Network configuration type control method and device considering voltage support capability and current limiting requirement

Abstract

The application belongs to the technical field of power grid control, and provides a network type control method and device which takes into account voltage support capability and current limiting requirements. The network type control method which takes into account voltage support capability and current limiting requirements comprises: determining equivalent impedance of each control link of a network type converter system according to a topological structure of the network type converter system; wherein the network type converter system is controlled by a virtual synchronous machine; determining fault current of the network type converter system according to the equivalent impedance of each control link; determining virtual impedance of the network type converter system according to a size relationship between the fault current and a preset maximum short-circuit current and a current internal potential of the network type converter system, and inputting the virtual impedance to the virtual synchronous machine. The method provided by the application takes into account voltage support capability and current limiting requirements.

Description

Technical Field

[0001] This application belongs to the field of power grid control technology, and in particular relates to the field of grid-type converters, especially a grid-type control method and device that takes into account both voltage support capability and current limiting requirements. Background Technology

[0002] In existing technologies, the methods for steady-state voltage support in single-unit systems generally employ reactive power control strategies. These strategies include: blocking the reactive power regulator during faults to improve reactive power output capacity; improving reactive power voltage control based on a third-order synchronous machine model to enhance the unit's reactive power voltage support capability; improving the power loop of VSG control and setting the voltage reference value according to the power angle to improve reactive power characteristics during faults; and adopting reactive power priority control to provide voltage support to the system by injecting dynamic reactive current. New power systems based on power electronic converters offer high flexibility and controllability, and voltage support can be achieved by controlling the reactive power output of the converter. However, research on voltage support using virtual synchronous generators (VSGs) focuses primarily on improving control strategies; existing technologies do not consider system short-circuit current limitations, meaning they cannot achieve optimal voltage support during system faults. Summary of the Invention

[0003] The grid-type control method and device provided by this invention, which balances voltage support capability and current limiting requirements, aims to solve the technical problem of poor voltage support capability of grid-type converter systems during faults in the prior art.

[0004] To address the technical problems in the background section of this application, the present invention provides the following technical solutions:

[0005] In a first aspect, the present invention provides a grid-type control method that balances voltage support capability and current limiting requirements, the method comprising:

[0006] The equivalent impedance of each control element of the grid-type converter system is determined based on the topology of the grid-type converter system; wherein the grid-type converter system is controlled by a virtual synchronous machine;

[0007] The fault current of the grid converter system is determined based on the equivalent impedance of each control element.

[0008] The virtual impedance of the grid converter system is determined based on the relationship between the fault current and the preset maximum short-circuit current and the current internal potential of the grid converter system, and the virtual impedance is input to the virtual synchronous machine.

[0009] In some embodiments of this application, the control loop includes: a reactive voltage control loop and a voltage and current dual inner loop control loop;

[0010] Based on the topology of the grid converter system, the equivalent impedance of each control element of the grid converter system is determined, including:

[0011] The equivalent impedance of the reactive voltage control loop is determined based on the power transmission model of the virtual synchronous machine.

[0012] The equivalent impedance of the voltage and current dual inner loop control loop is determined based on the control structure and circuit equations of the voltage and current dual inner loop control loop.

[0013] In some embodiments of this application, determining the fault current of the grid-type converter system based on the equivalent impedance of each control element includes:

[0014] The internal potential of the grid converter system is determined based on the equivalent impedance of each control element.

[0015] The generator terminal voltage during a grid voltage drop is determined based on the internal potential.

[0016] The fault current is determined based on the terminal voltage and the impedance between the terminal bus and the fault point.

[0017] In some embodiments of this application, the virtual impedance of the grid-type converter system is determined based on the relationship between the fault current and the preset maximum short-circuit current and the current internal potential of the grid-type converter system, including:

[0018] When the fault current is not greater than the maximum short-circuit current, the virtual impedance is set to the initial set value;

[0019] Otherwise, the virtual impedance is determined based on the current internal potential and the maximum short-circuit current.

[0020] In some embodiments of this application, determining the virtual impedance based on the current internal potential and the maximum short-circuit current includes:

[0021] The current voltage compensation coefficient of the grid converter system is determined based on the current internal potential.

[0022] The virtual impedance is determined based on the current internal potential and the current voltage compensation coefficient.

[0023] Secondly, the present invention provides a grid-type control device that balances voltage support capability and current limiting requirements, the device comprising:

[0024] An equivalent impedance determination module is used to determine the equivalent impedance of each control element of the grid-type converter system based on the topology of the grid-type converter system; wherein the grid-type converter system is controlled by a virtual synchronous machine;

[0025] The fault current determination module is used to determine the fault current of the grid-type converter system based on the equivalent impedance of each control link.

[0026] The virtual impedance determination module is used to determine the virtual impedance of the grid converter system based on the relationship between the fault current and the preset maximum short-circuit current and the current internal potential of the grid converter system, and input the virtual impedance to the virtual synchronous machine.

[0027] In some embodiments of this application, the control loop includes: a reactive voltage control loop and a voltage and current dual inner loop control loop;

[0028] The equivalent impedance determination module includes:

[0029] The first unit for determining equivalent impedance is used to determine the equivalent impedance of the reactive voltage control link based on the power transmission model of the virtual synchronous machine.

[0030] The second unit for determining equivalent impedance is used to determine the equivalent impedance of the voltage and current dual inner loop control loop based on the control structure and circuit equations of the voltage and current dual inner loop control loop.

[0031] In some embodiments of this application, the fault current determination module includes:

[0032] An internal potential determination unit is used to determine the internal potential of the grid-type converter system based on the equivalent impedance of each control element.

[0033] A terminal voltage determination unit is used to determine the terminal voltage when the grid voltage drops based on the internal potential.

[0034] The fault current determination unit is used to determine the fault current based on the terminal voltage and the impedance between the terminal bus and the fault point.

[0035] In some embodiments of this application, the virtual impedance determination module includes:

[0036] The virtual impedance determination first unit is used to set the virtual impedance to an initial set value when the fault current is not greater than the maximum short-circuit current;

[0037] The virtual impedance is determined by a second unit, which is used otherwise to determine the virtual impedance based on the current internal potential and the maximum short-circuit current.

[0038] In some embodiments of this application, the virtual impedance determination second unit includes:

[0039] The current voltage compensation coefficient determination unit is used to determine the current voltage compensation coefficient of the grid-type converter system based on the current internal potential.

[0040] The virtual impedance determination subunit is used to determine the virtual impedance based on the current internal potential and the current voltage compensation coefficient.

[0041] Thirdly, the present invention provides a computer program product, including a computer program / instruction, which, when executed by a processor, implements the steps of a network-type control method that balances voltage support capability and current limiting requirements.

[0042] Fourthly, the present invention provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement a network-type control method that balances voltage support capability and current limiting requirements.

[0043] Fifthly, the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of a network-type control method that balances voltage support capability and current limiting requirements.

[0044] As described above, embodiments of the present invention provide a grid-type control method and apparatus that balances voltage support capability and current limiting requirements. The corresponding grid-type control method includes: first, determining the equivalent impedance of each control link of the grid-type converter system based on the topology of the grid-type converter system; wherein the grid-type converter system is controlled by a virtual synchronous machine; next, determining the fault current of the grid-type converter system based on the equivalent impedance of each control link; finally, determining the virtual impedance of the grid-type converter system based on the relationship between the fault current and the preset maximum short-circuit current and the current internal potential of the grid-type converter system, and inputting the virtual impedance to the virtual synchronous machine.

[0045] First, the virtual impedance in this invention can change with the voltage compensation coefficient, and can ensure that the short-circuit current is always the maximum allowable short-circuit current during a fault, achieving optimal voltage support while meeting the short-circuit current limit. First, based on the converter voltage source characteristics, the equivalent impedance of each control link in steady state is analyzed, and an equivalent circuit model of the system is established. The output external voltage of each link in the system is characterized based on the equivalent impedance. Second, based on the equivalent circuit analysis, the short-circuit current characteristics of the system are analyzed, the terminal voltage expression is derived, and influencing factors are analyzed. Then, considering both voltage support capability and short-circuit current limit requirements, an adaptive control strategy of virtual impedance and voltage compensation coefficient is proposed. Finally, the effectiveness of the control method is verified through time-domain simulation. Attached Figure Description

[0046] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. 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.

[0047] Figure 1 This is a schematic flowchart of a grid-type control method that balances voltage support capability and current limiting requirements in an embodiment of the present invention.

[0048] Figure 2 This is a flowchart illustrating step 100 of a grid-type control method that balances voltage support capability and current limiting requirements in an embodiment of the present invention.

[0049] Figure 3 This is a flowchart illustrating step 200 of a network-type control method that balances voltage support capability and current limiting requirements in an embodiment of the present invention.

[0050] Figure 4 This is a flowchart illustrating step 300 of a network-type control method that balances voltage support capability and current limiting requirements in an embodiment of the present invention.

[0051] Figure 5 This is a flowchart illustrating step 302 of a network-type control method that balances voltage support capability and current limiting requirements in an embodiment of the present invention.

[0052] Figure 6 This is a flowchart illustrating a network-type control method that balances voltage support capability and current limiting requirements in a specific embodiment of the present invention.

[0053] Figure 7 This is a schematic diagram of the grid-connected converter topology based on VSG control in a specific embodiment of the present invention.

[0054] Figure 8 This is a schematic diagram of the equivalent circuit of the VSG-based control system in a specific embodiment of the present invention.

[0055] Figure 9 This is a schematic diagram of a voltage loop control structure based on control equations and circuit equations in a specific embodiment of the present invention.

[0056] Figure 10 This is a simplified voltage loop control structure diagram in a specific embodiment of the present invention.

[0057] Figure 11 This is a simplified equivalent circuit diagram of the VSG-based control system in a specific embodiment of the present invention.

[0058] Figure 12 This is a three-dimensional curve showing the terminal voltage, virtual impedance, and droop coefficient in a specific embodiment of the present invention.

[0059] Figure 13 This is a curve showing the terminal voltage and voltage compensation coefficient in a specific embodiment of the present invention.

[0060] Figure 14 The diagram below shows the adaptive control structure for virtual impedance and voltage compensation coefficient in a specific embodiment of the present invention.

[0061] Figure 15 This is the terminal voltage waveform of a machine under conventional VSG control in a specific embodiment of the present invention under a three-phase short-circuit fault.

[0062] Figure 16 The specific embodiment of the present invention shows the terminal current waveform under conventional VSG control during a three-phase short-circuit fault.

[0063] Figure 17 This is a specific embodiment of the present invention showing the terminal voltage waveform under a three-phase short-circuit fault, which is controlled adaptively by virtual impedance and voltage compensation coefficient.

[0064] Figure 18 This is a specific embodiment of the present invention showing the terminal current waveform under a three-phase short-circuit fault, which is controlled adaptively by virtual impedance and voltage compensation coefficient.

[0065] Figure 19 This is a virtual impedance waveform obtained by adaptive control of virtual impedance and voltage compensation coefficient under a three-phase short-circuit fault in a specific embodiment of the present invention.

[0066] Figure 20 This is a block diagram of a grid-type control device that balances voltage support capability and current limiting requirements in an embodiment of the present invention.

[0067] Figure 21This is a block diagram of the equivalent impedance determination module 10 in an embodiment of the present invention;

[0068] Figure 22 This is a block diagram of the fault current determination module 20 in an embodiment of the present invention;

[0069] Figure 23 This is a block diagram of the virtual impedance determination module 30 in an embodiment of the present invention;

[0070] Figure 24 A block diagram for determining the virtual impedance of the second unit 30b in an embodiment of the present invention;

[0071] Figure 25 This is a schematic diagram of the structure of an electronic device in an embodiment of the present invention. Detailed Implementation

[0072] 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.

[0073] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention 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.

[0074] It should be noted that the terms "comprising" and "having," and any variations thereof, in the specification, claims, and accompanying drawings of this application are intended to cover a non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not necessarily limited to those explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products, or apparatuses. Without conflict, the embodiments and features in the embodiments of this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0075] Currently, new energy sources are becoming an important part of future energy, possessing enormous development potential. However, with the rapid development of new energy power generation, the integration of large-scale power electronic devices, primarily wind turbines, has altered the power system structure. The current power grid is gradually moving away from the characteristics of a large-scale synchronous grid dominated by traditional rotating equipment with high inertia and strong voltage support, and transitioning towards a new type of power system dominated by power electronic equipment characteristics. Under this new architecture, the reactive power regulation capability of converters based on grid-following (GFL) control is limited, and the integration of grid-following converters will lead to a decrease in system voltage support capability. Therefore, transforming converters from traditional grid-following control to grid-forming (GFM) control is of great significance for improving system voltage support capability.

[0076] The key to improving system voltage support through grid-connected control lies in altering the external characteristics of the converter. Traditional grid-connected control exhibits a controlled current source external characteristic, resulting in poor voltage support capability during faults and a high risk of unit disconnection from the grid, which is detrimental to the safe and stable operation of the system. Grid-connected converters based on VSG control exhibit a controlled voltage source external characteristic, enabling them to actively support system voltage. However, due to the almost constant internal potential during faults, a large short-circuit current will be generated.

[0077] Current limiting strategies for grid-connected converters can be divided into two categories: one is to modify the converter's external characteristics. During a fault, the grid-connected control is switched to grid-following control based on phase-locked loop synchronization, or the current loop is saturated through a current limiter, both of which change the converter's external characteristics from voltage source characteristics to current source characteristics. The other is current limiting based on virtual impedance. This method does not change the converter's external characteristics but achieves current limiting by increasing the system's equivalent impedance. While significant research has been conducted on short-circuit current suppression, short-circuit current and voltage support are interdependent, and control strategies that balance both short-circuit current and voltage support capabilities are rarely studied.

[0078] Based on this, embodiments of the present invention provide a specific implementation of a network-based control method that balances voltage support capability and current limiting requirements. See [link to relevant documentation]. Figure 1 The method includes:

[0079] Step 100: Determine the equivalent impedance of each control element of the grid-type converter system based on the topology of the grid-type converter system; wherein the grid-type converter system is controlled by a virtual synchronous machine;

[0080] Step 200: Determine the fault current of the grid-type converter system based on the equivalent impedance of each control element;

[0081] Step 300: Determine the virtual impedance of the grid-type converter system based on the relationship between the fault current and the preset maximum short-circuit current and the current internal potential of the grid-type converter system, and input the virtual impedance to the virtual synchronous machine.

[0082] As described above, embodiments of the present invention provide a grid-type control method that balances voltage support capability and current limiting requirements, comprising: first, determining the equivalent impedance of each control link of the grid-type converter system based on the topology of the grid-type converter system; wherein the grid-type converter system is controlled by a virtual synchronous machine; next, determining the fault current of the grid-type converter system based on the equivalent impedance of each control link; and finally, determining the virtual impedance of the grid-type converter system based on the relationship between the fault current and the preset maximum short-circuit current and the current internal potential of the grid-type converter system, and inputting the virtual impedance to the virtual synchronous machine.

[0083] This invention provides a grid-type control method that balances voltage support capability and current limiting requirements. It is a grid-type control strategy that balances voltage support capability and current limiting requirements. First, based on the topology of the grid-type converter system controlled by VSG, the equivalent circuit of the system is constructed, and the equivalent impedance of each control element is derived. Then, based on the equivalent impedance, the influencing factors of VSG voltage support and the VSG output current characteristics under short-circuit faults are analyzed. Finally, the VSG control strategy is improved to balance voltage support capability and short-circuit current limiting requirements, proposing an adaptive control strategy based on virtual impedance and voltage compensation coefficient.

[0084] The virtual synchronous generator (VSG) control in step 100 achieves voltage and frequency regulation by simulating the operating characteristics of a synchronous generator. It has the function of actively supporting the system frequency and voltage, and can effectively improve the inertia level of new energy units.

[0085] When implementing step 100, the topology analysis of the network converter system based on VSG control can be used to determine the composition of the system's equivalent impedance and derive the equivalent impedance expressions for each control element.

[0086] For step 200, the voltage support capability and output current characteristics of the VSG are analyzed based on the equivalent impedance. Specifically, the effects of virtual impedance, reactive voltage droop coefficient, and voltage compensation coefficient on the terminal voltage and short-circuit current are analyzed based on the equivalent impedance model.

[0087] Understandably, step 300 improves VSG control by balancing voltage support capability and current limiting requirements. Specifically, it calculates the virtual impedance value that meets the short-circuit current limiting requirements based on the current compensation coefficient, achieving the optimal voltage support state while ensuring that the short-circuit current does not exceed the current limiting requirement.

[0088] In some embodiments of this application, the control loop includes: a reactive voltage control loop and a voltage and current dual inner loop control loop;

[0089] In some embodiments of this application, see Figure 2 Step 100 includes:

[0090] Step 101: Determine the equivalent impedance of the reactive voltage control loop based on the power transmission model of the virtual synchronous machine;

[0091] Specifically, by solving the equivalent impedance of the reactive voltage control loop using the VSG power transfer formula, the equivalent impedance of reactive voltage droop control can be expressed as:

[0092] X q =k q U s (1)

[0093] In the formula, k q U is the reactive voltage droop factor. s This is the terminal voltage.

[0094] Step 102: Determine the equivalent impedance of the voltage and current dual inner loop control loop based on the control structure and circuit equations of the voltage and current dual inner loop control loop.

[0095] Specifically, the equivalent impedance of the voltage and current double inner loop can be solved based on its control structure and circuit equations. Define C. f For the filter capacitor, i sd i sq Let i be the dq-axis component of the converter terminal current. gd i gq Let d be the dq-axis component of the terminal current. According to Kirchhoff's current law, the three-phase currents flowing through the filter capacitor in the dq coordinate system satisfy:

[0096]

[0097] Perform a Laplace transform on equation (2):

[0098]

[0099] When designing a voltage loop control structure using a PI controller, the control equation for the voltage loop can be expressed as:

[0100]

[0101] Because the response speed of the inner current loop is much faster than that of the outer voltage loop, the current loop can be considered equivalent to unity gain when designing the voltage loop. According to the circuit equations and control equations of the voltage loop, the equivalent impedance X under dual voltage and current control is... dWith filter reactance X f They cancel each other out.

[0102] Furthermore, based on the VSG-controlled grid-connected converter topology, the equivalent impedance between the internal potential and the grid can be divided into the following three parts: the equivalent impedance between the internal potential and the grid consists only of the reactive voltage link equivalent impedance X. q Virtual impedance X v and line impedance X g .

[0103] In some embodiments of this application, see Figure 3 Step 200 includes:

[0104] Step 201: Determine the internal potential of the grid-type converter system based on the equivalent impedance of each control element;

[0105] Step 202: Determine the generator terminal voltage when the grid voltage drops based on the internal potential;

[0106] Step 203: Determine the fault current based on the terminal voltage and the impedance between the terminal bus and the fault point.

[0107] In steps 201 to 203, the internal potential of the converter is defined as E. When the grid voltage drops, the terminal voltage can be expressed as follows according to the series voltage divider principle:

[0108]

[0109] In the formula, U ref k is the voltage reference value. q k is the reactive voltage droop factor. v This is the voltage compensation coefficient.

[0110] Define X F Let be the impedance between the terminal bus and the fault point. When a three-phase-to-ground short-circuit fault occurs at the midpoint of the transmission line, neglecting the system's equivalent resistance, the fault current can be expressed as:

[0111]

[0112] Based on the expressions for terminal voltage and fault current, the influence of the system's equivalent impedance on the VSG voltage support capability and fault current is analyzed. Reducing the virtual impedance and droop factor, or adding voltage compensation control, can improve the terminal voltage support capability, but will also increase the system's short-circuit current.

[0113] In some embodiments of this application, see Figure 4 Step 300 includes:

[0114] Step 301: When the fault current is not greater than the maximum short-circuit current, set the virtual impedance to the initial set value;

[0115] Step 302: Otherwise, determine the virtual impedance based on the current internal potential and the maximum short-circuit current.

[0116] In steps 301 and 302, firstly, it is detected whether the fault current exceeds the maximum short-circuit current limit. When the fault current is less than the maximum short-circuit current, the virtual impedance is the initial set value. When the fault current is detected to be greater than the maximum short-circuit current, the virtual impedance is obtained based on the system potential and the maximum short-circuit current at this time, realizing adaptive control of the pseudo-impedance and voltage compensation coefficient. The expression for the virtual impedance is:

[0117]

[0118] In the formula, I fmax To determine the maximum short-circuit current, take I. fmax =3I N At this time, the short-circuit current is limited to three times the rated current during the fault, so that the short-circuit current neither exceeds the limit nor is fully utilized.

[0119] In some embodiments of this application, see Figure 5 Step 302 includes:

[0120] Step 3021: Determine the current voltage compensation coefficient of the grid-type converter system based on the current internal potential;

[0121] Step 3022: Determine the virtual impedance based on the current internal potential and the current voltage compensation coefficient.

[0122] As described above, embodiments of the present invention provide a grid-type control method that balances voltage support capability and current limiting requirements, comprising: first, determining the equivalent impedance of each control link of the grid-type converter system based on the topology of the grid-type converter system; wherein the grid-type converter system is controlled by a virtual synchronous machine; next, determining the fault current of the grid-type converter system based on the equivalent impedance of each control link; and finally, determining the virtual impedance of the grid-type converter system based on the relationship between the fault current and the preset maximum short-circuit current and the current internal potential of the grid-type converter system, and inputting the virtual impedance to the virtual synchronous machine.

[0123] The beneficial effects of this invention are as follows: First, the equivalent impedance of each control link in steady state is derived to obtain the equivalent circuit of the grid-type converter based on VSG control; then, by analyzing the influence of the equivalent impedance on the VSG voltage support capability and fault current, it is proved that the voltage support capability and fault current are coupled with each other, and the key to achieving voltage support lies in making full use of the short-circuit current to generate timely and appropriate reactive power; finally, by improving the VSG control strategy, the virtual impedance matching the current voltage compensation coefficient is calculated according to the short-circuit current requirement, that is, the virtual impedance and voltage compensation coefficient are adaptively controlled to achieve maximum voltage support.

[0124] To further illustrate the solution, this invention also provides a specific implementation of a network-based control method that balances voltage support capability and current limiting requirements. See [link to implementation details]. Figure 6 The method includes the following:

[0125] S1: Determine the equivalent impedance of the grid-type converter system;

[0126] Specifically, firstly, a grid-connected inverter topology based on VSG control is constructed. The converter power outer loop control uses VSG control to generate virtual voltage amplitude and phase.

[26] The virtual voltage, after passing through a virtual impedance, generates the reference voltage for the inner loop control. The virtual impedance is used to simulate the stator resistance and synchronous reactance of the synchronous generator. The converter's inner loop employs a dual-loop voltage and current control, which generates the voltage reference value. The converter in this paper uses an average value model; therefore, the reference voltage does not require PWM modulation and can be directly used as the drive voltage to control the converter. The grid-connected converter topology based on VSG control is shown below. Figure 7 As shown. Figure 7 The variables in the grid-connected converter topology are defined as follows: u d For DC voltage, L f C f These are the filter inductor and capacitor, respectively, Z g U is the equivalent impedance of the line. c U is the converter terminal voltage. s For terminal voltage, i s i is the converter terminal current. g For terminal current, u g This is the grid voltage.

[0127] Next, circuits for a grid-connected inverter system based on VSG control are constructed. Specifically, when constructing the equivalent circuit of the system based on the converter voltage source characteristics, it is assumed that all control elements within the system have reached a steady state. During parameter design, to make the system inductive, the virtual resistance and line resistance are much smaller than the virtual reactance and line reactance, and are neglected in subsequent analysis. According to... Figure 7Based on the VSG-controlled grid-connected converter topology, the equivalent impedance between the internal potential and the grid can be divided into the following five parts: reactive power and voltage link equivalent impedance X q Virtual impedance X v The equivalent impedance X of the voltage and current dual-loop control circuit d Filter reactance X f and line impedance X g The equivalent circuit of the VSG control system is as follows: Figure 8 As shown.

[0128] The equivalent impedance of the reactive voltage control loop is calculated using the VSG power transfer formula. The potential E after reactive voltage droop control is used. f As a reference point, the reactive power output of VSG satisfies equation (8).

[0129]

[0130] Virtual voltage E f With grid connection point voltage U g When the angle between them is very small, we can assume that cosδ = 1, and at this time equation (8) can be simplified to:

[0131]

[0132] according to Figure 7 In the reactive voltage loop control structure, when k v When the voltage is 0, the reactive voltage control loop is reactive voltage droop control, and the virtual voltage amplitude can be expressed as:

[0133] E f =U ref +k q (Q ref -Q s (10)

[0134] Substituting equation (10) into equation (9), we get:

[0135]

[0136] Due to the reactive power reference value Q ref =0, voltage reference value U ref =1, the internal potential of the converter E=1 remains almost unchanged, so equation (11) can be rewritten as:

[0137]

[0138] Equation (12) has a similar form to Equation (9), so the denominator of Equation (12) is the equivalent impedance between the internal potential and the grid connection point. Therefore, the equivalent impedance for reactive voltage droop control can be expressed as:

[0139] X q =k q U s (13)

[0140] When k v When ≠0, compared with reactive voltage droop control, the reference voltage of the reactive voltage control loop is changed from U ref Change to U ref +ΔU v This is equivalent to adding voltage compensation in reactive voltage droop control, and the reactive power after the additional voltage compensation can be obtained:

[0141]

[0142] At this point, the system potential after additional voltage compensation is:

[0143] E=U ref +k v (U ref -U s (15)

[0144] The equivalent impedance of the reactive voltage link still satisfies equation (13), i.e., X q =k q U s .

[0145] For the equivalent impedance of the voltage and current dual inner loop control loop, according to Kirchhoff's current law... Figure 7 The current flowing through the filter capacitor in the dq coordinate system satisfies:

[0146]

[0147] When designing a voltage loop control structure using a PI controller, the control equation for the voltage loop can be expressed as:

[0148]

[0149] Since the response speed of the inner current loop is much faster than that of the outer voltage loop, the current loop can be considered equivalent to unity gain when designing the voltage loop, i.e., ii sdref =i sd i sqref =i sq Based on the voltage loop circuit equation (16) and the voltage loop control equation (17), the decoupling control structure of the voltage loop can be obtained as follows: Figure 9 As shown. The feedforward and dq-axis cross-coupling terms in the voltage loop control structure cancel each other out with the feedforward and dq-axis cross-coupling terms in the circuit equations. The decoupled control structure of the voltage loop after cancellation is as follows: Figure 10 As shown.

[0150] according to Figure 7 In a grid-connected converter topology based on VSG control, the voltage loop reference value is the voltage after passing through a virtual impedance, i.e. Figure 8 U in c The actual value of the filter capacitor voltage is the voltage after passing through the filter impedance, which is equal to the terminal voltage U. s . Figure 10 The actual value of the filter capacitor voltage shown forms a negative feedback with the given value. By properly designing the PI parameters of the voltage loop, the actual value of the filter capacitor voltage can be made to follow the given value, i.e., U. c =U s ,so Figure 8 Medium voltage and current dual-loop controlled equivalent impedance X d With filter reactance X f They cancel each other out.

[0151] In summary, the equivalent impedance between the internal potential and the power grid can be considered as the equivalent impedance X consisting only of the reactive voltage droop element. q Virtual impedance X v and line impedance X g The system consists of three parts, and its equivalent circuit is as follows: Figure 11 As shown.

[0152] S2: Based on equivalent impedance analysis, the voltage support capability and output current characteristics of VSG are analyzed.

[0153] First, we analyze the factors affecting VSG voltage support capability. Based on the system equivalent circuit, when the grid voltage drops, the voltage at the computer terminal can be calculated according to the series voltage divider principle:

[0154]

[0155] Substituting equation (13) into equation (18), we can obtain the generator terminal voltage without additional voltage compensation when the grid voltage drops:

[0156]

[0157] Substituting equation (15) into equation (18), we can obtain the generator terminal voltage after additional voltage compensation when the grid voltage drops:

[0158]

[0159] Based on equation (19), a three-dimensional curve of terminal voltage versus virtual impedance and droop coefficient is plotted as follows: Figure 12 As shown, when the grid voltage amplitude drops, the generator terminal voltage is related to the virtual impedance and the reactive voltage droop coefficient, and decreases as the virtual impedance and the reactive voltage droop coefficient increase. The generator terminal voltage versus voltage compensation coefficient curve is plotted according to equation (20), as shown below. Figure 13As shown, when the grid voltage amplitude drops, the generator terminal voltage is related to the voltage compensation coefficient, and it increases as the voltage compensation coefficient increases.

[0160] Next, the output current characteristics of the VSG under a short-circuit fault are determined. When a three-phase-to-ground short-circuit fault occurs at the midpoint of the transmission line, neglecting the equivalent system resistance, the fault current can be expressed as:

[0161]

[0162] According to equation (21), while reducing the virtual impedance, reducing the droop coefficient, and adding voltage compensation control improve the voltage support capability, the system also faces the risk of overcurrent. Referring to industry standard requirements k... q The variable range is small; when the fault condition is determined, X F Since the equivalent impedance is constant, the change in the equivalent impedance mainly depends on the virtual impedance. The virtual impedance can be adjusted according to the current voltage compensation coefficient to meet the system current limiting requirements.

[0163] S3: Improved VSG control to balance voltage support capability and current limiting requirements.

[0164] Understandably, the key to a grid-type converter system's good voltage support capability lies in its ability to fully utilize short-circuit current and generate timely and appropriate reactive power. To balance voltage support capability and short-circuit current limitations, two conditions must be met when designing the virtual impedance:

[0165] (1) Ensure that the fault current is never greater than the maximum short-circuit current to prevent the current from exceeding the limit;

[0166] (2) Make full use of the short-circuit current during the fault to achieve the best voltage support effect.

[0167] Based on the above conditions, the virtual impedance that meets the requirements can be obtained from the current internal potential and the maximum short-circuit current. The expression for the virtual impedance is shown in equation (21).

[0168]

[0169] When the fault current is less than the maximum short-circuit current, the virtual impedance is the initial set value; when the detected fault current is greater than the maximum short-circuit current, the virtual impedance is obtained based on the system potential and the maximum short-circuit current at this time. Based on equation (22) Figure 7 The VSG control structure shown is improved to obtain an adaptive control of virtual impedance and voltage compensation coefficient, as shown below. Figure 14 As shown.

[0170] Feasibility verification: The simulation example system topology is as follows Figure 7 As shown, the droop coefficient k q =0.04, virtual reactance X v=0.04pu, filter reactance X f =0.33pu, transformer impedance is 0.08pu, line impedance is 0.04pu, with Figure 7 The effectiveness of this invention is verified using a three-phase short-circuit fault occurring at the neutral point of a 35kV line as an example. To highlight the superiority of the method employed in this invention, simulations are performed under fault conditions under two scenarios: conventional VSG control and adaptive control with virtual impedance and voltage compensation coefficient. The changes in terminal voltage and current, as well as the adaptive virtual impedance, are observed.

[0171] Figure 15 , Figure 16 The waveforms of the terminal voltage and current are shown for different virtual impedances and voltage compensation coefficients when using conventional VSG control under a three-phase short-circuit fault. Figure 15 It can be seen that under conventional VSG control, reducing virtual impedance or adding voltage compensation control during fault periods results in an increase in terminal voltage. According to... Figure 16 It can be seen that when the voltage compensation coefficient is 0.5, the virtual impedance X v =0.36pu The current is limited to 3 times the rated current, but when the voltage compensation coefficient decreases, the short-circuit current cannot be fully utilized.

[0172] Figure 17 , Figure 18 , Figure 19 The figures show the terminal voltage, current, and virtual impedance waveforms under three-phase short-circuit faults using adaptive control with virtual impedance and voltage compensation, and different voltage compensation coefficients. Adaptive control with virtual impedance and voltage compensation coefficient allows the virtual impedance to change with the voltage compensation coefficient, ensuring that the short-circuit current remains at the system's maximum allowable short-circuit current during the fault, achieving optimal voltage support while meeting short-circuit current limits.

[0173] contrast Figures 15 to 19 The simulation results demonstrate that the control strategy described in this invention can ensure that the current does not exceed the limit while also taking into account the voltage support capability. This demonstrates the effectiveness and feasibility of the grid-type control strategy described in this invention, which takes into account both voltage support capability and current limiting requirements.

[0174] As described above, embodiments of the present invention provide a grid-type control method that balances voltage support capability and current limiting requirements, comprising: first, determining the equivalent impedance of each control link of the grid-type converter system based on the topology of the grid-type converter system; wherein the grid-type converter system is controlled by a virtual synchronous machine; next, determining the fault current of the grid-type converter system based on the equivalent impedance of each control link; and finally, determining the virtual impedance of the grid-type converter system based on the relationship between the fault current and the preset maximum short-circuit current and the current internal potential of the grid-type converter system, and inputting the virtual impedance to the virtual synchronous machine.

[0175] In summary, the grid-type control strategy described in this invention, which balances voltage support capability and current limiting requirements, fully utilizes the voltage support capability while ensuring that the short-circuit current does not exceed the limit. Before analyzing the voltage source characteristics of the VSG-controlled grid-type converter, the system equivalent impedance is divided into five parts based on the topology of the VSG-controlled grid-type converter. The equivalent impedance of each part is derived, and the system equivalent circuit is constructed. Then, based on the system impedance, the influence of virtual impedance, reactive voltage droop coefficient, and voltage compensation coefficient on the terminal voltage is analyzed. Based on the system equivalent circuit, the influence of voltage support factors on short-circuit current is analyzed. Finally, considering both voltage support capability and short-circuit current limitation requirements, the VSG control strategy is improved, and adaptive control of virtual impedance and voltage compensation coefficient is proposed. This invention utilizes the voltage source characteristics of grid-type control to achieve both voltage support and effective suppression of short-circuit current.

[0176] Based on the same inventive concept, embodiments of this application also provide a network-type control device that balances voltage support capability and current limiting requirements, which can be used to implement the methods described in the above embodiments, as shown in the following embodiments. Since the principle of the network-type control device that balances voltage support capability and current limiting requirements is similar to that of the network-type control method that balances voltage support capability and current limiting requirements, the implementation of the network-type control device that balances voltage support capability and current limiting requirements can refer to the implementation of the network-type control method that balances voltage support capability and current limiting requirements; repeated details will not be elaborated further. As used below, the terms "unit" or "module" can refer to a combination of software and / or hardware that performs a predetermined function. Although the system described in the following embodiments is preferably implemented in software, hardware implementation, or a combination of software and hardware, is also possible and contemplated.

[0177] Embodiments of the present invention provide a specific implementation of a network-type control device that balances voltage support capability and current limiting requirements, enabling a network-type control method that achieves both voltage support capability and current limiting requirements. See [link to specific implementation details]. Figure 20 A grid-type control device that balances voltage support capability and current limiting requirements specifically includes the following:

[0178] The equivalent impedance determination module 10 is used to determine the equivalent impedance of each control link of the grid-type converter system according to the topology of the grid-type converter system; wherein the grid-type converter system is controlled by a virtual synchronous machine;

[0179] The fault current determination module 20 is used to determine the fault current of the grid-type converter system based on the equivalent impedance of each control link.

[0180] The virtual impedance determination module 30 is used to determine the virtual impedance of the grid-type converter system based on the relationship between the fault current and the preset maximum short-circuit current and the current internal potential of the grid-type converter system, and input the virtual impedance to the virtual synchronous machine.

[0181] In some embodiments of this application, the control loop includes: a reactive voltage control loop and a voltage and current dual inner loop control loop;

[0182] See Figure 21 The equivalent impedance determination module 10 includes:

[0183] The first unit 10a for determining equivalent impedance is used to determine the equivalent impedance of the reactive voltage control link based on the power transmission model of the virtual synchronous machine.

[0184] The second unit 10b for determining equivalent impedance is used to determine the equivalent impedance of the voltage and current dual inner loop control loop based on the control structure and circuit equations of the voltage and current dual inner loop control loop.

[0185] In some embodiments of this application, see Figure 22 The fault current determination module 20 includes:

[0186] Internal potential determination unit 20a is used to determine the internal potential of the grid-type converter system based on the equivalent impedance of each control link.

[0187] Terminal voltage determination unit 20b is used to determine the terminal voltage when the grid voltage drops based on the internal potential.

[0188] The fault current determination unit 20c is used to determine the fault current based on the terminal voltage and the impedance between the terminal bus and the fault point.

[0189] In some embodiments of this application, see Figure 23 The virtual impedance determination module 30 includes:

[0190] The virtual impedance determination first unit 30a is used to set the virtual impedance to an initial set value when the fault current is not greater than the maximum short-circuit current;

[0191] The virtual impedance is determined by the second unit 30b, which is used otherwise to determine the virtual impedance based on the current internal potential and the maximum short-circuit current.

[0192] In some embodiments of this application, see Figure 24 The virtual impedance determination of the second unit 30b includes:

[0193] The current voltage compensation coefficient determination unit 30b1 is used to determine the current voltage compensation coefficient of the grid-type converter system based on the current internal potential.

[0194] Virtual impedance determination subunit 30b2 is used to determine the virtual impedance based on the current internal potential and the current voltage compensation coefficient.

[0195] As described above, embodiments of the present invention provide a grid-type control device that balances voltage support capability and current limiting requirements, comprising: an equivalent impedance determination module, used to determine the equivalent impedance of each control link of the grid-type converter system according to the topology of the grid-type converter system; wherein the grid-type converter system is controlled by a virtual synchronous machine; a fault current determination module, used to determine the fault current of the grid-type converter system according to the equivalent impedance of each control link; and a virtual impedance determination module, used to determine the virtual impedance of the grid-type converter system according to the relationship between the fault current and the preset maximum short-circuit current and the current internal potential of the grid-type converter system, and input the virtual impedance to the virtual synchronous machine.

[0196] First, the virtual impedance in this invention can change with the voltage compensation coefficient, and can ensure that the short-circuit current is always the maximum allowable short-circuit current during a fault, achieving optimal voltage support while meeting the short-circuit current limit. First, based on the converter voltage source characteristics, the equivalent impedance of each control link in steady state is analyzed, and an equivalent circuit model of the system is established. The output external voltage of each link in the system is characterized based on the equivalent impedance. Second, based on the equivalent circuit analysis, the short-circuit current characteristics of the system are analyzed, the terminal voltage expression is derived, and influencing factors are analyzed. Then, considering both voltage support capability and short-circuit current limit requirements, an adaptive control strategy of virtual impedance and voltage compensation coefficient is proposed. Finally, the effectiveness of the control method is verified through time-domain simulation.

[0197] The embodiments of this application also provide a specific implementation of an electronic device capable of realizing all steps in the network-type control method that balances voltage support capability and current limiting requirements as described in the above embodiments. See [link to relevant documentation]. Figure 25 The electronic devices specifically include the following:

[0198] Processor 1201, memory 1202, communications interface 1203, and bus 1204;

[0199] The processor 1201, memory 1202, and communication interface 1203 communicate with each other via bus 1204; the communication interface 1203 is used to realize information transmission between server-side devices and client-side devices and other related devices.

[0200] The processor 1201 is used to call the computer program in the memory 1202. When the processor executes the computer program, it implements all the steps in the network-type control method that balances voltage support capability and current limiting requirements in the above embodiments. For example, when the processor executes the computer program, it implements the following steps:

[0201] Step 100: Determine the equivalent impedance of each control element of the grid-type converter system based on the topology of the grid-type converter system; wherein the grid-type converter system is controlled by a virtual synchronous machine;

[0202] Step 200: Determine the fault current of the grid-type converter system based on the equivalent impedance of each control element;

[0203] Step 300: Determine the virtual impedance of the grid-type converter system based on the relationship between the fault current and the preset maximum short-circuit current and the current internal potential of the grid-type converter system, and input the virtual impedance to the virtual synchronous machine.

[0204] Embodiments of this application also provide a computer-readable storage medium capable of implementing all steps of the network-type control method that balances voltage support capability and current limiting requirements in the above embodiments. The computer-readable storage medium stores a computer program that, when executed by a processor, implements all steps of the network-type control method that balances voltage support capability and current limiting requirements in the above embodiments. For example, when the processor executes the computer program, it implements the following steps:

[0205] Step 100: Determine the equivalent impedance of each control element of the grid-type converter system based on the topology of the grid-type converter system; wherein the grid-type converter system is controlled by a virtual synchronous machine;

[0206] Step 200: Determine the fault current of the grid-type converter system based on the equivalent impedance of each control element;

[0207] Step 300: Determine the virtual impedance of the grid-type converter system based on the relationship between the fault current and the preset maximum short-circuit current and the current internal potential of the grid-type converter system, and input the virtual impedance to the virtual synchronous machine.

[0208] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to interchangeably. Each embodiment focuses on its differences from other embodiments. In particular, hardware + program embodiments are relatively simple in description because they are fundamentally similar to method embodiments; relevant parts can be referred to the descriptions in the method embodiments.

[0209] The foregoing has described specific embodiments of this specification. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recited in the claims may be performed in a different order than that shown in the embodiments and may still achieve the desired result. Furthermore, the processes depicted in the drawings do not necessarily require the specific or sequential order shown to achieve the desired result. In some embodiments, multitasking and parallel processing are possible or may be advantageous.

[0210] While this application provides method operation steps as shown in the embodiments or flowcharts, more or fewer operation steps may be included based on conventional or non-inventive labor. The order of steps listed in the embodiments is merely one possible execution order among many and does not represent the only execution order. In actual device or client product execution, the method can be executed sequentially as shown in the embodiments or drawings, or in parallel (e.g., in a parallel processor or multi-threaded processing environment).

[0211] For ease of description, the above devices are described in terms of function, divided into various modules. Of course, in implementing the embodiments of this specification, the functions of each module can be implemented in one or more software and / or hardware components, or a module that performs the same function can be implemented by a combination of multiple sub-modules or sub-units. The device embodiments described above are merely illustrative. For example, the division of units is only a logical functional division; in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces, or indirect coupling or communication connection between devices or units, and may be electrical, mechanical, or other forms.

[0212] Those skilled in the art will also know that, besides implementing the controller using purely computer-readable program code, the same functions can be achieved by logically programming the method steps, making the controller function as logic gates, switches, application-specific integrated circuits (ASICs), programmable logic controllers (PLCs), and embedded microcontrollers. Therefore, such a controller can be considered a hardware component, and the devices within it used to implement various functions can also be considered structures within that hardware component. Alternatively, the devices used to implement various functions can be considered as both software modules implementing the method and structures within a hardware component.

[0213] In a typical configuration, a computing device includes one or more processors (CPU), input / output interfaces, network interfaces, and memory.

[0214] Memory may include non-persistent storage in computer-readable media, such as random access memory (RAM) and / or non-volatile memory, such as read-only memory (ROM) or flash RAM. Memory is an example of computer-readable media.

[0215] The embodiments described in this specification can be described in the general context of computer-executable instructions, such as program modules, that are executed by a computer. Generally, program modules include routines, programs, objects, components, data structures, etc., that perform a specific task or implement a specific abstract data type. The embodiments of this specification can also be practiced in distributed computing environments where tasks are performed by remote processing devices connected via a communication network. In distributed computing environments, program modules can reside in local and remote computer storage media, including storage devices.

[0216] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, system embodiments are basically similar to method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments. In the description of this specification, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the embodiments in this specification. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described can be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0217] The above description is merely an embodiment of the embodiments in this specification and is not intended to limit the embodiments of this specification. For those skilled in the art, various modifications and variations can be made to the embodiments of this specification. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of the embodiments of this specification should be included within the scope of the claims of the embodiments of this specification.

Claims

1. A grid-based control method that balances voltage support capability and current limiting requirements, characterized in that, include: The equivalent impedance of each control element of the grid-type converter system is determined based on the topology of the grid-type converter system; wherein the grid-type converter system is controlled by a virtual synchronous machine; The fault current of the grid converter system is determined based on the equivalent impedance of each control element. The virtual impedance of the grid converter system is determined based on the relationship between the fault current and the preset maximum short-circuit current and the current internal potential of the grid converter system, and the virtual impedance is input to the virtual synchronous machine. The virtual impedance of the grid converter system is determined based on the relationship between the fault current and the preset maximum short-circuit current, and the current internal potential of the grid converter system, including: When the fault current is not greater than the maximum short-circuit current, the virtual impedance is set to the initial set value; Otherwise, the virtual impedance is determined based on the current internal potential and the maximum short-circuit current.

2. The network-type control method according to claim 1, characterized in that, The control mechanism includes: a reactive voltage control mechanism and a voltage and current dual inner loop control mechanism. Based on the topology of the grid converter system, the equivalent impedance of each control element of the grid converter system is determined, including: The equivalent impedance of the reactive voltage control loop is determined based on the power transmission model of the virtual synchronous machine. The equivalent impedance of the voltage and current dual inner loop control loop is determined based on the control structure and circuit equations of the voltage and current dual inner loop control loop.

3. The network-type control method according to claim 1, characterized in that, Determining the fault current of the grid-type converter system based on the equivalent impedance of each control element includes: The internal potential of the grid converter system is determined based on the equivalent impedance of each control element. The generator terminal voltage during a grid voltage drop is determined based on the internal potential. The fault current is determined based on the terminal voltage and the impedance between the terminal bus and the fault point.

4. The network-type control method according to claim 1, characterized in that, Determining the virtual impedance based on the current internal potential and the maximum short-circuit current includes: The current voltage compensation coefficient of the grid converter system is determined based on the current internal potential. The virtual impedance is determined based on the current internal potential and the current voltage compensation coefficient.

5. A grid-type control device that balances voltage support capability and current limiting requirements, characterized in that, include: An equivalent impedance determination module is used to determine the equivalent impedance of each control element of the grid-type converter system based on the topology of the grid-type converter system; wherein the grid-type converter system is controlled by a virtual synchronous machine; The fault current determination module is used to determine the fault current of the grid-type converter system based on the equivalent impedance of each control link. The virtual impedance determination module is used to determine the virtual impedance of the grid converter system based on the relationship between the fault current and the preset maximum short-circuit current and the current internal potential of the grid converter system, and input the virtual impedance to the virtual synchronous machine. The virtual impedance determination module includes: The virtual impedance determination first unit is used to set the virtual impedance to an initial set value when the fault current is not greater than the maximum short-circuit current; The virtual impedance is determined by a second unit, which is used otherwise to determine the virtual impedance based on the current internal potential and the maximum short-circuit current.

6. The network-type control device according to claim 5, characterized in that, The control mechanism includes: a reactive voltage control mechanism and a voltage and current dual inner loop control mechanism. The equivalent impedance determination module includes: The first unit for determining equivalent impedance is used to determine the equivalent impedance of the reactive voltage control link based on the power transmission model of the virtual synchronous machine. The second unit for determining equivalent impedance is used to determine the equivalent impedance of the voltage and current dual inner loop control loop based on the control structure and circuit equations of the voltage and current dual inner loop control loop.

7. The network-type control device according to claim 5, characterized in that, The fault current determination module includes: An internal potential determination unit is used to determine the internal potential of the grid-type converter system based on the equivalent impedance of each control element. A terminal voltage determination unit is used to determine the terminal voltage when the grid voltage drops based on the internal potential. The fault current determination unit is used to determine the fault current based on the terminal voltage and the impedance between the terminal bus and the fault point.

8. The network-type control device according to claim 5, characterized in that, The virtual impedance determination second unit includes: The current voltage compensation coefficient determination unit is used to determine the current voltage compensation coefficient of the grid-type converter system based on the current internal potential. The virtual impedance determination subunit is used to determine the virtual impedance based on the current internal potential and the current voltage compensation coefficient.

9. A computer program product comprising a computer program / instructions, characterized in that, When the computer program / instruction is executed by the processor, it implements the steps of the network control method that balances voltage support capability and current limiting requirements as described in any one of claims 1 to 4.

10. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the steps of the network control method that balances voltage support capability and current limiting requirements as described in any one of claims 1 to 4.

11. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of the network control method that balances voltage support capability and current limiting requirements as described in any one of claims 1 to 4.

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