An adaptive grid connection method and device for energy storage that considers the entire transient process of the power grid

Abstract

This invention discloses an adaptive grid-connected energy storage method and device that considers the entire transient process of the power grid. The method includes: performing small-signal modeling on the frequency variation of the grid structure to obtain a first model; performing small-signal modeling on the power flow to obtain a second model; and adjusting and controlling the grid-connected converter using a preset adaptive strategy based on the first model and the second model. Compared with traditional controller design methods based on fixed parameters, AVSG can achieve the desired performance under different grid conditions, such as no oscillation, specified steady-state time, and minimal overshoot.

Description

Technical Field

[0001] This invention belongs to the field of grid-connected converter technology, and particularly relates to an energy storage adaptive grid connection method and device that takes into account the entire process of grid transient support. Background Technology

[0002] Analyzing the negative impact of grid impedance on power coupling in grid-shaped inverters is crucial. However, most control strategies in the literature addressing power coupling primarily focus on grid-shaped inverters based on droop control. These techniques include virtual inductors, virtual impedance, adaptive virtual impedance, adaptive droop control, and various improved droop control strategies. Few studies focus on addressing power coupling in VSG-based grid-shaped inverters, especially in GCM. In existing technologies, a power decoupling method based on compensating for the coupling components of the power equation is proposed, considering the linearization of the power equation for the resistive-inductor grid impedance at a specific operating point. A unified dynamic power coupling model is proposed to evaluate power coupling characteristics. The limitations of using only virtual inductors to decouple power flow are investigated, and a power decoupling control method based on q-axis voltage drop is proposed. Furthermore, the impact of using virtual inductors on power decoupling is evaluated in detail in existing technologies. A general control is proposed to meet the operational requirements under both GCM and IM. Therefore, in GCM, oscillations are suppressed, and the steady-state time of the output power is shortened.

[0003] Despite the efforts made to eliminate power decoupling issues in VSG-based grid shaping inverters, several shortcomings remain. First, the control design based on linearization and decoupling is only effective and accurate at specific linearization operating points. Second, the proposed control design assumes that the grid impedance is purely inductive, which does not hold true in low-voltage grids. Last but not least, comprehensive studies have yet to reveal the performance of VSGs in GCMs, especially considering operating scenarios with different short-circuit ratios (SCRs), different grid impedance ratios Xg / Rg, and grid impedance variations with the same Xg / Rg ratio.

[0004] Traditional virtual synchronous generators (VSGs) are typically designed to meet certain operational and control requirements in islanded mode. However, once a VSG switches to grid-connected mode (GCM), stable operation under varying grid conditions cannot be guaranteed. This can be particularly problematic in high-voltage grids, potentially leading to poor dynamic performance, such as significant oscillations, longer steady-state times, and higher overshoot. Summary of the Invention

[0005] This invention provides an energy storage adaptive grid connection method and device that takes into account the entire transient process of the power grid, in order to solve technical problems that may lead to poor dynamic performance, such as significant oscillations, long steady-state time and high overshoot.

[0006] In a first aspect, the present invention provides an adaptive grid connection method for energy storage that takes into account the entire transient process of the power grid, comprising:

[0007] Small-signal modeling is performed on the frequency variation of the network structure to obtain the first model;

[0008] By modeling the tidal current using small signals, a second model is obtained;

[0009] Based on the first model and the second model, a preset adaptive strategy is used to adjust and control the grid-type converter, wherein the adaptive strategy specifically includes:

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

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

[0012] Equation (8) is: K pq Let V be the droop coefficient of QV. max V is the maximum permissible voltage deviation specified in the power grid specifications. min Q is the minimum permissible voltage deviation specified in the power grid standard. max This represents 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 base inverter are calculated according to equations (36), (37), (34) and (38), respectively. The second control parameters include J and D. p K pq and K iq Equation (36) is: K 11 No practical meaning, M=K 11 K 22 -K 12 K 21 K 11 For, ω n The rated angular frequency;

[0014] Equation (37) is: ζ represents damping;

[0015] Equation (34) is: K 22 It has no real meaning;

[0016] Equation (38) is:

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

[0018] The control parameters of the VSG base inverter are recalculated based on the updated impedance value, and based on the recalculated J and D... p K pq and K iq Adjust and control the grid-type converter.

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

[0020] The first modeling module is configured to perform small-signal modeling on the frequency variation of the network structure to obtain the first model;

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

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

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

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

[0025] Equation (8) is: K pq Let V be the droop coefficient of QV. max V is the maximum permissible voltage deviation specified in the power grid specifications. min Q is the minimum permissible voltage deviation specified in the power grid standard. max This represents 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 base inverter are calculated according to equations (36), (37), (34) and (38), respectively. The second control parameters include J and D. p K pq and K iq Equation (36) is: K 11 No practical meaning, M=K 11 K 22 -K 12 K 21 K 11 For, ω n The rated angular frequency;

[0027] Equation (37) is: ζ represents damping;

[0028] Equation (34) is: K 22 It has no real meaning;

[0029] Equation (38) is:

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

[0031] The control parameters of the VSG base inverter are recalculated based on the updated impedance value, and based on the recalculated J and D... p K pq and K iq Adjust and control the grid-type converter.

[0032] Thirdly, 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, the instructions being executed by the at least one processor to enable the at least one processor to perform the steps of the grid-type converter flexible control method according to any embodiment of the present invention.

[0033] Fourthly, the present invention also provides a computer-readable storage medium having a computer program stored thereon, wherein when the program instructions are executed by a processor, the processor performs the steps of the flexible control method for a grid-type converter according to any embodiment of the present invention.

[0034] This application presents a flexible control method and device for grid-connected converters, analyzing the inherent coupling between active 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). Subsequently, an adaptive VSG (AVSG) control strategy based on online grid impedance estimation is proposed to ensure robust operation of the VSG under both strong and weak grid conditions. This technique allows the operator to specify the desired steady-state time and damping ratio of the output power. To estimate 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 AVSG control loop. Compared to traditional controller design methods based on fixed parameters, AVSG can achieve the desired performance under different grid conditions, such as no oscillations, specified steady-state time, and minimal overshoot. Attached Figure Description

[0035] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 A flowchart of an energy storage adaptive grid connection method that takes into account the entire transient process of the power grid, provided by an embodiment of the present invention;

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

[0038] Figure 3 This is a schematic diagram of the structure of an electronic device provided in an embodiment of the present invention. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] Please see Figure 1 The diagram shows a flowchart of an adaptive grid connection method for energy storage that takes into account the entire transient process of the power grid.

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

[0042] Step S101: Perform small-signal modeling on the frequency variation of the network structure to obtain the first model.

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

[0044]

[0045] In the formula, s is the Laplace operator;

[0046] Rearranging equation (1), we get:

[0047]

[0048] Assumption Then equation (2) can be rewritten as:

[0049]

[0050] The damping coefficient is calculated using the following expression:

[0051]

[0052] In the formula, m p P has no practical meaning. max f is the maximum active power that the VSG can provide. max f is the maximum allowable frequency deviation in IM. min This represents the minimum allowed frequency deviation in IM;

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

[0054]

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

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

[0057]

[0058] In the formula, δ represents the frequency deviation;

[0059] The QV droop coefficient is calculated using the following expression:

[0060]

[0061] In the formula, K pq Let V be the droop coefficient of QV. max V is the maximum permissible voltage deviation specified in the power grid specifications. min Q is the minimum permissible voltage deviation specified in the power grid standard. max This represents 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 to 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 a grid-controlled system (GCM), the primary control objective of a voltage regulator (VSG) is to regulate its output active and reactive power to the desired reference command. To further investigate the performance of the VSG in a GCM and how grid impedance parameters affect its performance, a small-signal model is constructed. Based on the inherent power flow coupling, the small-signal model is derived below, followed by stability analysis.

[0063] Step S102: Perform small-signal modeling on the power flow to obtain the second model.

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

[0065]

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

[0067] To study the stability characteristics and dynamic performance of VSG, small-signal models of active power and reactive power injected into the grid by VSG are established, with the following expressions:

[0068]

[0069] In the formula, ΔP pcc The deviation of active power, ΔQ pcc K represents the deviation in reactive power. 11 K 12 K 21 K 22 Neither has any practical meaning, Δθ ij For the angle deviation, ΔV i For voltage amplitude deviation, V i0 Let θ be the steady-state effective value of the PCC line-to-ground voltage. ij0 The power angle at the steady-state point;

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

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

[0072]

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

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

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

[0076]

[0077] Power angle deviation Δθ ij Voltage amplitude deviation ΔV i Deviation of reference active power 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] Rewritten as:

[0081]

[0082] Substituting equation (18) into equation (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 real meaning;

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

[0089] To achieve good dynamic effects, assume:

[0090]

[0091] In the formula, ω n Let ζ be the natural frequency and ζ be the damping ratio.

[0092] By substituting H in equation (20) in equation (25) 11 (s), then in the obtained equations, use G from equations (14) and (15) p (s), G q (s) substitution yields:

[0093]

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

[0095]

[0096] definition:

[0097]

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

[0099]

[0100] choose:

[0101]

[0102] We can obtain:

[0103]

[0104] Therefore, due to the cross-coupling term K 12 K 21 It is not dominant, i.e., |K 12 K 21 |≤|K 11 K 22 |, from equation (31), we can deduce that 0 ≤ σ ≤ 1, therefore 0 ≤ γ ≤ 1. The result is that, 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 practical meaning, M=K 11 K 22 -K 12 K 21 K 11 For, ω n The rated angular frequency;

[0107]

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

[0109] The above demonstrates that in order to adjust the VSG to cope with both strong and weak power grids, it is essential to understand the grid impedance information in advance. However, a key challenge is that grid impedance is time-varying; using only fixed values ​​for design will hinder optimal design. Therefore, accurate control can only be achieved based on the actual values ​​of the grid impedance.

[0110] To address this issue, an online GIE algorithm utilizing the inverter's own capabilities can be used. This approach is cost-effective because it requires no 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 inverter control loop. These algorithms are generally classified into three categories: active, passive, and hybrid techniques. Single-frequency injection-based GIE technology has shown very accurate results when the estimation time and disturbance amplitude are well-designed. Therefore, this paper selects online active GIE based on 75Hz injection. To avoid estimation errors caused by background intermodulation / subharmonics in the grid voltage, the injection / estimation time is set to 200 milliseconds. This allows for accurate measurements using a resolution of 5Hz.

[0112] To address the impact of disturbance currents on power quality and the trade-off between active and passive techniques, this application proposes a novel algorithm that automatically triggers grid impedance only when necessary. This significantly reduces the potential adverse effects of disturbance amplitude on power quality. Furthermore, to ensure rapid and accurate estimation of grid impedance, the disturbance current is generated at 25Hz within the dq reference frame and added to the current reference values ​​id-ref and iq-ref, thereby leveraging the fast response of the inner loop to quickly track the disturbance current.

[0113] Simultaneously, when injecting id-inj and iq-inj, record the current and voltage responses (V) of phases A, B, or C at PCC. res (75Hz), i res (75Hz)). Then, the fundamental frequency grid impedance Zg(50Hz) is estimated by approximating its value as Zg(75Hz), as shown in Equation (39).

[0114]

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

[0116] The adaptive strategy is specifically as follows:

[0117] When the inverter is started, if the inverter is running in IM or GCM and AVSG is disabled, the first control parameters of the VSG-based inverter designed by Equations (4), (6) and (8) are used.

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

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

[0120] The control parameters of the VSG base inverter are recalculated based on the updated impedance value, and based on the recalculated J and D... p K pq and K iq Adjust and control the grid-type converter.

[0121] In summary, the method presented in this application analyzes the inherent coupling between active and reactive power and its dependence on grid conditions (such as short-circuit ratio, grid impedance ratio Xg / Rg, and the wide variation in grid impedance). Subsequently, an adaptive VSG (AVSG) control strategy based on online grid impedance estimation is proposed to ensure robust operation of the VSG under both strong and weak grid conditions. This technique allows the operator to specify the desired steady-state time and damping ratio of the output power. To estimate 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 into the AVSG control loop. Compared to traditional controller design methods based on fixed parameters, AVSG can achieve the desired performance under different grid conditions, such as no oscillations, specified steady-state time, and minimal overshoot.

[0122] Please see Figure 2 The diagram shows a structural block diagram of a flexible control device for a grid-type converter according to this application.

[0123] like Figure 2 As shown, the flexible control device 200 for grid-type converters 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 variation of the network structure to obtain the first model;

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

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

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

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

[0129] Equation (8) is: K pq v is the QV droop coefficient. max v is the maximum permissible voltage deviation specified in the power grid specifications. min Q is the minimum permissible voltage deviation specified in the power grid standard. max This represents 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 base inverter are calculated according to equations (36), (37), (34) and (38), respectively. The second control parameters include J and D. p K pq and K iq Equation (36) is: K 11 No practical meaning, M=K 11 K 22 -K 12 K 21 K 11 For, ω n The rated angular frequency;

[0131] Equation (37) is: ζ represents damping;

[0132] Equation (34) is: K 22 It has no real meaning;

[0133] Equation (38) is:

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

[0135] The control parameters of the VSG base inverter are recalculated based on the updated impedance value, and based on the recalculated J and D... p K pq and D iq Adjust and control the grid-type converter.

[0136] It should be understood that Figure 2 The modules and references described in the document Figure 1 The steps described in the text correspond to those in the method described above. Therefore, the operations, features, and corresponding technical effects described above also apply to the method described in the text. Figure 2 The various modules in the document will not be described in detail here.

[0137] In other embodiments, the present invention also provides a computer-readable storage medium having a computer program stored thereon, wherein when the program instructions are executed by a processor, the processor performs the flexible control method for the grid-type converter in any of the above method embodiments.

[0138] In one embodiment, the computer-readable storage medium of the present invention stores computer-executable instructions, which are configured as follows:

[0139] Small-signal modeling is performed on the frequency variation of the network structure to obtain the first model;

[0140] By modeling the tidal current using small signals, a second model is obtained;

[0141] Based on the first model and the second model, a preset adaptive strategy is used to adjust and control the grid-type converter, wherein the adaptive strategy specifically includes:

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

[0143] Equation (6) is: J is the inertia coefficient of VSG, T VSGLet ω be the time constant of VSG. o The rated angular frequency of the power grid;

[0144] Equation (8) is: K pq Let V be the droop coefficient of QV. max V is the maximum permissible voltage deviation specified in the power grid specifications. min Q is the minimum permissible voltage deviation specified in the power grid standard. max This represents 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 base inverter are calculated according to equations (36), (37), (34) and (38), respectively. The second control parameters include J and D. p K pq and K iq Equation (36) is: K 11 No practical meaning, M=K 11 K 22 -K 12 K 21 K 11 For, ω n The rated angular frequency;

[0146] Equation (37) is: ζ represents damping;

[0147] Equation (34) is: K 22 It has no real meaning;

[0148] Equation (38) is:

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

[0150] The control parameters of the VSG base inverter are recalculated based on the updated impedance value, and based on the recalculated J and D... p K pq and K iq Adjust and control the grid-type converter.

[0151] Computer-readable storage media may include a stored program area and a stored data area, wherein the stored program area may store an operating system and an application program required for at least one function; the stored data area may store data created based on the use of the network-type converter flexible control device, etc. Furthermore, the computer-readable storage medium may include high-speed random access memory, and may also include memory, such as at least one disk storage device, flash memory device, or other non-volatile solid-state storage device. In some embodiments, the computer-readable storage medium may optionally include memory remotely disposed relative to a processor, and these remote memories may be connected to the network-type converter flexible control device via a network. Examples of such networks include, but are not limited to, the Internet, corporate intranets, local area networks, mobile communication networks, and combinations thereof.

[0152] Figure 3 This is a schematic diagram of the structure of the electronic device provided in the 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, memory 320, input device 330, and output device 340 can be connected via a bus or other means. Figure 3 Taking a bus connection as an example, the memory 320 is the computer-readable storage medium described above. The processor 310 executes various server functions and data processing by running non-volatile software programs, instructions, and modules stored in the memory 320, thereby implementing the flexible control method for the grid-type converter described in the above embodiment. The input device 330 can receive input digital or character information and generate key signal inputs related to user settings and function control of the flexible control device for the grid-type converter. The output device 340 may include a display screen or other display device.

[0153] The aforementioned electronic device can execute the method provided in the embodiments of the present invention, and has the corresponding functional modules and beneficial effects for executing the method. Technical details not described in detail in this embodiment can be found in the method provided in the embodiments of the present invention.

[0154] In one implementation, the above-described electronic device is used in a flexible control device for a grid-connected converter, serving as a client, and includes: 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, the instructions being executed by the at least one processor to enable the at least one processor to:

[0155] Small-signal modeling is performed on the frequency variation of the network structure to obtain the first model;

[0156] By modeling the tidal current using small signals, a second model is obtained;

[0157] Based on the first model and the second model, a preset adaptive strategy is used to adjust and control the grid-type converter, wherein the adaptive strategy specifically includes:

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

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

[0160] Equation (8) is: K pq Let V be the droop coefficient of QV. max V is the maximum permissible voltage deviation specified in the power grid specifications. min Q is the minimum permissible voltage deviation specified in the power grid standard. max This represents 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 base inverter are calculated according to equations (36), (37), (34) and (38), respectively. The second control parameters include J and D. p K pq and K iq Equation (36) is: K 11 No practical meaning, M=K 11 K 22 -K 12 K 21 K 11 For, ω n The rated angular frequency;

[0162] Equation (37) is: ζ represents damping;

[0163] Equation (34) is: K 22 It has no real meaning;

[0164] Equation (38) is:

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

[0166] The control parameters of the VSG base inverter are recalculated based on the updated impedance value, and based on the recalculated J and D... p K pq and K iq Adjust and control the grid-type converter.

[0167] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus necessary general-purpose hardware platforms, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solutions, in essence or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., including several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods of various embodiments or some parts of embodiments.

[0168] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; 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; and these 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 adaptive grid connection of energy storage considering the entire transient process of the power grid, characterized in that, include: Small-signal modeling is performed on the frequency variation of the network structure to obtain the first model; By modeling the tidal current using small signals, a second model is obtained; Based on the first model and the second model, a preset adaptive strategy is used to adjust and control the grid-type converter, wherein the adaptive strategy specifically includes: When the inverter starts up, if the inverter is operating in IM or GCM and AVSG is disabled, the first control parameters of the VSG-based inverter designed by equations (4), (6) and (8) are used, where equation (4) is: , The damping coefficient is... , and These are the maximum and minimum allowed frequency deviations in the IM, respectively. The maximum active power that the VSG can provide; Equation (6) is: , The inertia coefficient of VSG, The time constant of VSG, The rated angular frequency of the power grid; Equation (8) is: , This is the QV droop coefficient. The maximum permissible voltage deviation as specified in the power grid specifications. This refers to the minimum permissible voltage deviation specified in the power grid specifications. This represents the maximum reactive power. When AVSG is enabled, the GIE algorithm will be activated to initialize the resistor. and reactance The impedance value is calculated, and the second control parameters of the VSG base inverter are calculated according to equations (36), (37), (34), and (38), respectively. The second control parameters include... , , and Equation (36) is: , , It has no real meaning. , The rated angular frequency; Equation (37) is: , For damping; Equation (34) is: , It has no real meaning; Equation (38) is: ; Each time the power reference command changes, an enable signal is generated, and the impedance value is updated based on the enable signal, wherein the enable signal includes a delay time equal to the time required by the GIE algorithm; The control parameters of the VSG base inverter are recalculated based on the updated impedance value, and the recalculated parameters are used to determine the control parameters of the VSG base inverter. , , and Adjust and control the grid-type converter.

2. The adaptive grid connection method for energy storage considering the entire transient process of the power grid as described in claim 1, characterized in that, The method of performing small-signal modeling on the frequency variation of the network structure to obtain the first model includes: Ignoring line losses, from the perspective of load changes to angular frequency change The small-signal transfer function is derived as follows: ，（1） In the formula, For the Laplace operator; Rearranging equation (1), we get: ，（2） Assumption Then equation (2) can be rewritten as: ，（3） The damping coefficient is calculated using the following expression: ，（4） ，（5） In the formula, It has no real meaning. The maximum active power that VSG can provide. This represents the maximum allowable frequency deviation in IM. This represents the minimum allowed frequency deviation in IM; Based on equations (2) and (3), the inertia coefficient of VSG is calculated, and its expression is: ，（6） In the formula, The inertia coefficient of VSG, The time constant of VSG, The rated angular frequency of the power grid; The Bode plot of the open-loop transfer function of VSG is expressed as follows: ，（7） In the formula, This represents the frequency deviation. The QV droop coefficient is calculated using the following expression: ，（8） In the formula, This is the QV droop coefficient. The maximum permissible voltage deviation as specified in the power grid specifications. This refers to the minimum permissible voltage deviation specified in the power grid specifications. This represents the maximum reactive power.

3. The adaptive grid connection method for energy storage considering the entire transient process of the power grid as described in claim 1, characterized in that, The method of performing small-signal modeling on the power flow to obtain the second model includes: The expression for calculating the active and reactive power injected into the grid by the VSG is: ，（9） ，（10） In the formula, The active power injected into the grid by the VSG. The resistance of the power grid, This is the effective value of the PCC voltage. This is the effective value of the grid-side voltage. for and The phase angle between them For the inductance of the power grid, The reactive power injected into the grid by the VSG; Establish small-signal models for the active power and reactive power injected into the grid by the VSG, with the following expressions: ，（11） ，（12） In the formula, For the deviation of active power, This refers to the deviation in reactive power. , , , None of them have any real meaning. For the angle of work deviation, For voltage amplitude deviation, This represents the steady-state RMS value of the PCC line-to-ground voltage. The power angle at the steady-state point; The open-loop transfer function of the active power loop, taking into account the impedance of the power grid and lines, is expressed as follows: ，（13） In the formula, , All are open-loop transfer functions. The deviation of PCC active power, For reference, the deviation of active power, This refers to the deviation of the PCC reactive power.

4. A flexible control device for a grid-type converter, characterized in that, include: The first modeling module is configured to perform small-signal modeling on the frequency variation of the network structure to obtain the first model; The second modeling module is configured to perform small-signal modeling on the power flow to obtain the second model; The control module is configured to adjust and control the grid-type converter using a preset adaptive strategy based on the first model and the second model, wherein the adaptive strategy specifically includes: When the inverter starts up, if the inverter is operating in IM or GCM and AVSG is disabled, the first control parameters of the VSG-based inverter designed by equations (4), (6) and (8) are used, where equation (4) is: , The damping coefficient is... , and These are the maximum and minimum allowed frequency deviations in the IM, respectively. The maximum active power that the VSG can provide; Equation (6) is: , The inertia coefficient of VSG, The time constant of VSG, The rated angular frequency of the power grid; Equation (8) is: , This is the QV droop coefficient. The maximum permissible voltage deviation as specified in the power grid specifications. This refers to the minimum permissible voltage deviation specified in the power grid specifications. This represents the maximum reactive power. When AVSG is enabled, the GIE algorithm will be activated to initialize the resistor. and reactance The impedance value is calculated, and the second control parameters of the VSG base inverter are calculated according to equations (36), (37), (34), and (38), respectively. The second control parameters include... , , and Equation (36) is: , , It has no real meaning. , The rated angular frequency; Equation (37) is: , For damping; Equation (34) is: , It has no real meaning; Equation (38) is: ; Each time the power reference command changes, an enable signal is generated, and the impedance value is updated based on the enable signal, wherein the enable signal includes a delay time equal to the time required by the GIE algorithm; The control parameters of the VSG base inverter are recalculated based on the updated impedance value, and the recalculated parameters are used to determine the control parameters of the VSG base inverter. , , and Adjust and control the grid-type 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 to enable the at least one processor to perform the method according to 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 the processor, it implements the method according to any one of claims 1 to 3.

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