Single new energy grid-connected system strength determination method and device, equipment and storage medium

Abstract

The application discloses a single new energy grid-connected system strength determination method and device, equipment and a storage medium, the method comprises the following steps: constructing a transfer function matrix of a single new energy grid-connected system containing a static var generator according to power grid operating condition parameters, and establishing a closed-loop characteristic equation reflecting the stability of the single new energy grid-connected system according to the transfer function matrix; the single new energy grid-connected system is equivalent to a single feed-in system according to the dynamic characteristics of the power grid operating condition parameters, and the short-circuit ratio and the critical short-circuit ratio are calculated according to the single feed-in system processing power grid operating condition parameters, the dynamic characteristics of the power grid operating condition parameters can reflect the change of the power grid operating condition; the grid strength of the single new energy grid-connected system under the preset operating condition is judged according to the short-circuit ratio and the critical short-circuit ratio, and the small disturbance stability margin is obtained. The application can accurately analyze the grid strength and small disturbance stability margin of the single new energy equipment grid-connected system containing an SVG under the preset operating condition, and obtain the stability result of the system.

Description

Technical Field

[0001] This invention relates to the field of new energy grid-connected system technology, and in particular to a method, apparatus, equipment and storage medium for determining the intensity of a single new energy grid-connected system. Background Technology

[0002] Grid-connected renewable energy systems are one of the key technologies for achieving efficient and stable operation of renewable energy power generation systems alongside traditional energy power generation systems. With the development of renewable energy power generation technologies, the proportion of renewable energy equipment such as photovoltaic and wind power in the power grid is gradually increasing.

[0003] Currently, renewable energy equipment primarily uses grid-connected converters synchronized with phase-locked loops (PLLs) as their grid interface. These PLLs provide weak voltage support to the grid. With a high proportion of renewable energy, the low short-circuit ratio and weak grid characteristics of the power grid become more prominent, leading to a gradual increase in the interaction between renewable energy equipment and the grid, which can easily cause broadband oscillations. On the other hand, renewable energy power plants typically employ a certain proportion of static var generators (SVGs) to maintain voltage stability. However, SVGs interact with renewable energy equipment, and in severe cases, this can even exacerbate the broadband oscillations caused by the renewable energy equipment.

[0004] Existing technologies can assess the small-disturbance stability margin of grid-connected systems with SVG (Static Var Generator) under rated operating conditions and the effect of SVG on system stability. However, due to factors such as weather, the output of new energy equipment fluctuates, and the system typically operates under non-rated conditions. How changes in operating conditions affect the interaction between SVG and new energy equipment, and how they affect the small-disturbance stability of the system, remains a challenge. Summary of the Invention

[0005] The purpose of this invention is to provide a method, apparatus, equipment, and storage medium for determining the strength of a single new energy grid-connected system, in order to solve the technical problem that existing technologies cannot accurately analyze the stability of a single new energy grid-connected system containing SVG under non-rated operating conditions.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] Option 1, the method for determining the intensity of a single new energy grid-connected system, includes:

[0008] Based on the grid operating condition parameters, a transfer function matrix of a single renewable energy grid-connected system containing a static var generator is constructed, and a closed-loop characteristic equation reflecting the stability of the single renewable energy grid-connected system is established based on the transfer function matrix.

[0009] Based on the dynamic characteristics of the power grid operating condition parameters, the single new energy grid-connected system is equivalent to a single feed-in system. The short-circuit ratio and critical short-circuit ratio are calculated by processing the power grid operating condition parameters according to the single feed-in system. The dynamic characteristics of the power grid operating condition parameters can reflect the changes in the power grid operating conditions.

[0010] The grid strength of the single new energy grid-connected system under the preset operating conditions is determined based on the short-circuit ratio and the critical short-circuit ratio, and the small disturbance stability margin is obtained.

[0011] Optionally, the single new energy grid-connected system includes a network side and an equipment side, and the transfer function matrix includes a first transfer function matrix on the network side and a second transfer function matrix on the equipment side.

[0012] Optionally, the device side includes SVG and new energy devices, and the first transfer function matrix of the network side is:

[0013] Y net (s)=Bγ(s);

[0014]

[0015]

[0016] Among them, Y net γ(s) is the first transfer function matrix on the network side, B is the admittance matrix on the network side, γ(s) is the coefficient matrix of the admittance matrix on the network side, ω0 is the synchronization angular frequency of the single new energy grid-connected system, X1 is the equivalent reactance between the new energy equipment and the SVG, X g Let S be the equivalent reactance between the SVG and the infinite power grid, and let S be the Laplace operator.

[0017] Optionally, the second transfer function matrix on the device side is:

[0018]

[0019] Among them, Y G (s) is the second transfer function matrix on the device side, Y CBR (s) is the admittance matrix of the new energy equipment, Y SVG (s) is the admittance matrix of SVG, S Bs Y is the rated capacity of the SVG; CBR (s)=P e Y CBR0 (s), P e =U0I d0 =I d0 Y CBR0 (s) is the admittance matrix normalized to its own capacity under rated operating conditions, P eU0 represents the output power of the new energy equipment, and U0 represents the grid connection node voltage of the new energy equipment; d0 This refers to the d-axis output current of new energy equipment.

[0020] Optionally, the closed-loop characteristic equation is:

[0021]

[0022] Among them, Y CBR0 (s) is the admittance matrix normalized to its own capacity under rated operating conditions, P e For the output power of new energy equipment, Y SVG (s) is the admittance matrix of SVG, S Bs B is the rated capacity of the SVG; S is the admittance matrix on the network side; and S is the Laplace operator.

[0023] Optionally, the closed-loop characteristic equation of the single-feed system is:

[0024] det{[Y CBR0 [(s)+Δ(s)]γ -1 (s)+SCR·I}=0;

[0025]

[0026]

[0027] Among them, Y CBR0 γ(s) is the admittance matrix normalized to its own capacity under rated operating conditions, Δ(s) is the impedance admittance matrix of the SVG dynamic characteristics, and γ(s) is the coefficient matrix of the network-side admittance matrix. -1 (s) is the inverse matrix of γ(s); p1 is the influence factor of SVG on the stability of the system under small disturbances; S Bs For the rated capacity of the SVG, Y SVG (s) is the admittance matrix of the SVG; SCR is the short-circuit ratio of a single renewable energy grid-connected system without the SVG; L1 is the inductance between the SVG and the renewable energy equipment, L g I represents the grid-connected inductance on the equipment side, and I represents the identity matrix.

[0028] Optionally, when a single-energy grid-connected system is in a critical stable state, the critical short-circuit ratio is:

[0029] CSCR = arg{det{[Y CBR (s c )+Δ(s c )]γ -1 (s c )+SCR·I}=0};

[0030] Where CSCR is the critical short-circuit ratio, s c =jω c It is the dominant eigenvalue of the equivalent system on the imaginary axis of the complex plane; Y CBR (s c ) is the admittance matrix of a single-feed system when the short-circuit ratio equals the critical short-circuit ratio; Δ(s c ω is the impedance admittance matrix of the SVG dynamic characteristics when the short-circuit ratio of the single-infeed system is equal to the critical short-circuit ratio; c γ is the oscillation frequency, and γ(s) is the coefficient matrix of the network-side admittance matrix. -1 (s) is the inverse matrix of γ(s); SCR is the short-circuit ratio of a single new energy grid-connected system without SVG; I is the identity matrix.

[0031] Option 2, a grid intensity determination device for a single renewable energy grid-connected system including SVG, comprising:

[0032] The characteristic equation construction module is used to construct the transfer function matrix of a single renewable energy grid-connected system containing a static var generator based on the grid operating condition parameters, and to establish a closed-loop characteristic equation reflecting the stability of the single renewable energy grid-connected system based on the transfer function matrix.

[0033] The short-circuit ratio calculation module is used to convert the single new energy grid-connected system into a single feed-in system based on the dynamic characteristics of the grid operating condition parameters, and to calculate the short-circuit ratio and critical short-circuit ratio based on the grid operating condition parameters processed by the single feed-in system. The dynamic characteristics of the grid operating condition parameters can reflect the changes in the grid operating condition.

[0034] The strength judgment module is used to determine the grid strength of the single new energy grid-connected system under preset operating conditions based on the short-circuit ratio and the critical short-circuit ratio, and to obtain the small disturbance stability margin.

[0035] Option 3: A computer device including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps of Option 1.

[0036] Option 4: A computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of Option 1.

[0037] This invention provides a method, apparatus, device, and storage medium for determining the strength of a single renewable energy grid-connected system. The method includes: constructing a transfer function matrix of the single renewable energy grid-connected system containing a static var generator based on grid operating condition parameters; establishing a closed-loop characteristic equation reflecting the stability of the single renewable energy grid-connected system based on the transfer function matrix; equipping the single renewable energy grid-connected system as a single-infeed system based on the dynamic characteristics of the grid operating condition parameters; calculating the short-circuit ratio and critical short-circuit ratio based on the grid operating condition parameters processed by the single-infeed system, wherein the dynamic characteristics of the grid operating condition parameters reflect changes in grid operating conditions; determining the grid strength of the single renewable energy grid-connected system under preset operating conditions based on the short-circuit ratio and the critical short-circuit ratio, and obtaining a small-disturbance stability margin.

[0038] In view of this, the beneficial effects of this invention are:

[0039] This invention considers changes in grid operating conditions, constructs the transfer function matrix of a single renewable energy grid-connected system containing a static var generator (SVG), and further constructs the closed-loop characteristic equation of the system. The single renewable energy grid-connected system is equivalent to a single-infeed system, and the short-circuit ratio and critical short-circuit ratio are obtained using the single-infeed system processing parameters. Based on the short-circuit ratio analysis method, it reveals how changes in grid operating conditions affect the interaction between the SVG and renewable energy equipment, and how operating conditions affect the small-disturbance stability of the system. It also reveals the influence of the SVG on the small-disturbance stability of the system under complex operating conditions. This invention can accurately analyze the grid strength and small-disturbance stability margin of a single renewable energy equipment grid-connected system containing an SVG under preset operating conditions, obtaining the system's stability results. Attached Figure Description

[0040] Figure 1 This is a flowchart illustrating an embodiment of the method of the present invention;

[0041] Figure 2 This is a topology diagram of the original model of a single new energy grid-connected system containing SVG in the method of this invention;

[0042] Figure 3 This is a schematic diagram of an equivalent system according to an embodiment of the method of the present invention;

[0043] Figure 4 This is a schematic diagram of a single new energy grid-connected system containing SVG, used in a specific simulation verification of the method of this invention. Figure 1 ;

[0044] Figure 5 This is a schematic diagram of a single new energy grid-connected system containing SVG, used in a specific simulation verification of the method of this invention. Figure 2 ;

[0045] Figure 6This is a schematic diagram of the eigenvalue loci of the original system and the equivalent system in a numerical example of the implementation of the method of the present invention. Figure 1 ;

[0046] Figure 7 This is a schematic diagram of the eigenvalue loci of the original system and the equivalent system in a numerical example of the implementation of the method of the present invention. Figure 2 ;

[0047] Figure 8 This is a schematic diagram of the structure of an embodiment of the device of the present invention. Detailed Implementation

[0048] This invention provides a method, apparatus, device, and storage medium for determining the strength of a single new energy grid-connected system, in order to solve the technical problem that existing technologies cannot accurately analyze the stability of a single new energy grid-connected system containing SVG under non-rated operating conditions.

[0049] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

[0050] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0051] One of the fundamental issues of widespread concern regarding renewable energy grid-connected systems is the complex oscillation phenomenon that occurs when power electronic equipment is connected to an AC system with low grid strength. As grid strength decreases, the system stability margin (specifically referring to small-disturbance stability in this invention) declines. Therefore, the newly revised "Guidelines for the Safety and Stability of Power Systems" stipulates that renewable energy access systems must meet certain grid strength requirements.

[0052] The application scenario of this invention is a single new energy grid-connected system containing SVG, especially for scenarios where the reactive current of SVG varies due to the variable output power of new energy equipment and the infinite grid voltage fluctuation.

[0053] Firstly, please refer to Figure 1 Methods for determining the intensity of a single new energy grid-connected system include:

[0054] S100: Construct the transfer function matrix of a single new energy grid-connected system containing a static var generator based on the grid operating condition parameters, and establish a closed-loop characteristic equation reflecting the stability of the single new energy grid-connected system based on the transfer function matrix;

[0055] S200: Based on the dynamic characteristics of the power grid operating condition parameters, the single new energy grid-connected system is equivalent to a single feed-in system. The short-circuit ratio and critical short-circuit ratio are calculated by processing the power grid operating condition parameters according to the single feed-in system. The dynamic characteristics of the power grid operating condition parameters can reflect the changes in the power grid operating condition.

[0056] S300: Determine the grid strength of the single new energy grid-connected system containing SVG under the preset operating conditions based on the short-circuit ratio and the critical short-circuit ratio, and obtain the small disturbance stability margin.

[0057] In this embodiment of the invention, "new energy" refers to new energy equipment.

[0058] In step S100, firstly, the transfer function matrix of a single new energy grid-connected system containing a static var generator is constructed based on the grid operating condition parameters.

[0059] In one embodiment, a single renewable energy grid-connected system containing an SVG may include a network side and an equipment side. The equipment side includes the SVG and renewable energy equipment. The grid operating parameters may include: the active power output of the renewable energy equipment, the reactive power output of the SVG, the inductance between the SVG and the renewable energy equipment, the grid-connected inductance on the equipment side, the parameters of the renewable energy equipment (such as DC capacitor, filter inductance, filter capacitor, etc.), the parameters of the SVG (such as DC capacitor, filter inductance, etc.), the control method of the renewable energy equipment (such as constant DC voltage control, constant active power control), the control method of the SVG (such as constant AC voltage control, constant reactive power control), and other parameters.

[0060] When constructing the transfer function matrix of a single renewable energy grid-connected system containing SVG, the original grid topology remains unchanged. Assuming a grid contains N nodes, one node can be selected to connect a static var generator (SVM), a renewable energy device, or both. This node can have at most one SVM and at most one renewable energy device connected, thus obtaining a single renewable energy grid-connected system containing SVG.

[0061] The transfer function matrix represents the transfer relationship between the input vector and the state vector, and between the input vector and the output vector in a linear time-invariant control system. It is used for the analysis and research of multi-input multi-output control systems. Since a single-energy grid-connected system containing SVG can include both the network side and the equipment side, the transfer function matrix of such a system can include the first transfer function matrix on the network side (denoted by Y). net (s) and the second transfer function matrix on the device side (denoted by Y) G (s) represents).

[0062] Figure 2 in,I, U and θ represent the magnitude and phase angle of the injected current at the new energy equipment node, respectively; U and θ represent the magnitude and phase angle of the voltage at the new energy equipment node, respectively; I s , These represent the magnitude and phase angle of the injected current at the SVG node, respectively; U s and θ s These represent the voltage magnitude and phase angle at the SVG node, respectively; E and θ. E These represent the voltage magnitude and phase angle at the infinite node, respectively; P e For the output power of new energy equipment; S Bs C is the rated capacity of the SVG. f For filtering capacitors in new energy equipment; X1 and X g These are the equivalent reactances between new energy equipment and SVG, and between SVG and the infinite power grid, respectively.

[0063] Specifically, in one embodiment, the first transfer function matrix on the network side can be:

[0064] Y net (s)=Bγ(s); (1)

[0065]

[0066]

[0067] Among them, Y net γ(s) is the first transfer function matrix on the network side, B is the admittance matrix on the network side, γ(s) is the coefficient matrix of the admittance matrix on the network side, ω0 is the synchronization angular frequency of the single new energy grid-connected system, X1 is the equivalent reactance between the new energy equipment and the SVG, X g Let S be the equivalent reactance between the SVG and the infinite power grid, and let S be the Laplace operator.

[0068] It should be noted that, in one embodiment, the equipment side may include SVG equipment and new energy equipment, wherein the SVG mainly injects reactive power into the grid, and the new energy equipment mainly injects active power into the grid.

[0069] In one embodiment, the second transfer function matrix on the device side can be represented by equation (4):

[0070]

[0071] Among them, Y G (s) is the second transfer function matrix on the device side, Y CBR (s) is the admittance matrix of the new energy equipment, Y SVG (s) is the admittance matrix of SVG, S Bs This is the rated capacity of the SVG.

[0072] Understandably, Y CBR (s) is the admittance transfer function matrix of the new energy equipment in the xy coordinate system, Y SVG (s) is the admittance transfer function matrix of SVG in the xy coordinate system.

[0073] Under different power grid operating conditions, since SVG mainly injects reactive power into the power grid and provides reactive power compensation, the terminal voltage of renewable energy equipment can be maintained at approximately 1 p.u (per unit). Therefore, the admittance transfer function matrix Y of renewable energy equipment can be... CBR (s) can be rewritten as equation (5):

[0074] Y CBR (s)=P e Y CBR0 (s), P e =U0I d0 =I d0 (5)

[0075] Among them, Y CBR0 (s) is the admittance matrix normalized to its own capacity under rated operating conditions, P e U0 represents the output power of the renewable energy (CBR) equipment, and U0 represents the grid connection voltage of the renewable energy equipment. d0 This refers to the d-axis output current of new energy equipment.

[0076] After constructing the transfer function matrix, a closed-loop characteristic equation reflecting the stability of a single new energy grid-connected system containing SVG is established based on the transfer function matrix, as shown in equation (6):

[0077]

[0078] Among them, Y CBR0(s) is the admittance matrix normalized to its own capacity under rated operating conditions, P e Y represents the output power of the CBR device. SVG (s) is the admittance matrix of SVG, S Bs B is the rated capacity of the SVG; S is the admittance matrix on the network side; and S is the Laplace operator.

[0079] In step S200, the single new energy grid-connected system is equivalent to a single feed-in system based on the dynamic characteristics of the grid operating condition parameters. The short-circuit ratio and critical short-circuit ratio are calculated based on the grid operating condition parameters processed by the single feed-in system. The dynamic characteristics of the grid operating condition parameters can reflect the changes in the grid operating condition.

[0080] In this embodiment, the Static Var Generator (SVG) and the renewable energy equipment are combined into an equivalent device. The single renewable energy grid-connected system containing the SVG has only one equivalent device. Considering changes in grid operating conditions, an equivalent system to a single-infeed system is constructed. Under different operating conditions, this single-infeed system can be used to characterize the small-disturbance stability of the single renewable energy grid-connected system containing the SVG.

[0081] The dynamic characteristics of power grid operating condition parameters reflect changes in power grid operating conditions. These dynamic characteristics can include the dynamic characteristics of SVG and changes in the output power of new energy equipment. The dynamic characteristics of SVG can include its control structure, control parameters, and output reactive current. The control structure of SVG can adopt constant AC voltage control or constant reactive power control.

[0082] It should be noted that changes in the output power of new energy equipment have no impact on the dynamics of the network lines.

[0083] Figure 3 In this context, IBR stands for inverter-based resources; S B1 SBs and SBs are the rated capacities of the new energy equipment and SVG, respectively; p1 is the capacity conversion factor of SVG, and its specific expression is given by reference to formula (8).

[0084] In one embodiment, considering changes in operating conditions, the grid-connected system with a single new energy source containing SVG is equivalent to a single feed-in system. This single feed-in system is an equivalent system characterizing the small-disturbance stability of the grid-connected system with SVG under operating conditions. The closed-loop characteristic equation of the single feed-in system can be expressed by equations (7) to (9):

[0085] det{[Y CBR0 [(s)+Δ(s)]γ -1 (s)+SCR·I}=0; (7)

[0086]

[0087]

[0088] Among them, Y CBR0 γ(s) is the admittance matrix normalized to its own capacity under rated operating conditions, Δ(s) is the impedance admittance matrix of the SVG dynamic characteristics, and γ(s) is the coefficient matrix of the network-side admittance matrix. -1 (s) is the inverse matrix of γ(s); p1 is the influence factor of SVG on the stability of the system under small disturbances; S Bs For the rated capacity of the SVG, Y SVG (s) is the admittance matrix of the SVG; SCR is the short-circuit ratio of a single renewable energy grid-connected system without the SVG; L1 is the inductance between the SVG and the renewable energy equipment, L g I represents the grid-connected inductance on the equipment side, and I represents the identity matrix.

[0089] The short-circuit ratio (SCR) is one of the important indicators for analyzing the grid strength and stability margin of power electronic equipment (DC, wind turbines, photovoltaics, etc.). For single-infeed systems, the SCR is simple to calculate and has a clear physical meaning, providing a convenient and intuitive method for stability analysis of renewable energy grid-connected systems. The critical short-circuit ratio (CSCR) is the short-circuit ratio corresponding to the critical stable state of the system.

[0090] By comparing the current short-circuit ratio of the system with its critical short-circuit ratio, the operating status of the system can be determined and the voltage support strength of the system can be evaluated. This helps to control the impact of new energy grid connection and is therefore of great significance to ensuring the safe and stable operation of the new energy grid connection system.

[0091] In one embodiment, when a single-energy grid-connected system is in a critical stable state, the critical short circuit is as shown in equation (10):

[0092] CSCR = arg{det{[Y CBR (s c )+Δ(s c )]γ -1 (s c )+SCR·I}=0}; (10)

[0093] Where CSCR is the critical short-circuit ratio, s c =jω c It is the dominant eigenvalue on the imaginary axis of the complex plane of the equivalent system; Y CBR (s c ) is the admittance matrix of a single-feed system when the short-circuit ratio equals the critical short-circuit ratio; Δ(s cω is the impedance admittance matrix of the SVG dynamic characteristics when the short-circuit ratio of the single-infeed system is equal to the critical short-circuit ratio; c γ is the oscillation frequency, and γ(s) is the coefficient matrix of the network-side admittance matrix. 1 (s) is the inverse matrix of γ(s); SCR is the short-circuit ratio of a single new energy grid-connected system without SVG; I is the identity matrix.

[0094] It should be noted that when a single new energy grid-connected system is in a critical stable state, the short-circuit ratio (SCR) and the critical short-circuit ratio (CSCR) are calculated to be the same.

[0095] In step S300, the grid strength of the single new energy grid-connected system under the preset operating conditions is determined based on the short-circuit ratio and the critical short-circuit ratio, and the small disturbance stability margin is obtained.

[0096] The short-circuit ratio and critical short-circuit ratio are calculated based on the grid operating parameters of the single-infeed system. The small-disturbance stability margin of the single renewable energy grid-connected system containing SVG is determined by the difference between the short-circuit ratio and the critical short-circuit ratio under the preset operating conditions. It should be noted that the preset operating conditions are non-rated operating conditions.

[0097] Specifically, for a grid-connected system with a single new energy source containing a Static Var Generator (SVG), there exists a Short-Circuit Ratio (CSCR) that reflects the system's critical stability. The difference between the SCR and CSCR reflects the system's small-disturbance stability margin: a difference greater than zero indicates system stability, while a difference less than zero indicates system instability. Furthermore, the larger the difference, the better the system's small-disturbance stability.

[0098] In one embodiment, the difference between the short-circuit ratio (SCR) and the critical short-circuit ratio (CSCR) can be used as the grid strength for the following determination:

[0099] When the grid strength SCR-CSCR is greater than zero, the single-infeed system is stable under small disturbances.

[0100] When the grid strength SCR-CSCR is less than zero, the single-infeed system is unstable under small disturbances.

[0101] In this embodiment, based on the short-circuit ratio analysis method, the influence of SVG on the stability of the system under complex operating conditions is revealed as follows:

[0102] (1) The access of SVG does not change the SCR of the single new energy grid-connected system, but only affects the CSCR of the system. In addition, how SVG affects CSCR (increases or decreases) is mainly related to the dynamic characteristics of SVG. The dynamic characteristics of SVG may include: SVG control structure, control parameters and output reactive current Iqs, etc. The control structure of SVG can adopt constant AC voltage control or constant reactive power control.

[0103] It is understandable that connecting SVG to a single renewable energy grid-connected system, while not changing the system's SCR, will affect the CSCR. Since the grid strength of the system is the difference between the SCR and the CSCR, the connection of SVG will affect the grid strength of the system.

[0104] (2) p1 reflects the relative magnitude of the impact of SVG on system stability. The larger p1 is, the greater the impact of SVG on system stability; the smaller p1 is, the smaller the impact of SVG on system stability. For example, if SVG access increases the CSCR of the system, the larger p1 is, the greater the increase in CSCR by SVG; the smaller p1 is, the smaller the increase in CSCR by SVG.

[0105] (3) Active power output P of new energy equipment e Changes in P affect both SCR and CSCR. Specifically, as P... e As the value decreases, the SCR increases, and p1 increases (i.e., the influence of SVG on CSCR increases).

[0106] Specifically, in the first case: assuming that SVG access reduces CSCR, then as P... e As the SCR decreases, the CSCR increases while the SCR decreases, thus increasing the difference between the SCR and CSCR, SCR-CSCR. In this case, the small disturbance stability margin of the system increases.

[0107] The second scenario: Assuming SVG access increases CSCR, then with P... e As the SCR decreases, both the SCR and CSCR increase simultaneously. Therefore, the difference between the SCR and CSCR, SCR-CSCR, may increase or decrease, and the change in the small disturbance stability margin of the system is unclear.

[0108] The method for determining the strength of a single renewable energy grid-connected system provided in this invention considers changes in grid operating conditions, constructs the transfer function matrix of the single renewable energy grid-connected system including a static var generator (SVG), and further constructs the closed-loop characteristic equation of the system. The single renewable energy grid-connected system is equivalent to a single-infeed system, and the short-circuit ratio and critical short-circuit ratio are obtained using the single-infeed system processing parameters. Based on the short-circuit ratio analysis method, it reveals how changes in grid operating conditions affect the interaction between the SVG and renewable energy equipment, and how operating conditions affect the small-disturbance stability of the system. It also reveals the influence of SVG on the small-disturbance stability of the system under complex operating conditions. This invention can accurately analyze the grid strength and small-disturbance stability margin of a single renewable energy equipment grid-connected system including SVG under preset operating conditions, and obtain the system stability results.

[0109] The following are specific embodiments of the method of the present invention:

[0110] Build a grid-connected system with a single renewable energy device and an SVG in Matlab / Simulink software. The renewable energy device is configured with a capacity of 1 p.u., and the SVG capacity is configured with a capacity of 0.4 p.u. Figure 2 As shown, the line inductance L1 is 0.06 pu, and the line inductance L... g The value is 0.6 pu; the control parameters for new energy equipment and SVG are shown in Tables 1 and 2; two typical control methods are considered for new energy equipment: constant DC voltage control and constant active power control, while only constant AC voltage control is considered for SVG.

[0111] It should be noted that since the analysis results obtained when SVG adopts constant reactive power control are similar to those under constant AC voltage control, the analysis results of SVG adopting constant AC voltage control are mainly given in the specific example analysis.

[0112] Table 1 shows the parameter values ​​of the new energy equipment in the simulation verification of the embodiment, and Table 2 shows the parameter values ​​of the SVG equipment in the simulation verification of the embodiment, as shown below:

[0113] Table 1

[0114]

[0115]

[0116] Table 2

[0117] <![CDATA[Filter inductor L fs / pu]]> 0.1 <![CDATA[DC voltage outer loop H dcs (s) proportional and integral parameters]]> 0.6,8 <![CDATA[AC voltage outer loop H acs (s) proportional and integral parameters]]> 0.6,8 <![CDATA[Inner current loop H is (s) proportional and integral parameters]]> 0.6,12 <![CDATA[Phase-locked loop H PLLs (s) proportional and integral parameters]]> 40,2400 <![CDATA[Voltage feedforward G FFs (s) filtering time constant]]> 0.01 <![CDATA[DC voltage reference value U dcrefs / pu]]> 1

[0118] Figures 4 to 7 The dominant characteristic root loci of a single renewable energy grid-connected system and its equivalent system with SVG are given when the active power output of renewable energy changes from 0.5 pu to 1.0 pu, and the corresponding system SCR changes from 3.03 to 1.52. Figure 4 and Figure 5 In this context, SVG equipment uses constant AC voltage control, while new energy equipment considers two control structures: Figure 4 In China, new energy equipment uses constant DC voltage control; Figure 5 In China, new energy equipment adopts constant active power control; Figure 6 and Figure 7 In this context, SVG equipment employs constant reactive power control, while new energy equipment considers two control structures: Figure 6 Zhongxin Energy's equipment adopts constant DC voltage control; Figure 7 In China, new energy equipment adopts constant active power control.

[0119] from Figures 4 to 7As can be seen, the dominant eigenvalue locus of the new energy grid-connected system containing SVG is approximately consistent with that of the equivalent system. This indicates that, under non-rated operating conditions, the established equivalent system (single-feed system) can approximately represent the small-disturbance stability of the new energy grid-connected system containing SVG.

[0120] In summary, frequency domain eigenvalue analysis demonstrates that the method for obtaining grid strength of a single renewable energy grid-connected system containing SVG under complex operating conditions is effective.

[0121] Therefore, the method of the present invention can accurately analyze the stability (grid strength) and small disturbance stability margin of a grid-connected system with SVG under operating conditions, and has outstanding technical effects.

[0122] Please see Figure 8 The present invention also provides an embodiment of a device for determining the intensity of a single new energy grid-connected system, comprising:

[0123] The characteristic equation construction module 11 is used to consider the changes in grid operating conditions, construct the transfer function matrix of a single new energy grid-connected system containing a static var generator, and establish a closed-loop characteristic equation reflecting the stability of the single new energy grid-connected system based on the transfer function matrix.

[0124] The short-circuit ratio calculation module 22 is used to consider changes in grid operating conditions, to convert the single new energy grid-connected system into a single feeder system, and to calculate the short-circuit ratio and critical short-circuit ratio based on the parameters of the single feeder system and the single new energy grid-connected system.

[0125] The strength judgment module 33 is used to judge the grid strength of the single new energy grid-connected system under the preset operating conditions based on the short-circuit ratio and the critical short-circuit ratio, and to obtain the small disturbance stability margin.

[0126] The present invention also provides an embodiment of a computer device, including a memory and a processor, wherein the memory stores a computer program, characterized in that the processor executes the computer program to implement the steps of a method for determining the intensity of a single new energy grid-connected system.

[0127] The present invention also provides an embodiment of a computer-readable storage medium having a computer program stored thereon, characterized in that, when the computer program is executed by a processor, it implements the steps of a method for determining the strength of a single new energy grid-connected system.

[0128] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0129] In the embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces, indirect coupling or communication connection between apparatuses or units, and may be electrical, mechanical, or other forms.

[0130] The units described as separate components may or may not be physically separate. The components shown as units 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 units can be selected to achieve the purpose of this embodiment according to actual needs.

[0131] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0132] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0133] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention 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 of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for determining the intensity of a single new energy grid-connected system, characterized in that, include: Based on the grid operating condition parameters, a transfer function matrix of a single renewable energy grid-connected system containing a static var generator is constructed, and a closed-loop characteristic equation reflecting the stability of the single renewable energy grid-connected system is established based on the transfer function matrix. Based on the dynamic characteristics of the power grid operating condition parameters, the single new energy grid-connected system is equivalent to a single feed-in system. The short-circuit ratio and critical short-circuit ratio are calculated by processing the power grid operating condition parameters according to the single feed-in system. The dynamic characteristics of the power grid operating condition parameters can reflect the changes in the power grid operating conditions. The grid strength of the single new energy grid-connected system under the preset operating conditions is determined based on the short-circuit ratio and the critical short-circuit ratio, and the small disturbance stability margin is obtained. The single new energy grid-connected system includes a network side and an equipment side, and the transfer function matrix includes a first transfer function matrix on the network side and a second transfer function matrix on the equipment side. The second transfer function matrix on the device side is: ； in, This is the second transfer function matrix on the device side. For the admittance matrix of new energy equipment, Let be the admittance matrix of SVG. This refers to the rated capacity of the SVG; , , It is the admittance matrix normalized to its own capacity under rated operating conditions. For the output power of new energy equipment, The voltage at the grid connection point for new energy equipment; For the d-axis output current of new energy equipment; Based on the transfer function matrix, a closed-loop characteristic equation reflecting the stability of a single renewable energy grid-connected system containing SVG is established. The closed-loop characteristic equation is as follows: ； in, It is the admittance matrix normalized to its own capacity under rated operating conditions. For the output power of new energy equipment, Let be the admittance matrix of SVG. B is the rated capacity of the SVG; S is the admittance matrix on the network side; and S is the Laplace operator. A single renewable energy grid-connected system containing SVG is equivalent to a single feed-in system, and the closed-loop characteristic equation of the single feed-in system is: ； ； ； in, It is the admittance matrix normalized to its own capacity under rated operating conditions. The impedance-admittance matrix is ​​the dynamic characteristic of the SVG. The coefficient matrix of the network-side admittance matrix. for The inverse matrix; The influence factor of SVG on the stability of the system under small disturbances; For the rated capacity of the SVG, is the admittance matrix of SVG; SCR is the short-circuit ratio of a single renewable energy grid-connected system without SVG; For the inductance between SVG and new energy equipment, For the grid-connected inductor on the equipment side, It is an identity matrix.

2. The method for determining the intensity of a single new energy grid-connected system according to claim 1, characterized in that, The device side includes SVG and new energy devices, and the first transfer function matrix of the network side is: ； ； ； in, Let B be the first transfer function matrix on the network side, and let B be the admittance matrix on the network side. The coefficient matrix of the network-side admittance matrix. The synchronous angular frequency of a single new energy grid-connected system. The equivalent reactance between the new energy equipment and the SVG. Let S be the equivalent reactance between the SVG and the infinite power grid, and let S be the Laplace operator.

3. The method for determining the intensity of a single new energy grid-connected system according to claim 1, characterized in that, When the single-new energy grid-connected system is in a critical stable state, the critical short-circuit ratio is: ； in, The critical short-circuit ratio, These are the dominant eigenvalues ​​of the equivalent system on the imaginary axis of the complex plane; The admittance matrix of a single-feed system when the short-circuit ratio is equal to the critical short-circuit ratio; The impedance admittance matrix of the SVG dynamic characteristics when the short-circuit ratio of the single-feed system is equal to the critical short-circuit ratio; It is the oscillation frequency. The coefficient matrix of the network-side admittance matrix. for The inverse matrix; SCR is the short-circuit ratio of a single new energy grid-connected system without SVG; I is the identity matrix.

4. A device for determining the intensity of a single new energy grid-connected system, characterized in that, include: feature The equation construction module is used to construct the transfer function matrix of a single renewable energy grid-connected system containing a static var generator based on the grid operating condition parameters, and to establish a closed-loop characteristic equation reflecting the stability of the single renewable energy grid-connected system based on the transfer function matrix. The short-circuit ratio calculation module is used to convert the single new energy grid-connected system into a single feed-in system based on the dynamic characteristics of the grid operating condition parameters, and to calculate the short-circuit ratio and critical short-circuit ratio based on the grid operating condition parameters processed by the single feed-in system. The dynamic characteristics of the grid operating condition parameters can reflect the changes in the grid operating condition. The strength judgment module is used to judge the grid strength of the single new energy grid-connected system under preset operating conditions based on the short-circuit ratio and the critical short-circuit ratio, and to obtain the small disturbance stability margin. The single new energy grid-connected system includes a network side and an equipment side, and the transfer function matrix includes a first transfer function matrix on the network side and a second transfer function matrix on the equipment side. The second transfer function matrix on the device side is: ； in, This is the second transfer function matrix on the device side. For the admittance matrix of new energy equipment, Let be the admittance matrix of SVG. This refers to the rated capacity of the SVG; , , It is the admittance matrix normalized to its own capacity under rated operating conditions. For the output power of new energy equipment, The voltage at the grid connection point for new energy equipment; For the d-axis output current of new energy equipment; Based on the transfer function matrix, the closed-loop characteristic equation reflecting the stability of the single-new energy grid-connected system is established as follows: ； in, It is the admittance matrix normalized to its own capacity under rated operating conditions. For the output power of new energy equipment, Let be the admittance matrix of SVG. B is the rated capacity of the SVG; S is the admittance matrix on the network side; and S is the Laplace operator. The closed-loop characteristic equation for equating the single renewable energy grid-connected system to a single feed-in system is as follows: ； ； ； in, It is the admittance matrix normalized to its own capacity under rated operating conditions. The impedance-admittance matrix is ​​the dynamic characteristic of the SVG. The coefficient matrix of the network-side admittance matrix. for The inverse matrix; The influence factor of SVG on the stability of the system under small disturbances; For the rated capacity of the SVG, is the admittance matrix of SVG; SCR is the short-circuit ratio of a single renewable energy grid-connected system without SVG; For the inductance between SVG and new energy equipment, For the grid-connected inductor on the equipment side, It is an identity matrix.

5. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the method for determining the strength of a single new energy grid-connected system as described in any one of claims 1 to 3.

6. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of the method for determining the strength of a single new energy grid-connected system as described in any one of claims 1 to 3.

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