Method and system for improving transient performance of network construction type energy storage

Abstract

The invention discloses a network construction type energy storage transient performance improving method and system, and the method comprises the steps: dividing a maximum current threshold value of an energy storage current converter in a transient state into a current under a dq coordinate system, calculating the total impedance required by current limiting through combining the component of the A-phase current output by the energy storage current converter on a d axis and the voltage difference between the two ends, setting the virtual impedance, and carrying out the current limiting through the virtual impedance. Virtual impedance is introduced into a current control link to realize over-current limitation; and the current control link outputs voltage, and the output voltage acts on the VSG power control link to realize power angle control. The system comprises a current control module and a power control module. According to the invention, through adaptive adjustment of the virtual impedance and correction of the active power instruction value, the overcurrent is effectively suppressed in the low voltage ride through process, and the power angle of the system is maintained to be stable, so that the transient performance of the network-forming type energy storage system is improved.

Description

Technical Field

[0001] The present invention belongs to the field of electric power technology, and specifically relates to a method and system for improving the transient performance of grid-type energy storage. Background Art

[0002] With the large-scale grid connection of wind power, photovoltaic power generation units with power electronic converters as interfaces, the grid-forming (GFM) control mode has gradually attracted attention because it can simulate the voltage and frequency characteristics of traditional synchronous generators. However, under large disturbances such as grid short-circuit faults, grid-forming energy storage systems are prone to overcurrent, resulting in system power angle instability and even grid-off risks. Existing research has mostly focused on control mode switching or simply constructing virtual impedance, but has failed to fully consider the balance between low voltage ride-through, overcurrent limitation and power angle stability. Summary of the invention

[0003] The present invention aims to solve the problem in the prior art that the balance among low voltage ride-through, overcurrent limitation and power angle stability is not fully considered, and provides a method and system for improving the transient performance of grid-type energy storage.

[0004] In order to achieve the above object, the present invention adopts the following technical solution:

[0005] A method for improving transient performance of grid-type energy storage, comprising:

[0006] The maximum current threshold of the energy storage converter in the transient state is divided into the current in the dq coordinate system, and the total impedance required for current limiting is calculated by combining the component of the A-phase current output by the energy storage converter on the d-axis and the voltage difference at both ends, and the virtual impedance is set and introduced into the current control link to achieve overcurrent limitation;

[0007] The current control link outputs voltage, and the output voltage acts on the VSG power control link to achieve power angle control.

[0008] A further improvement of the present invention is that the maximum current threshold value I of the energy storage converter in the transient state is set to m Set to: I m =(1+K m )I N Where: K m I is the peak current carrying coefficient of the energy storage converter; N is the rated current of the VSG output.

[0009] The present invention is further improved in that the maximum current threshold of the energy storage converter in the transient state is set, the initial position of the A-phase voltage output by the energy storage converter is coincident with the d-axis in the dq coordinate system, so that the impedance of the line connected to the energy storage converter is approximately equivalent to the d-axis, the d-axis and q-axis components of the required virtual impedance are calculated, and the total impedance required for current limiting is calculated by combining the component of the A-phase current output by the energy storage converter on the d-axis and the voltage difference at both ends. The virtual impedance value Z v By the virtual resistor R v and virtual inductance L v Composition, expressed as: in: Where: Z d , Z q is the virtual impedance Z v The d and q axis components of E d 、E q are the d-axis and q-axis components of the output voltage of the energy storage converter; R eq +jX eq is the equivalent impedance of the external line connected to the energy storage before the fault, R eq is the equivalent resistance, X eq is the equivalent reactance; U gd , U gq are the d-axis and q-axis components of the grid voltage after the fault occurs.

[0010] A further improvement of the present invention is that, according to the set virtual impedance, the steady-state current during the fault period is controlled to be (1+K m )I N At this time, the maximum output current i of the energy storage converter is max It is expressed as: To ensure the stable operation of the energy storage control system during the fault period, the maximum output current i of the energy storage converter is max Need to meet: i max ≤I m ; In order to enable the energy storage converter to withstand the maximum transient current, the virtual impedance is set to meet:

[0011] A further improvement of the present invention is that, when the impedance of the energy storage converter and the external transmission line is set to X, the active power P and reactive power Q output by the energy storage converter VSG are expressed as: Where: E is the VSG output voltage; U is the line voltage connected to the energy storage converter; δ is the VSG system power angle; the difference Δδ between the VSG system power angle and the rated value is expressed as: Where: Δω=ω N -ω is the virtual frequency adjustment amount; ω N is the rated virtual frequency; ΔP is the VSG output active power adjustment; D is the virtual damping; J is the virtual inertia.

[0012] A further improvement of the present invention is that by adjusting the active power reference value and reactive circuit control at the same time, the output characteristics of the VSG can be precisely controlled under a three-phase grounding fault; the reference voltage of the reactive circuit before and after the fault is It is expressed as: Where: n is the reactive power voltage droop coefficient; E ref is the reference voltage before the fault; is the reactive power reference value.

[0013] A further improvement of the present invention is that in order to maintain the transient power angle stability of the VSG, the active power reference value is modified. for: Where: P ref To modify the previous active power reference value.

[0014] A further improvement of the present invention is that the maximum active output reference value corresponding to the maximum active current output by the VSG is for: Where: λ is the correction coefficient of the reference value of active power; I d is the d-axis component of the output current of the energy storage converter; the energy storage VSG control system achieves the current limiting purpose while stabilizing the active power reference value P output by the power angle ref Expressed as: P ref =min(P ref1 ,P ref2 ); where min means taking the minimum value.

[0015] A grid-type energy storage transient performance improvement system, comprising:

[0016] The current control module is used to divide the maximum current threshold of the energy storage converter in the transient state into the current in the dq coordinate system, combine the component of the A-phase current output by the energy storage converter on the d-axis, and calculate the total impedance required for current limiting with the voltage difference at both ends, set the virtual impedance, and introduce the virtual impedance into the current control link to achieve overcurrent limitation;

[0017] The power control module is used to output voltage in the current control link. The output voltage acts on the VSG power control link to achieve power angle control.

[0018] A further improvement of the present invention is that, in the current control module, the maximum current threshold value I of the energy storage converter in the transient state is set to m Set to: I m =(1+K m )I N Where: K m I is the peak current carrying coefficient of the energy storage converter; N is the rated current of the VSG output.

[0019] The present invention has at least the following beneficial technical effects:

[0020] The present invention mainly focuses on the overcurrent limitation and power angle control strategy of the grid-type energy storage system with the voltage-type virtual synchronous generator (VSG) as the core under the short-circuit fault of the power grid. This method realizes the effective suppression of overcurrent and maintains the stability of the system power angle during the low voltage ride-through process by adaptively adjusting the virtual impedance and correcting the active power command value, thereby improving the transient performance of the grid-type energy storage system. The present invention proposes an innovative overcurrent limitation and power angle control strategy for the complex working conditions when the power grid encounters a short-circuit fault in the grid-type energy storage system with the voltage-type virtual synchronous generator (VSG) as the core. The core of this strategy lies in the ingenious combination of the two major technical means of adaptively adjusting the virtual impedance and correcting the active power command value, thereby achieving efficient and stable operation under extreme grid conditions. In summary, the present invention has the following advantages:

[0021] 1. Adaptive adjustment of virtual impedance:

[0022] When a grid short circuit occurs, the system can quickly sense the degree of voltage drop and dynamically adjust the virtual impedance value of the VSG accordingly. The increase in virtual impedance can effectively increase the system output impedance, thereby reducing the short-circuit current and preventing equipment overload damage. Traditional methods often find it difficult to quickly and effectively limit overcurrent when facing a grid short circuit, which may cause damage to the energy storage system or even cause it to exit operation. Adaptive adjustment of virtual impedance can effectively suppress overcurrent at the early stage of a fault and protect system safety.

[0023] Through this means, the present invention significantly improves the survivability and reliability of the grid-connected energy storage system under grid short-circuit faults, providing important support for grid restoration.

[0024] 2. Correct the active power command value:

[0025] During voltage drops, the system not only adjusts the virtual impedance, but also synchronously corrects the active power command value of the VSG to match the actual needs of the power grid and the safe and stable operation boundaries of the system. This correction is based on real-time power grid status and system performance evaluation, ensuring the rationality and stability of power output. A power grid short circuit may cause an imbalance in the system's active power output, which in turn causes power angle instability and affects the overall stability of the system. By correcting the active power command value, the present invention can effectively avoid power angle fluctuations caused by power imbalance and maintain system power angle stability.

[0026] Maintaining a stable power angle is crucial to ensuring the long-term stable operation of the power grid and energy storage system. This technical means of the present invention significantly improves the power angle control capability of the grid-type energy storage system in a complex power grid environment, and enhances the transient stability and response speed of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The present invention is a flow chart of a method for improving transient performance of grid-type energy storage.

[0028] Figure 2 This is the block diagram of the overcurrent limit control with adaptive virtual impedance.

[0029] Figure 3 is the VSG power angle characteristic curve, where: Figure 3 (a) is the active power command value before correction, Figure 3 (b) When a fault occurs, the active power command value is reduced.

[0030] Figure 4 This is a structural block diagram of a grid-type energy storage transient performance improvement system of the present invention. DETAILED DESCRIPTION

[0031] In the following, only some exemplary embodiments are briefly described. As those skilled in the art will appreciate, the described embodiments may be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the drawings and descriptions are considered to be exemplary and non-restrictive in nature.

[0032] It should be understood that when used in this specification and the appended claims, the terms "include" and "comprises" indicate the presence of described features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or combinations thereof.

[0033] It should also be understood that the terms used in the present specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0034] It should be further understood that the term "and / or" used in the present description and the appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0035] Various structural schematic diagrams of the embodiments disclosed in the present invention are shown in the accompanying drawings. These figures are not drawn to scale, and some details are magnified and some details may be omitted for the purpose of clear expression. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships therebetween are only exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations, and those skilled in the art may additionally design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0036] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0037] Example 1

[0038] like Figure 1 As shown, this embodiment provides a method for improving transient performance of grid-type energy storage, including:

[0039] The maximum current threshold of the energy storage converter in the transient state is divided into the current in the dq coordinate system, and the total impedance required for current limiting is calculated by combining the component of the A-phase current output by the energy storage converter on the d-axis and the voltage difference at both ends, and the virtual impedance is set and introduced into the current control link to achieve overcurrent limitation;

[0040] The current control link outputs voltage, and the output voltage acts on the VSG power control link to achieve power angle control.

[0041] Example 2

[0042] like Figure 2 As shown in the figure, when the grid-type energy storage VSG control system is subjected to a large disturbance similar to a short-circuit fault, which causes the grid voltage to drop, in order to ensure safe and stable operation and not to be destabilized by the short-circuit current impact, a VSG control strategy needs to be formulated to limit the over-limit current and maintain the normal and stable operation of the system. When the system faces a sudden disturbance that causes a sudden drop in voltage, there is a delay in the output voltage and phase adjustment of the VSG. This delayed response characteristic means that the VSG cannot immediately adapt to changes in the state of the grid, which may cause overcurrent. This overcurrent not only puts pressure on the equipment itself, but may also have an adverse effect on the stability of the entire power system, because it will aggravate the transient process of the power grid and increase the difficulty and time of the system to restore a stable state.

[0043] The present invention introduces additional virtual impedance in the VSG control system. This strategy can limit fault current, reduce equipment load pressure, and keep the system voltage level fluctuating within a relatively stable range by increasing the equivalent impedance of the system. By precisely controlling the size of the virtual impedance, the VSG can show a larger equivalent impedance characteristic to the outside world, thereby enhancing the system's ability to resist faults and disturbances without affecting its simulated operating characteristics of traditional synchronous generators, and ensuring that the grid-type energy storage maintains a safe, stable, and efficient operating state in a complex and changeable operating environment.

[0044] In order to limit the fault current and avoid power waste, the present invention proposes a strategy for adjusting the virtual impedance. By finely controlling the virtual impedance, the current can be quickly limited to protect the equipment in the event of a fault, and the system power output can be maximized in the normal state. The present invention sets the maximum current threshold I of the energy storage converter in the transient state m for:

[0045] I m =(1+K m )I N (1)

[0046] Where: K m I is the peak current carrying coefficient of the energy storage converter; N is the rated current of VSG output;.

[0047] The present invention makes the initial position of the A-phase voltage output by the energy storage converter coincide with the d-axis in the dq coordinate system, so that the impedance of the line connected to the energy storage converter is approximately equivalent to the d-axis, calculates the d-axis and q-axis components of the required virtual impedance, and combines the component of the A-phase current output by the energy storage converter on the d-axis with the voltage difference at both ends to calculate the total impedance required for current limiting, and the virtual impedance value Z v By the virtual resistor R v and virtual inductance L v Composition, can be expressed as:

[0048]

[0049] in:

[0050]

[0051] Where: Z d , Z q is the virtual impedance Z v The d and q axis components of E d 、E q are the d-axis and q-axis components of the output voltage of the energy storage converter; R eq +jX eq is the equivalent impedance of the external line connected to the energy storage before the fault, R eq is the equivalent resistance, Xeq is the equivalent reactance; U gd , U gq are the d-axis and q-axis components of the grid voltage after the fault occurs.

[0052] By introducing virtual impedance, the steady-state current during the fault period is controlled to (1+K m )I N At this time, the maximum output current i of the energy storage converter is max It can be expressed as:

[0053]

[0054] To ensure the stable operation of the energy storage control system during the fault period, the maximum output current i of the energy storage converter is max Need to meet:

[0055] i max ≤I m (5)

[0056] In order to enable the energy storage converter to withstand the maximum transient current, according to formula (5), the set virtual impedance must satisfy:

[0057]

[0058] In formula (6), ω is the virtual frequency of the VSG control system.

[0059] like Figure 3 As shown, since the impedance of the external transmission line of the energy storage converter is generally inductive, the impedance of the energy storage converter + external transmission line is set to X, and the active power P and reactive power Q output by the energy storage converter VSG can be expressed as:

[0060]

[0061] In formula (7), E is the VSG output voltage; U is the line voltage connected to the energy storage converter; δ is the VSG system power angle. The difference Δδ between the VSG system power angle and the rated value can be expressed as:

[0062]

[0063] In formula (8): Δω=ω N -ω is the virtual frequency adjustment amount; ω N is the rated virtual frequency; ΔP is the VSG output active power adjustment; D is the virtual damping; J is the virtual inertia.

[0064] When the energy storage system encounters a three-phase grounding fault, there will be a significant difference between the output voltage of the VSG and the grid voltage. At the moment of this voltage drop, although the power angle (i.e. the relative angle between the generator rotor and the grid) remains unchanged temporarily, due to the sudden change in power transmission, especially when the output power drops sharply to a certain level, the power balance of the rotor is broken, causing the rotor to start to rotate faster. As the rotor accelerates, the power angle gradually increases. If the voltage drop is severe and continuous, the continuous increase in the power angle may eventually lead to system power angle instability, affecting the stable operation of the power system.

[0065] Figure 3 The power angle characteristic curve in (a) clearly shows the changing trend of the power angle under the three working conditions before, during and after the fault occurs. According to the equal area rule (that is, in one cycle, the area occupied by the rotor acceleration and deceleration should be equal to maintain stability), if the acceleration area is larger than the deceleration area, it means that the power angle will continue to increase, which may cause instability problems. The present invention proposes an innovative method, that is, by adjusting the reference value of active power to reduce the acceleration area, thereby effectively controlling the stability of the power angle. Specifically, by dynamically adjusting the output level of active power, the acceleration process of the rotor can be slowed down or prevented, thereby preventing the power angle from increasing excessively. In order to maintain a constant voltage difference between the VSG output voltage and the grid voltage before and after the fault, the present invention also utilizes the control strategy of the reactive circuit. By accurately adjusting the reference voltage value of the reactive circuit, the voltage difference can be quickly compensated when the voltage drops, the voltage stability can be maintained, and the output of active power can be indirectly helped to maintain the power angle stability of the entire system. The present invention achieves precise control of VSG output characteristics under three-phase grounding fault by adjusting active power reference value and reactive circuit control at the same time, effectively preventing the occurrence of power angle instability and ensuring the safe and stable operation of the power system. It can be expressed as:

[0066]

[0067] Where: n is the reactive power voltage droop coefficient; E ref is the reference voltage before the fault; is the reactive power reference value.

[0068] In order to maintain the transient power angle stability of VSG, the active power reference value is modified by formula (10): Improve its power angle stability.

[0069]

[0070] Where: P ref To modify the previous active power reference value.

[0071] The present invention takes into account the overload capacity of the PCS when a VSG fault occurs, and the maximum active output reference value corresponding to the maximum active current output by the VSG for:

[0072]

[0073] Where: λ is the correction coefficient of the reference value of active power. d is the d-axis component of the output current of the energy storage converter

[0074] The energy storage VSG control system achieves the current limiting purpose while stabilizing the active power reference value P output by the power angle ref It can be expressed as:

[0075] P ref =min(P ref1 ,P ref2 ) (12)

[0076] Where: min means taking the minimum value. When selecting the active power command value, the smaller value is preferred, which can not only ensure the effective control of the power angle to prevent it from excessively increasing during the fault, but also suppress the current amplitude at the same time. In other words, by selecting a smaller active power command value, we can reduce the impact of the fault current while maintaining the stability of the system power angle, thereby protecting the power system equipment from damage caused by excessive current and improving the reliability and safety of the overall system.

[0077] Example 3

[0078] like Figure 4 As shown, this embodiment provides a grid-type energy storage transient performance improvement system, which includes:

[0079] The current control module is used to divide the maximum current threshold of the energy storage converter in the transient state into the current in the dq coordinate system, combine the component of the A-phase current output by the energy storage converter on the d-axis, and calculate the total impedance required for current limiting with the voltage difference at both ends, set the virtual impedance, and introduce the virtual impedance into the current control link to achieve overcurrent limitation;

[0080] The power control module is used to output voltage in the current control link. The output voltage acts on the VSG power control link to achieve power angle control.

[0081] Example 4

[0082] This embodiment provides a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, it implements the steps of the method for improving the transient performance of a grid-type energy storage.

[0083] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented in one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that include computer-usable program code.

[0084] The present application is described with reference to the flowcharts and / or block diagrams of the methods, systems and computer program products according to the embodiments of the present application. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of the processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A system that specifies the functions of a box or multiple boxes.

[0085] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0086] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0087] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the attached claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention. Any figure mark in the claims should not be regarded as limiting the claims involved.

[0088] In addition, it should be understood that although this specification is described in accordance with the implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation modes that can be understood by those skilled in the art. The above content is only to illustrate the technical idea of ​​the present invention, and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution according to the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for improving transient performance of grid-type energy storage, characterized in that: include: The maximum current threshold of the energy storage converter in the transient state is divided into the current in the dq coordinate system, and the total impedance required for current limiting is calculated by combining the component of the A-phase current output by the energy storage converter on the d-axis and the voltage difference at both ends, and the virtual impedance is set and introduced into the current control link to achieve overcurrent limitation; The current control link outputs voltage, and the output voltage acts on the VSG power control link to achieve power angle control.

2. A method for improving transient performance of grid-type energy storage according to claim 1, characterized in that: The maximum current threshold I of the energy storage converter in transient state m Set to: I m =(1+K m )I N Where: K m I is the peak current carrying coefficient of the energy storage converter; N is the rated current of the VSG output.

3. A method for improving transient performance of grid-type energy storage according to claim 2, characterized in that: The maximum current threshold of the energy storage converter in the transient state is set, and the initial position of the A-phase voltage output by the energy storage converter coincides with the d-axis in the dq coordinate system, so that the impedance of the line connected to the energy storage converter is approximately equivalent to the d-axis. The d-axis and q-axis components of the required virtual impedance are calculated, and the total impedance required for current limiting is calculated by combining the component of the A-phase current output by the energy storage converter on the d-axis and the voltage difference at both ends. The virtual impedance value Z v By the virtual resistor R v and virtual inductance L v Composition, expressed as: in: Where: Z d , Z q is the virtual impedance Z v The d and q axis components of E d 、E q are the d-axis and q-axis components of the output voltage of the energy storage converter; R eq +jX eq is the equivalent impedance of the external line connected to the energy storage before the fault, R eq is the equivalent resistance, X eq is the equivalent reactance; U gd , U gq are the d-axis and q-axis components of the grid voltage after the fault occurs.

4. A method for improving transient performance of grid-type energy storage according to claim 3, characterized in that: According to the set virtual impedance, the steady-state current during the fault period is controlled to (1+K m )I N At this time, the maximum output current i of the energy storage converter is max It is expressed as: To ensure the stable operation of the energy storage control system during the fault period, the maximum output current i of the energy storage converter is max Need to meet: i max ≤I m ; In order to enable the energy storage converter to withstand the maximum transient current, the virtual impedance is set to meet:

5. A method for improving transient performance of grid-type energy storage according to claim 4, characterized in that: Assuming the impedance of the energy storage converter and the external transmission line is X, the active power P and reactive power Q output by the energy storage converter VSG are expressed as: Where: E is the VSG output voltage; U is the line voltage connected to the energy storage converter; δ is the VSG system power angle; the difference Δδ between the VSG system power angle and the rated value is expressed as: Where: Δω=ω N -ω is the virtual frequency adjustment amount; ω N is the rated virtual frequency; ΔP is the VSG output active power adjustment; D is the virtual damping; J is the virtual inertia.

6. A method for improving transient performance of grid-type energy storage according to claim 5, characterized in that: By adjusting the active power reference value and reactive power loop control simultaneously, the VSG output characteristics can be precisely controlled under a three-phase grounding fault. It is expressed as: Where: n is the reactive power voltage droop coefficient; E ref is the reference voltage before the fault; is the reactive power reference value.

7. A method for improving transient performance of grid-type energy storage according to claim 6, characterized in that: To maintain the transient power angle stability of VSG, modify the active power reference value for: Where: P ref To modify the previous active power reference value.

8. A method for improving transient performance of grid-type energy storage according to claim 7, characterized in that: Maximum active output reference value corresponding to the maximum active current output by VSG for: Where: λ is the correction coefficient of the reference value of active power; I d is the d-axis component of the output current of the energy storage converter; the energy storage VSG control system achieves the current limiting purpose while stabilizing the active power reference value P output by the power angle ref Expressed as: P ref =min(P ref1 ,P ref2 ); where min means taking the minimum value.

9. A grid-type energy storage transient performance improvement system, characterized in that: include: The current control module is used to divide the maximum current threshold of the energy storage converter in the transient state into the current in the dq coordinate system, combine the component of the A-phase current output by the energy storage converter on the d-axis, and calculate the total impedance required for current limiting with the voltage difference at both ends, set the virtual impedance, and introduce the virtual impedance into the current control link to achieve overcurrent limitation; The power control module is used to output voltage in the current control link. The output voltage acts on the VSG power control link to achieve power angle control.

10. A grid-type energy storage transient performance improvement system according to claim 9, characterized in that: In the current control module, the maximum current threshold I of the energy storage converter in the transient state is m Set to: I m =(1+K m )I N Where: K m I is the peak current carrying coefficient of the energy storage converter; N is the rated current of the VSG output.

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