Cross - temporal and spatial flexible interconnection planning method based on multi - agricultural and pastoral zero - carbon parks and photovoltaics

Abstract

The present invention discloses a cross-temporal and spatial flexible interconnection planning method based on multiple agricultural and animal husbandry zero-carbon parks and photovoltaics, including: comparative analysis of the control strategies and applicable scopes of typical regional flexible interconnection systems, establishment of converter-based interconnection system operation power balance constraints; regional connectability analysis of inter-regional interconnection needs, construction of a regional flexible interconnection two-layer planning model; with the goal of maximizing photovoltaic utilization, the economic benefits of agricultural and animal husbandry zero-carbon parks, and the operating efficiency of distribution networks, construction of a photovoltaic-agricultural and animal husbandry park flexible interconnection two-layer joint planning model; solving the model to obtain regional photovoltaic access capacity and the optimal flexible interconnection plan, realizing photovoltaic configuration in the photovoltaic planning area and photovoltaic absorption and distribution network operation in the agricultural and animal husbandry zero-carbon park. The present invention improves the overall acceptance level of distributed photovoltaics in the distribution network from the planning level, can realize cross-temporal and spatial interaction between agricultural and animal husbandry parks and photovoltaic areas in the entire county, improves the absorption level of photovoltaics in the entire county, and also realizes the joint economic operation of multiple regions.

Description

Technical Field

[0001] The present invention relates to the field of multi-regional cross-temporal and spatial interaction, and specifically to a cross-temporal and spatial flexible interconnection planning method based on multiple agricultural and animal husbandry zero-carbon parks and photovoltaics. Background Art

[0002] To maximize the utilization of solar resources, relevant policies encourage regions to fully tap the capacity of distributed photovoltaic access. However, as the number of distributed photovoltaic access points continues to climb, its absorption has become a challenge for the optimized operation of low-voltage distribution networks. Affected by the characteristics of photovoltaic output and load, distribution areas are prone to transformer power reverse during periods of peak photovoltaic power generation. In some power supply areas, excessive photovoltaic capacity at 35kV substations has led to periodic reverse power supply at upstream substations, causing step-down distribution transformers to become step-up transformers during certain periods. This not only reduces the transformer's allowable transmission capacity but also significantly increases losses during transmission. Furthermore, power reverse can lead to safety hazards such as complex line protection devices and voltage violations at access points. Therefore, to ensure reliable and safe power supply to users, it is necessary to limit reverse power.

[0003] Due to the mismatch between solar resource conditions and load absorption capacity across distribution areas, using the proportion of distributed PV installed capacity to prevent regional power backflow is not universally applicable. Furthermore, for low-voltage areas with low loads and large PV capacity, or large loads and small PV capacity, matching source and load within a single area is not conducive to the development and utilization of the distribution area's potential solar resources. Furthermore, with the continued growth of DC resources such as distributed PV, electric vehicle charging stations, and small DC power devices, the operating conditions of low-voltage distribution areas have become increasingly complex and variable. The mismatch between source and load power characteristics within a region is prominent, leading to a widening difference in regional net load peaks and valleys, low overall utilization of distribution equipment, and insufficient capacity during peak load periods. Under the traditional radial connection model, each distribution area operates independently, with power exchange limited to within the area. The remaining transformer capacity and available source and load resources in adjacent areas cannot be shared, significantly limiting the flexibility and control of regional power.

[0004] Agricultural and pastoral parks are rich in organic waste. Their biogas power generation technology, which uses biomass waste resources as raw materials, has relatively fast start-up and shutdown characteristics and the ability to quickly adjust power generation output. Its highly flexible and controllable advantages can quickly supplement power output in the event of sudden power system failures or other equipment outages, and can also be coordinated and adjusted with other energy systems. Therefore, agricultural, forestry, and animal husbandry parks that integrate distributed biomass comprehensive utilization can promote the absorption of photovoltaic power throughout the county and alleviate the pressure on agricultural distribution network transformation. However, the timing production characteristics of various types of agricultural and pastoral parks vary, and the electricity-carbon coupling mechanism is unclear. This leads to high expansion and transformation costs for individual parks, difficult to manage and control the aggregation and complementarity of multiple parks, and difficult to autonomously manage regional distribution networks.

[0005] In response to the above problems, the applicant discovered that flexible interconnection technology can use power electronic transformers or converters and other equipment to achieve the division of AC and DC areas within the region, and build power interaction channels between adjacent distribution areas. Through the coordinated regulation of flexible equipment ports, interconnected areas can achieve load transfer and cross-regional photovoltaic consumption, which can not only improve the operating efficiency and safety of the system, but also provide greater possibilities for the development of distributed photovoltaic capacity in the entire regional distribution network. Therefore, how to explore the regional flexible interconnection economic operation and optimization planning of regional distribution networks based on flexible interconnection technology is an urgent problem to be solved. Summary of the Invention

[0006] In view of the deficiencies of the above-mentioned existing technologies, the technical problem to be solved by the present invention is: how to provide a cross-temporal and spatial flexible interconnection planning method based on multiple agricultural and pastoral zero-carbon parks and photovoltaics, improve the overall acceptance level of distributed photovoltaics in the distribution network within the agricultural and pastoral zero-carbon parks from the planning level, realize cross-temporal and spatial interaction between agricultural and pastoral parks and the photovoltaic areas of the entire county, improve the absorption level of photovoltaics in the entire county, and also realize the joint economic operation of multiple regions, thereby ensuring the effectiveness of the cross-temporal and spatial flexible interconnection planning of multiple agricultural and pastoral zero-carbon parks and photovoltaics.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0008] A cross-temporal and spatial flexible interconnection planning method based on multiple zero-carbon agricultural and animal husbandry parks and photovoltaics includes:

[0009] S1: Compare and analyze the control strategies and applicable scopes of typical regional flexible interconnection systems, and establish converter-based interconnection system operation power balance constraints;

[0010] S2: Based on the operating power balance constraints of the converter-based interconnected system, a regional connectivity analysis is conducted on the inter-regional interconnection demand, and then a converter-based two-level planning model for regional flexible interconnection is constructed;

[0011] S3: Based on the converter-based regional flexible interconnection two-tier planning model, a two-tier joint planning model for PV-agricultural and animal husbandry park flexible interconnection is constructed with the goal of maximizing PV utilization, the economic benefits of the agricultural and animal husbandry zero-carbon park, and the operational efficiency of the distribution network.

[0012] S4: Solve the photovoltaic-agricultural and animal husbandry park flexible interconnection two-layer joint planning model to obtain the regional photovoltaic access capacity and the optimal flexible interconnection plan, and then realize the photovoltaic configuration of the photovoltaic planning area and the photovoltaic absorption and distribution network operation of the agricultural and animal husbandry zero-carbon park based on the photovoltaic access capacity and the optimal flexible interconnection plan.

[0013] Preferably, in step S1, the converter-based interconnected system operation power balance constraint is established through the following steps:

[0014] S101: Compare the similarities and differences in the working principles, topologies, and control strategies of typical regional flexible interconnection systems, and analyze and determine the applicable scenarios of regional flexible interconnection systems;

[0015] S102: Analyze the flexible interconnection area of the converter based on the applicable scenarios of the regional flexible interconnection system, and then divide the flexible interconnection area into VSC commutation sub-area, AC sub-area and DC sub-area according to resource type, and establish power balance constraint equations for each sub-area.

[0016] Preferably, in step S102, the power balance constraint equation of each sub-area is as follows:

[0017] 1) Power balance constraint equation of VSC commutation sub-area

[0018]

[0019] Where: is the active power flowing into the VSC port from the AC region of region i at time t; is the active power flowing into the AC area from the VSC port of area i at time t; is the active power flowing into the VSC port from the DC region of region i at time t; is the active power flowing into the DC region from the VSC port of region i at time t; K vsc The loss factor for power exchange for VSC;

[0020]

[0021] Where: is the reactive power flowing into the VSC AC port in region i at time t; S i,vsc VSC capacity configured for region i;

[0022] 2) Power balance constraint equation of AC sub-area

[0023]

[0024]

[0025]

[0026]

[0027]

[0028] Where: and are the active power and reactive power on the low-voltage side of the transformer in region i at time t, respectively; and are the active power and reactive power on the high-voltage side of the transformer in region i at time t, respectively; are the active power and reactive power of AC load in area i at time ι respectively; P T0 、P TK , I T0 and U TK They represent the no-load loss, rated load loss, no-load current percentage and short-circuit voltage percentage of the transformer in area i respectively; β i (t), S i,T are the transformer load factor and transformer capacity in region i respectively;

[0029] 3) Power balance constraint equation of DC sub-region

[0030]

[0031] Where: P i,pv (t) represents the actual output of DPVG in region i at time t; is the power flowing on the line between regions i and j at time i, with the positive direction being the power flowing from region i to region j; π(i) is the set of all regions connected to region i; P i,pc (t) represents the DC load of area i at time t; and represents the charging and discharging power of the energy storage in region i at time t; It represents the flexible DC load transfer amount in region i at time t.

[0032] Preferably, the power balance constraint equation of each sub-area further includes:

[0033] 1) The self-supply model meets the following requirements:

[0034]

[0035] Where: represents the power flowing on the tie line between regions i and j at time t, with the positive direction being the power flowing from region i to region j; π(i) represents the set of all regions connected to region i;

[0036] 2) The photovoltaic cross-regional consumption model meets the following requirements:

[0037]

[0038] 3) The load transfer mode meets the following requirements:

[0039]

[0040] Preferably, in step S2, a converter-based regional flexible interconnection two-layer planning model is established through the following steps:

[0041] S201: Based on the interconnection demand index, the interconnection demand of different regions is judged and the regions are classified, and then the interconnection distance constraint is introduced to determine the possible interconnection combinations between different regions;

[0042] S202: Based on the flexible interconnection technology of converters, a two-layer planning model for regional flexible interconnection based on converters is established in combination with the interconnectable combinations between different regions to achieve optimal planning of interconnection schemes and interconnection transposition capacity.

[0043] Preferably, in step S2021, the steps of determining the connectable combinations between different regions are as follows:

[0044] 1) Calculate the maximum net load index and the minimum net load index;

[0045] The calculation formula is as follows:

[0046]

[0047]

[0048] Where: and Respectively represent the maximum net load index and the minimum net load index; and are the active and reactive power of the AC load at time t in region i under the s season scenario; is the maximum output of distributed photovoltaic power generation in region i at time t in the s season scenario; S i,T is the transformer capacity of area i;

[0049] 2) Based on the maximum net load factor and minimum net load factors, the possible interconnection combinations between different areas are analyzed as follows:

[0050] 2.1) Calculate the source and load characteristic curves, regional transformer parameters, and distances between different regions under different seasonal scenarios in each region;

[0051] 2.2) Calculate the maximum net load factor index T for each region's interconnection demand i load and minimum net load index P i pure ;

[0052] 2.3) Classify the regions: If T i load >0.8, classified into set φ f1 , otherwise it is classified into the set φ t1 If P i pure <0, included in the set φ f2, otherwise it is classified into the set φ t2 ;

[0053] 2.4) Set φ f1 With φ t1 The regions of φ are combined and φ f2 With φ t2 to combine the areas;

[0054] 2.5) Filter the interconnection results that meet the regional contact distance constraint from all the combinations in step 2.4) to form the regional connectable combination set Ω.

[0055] Preferably, in step S022, the converter-based regional flexible interconnection two-layer planning model includes:

[0056] 1) Upper-level planning model:

[0057] minC=C I +C OM +C buy ;

[0058] Where: C I represents the annual investment cost of the flexible interconnection device; C OM Indicates the annual operation and maintenance cost of the interconnected device; C buy Indicates the cost of purchasing electricity from the upper power grid;

[0059] 1.1) Annual investment cost of interconnection devices

[0060]

[0061] Where: S i,vsc and is the converter capacity installed in region i and the unit capacity investment cost; N is the total number of distribution areas in the regional distribution network; Ω is the regional connectable combination set obtained after the connectability analysis of the distribution network; x h is a 0-1 variable, indicating whether the regions of the h-th combination in the set Ω are connected, where 1 indicates that the regions in the combination are connected, and 0 indicates that the regions in the combination are not connected; h represents the distance between two regions in the hth combination; represents the investment and installation cost of the unit length DC interconnection line; y vsc 、y line are the economic service life of the converter and DC line respectively; r is the discount rate;

[0062] 1.2) Annual operation and maintenance costs of interconnected devices

[0063]

[0064] Where: is the annual operation and maintenance cost per unit capacity of the converter;

[0065] 1.3) Cost of purchasing electricity from the upstream main grid

[0066] C buy =C Tbuy +C loss ;

[0067] Where: C Tbuy The cost of purchasing electricity from the main grid for all regions throughout the year; C loss The annual 10kV line loss cost of the power distribution system;

[0068] 2) Lower-level optimization operation model:

[0069]

[0070] Where: D s is the number of days included in the seasonal scenario s in a year; N is the total number of distribution areas included in the distribution network; N bos is the total number of 10kV nodes included in the distribution network; is the active power on the high-voltage side of the transformer in region i at time t under seasonal scenario s; c(t) is the electricity price from the upper grid at time t; P s,t (t) is the active power injected into node i by the system at time t under seasonal scenario s.

[0071] Preferably, the converter-based regional flexible interconnection two-layer planning model also includes the following constraints:

[0072] 1) Constraints of the upper model

[0073] 1.1) Regional converter access capacity constraints:

[0074]

[0075] Where: is the maximum installable capacity of the regional converter;

[0076] 2) Constraints of the lower-level model

[0077] 2.1) Power balance constraints of VSC commutation sub-areas and AC sub-areas

[0078] 2.2) Power balance constraints of the DC sub-area after the change

[0079]

[0080] Where: P s,i,pv (t) is the actual DPVG output of region i at time t in the s season scenario; P s,i,DC (t) is the DC load of region i at time t under the s season scenario; is the power flowing from region i to region j via the tie line at time t in the s season scenario; π(i) is the set of all regions connected to region i;

[0081] 2.3) Energy storage status and power constraints

[0082]

[0083]

[0084]

[0085] Where: and They are the charge and discharge state variables of the energy storage, which are 0-1 variables. A value of 1 indicates that the energy storage is in the charge / discharge state, and a value of 0 indicates that the charge / discharge state is stopped. is the maximum value of energy storage charging and discharging power in area i;

[0086]

[0087]

[0088]

[0089] Where: E i,Ess (t) is the energy storage capacity of region i at time t in the s season scenario; is the upper limit of energy storage capacity; η + and η - are the charging and discharging efficiency of energy storage respectively;

[0090] 2.4) Distributed PV Constraints

[0091]

[0092] Where: P i,pv (t) is the maximum output of distributed photovoltaic power generation in region i at time t under the s season scenario;

[0093] 2.5) Transferable load constraints

[0094]

[0095]

[0096] Where: is the upper limit of transferable DC load in region i at time t under the s season scenario;

[0097] 2.6) Constraints between flexible interconnected regions

[0098]

[0099]

[0100]

[0101] Where: K is the maximum transmission power allowed by the DC tie line; line is the line transmission loss coefficient;

[0102] 2.7) Power balance constraints in non-interconnected distribution areas

[0103]

[0104]

[0105]

[0106]

[0107]

[0108] 2.8) Distribution network flow constraints and node voltage constraints

[0109]

[0110]

[0111]

[0112]

[0113]

[0114] Where: U s,i (t), U s,j (t) and θ s,i (t) represents the voltage amplitude and phase angle difference of nodes i and j at time t in the s season scenario; Q s,i (t) represents the reactive power injected into node i by the system at time t in the s season scenario; δ(i) represents the set of nodes connected to node i; G i 、B i , G i 、B i are the mutual conductance, mutual susceptance, self-conductance and self-susceptance of the nodes respectively; U max and U min are the upper and lower limits of the voltage amplitude at node i, respectively.

[0115] Preferably, in step S3, the photovoltaic-agricultural and animal husbandry park flexible interconnection two-layer joint planning model includes:

[0116] 1) Upper-level planning model:

[0117] minF=F l +F om +F buy ;

[0118] Where: F l F is the annual investment and installation cost; om F is the annual operation and maintenance cost, including the operation and maintenance cost of distributed photovoltaic and VSC; buy Cost of electricity purchased by the distribution network from the upper power grid;

[0119] 1.1) Annualized investment and installation costs

[0120]

[0121] Where: S i,PV and is the distributed photovoltaic capacity installed in region i and the investment and installation cost per unit capacity; S i,VSC and The installed VSC capacity and unit capacity investment and installation cost of region i; ij is the distance between interconnected regions i and j; is the investment and installation cost per unit length of DC interconnection line. Since DC transmission has positive and negative poles, the line cost is multiplied by a factor of 2 when calculating the line cost. pv 、y VSC 、y line are the economic service life of distributed photovoltaic, VSC and DC routes respectively; r is the discount rate; N is the number of regions to be planned for the distribution network; B is the set of all regions of the distribution network; x ij is a 0-1 state variable, indicating the interconnection status of regions i and j, 1 indicates that the two regions are interconnected, and 0 indicates that the two regions are not interconnected;

[0122] 1.2) Annual operation and maintenance costs

[0123]

[0124] Where: are the annual operation and maintenance costs per unit capacity of distributed PV and VSC, respectively;

[0125] 1.3) Electricity purchase costs from the upper-level power grid

[0126] F buy =F Tbuy +F loss ;

[0127] Where: F Tbuy F is the cost of purchasing electricity from the power grid; loss10kV network loss cost for regional distribution network;

[0128] 2) Lower layer running model:

[0129]

[0130] Where: D s is the number of days included in the seasonal scenario s in a year; N is the total number of distribution areas included in the distribution network; N bos is the total number of 10kV nodes included in the distribution network; is the active power on the high-voltage side of the transformer in region i at time t under seasonal scenario s; P s,i (t) is the active power injected into node i by the system at time t under seasonal scenario s.

[0131] Preferably, the photovoltaic-agricultural and pastoral park flexible interconnection two-layer joint planning model includes the following constraints:

[0132] 1) Constraints of the upper model

[0133] 1.1) Distributed PV installation constraints

[0134]

[0135]

[0136] Where: dis(i,j) represents the distance between region i and region j; dis max Indicates the maximum distance allowed between interconnected areas;

[0137] 1.2) VSC Installation Capacity Constraints

[0138]

[0139]

[0140] Where: The maximum capacity of VSCs allowed to be installed in region i

[0141] Compared with the existing technology, the cross-temporal and spatial flexible interconnection planning method based on multiple agricultural and animal husbandry zero-carbon parks and photovoltaics in the present invention has the following beneficial effects:

[0142] The present invention establishes the operating power balance constraints of the converter-based interconnected system by analyzing the control strategies and applicable scope of typical regional flexible interconnected systems. On the one hand, by comparing the differences in topology, voltage level, regulation performance, construction cost, etc. of typical regional interconnection methods, it is possible to select a flexible interconnection method that is more applicable in the current context, laying the foundation for the subsequent operation control of the interconnected systems of photovoltaic and agricultural and pastoral parks; on the other hand, the present invention divides the interconnected system and establishes the operating power balance constraints of each subsystem, which can lay the foundation for the coordinated control of regional source, load, and storage resources, and is conducive to the complementarity of flexible resources in agricultural and pastoral parks and photovoltaic power generation in the entire county.

[0143] The present invention constructs a flexible interconnection system based on the energy needs and energy coordination and complementarity of different regions. By establishing regional interconnection indicators, a regional connectability analysis method is proposed, and then a regional flexible interconnection two-layer planning model is established. It can accurately match regions with interconnection needs, and by optimizing the interconnection scheme of the distribution area and the capacity of the corresponding interconnection device, it provides distributed photovoltaic cross-regional absorption and heavy load paths for regions with interconnection needs, alleviates the problems of excessive photovoltaic output and transformer overload, and is conducive to better considering the complementary characteristics of flexible resources in agricultural and pastoral parks and photovoltaics in the entire county, thereby providing a basis for subsequent flexible interconnection planning between agricultural and pastoral zero-carbon parks and photovoltaics across time and space.

[0144] The present invention establishes a two-layer joint planning model for the flexible interconnection of photovoltaic power generation and agricultural and animal husbandry parks in the whole county, targeting photovoltaic planning areas with great installation potential and agricultural and animal husbandry zero-carbon parks with rich biomass resources. It also optimizes the regional photovoltaic access capacity and the optimal flexible interconnection scheme, and realizes the photovoltaic configuration of the photovoltaic planning areas and the photovoltaic absorption and distribution network operation of the agricultural and animal husbandry zero-carbon parks. The present invention improves the overall acceptance level of distributed photovoltaics in the distribution network of the agricultural and animal husbandry zero-carbon park from the planning level, promotes the photovoltaic configuration and safe and economic operation of the regional distribution network under the background of the whole county photovoltaic, that is, it can realize the cross-temporal and spatial interaction between the agricultural and animal husbandry park and the photovoltaic area of the whole county, improve the absorption level of photovoltaics in the whole county, and also realize the joint economic operation of multiple regions, thereby ensuring the effectiveness of the cross-temporal and spatial flexible interconnection planning of multiple agricultural and animal husbandry zero-carbon parks and photovoltaics. BRIEF DESCRIPTION OF THE DRAWINGS

[0145] In order to make the purpose, technical solutions and advantages of the invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings, in which:

[0146] Figure 1 It is a logical block diagram of the cross-temporal and spatial interaction technology between multiple agricultural and animal husbandry zero-carbon parks and the entire county photovoltaic system;

[0147] Figure 2 This is the topological structure diagram of the flexible interconnection system;

[0148] Figure 3 It is a two-tier planning model for regional flexible interconnection. DETAILED DESCRIPTION

[0149] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. The components of the embodiments of the present invention generally described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the invention claimed for protection, but only represents selected embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0150] It should be noted that similar reference numerals and letters denote similar items in the following figures. Therefore, once an item is defined in one figure, it does not require further definition or explanation in subsequent figures. In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer" indicate positions or relationships based on the positions or relationships shown in the figures, or the positions or relationships in which the inventive product is typically placed when in use. These terms are intended solely to facilitate the description of the present invention and simplify the description. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation, and are therefore not to be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third," etc., are used solely to distinguish descriptions and are not to be construed as indicating or implying relative importance. Furthermore, terms such as "horizontal" and "vertical" do not imply that a component is absolutely horizontal or overhanging, but rather may be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but rather may be slightly tilted. In the description of the present invention, it should also be noted that, unless otherwise expressly specified or limited, the terms "disposed," "installed," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to mechanical connections or electrical connections; they may refer to direct connections or indirect connections through an intermediate medium; and they may refer to internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0151] The following is a further detailed description through specific implementation methods:

[0152] Example:

[0153] This embodiment discloses a cross-temporal and spatial flexible interconnection planning method based on multiple agricultural and animal husbandry zero-carbon parks and photovoltaics.

[0154] like Figure 1 As shown in the figure, the cross-temporal and spatial flexible interconnection planning method based on multiple agricultural and animal husbandry zero-carbon parks and photovoltaics includes:

[0155] S1: Compare and analyze the control strategies and applicable scopes of typical regional flexible interconnection systems, and establish converter-based interconnection system operation power balance constraints;

[0156] S2: Based on the operating power balance constraints of the converter-based interconnected system, a regional connectivity analysis is conducted on the inter-regional interconnection demand, and then a converter-based two-level planning model for regional flexible interconnection is constructed;

[0157] S3: Based on the converter-based regional flexible interconnection two-tier planning model, a two-tier joint planning model for PV-agricultural and animal husbandry park flexible interconnection is constructed with the goal of maximizing PV utilization, the economic benefits of the agricultural and animal husbandry zero-carbon park, and the operational efficiency of the distribution network.

[0158] S4: Solve the photovoltaic-agricultural and animal husbandry park flexible interconnection two-layer joint planning model to obtain the regional photovoltaic access capacity and the optimal flexible interconnection plan, and then realize the photovoltaic configuration of the photovoltaic planning area and the photovoltaic absorption and distribution network operation of the agricultural and animal husbandry zero-carbon park based on the photovoltaic access capacity and the optimal flexible interconnection plan.

[0159] In this example, the optimal flexible interconnection scheme and operating costs for agricultural and pastoral parks and county-wide photovoltaic zones are used as the objectives of the cross-temporal and spatial interaction technology between the two. A hybrid algorithm based on simulated annealing and a second-order cone algorithm is used to solve the photovoltaic-agricultural and pastoral park flexible interconnection two-layer joint planning model, resulting in the optimal flexible interconnection scheme and regional photovoltaic access capacity. After clarifying the planning scheme for the interconnected system, the flexible resources of the agricultural and pastoral parks can promote the absorption of photovoltaic power throughout the county across time and space. Furthermore, considering the complementary characteristics of agricultural and pastoral parks and county-wide photovoltaic zones at the distributed photovoltaic planning level can enhance the installation potential of distributed photovoltaic power.

[0160] The present invention establishes the operating power balance constraints of the converter-based interconnected system by analyzing the control strategies and applicable scope of typical regional flexible interconnected systems. On the one hand, by comparing the differences in topology, voltage level, regulation performance, construction cost, etc. of typical regional interconnection methods, it is possible to select a flexible interconnection method that is more applicable in the current context, laying the foundation for the subsequent operation control of the interconnected systems of photovoltaic and agricultural and pastoral parks; on the other hand, the present invention divides the interconnected system and establishes the operating power balance constraints of each subsystem, which can lay the foundation for the coordinated control of regional source, load, and storage resources, and is conducive to the complementarity of flexible resources in agricultural and pastoral parks and photovoltaic power generation in the entire county.

[0161] The present invention constructs a flexible interconnection system based on the energy needs and energy coordination and complementarity of different regions. By establishing regional interconnection indicators, a regional connectability analysis method is proposed, and then a regional flexible interconnection two-layer planning model is established. It can accurately match regions with interconnection needs, and by optimizing the interconnection scheme of the distribution area and the capacity of the corresponding interconnection device, it provides distributed photovoltaic cross-regional absorption and heavy load paths for regions with interconnection needs, alleviates the problems of excessive photovoltaic output and transformer overload, and is conducive to better considering the complementary characteristics of flexible resources in agricultural and pastoral parks and photovoltaics in the entire county, thereby providing a basis for subsequent flexible interconnection planning between agricultural and pastoral zero-carbon parks and photovoltaics across time and space.

[0162] The present invention establishes a two-layer joint planning model for the flexible interconnection of photovoltaic power generation and agricultural and animal husbandry parks in the whole county, targeting photovoltaic planning areas with great installation potential and agricultural and animal husbandry zero-carbon parks with rich biomass resources. It also optimizes the regional photovoltaic access capacity and the optimal flexible interconnection scheme, and realizes the photovoltaic configuration of the photovoltaic planning areas and the photovoltaic absorption and distribution network operation of the agricultural and animal husbandry zero-carbon parks. The present invention improves the overall acceptance level of distributed photovoltaics in the distribution network of the agricultural and animal husbandry zero-carbon park from the planning level, promotes the photovoltaic configuration and safe and economic operation of the regional distribution network under the background of the whole county photovoltaic, that is, it can realize the cross-temporal and spatial interaction between the agricultural and animal husbandry park and the photovoltaic area of the whole county, improve the absorption level of photovoltaics in the whole county, and also realize the joint economic operation of multiple regions, thereby ensuring the effectiveness of the cross-temporal and spatial flexible interconnection planning of multiple agricultural and animal husbandry zero-carbon parks and photovoltaics.

[0163] During implementation, with the advancement of county-wide photovoltaic policies, the number of distributed photovoltaic systems connected to low-voltage distribution areas has continued to increase. Coupled with the continued rise in DC loads, load imbalances within distribution areas have become increasingly prominent, and the demand for interconnection within distribution areas has become increasingly urgent. The converter-based flexible interconnection system retains traditional AC distribution transformers. The converter capacity configuration primarily considers the region's power transfer needs and the level of distributed photovoltaic access. Combined with its low unit construction cost, it is more suitable for retrofitting existing AC areas with relatively small distributed power generation connections but a certain degree of power exchange requirements.

[0164] This embodiment takes the flexible interconnection system based on the converter as the object, such as Figure 2 As shown, it adopts a DC bus segmented chain structure. The present invention first compares and analyzes the control strategies and applicable scopes of typical regional flexible interconnection systems, and establishes the operating power balance constraints of the interconnection system based on the converter. Based on the interconnection requirements between regions, a regional connectability analysis method is proposed, and then a regional flexible interconnection two-layer planning model is established based on the system power balance constraints. At the distributed photovoltaic planning level, based on regional flexible interconnection technology, a county-wide photovoltaic and agricultural and animal husbandry park flexible interconnection two-layer joint planning model is established to improve the acceptance capacity of distributed photovoltaic in the county.

[0165] Specifically, the operating power balance constraint of the converter-based interconnected system is established through the following steps:

[0166] S101: Compare the similarities and differences in the working principles, topologies, and control strategies of typical regional flexible interconnection systems, and analyze and determine the applicable scenarios of regional flexible interconnection systems;

[0167] In this embodiment, a comparison of typical flexible interconnection approaches revealed that, overall, a PET-based regional flexible interconnection system offers superior operational flexibility, but also carries relatively higher control complexity and construction costs. For regional distribution networks, PET-based flexible interconnection systems require replacing traditional transformers. Therefore, their capacity configuration must consider the overall level of AC and DC sources and loads within the region, resulting in a large capacity requirement. Furthermore, their unit capacity construction cost is relatively high, making them more suitable for new distribution areas with large distributed power generation connections and high requirements for interactive flexibility. A converter-based flexible interconnection system retains traditional AC distribution transformers. Converter capacity configuration primarily considers the regional power transfer requirements and the level of distributed photovoltaic access. Furthermore, their unit construction cost is low, making them more suitable for retrofitting existing AC areas with relatively small distributed power generation connections but a certain degree of power interactive demand. Therefore, this paper selects the highly adaptable VSC-based DC bus segmented chain interconnection system as its research object, dividing the interconnection area into VSC conversion areas, AC areas, and DC areas based on their operational functions and resource types.

[0168] S102: Analyze the flexible interconnection area of the converter based on the applicable scenarios of the regional flexible interconnection system, and then divide the flexible interconnection area into VSC commutation sub-area, AC sub-area and DC sub-area according to resource type, and establish power balance constraint equations for each sub-area.

[0169] Specifically, the power balance constraint equations for each sub-area are as follows:

[0170] 1) Power balance constraint equation of VSC commutation sub-area

[0171]

[0172] Where: is the active power flowing into the VSC port from the AC region of region i at time t; is the active power flowing into the AC area from the VSC port of area i at time t; is the active power flowing into the VSC port from the DC region of region i at time t; is the active power flowing into the DC region from the VSC port of region i at time t; K vsc The loss factor for power exchange for VSC;

[0173]

[0174] Where: is the reactive power flowing into the VSC AC port in region i at time t; S i,vsc VSC capacity configured for region i;

[0175] 2) Power balance constraint equation of AC sub-area

[0176]

[0177]

[0178]

[0179]

[0180]

[0181] Where: and are the active power and reactive power on the low-voltage side of the transformer in region i at time t, respectively; and are the active power and reactive power on the high-voltage side of the transformer in region i at time t, respectively; are the active power and reactive power of AC load in area i at time ι respectively; P T0 、P TK , I T0 and U TK They represent the no-load loss, rated load loss, no-load current percentage and short-circuit voltage percentage of the transformer in area i respectively; β i (t), S i,T are the transformer load factor and transformer capacity in region i respectively;

[0182] 3) Power balance constraint equation of DC sub-region

[0183]

[0184] Where: P i,pv (t) represents the actual output of DPVG (distributed photovoltaic) in region i at time t; is the power flowing on the line between regions i and j at time i, with the positive direction being the power flowing from region i to region j; π(i) is the set of all regions connected to region i; P i,pc (t) represents the DC load of area i at time t; and represents the charging and discharging power of the energy storage in region i at time t; It represents the flexible DC load transfer amount in region i at time t.

[0185] The power balance constraint equations of each sub-area also include:

[0186] 1) Determine the operation mode of the interconnected system. The self-supply mode meets the following requirements:

[0187]

[0188] Where: represents the power flowing on the tie line between regions i and j at time t, with the positive direction being the power flowing from region i to region j; π(i) represents the set of all regions connected to region i;

[0189] 2) The photovoltaic cross-regional consumption model meets the following requirements:

[0190]

[0191] 3) The load transfer mode meets the following requirements:

[0192]

[0193] Based on the regional interconnection needs, this paper proposes a regional connectability analysis method for the regional distribution network. On this basis, a converter-based distribution regional flexible interconnection planning model is established. By optimizing the regional interconnection scheme and interconnection operation method, the purpose of improving the system photovoltaic absorption rate and safe and economical operation is achieved.

[0194] During the specific implementation process, a two-layer planning model for regional flexible interconnection based on converters is established through the following steps:

[0195] S201: Based on the interconnection demand index, the interconnection demand of different regions is judged and the regions are classified, and then the interconnection distance constraint is introduced to determine the possible interconnection combinations between different regions;

[0196] In this embodiment, interconnection demand and connectability are assessed for all regions within the scope, and then the set of connectable regions is determined. When assessing regional demand, the degree of compatibility between the region's daily load characteristics and PV output characteristics in different seasons must be comprehensively considered. Therefore, a regional seasonal net load curve is used to characterize its operating characteristics. Furthermore, two interconnection demand indicators, the regional maximum variable maximum net load ratio and minimum net load, are used to assess regional interconnection demand and assist in regional classification.

[0197] In step S2021, the steps for determining the connectable combinations between different regions are as follows:

[0198] 1) Calculate the maximum net load index and the minimum net load index;

[0199] The calculation formula is as follows:

[0200]

[0201]

[0202] Where: T i load and P i pure Respectively represent the maximum net load index and the minimum net load index; and are the active and reactive power of the AC load at time t in region i under the s season scenario; is the maximum output of distributed photovoltaic power generation in region i at time t in the s season scenario; S i,T is the transformer capacity of area i;

[0203] 2) Based on the maximum net load factor and minimum net load factors, the possible interconnection combinations between different areas are analyzed as follows:

[0204] 2.1) Calculate the source and load characteristic curves, regional transformer parameters, and distances between different regions under different seasonal scenarios in each region;

[0205] 2.2) Calculate the maximum net load factor index T for each region's interconnection demand i load and minimum net load index P i pure ;

[0206] 2.3) Classify the regions: If T i load >0.8, classified into set φ f1 , otherwise it is classified into the set φ t1 If P i pure <0, included in the set φ f2 , otherwise it is classified into the set φ t2 ;

[0207] 2.4) φ f1 With φ t1 The regions of φ are combined and φ f2 With φ t2 to combine the areas;

[0208] 2.5) Filter the interconnection results that meet the regional contact distance constraint from all the combinations in step 2.4) to form the regional connectable combination set Ω.

[0209] S202: Based on the flexible interconnection technology of converters, a two-layer planning model for regional flexible interconnection based on converters is established in combination with the interconnectable combinations between different regions to achieve optimal planning of interconnection schemes and interconnection transposition capacity.

[0210] This paper analyzes the regional flexible interconnection planning problem from two perspectives: operation and planning. Taking into account the significant differences in the optimization time scales and order of magnitude of decision variables at the two levels, a hierarchical approach is used to establish a regional flexible interconnection planning model. The upper-level model is used to achieve optimal flexible interconnection solutions and optimize the planning of interconnection device capacity, with the objective function being to minimize the annual comprehensive cost of the distribution network. The lower-level model achieves optimal operation of the flexible interconnected distribution system, with the objective function being to minimize the total electricity purchase cost from the upper main grid. Specifically, the converter-based two-level planning model for regional flexible interconnection includes:

[0211] 1) Upper-level planning model:

[0212] min C=C I +C OM +C buy ''

[0213] Where: C I represents the annual investment cost of the flexible interconnection device; C OM Indicates the annual operation and maintenance cost of the interconnected device; C buy Indicates the cost of purchasing electricity from the upper power grid;

[0214] 1.1) Annual investment cost of interconnection devices

[0215] The investment cost of the interconnection device consists of two parts: the investment cost of the converter and the investment cost of the inter-regional DC tie line. The mathematical expression is:

[0216]

[0217] Where: S i,vsc and is the converter capacity installed in region i and the unit capacity investment cost; N is the total number of distribution areas in the regional distribution network; Ω is the regional connectable combination set obtained after the connectability analysis of the distribution network; x h is a 0-1 variable, indicating whether the regions of the h-th combination in the set Ω are connected, where 1 indicates that the regions in the combination are connected, and 0 indicates that the regions in the combination are not connected; h represents the distance between two regions in the hth combination; represents the investment and installation cost of the unit length DC interconnection line; y vsc 、y line are the economic service life of the converter and DC line respectively; r is the discount rate;

[0218] 1.2) Annual operation and maintenance costs of interconnected devices

[0219] The operating voltage level of the DC interconnection line in the interconnection device is low and the connection distance is short, so its maintenance cost can be basically ignored. Therefore, the annual operation and maintenance cost of the interconnection device is mainly the operation and maintenance cost of the regional converter.

[0220]

[0221] Where: is the annual operation and maintenance cost per unit capacity of the converter.

[0222] 1.3) Cost of purchasing electricity from the upstream main grid

[0223] The cost of electricity purchased from the upper main grid by the interconnected distribution system mainly includes the cost of electricity purchased from the main grid in the region and the cost of 10kV line loss in the distribution network:

[0224] C buy =C Tbuy +C loss ;

[0225] Where: C Tbuy The cost of purchasing electricity from the main grid for all regions throughout the year; C loss The annual 10kV line loss cost of the power distribution system;

[0226] 2) Lower-level optimization operation model:

[0227]

[0228] Where: D s is the number of days included in the seasonal scenario s in a year; N is the total number of distribution areas included in the distribution network; N bos is the total number of 10kV nodes included in the distribution network; is the active power on the high-voltage side of the transformer in region i at time t under seasonal scenario s; c(t) is the electricity price from the upper grid at time t; P s,t (t) is the active power injected into node i by the system at time t under seasonal scenario s.

[0229] Specifically, the converter-based regional flexible interconnection two-layer planning model also includes the following constraints:

[0230] 1) Constraints of the upper model

[0231] 1.1) Regional converter access capacity constraints:

[0232]

[0233] Where: is the maximum installable capacity of the regional converter;

[0234] 2) Constraints of the lower-level model

[0235] 2.1) Power balance constraints between VSC commutation sub-areas and AC sub-areas

[0236] 2.2) Power balance constraints of the DC sub-area after the change

[0237]

[0238] Where: P s,i,pv (t) is the actual DPVG output of region i at time t in the s season scenario; P s,i,DC (t) is the DC load of region i at time t under the s season scenario; is the power flowing from region i to region j via the tie line at time t in the s season scenario; π(i) is the set of all regions connected to region i;

[0239] 2.3) Energy storage status and power constraints

[0240]

[0241]

[0242]

[0243] Where: and They are the charge and discharge state variables of the energy storage, which are 0-1 variables. A value of 1 indicates that the energy storage is in the charge / discharge state, and a value of 0 indicates that the charge / discharge state is stopped. is the maximum value of energy storage charging and discharging power in area i;

[0244]

[0245]

[0246]

[0247] Where: E i,Ess (t) is the energy storage capacity of region i at time t in the s season scenario; is the upper limit of energy storage capacity; η + and η - are the charging and discharging efficiency of energy storage respectively;

[0248] 2.4) Distributed PV Constraints

[0249]

[0250] Where: P i,pv (t) is the maximum output of distributed photovoltaic power generation in region i at time t under the s season scenario;

[0251] 2.5) Transferable load constraints

[0252]

[0253]

[0254] Where: is the upper limit of transferable DC load in region i at time t under the s season scenario;

[0255] 2.6) Constraints between flexible interconnected regions

[0256]

[0257]

[0258]

[0259] Where: K is the maximum transmission power allowed by the DC tie line; line is the line transmission loss coefficient;

[0260] 2.7) Power balance constraints in non-interconnected distribution areas

[0261]

[0262]

[0263]

[0264]

[0265]

[0266] 2.8) Distribution network flow constraints and node voltage constraints

[0267]

[0268]

[0269]

[0270]

[0271]

[0272] Where: U s,i (t), U s,j (t) and θ s,i (t) represents the voltage amplitude and phase angle difference of nodes i and j at time t in the s season scenario; Q s,i(t) represents the reactive power injected into node i by the system at time t in the s season scenario; δ(i) represents the set of nodes connected to node i; G i 、B i , G i 、B i are the mutual conductance, mutual susceptance, self-conductance and self-susceptance of the nodes respectively; U max and U min are the upper and lower limits of the voltage amplitude at node i, respectively.

[0273] During implementation, for distribution networks not yet connected to distributed photovoltaics, the power transfer capabilities of flexible interconnection can also overcome the limitations of regional load levels on photovoltaic installation capacity under traditional structures, thereby increasing the overall photovoltaic installation capacity of the distribution network at the planning level. Flexible interconnection systems can improve the absorption capacity of distributed photovoltaics at both the operational and planning levels. However, because the optimization problems of planning and operation are relatively independent yet mutually influential at different time scales, the decision variables and the order of magnitude of the variables differ significantly.

[0274] To simplify the planning and solving process and improve model solution efficiency, this paper adopts a layered approach to establish a two-tiered joint planning model for county-wide photovoltaic and agricultural park flexible interconnection. The upper-tier model primarily addresses planning issues, optimizing decisions regarding regional distributed photovoltaic (PV) and VSC (VSC) capacity, as well as the optimal regional flexible interconnection solution. The lower-tier model primarily addresses operational issues, optimizing the operation of the regional distribution network encompassing distributed photovoltaic (PV) and flexible interconnection areas.

[0275] Combine Figure 3 As shown in Figure 2, the photovoltaic-agricultural and animal husbandry park flexible interconnection two-layer joint planning model includes:

[0276] 1) Upper-level planning model:

[0277] minF=F l +F om +F buy ;

[0278] Where: F l F is the annual investment and installation cost; om F is the annual operation and maintenance cost, including the operation and maintenance cost of distributed photovoltaic and VSC; buy Cost of electricity purchased by the distribution network from the upper power grid;

[0279] 1.1) Annualized investment and installation costs

[0280]

[0281] Where: S i,PV and is the distributed photovoltaic capacity installed in region i and the investment and installation cost per unit capacity; Si,VSC and The installed VSC capacity and unit capacity investment and installation cost of region i; ij is the distance between interconnected regions i and j; is the investment and installation cost per unit length of DC interconnection line. Since DC transmission has positive and negative poles, the line cost is multiplied by a factor of 2 when calculating the line cost. pv 、y VSC 、y line are the economic service life of distributed photovoltaic, VSC and DC routes respectively; r is the discount rate; N is the number of regions to be planned for the distribution network; B is the set of all regions of the distribution network; x ij is a 0-1 state variable, indicating the interconnection status of regions i and j, 1 indicates that the two regions are interconnected, and 0 indicates that the two regions are not interconnected;

[0282] 1.2) Annual operation and maintenance costs

[0283]

[0284] Where: are the annual operation and maintenance costs per unit capacity of distributed PV and VSC, respectively;

[0285] 1.3) Electricity purchase costs from the upper-level power grid

[0286] F buy =F Tbuy +F loss ;

[0287] Where: F Tbw F is the cost of purchasing electricity from the power grid; ioss 10kV network loss cost for regional distribution network;

[0288] 2) Lower layer running model:

[0289]

[0290] Where: D s is the number of days included in the seasonal scenario s in a year; N is the total number of distribution areas included in the distribution network; N bos is the total number of 10kV nodes included in the distribution network; is the active power on the high-voltage side of the transformer in region i at time t under seasonal scenario s; P s,i (t) is the active power injected into node i by the system at time t under seasonal scenario s.

[0291] Specifically, the photovoltaic-agricultural and pastoral park flexible interconnection two-layer joint planning model includes the following constraints:

[0292] 1) Constraints of the upper model

[0293] 1.1) Distributed PV installation constraints

[0294]

[0295]

[0296] Where: dis(i,j) represents the distance between region i and region j; dis max Indicates the maximum distance allowed between interconnected areas;

[0297] 1.2) VSC Installation Capacity Constraints

[0298]

[0299]

[0300] Where: The maximum capacity of VSCs allowed to be installed in area i;

[0301] 2) The constraints of the lower-level model are the same as those of the lower-level model of the converter-based regional flexible interconnection two-level planning model.

[0302] Aiming at the trend of whole-county photovoltaics, this invention considers the complementary characteristics of flexible resources in agricultural and pastoral parks and whole-county photovoltaics, and uses flexible interconnection technology to establish an agricultural and pastoral park-whole-county photovoltaic joint planning model from the planning and operation levels, thereby improving the power supply flexibility and reliability of the interconnected areas in multiple dimensions, effectively solving the problem of cross-temporal and spatial interaction between agricultural and pastoral parks and whole-county photovoltaics, and improving the level of distributed photovoltaic absorption.

[0303] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the technical solutions. Those skilled in the art should understand that modifications or equivalent replacements of the technical solutions of the present invention that do not depart from the purpose and scope of the technical solutions of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A cross-temporal and spatial flexible interconnection planning method based on multiple agricultural and animal husbandry zero-carbon parks and photovoltaics, characterized by: include: S1: Compare and analyze the control strategies and applicable scopes of typical regional flexible interconnection systems, and establish converter-based interconnection system operation power balance constraints; S2: Based on the operating power balance constraints of the converter-based interconnected system, a regional connectivity analysis is conducted on the inter-regional interconnection demand, and then a converter-based two-level planning model for regional flexible interconnection is constructed; In step S2, a converter-based regional flexible interconnection two-layer planning model is established through the following steps: S201: Based on the interconnection demand index, the interconnection demand of different regions is judged and the regions are classified, and then the interconnection distance constraint is introduced to determine the possible interconnection combinations between different regions; S202: Based on converter-based flexible interconnection technology and combining different regional interconnection combinations, a converter-based regional flexible interconnection two-layer planning model is established to achieve optimal planning of interconnection solutions and interconnection translocation capacity; The steps to determine the possible combinations between different regions are as follows: 1) Calculate the maximum net load index and the minimum net load index; The calculation formula is as follows: Where: T i load and P i pure Respectively represent the maximum net load index and the minimum net load index; and are the active and reactive power of the AC load at time t in region i under the s season scenario; is the maximum output of distributed photovoltaic power generation in region i at time t in the s season scenario; S i,T is the transformer capacity of area i; 2) Based on the maximum net load factor and minimum net load factors, the possible interconnection combinations between different areas are analyzed as follows: 2.1) Calculate the source and load characteristic curves, regional transformer parameters, and distances between different regions under different seasonal scenarios in each region; 2.2) Calculate the maximum net load factor index T for each region's interconnection demand i load and minimum net load index P i pure ; 2.3) Classify the regions: If T i load >0.8, classified into set φ f1 , otherwise it is classified into the set φ t1 If P i pure <0, included in the set φ f2 , otherwise it is classified into the set φ t2 ; 2.4) φ f1 With φ t1 The regions of φ are combined and φ f2 With φ t2 to combine the areas; 2.5) Filtering interconnection results that satisfy the regional contact distance constraint from all combinations in step 2.4) to form a regional connectable combination set Ω; The two-tier planning model for regional flexible interconnection based on converters includes: 1) Upper-level planning model: minC=C I +C OM +C buy ; Where: C I represents the annual investment cost of the flexible interconnection device; C OM Indicates the annual operation and maintenance cost of the interconnected device; C buy Indicates the cost of purchasing electricity from the upper power grid; 1.1) Annual investment cost of interconnection devices Where: S i,vsc and is the converter capacity installed in region i and the unit capacity investment cost; N is the total number of distribution areas in the regional distribution network; Ω is the regional connectable combination set obtained after the connectability analysis of the distribution network; x h is a 0-1 variable, indicating whether the regions of the h-th combination in the set Ω are connected, where 1 indicates that the regions in the combination are connected, and 0 indicates that the regions in the combination are not connected; h represents the distance between two regions in the hth combination; represents the investment and installation cost of the unit length DC interconnection line; y vsc 、y line are the economic service life of the converter and DC line respectively; r is the discount rate; 1.2) Annual operation and maintenance costs of interconnected devices Where: is the annual operation and maintenance cost per unit capacity of the converter; 1.3) Cost of purchasing electricity from the upstream main grid C buy =C Tbuy +C loss ; Where: C Tbuy The cost of purchasing electricity from the main grid for all regions throughout the year; C loss The annual 10kV line loss cost of the power distribution system; 2) Lower-level optimization operation model: Where: D s is the number of days included in the seasonal scenario s in a year; N is the total number of distribution areas included in the distribution network; N bos is the total number of 10kV nodes included in the distribution network; is the active power on the high-voltage side of the transformer in region i at time t under seasonal scenario s; c(t) is the electricity price purchased from the upper power grid at time t; P s,t (t) is the active power injected into node i by the system at time t under seasonal scenario s; S3: Based on the converter-based regional flexible interconnection two-tier planning model, a two-tier joint planning model for PV-agricultural and animal husbandry park flexible interconnection is constructed with the goal of maximizing PV utilization, the economic benefits of the agricultural and animal husbandry zero-carbon park, and the operational efficiency of the distribution network. In step S3, the photovoltaic-agricultural and animal husbandry park flexible interconnection two-layer joint planning model includes: 1) Upper-level planning model: min F=F l +F om +F buy ; Where: F l F is the annual investment and installation cost; om F is the annual operation and maintenance cost, including the operation and maintenance cost of distributed photovoltaic and VSC; buy Cost of electricity purchased by the distribution network from the upper power grid; 1.1) Annual investment and installation costs Where: S i,PV and is the distributed photovoltaic capacity installed in region i and the investment and installation cost per unit capacity; S i,VSC and The installed VSC capacity and unit capacity investment and installation cost of region i; ij is the distance between interconnected regions i and j; is the investment and installation cost per unit length of DC interconnection line. Since DC transmission has positive and negative poles, the line cost is multiplied by a factor of 2 when calculating the line cost. pv 、y VSC 、y line are the economic service life of distributed photovoltaic, VSC and DC routes respectively; r is the discount rate; N is the number of regions to be planned for the distribution network; B is the set of all regions of the distribution network; x ij is a 0-1 state variable, indicating the interconnection status of regions i and j, 1 indicates that the two regions are interconnected, and 0 indicates that the two regions are not interconnected; 1.2) Annual operation and maintenance costs Where: are the annual operation and maintenance costs per unit capacity of distributed PV and VSC respectively; 1.3) Electricity purchase costs from the upper-level power grid F buy =F Tbuy +F loss ; Where: F Tbuy F is the cost of purchasing electricity from the power grid; loss 10kV network loss cost for regional distribution network; 2) Lower layer running model: Where: D s is the number of days included in the seasonal scenario s in a year; N is the total number of distribution areas included in the distribution network; N bos is the total number of 10kV nodes included in the distribution network; is the active power on the high-voltage side of the transformer in region i at time t under seasonal scenario s; P s,i (t) is the active power injected into node i by the system at time t under seasonal scenario s; S4: Solve the photovoltaic-agricultural and animal husbandry park flexible interconnection two-layer joint planning model to obtain the regional photovoltaic access capacity and the optimal flexible interconnection plan, and then realize the photovoltaic configuration of the photovoltaic planning area and the photovoltaic absorption and distribution network operation of the agricultural and animal husbandry zero-carbon park based on the photovoltaic access capacity and the optimal flexible interconnection plan.

2. The cross-temporal and spatial flexible interconnection planning method based on multiple agricultural and animal husbandry zero-carbon parks and photovoltaics according to claim 1 is characterized by: In step S1, the converter-based interconnected system operation power balance constraint is established through the following steps: S101: Compare the similarities and differences in the working principles, topologies, and control strategies of typical regional flexible interconnection systems, and analyze and determine the applicable scenarios of regional flexible interconnection systems; S102: Analyze the flexible interconnection area of the converter based on the applicable scenarios of the regional flexible interconnection system, and then divide the flexible interconnection area into VSC commutation sub-area, AC sub-area and DC sub-area according to resource type, and establish power balance constraint equations for each sub-area.

3. The cross-temporal and spatial flexible interconnection planning method based on multiple agricultural and animal husbandry zero-carbon parks and photovoltaics according to claim 2 is characterized by: In step S102, the power balance constraint equation of each sub-area is as follows: 1) Power balance constraint equation of VSC commutation sub-area Where: is the active power flowing into the VSC port from the AC region of region i at time t; is the active power flowing into the AC area from the VSC port of area i at time t; is the active power flowing into the VSC port from the DC region of region i at time t; is the active power flowing into the DC region from the VSC port of region i at time t; K vsc The loss factor for power exchange for VSC; Where: is the reactive power flowing into the VSC AC port in region i at time t; S i,vsc VSC capacity configured for region i; 2) Power balance constraint equation of AC sub-area Where: and are the active power and reactive power on the low-voltage side of the transformer in region i at time t, respectively; and are the active power and reactive power on the high-voltage side of the transformer in region i at time t, respectively; are the active power and reactive power of AC load in area i at time ι respectively; P T0 、P TK , I T0 and U TK They represent the no-load loss, rated load loss, no-load current percentage and short-circuit voltage percentage of the transformer in area i respectively; β i (t), S i,T are the transformer load factor and transformer capacity in region i respectively; 3) Power balance constraint equation of DC sub-region Where: P i,pv (t) represents the actual output of DPVG in region i at time t; is the power flowing on the line between regions i and j at time i, with the positive direction being the power flowing from region i to region j; π(i) is the set of all regions connected to region i; P i,DC (t) represents the DC load of area i at time t; and represents the charging and discharging power of the energy storage in region i at time t; It represents the flexible DC load transfer amount in region i at time t.

4. The cross-temporal and spatial flexible interconnection planning method based on multiple agricultural and animal husbandry zero-carbon parks and photovoltaics according to claim 3 is characterized by: The power balance constraint equations for each sub-area also include: 1) The self-supply model meets the following requirements: Where: represents the power flowing on the tie line between regions i and j at time t, with the positive direction being the power flowing from region i to region j; π(i) represents the set of all regions connected to region i; 2) The photovoltaic cross-regional consumption model meets the following requirements: 3) The load transfer mode meets the following requirements:

5. The cross-temporal and spatial flexible interconnection planning method based on multiple agricultural and animal husbandry zero-carbon parks and photovoltaics according to claim 1 is characterized by: The converter-based regional flexible interconnection two-tier planning model also includes the following constraints: 1) Constraints of the upper model 1.1) Regional converter access capacity constraints: Where: is the maximum installable capacity of the regional converter; 2) Constraints of the lower-level model 2.1) Power balance constraints between VSC commutation sub-areas and AC sub-areas 2.2) Power balance constraints of the DC sub-area after the change Where: P s,i,pv (t) is the actual DPVG output of region i at time t in the s season scenario; P s,i,DC 9t) is the DC load of region i at time t under the s season scenario; is the power flowing from region i to region j via the tie line at time t in the s season scenario; π(i) is the set of all regions connected to region i; 2.3) Energy storage status and power constraints Where: and They are the charge and discharge state variables of the energy storage, which are 0-1 variables. A value of 1 indicates that the energy storage is in the charge / discharge state, and a value of 0 indicates that the charge / discharge state is stopped. is the maximum value of energy storage charging and discharging power in area i; Where: E i,Ess (t) is the energy storage capacity of region i at time t in the s season scenario; The upper limit of energy storage capacity; η + and η - are the charging and discharging efficiency of energy storage respectively; 2.4) Distributed PV Constraints Where: is the maximum output of distributed photovoltaic power generation in region i at time t under the scenario of season s; 2.5) Transferable load constraints Where: is the upper limit of transferable DC load in region i at time t under the s season scenario; 2.6) Constraints between flexible interconnected regions Where: K is the maximum transmission power allowed by the DC tie line; line is the line transmission loss coefficient; 2.7) Power balance constraints in non-interconnected distribution areas 2.8) Distribution network flow constraints and node voltage constraints Where: U s,i (t), U s,j (t) and θ s,i (t) represents the voltage amplitude and phase angle difference of nodes i and j at time t in the s season scenario; Q s,i (t) represents the reactive power injected into node i by the system at time t in the s-season scenario; δ(i) represents the set of nodes connected to node i; G i 、B i , G i 、B i are the mutual conductance, mutual susceptance, self-conductance and self-susceptance of the nodes respectively; and are the upper and lower limits of the voltage amplitude at node i, respectively.

6. The cross-temporal and spatial flexible interconnection planning method based on multiple agricultural and animal husbandry zero-carbon parks and photovoltaics according to claim 1 is characterized by: The two-layer joint planning model for the flexible interconnection of photovoltaic and agricultural and pastoral parks includes the following constraints: 1) Constraints of the upper model 1.1) Distributed PV installation constraints Where: dis(i,j) represents the distance between region i and region j; dis max Indicates the maximum distance allowed between interconnected areas; 1.2) VSC Installation Capacity Constraints Where: The maximum capacity of VSCs allowed to be installed in area i.

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