Energy storage adaptive grid connection method and device considering transient whole process support of power grid

Abstract

The invention discloses an energy storage adaptive grid-connected method and device considering power grid transient whole process support, and the method comprises the steps: carrying out the small-signal modeling of a network construction type frequency change, and obtaining a first model; performing small-signal modeling on the power flow to obtain a second model; and according to the first model and the second model, adopting a preset adaptive strategy to adjust and control the network-forming converter. Compared with a traditional controller design method based on fixed parameters, the AVSG can achieve expected performance under different power grid conditions, such as no oscillation, specified steady-state time and minimum overshoot.

Description

Technical Field

[0001] The present invention belongs to the technical field of grid-connected converters, and in particular to an energy storage adaptive grid-connected method and device taking into account the full-process transient support of a power grid. Background Art

[0002] It is very important to analyze the negative impact of grid impedance on power coupling in grid-forming inverters. However, most of the control strategies to solve the power coupling problem in the literature focus on grid-forming inverters based on droop control. These techniques include virtual inductance, virtual impedance, adaptive virtual impedance, adaptive droop control, and various improved droop control strategies. Few studies focus on solving the power coupling problem in VSG-based grid-forming inverters, especially in GCM. In the prior art, the power equation considering the resistor-inductor grid impedance is linearized at a specific operating point, and then a power decoupling method based on compensating the coupled components of the power equation is proposed. In the prior art, a unified dynamic power coupling model is proposed to evaluate the power coupling characteristics. In the prior art, the limitations of decoupling power flows using only virtual inductance are studied, and a power decoupling control method based on q-axis voltage drop is proposed. In addition, the impact of adopting virtual inductance on power decoupling is evaluated in detail in the prior art. In the prior art, a universal control is proposed to meet the operation requirements in GCM and IM. As a result, in GCM, the oscillation is suppressed and the steady-state time of the output power is shortened.

[0003] Despite the above efforts to eliminate the power decoupling problem in VSG-based grid-forming inverters, there are still some shortcomings that need to be addressed. First, the control design based on linearization and decoupling is only effective and accurate at a specific linearized operating point. Second, the proposed control design assumes that the grid impedance is purely inductive, which is not true in weak voltage grids. Last but not least, there is no comprehensive study that reveals the performance of VSGs in GCM, especially considering the operating scenarios with different short circuit ratio (SCR) values, different grid impedance ratios Xg / Rg, and grid impedance variations with the same Xg / Rg ratio.

[0004] Conventional virtual synchronous generators (VSGs) are usually designed to meet certain operation and control requirements in island mode. However, once the VSG switches to grid-connected mode (GCM), stable operation under different grid conditions cannot be guaranteed. Especially in strong grids, poor dynamic performance may result, such as significant oscillations, long steady-state time and high overshoot. Summary of the invention

[0005] The present invention provides an energy storage adaptive grid-connected method and device taking into account the full process support of the transient state of the power grid, which is used to solve technical problems that may cause poor dynamic performance, such as significant oscillation, longer steady-state time and higher overshoot.

[0006] In a first aspect, the present invention provides an energy storage adaptive grid connection method taking into account the full process support of the transient state of the power grid, comprising:

[0007] Perform small signal modeling on the frequency change of the network type to obtain the first model;

[0008] Perform small signal modeling on the power flow to obtain the second model;

[0009] According to the first model and the second model, a preset adaptive strategy is adopted to adjust and control the grid-connected converter, wherein the adaptive strategy is specifically:

[0010] When the inverter starts, if the inverter operates in IM or GCM and the AVSG is disabled, the first control parameter of the VSG base inverter designed by equations (4), (6) and (8) is used, where equation (4) is: D p is the damping coefficient, f max and f min are the maximum and minimum frequency deviations allowed in IM, P max is the maximum active power that the VSG can provide;

[0011] Formula (6) is: J is the inertia coefficient of VSG, T VSG is the time constant of VSG, ω0 is the rated angular frequency of the power grid;

[0012] Formula (8) is: K pq is the QV droop coefficient, V max is the maximum voltage deviation allowed in the grid code, V min is the minimum voltage deviation allowed in the grid code, Q max is the maximum reactive power;

[0013] When AVSG is enabled, the GIE algorithm will be activated to initialize the resistor R g and reactance X g The impedance value is calculated, and the second control parameters of the VSG basic inverter are calculated according to equations (36), (37), (34) and (38). The second control parameters include J, D p , K pq and K iq , where formula (36) is: K 11 No actual meaning, M = K 11 K 22 -K 12 K 21 , K 11 For n is the rated angular frequency;

[0014] Formula (37) is: ζ is damping;

[0015] Formula (34) is: K 22 No real meaning;

[0016] Formula (38) is:

[0017] Each time the power reference command changes, an enable signal is generated, and an impedance value is updated according to the enable signal, wherein the enable signal includes a delay time, and the delay time is equal to the time required by the GIE algorithm;

[0018] The control parameters of the VSG basic inverter are recalculated according to the updated impedance value, and the control parameters of the VSG basic inverter are recalculated according to the recalculated J and D p , K pq and K iq Regulate and control the grid-connected converter.

[0019] In a second aspect, the present invention provides a flexible control device for a grid-type converter, comprising:

[0020] A first modeling module is configured to perform small signal modeling on the frequency change of the meshing pattern to obtain a first model;

[0021] A second modeling module is configured to perform small signal modeling on the power flow to obtain a second model;

[0022] The control module is configured to adjust and control the grid-connected converter using a preset adaptive strategy according to the first model and the second model, wherein the adaptive strategy is specifically:

[0023] When the inverter starts, if the inverter operates in IM or GCM and the AVSG is disabled, the first control parameter of the VSG base inverter designed by equations (4), (6) and (8) is used, where equation (4) is: D p is the damping coefficient, f max and f min are the maximum and minimum frequency deviations allowed in IM, P max is the maximum active power that the VSG can provide;

[0024] Formula (6) is: J is the inertia coefficient of VSG, T VSG is the time constant of VSG, ω0 is the rated angular frequency of the power grid;

[0025] Formula (8) is: K pq is the QV droop coefficient, V max is the maximum voltage deviation allowed in the grid code, V min is the minimum voltage deviation allowed in the grid code, Q max is the maximum reactive power;

[0026] When AVSG is enabled, the GIE algorithm will be activated to initialize the resistor R g and reactance X g The impedance value is calculated, and the second control parameters of the VSG basic inverter are calculated according to equations (36), (37), (34) and (38). The second control parameters include J, D p , K pq and K iq , where formula (36) is: K 11 No actual meaning, M = K 11 K 22 -K 12 K 21 , K 11 For n is the rated angular frequency;

[0027] Formula (37) is: ζ is damping;

[0028] Formula (34) is: K 22 No real meaning;

[0029] Formula (38) is:

[0030] Each time the power reference command changes, an enable signal is generated, and an impedance value is updated according to the enable signal, wherein the enable signal includes a delay time, and the delay time is equal to the time required by the GIE algorithm;

[0031] The control parameters of the VSG basic inverter are recalculated according to the updated impedance value, and the control parameters of the VSG basic inverter are recalculated according to the recalculated J and D p , K pq and K iq Regulate and control the grid-connected converter.

[0032] According to a third aspect, an electronic device is provided, comprising: at least one processor, and a memory communicatively connected to the at least one processor, wherein the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can perform the steps of the flexible control method of a grid-type converter according to any embodiment of the present invention.

[0033] In a fourth aspect, the present invention further provides a computer-readable storage medium having a computer program stored thereon, wherein when the program instructions are executed by a processor, the processor executes the steps of the flexible control method for a grid-type converter of any embodiment of the present invention.

[0034] The flexible control method and device of the grid-type converter of the present application analyzes the inherent coupling between active power and reactive power and its dependence on grid conditions (such as short-circuit ratio, grid impedance ratio Xg / Rg and wide variations in grid impedance). Afterwards, an adaptive VSG (AVSG) control strategy based on online grid impedance estimation is proposed to ensure the robust operation of the VSG under strong and weak grid conditions. This technology allows the operator to specify the desired steady-state time and damping ratio of the output power. In order to estimate the grid impedance in real time without additional hardware and reduce the related impact on power quality, an online event-driven grid impedance estimation algorithm is embedded in the control loop of the AVSG. Compared with the traditional fixed parameter-based controller design method, the AVSG can achieve the desired performance under different grid conditions, such as no oscillation, specified steady-state time, and minimal overshoot. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0036] Figure 1 A flow chart of an energy storage adaptive grid-connected method taking into account the full process support of power grid transient state provided by one embodiment of the present invention;

[0037] Figure 2 A structural block diagram of a grid-type converter flexible control device provided by an embodiment of the present invention;

[0038] Figure 3 It is a schematic diagram of the structure of an electronic device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] See also Figure 1 , which shows a flow chart of an energy storage adaptive grid-connected method of the present application that takes into account the entire transient process support of the power grid.

[0041] like Figure 1 As shown, the flexible control method of the grid-type converter specifically includes the following steps:

[0042] Step S101, performing small signal modeling on the frequency variation of the meshing pattern to obtain a first model.

[0043] In this step, the VSG is expected to provide frequency support when the load changes. Therefore, the inertia and damping parameters of the VSG are designed to meet the frequency change rate (ROCOF) requirements. Ignoring line losses, the small signal transfer function from load change ΔPload to angular frequency change Δω is derived as:

[0044]

[0045] Where s is the Laplace operator;

[0046] Rearranging formula (1) yields:

[0047]

[0048] Assumptions Then formula (2) can be rewritten as:

[0049]

[0050] Calculate the damping coefficient, the expression is:

[0051]

[0052] In the formula, m p No real meaning, P max is the maximum active power that VSG can provide, f max is the maximum frequency deviation allowed in IM, f min is the minimum frequency deviation allowed in IM;

[0053] Based on equations (2) and (3), the inertia coefficient of VSG is calculated as follows:

[0054]

[0055] Where, J is the inertia coefficient of VSG, T VSG is the time constant of VSG, ω0 is the rated angular frequency of the power grid;

[0056] The Bode plot of the open-loop transfer function of the VSG is expressed as:

[0057]

[0058] Where δ is the frequency deviation;

[0059] Calculate the QV droop coefficient, the expression is:

[0060]

[0061] In the formula, K pq is the QV droop coefficient, V max is the maximum voltage deviation allowed in the grid code, V min is the minimum voltage deviation allowed in the grid code, Q max is the maximum reactive power. The number 2 in the denominator indicates that the VSG can supply and absorb reactive power. In GCM, it is recommended to add an integral term in the reactive power controller to track the reactive power reference with zero steady-state error. Therefore, this application uses a PI controller for the reactive power control channel.

[0062] In GCM, the main control objective of VSG is to adjust its output active and reactive power to the required reference instructions. In order to further study the performance of VSG in GCM and how the grid impedance parameters affect its performance, a small signal model with consideration is constructed. Based on the inherent power flow coupling, the small signal model is derived below and further stability analysis is performed.

[0063] Step S102, performing small signal modeling on the power flow to obtain a second model.

[0064] In this step, the active power and reactive power injected by VSG into the grid are calculated, and the expressions are:

[0065]

[0066] Where P pcc is the active power injected by VSG into the grid, R g is the resistance of the grid, V i is the effective value of the PCC voltage, V j is the effective value of the grid side voltage, θ ij V i and Vj The phase angle between g is the inductance of the grid, Q pcc is the reactive power injected by VSG into the grid;

[0067] In order to study the stability characteristics and dynamic performance of VSG, the small signal model of active power and reactive power injected by VSG into the power grid are established, and the expressions are as follows:

[0068]

[0069] Where ΔP pcc is the deviation of active power, ΔQ pcc is the reactive power deviation, K 11 , K 12 , K 21 , K 22 No practical meaning, Δθ ij is the power angle deviation, ΔV i is the voltage amplitude deviation, V i0 is the steady-state effective value of the PCC line-to-ground voltage, θ ij0 is the power angle at the steady state point;

[0070] Active and reactive power are coupled through the power angle and voltage amplitude, as shown in Equations (9) to (12). In addition, the grid / line impedance (i.e., and ) has a significant impact on the coupling and direct path terms. In summary, active and reactive power cannot be controlled independently in a resistive-inductive grid. Therefore, this inherent coupling between active and reactive power will hinder the optimal control of the VSG.

[0071] It should be noted that the reactive power command is set to zero, so and are not considered in the analysis. In addition, and are obtained based on the linearized small signal model of the power flow shown in Equation (12), calculated from the steady-state operation of the VSG. Then, the open-loop transfer function of the active power loop considering and can be calculated as:

[0072]

[0073] In the formula, G 11-OL (s), G 21-OL (s) are all open-loop transfer functions, ΔP pcc is the deviation of PCC active power, ΔP ref is the deviation of the reference active power, ΔQ pcc is the deviation of PCC reactive power.

[0074] Step S103: According to the first model and the second model, a preset adaptive strategy is used to adjust and control the grid-connected converter.

[0075] In this step, the small signal model of the VSG-grid system (Eq. (11) and Eq. (12)) is introduced to obtain the relationship between the VSG controller parameters and the system response. On this basis, the VSG controller parameters are adjusted in an adaptive manner to obtain the desired response. p (s), G q (s) is defined as the transfer function of VSG and the transfer function of reactive power controller, that is:

[0076]

[0077] Power angle deviation Δθ ij , voltage amplitude deviation ΔV i , Reference active power deviation ΔP ref , deviation of reference reactive power ΔQ ref The relationship between them is:

[0078] Δθ ij =G p (s)(ΔP ref -K 11 Δθ ij -K 12 ΔV i ), (16)

[0079] ΔV i =G q (s)(ΔQ ref -K 21 Δθ ij -K 22 ΔV i ), (17)

[0080] Rewrite it as:

[0081]

[0082] Substituting formula (18) into formula (11), we get:

[0083]

[0084] In the formula, H 11 , H 12 , H 21 , H 22 All are matrix expressions;

[0085]

[0086]

[0087] In the formula, H 11 (s), H 12 (s), H21 (s), H 22 (s) have no practical meaning;

[0088] Where M = K 11 K 22 -K 12 K 21 , (twenty four)

[0089] In order to achieve good dynamic effects, it is assumed that:

[0090]

[0091] In the formula, ω n is the natural frequency, ζ is the damping ratio;

[0092] By replacing H in equation (20) with 11 (s), and then use G in equations (14) and (15) in the obtained equations p (s), G q (s) by substitution, we can get:

[0093]

[0094] Substituting equations (27)-(29) into equation (23), we obtain:

[0095]

[0096] definition:

[0097]

[0098] H 22 (s) can be written as:

[0099]

[0100] choose:

[0101]

[0102] You can get:

[0103]

[0104] Therefore, due to the cross-coupling term K 12 , K 21 is not dominant, that is, |K 12 K 21 |≤|K 11 K 22 |, we can conclude from equation (31) that 0≤σ≤1, and therefore 0≤γ≤1. As a result, except for H 11(s) Similar to a pair of poles, H 22 (s) has one real pole and three zeros in the left half plane and is stable. Finally, by substituting equation (34) into equations (27), (28) and (29), we can obtain:

[0105]

[0106] In the formula, K 11 No actual meaning, M = K 11 K 22 -K 12 K 21 , K 11 For n is the rated angular frequency;

[0107]

[0108] Based on equations (34), (36), (37) and (38), the VSG and reactive power controller can be adjusted so that H 11 (s), H 22 (s) has the desired natural frequency ω n and the damping ratio ζ. However, it can be seen from these equations that J, D p , K pq , K iq It's K 11 , K 22 functions, which in turn are determined by the operating point R g , X g 、V i0 、V j ,θ ij0 Decide,

[0109] The above shows that in order to adjust the VSG to cope with strong and weak grids, grid impedance information must be known in advance. However, a key challenge is that the grid impedance is time-varying, which prevents optimal design if only fixed values ​​are used for design. Therefore, accurate control can only be performed based on the actual value of the grid impedance.

[0110] To address this issue, an online GIE algorithm that exploits the inverter itself can be used. This approach is cost-effective as it does not require additional hardware and only uses available local measurements to estimate the grid impedance seen by the inverter at the PCC.

[0111] Several online GIE algorithms can be integrated into the control loop of the inverter. These algorithms are generally classified into three categories, namely active, passive and hybrid techniques. GIE techniques based on single frequency injection have shown very accurate results when the estimation time and disturbance amplitude are designed properly. Therefore, online active GIE based on 75Hz injection is chosen in this paper. In order to avoid estimation errors due to the presence of background intermodulation / subharmonics in the grid voltage, the injection / estimation time is set to 200ms. This allows accurate measurements due to the use of a resolution of 5Hz.

[0112] In order to address the impact of disturbance current on power quality and the trade-off between active and passive technologies, this application proposes a new algorithm that automatically triggers grid impedance only when needed. Therefore, the potential adverse effects of disturbance amplitude on power quality can be significantly reduced. In addition, to ensure fast and accurate estimation of grid impedance, the disturbance current is generated at 25Hz in the dq reference frame and added to the current reference values ​​id-ref and iq-ref, thereby quickly tracking the disturbance current using the fast response of the inner loop.

[0113] At the same time, when injecting id-inj, iq-inj, record the current and voltage response (v res (75Hz),i res (75Hz)). Then, the fundamental frequency grid impedance Zg(50Hz) is estimated by approximating its value to Zg(75Hz), as shown in equation (39).

[0114]

[0115] In the formula, is the real part, v res (75Hz) is the feedback value of the voltage at 75hz after a signal is injected, i res (75Hz) is the feedback value of the current at 75hz after a signal is injected, L g is the inductor, Is the imaginary part.

[0116] The specific adaptive strategies are:

[0117] When the inverter starts, if the inverter operates in IM or GCM and the AVSG is disabled, the first control parameters of the VSG base inverter designed by equations (4), (6) and (8) are used;

[0118] When AVSG is enabled, the GIE algorithm will be activated to initialize the impedance values ​​of the resistor Rg and the reactance Xg, and calculate the second control parameters of the VSG base inverter according to equations (36), (37), (34) and (38), respectively. The second control parameters include J, D p , Kpq and K iq ;

[0119] Each time the power reference command changes, an enable signal is generated, and an impedance value is updated according to the enable signal, wherein the enable signal includes a delay time, and the delay time is equal to the time required by the GIE algorithm;

[0120] The control parameters of the VSG basic inverter are recalculated according to the updated impedance value, and the control parameters of the VSG basic inverter are recalculated according to the recalculated J and D p , K pq and K iq Regulate and control the grid-connected converter.

[0121] In summary, the method of this application analyzes the inherent coupling between active power and reactive power and its dependence on grid conditions such as short-circuit ratio, grid impedance ratio Xg / Rg, and wide variations in grid impedance. Afterwards, an adaptive VSG (AVSG) control strategy based on online grid impedance estimation is proposed to ensure the robust operation of the VSG under strong and weak grid conditions. This technology allows the operator to specify the desired steady-state time and damping ratio of the output power. In order to estimate the grid impedance in real time without additional hardware and reduce the associated impact on power quality, an online event-driven grid impedance estimation algorithm is embedded in the control loop of the AVSG. Compared with traditional fixed-parameter-based controller design methods, the AVSG is able to achieve the desired performance under different grid conditions, such as no oscillation, specified steady-state time, and minimal overshoot.

[0122] See also Figure 2 , which shows a structural block diagram of a grid-type converter flexible control device of the present application.

[0123] like Figure 2 As shown, the grid-type converter flexible control device 200 includes a first modeling module 210 , a second modeling module 220 and a control module 230 .

[0124] The first modeling module 210 is configured to perform small signal modeling on the frequency change of the meshing type to obtain a first model;

[0125] A second modeling module 220 is configured to perform small signal modeling on the power flow to obtain a second model;

[0126] The control module 230 is configured to adjust and control the grid-connected converter using a preset adaptive strategy according to the first model and the second model, wherein the adaptive strategy is specifically:

[0127] When the inverter starts, if the inverter operates in IM or GCM and the AVSG is disabled, the first control parameter of the VSG base inverter designed by equations (4), (6) and (8) is used, where equation (4) is: D p is the damping coefficient, f max and f min are the maximum and minimum frequency deviations allowed in IM, P max is the maximum active power that the VSG can provide;

[0128] Formula (6) is: J is the inertia coefficient of VSG, T VSG is the time constant of VSG, ω o is the rated angular frequency of the power grid;

[0129] Formula (8) is: K pq is the QV droop coefficient, v max is the maximum voltage deviation allowed in the grid code, v min is the minimum voltage deviation allowed in the grid code, Q max is the maximum reactive power;

[0130] When AVSG is enabled, the GIE algorithm will be activated to initialize the resistor R g and reactance X g The impedance value is calculated, and the second control parameters of the VSG basic inverter are calculated according to equations (36), (37), (34) and (38). The second control parameters include J, D p , K pq and K iq , where formula (36) is: K 11 No actual meaning, M = K 11 K 22 -K 12 K 21 , K 11 For n is the rated angular frequency;

[0131] Formula (37) is: ζ is damping;

[0132] Formula (34) is: K 22 No real meaning;

[0133] Formula (38) is:

[0134] Each time the power reference command changes, an enable signal is generated, and an impedance value is updated according to the enable signal, wherein the enable signal includes a delay time, and the delay time is equal to the time required by the GIE algorithm;

[0135] The control parameters of the VSG basic inverter are recalculated according to the updated impedance value, and the control parameters of the VSG basic inverter are recalculated according to the recalculated J and D p , K pq and D iq Regulate and control the grid-connected converter.

[0136] It should be understood that Figure 2 Modules and references documented in Figure 1 Therefore, the operations and features described above for the method and the corresponding technical effects are also applicable to Figure 2 The modules in it will not be described in detail here.

[0137] In some other embodiments, the embodiments of the present invention further provide a computer-readable storage medium having a computer program stored thereon, wherein when the program instructions are executed by a processor, the processor executes the grid-type converter flexible control method in any of the above method embodiments;

[0138] As an implementation mode, the computer-readable storage medium of the present invention stores computer-executable instructions, and the computer-executable instructions are configured as follows:

[0139] Perform small signal modeling on the frequency change of the network type to obtain the first model;

[0140] Perform small signal modeling on the power flow to obtain the second model;

[0141] According to the first model and the second model, a preset adaptive strategy is adopted to adjust and control the grid-connected converter, wherein the adaptive strategy is specifically:

[0142] When the inverter starts, if the inverter operates in IM or GCM and the AVSG is disabled, the first control parameter of the VSG base inverter designed by equations (4), (6) and (8) is used, where equation (4) is: D p is the damping coefficient, f max and f min are the maximum and minimum frequency deviations allowed in IM, P max is the maximum active power that the VSG can provide;

[0143] Formula (6) is: J is the inertia coefficient of VSG, T VSGis the time constant of VSG, ω o is the rated angular frequency of the power grid;

[0144] Formula (8) is: K pq is the QV droop coefficient, V max is the maximum voltage deviation allowed in the grid code, V min is the minimum voltage deviation allowed in the grid code, Q max is the maximum reactive power;

[0145] When AVSG is enabled, the GIE algorithm will be activated to initialize the resistor R g and reactance X g The impedance value is calculated, and the second control parameters of the VSG basic inverter are calculated according to equations (36), (37), (34) and (38). The second control parameters include J, D p , K pq and K iq , where formula (36) is: K 11 No actual meaning, M = K 11 K 22 -K 12 K 21 , K 11 For n is the rated angular frequency;

[0146] Formula (37) is: ζ is damping;

[0147] Formula (34) is: K 22 No real meaning;

[0148] Formula (38) is:

[0149] Each time the power reference command changes, an enable signal is generated, and an impedance value is updated according to the enable signal, wherein the enable signal includes a delay time, and the delay time is equal to the time required by the GIE algorithm;

[0150] The control parameters of the VSG basic inverter are recalculated according to the updated impedance value, and the control parameters of the VSG basic inverter are recalculated according to the recalculated J and D p , K pq and K iq Regulate and control the grid-connected converter.

[0151] The computer-readable storage medium may include a program storage area and a data storage area, wherein the program storage area may store an operating system and an application required by at least one function; the data storage area may store data created according to the use of the flexible control device of the meshed converter, etc. In addition, the computer-readable storage medium may include a high-speed random access memory, and may also include a memory, such as at least one disk storage device, a flash memory device, or other non-volatile solid-state storage device. In some embodiments, the computer-readable storage medium may optionally include a memory remotely arranged relative to the processor, and these remote memories may be connected to the flexible control device of the meshed converter via a network. Examples of the above-mentioned network include, but are not limited to, the Internet, an intranet, a local area network, a mobile communication network, and combinations thereof.

[0152] Figure 3 is a schematic diagram of the structure of an electronic device provided by an embodiment of the present invention, such as Figure 3 As shown, the device includes: a processor 310 and a memory 320. The electronic device may also include: an input device 330 and an output device 340. The processor 310, the memory 320, the input device 330 and the output device 340 may be connected via a bus or other means. Figure 3 The example of the connection via bus is taken. The memory 320 is the above-mentioned computer-readable storage medium. The processor 310 executes various functional applications and data processing of the server by running the non-volatile software programs, instructions and modules stored in the memory 320, that is, the flexible control method of the grid-type converter of the above-mentioned method embodiment is realized. The input device 330 can receive input digital or character information, and generate key signal input related to user settings and function control of the flexible control device of the grid-type converter. The output device 340 may include display devices such as display screens.

[0153] The electronic device can execute the method provided by the embodiment of the present invention, and has the functional modules and beneficial effects corresponding to the execution method. For technical details not described in detail in this embodiment, please refer to the method provided by the embodiment of the present invention.

[0154] As an implementation mode, the electronic device is applied to a grid-type converter flexible control device, used for a client, and includes: at least one processor; and a memory connected to the at least one processor in communication; wherein the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can:

[0155] Perform small signal modeling on the frequency change of the network type to obtain the first model;

[0156] Perform small signal modeling on the power flow to obtain the second model;

[0157] According to the first model and the second model, a preset adaptive strategy is adopted to adjust and control the grid-connected converter, wherein the adaptive strategy is specifically:

[0158] When the inverter starts, if the inverter operates in IM or GCM and the AVSG is disabled, the first control parameter of the VSG base inverter designed by equations (4), (6) and (8) is used, where equation (4) is: D p is the damping coefficient, f max and f min are the maximum and minimum frequency deviations allowed in IM, P max is the maximum active power that the VSG can provide;

[0159] Formula (6) is: J is the inertia coefficient of VSG, T VSG is the time constant of VSG, ω0 is the rated angular frequency of the power grid;

[0160] Formula (8) is: K pq is the QV droop coefficient, V max is the maximum voltage deviation allowed in the grid code, V min is the minimum voltage deviation allowed in the grid code, Q max is the maximum reactive power;

[0161] When AVSG is enabled, the GIE algorithm will be activated to initialize the resistor R g and reactance X g The impedance value is calculated, and the second control parameters of the VSG basic inverter are calculated according to equations (36), (37), (34) and (38). The second control parameters include J, D p , K pq and K iq , where formula (36) is: K 11 No actual meaning, M = K 11 K 22 -K 12 K 21 , K 11 For n is the rated angular frequency;

[0162] Formula (37) is: ζ is damping;

[0163] Formula (34) is: K 22 No real meaning;

[0164] Formula (38) is:

[0165] Each time the power reference command changes, an enable signal is generated, and an impedance value is updated according to the enable signal, wherein the enable signal includes a delay time, and the delay time is equal to the time required by the GIE algorithm;

[0166] The control parameters of the VSG basic inverter are recalculated according to the updated impedance value, and the control parameters of the VSG basic inverter are recalculated according to the recalculated J and D p , K pq and K iq Regulate and control the grid-connected converter.

[0167] Through the description of the above implementation methods, those skilled in the art can clearly understand that each implementation method can be implemented by means of software plus a necessary general hardware platform, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solution is essentially or the part that contributes to the prior art can be embodied in the form of a software product, and the computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a disk, an optical disk, etc., including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods of each embodiment or some parts of the embodiment.

[0168] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An energy storage adaptive grid connection method taking into account the full process support of the transient state of the power grid, characterized in that: include: Perform small signal modeling on the frequency change of the network type to obtain the first model; Perform small signal modeling on the power flow to obtain the second model; According to the first model and the second model, a preset adaptive strategy is adopted to adjust and control the grid-connected converter, wherein the adaptive strategy is specifically: When the inverter starts, if the inverter operates in IM or GCM and the AVSG is disabled, the first control parameters of the VSG base inverter designed by equations (4), (6) and (8) are used, where equation (4) is: D p is the damping coefficient, f max and f min are the maximum and minimum frequency deviations allowed in IM, P max is the maximum active power that the VSG can provide; Formula (6) is: J is the inertia coefficient of VSG, T VSG is the time constant of VSG, ω0 is the rated angular frequency of the power grid; Formula (8) is: K pq is the QV droop coefficient, V max is the maximum voltage deviation allowed in the grid code, V min is the minimum voltage deviation allowed in the grid code, Q max is the maximum reactive power; When AVSG is enabled, the GIE algorithm will be activated to initialize the resistor R g and reactance X g The impedance value is calculated, and the second control parameters of the VSG basic inverter are calculated according to equations (36), (37), (34) and (38). The second control parameters include J, D p , K pq and K iq , where formula (36) is: K 11 No actual meaning, M = K 11 K 22 -K 12 K 21 , K 11 For n is the rated angular frequency; Formula (37) is: ζ is damping; Formula (34) is: K 22 No real meaning; Formula (38) is: Each time the power reference command changes, an enable signal is generated, and an impedance value is updated according to the enable signal, wherein the enable signal includes a delay time, and the delay time is equal to the time required by the GIE algorithm; The control parameters of the VSG basic inverter are recalculated according to the updated impedance value, and the control parameters of the VSG basic inverter are recalculated according to the recalculated J and D p , K pq and K iq Regulate and control the grid-connected converter.

2. The energy storage adaptive grid connection method taking into account the full process support of the transient state of the power grid according to claim 1 is characterized in that: The small signal modeling of the network type frequency change to obtain the first model includes: Ignoring line losses, the small signal transfer function from load change ΔPload to angular frequency change Δω is derived as: Where s is the Laplace operator; Rearranging formula (1) yields: Assumptions Then formula (2) can be rewritten as: Calculate the damping coefficient, the expression is: In the formula, m p No real meaning, P max is the maximum active power that VSG can provide, f max is the maximum frequency deviation allowed in IM, f min is the minimum frequency deviation allowed in IM; Based on equations (2) and (3), the inertia coefficient of VSG is calculated as follows: Where, J is the inertia coefficient of VSG, T VSG is the time constant of VSG, ω0 is the rated angular frequency of the power grid; The Bode plot of the open-loop transfer function of the VSG is expressed as: Where δ is the frequency deviation; Calculate the QV droop coefficient, the expression is: In the formula, K pq is the QV droop coefficient, V max is the maximum voltage deviation allowed in the grid code, V min is the minimum voltage deviation allowed in the grid code, Q max is the maximum reactive power.

3. The energy storage adaptive grid connection method taking into account the full process support of the transient state of the power grid according to claim 1 is characterized in that: The small signal modeling of the power flow to obtain the second model includes: Calculate the active power and reactive power injected by VSG into the grid. The expression is: Where P pcc is the active power injected by VSG into the grid, R g is the resistance of the grid, V i is the effective value of the PCC voltage, V j is the effective value of the grid side voltage, θ ij V i and V j The phase angle between g is the inductance of the grid, Q pcc is the reactive power injected by VSG into the grid; The small signal model of active power and reactive power injected by VSG into the power grid is established, and the expression is: Where ΔP pcc is the deviation of active power, ΔQ pcc is the reactive power deviation, K 11 , K 12 , K 21 , K 22 No practical meaning, Δθ ij is the power angle deviation, ΔV i is the voltage amplitude deviation, V i0 is the steady-state effective value of the PCC line-to-ground voltage, θ ij0 is the power angle at the steady state point; Calculate the open-loop transfer function of the active power loop taking into account the impedance of the grid and the line, and the expression is: In the formula, G 11-OL (s), G 21-OL (s) are all open-loop transfer functions, ΔP pcc is the deviation of PCC active power, ΔP ref is the deviation of the reference active power, ΔQ pcc is the deviation of PCC reactive power.

4. A flexible control device for a grid-type converter, characterized in that: include: A first modeling module is configured to perform small signal modeling on the frequency change of the meshing pattern to obtain a first model; A second modeling module is configured to perform small signal modeling on the power flow to obtain a second model; The control module is configured to adjust and control the grid-connected converter using a preset adaptive strategy according to the first model and the second model, wherein the adaptive strategy is specifically: When the inverter starts, if the inverter operates in IM or GCM and the AVSG is disabled, the first control parameters of the VSG base inverter designed by equations (4), (6) and (8) are used, where equation (4) is: D p is the damping coefficient, f max and f min are the maximum and minimum frequency deviations allowed in IM, P max is the maximum active power that the VSG can provide; Formula (6) is: J is the inertia coefficient of VSG, T VSG is the time constant of VSG, ω0 is the rated angular frequency of the power grid; Formula (8) is: K pq is the QV droop coefficient, V max is the maximum voltage deviation allowed in the grid code, V min is the minimum voltage deviation allowed in the grid code, Q max is the maximum reactive power; When AVSG is enabled, the GIE algorithm will be activated to initialize the resistor R g and reactance X g The impedance value is calculated, and the second control parameters of the VSG basic inverter are calculated according to equations (36), (37), (34) and (38). The second control parameters include J, D p , K pq and K iq , where formula (36) is: K 11 No actual meaning, M = K 11 K 22 -K 12 K 21 , K 11 For n is the rated angular frequency; Formula (37) is: ζ is damping; Formula (34) is: K 22 No real meaning; Formula (38) is: Each time the power reference command changes, an enable signal is generated, and an impedance value is updated according to the enable signal, wherein the enable signal includes a delay time, and the delay time is equal to the time required by the GIE algorithm; The control parameters of the VSG basic inverter are recalculated according to the updated impedance value, and the control parameters of the VSG basic inverter are recalculated according to the recalculated J and D p , K pq and K iq Regulate and control the grid-connected converter.

5. An electronic device, characterized in that: include: At least one processor, and a memory communicatively connected to the at least one processor, wherein the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor to enable the at least one processor to perform the method 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 program is executed by a processor, the method according to any one of claims 1 to 3 is implemented.

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