Reactive power circulating flow analysis and control method and device for grid-forming hybrid new energy station

Abstract

This application provides a method and apparatus for reactive power circulation analysis and control in a grid-connected hybrid renewable energy power station. The method includes: constructing an equivalent model of the grid-connected hybrid renewable energy power station, in which the grid-connected units in the renewable energy power station are equivalent to one equivalent grid-connected unit, connected to the point of common coupling (PCC) via a first line reactor; and the grid-connected units in the renewable energy power station are equivalent to one equivalent grid-connected unit, connected to the PCC via a second line reactor, the PCC being connected to the power grid via a third line reactor; obtaining the reactive power of the grid-connected units and the voltage amplitude of the grid-connected units based on the equivalent model; and limiting the values ​​of the voltage control command for the grid-connected units and the reactive power control command for the grid-connected units by analyzing the reactive power of the grid-connected units and the voltage amplitude of the grid-connected units, so as to ensure that reactive power circulation is suppressed within any given target range of PCC voltage.

Description

Technical Field

[0001] This application relates to the field of stability analysis technology for new energy power systems, and in particular to a reactive power circulation analysis and control method and device for hybrid new energy power plants with integrated grids. Background Technology

[0002] Grid-connected generating units have advantages in stable operation and frequency and voltage support under weak grid conditions, but they also have disadvantages such as reduced power generation efficiency and increased investment and operating costs. Hybrid grid-connected / integrated power plants will become the mainstream form of new energy power plants during the transition period of new energy equipment upgrades. When both grid-connected and integrated generating units operate in PQ control mode, reactive power circulation will not occur because the reactive power control commands are uniformly issued by the automatic voltage control system (AVC) of the power plant. However, when grid-connected units operate in PV mode and integrated grid-connected units operate in PQ mode, reactive power circulation will occur between the units if the voltage commands issued by the AVC system to the grid-connected units and the reactive power commands issued to the integrated grid-connected units are unreasonable. Currently, there is no quantitative analysis method for reactive power circulation in hybrid grid-connected new energy power plants. Accurate quantitative analysis of reactive power circulation in hybrid grid-connected new energy power plants can provide a reference for the AVC system to issue control commands reasonably when performing voltage control. Summary of the Invention

[0003] In view of this, this application provides a reactive power circulation analysis and control method and device for a grid-connected hybrid renewable energy power station to solve at least one of the aforementioned problems.

[0004] To achieve the above objectives, this application adopts the following approach: According to a first aspect of this application, a method for reactive power circulation analysis and control of a grid-connected hybrid renewable energy power station is provided. The method includes: constructing an equivalent model of the grid-connected hybrid renewable energy power station; in the equivalent model, the grid-connected generating units within the renewable energy power station are equivalent to a single equivalent grid-connected generating unit, connected to the point of common coupling (PCC) via a first line reactor; and the grid-connected generating units within the renewable energy power station are equivalent to a single equivalent grid-connected generating unit, connected to the PCC via a second line reactor, the PCC being connected to the power grid via a third line reactor; obtaining the reactive power of the grid-connected generating units and the voltage amplitude of the grid-connected generating units based on the equivalent model; and limiting the values ​​of the voltage control command for the grid-connected generating units and the reactive power control command for the grid-connected generating units by analyzing the reactive power of the grid-connected generating units and the voltage amplitude of the grid-connected generating units, to ensure that reactive power circulation is suppressed within a target range of any given PCC voltage.

[0005] In some embodiments of this application, the effects of line resistance and capacitance are ignored for the first line reactance, the second line reactance, and the third line reactance in the above method.

[0006] In some embodiments of this application, the method described above for obtaining the reactive power of the grid-connected generator unit and the voltage amplitude of the grid-connected generator unit based on the equivalent model includes: obtaining the system active power flow equation from the point of common coupling to the power grid, wherein the system active power flow equation includes the first active power of the equivalent grid-connected generator unit, the second active power of the equivalent grid-connected generator unit, the voltage and voltage phase angle of the point of common coupling, and the third line reactance; obtaining the grid current based on the voltage, voltage phase angle, and third line reactance of the point of common coupling; obtaining the first branch current of the equivalent grid-connected generator unit based on the second active power and the first reactive power of the equivalent grid-connected generator unit measured at the point of common coupling; obtaining the reactive power of the grid-connected generator unit based on the first reactive power, the first branch current, and the second line reactance; and obtaining the voltage amplitude of the grid-connected generator unit based on the second branch current of the equivalent grid-connected generator unit, the first line reactance, the voltage and voltage phase angle of the point of common coupling.

[0007] In some embodiments of this application, limiting the values ​​of the voltage control command for grid-connected units and the reactive power control command for grid-connected units in the above method includes: if the voltage amplitude of the grid-connected unit is a fixed value and does not fall within the range of 0.95pu to 1pu, the reactive power of the grid-connected unit is increased to suppress reactive circulating current.

[0008] In some embodiments of this application, limiting the values ​​of the voltage control command for the grid-connected generator unit and the reactive power control command for the grid-connected generator unit in the above method further includes: if the reactive power of the grid-connected generator unit is less than 0 and is a constant value, suppressing reactive circulating current by gradually reducing the voltage amplitude of the grid-connected generator unit; if the reactive power of the grid-connected generator unit is equal to 0.05pu or 0.1pu, suppressing reactive circulating current by gradually increasing the voltage amplitude of the grid-connected generator unit.

[0009] In some embodiments of this application, limiting the values ​​of the voltage control command for grid-connected units and the reactive power control command for grid-connected units in the above method further includes: when the system short-circuit ratio is lower than a preset threshold, increasing the adjustment range of the voltage control command for grid-connected units, or adjusting the reference value of the reactive power control command for grid-connected units, so as to expand the reactive power circulating current suppression region.

[0010] According to a second aspect of this application, a reactive power circulation analysis and control device for a grid-connected hybrid renewable energy power station is provided. The device includes: an equivalent model construction unit, used to construct an equivalent model of the grid-connected hybrid renewable energy power station, in which the grid-connected units within the renewable energy power station are equivalent to a single equivalent grid-connected unit, connected to the point of common coupling (PCC) via a first line reactor; and the grid-connected units within the renewable energy power station are equivalent to a single equivalent grid-connected unit, connected to the PCC via a second line reactor, the PCC being connected to the power grid via a third line reactor; a power and amplitude acquisition unit, used to acquire the reactive power of the grid-connected units and the voltage amplitude of the grid-connected units based on the equivalent model; and an analysis and control unit, used to limit the values ​​of the voltage control command for the grid-connected units and the reactive power control command for the grid-connected units by analyzing the reactive power of the grid-connected units and the voltage amplitude of the grid-connected units, to ensure that reactive power circulation is suppressed within a target range of any given PCC voltage.

[0011] In some embodiments of this application, the effects of line resistance and capacitance are ignored for the first line reactance, the second line reactance, and the third line reactance.

[0012] In some embodiments of this application, the power and amplitude acquisition unit includes: a power flow equation acquisition module, used to acquire the system active power flow equation from the point of common coupling to the power grid, the system active power flow equation including the first active power of the equivalent grid-type generator, the second active power of the equivalent follow-grid generator, the voltage and voltage phase angle of the point of common coupling, and the third line reactance; a grid current acquisition module, used to obtain the grid current based on the voltage, voltage phase angle, and third line reactance of the point of common coupling; a branch current acquisition module, used to obtain the first branch current of the equivalent follow-grid generator based on the second active power and the first reactive power measured at the point of common coupling of the equivalent follow-grid generator; a reactive power acquisition module, used to obtain the reactive power of the follow-grid generator based on the first reactive power, the first branch current, and the second line reactance; and a voltage amplitude acquisition module, used to obtain the voltage amplitude of the grid-type generator based on the second branch current of the equivalent grid-type generator, the first line reactance, the voltage and voltage phase angle of the point of common coupling.

[0013] In some embodiments of this application, the above-mentioned analysis and control unit includes: a first control module, used to suppress reactive circulating current by increasing the reactive power of the grid-connected unit when the voltage amplitude of the grid-connected unit is a fixed value and does not fall within the range of 0.95pu to 1pu.

[0014] In some embodiments of this application, the above-mentioned analysis and control unit further includes: a second control module, used to suppress reactive circulating current by gradually reducing the voltage amplitude of the grid-connected unit when the reactive power of the grid-connected unit is less than 0 and is a constant value; and to suppress reactive circulating current by gradually increasing the voltage amplitude of the grid-connected unit when the reactive power of the grid-connected unit is equal to 0.05pu or 0.1pu.

[0015] In some embodiments of this application, the above-mentioned analysis and control unit further includes: a third control module, used to increase the adjustment range of the voltage control command of the grid-connected unit or adjust the reference value of the reactive power control command of the grid-connected unit when the system short-circuit ratio is lower than a preset threshold, so as to expand the reactive power circulating current suppression area.

[0016] According to a third aspect of this application, an electronic device is provided, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of the method described above.

[0017] According to a fourth aspect of this application, a computer-readable storage medium is provided, on which a computer program is stored, which, when executed by a processor, implements the steps of the above-described method.

[0018] According to a fifth aspect of this application, a computer program product is provided, comprising a computer program / instructions that, when executed by a processor, implement the steps of the above-described method.

[0019] The reactive power circulation analysis and control method and device for grid-connected hybrid renewable energy power plants proposed in this application fill the gap in the current lack of quantitative analysis methods for reactive power circulation in grid-connected hybrid renewable energy power plants. It can analyze the relationship between the values ​​of voltage control commands for grid-connected units and reactive power control commands for grid-connected units and reactive power circulation. The analysis results can be used as a reference for AVC systems to reasonably issue control commands when performing voltage control, thereby improving the stability and operating efficiency of the system. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In the drawings: Figure 1 This is a flowchart illustrating a method for reactive power circulation analysis and control of a hybrid renewable energy power station based on a grid-connected network, as provided in an embodiment of this application. Figure 2This is a system topology diagram of an equivalent model of a grid-connected hybrid new energy power station provided in an embodiment of this application; Figure 3 This is a schematic diagram of the process for obtaining the reactive power of grid-connected units and the voltage amplitude of grid-connected units provided in the embodiments of this application; Figure 4 This is a diagram showing the relationship between instruction issuance and circulation provided in the embodiments of this application; Figure 5 When the system provided in this application embodiment has or does not have circulating current. V 1 and q 2 The range of values; Figure 6 These are different typical examples provided in the embodiments of this application. V 1 Value q 2 Relationship diagram with K; Figure 7 These are different typical examples provided in the embodiments of this application. q 2 Value V 1 Relationship diagram with K; Figure 8 This is provided by the embodiments of this application. V m and V 1 , q 2 Relationship diagram; Figure 9 The embodiments provided in this application provide that when ( V 1 , q 2 When ) = (0.93124, 0.081271), the grid connection point voltage diagram is shown. Figure 10 The embodiments provided in this application provide that when ( V 1 , q 2 When ) = (0.93124, 0.081271), the reactive power diagram is shown. Figure 11 This is provided in the embodiments of this application ( V 1 , q 2 When ) = (0.939516, 0.0197837), the grid connection point voltage diagram is shown. Figure 12 This is provided in the embodiments of this application ( V 1 ,q 2 When ) = (0.939516, 0.0197837), the reactive power diagram is shown. Figure 13 This is a diagram illustrating the impact of the short-circuit ratio on reactive circulating current, provided in an embodiment of this application. Figure 14 This is a diagram illustrating the impact of line length on reactive power circulation provided in an embodiment of this application. Figure 15 This is a schematic diagram of the structure of a reactive power circulation analysis and control device for a hybrid renewable energy power station based on a grid-connected network, provided in an embodiment of this application. Figure 16 This is a schematic diagram of the structure of an electronic device provided in an embodiment of this application. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the embodiments of this application will be further described in detail below with reference to the accompanying drawings. Here, the illustrative embodiments and descriptions of this application are used to explain this application, but are not intended to limit this application.

[0022] like Figure 1 The diagram shown is a flowchart illustrating a reactive power circulation analysis and control method for a hybrid renewable energy power station based on a grid-connected network, according to an embodiment of this application. The method includes the following steps: Step S101: Construct an equivalent model of a grid-connected hybrid renewable energy power station. In the equivalent model, the grid-connected unit in the renewable energy power station is equivalent to an equivalent grid-connected unit, which is connected to the point of common coupling via a first line reactor. The grid-connected unit in the renewable energy power station is equivalent to an equivalent grid-connected unit, which is connected to the point of common coupling via a second line reactor. The point of common coupling is connected to the power grid via a third line reactor.

[0023] Step S102: Obtain the reactive power of the grid-connected unit and the voltage amplitude of the grid-connected unit based on the equivalent model.

[0024] Step S103: By analyzing the reactive power of the grid-connected unit and the voltage amplitude of the grid-connected unit, the values ​​of the voltage control command for the grid-connected unit and the reactive power control command for the grid-connected unit are limited to ensure that reactive circulating current is suppressed within any given target range of the common coupling voltage.

[0025] The reactive power circulation analysis and control method for grid-connected hybrid renewable energy power plants proposed in this application fills the gap in the current lack of quantitative analysis methods for reactive power circulation in such power plants. It can analyze the relationship between the values ​​of voltage control commands for grid-connected units and reactive power control commands for grid-connected units and reactive power circulation. The analysis results can serve as a reference for the AVC system to issue control commands reasonably when performing voltage control, thereby improving the stability and operating efficiency of the system.

[0026] The steps outlined above in this application are further explained below: Step S101: Construct an equivalent model of a grid-connected hybrid renewable energy power station. In the equivalent model, the grid-connected unit in the renewable energy power station is equivalent to an equivalent grid-connected unit, which is connected to the point of common coupling via a first line reactor. The grid-connected unit in the renewable energy power station is equivalent to an equivalent grid-connected unit, which is connected to the point of common coupling via a second line reactor. The point of common coupling is connected to the power grid via a third line reactor.

[0027] like Figure 2 The diagram shown is a system topology diagram of an equivalent model of a grid-connected hybrid renewable energy power station provided in an embodiment of this application. Figure 2 As can be seen, all grid-connected units in this hybrid renewable energy power station are equivalent to a single equivalent grid-connected unit. This equivalent grid-connected unit operates in PV mode, with active power and voltage control parameters p1 and V1, respectively. It is connected to the Point of Common Coupling (PCC) via line reactance Xt1 (i.e., the first line reactance), and its line current is I1. Furthermore, all grid-connected units in this hybrid renewable energy power station are equivalent to a single equivalent grid-connected unit. This equivalent grid-connected unit operates in PQ mode, with active power and reactive power control parameters p2 and q2, respectively. It is connected to the PCC via line reactance Xt2 (i.e., the second line reactance), and its line current is I2. The active power, voltage, and current at the PCC point are Pm, Vm, and Im, respectively; the PCC point is connected to the grid via line reactance Xb (i.e., the third line reactance).

[0028] In one embodiment of this application, the effects of line resistance and capacitance are ignored for the first, second, and third line reactances. When analyzing reactive circulating current, key factors are typically reactive power distribution, voltage amplitude and phase angle, and the influence of line inductive reactance on current distribution. Removing secondary factors such as resistance and capacitance helps to highlight the dominant role of reactance in reactive circulating current, reduces model complexity, and facilitates the derivation of analytical solutions or rapid numerical simulation.

[0029] Step S102: Obtain the reactive power of grid-connected units and the voltage amplitude of grid-connected units based on the equivalent model. In some embodiments of this application, such as Figure 3 As shown, this step may further include the following sub-steps: Step S1021: Obtain the system active power flow equations from the point of common coupling to the power grid. The system active power flow equations include the first active power of the equivalent grid-type generators, the second active power of the equivalent grid-type generators, the voltage and voltage phase angle of the point of common coupling, and the third line reactance.

[0030] Assumption Figure 2 In the grid voltage The voltage at point PCC is Then the active power flow equation from point PCC to the power grid is as follows (1): (1) in, p 1 It is the first active power of the equivalent grid-type unit. p 2 It is the second active power of the equivalent grid-type unit. V m It is the voltage at the point of common coupling. θ It is the voltage phase angle at the point of common coupling. X b It is the third line reactor.

[0031] Step S1022: Obtain the grid current based on the voltage of the common connection point, the voltage phase angle, and the third line reactance.

[0032] Assuming the grid current I m of d Axial components and q The axis components are respectively I md and I mq ,exist dq In coordinate system: (2) We can calculate from equation (2) that dq The grid current in the coordinate system is: (3) Step S1023: Based on the second active power and the first reactive power measured at the common coupling point by the equivalent grid-type unit, the first branch current of the equivalent grid-type unit is obtained.

[0033] Assume that the first reactive power measured at point PCC for the grid-connected unit branch is q 2mThen, the equivalent first branch current of the grid-type unit can be obtained through the following formula (4) in this step. I 2 : (4) In the dq coordinate system, the current in the first branch... I 2 The d-axis and q-axis components are respectively I 2d and I 2q ,but I 2d and I 2q The calculation is as follows (5): (5) Step S1024: Based on the first reactive power, the first branch current and the second line reactance, obtain the reactive power of the grid-connected unit.

[0034] Specifically, regarding the reactive power of grid-type generator units q 2 It can be obtained through the following formula (6): (6) Step S1025: Based on the second branch current of the equivalent grid-type unit, the first line reactance, the voltage of the common connection point, and the voltage phase angle, the voltage amplitude of the grid-type unit is obtained.

[0035] Assuming the second branch current of the equivalent grid-type unit I 1 The d-axis and q-axis components are respectively I 1d and I 1q Then the dq-axis voltage amplitude of the grid-type unit is: (7) Furthermore, the voltage amplitude of grid-connected units V 1 for: (8) As can be seen from the above, the reactive power of the grid-connected generator unit can be obtained using the known values ​​of various variable parameters. q 2 Voltage amplitude of grid-connected units V 1 .

[0036] As can be seen, step S102 and its sub-steps provide a systematic, quantitative, and repeatable path. This path starts from the point of common coupling and directly obtains the reactive power of the grid-connected units through the relationship between active power flow, branch current, and reactance. q 2 Voltage amplitude of grid-connected units V 1 This approach avoids the need for large-scale hardware modifications and repetitive testing of complex renewable energy power plants, reducing the hardware costs and time investment required for system verification before actual deployment. It provides a clear and executable computational framework and data support for reactive power circulation analysis, control command design, and system stability assessment, making it possible to evaluate and optimize system performance at a lower cost in the early stages of a project.

[0037] In some embodiments of this application, limiting the values ​​of the voltage control command for the grid-connected unit and the reactive power control command for the grid-connected unit in step S103 includes: if the voltage amplitude of the grid-connected unit is a fixed value and does not fall within the range of 0.95pu to 1pu, the reactive power of the grid-connected unit is increased to suppress reactive circulating current.

[0038] In this embodiment, when the voltage amplitude of the grid-connected unit V 1 When the reactive power is a fixed value and not within the target range of 0.95 pu to 1.0 pu, increasing the reactive power of the grid-connected units can be prioritized. q 2 This is to suppress reactive circulating current, thereby improving the voltage stability and circulating current characteristics of the system by adjusting the reactive power distribution without changing the voltage amplitude of the grid-type generator units.

[0039] In some embodiments of this application, limiting the values ​​of the voltage control command for the grid-connected generator unit and the reactive power control command for the grid-connected generator unit in step S103 further includes: if the reactive power of the grid-connected generator unit is less than 0 and is a constant value, suppressing reactive circulating current by gradually reducing the voltage amplitude of the grid-connected generator unit; if the reactive power of the grid-connected generator unit is equal to 0.05pu or 0.1pu, suppressing reactive circulating current by gradually increasing the voltage amplitude of the grid-connected generator unit.

[0040] In this embodiment, two sets of conditional triggering strategies are added in step S103 to trigger the voltage amplitude of grid-connected units under specific reactive power conditions. V 1 Adjustments are made to suppress reactive power circulation. Specifically, this includes control in two scenarios: (1) When the reactive power of the grid-connected unit q 2 When the voltage amplitude is less than 0 and is a constant value, the voltage amplitude of the grid-connected unit is gradually reduced.V 1 This is to suppress reactive power circulation.

[0041] (2) When the reactive power of the grid-connected unit q 2 When the voltage amplitude is equal to 0.05 pu or 0.1 pu, gradually increase the voltage amplitude of the grid-connected unit. V 1 This is to suppress reactive power circulation.

[0042] In this embodiment, by measuring the voltage amplitude of the grid-connected unit V 1 Adjustments can directly affect the voltage distribution and reactive power resource allocation at the point of common coupling, thereby changing the direction and magnitude of reactive power at the point of common coupling between the two ends (grid-connected units and grid-linked units), achieving the goal of suppressing reactive circulating current. This strategy reflects the... V 1 and q 2 Coupling control: Under different reactive power output levels, different methods are adopted. V 1 Adjusting the direction can ensure system stability and robustness of circulating flow control.

[0043] In some embodiments of this application, limiting the values ​​of the voltage control command for the grid-connected generator unit and the reactive power control command for the grid-connected generator unit in step S103 above further includes: when the system short-circuit ratio is lower than a preset threshold, increasing the adjustment range of the voltage control command for the grid-connected generator unit, or adjusting the reference value of the reactive power control command for the grid-connected generator unit, so as to expand the reactive power circulation suppression area.

[0044] By analyzing the reactive power of grid-type generating units under different short-circuit ratios and the presence or absence of reactive circulating current in the system. q 2 Voltage amplitude of grid-connected units V 1 After analyzing the range of values, it can be seen that when the SCR (short-circuit ratio) is low, the system is more prone to reactive power circulation, indicating that reactive power circulation is more likely to occur under weak grid conditions, and more aggressive reactive power suppression strategies are needed to maintain stability.

[0045] Therefore, in scenarios with low short-circuit ratios and increased risk of reactive power circulating current, this embodiment increases the adequacy of the voltage support capability of grid-connected units (by expanding...). V 1 Adjust the range, or adjust q 2 The reference value is used to more effectively suppress reactive circulating current, thereby improving the system's robustness to reactive circulating current.

[0046] The method described above in this application will be further illustrated below with specific simulation results.

[0047] (1) Analysis of factors affecting reactive power circulation.

[0048] Assuming a constant system short-circuit ratio, SCR=4, and the distance between the grid-connected generators and the grid connection point is zero, i.e., the influence of line impedance is ignored. The criterion for reactive power circulating current is defined as whether the reactive power on the line is reversed, i.e., K =q 1 ×q 2 When the value is less than 0, it is considered that reactive power circulation has occurred in the system.

[0049] In a two-node system, the AVC system can issue different V and q commands to grid-connected and grid-linked units to support the grid connection point voltage. Now, assuming the goal is to maintain the grid connection point voltage... Vm Within the range [0.9, 1.1], traverse all possible values. V 1 , q 2 Instructions, such as Figure 4 As shown, this is to analyze the relationship between command issuance and circulation.

[0050] from Figure 4 It can be seen that when K < 0, at this time V 1 and q 2 Improper command issuance may lead to circulation issues. Further analysis is needed. V 1 and q 2 Within a reasonable range of command issuance, determine whether the system exhibits any circulation. V 1 and q 2 The range of values ​​is as follows Figure 5 As shown.

[0051] Depend on Figure 5 It can be known that when ( V 1 , q 2 Circulation will occur when the sample falls into the red area, but will not occur when it falls into the blue area. For analysis... V 1 and q 2 The effects of changes on the generation of circulation, respectively fixing several typical... V 1 value or q 2 We will observe the effect of changes in another parameter on the generation of circulation. We will take different typical values. V1 value, q 2 The relationship between the value and K is as follows: Figure 6 As shown.

[0052] from Figure 6 It can be seen that, V 1 At a certain time, K basically follows q 2 It increases with the increase of, that is, it increases. q 2 It can suppress circulation, but when V 1 When the value is between 0.95 and 1, regardless of q 2 Regardless of the value, circulation will occur.

[0053] Take different typical q 2 The value, the relationship between V1 and K is as follows: Figure 7 As shown.

[0054] from Figure 7 It can be seen that when q 2 When <0, q 2 Certainly, K follows V 1 The increase of [something] decreases, that is, increases. V 1 This may cause circulating current in the system, when q 2 When equal to 0.05 or 0.1, q 2 Certainly, K follows V 1 It increases with the increase of, that is, it increases. V 1 It can suppress circulation. Therefore, increasing V 1 Whether circulation can be suppressed depends on q 2 The value needs to be determined based on different... q 2 Value, Adjustment V 1 Only by changing the direction of the flow can the circulation be suppressed.

[0055] The AVC system issues commands to network-type generating units. V 1 Instructions were issued to grid-connected generating units. q 2 The instructions are to support the voltage at the grid connection point. Analysis shows that the support effect is the same for the same voltage. V mThere can be different ( V 1 , q 2 The instruction set of ). V m and V 1 , q 2 Relationship such as Figure 8 As shown.

[0056] from Figure 8 It can be seen that the corresponding voltage support effect V m There are different ( V 1 , q 2 The instruction set of ) . To verify the correctness of the drawing parameter value range, (0.93124, 0.081271) and (0.939516, 0.0197837) were taken. In the Simulink site model with a hybrid root-mesh network, different ( V 1 , q 2 The instruction value is input into the model.

[0057] when( V 1 , q 2 When ) = (0.93124, 0.081271), V m And the reactive power of the line, such as Figure 9 and Figure 10 As shown.

[0058] when( V 1 , q 2 When ) = (0.939516, 0.0197837), V m And the reactive power of the line, such as Figure 11 and Figure 12 As shown.

[0059] Depend on Figure 9 and Figure 11 It can be seen that at this time V m =0.945, and Figure 8 The theoretical results are consistent. (By...) Figure 10 and Figure 12 It can be seen that when ( V 1 , q 2When () = (0.93124, 0.081271), circulation will occur; when () V 1 , q 2 When ) = (0.939516, 0.0197837), no circulation will occur. Simulation results are consistent with... Figure 5 The theoretical results are consistent, verifying the correctness of the analysis results. Both theoretical and simulation results show that in a grid-connected hybrid system, appropriately issuing voltage commands for grid-connected units and reactive power commands for grid-connected units can suppress reactive power circulation.

[0060] (2) The effect of short-circuit ratio on reactive circulating current.

[0061] Analyze the impact of short-circuit ratio on reactive circulating current. When the system SCR is 3, 4, or 5, is there reactive circulating current in the system? V 1 and q 2 The range of values ​​is as follows Figure 13 As shown, (a)-(c) correspond to SCR=3, 4, and 5 respectively.

[0062] contrast Figure 13 As can be seen from (a) to (c), reactive power circulation is more likely to occur in scenarios with a low system short-circuit ratio, i.e., weak power grids.

[0063] (3) The impact of line length on reactive circulating current.

[0064] Existing research results indicate that grid-connected units are better positioned closer to the grid connection point to provide greater support in the event of a fault.

[0065] The distances to the grid-connected units and grid connection points are set to 0 km, 3 km, and 6 km respectively. Assuming the 35kV line uses LGJ-120 conductor, the inductive reactance per kilometer of conductor is 0.379 Ω according to the common power line impedance table. The impact of line length on reactive power circulation is as follows: Figure 14 As shown, (a)-(c) correspond to 0 km, 3 km, and 6 km, respectively.

[0066] contrast Figure 14 As shown in equations (a) to 11(c), the system exhibits reactive power circulation under different line length scenarios. V 1 and q 2 The range of values ​​is not significantly different, indicating that the line length has a limited impact on reactive circulating current, and the influence of line length can be ignored when adjusting the command.

[0067] like Figure 15The diagram shown is a structural schematic of a reactive power circulation analysis and control device for a hybrid renewable energy power station based on an embodiment of this application. The device includes: The equivalent model construction unit 151 is used to construct an equivalent model of a grid-connected hybrid renewable energy power station. In the equivalent model, the grid-connected unit in the renewable energy power station is equivalent to an equivalent grid-connected unit, which is connected to the point of common coupling through a first line reactor. The grid-connected unit in the renewable energy power station is equivalent to an equivalent grid-connected unit, which is connected to the point of common coupling through a second line reactor. The point of common coupling is connected to the power grid through a third line reactor.

[0068] The power and amplitude acquisition unit 152 is used to acquire the reactive power of the grid-connected unit and the voltage amplitude of the grid-connected unit based on the equivalent model.

[0069] The analysis control unit 153 is used to limit the values ​​of the voltage control command for the grid-connected unit and the reactive power control command for the grid-connected unit by analyzing the reactive power of the grid-connected unit and the voltage amplitude of the grid-connected unit, so as to ensure that reactive circulating current is suppressed within any given target range of the common coupling voltage.

[0070] In some embodiments of this application, the effects of line resistance and capacitance are ignored for the first line reactance, the second line reactance, and the third line reactance.

[0071] In some embodiments of this application, the power and amplitude acquisition unit 152 includes: The power flow equation acquisition module is used to acquire the system active power flow equation from the point of common coupling to the power grid. The system active power flow equation includes the first active power of the equivalent grid-type unit, the second active power of the equivalent grid-type unit, the voltage and voltage phase angle of the point of common coupling, and the third line reactance. A grid current acquisition module is used to obtain the grid current based on the voltage, voltage phase angle, and third line reactance of the common connection point; The branch current acquisition module is used to obtain the first branch current of the equivalent grid unit based on the second active power and the first reactive power measured at the point of common coupling of the equivalent grid unit. The reactive power acquisition module is used to obtain the reactive power of the grid-connected unit based on the first reactive power, the first branch current, and the second line reactance. The voltage amplitude acquisition module is used to obtain the voltage amplitude of the grid-type generator unit based on the second branch current of the equivalent grid-type generator unit, the first line reactance, the voltage of the common connection point, and the voltage phase angle.

[0072] In some embodiments of this application, the analysis and control unit 153 includes: a first control module, used to suppress reactive circulating current by increasing the reactive power of the grid-connected unit when the voltage amplitude of the grid-connected unit is a fixed value and does not fall within the range of 0.95pu to 1pu.

[0073] In some embodiments of this application, the analysis control unit 153 further includes: a second control module, configured to suppress reactive circulating current by gradually reducing the voltage amplitude of the grid-connected unit when the reactive power of the grid-connected unit is less than 0 and is a constant value; and to suppress reactive circulating current by gradually increasing the voltage amplitude of the grid-connected unit when the reactive power of the grid-connected unit is equal to 0.05pu or 0.1pu.

[0074] In some embodiments of this application, the analysis and control unit 153 further includes: a third control module, used to increase the adjustment range of the voltage control command of the grid-connected unit or adjust the reference value of the reactive power control command of the grid-connected unit when the system short-circuit ratio is lower than a preset threshold, so as to expand the reactive power circulating current suppression area.

[0075] As mentioned above, the reactive power circulation analysis and control device for grid-connected hybrid new energy power plants proposed in this application fills the gap in the current lack of quantitative analysis methods for reactive power circulation in grid-connected hybrid new energy power plants. It can analyze the relationship between the values ​​of voltage control commands for grid-connected units and reactive power control commands for grid-connected units and reactive power circulation. The analysis results can serve as a reference for the AVC system to issue control commands reasonably when performing voltage control, thereby improving the stability and operating efficiency of the system.

[0076] Figure 16 This is a schematic diagram of the electronic device provided in the embodiments of this application. Figure 16 The electronic device shown is a general-purpose data processing device, which includes a general-purpose computer hardware structure, including at least a processor 801 and a memory 802. The processor 801 and the memory 802 are connected via a bus 803. The memory 802 is adapted to store one or more instructions or programs executable by the processor 801. These instructions or programs are executed by the processor 801 to implement the steps in the above-described reactive power circulation analysis and control method for grid-connected hybrid renewable energy power plants.

[0077] The processor 801 described above can be a standalone microprocessor or a collection of one or more microprocessors. Thus, the processor 801 executes commands stored in the memory 802, thereby performing the method flow described in the embodiments of this application to process data and control other devices. The bus 803 connects the aforementioned components together, and also connects these components to the display controller 804, the display device, and the input / output (I / O) device 805. The input / output (I / O) device 805 can be a mouse, keyboard, modem, network interface, touch input device, motion-sensing input device, printer, and other devices known in the art. Typically, the input / output (I / O) device 805 is connected to the system via an input / output (I / O) controller 806.

[0078] The memory 802 can store software components, such as an operating system, a communication module, an interaction module, and application programs. Each of the modules and application programs described above corresponds to a set of executable program instructions that perform one or more functions and the methods described in the embodiments of the invention.

[0079] This application also provides a computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the steps of the above-described method for reactive power circulation analysis and control of hybrid renewable energy power plants.

[0080] The reactive power circulation analysis and control method and device for grid-connected hybrid renewable energy power plants proposed in this application fill the gap in the current lack of quantitative analysis methods for reactive power circulation in grid-connected hybrid renewable energy power plants. It can analyze the relationship between the values ​​of voltage control commands for grid-connected units and reactive power control commands for grid-connected units and reactive power circulation. The analysis results can be used as a reference for AVC systems to reasonably issue control commands when performing voltage control, thereby improving the stability and operating efficiency of the system.

[0081] Preferred embodiments of this application have been described above with reference to the accompanying drawings. Many features and advantages of these embodiments are apparent from this detailed description, and therefore the claims are intended to cover all such features and advantages of these embodiments that fall within their true spirit and scope. Furthermore, since many modifications and alterations will readily occur to those skilled in the art, the embodiments of this application are not intended to be limited to the precise structures and operations illustrated and described, but rather to encompass all suitable modifications and equivalents falling within their scope.

[0082] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0083] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0084] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0085] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0086] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of this application. It should be understood that the above descriptions are merely specific embodiments of this application and are not intended to limit the scope of protection of this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A reactive loop analysis and control method for a hybrid new energy station, characterized in that, The method comprises: An equivalent model of the hybrid new energy station is constructed, in which the grid-connected unit in the new energy station is equivalent to an equivalent grid-connected unit connected to the point of common coupling (PCC) through a first line reactance, and the grid-following unit in the new energy station is equivalent to an equivalent grid-following unit connected to the PCC through a second line reactance, and the PCC is connected to the power grid through a third line reactance; The reactive power of the grid-following unit and the voltage amplitude of the grid-connected unit are obtained based on the equivalent model; The values of the voltage control instruction of the grid-connected unit and the reactive power control instruction of the grid-following unit are limited by analyzing the reactive power of the grid-following unit and the voltage amplitude of the grid-connected unit, so as to ensure that the reactive current circulation is suppressed within a target interval of any given PCC voltage.

2. The reactive power circulating current analysis and control method for the hybrid new energy station of the network following type according to claim 1, characterized in that, The first line reactance, the second line reactance and the third line reactance all ignore the influence of line resistance and capacitance.

3. The reactive power circulating current analysis and control method for the hybrid new energy station of the network construction according to claim 1, characterized in that, The method of obtaining the reactive power of the grid-following unit and the voltage amplitude of the grid-connected unit based on the equivalent model comprises: A system active power flow equation from the PCC to the power grid is obtained, which includes the first active power of the equivalent grid-connected unit, the second active power of the equivalent grid-following unit, the voltage and voltage phase angle of the PCC, and the third line reactance; The power grid current is obtained based on the voltage, voltage phase angle and third line reactance of the PCC; The first branch current of the equivalent grid-following unit is obtained based on the second active power and the first reactive power measured at the PCC; The reactive power of the grid-following unit is obtained based on the first reactive power, the first branch current and the second line reactance; The voltage amplitude of the grid-connected unit is obtained based on the second branch current of the equivalent grid-connected unit, the first line reactance, the voltage and voltage phase angle of the PCC.

4. The reactive power circulating current analysis and control method for the hybrid new energy station of the network construction according to claim 1, characterized in that, The limiting of the values of the voltage control instruction of the grid-connected unit and the reactive power control instruction of the grid-following unit comprises: If the voltage amplitude of the grid-connected unit is a constant value and does not belong to the interval of 0.95pu to 1pu, the reactive current circulation is suppressed by increasing the reactive power of the grid-following unit.

5. The reactive power circulating current analysis and control method for the hybrid new energy power station of the network following type according to claim 4, characterized in that, The limiting of the values of the voltage control instruction of the grid-connected unit and the reactive power control instruction of the grid-following unit further comprises: If the reactive power of the grid-following unit is less than 0 and a constant value, the reactive current circulation is suppressed by gradually reducing the voltage amplitude of the grid-connected unit; If the reactive power of the grid-following unit is equal to 0.05pu or 0.1pu, the reactive current circulation is suppressed by gradually increasing the voltage amplitude of the grid-connected unit.

6. The reactive power circulating current analysis and control method for the hybrid new energy power station of the networking type according to claim 5, characterized in that, The limiting of the values of the voltage control instruction of the grid-connected unit and the reactive power control instruction of the grid-following unit further comprises: When the system short-circuit ratio is lower than a preset threshold, the adjustment range of the voltage control instruction of the grid-connected unit is increased, or the reference value of the reactive power control instruction of the grid-following unit is adjusted to expand the reactive current circulation suppression area.

7. A reactive loop analysis and control device for a hybrid new energy station, characterized in that, The device comprises: An equivalent model construction unit is configured to construct an equivalent model of a hybrid grid-connection and follow-grid new energy station, in which grid-connection type units in the new energy station are equivalent to one equivalent grid-connection type unit connected to a point of common coupling (PCC) through a first line reactance, and follow-grid type units in the new energy station are equivalent to one equivalent follow-grid type unit connected to the PCC through a second line reactance, and the PCC is connected to a power grid through a third line reactance; A power and amplitude acquisition unit is configured to acquire reactive power of the follow-grid type units and voltage amplitude of the grid-connection type units based on the equivalent model; An analysis and control unit is configured to limit values of grid-connection type unit voltage control instructions and follow-grid type unit reactive power control instructions by analyzing the reactive power of the follow-grid type units and the voltage amplitude of the grid-connection type units, so as to ensure that reactive power circulation is suppressed within a target interval of any given PCC voltage.

8. An electronic device comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, characterized in that, The processor executes the computer program to implement the steps of the method of any one of claims 1 to 6.

9. A computer-readable storage medium having stored thereon a computer program, characterized in that, The computer program is executed by the processor to implement the steps of the method of any one of claims 1 to 6.

10. A computer program product comprising computer programs / instructions, characterized in that, The computer program / instructions are executed by the processor to implement the steps of the method of any one of claims 1 to 6.

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