Self-adaptive current-limiting control method for network-building type energy storage converter under symmetric fault of power grid and related device

Abstract

The invention discloses a self-adaptive current-limiting control method and related device for a network construction type energy storage converter under a symmetric fault of a power grid, and belongs to the technical field of network construction type energy storage converter control, and the method comprises the steps: constructing a corresponding fault current dynamic response model based on the network construction type energy storage converter under the symmetric fault of the power grid; generating a self-adaptive current-limiting control strategy based on the voltage drop depth of the power grid; wherein the self-adaptive current-limiting control strategy comprises the steps of carrying out overcurrent steady-state component suppression based on a phasor current-limiting method and carrying out overcurrent transient-state component suppression based on a virtual impedance control method, and self-adaptively adjusting a power instruction to meet a system support requirement in a current-limiting process; a fault current dynamic response model is solved through a self-adaptive current-limiting control strategy, a current-limiting control scheme is obtained, it can be ensured that the converter maintains the networking characteristic in the fault period, steady-state and transient overcurrent is effectively restrained, output current is strictly limited within a safety threshold value, and transient stability of a system is maintained.

Description

Technical Field

[0001] This invention belongs to the field of grid-type energy storage converter control technology, and particularly relates to an adaptive current limiting control method and related device for grid-type energy storage converter under symmetrical grid faults. Background Technology

[0002] In the global energy structure transition towards a low-carbon model, the installed capacity of new energy sources, primarily wind and solar power, continues to grow. Against this backdrop, "new energy + energy storage" systems have become a key supporting technology for achieving "dual carbon" goals. Energy storage converters not only improve the absorption of renewable energy but also enhance the dynamic response characteristics of the power system. In particular, grid-based control strategies, due to their autonomous inertial response and primary frequency regulation capabilities, are gradually becoming a core technology for improving grid stability. However, when a symmetrical short-circuit fault occurs in the grid, grid-based converters face significant challenges such as reduced power margin and increased transient instability risks. Traditional grid-based fault ride-through strategies are difficult to apply directly to such scenarios, and the operation mode switching process may induce secondary instability. Therefore, there is an urgent need to develop highly reliable grid-based fault ride-through control mechanisms.

[0003] Currently, overcurrent suppression strategies for grid-connected converters mainly include control mode switching, virtual impedance control, and current limiting modules. For example, switching grid control to grid-following mode during voltage dips to achieve low-voltage ride-through can lead to a loss of voltage support capability, potentially causing cascading instability under weak grid conditions. Alternatively, virtual impedance current limiting technology can be used. While this method can suppress fault current, its performance is highly dependent on impedance parameter settings, and current surges are easily triggered when impedance is removed, requiring additional control strategies. Another approach is current saturation control, which, although simple to implement, can alter the converter's operating state under large disturbances, potentially inducing transient overcurrents or system instability, and even damaging components. Summary of the Invention

[0004] The purpose of this invention is to provide an adaptive current limiting control method and related device for grid-type energy storage converters under symmetrical grid faults, which can ensure that the converter maintains grid characteristics during the fault, effectively suppress steady-state and transient overcurrents, strictly limit the output current within a safe threshold, and maintain system transient stability.

[0005] To achieve the above objectives, the present invention is implemented using the following technical solution:

[0006] In a first aspect, the present invention provides an adaptive current limiting control method for a grid-type energy storage converter under symmetrical grid faults, comprising:

[0007] Based on the grid-type energy storage converter under symmetrical grid faults, a corresponding dynamic response model for fault current is constructed.

[0008] Based on the voltage dip depth of the power grid, an adaptive current limiting control strategy is generated. The adaptive current limiting control strategy includes: suppressing the steady-state component of overcurrent based on the phasor current limiting method and suppressing the transient component of overcurrent based on the virtual impedance control method, and adaptively adjusting the power command to meet the system support requirements during the current limiting process.

[0009] The current limiting control scheme is obtained by solving the dynamic response model of the fault current through an adaptive current limiting control strategy.

[0010] Optionally, the fault current dynamic response model characterizes the dynamic relationship between the fault current and the internal potential, grid voltage, and virtual impedance.

[0011] Optionally, the phasor current limiting method includes: projecting the internal potential and the voltage difference between the fault point onto the virtual synchronous machine rotor coordinate system, and limiting the steady-state component of the fault current by limiting the voltage difference amplitude to not exceed a preset threshold.

[0012] Optionally, the virtual impedance control method includes: increasing the virtual inductance value in the early stage of the fault to suppress transient current surges, and gradually reducing the virtual inductance while maintaining the virtual resistance in the steady-state stage of the fault.

[0013] Optionally, the method for adaptively adjusting the power command includes: maintaining the original active power command when the grid voltage drop depth is less than a first voltage threshold; reducing the active power command value and increasing the reactive power command value when the drop depth is between the first voltage threshold and a second voltage threshold; and limiting the active power output and supporting the grid with reactive power when the drop depth is greater than the second voltage threshold.

[0014] Optionally, when the drop depth is between the first voltage threshold and the second voltage threshold, the active power command value is adjusted using the following formula:

[0015] ,

[0016] in, This is the active power command value after the fault. This is the active power command value before the fault. This refers to the voltage drop depth. The first voltage threshold, This is the second voltage threshold.

[0017] Optionally, when the drop depth is between the first voltage threshold and the second voltage threshold, the reactive power command value is adjusted using the following formula:

[0018] ,

[0019] ,

[0020] in, This is the reactive power command value after the fault. For coefficients, This refers to the permissible apparent power after a grid fault. Rated apparent power, The voltage amplitude of the power grid. This is the rated voltage amplitude.

[0021] Optionally, the current limiting control scheme achieves closed-loop regulation through a sliding mode controller or a PI controller, and the controlled objects include the amplitude and phase of the converter output voltage.

[0022] Secondly, the present invention provides an adaptive current limiting control device for a grid-type energy storage converter under symmetrical grid faults, comprising:

[0023] Problem model building module: used to build the corresponding dynamic response model of fault current for grid-type energy storage converters under symmetrical grid faults;

[0024] Control strategy generation module: used to generate adaptive current limiting control strategy based on grid voltage drop depth; wherein, the adaptive current limiting control strategy includes: overcurrent steady-state component suppression based on phasor current limiting method and overcurrent transient component suppression based on virtual impedance control method, and adaptively adjusts power command to meet system support requirements during current limiting process.

[0025] Control scheme generation module: used to solve the dynamic response model of fault current through adaptive current limiting control strategy to obtain current limiting control scheme.

[0026] Thirdly, the present invention provides a computer storage medium storing a computer program thereon, which, when executed by a processor, implements the adaptive current limiting control method for grid-type energy storage converters under symmetrical grid faults as described in any of the first aspects.

[0027] Compared with existing technologies, the beneficial effects achieved by this invention are as follows: This invention constructs a steady-state component suppression scheme based on phasor current limiting and a transient component suppression scheme based on virtual impedance control for different voltage dip levels. By changing the time constant and system impedance characteristics through virtual impedance, it effectively suppresses transient overcurrents and accelerates their decay. Phasor current limiting effectively suppresses the steady-state component of fault overcurrents. Simultaneously, an adaptive adjustment mechanism is incorporated to optimize power commands. Adjustment of the active power reference value effectively prevents system instability caused by large disturbances. While maintaining system stability, the reactive power reference value is adjusted according to the voltage dip level. During faults, it meets the transient power angle stability requirements while ensuring the system's reactive power support capability. This invention is applicable to various power systems with grid-type energy storage converters, especially in scenarios such as new energy grid connection and microgrid control, enhancing the system's fault ride-through capability and playing a significant role in ensuring the safe and stable operation of the power system. Attached Figure Description

[0028] Figure 1 The diagram shown is a flowchart of an adaptive current limiting control method for a grid-type energy storage converter under symmetrical grid faults, according to one embodiment of the present invention.

[0029] Figure 2 The diagram shown is an equivalent circuit diagram after introducing virtual impedance in one embodiment of the present invention.

[0030] Figure 3 The diagram shown is a schematic of the overcurrent suppression strategy for the energy storage converter in one embodiment of the present invention.

[0031] Figure 4 The diagram shown is a flowchart of an overcurrent suppression strategy for an energy storage converter in one embodiment of the present invention.

[0032] Figure 5 The diagram shown is a schematic representation of the output current in one embodiment of the present invention without overcurrent suppression measures.

[0033] Figure 6 The diagram shown is a schematic representation of the output current using steady-state overcurrent suppression measures in one embodiment of the present invention.

[0034] Figure 7 The diagram shown is a schematic representation of the output power using steady-state overcurrent suppression measures in one embodiment of the present invention.

[0035] Figure 8 The diagram shown is a schematic representation of the output current using steady-state and transient overcurrent suppression measures in one embodiment of the present invention.

[0036] Figure 9 The diagram shown is a schematic of the output power using steady-state and transient overcurrent suppression measures in one embodiment of the present invention. Detailed Implementation

[0037] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0038] Example 1

[0039] like Figure 1 As shown, this embodiment proposes an adaptive current-limiting control method for grid-connected energy storage converters under symmetrical grid faults. For different voltage dip levels, it constructs a steady-state component suppression scheme based on phasor current limiting and a transient component suppression scheme based on virtual impedance control, respectively. Simultaneously, an adaptive adjustment mechanism is incorporated to optimize power commands based on different grid voltage dips, aiming to meet transient power angle stability requirements while ensuring the system's reactive power support capability. Specifically, the method includes the following steps:

[0040] Step S1: By analyzing the basic principles of grid control of energy storage converters, the fault current under symmetrical grid faults is analyzed, and its dynamic response model is established.

[0041] Based on the virtual synchronous machine control principle, an equivalent voltage source model of a grid-connected energy storage converter under symmetrical grid fault conditions is constructed. This model uses the internal potential of the grid-connected energy storage converter as the reference voltage source, and the virtual impedance and the grid equivalent impedance form the total impedance path, creating a flow loop for the fault current. By analyzing the phase difference and amplitude difference between the internal potential and the grid connection point voltage at the instant of fault occurrence, a dynamic response model of the fault current is constructed to characterize the different response characteristics of the fault current in the transient and steady-state stages. This dynamic response model can reflect the nonlinear characteristics of the fault current changing over time, including the peak inrush current at the initial stage of the fault, the continuous overcurrent in the steady-state stage, and the current recovery process after fault clearance.

[0042] Step S2: To address the overcurrent characteristics under a short-circuit fault in the power grid, a phasor current limiting method is used to suppress the steady-state component of the overcurrent. The core mechanism of phasor current limiting is to suppress the fault current by limiting the voltage difference between the internal potential and the fault point. However, in practical applications, the voltage difference between the internal potential and the fault point is difficult to measure directly, thus making direct limitation impossible. This application selects the virtual synchronous machine rotor coordinate system as the reference coordinate system, synchronously projecting the grid voltage and the virtual synchronous machine current onto this coordinate system. In the rotor coordinate system, by limiting the voltage difference between the internal potential and the converter terminal voltage, indirect limitation of the voltage difference between the internal potential and the fault point is achieved.

[0043] The phasor current limiting method is based on a virtual synchronous machine rotating coordinate system. It projects the internal potential of the converter and the grid connection point voltage onto the same rotating coordinate system to obtain the voltage difference vector between the two. By setting the maximum allowable amplitude threshold of the voltage difference vector, the deviation range between the internal potential and the grid voltage is limited, thereby indirectly controlling the steady-state component of the fault current.

[0044] Step S3: In order to limit the transient impact current component of the system during a grid short-circuit fault, virtual impedance control is introduced to suppress transient overcurrent impact and accelerate short-circuit current decay, based on the overcurrent characteristics under grid short-circuit fault.

[0045] During the fault current suppression process, the equivalent impedance characteristics of the converter output port are changed by dynamically adjusting the virtual resistance and virtual inductance. Specifically, this includes: in the early stage of the fault, rapidly increasing the virtual inductance value to increase the system impedance, suppress the current rise rate, and reduce the peak inrush current; in the steady-state stage of the fault, appropriately increasing the virtual resistance value to limit the steady-state current amplitude, while avoiding oscillation caused by excessively low system damping; the virtual impedance parameters are adjusted in real time according to the depth of the grid voltage drop, the deeper the drop, the larger the virtual impedance value, thereby achieving adaptive suppression of the fault current.

[0046] Step S4: An adaptive adjustment mechanism based on voltage sag depth is proposed. The power command and virtual impedance value during the fault period are dynamically adjusted according to the voltage sag depth of the grid. The reactive power support requirements are met and the system stability is maintained while ensuring the current limiting effect.

[0047] Example 2

[0048] Based on Example 1, this example also includes the following design, which includes the simulation verification process of the adaptive current limiting control strategy of the grid-type energy storage converter using the method of the present invention.

[0049] In the simulation verification process, a grid-connected simulation model of a grid-connected energy storage converter was constructed. Initially, the grid-connected converter operated at its rated state, with an output active power of 50kW and reactive power of 0var. At 0.5 s, the grid voltage dropped, lasting for 800 ms, and the fault was cleared at 1.3 s. Simulation comparisons were conducted through three sets of control experiments (operation without suppression strategy, operation with steady-state overcurrent suppression strategy, and operation with steady-state + transient overcurrent suppression strategy).

[0050] The control strategy of this invention mainly includes two parts: one is an overcurrent suppression strategy, which uses phasor current limiting to suppress the steady-state component of overcurrent and virtual impedance to suppress the transient component of overcurrent; the other part is an adaptive adjustment mechanism based on the grid voltage sag depth, which dynamically adjusts the power command and virtual impedance value during the fault according to the grid voltage sag depth. Figure 2The diagram shows the overcurrent suppression strategy that simultaneously employs phasor current limiting and virtual impedance control. Finally, the superiority of the strategy is verified through simulation.

[0051] (1) Overcurrent suppression strategy

[0052] To address the overcurrent characteristics under power grid short-circuit faults, this application employs phasor current limiting to suppress the steady-state component of the overcurrent and virtual impedance to suppress the transient component of the overcurrent.

[0053] The core mechanism of phasor current limiting is to suppress fault current by limiting the voltage difference between the internal potential and the fault point. However, in practical applications, the voltage difference between the internal potential and the fault point is difficult to measure directly, and therefore cannot be directly limited. This application selects the virtual synchronous machine rotor coordinate system as the reference coordinate system, and synchronously projects the grid voltage and the virtual synchronous machine current into this coordinate system. Under the virtual synchronous machine rotor coordinate system, the voltage difference between the internal potential and the fault point is indirectly limited by limiting the voltage difference between the internal potential and the converter terminal voltage.

[0054] When the output current is projected onto the internal potential reference coordinate system, the output current must satisfy the following constraint:

[0055] (1)

[0056] in, The maximum allowable current along the d-axis represents the maximum permissible output current in the d-axis direction of the virtual synchronous machine rotor coordinate system. The d-axis component represents the grid current, which is the current value projected onto the d-axis of the virtual synchronous machine rotor coordinate system. This represents the maximum allowable current along the q-axis, which is the maximum allowable output current in the q-axis direction of the virtual synchronous machine rotor coordinate system. Let be the q-axis component of the grid current, which is the current value projected onto the q-axis of the virtual synchronous machine rotor coordinate system. The maximum amplitude of the output current represents the effective value or the maximum limit value of the amplitude of the output current, used to constrain the overall magnitude of the current.

[0057] From Equation 1, the constraint condition for the internal potential of the virtual synchronous machine can be obtained (Equation 2):

[0058] (2)

[0059] in, This represents the maximum internal potential along the d-axis of the virtual synchronizer, which is the upper limit of the allowable internal potential in the d-axis direction. This represents the minimum internal potential along the d-axis of the virtual synchronizer, which is the lower limit of the allowable internal potential in the d-axis direction. This represents the d-axis component of the grid voltage, i.e., the voltage value projected onto the d-axis of the virtual synchronous machine rotor coordinate system. The electrical angular velocity of the virtual synchronizer reflects its rotational electrical speed. For filtering inductors, This represents the maximum value of the q-axis component of the grid current, and the maximum permissible value of the grid current in the q-axis direction. This represents the maximum internal potential of the virtual synchronizer along the q-axis, and the upper limit of the allowable internal potential in the q-axis direction. This represents the minimum internal potential along the q-axis of the virtual synchronizer, and the lower limit of the allowable internal potential in the q-axis direction. The grid voltage component on the q-axis represents the voltage value projected onto the q-axis of the virtual synchronous machine rotor coordinate system. This represents the maximum value of the d-axis component of the grid current, and the maximum permissible value of the grid current in the d-axis direction. Phasor current limiting does not affect the dynamic characteristics of the virtual synchronous machine during normal operation, nor does it affect the operating point of the virtual synchronous machine. However, phasor current limiting is designed based on the circuit's steady-state equations and does not consider the transient components of the current; therefore, it cannot limit the transient inrush current component of the virtual synchronous machine during grid faults.

[0060] To limit the transient inrush current component of the virtual synchronous machine during grid faults, this application introduces virtual impedance control to suppress transient overcurrent impacts and accelerate short-circuit current decay. The equivalent circuit diagram of the grid-connected converter after introducing virtual impedance is shown below. Figure 3 As shown in Equation 3, the inverter modulation wave dq-axis voltage can be obtained by subtracting the voltage drop of the virtual impedance from the internal potential after simulating the stator impedance using a virtual impedance, as shown in Equation 3.

[0061] (3)

[0062] in, The d-axis reference voltage. This is the q-axis reference voltage. , These are the virtual resistance and virtual reactance of the virtual synchronous control, respectively. This formula is the reference voltage expression after the virtual impedance is introduced into the virtual synchronous machine. and For output current The value after Parker transformation This is the internal potential of the virtual synchronous machine.

[0063] (2) Adaptive adjustment mechanism

[0064] Based on the characteristics of phasor current limiting and virtual impedance current limiting, this application combines the two to suppress steady-state fault current and transient inrush current, respectively. Furthermore, it proposes an adaptive adjustment mechanism based on voltage sag depth, dynamically adjusting the power command and virtual impedance value during faults according to the grid voltage sag depth, thus ensuring reactive power support and maintaining system stability while ensuring current limiting effectiveness.

[0065] When a power grid fault occurs, the active power output of the virtual synchronous machine decreases and falls below its active power command (which is physically equivalent to the mechanical power input of a traditional synchronous generator). This causes the virtual synchronous machine rotor to accelerate and its internal frequency to rise rapidly, leading to an increase in the power angle. According to the equal area rule, if the accelerating area is greater than the maximum decelerating area, it will cause transient power angle instability problems in the virtual synchronous machine.

[0066] During grid faults, reducing the active power command value of the virtual synchronous machine can decrease its acceleration area while significantly increasing the maximum deceleration area. This application is based on regulating the active power command during voltage sag depth faults during grid faults:

[0067] (4)

[0068] In the formula: , These are the active power command values ​​before and after the fault, respectively. This refers to the voltage drop depth. The first voltage threshold, This is the second voltage threshold. (This is from an example.) The value is 0.2pu. Take the value 0.9pu and substitute it. The calculation formula (4) is as follows: .

[0069] According to national grid connection standards, when the grid voltage drops, the inverter needs to inject reactive power into the grid to support it. This application adopts Formula 5 for reactive power regulation command:

[0070] (5)

[0071] (6)

[0072] In the formula, Reactive power command value after a fault This refers to the permissible apparent power after a grid fault. This is the rated voltage amplitude; This is the rated apparent power; This represents the grid voltage amplitude. The value is 0.2pu. Take the value 0.9pu and substitute it. The calculation formula (5) is as follows: .

[0073] In traditional fixed virtual impedance control, the system still faces overcurrent or instability problems under large disturbances. While a smaller virtual impedance can ensure system stability, the inrush current during disturbances may exceed the converter's tolerance; while a larger virtual impedance can limit the current to the inverter's maximum limit, it is prone to system divergence and instability.

[0074] During grid voltage dips, different virtual impedances and control strategies need to be designed based on the dip conditions. This application uses Equations 7 and 8 to calculate the virtual reactance. With virtual resistance :

[0075] (7)

[0076] (8)

[0077] In the formula: For proportional gain; This is the impedance control coefficient.

[0078] During the process of the grid voltage recovering from a fault state to normal operating conditions, transient inrush currents will still be generated during the recovery phase because the potential within the system has changed during the fault.

[0079] A larger virtual inductance primarily suppresses steady-state current and provides sufficient reactive power support, while a smaller time constant (i.e., a larger impedance-to-inductance ratio) helps reduce transient current. Therefore, this application immediately disconnects the virtual inductance added during the voltage dip after voltage recovery, and the virtual resistance is controlled by an exponential decay function to avoid recovery transient current caused by the sudden removal of the virtual resistance. Equation 9 is the expression for the virtual impedance changing with time.

[0080] (9)

[0081] in, For a moment virtual impedance, This is the virtual impedance attenuation coefficient. This is the virtual impedance under voltage drop. It is an exponentially decaying function. This is the starting point of the fault or virtual impedance effect, and also the starting time point of the virtual impedance control sequence. This is the moment when the virtual inductance switches to the virtual resistance (fault recovery moment), used to switch the type of virtual impedance. The moment when the virtual resistance begins to decay exponentially (i.e. ). Due to The transient current has decayed completely, therefore during the exit period During this period, it becomes a virtual resistance value. , Then, an exponential decay method was used to reduce it.

[0082] Based on the above control method, a sliding mode controller or a PI controller is used to control the amplitude and phase of the converter output voltage to achieve closed-loop regulation. The control flow is as follows: Figure 4 As shown.

[0083] Practical application results:

[0084] Initially, the grid-connected converter operates in parallel with the grid, with a set output active power of 50kW and reactive power of 0var. At 0.5s, the grid voltage drops, lasting for 800ms, and at 1.3s, the fault is cleared.

[0085] The three sets of verification and comparison experiments are as follows:

[0086] 1) Without suppression strategy, the grid voltage drops by 50%. The output current without suppression measures is shown below. Figure 8 ,from Figure 5 It can be seen that during the fault period of 0.5~1.3s, the current far exceeds the current during normal operation, with steady-state overcurrent reaching 5.2pu and transient overcurrent as high as 8.3pu.

[0087] 2) A steady-state overcurrent suppression strategy is implemented, resulting in a 50% voltage drop in the mains voltage. The output current after implementing the steady-state overcurrent suppression strategy is shown below. Figure 6 The steady-state overcurrent during the fault was successfully limited to below 1.3 pu, and transient overcurrent was suppressed to some extent. However, the transient overcurrent still exceeded the safety threshold, reaching 1.7 pu. The output power after adopting the steady-state overcurrent suppression strategy is shown in [reference needed]. Figure 7 According to the adaptive power command optimization adopted in this application, the converter generates an additional 15kvar during the fault period to ensure reactive power support for the power grid, which alleviates power fluctuations to a certain extent. The output active power becomes 22.5kW, ensuring the transient stability of the system during the fault period.

[0088] 3) With the addition of a steady-state and transient overcurrent suppression strategy, the grid voltage drops by 70%. The output current after adding the steady-state and transient overcurrent suppression strategy is shown below. Figure 8 The transient inrush current was successfully limited within the safe threshold. The output power after incorporating the steady-state + transient suppression strategy is shown in [reference needed]. Figure 9 During the fault, the converter generates an additional 13.5 kvar, resulting in an active power output of 15 kW.

[0089] Comparing the simulation results of converters without suppression strategies, with steady-state suppression strategies, and with a combination of steady-state and transient suppression strategies, it can be seen that when a grid fault occurs, the steady-state suppression strategy has a significant effect on suppressing steady-state overcurrent during the fault period, and has some effect on the peak transient overcurrent, but not significantly; after adding the transient suppression strategy, the transient overcurrent is significantly suppressed. Simultaneously, using the fault current limiting method described in this application, the power fluctuation of the converter output power is also mitigated, and reactive power is generated to support the grid voltage.

[0090] Example 3

[0091] This embodiment provides an adaptive current limiting control device for a grid-type energy storage converter under symmetrical grid faults, including:

[0092] Problem model building module: used to build the corresponding dynamic response model of fault current for grid-type energy storage converters under symmetrical grid faults;

[0093] Control strategy generation module: used to generate adaptive current limiting control strategy based on grid voltage drop depth; wherein, the adaptive current limiting control strategy includes: overcurrent steady-state component suppression based on phasor current limiting method and overcurrent transient component suppression based on virtual impedance control method, and adaptively adjusts power command to meet system support requirements during current limiting process.

[0094] Control scheme generation module: used to solve the dynamic response model of fault current through adaptive current limiting control strategy to obtain current limiting control scheme.

[0095] The device provided in this embodiment can execute the adaptive current limiting control method for grid-type energy storage converters under symmetrical grid faults provided in either embodiment 1 or embodiment 2, and has the corresponding functional modules and beneficial effects of the method.

[0096] Example 4

[0097] This embodiment provides a computer storage medium storing a computer program. When the computer program is executed by a processor, it implements the adaptive current limiting control method for grid-type energy storage converters under symmetrical grid faults as provided in either embodiment 1 or embodiment 2.

[0098] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0099] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0100] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0101] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0102] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. An adaptive current limiting control method for a grid-type energy storage converter under symmetrical grid faults, characterized in that, include: Based on the grid-type energy storage converter under symmetrical grid faults, a corresponding dynamic response model for fault current is constructed. Based on the voltage dip depth of the power grid, an adaptive current limiting control strategy is generated. The adaptive current limiting control strategy includes: suppressing the steady-state component of overcurrent based on the phasor current limiting method and suppressing the transient component of overcurrent based on the virtual impedance control method, and adaptively adjusting the power command to meet the system support requirements during the current limiting process. The current limiting control scheme is obtained by solving the dynamic response model of the fault current through an adaptive current limiting control strategy.

2. The adaptive current limiting control method for grid-type energy storage converters under symmetrical grid faults according to claim 1, characterized in that, The fault current dynamic response model characterizes the dynamic relationship between fault current and internal potential, grid voltage and virtual impedance.

3. The adaptive current limiting control method for grid-type energy storage converters under symmetrical grid faults according to claim 2, characterized in that, The phasor current limiting method includes: projecting the voltage difference between the internal potential and the fault point onto the virtual synchronous machine rotor coordinate system, and limiting the steady-state component of the fault current by limiting the voltage difference amplitude to not exceed a preset threshold.

4. The adaptive current limiting control method for grid-type energy storage converters under symmetrical grid faults according to claim 2, characterized in that, The virtual impedance control method includes: increasing the virtual inductance value in the early stage of the fault to suppress transient current surges, and gradually reducing the virtual inductance while maintaining the virtual resistance in the steady-state stage of the fault.

5. The adaptive current limiting control method for grid-type energy storage converters under symmetrical grid faults according to claim 2, characterized in that, The method for adaptively adjusting power commands includes: maintaining the original active power command when the grid voltage drop depth is less than a first voltage threshold; reducing the active power command value and increasing the reactive power command value when the drop depth is between the first voltage threshold and a second voltage threshold; and limiting active power output and supporting the grid with reactive power when the drop depth is greater than the second voltage threshold.

6. The adaptive current limiting control method for grid-type energy storage converters under symmetrical grid faults according to claim 5, characterized in that, When the drop depth is between the first voltage threshold and the second voltage threshold, the active power command value is adjusted using the following formula: ， in, This is the active power command value after the fault. This is the active power command value before the fault. This refers to the voltage drop depth. The first voltage threshold, This is the second voltage threshold.

7. The adaptive current limiting control method for grid-type energy storage converters under symmetrical grid faults according to claim 5, characterized in that, When the voltage drop depth is between the first voltage threshold and the second voltage threshold, the reactive power command value is adjusted using the following formula: ， ， in, This is the reactive power command value after the fault. For coefficients, This refers to the permissible apparent power after a grid fault. Rated apparent power, The voltage amplitude of the power grid. This is the rated voltage amplitude.

8. The adaptive current limiting control method for grid-type energy storage converters under symmetrical grid faults according to claim 1, characterized in that, The current limiting control scheme achieves closed-loop regulation through a sliding mode controller or a PI controller, and the controlled objects include the amplitude and phase of the converter output voltage.

9. An adaptive current limiting control device for a grid-type energy storage converter under symmetrical grid faults, characterized in that, include: Problem model building module: used to build the corresponding dynamic response model of fault current for grid-type energy storage converters under symmetrical grid faults; Control strategy generation module: used to generate adaptive current limiting control strategy based on grid voltage drop depth; wherein, the adaptive current limiting control strategy includes: overcurrent steady-state component suppression based on phasor current limiting method and overcurrent transient component suppression based on virtual impedance control method, and adaptively adjusts power command to meet system support requirements during current limiting process. Control scheme generation module: used to solve the dynamic response model of fault current through adaptive current limiting control strategy to obtain current limiting control scheme.

10. A computer storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the adaptive current limiting control method for grid-type energy storage converters under symmetrical grid faults as described in any one of claims 1-8.

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