak hours, electricity is purchased from the main grid. During normal hours, some power is supplied by energy storage and some by the main grid.

[0169] At the last moment, the energy storage capacity was 1.12MWh, not reaching the lower limit. This is because the operating cycle from the current moment to midnight the next day is considered when making decisions at each moment, thus favoring the use of reserved energy storage capacity to meet the next day's operational needs. This approach avoids short-sighted decisions based solely on the current situation.

[0170] Therefore, the grid-connected operation portion of the proposed model can select the most economically efficient strategy based on the real-time status and forecast results, achieving the highest-revenue operation. The full-day operating profit for this example was 23,284 yuan.

[0171] On this basis, considering the off-grid fault protection factor, the model proposed by this method is used to optimize the microgrid operation strategy moment by moment. The operation decision is as follows: Figure 8 After the off-grid model is introduced, the power generation of renewable energy is predicted to be low the next day (see Figure 6 To ensure sufficient energy storage to power the microgrid in a black start and stabilize wind and solar power for two hours after a fault, the available energy storage capacity was further reduced. Therefore, in the operational results, when the output of renewable energy within the microgrid falls below the load, energy storage discharge occurs only during peak hours. During normal and off-peak hours, electricity is purchased from external sources to supplement the power shortage.

[0172] The full-day revenue from this operating strategy was 23,055 yuan, slightly lower than the revenue without off-grid operation. The final stored energy was 1.57 MWh, higher than the 1.12 MWh without off-grid operation. This method leaves more stored energy to cope with potential failures and offers higher reliability. Therefore, the present invention balances the economic benefits of grid-connected operation with the reliability of off-grid operation, resulting in a comprehensive and optimal operating strategy.

[0173] Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0174] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the steps in the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0175] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0176] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0177] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other manner. Any person skilled in the art may utilize the above-disclosed technical content to modify or modify the present invention into equivalent embodiments. However, any simple modifications, equivalent variations, and modifications to the above embodiments that do not depart from the technical content of the present invention and are based on the technical essence of the present invention remain within the scope of protection of the present invention.

Claims

1. A weakly connected wind-solar-storage microgrid operation optimization method, characterized in that: include: Obtain the data required to build the model, including forecast data, measured data, equipment parameters, electricity price data, and forecast deviation data; With the goal of minimizing cost within the operation cycle, a wind-solar-storage microgrid grid-connected operation optimization model is established by considering constraints including power balance constraints, renewable energy operation constraints, energy storage operation constraints, and interconnection line transmission constraints. With the goal of minimizing power supply loss during the fault protection period, considering constraints including power balance constraints, renewable energy operation constraints, energy storage operation constraints, and load constraints, and considering renewable energy forecast deviations, an off-grid operation optimization model for wind, solar, and energy storage microgrids is established. Combining the wind-solar-storage microgrid grid-connected operation optimization model and the wind-solar-storage microgrid off-grid operation optimization model, a wind-solar-storage microgrid operation model that takes fault protection into consideration is constructed; Calculate the operation decision within the operation cycle based on the constructed wind, solar and storage microgrid operation model and execute the first-point decision result; The objective function of the wind-solar-storage microgrid grid-connected operation optimization model is: Where t0, t d2 Respectively represent the start and end time of the operation cycle; c load 、c out 、 c ES They are the price of electricity sold within the microgrid, the price of electricity sold by the microgrid to the large grid, the price of electricity purchased by the microgrid from the large grid, and the energy storage operation cost; They are the forecast values of important load and general load respectively; They are respectively the power sold to the large power grid and the power purchased from the large power grid; They are energy storage charging power and energy storage discharging power respectively; The objective function of the off-grid operation optimization model of the wind-solar-storage microgrid is: Where, δ 1 , δ 2 They are the penalty coefficient for loss of important loads and the reward coefficient for supply of general loads respectively; is the load shedding value for important loads; For general load supply value; set δ 1 Greater than δ 2 , so that important loads are supplied first during the off-grid operation phase; The objective function of the wind-solar-storage microgrid operation model is:

2. The weakly connected wind-solar-storage microgrid operation optimization method according to claim 1 is characterized in that: The forecast data includes the short-term forecast results of new energy output on the same day and the next day, the ultra-short-term forecast results of new energy output on the same day and the next day, the important load forecast results on the same day and the next day, and the general load forecast results on the same day and the next day; the measured data includes the wind power generation power, photovoltaic power generation power, important load value, general load value and energy storage power at the current moment; the equipment parameters include the maximum transmission power of the interconnection line, the maximum charging and discharging power of energy storage, the maximum and minimum storage power of energy storage, the energy storage charging and discharging efficiency and the energy storage power self-loss coefficient; the electricity price data includes the electricity sales price within the microgrid, the electricity purchase price of the large power grid, the electricity sales price of the large power grid and the energy storage cost per kilowatt-hour; the forecast deviation data includes wind power forecast deviation and photovoltaic forecast deviation; the required data also includes peak, flat and valley time period information, fault supply duration, and the power required for black start after a fault.

3. The method for optimizing the operation of a weakly connected wind-solar-storage microgrid according to claim 1, characterized in that: The power balance constraint of the wind-solar-storage microgrid grid-connected operation optimization model is: Where, They are wind power generation power and photovoltaic power generation power respectively; The new energy operation constraints of the wind-solar-storage microgrid grid-connected operation optimization model are: Where, They are wind power forecast output and photovoltaic forecast output respectively; The energy storage operation constraints of the wind-solar-storage microgrid grid-connected operation optimization model include energy storage charging and discharging power upper limit, energy storage power constraint, and energy storage charging and discharging state constraint, specifically: Where, P ES,max is the upper limit of energy storage power generation and discharge power; γ t is the charge and discharge state constraint, 1 indicates energy storage charging, and 0 indicates energy storage discharging; is the energy storage capacity; η ES ,η c ,η d are the energy storage self-loss coefficient, charging efficiency, and discharging efficiency respectively; Δt is the time resolution; E t0 E is the energy storage capacity at the initial moment; ES,max is the maximum energy storage capacity; The tie line transmission constraints of the wind-solar-storage microgrid grid-connected operation optimization model are: Where, P line It is the maximum transmittable power of the line connecting the microgrid and the distribution network.

4. The method for optimizing the operation of a weakly connected wind-solar-storage microgrid according to claim 3 is characterized in that: The power balance constraint of the off-grid operation optimization model of the wind-solar-storage microgrid is: Where, are the wind power generation power, photovoltaic power generation power, energy storage discharge power, energy storage charging power, and important load supply value at time k after the tie line fault at time f; The new energy operation constraints of the wind-solar-storage microgrid off-grid operation optimization model are: Where, are the predicted output conversion coefficients of wind power and photovoltaic power respectively; The energy storage operation constraints of the off-grid operation optimization model of the wind-solar-storage microgrid include the upper limit of energy storage charge and discharge power, energy storage capacity constraints, energy storage charge and discharge state constraints, and energy storage capacity transition constraints, specifically: Where, γ f,k 、 are the energy storage charging and discharging status and energy storage capacity under fault scenarios respectively; ΔE ES The power required for a black start after a fault. After the tie line is disconnected, the power required for a black start after a fault is completely provided by energy storage. The energy storage capacity at time f before the fault is equal to the capacity at the same time in the grid-connected operation model; the energy storage capacity required after the fault is ΔE ES Used to achieve system black start, and then the energy storage capacity is Reduce to and enter off-grid operation; The load constraints of the off-grid operation optimization model of the wind-solar-storage microgrid are: Where, It is the general load removal value.

5. The method for optimizing the operation of a weakly connected wind-solar-storage microgrid according to claim 4 is characterized in that: Wind power and photovoltaic forecast output conversion coefficient Select as follows: Based on historical forecasts and operating data, the historical forecast positive deviation is calculated using the following formula: Where, The historical output forecast and actual value of new energy; The historical forecast deviation ΔP i After the sequence is sorted from small to large, the value at the 95% position is recorded as ΔP 95％ , select the conversion factor and 1-ΔP 95％ .

6. The method for optimizing the operation of a weakly connected wind-solar-storage microgrid according to claim 4, characterized in that: A rolling optimization approach is used to make operational decisions. For each moment, the wind-solar-storage microgrid operation model is executed, but only the first point, that is, the operation decision at the current moment, is executed, including renewable energy output, energy storage charging and discharging power, and interconnection line transmission power. After entering the next moment, the wind-solar-storage microgrid operation model is rebuilt to obtain a new decision-making plan, and the impact of uncertain factors is dealt with by rollingly updating the operation decision.

7. A weakly connected wind-solar-storage microgrid operation optimization system for implementing the method according to any one of claims 1 to 6, characterized in that: include: Data acquisition module, used to obtain the data required to build the model; Grid-connected model construction module, used to build a wind, solar, and storage microgrid grid-connected operation optimization model; Off-grid model construction module, used to build off-grid operation optimization model of wind, solar and storage microgrid; A comprehensive model building module is used to combine the wind-solar-storage microgrid grid-connected operation optimization model and the wind-solar-storage microgrid off-grid operation optimization model to build a wind-solar-storage microgrid operation model that takes fault protection into account; as well as The operation optimization module is used to calculate the operation decisions within the operation cycle based on the constructed wind, solar and storage microgrid operation model and execute the first-point decision results.

8. A computer-readable storage medium storing computer program instructions that can be executed by a processor, wherein when the processor executes the computer program instructions, the method according to any one of claims 1 to 6 can be implemented.

9. A weakly connected wind-solar-storage microgrid operation optimization device, characterized in that: The method comprises a memory, a processor, and computer program instructions stored in the memory and capable of being executed by the processor. When the processor executes the computer program instructions, the method according to any one of claims 1 to 6 can be implemented.

Images