Photovoltaic power station layered reactive power coordination optimization method, device and equipment considering SVG access and storage medium

Abstract

The invention provides a photovoltaic power station layered reactive power coordination optimization method and device considering SVG access, equipment and a storage medium, and relates to the technical field of reactive power compensation. According to the method, a three-layer progressive control system is constructed based on a photovoltaic power station topological structure and reactive power transmission characteristics: reactive power centralized compensation is completed preferentially through a main transformer low-voltage side SVG, so that the loss of a current collection line is reduced to the maximum extent; and when the SVG compensation capacity reaches the upper limit, the residual reactive power is reasonably distributed to each photovoltaic power generation unit. Simulation verification results show that the strategy can strictly control the voltage deviation of the grid-connected point within a stable interval, and the voltage stability and economical efficiency of grid-connected operation of the photovoltaic power station are remarkably enhanced.

Description

Technical Field

[0001] This application relates to the field of reactive power compensation technology, and in particular to a hierarchical reactive power coordination optimization method, apparatus, equipment and storage medium for photovoltaic power plants considering SVG access. Background Technology

[0002] As a core carrier of clean energy supply, photovoltaic (PV) power plants, with their large-scale grid-connected operation, pose higher standards for the safety and stability of the power system. PV power plants employ a centralized grid-connected mode with parallel inverters, connecting to the high-voltage AC transmission system after processing by a step-up transformer. However, a significant contradiction exists in actual operation: when the power plant increases its active power output, reducing the reactive power output of the inverters cannot offset the reactive power losses of the step-up transformers, forcing the power plant to absorb a large amount of reactive power from the grid, thus weakening the inverters' voltage regulation function. Furthermore, PV power plants are often located in remote areas, and the superposition of long-distance transmission lines and dispersed loads further exacerbates voltage fluctuations in the local power grid, seriously threatening the stable operation of the power system. Therefore, optimizing voltage control through scientific reactive power compensation technology has become a key technological breakthrough for the efficient grid connection of PV power plants.

[0003] In existing technologies, the application of reactive power compensation technology in power systems has been widely discussed. The paper "CRiedmann, U Schichler, W Häusler and W Neuhold. Gas Losses in Transformers—Influences and Consideration. IEEE Access 2023;11:58654-58663." focuses on the coordinated operation of inverters and reactive power compensation devices, and designs a three-layer reactive power control framework for photovoltaic power plants, realizing the coordination of reactive power distribution among reactive power compensation devices, various power generation units, and inverters. The paper "R Emadifar, N T. Kalantari, V Behjat and RNajjar. Monitoring and Condition Assessment of Insulation Paper of Distribution Transformers With Novel Oil Spectroscopy Method. IEEE Transactions on Dielectrics and Electrical Insulation 2022; 29(5): 1904-1912" proposes a voltage coordination control strategy based on inverter reactive power regulation by constructing a mathematical model of the inverter. This strategy deeply explores the reactive power regulation potential of the inverter and can provide reliable support for the grid voltage under both steady-state and transient conditions, thus optimizing the regulation performance of photovoltaic power plants. The paper "Zhou Lin, Ren Wei. Reactive power and voltage control of grid-connected photovoltaic power plants. Journal of Electrical Engineering, 2015, 30(20): 168-175" analyzes the influencing factors of grid-connected voltage and proposes a reactive power control scheme that takes into account the voltage distribution characteristics within the station. With the core objective of achieving voltage balance within the station, the reactive power optimization problem is transformed into a nonlinear programming model with constraints, enabling efficient and rapid solution. However, the existing technology fails to establish a deep collaborative control mechanism between SVG and photovoltaic power generation units, and does not fully consider the coupling effect of collector line losses and inverter capacity limitations, leaving room for further optimization. Summary of the Invention

[0004] This application provides a hierarchical reactive power coordination optimization method, device, equipment, and storage medium for photovoltaic power plants considering SVG access. By constructing a deep collaborative control mechanism between SVG and photovoltaic power generation units, it fully considers the coupling effect of collector line losses and inverter capacity limitations, and constructs a three-layer progressive control system to solve the problem that the inverter's voltage regulation capability is limited after the active power output of the photovoltaic power plant is increased, and reactive power needs to be drawn from the grid.

[0005] Firstly, this application provides a hierarchical reactive power coordination optimization method for photovoltaic power plants considering SVG access, including: Based on the assumption that the impedance of each line in a photovoltaic power station is consistent and the actual output current of a single photovoltaic power generation unit, an equivalent relationship between power loss and no power loss is established. Based on the equivalent relationship between power loss and no power loss, calculate the equivalent impedance of the collector line and the equivalent impedance of the transformer. Calculate the total equivalent impedance of the photovoltaic power station based on the equivalent impedance of the collector line and the transformer. Based on the total equivalent impedance of the photovoltaic power station, a reactive power balance relationship is established according to the active power and reactive power transmitted from the photovoltaic power station to the grid. Based on the aforementioned reactive power balance relationship and the preset grid voltage reference value, the grid connection point voltage of the photovoltaic power station is calculated. U pv and based on U pv A constant steady-state control objective is to calculate the reactive power required to maintain a constant voltage. Based on the reactive power required to maintain constant voltage, the total equivalent impedance of the photovoltaic power station, and the reactive power balance relationship, the constraints that the reactive power supply of the photovoltaic power station must meet are determined. Based on the constraints that the reactive power supply of the photovoltaic power station must meet, a three-layer progressive control system is adopted to allocate reactive power. This three-layer progressive control system includes a first-layer control, a second-layer control, and a third-layer control connected sequentially. The first-layer control includes: prioritizing centralized reactive power compensation through the low-voltage side SVG of the main transformer; dynamically adjusting the SVG compensation capacity based on the goal of minimizing collector line losses to maximize the reduction of collector line losses. The second-layer control includes: when the SVG compensation capacity in the first-layer control reaches its upper limit, based on the constraints, determining sensitivity-related parameters by analyzing the impact of each photovoltaic power generation unit on the grid connection point voltage, calculating weighting coefficients, and allocating the remaining reactive power to each photovoltaic power generation unit. The third-layer control includes: based on the reactive power allocated by the second-layer control, and under the condition of meeting the set inverter capacity constraints, according to the obtained data of each power generation unit... t The rated capacity and active power output of each inverter are used to distribute the reactive power allocated by the second-level control to each inverter.

[0006] In one possible design, the equivalent relationship between power loss and no power loss is expressed as: (1) In the formula, I pv This refers to the actual output current of a single photovoltaic power generation unit. Z The impedance of a single line; nThe number of circuits in the collector line; m This refers to the number of photovoltaic power generation units connected to each collector line; Z T The equivalent impedance of the main transformer; The equivalent impedance of the collector line; Z t The equivalent impedance of the step-up transformer in a photovoltaic power station. This is the equivalent impedance of the transformer.

[0007] In one possible design, based on the equivalent relationship between power loss and no power loss, the equivalent impedance of the collector line and the equivalent impedance of the transformer are calculated using the following formula: (2) (3) In the formula, Z The impedance of a single line; n The number of circuits in the collector line; m This refers to the number of photovoltaic power generation units connected to each collector line; Z T The equivalent impedance of the main transformer; The equivalent impedance of the collector line; Z t The equivalent impedance of the step-up transformer in a photovoltaic power station; The equivalent impedance of the transformer; Based on the equivalent impedance of the collector lines and the equivalent impedance of the transformer, the total equivalent impedance of the photovoltaic power station is calculated using the following formula: (4) In the formula, Z equ This represents the total equivalent impedance of the photovoltaic power station.

[0008] In one possible design, the reactive power balance relationship is expressed as: (5) (6) In the formula, This is the sum of the reactive power output of each photovoltaic power generation unit; This is the sum of the reactive power output of all reactive power compensation devices; This is the sum of reactive power consumption of the transmission line and reactive power consumption of the transformer. X equ The equivalent reactance of the collector line and the transformer in the station; Q Reactive power; For the first i Reactive power output of each photovoltaic power generation unit; For reactive power output of reactive power compensation equipment;Q line This refers to reactive power consumption of the line. Q tj This refers to the reactive power loss of each transformer unit within the photovoltaic power station. Q T This is the reactive power loss of the main step-up transformer.

[0009] In one possible design, based on the reactive power balance relationship and a preset grid voltage reference value, the grid connection point voltage of the photovoltaic power station is calculated using the following formula. U pv : (7) In the formula, U is the preset reference value of the mains voltage; R g and X g These are the equivalent resistance and equivalent reactance on the grid side, respectively; P Active power; Q Reactive power; based on U pv For a constant steady-state control target, the reactive power required to maintain a constant voltage is calculated using the following formula: (8) The constraints that the reactive power supply of the photovoltaic power station must meet are expressed as follows: (9)

[0010] In one possible design, the weighting coefficients are calculated using the following formula: (10) In the formula, These are weighting coefficients; S VQi Capacity of each photovoltaic unit; The remaining reactive power is allocated to each photovoltaic power generation unit using the following formula: (11) In the formula, For the first i The reactive power setpoint of each photovoltaic power generation unit; This is the total reactive power setpoint for the power station.

[0011] In one possible design, based on the obtained data from each power generation unit... t The rated capacity and active power output of each inverter are used to distribute the reactive power allocated by the second-level control to each inverter using the following formula: (12) In the formula, k This refers to the actual number of inverters present in the photovoltaic unit. This represents the maximum reactive power output of each photovoltaic unit. The set inverter capacity constraints are as follows: (13) In the formula, For the first i In the power generation unit, the one involved is the first t The actual rated capacity of the inverter; For the first i In the power generation unit, the one involved is the first t The actual active power output of the inverter; For the first i In the power generation unit, the one involved is the first t The actual reactive power setpoint of the inverter.

[0012] Secondly, this application provides a hierarchical reactive power coordination optimization device for photovoltaic power plants considering SVG access, the device comprising: The equivalent relationship establishment module is configured to establish an equivalent relationship with and without power loss based on the assumption of consistent impedance of each line in the photovoltaic power station and the actual output current of a single photovoltaic power generation unit. The first calculation module is configured to calculate the equivalent impedance of the collector line and the equivalent impedance of the transformer based on the equivalent relationship between power loss and no power loss. The second calculation module is configured to calculate the total equivalent impedance of the photovoltaic power station based on the equivalent impedance of the collector line and the equivalent impedance of the transformer. The balance relationship establishment module is configured to establish a reactive power balance relationship based on the total equivalent impedance of the photovoltaic power station and the active and reactive power transmitted from the photovoltaic power station to the grid. The third calculation module is configured to calculate the grid connection point voltage of the photovoltaic power station based on the reactive power balance relationship and a preset grid voltage reference value. U pv and based on U pv A constant steady-state control objective is to calculate the reactive power required to maintain a constant voltage. The constraint determination module is configured to determine the constraints that the reactive power supply of the photovoltaic power station must meet based on the reactive power required to maintain constant voltage, the total equivalent impedance of the photovoltaic power station, and the reactive power balance relationship. The three-layer control module is configured to allocate reactive power using a three-layer progressive control system based on the constraints that the reactive power supply of the photovoltaic power station must meet. This three-layer progressive control system includes a first-layer control, a second-layer control, and a third-layer control connected sequentially. The first-layer control includes: prioritizing centralized reactive power compensation via the low-voltage side SVG of the main transformer; dynamically adjusting the SVG compensation capacity based on the goal of minimizing collector line losses to maximize the reduction of collector line losses. The second-layer control includes: when the SVG compensation capacity in the first-layer control reaches its upper limit, determining sensitivity-related parameters based on the constraints by analyzing the impact of each photovoltaic power generation unit on the grid connection voltage, calculating weighting coefficients, and allocating the remaining reactive power to each photovoltaic power generation unit. The third-layer control includes: based on the reactive power allocated by the second-layer control, and under the condition of meeting the set inverter capacity constraints, according to the obtained data of each power generation unit... t The rated capacity and active power output of each inverter are used to distribute the reactive power allocated by the second-level control to each inverter.

[0013] Thirdly, embodiments of this application provide an electronic device, including: at least one processor and a memory; the memory stores computer execution instructions; the at least one processor executes the computer execution instructions stored in the memory, causing the at least one processor to perform the hierarchical reactive power coordination optimization method for photovoltaic power plants considering SVG access as described in the first aspect and various possible designs of the first aspect.

[0014] Fourthly, embodiments of this application provide a computer-readable storage medium storing computer-executable instructions. When a processor executes the computer-executable instructions, it implements the hierarchical reactive power coordination optimization method for photovoltaic power plants considering SVG access, as described in the first aspect and various possible designs of the first aspect.

[0015] Fifthly, embodiments of this application provide a computer program product, including a computer program that, when executed by a processor, implements the hierarchical reactive power coordination optimization method for photovoltaic power plants considering SVG access, as described in the first aspect and various possible designs of the first aspect.

[0016] The hierarchical reactive power coordination optimization method, apparatus, equipment, and storage medium for photovoltaic power plants considering SVG access provided in this application have at least the following beneficial effects: This application proposes a hierarchical reactive power coordination optimization strategy considering SVG (Static Var Generator) integration, based on the analysis of the structure and reactive power characteristics of photovoltaic power plants. This strategy achieves hierarchical control of reactive power through three-layer control logic, which improves voltage stability, reduces grid power loss, and enhances inverter reliability. It provides a feasible engineering solution for reactive power and voltage control in photovoltaic power plants and has practical application value in promoting large-scale grid connection of photovoltaic systems. Attached Figure Description

[0017] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0018] Figure 1 A typical topology diagram of a photovoltaic power station in the prior art provided in the embodiments of this application; Figure 2 A schematic diagram of the equivalent structure of a photovoltaic power plant for grid-connected operation provided in an embodiment of this application; Figure 3 A flowchart of a hierarchical reactive power coordination optimization method for photovoltaic power plants considering SVG access is provided in an embodiment of this application; Figure 4 This is a flowchart of reactive power control provided in an embodiment of this application; Figure 5 A flowchart illustrating the implementation of the photovoltaic hierarchical reactive power coordination optimization strategy provided in this application embodiment; Figure 6 A comparison diagram of grid connection point voltages provided in the embodiments of this application; Figure 7 The diagram shows the structure of a hierarchical reactive power coordination optimization device for a photovoltaic power plant considering SVG access, as provided in the embodiments of this application.

[0019] The accompanying drawings have illustrated specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to specific embodiments. Detailed Implementation

[0020] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0021] The collection, storage, use, processing, transmission, provision, and disclosure of financial data or user data involved in the technical solution of this application all comply with the provisions of relevant laws and regulations and do not violate public order and good morals.

[0022] It should be noted that in the embodiments of this application, certain software, components, models and other existing solutions in the industry may be mentioned. These should be regarded as exemplary and are only intended to illustrate the feasibility of implementing the technical solution of this application. However, it does not mean that the applicant has used or necessarily used the solution.

[0023] The technical solution of this application and how the technical solution of this application solves the above-mentioned technical problems are described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of this application will now be described with reference to the accompanying drawings.

[0024] With the continuous expansion of photovoltaic (PV) power plant installed capacity, the reactive power loss problem during grid-connected operation has become increasingly prominent, posing a severe challenge to grid voltage stability. Addressing the core issue of limited inverter voltage regulation capability and the need to draw reactive power from the grid after the increase in active power output of PV power plants, this application provides a hierarchical reactive power coordination optimization method for PV power plants considering SVG (Static Var Generator) access. Essentially, it is a hierarchical reactive power coordination optimization scheme integrating Static Var Generator (SVG) access. Based on the PV power plant topology and reactive power transmission characteristics, this scheme constructs a three-layer progressive control system: reactive power centralized compensation is prioritized through the SVG on the low-voltage side of the main transformer to maximize the reduction of collector line losses; when the SVG compensation capacity reaches its upper limit, the remaining reactive power is then rationally allocated to each PV power generation unit. Simulation results demonstrate that this strategy can strictly control the grid connection point voltage deviation within a stable range, significantly enhancing the voltage stability and economy of PV power plant grid-connected operation. The overall technical approach of this method is as follows: Based on the equivalent impedance model of the photovoltaic power plant's collector lines and transformers, the quantitative relationship between reactive power loss and voltage deviation under grid-connected conditions is derived, and a three-layer reactive power coordination control system is constructed: SVG (Static Var Generator) is preferentially used for centralized compensation to reduce line losses; when the SVG capacity is insufficient, the remaining reactive power is allocated to each photovoltaic power generation unit, and the allocation design is optimized in conjunction with inverter capacity constraints. Finally, a photovoltaic power plant simulation model is constructed using electromagnetic simulation software to verify the compensation effect of this strategy under different voltage deviation conditions.

[0025] To illustrate the method of this application in detail, this embodiment provides a typical topology of a photovoltaic power station to which this method is applied, as shown below. Figure 1As shown. It is understood that the photovoltaic power station exemplified herein is merely one example of the successful application of the method of this application, and does not imply that the method of this application must rely on this photovoltaic power station for implementation. Figure 1 The photovoltaic power station shown is composed of several basic photovoltaic power generation units connected in parallel. n The collection lines collect the electrical energy, which is then transmitted to the grid connection point. Since photovoltaic arrays typically require a large area and the photovoltaic power generation units are spatially dispersed, the collection lines are connected in parallel. m There are 10 photovoltaic power generation units, of which Z nm Z represents the impedance parameter of the collector line. g The equivalent impedance value corresponding to the power grid side, Z r Represents the equivalent impedance of the main transformer. Represents each photovoltaic power generation unit.

[0026] When a photovoltaic (PV) system moderately increases its active power output while minimizing the reactive power output of the grid-connected inverter, the reactive power losses generated by the step-up transformer will be difficult to compensate for. In this situation, the PV power plant needs to obtain the required reactive power from the grid, thus hindering the inverter's voltage regulation performance. Therefore, it is necessary to scientifically configure SVG (Static Var Generator) reactive power compensation devices on the low-voltage side of the main transformer to enhance reactive power regulation efficiency and improve the voltage control accuracy of the PV power plant.

[0027] Most photovoltaic (PV) power plants are located in remote, open areas where loads are dispersed and transmission lines are typically long. When the installed capacity of a PV power plant is close to the local load level, it can significantly impact the voltage stability of the local power grid. Essentially, this stability impact stems from the external characteristics exhibited by the power plant as a whole operating unit. Figure 2 This is a schematic diagram of the equivalent structure of a photovoltaic power plant operating in grid-connected mode. R equ Characterizes the equivalent resistance of the collector line and the transformer within the station. X equ Characterizes the equivalent reactance of the collector line and the transformer in the station.

[0028] Specifically, such as Figure 3 As shown, when the hierarchical reactive power coordination optimization method for photovoltaic power plants considering SVG access is applied to the aforementioned photovoltaic power plants, it includes the following steps S10-S70.

[0029] S10: Based on the assumption that the impedance of each line in a photovoltaic power station is consistent and the actual output current of a single photovoltaic power generation unit, establish the equivalent relationship between power loss and no power loss.

[0030] In this embodiment, it is assumed that Figure 1Since the impedances of all lines are consistent, i.e., Z11=Z21=…=Znm=Z, when the active power loss and reactive power loss of the photovoltaic power station are equal, the equivalent relationship between active power loss and reactive power loss can be expressed as: (1) In the formula, I pv This refers to the actual output current of a single photovoltaic power generation unit. Z The impedance of a single line; n The number of circuits in the collector line; m This refers to the number of photovoltaic power generation units connected to each collector line; Z T The equivalent impedance of the main transformer; The equivalent impedance of the collector line; Z t The equivalent impedance of the step-up transformer in a photovoltaic power station. This is the equivalent impedance of the transformer.

[0031] S20: Based on the equivalent relationship between power loss and no power loss, calculate the equivalent impedance of the collector line and the equivalent impedance of the transformer.

[0032] In this embodiment, based on the equivalent relationship between power loss and no power loss shown in formula (1), Figure 2 The equivalent impedance of each component (including collector lines and transformers) can be expressed as: (2) (3) In the formula, Z The impedance of a single line; n The number of circuits in the collector line; m This refers to the number of photovoltaic power generation units connected to each collector line; Z T The equivalent impedance of the main transformer; The equivalent impedance of the collector line; Z t The equivalent impedance of the step-up transformer in a photovoltaic power station; This is the equivalent impedance of the transformer.

[0033] S30: Calculate the total equivalent impedance of the photovoltaic power station based on the equivalent impedance of the collector line and the equivalent impedance of the transformer.

[0034] In this embodiment, the formula for calculating the total equivalent impedance Zequ of the photovoltaic power station is expressed as follows: (4) In the formula, Z equ This represents the total equivalent impedance of the photovoltaic power station.

[0035] S40: Based on the total equivalent impedance of the photovoltaic power station, establish a reactive power balance relationship according to the active power and reactive power transmitted from the photovoltaic power station to the grid.

[0036] In this embodiment, if the active power transmitted from the photovoltaic power station to the grid is P reactive power is Q The reactive power balance relationship is then determined as follows: (5) (6) In the formula, This is the sum of the reactive power output of each photovoltaic power generation unit; This is the sum of the reactive power output of all reactive power compensation devices; This is the sum of reactive power consumption of the transmission line and reactive power consumption of the transformer. X equ The equivalent reactance of the collector line and the transformer in the station; Q Reactive power; For the first i Reactive power output of each photovoltaic power generation unit; For reactive power output of reactive power compensation equipment; Q line This refers to reactive power consumption of the line. Q tj This refers to the reactive power loss of each transformer unit within the photovoltaic power station. Q T This is the reactive power loss of the main step-up transformer.

[0037] S50: Calculate the grid connection voltage of the photovoltaic power station based on the reactive power balance relationship and the preset grid voltage reference value. U pv and based on U pv A constant steady-state control objective is defined by calculating the reactive power required to maintain a constant voltage.

[0038] In this embodiment, the preset grid voltage reference value is U, and the grid connection point voltage of the photovoltaic power station is calculated using the following formula. U pv : (7) In the formula, U is the preset reference value of the mains voltage; R g and X g These are the equivalent resistance and equivalent reactance on the grid side, respectively; P Active power; Q This refers to reactive power.

[0039] If a photovoltaic power station implements reasonable control over reactive power and voltage, under steady-state conditions... If the value of remains constant, then the reactive power of the system is: (8) S60: Based on the reactive power required to maintain a constant voltage, the total equivalent impedance of the photovoltaic power station, and the reactive power balance relationship, determine the constraints that the reactive power supply of the photovoltaic power station must meet.

[0040] In this embodiment, based on steps S10-S50 above, in order to maintain a constant grid connection point voltage, the reactive power of the photovoltaic power station should meet the following constraints: (9)

[0041] S70: Based on the constraints that the reactive power supply of photovoltaic power plants must meet, a three-layer progressive control system is adopted to allocate reactive power.

[0042] When the inverter has no reactive power output and the photovoltaic power station has not deployed a reactive power compensation device, continuously increasing the active power output will cause the grid connection point voltage to deviate significantly from the rated range. Therefore, to achieve precise control of the grid connection point voltage, it is necessary to configure adaptive reactive power and voltage control equipment. The core control objective of the photovoltaic power station's grid connection point voltage is to maintain the voltage setpoint or initial operating parameters through real-time dynamic scheduling. The reactive power sources of photovoltaic power stations are mainly divided into two categories: grid-connected inverters and reactive power compensation devices. The mainstream configuration is to deploy reactive power compensation devices on the low-voltage side of the main transformer. Among them, SVG (Static Var Generator) is preferred due to its fast response speed and excellent adjustment response time, which can significantly reduce grid power loss and improve the stability and reliability of inverter operation. It can be seen that regulating the output characteristics of the reactive power compensation device is the core path to achieve on-demand reactive power supply from photovoltaic power generation units. The reactive power and voltage control process of the photovoltaic power station designed in this embodiment is as follows: Figure 4 As shown. First, it determines whether the grid-connected bus voltage of the photovoltaic power station exceeds the control range. If the result of this determination is negative, it returns to this determination step; if the result is positive, it adjusts the reactive power compensation device of the photovoltaic power station. After completing this operation, it determines whether the capacity of the reactive power compensation device has reached its limit. If the result of this determination is negative, it returns to the operation step of adjusting the reactive power compensation device of the photovoltaic power station; if the result is positive, it adjusts the reactive power output of the photovoltaic power generation unit, and then the process ends.

[0043] Specifically, the three-layer progressive control system includes three sequentially connected layers: a first layer, a second layer, and a third layer. The first layer includes: prioritizing centralized reactive power compensation via the low-voltage side SVG of the main transformer; dynamically adjusting the SVG compensation capacity based on the goal of minimizing collector line losses to maximize the reduction of collector line losses. The second layer includes: when the SVG compensation capacity in the first layer reaches its upper limit, determining sensitivity-related parameters based on constraints by analyzing the impact of each photovoltaic power generation unit on the grid connection voltage, calculating weighting coefficients, and allocating the remaining reactive power to each photovoltaic power generation unit. The third layer includes: based on the reactive power allocated by the second layer control, and under the condition of meeting the set inverter capacity constraints, adjusting the compensation capacity according to the obtained data from each power generation unit... t The rated capacity and active power output of each inverter are used to distribute the reactive power allocated by the second-level control to each inverter.

[0044] In one specific implementation, the above three-layer progressive control system can be designed as follows: Figure 5 The photovoltaic hierarchical reactive power coordination optimization strategy is shown. This strategy adopts a three-layer reactive power control architecture, as detailed below: The first layer prioritizes centralized regulation using reactive power compensation devices to reduce the reactive power transmission scale of the collector lines, decrease power loss, and improve inverter operational reliability. This is achieved by installing an SVG (Static Var Generator) of appropriate capacity on the low-voltage side of the main transformer.

[0045] The second layer involves allocating surplus reactive power to each photovoltaic power generation unit according to reasonable principles when the reactive power compensation device reaches its capacity limit. This allocation is based on sensitivity calculation using weighted coefficients. The weighted coefficients are calculated as follows: (10) In the formula, These are weighting coefficients; S VQi This represents the capacity of each photovoltaic unit.

[0046] Based on the weighting coefficients, the given value for reactive power is: (11) In the formula, For the first i The reactive power setpoint of each photovoltaic power generation unit; This is the total reactive power setpoint for the power station.

[0047] The third layer addresses the capacity constraints of grid-connected inverters. Photovoltaic power generation units typically employ a parallel structure of multiple sub-units. Therefore, reactive power must be evenly distributed to each inverter according to actual operational needs. As seen in the second-layer control logic, it allocates appropriate reactive power setpoints to each photovoltaic power generation unit, ensuring all inverters have consistent reactive power margins and effectively preventing voltage exceeding limits and inverter chain reactions. The specific principle is as follows: (12) In the formula, k This refers to the actual number of inverters present in the photovoltaic unit. This represents the maximum reactive power output of each photovoltaic unit.

[0048] The reactive power output of the inverter needs to take into account its own capacity limitations. In this embodiment, the inverter capacity constraint is set as follows: (13) In the formula, For the first i In the power generation unit, the one involved is the first t The actual rated capacity of the inverter; For the first i In the power generation unit, the one involved is the first t The actual active power output of the inverter; For the first i In the power generation unit, the one involved is the first t The actual reactive power setpoint of the inverter.

[0049] To further illustrate the feasibility and advancement of the method proposed in this application, a simulation model of a photovoltaic power station in a certain region was built using electromagnetic transient simulation software, adopting an operation mode of reactive power compensation through coordinated inverter and SVG. First, the real-time reactive power deficit at the connection point voltage was calculated. After determining the upper limit of the reactive power compensation capacity of the inverter and SVG, the required reactive power compensation capacity was then evenly distributed among the photovoltaic power generation units. The specific calculation results of the reactive power deficit at the connection point are shown in Table 1.

[0050] Table 1 Reactive power deficit at access points

[0051] Based on the calculation results of reactive power compensation required at the photovoltaic power plant access point, reactive power is reasonably allocated between the inverter and SVG to achieve the control objective of minimizing the voltage deviation at the access point. The reference values ​​of reactive power compensation required by the inverter and SVG under each voltage deviation condition are calculated. Detailed calculation data are shown in Table 2.

[0052] Table 2. Reactive power reference quantities required for inverter and SVG compensation under various voltage deviation conditions.

[0053] Comparison of grid connection point voltage before and after the application of the control strategy, as follows: Figure 6 As shown, when the active power is 50MW, the actual measured value of the grid connection point voltage without applying this control strategy is 0.898pu; while after the photovoltaic power station adopts the reactive power voltage support control strategy, the grid connection point voltage is maintained in the range of 0.9819-1.014pu, effectively ensuring the stable operation of the grid connection voltage.

[0054] In summary, this embodiment, through analysis of the structure and reactive power characteristics of photovoltaic power plants (corresponding to steps SS10-S60 above), proposes a hierarchical reactive power coordination optimization strategy considering SVG access (corresponding to step S70 above). This strategy achieves hierarchical control of reactive power through three-layer control logic. This strategy can improve voltage stability, reduce grid power loss, and enhance inverter reliability, providing a feasible engineering solution for reactive power and voltage control of photovoltaic power plants, and has practical application value for promoting large-scale grid connection of photovoltaic power plants.

[0055] This application also provides a hierarchical reactive power coordination optimization device for photovoltaic power plants that considers SVG access, such as... Figure 7 As shown, the hierarchical reactive power coordination optimization device for photovoltaic power plants considering SVG access includes: The equivalent relationship establishment module 701 is configured to establish an equivalent relationship with and without power loss based on the assumption of consistent impedance of each line in the photovoltaic power station and the actual output current of a single photovoltaic power generation unit. The first calculation module 702 is configured to calculate the equivalent impedance of the collector line and the equivalent impedance of the transformer based on the equivalent relationship between power loss and no power loss. The second calculation module 703 is configured to calculate the total equivalent impedance of the photovoltaic power station based on the equivalent impedance of the collector line and the equivalent impedance of the transformer. The balance relationship establishment module 704 is configured to establish a reactive power balance relationship based on the total equivalent impedance of the photovoltaic power station and the active and reactive power transmitted from the photovoltaic power station to the grid. The third calculation module 705 is configured to calculate the grid connection voltage of the photovoltaic power station based on the reactive power balance relationship and a preset grid voltage reference value. U pv and based on U pv A constant steady-state control objective is to calculate the reactive power required to maintain a constant voltage. The constraint determination module 706 is configured to determine the constraints that the reactive power supply of the photovoltaic power station must meet based on the reactive power required to maintain a constant voltage, the total equivalent impedance of the photovoltaic power station, and the reactive power balance relationship. The three-layer control module 707 is configured to allocate reactive power using a three-layer progressive control system based on the constraints that the reactive power supply of the photovoltaic power station must meet. The three-layer progressive control system includes a first-layer control, a second-layer control, and a third-layer control connected sequentially. The first-layer control includes: prioritizing centralized reactive power compensation via the low-voltage side SVG of the main transformer; dynamically adjusting the SVG compensation capacity based on the goal of minimizing collector line losses to maximize the reduction of collector line losses. The second-layer control includes: when the SVG compensation capacity in the first-layer control reaches its upper limit, determining sensitivity-related parameters based on the constraints by analyzing the impact of each photovoltaic power generation unit on the grid connection voltage, calculating weighting coefficients, and allocating the remaining reactive power to each photovoltaic power generation unit. The third-layer control includes: based on the reactive power allocated by the second-layer control, and under the condition of meeting the set inverter capacity constraints, according to the obtained data of each power generation unit... t The rated capacity and active power output of each inverter are used to distribute the reactive power allocated by the second-level control to each inverter.

[0056] This application provides an electronic device. The electronic device may include a processor and a memory, wherein the processor and the memory can communicate; exemplarily, the processor and the memory communicate via a communication bus.

[0057] The processor executes computer execution instructions stored in memory, causing the processor to perform the scheme in the above embodiments. The processor can be a general-purpose processor, including a central processing unit (CPU), a network processor (NP), etc.; it can also be a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components.

[0058] The communication bus can be a Peripheral Component Interconnect (PCI) bus or an Extended Industry Standard Architecture (EISA) bus, etc. The system bus can be divided into address bus, data bus, control bus, etc. Transceivers are used to enable communication between database access devices and other computers (e.g., clients, read-write libraries, and read-only libraries). Memory may include random access memory (RAM) and may also include non-volatile memory.

[0059] The electronic device provided in this application embodiment can be the terminal device described in the above embodiments.

[0060] This application also provides a computer-readable storage medium storing computer instructions. When the computer instructions are executed on a computer, the computer performs the technical solution of the hierarchical reactive power coordination optimization method for photovoltaic power plants considering SVG access described in the above embodiments.

[0061] This application also provides a computer program product, which includes a computer program stored in a computer-readable storage medium. At least one processor can read the computer program from the computer-readable storage medium. When the at least one processor executes the computer program, it can implement the technical solution of the hierarchical reactive power coordination optimization method for photovoltaic power plants considering SVG access in the above embodiments.

[0062] In the several embodiments provided in this application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative; for instance, the division of modules is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple modules may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be indirect coupling or communication connection through some interfaces, devices, or modules, and may be electrical, mechanical, or other forms.

[0063] The modules described as separate components may or may not be physically separate. The components shown as modules may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to implement the solution of this embodiment according to actual needs.

[0064] Furthermore, the functional modules in the various embodiments of this application can be integrated into one processing unit, or each module can exist physically separately, or two or more modules can be integrated into one unit. The unit composed of the above modules can be implemented in hardware or in the form of hardware plus software functional units.

[0065] The integrated modules described above, implemented as software functional modules, can be stored in a computer-readable storage medium. These software functional modules, stored in a storage medium, include several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) or processor to execute some steps of the methods of the various embodiments of this application.

[0066] It should be understood that the aforementioned processor can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), etc. A general-purpose processor can be a microprocessor or any conventional processor. The steps of the method disclosed in this invention can be directly manifested as execution by a hardware processor, or execution by a combination of hardware and software modules within the processor.

[0067] The memory may include high-speed RAM, and may also include non-volatile storage (NVM), such as at least one disk storage device, and may also be a USB flash drive, external hard drive, read-only memory, disk or optical disc, etc.

[0068] Buses can be Industry Standard Architecture (ISA) buses, Peripheral Component Interconnect (PCI) buses, or Extended Industry Standard Architecture (EISA) buses, etc. Buses can be categorized into address buses, data buses, control buses, etc.

[0069] The aforementioned storage medium can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as static random access memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable read-only memory (PROM), read-only memory (ROM), magnetic storage, flash memory, magnetic disk, or optical disk. The storage medium can be any available medium that can be accessed by a general-purpose or special-purpose computer.

[0070] An exemplary storage medium is coupled to a processor, enabling the processor to read information from and write information to the storage medium. Alternatively, the storage medium can be an integral part of the processor. The processor and storage medium can reside in an Application Specific Integrated Circuit (ASIC). Alternatively, the processor and storage medium can exist as discrete components in an electronic control unit or main control device.

[0071] Those skilled in the art will understand that all or part of the steps of the above-described method embodiments can be implemented by hardware related to program instructions. The aforementioned program can be stored in a computer-readable storage medium. When executed, the program performs the steps of the above-described method embodiments; and the aforementioned storage medium includes various media capable of storing program code, such as ROM, RAM, magnetic disks, or optical disks.

[0072] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A hierarchical reactive power coordination optimization method for photovoltaic power plants considering SVG access, characterized in that, The method includes: Based on the assumption that the impedance of each line in a photovoltaic power station is consistent and the actual output current of a single photovoltaic power generation unit, an equivalent relationship between power loss and no power loss is established. Based on the equivalent relationship between power loss and no power loss, calculate the equivalent impedance of the collector line and the equivalent impedance of the transformer. Calculate the total equivalent impedance of the photovoltaic power station based on the equivalent impedance of the collector lines and the transformer. Based on the total equivalent impedance of the photovoltaic power station, a reactive power balance relationship is established according to the active power and reactive power transmitted from the photovoltaic power station to the grid. Based on the aforementioned reactive power balance relationship and the preset grid voltage reference value, the grid connection point voltage of the photovoltaic power station is calculated. U pv and based on U pv A constant steady-state control objective is to calculate the reactive power required to maintain a constant voltage. Based on the reactive power required to maintain constant voltage, the total equivalent impedance of the photovoltaic power station, and the reactive power balance relationship, the constraints that the reactive power supply of the photovoltaic power station must meet are determined. Based on the constraints that the reactive power supply of the photovoltaic power station must meet, a three-layer progressive control system is adopted to allocate reactive power. This three-layer progressive control system includes a first-layer control, a second-layer control, and a third-layer control connected sequentially. The first-layer control includes: prioritizing centralized reactive power compensation through the low-voltage side SVG of the main transformer; dynamically adjusting the SVG compensation capacity based on the goal of minimizing collector line losses to maximize the reduction of collector line losses. The second-layer control includes: when the SVG compensation capacity in the first-layer control reaches its upper limit, based on the constraints, determining sensitivity-related parameters by analyzing the impact of each photovoltaic power generation unit on the grid connection point voltage, calculating weighting coefficients, and allocating the remaining reactive power to each photovoltaic power generation unit. The third-layer control includes: based on the reactive power allocated by the second-layer control, and under the condition of meeting the set inverter capacity constraints, according to the obtained data of each power generation unit... t The rated capacity and active power output of each inverter are used to distribute the reactive power allocated by the second-level control to each inverter.

2. The hierarchical reactive power coordination optimization method for photovoltaic power plants considering SVG access according to claim 1, characterized in that, The equivalent relationship between power loss and no power loss is expressed as follows: (1) In the formula, I pv This refers to the actual output current of a single photovoltaic power generation unit. Z The impedance of a single line; n The number of circuits in the collector line; m This refers to the number of photovoltaic power generation units connected to each collector line; Z T The equivalent impedance of the main transformer; The equivalent impedance of the collector line; Z t The equivalent impedance of the step-up transformer in a photovoltaic power station. This is the equivalent impedance of the transformer.

3. The hierarchical reactive power coordination optimization method for photovoltaic power plants considering SVG access according to claim 1, characterized in that, Based on the equivalent relationship between power loss and no power loss, the equivalent impedance of the collector line and the equivalent impedance of the transformer are calculated using the following formulas: (2) (3) In the formula, Z The impedance of a single line; n The number of circuits in the collector line; m This refers to the number of photovoltaic power generation units connected to each collector line; Z T The equivalent impedance of the main transformer; The equivalent impedance of the collector line; Z t The equivalent impedance of the step-up transformer in a photovoltaic power station; The equivalent impedance of the transformer; Based on the equivalent impedance of the collector lines and the equivalent impedance of the transformer, the total equivalent impedance of the photovoltaic power station is calculated using the following formula: (4) In the formula, Z equ This represents the total equivalent impedance of the photovoltaic power station.

4. The hierarchical reactive power coordination optimization method for photovoltaic power plants considering SVG access according to claim 3, characterized in that, The reactive power balance relationship is expressed as follows: (5) (6) In the formula, This is the sum of the reactive power output of each photovoltaic power generation unit; This is the sum of the reactive power output of all reactive power compensation devices; This is the sum of reactive power consumption of the transmission line and reactive power consumption of the transformer. X equ The equivalent reactance of the collector line and the transformer in the station; Q Reactive power; For the first i Reactive power output of each photovoltaic power generation unit; For reactive power output of reactive power compensation equipment; Q line This refers to reactive power consumption of the line. Q tj This refers to the reactive power loss of each transformer unit within the photovoltaic power station. Q T This is the reactive power loss of the main step-up transformer.

5. The hierarchical reactive power coordination optimization method for photovoltaic power plants considering SVG access according to claim 4, characterized in that, Based on the aforementioned reactive power balance relationship and the preset grid voltage reference value, the grid connection point voltage of the photovoltaic power station is calculated using the following formula. U pv : (7) In the formula, U is the preset reference value of the mains voltage; R g and X g These are the equivalent resistance and equivalent reactance on the grid side, respectively; P Active power; Q Reactive power; based on U pv For a constant steady-state control target, the reactive power required to maintain a constant voltage is calculated using the following formula: (8) The constraints that the reactive power supply of the photovoltaic power station must meet are expressed as follows: (9)。 6. The hierarchical reactive power coordination optimization method for photovoltaic power plants considering SVG access according to claim 1, characterized in that... The formula for calculating the weighting coefficient is as follows: (10) In the formula, These are weighting coefficients; S VQi Capacity of each photovoltaic unit; The remaining reactive power is allocated to each photovoltaic power generation unit using the following formula: (11) In the formula, For the first i The reactive power setpoint of each photovoltaic power generation unit; This is the total reactive power setpoint for the power station.

7. The hierarchical reactive power coordination optimization method for photovoltaic power plants considering SVG access according to claim 1, characterized in that, According to the obtained data from each power generation unit, the first... t The rated capacity and active power output of each inverter are used to distribute the reactive power allocated by the second-level control to each inverter using the following formula: (12) In the formula, k This refers to the actual number of inverters present in the photovoltaic unit. This represents the maximum reactive power output of each photovoltaic unit. The set inverter capacity constraints are as follows: (13) In the formula, For the first i In the power generation unit, the one involved is the first t The actual rated capacity of the inverter; For the first i In the power generation unit, the one involved is the first t The actual active power output of the inverter; For the first i In the power generation unit, the one involved is the first t The actual reactive power setpoint of the inverter.

8. A hierarchical reactive power coordination optimization device for photovoltaic power plants considering SVG access, characterized in that, The device includes: The equivalent relationship establishment module is configured to establish an equivalent relationship with and without power loss based on the assumption of consistent impedance of each line in the photovoltaic power station and the actual output current of a single photovoltaic power generation unit. The first calculation module is configured to calculate the equivalent impedance of the collector line and the equivalent impedance of the transformer based on the equivalent relationship between power loss and no power loss. The second calculation module is configured to calculate the total equivalent impedance of the photovoltaic power station based on the equivalent impedance of the collector line and the equivalent impedance of the transformer. The balance relationship establishment module is configured to establish a reactive power balance relationship based on the total equivalent impedance of the photovoltaic power station and the active and reactive power transmitted from the photovoltaic power station to the grid. The third calculation module is configured to calculate the grid connection point voltage of the photovoltaic power station based on the reactive power balance relationship and a preset grid voltage reference value. U pv and based on U pv A constant steady-state control objective is to calculate the reactive power required to maintain a constant voltage. The constraint determination module is configured to determine the constraints that the reactive power supply of the photovoltaic power station must meet based on the reactive power required to maintain constant voltage, the total equivalent impedance of the photovoltaic power station, and the reactive power balance relationship. The three-layer control module is configured to allocate reactive power using a three-layer progressive control system based on the constraints that the reactive power supply of the photovoltaic power station must meet. This three-layer progressive control system includes a first-layer control, a second-layer control, and a third-layer control connected sequentially. The first-layer control includes: prioritizing centralized reactive power compensation via the low-voltage side SVG of the main transformer; dynamically adjusting the SVG compensation capacity based on the goal of minimizing collector line losses to maximize the reduction of collector line losses. The second-layer control includes: when the SVG compensation capacity in the first-layer control reaches its upper limit, determining sensitivity-related parameters based on the constraints by analyzing the impact of each photovoltaic power generation unit on the grid connection voltage, calculating weighting coefficients, and allocating the remaining reactive power to each photovoltaic power generation unit. The third-layer control includes: based on the reactive power allocated by the second-layer control, and under the condition of meeting the set inverter capacity constraints, according to the obtained data of each power generation unit... t The rated capacity and active power output of each inverter are used to distribute the reactive power allocated by the second-level control to each inverter.

9. An electronic device, characterized in that, include: A processor, and a memory communicatively connected to the processor; The memory stores computer-executed instructions; The processor executes the computer execution instructions stored in the memory to implement the hierarchical reactive power coordination optimization method for photovoltaic power plants considering SVG access as described in any one of claims 1-7.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer-executable instructions, which, when executed by a processor, are used to implement the hierarchical reactive power coordination optimization method for photovoltaic power plants considering SVG access as described in any one of claims 1-7.

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