A method for quantitatively analyzing overcurrent capability requirement of a network-constructed converter and related device

Abstract

A kind of network construction type converter overcurrent capacity requirement quantitative analysis method and related device, the method includes: based on equal-area rule, the quantitative relationship of minimum overcurrent capacity required to make converter meet transient stability target and critical clearance time is established;Based on the voltage-current phasor diagram when converter reaches maximum voltage support, the quantitative relationship of minimum overcurrent capacity required to make converter meet point of common coupling voltage support target and point of common coupling voltage is established;According to the grid operating condition outside converter and its key parameters, based on the aforementioned quantitative relationship, the minimum overcurrent capacity meeting transient stability and point of common coupling voltage support capacity key index is calculated respectively, and the maximum value thereof is obtained to obtain overcurrent capacity requirement under given parameters considering transient stability and voltage support capacity.This application can calculate the minimum overcurrent capacity required for network construction type converter to have transient stability and voltage support capacity, and optimize the cost of network construction type converter.

Description

Technical Field

[0001] This invention relates to the field of grid-type converters, specifically a quantitative analysis method and related apparatus for the current carrying capacity requirements of grid-type converters. Background Technology

[0002] my country's new energy industry is developing rapidly, and the penetration rate of distributed generators in the power grid is constantly increasing. The power system is showing a "dual high" development trend of high proportion of renewable energy and high proportion of power electronic equipment. However, at present, most new energy sources are connected to the grid through grid-following (GFL) converters. The output characteristics of grid-following converters are controlled current sources, and they rely on phase-locked loops to achieve synchronization with the grid. They have problems such as not being able to form an independent grid, poor stability under weak grid conditions, and inability to provide sufficient voltage support and inertial support.

[0003] To address these issues, grid-forming (GFM) converters have been proposed, gaining increasing attention due to their ability to provide sufficient voltage and frequency support and their strong stability in weak power grids. However, the support capability of grid-forming converters is limited by their overcurrent capacity, and increasing the overcurrent capacity may increase hardware costs. Therefore, a method is needed to determine an appropriate overcurrent capacity for grid-forming converters based on actual conditions.

[0004] Currently, due to the low overcurrent capacity of power electronic equipment, grid-type converters usually incorporate current limiting methods to prevent excessive current from damaging the equipment during operation. Common current limiting methods are mainly divided into two types: one is to achieve current limiting by using the current reference value of the current limiting current loop, as shown in references [1,2], and the other is to achieve current limiting by introducing virtual impedance, as shown in reference [3]. The former can be further divided into three methods: d-axis priority, q-axis priority, and power factor angle priority. Reference [4] analyzes the influence of the current limiting loop on the transient stability of the converter under the d-axis priority current limiting strategy, and points out the instability mechanism of the converter under large disturbances by analyzing the power angle curve of the converter. Similarly, reference [5] analyzes the transient process of the grid-type converter using the q-axis priority current limiting method under large disturbances. The above two articles only studied the influence of d-axis priority and q-axis priority current limiting, respectively. Reference [6] explored the power angle curves of grid-type converters under different current limiting strategies. By analyzing the phasor diagrams of grid-type converters under the d-axis priority, q-axis priority, and power factor angle priority conditions, the power angle curves under the corresponding conditions were obtained. Although the above references have studied the transient stability of grid-type converters, none of them have clearly pointed out the quantitative relationship between transient stability and overcurrent capacity.

[0005] On the other hand, the overcurrent capacity of the grid converter affects its active support capability, especially its voltage support capability. Reference [7] analyzed the influence of current limiting on the voltage support capability of the grid converter by studying the phasor diagram of the grid converter under different voltage drop levels, and proposed to add a power reference value limiting link and a variable coefficient reactive voltage droop control method to improve the voltage support capability of the converter under current limiting conditions. Reference [8] proposed to cut off the reactive voltage droop control link when the voltage drops, and introduce virtual impedance to limit the current, thereby realizing the voltage support under current limiting conditions. The above references all analyzed the influence of current limiting on the voltage support capability of the grid converter, but did not conduct in-depth research on the quantitative relationship between the overcurrent capacity and voltage support capability of the converter.

[0006] In summary, many studies have analyzed the impact of converter overcurrent capacity on its transient stability and voltage support capability, but none have established a method to determine the appropriate overcurrent capacity for grid-type converters based on this impact.

[0007] Related literature:

[0008] [1]

[0009] [2] Li Yanbin, Jia Ke, Bi Tianshu, et al. Analysis of the influence mechanism of inverter power supply on distance protection [J]. Power System Protection and Control, 2018, 46(16):54-59.

[0010] [3] F.Welck, D.Duckwitz and C.Gloeckler, "Influence of Virtual Impedanceon Short Circuit Performance of Virtual Synchronous Machines in the 9-BusSystem," NEIS2017; Conference on Sustainable Energy Supply and Energy Storage Systems, Hamburg, Germany, 2017, pp.1-7.

[0011] [4] Huang Linbin, Zhang Leiqi, Xin Huanhai, et al. Analysis of virtual power angle stability mechanism of droop control inverter [J]. Automation of Electric Power Systems, 2016, 40(12):117-123+150.

[0012] [5]Z.Bian and Z.Xu, "Fault Ride-Through Capability EnhancementStrategy for VSC-HVDC Systems Supplying for Passive IndustrialInstallations," in IEEE Transactions on Power Delivery, vol.31, no.4, pp.1673-1682, Aug.2016

[0013] [6]KGSaffar, S.Driss and FBAjaei, "Impacts of Current Limiting onth e Transient Stability of the Virtual Synchronous Generator," in IEEETransactions on Power Electronics, vol.38, no.2, pp.1509-1521, Feb.2023.

[0014] [7] Zhang Yu, Zhang Chen, Cai Xu, et al. Research on current-constrained transient voltage support mechanism and improved fault ride-through control of virtual synchronous machine [J / OL]. Proceedings of the CSEE, 1-14.

[0015] [8] Xing Pengxiang, Jia Xuanyue, Xu Changqing, et al. Characteristic analysis and control method of VSG low voltage ride-through [J]. Power Grid and Clean Energy, 2022, 38(08):130-7+43. Summary of the Invention

[0016] To address the lack of quantitative analysis methods for the current capacity requirements of grid-type converters, this invention proposes a quantitative analysis method and related apparatus for the current capacity requirements of grid-type converters.

[0017] A quantitative analysis method for the overcurrent capacity requirement of a grid-type converter includes the following steps:

[0018] Based on the equal area rule, a first quantitative relationship is established between the minimum overcurrent capacity required for the converter to meet the transient stability target and the critical clearing time.

[0019] Based on the voltage-current phasor diagram when the converter exerts its maximum voltage support capability, a second quantitative relationship is established between the minimum overcurrent capability required for the converter to meet the common coupling point voltage support target and the common coupling point voltage.

[0020] Based on the external power grid conditions and its own key parameters, the minimum overcurrent capacity required to meet the transient stability target and the common coupling point voltage support target are calculated based on the first quantification relationship and the second quantification relationship, respectively. The maximum value of the two minimum overcurrent capacities is taken to obtain the overcurrent capacity requirement that takes into account both transient stability and voltage support capacity under given parameters.

[0021] Furthermore, the converter has a minimum overcurrent capacity I required to meet the transient stability target. sta With critical clearance time t cc The quantization relationship is affected by the following parameters: active power setpoint P0, primary frequency regulation power P △ Short-circuit ratio (SCR), moment of inertia (J), rated angular frequency (ω0), converter terminal electromotive force (E), and grid terminal voltage (V) g ;

[0022] The first quantization relationship is shown below:

[0023]

[0024] Where P in The virtual axis power satisfies the relation P in =P0-P △ .

[0025] Furthermore, the converter meets the minimum overcurrent capability I required to support the voltage at the point of common coupling. sup voltage V at common coupling point pccThe quantification relationship is affected by the following parameters: grid short-circuit ratio (SCR), grid-side voltage (V). g The relative distance d between the short-circuit point and the common coupling point, and the ground short-circuit impedance Z. s ;

[0026] The second quantization relationship is shown below:

[0027]

[0028] Furthermore, the solution process for the overcurrent capacity requirement that balances transient stability and voltage support capability is as follows:

[0029] Based on the external power grid operating conditions and converter parameters, the relevant parameters required for the solution are set. These external power grid operating condition parameters include: the short-circuit ratio (SCR) and the grid-side voltage (V). g Rated angular frequency ω0, relative distance d from the short-circuit point to the common coupling point, and ground short-circuit impedance Z s The converter parameters include: active power setpoint P0, primary frequency regulation power P △ , moment of inertia J, converter terminal electromotive force E; performance requirements include: critical clearing time t cc Common coupling point voltage V pcc ;

[0030] Based on the relevant parameters required in the solution, the minimum overcurrent capacity I required for the converter to meet the transient stability target is obtained according to equations (1) and (2). sta The minimum overcurrent capacity I required for the converter to meet the target of common point of coupling voltage support. sup ;

[0031] Based on this, the minimum overcurrent capacity I is selected. sta and minimum overcurrent capability I sup The maximum value yields the overcurrent capacity requirement that balances transient stability and voltage support under given parameters. Therefore, the overcurrent capacity I of the grid-type converter is... max The following relation should be satisfied:

[0032] I max ≥max[I sta ,I sup (3).

[0033] A device for quantitatively analyzing the overcurrent capacity requirement of a grid-type converter includes:

[0034] The first quantification relationship construction module is used to establish the first quantification relationship between the minimum overcurrent capacity and the critical clearing time required for the converter to meet the transient stability target based on the equal area rule.

[0035] The second quantization relationship construction module is used to establish a second quantization relationship between the minimum overcurrent capacity required for the converter to meet the common coupling point voltage support target and the common coupling point voltage, based on the voltage and current phasor diagram when the converter exerts its maximum voltage support capacity.

[0036] The overcurrent capacity requirement acquisition module is used to calculate the minimum overcurrent capacity required to meet the transient stability target and the common coupling point voltage support target based on the power grid conditions outside the converter and its own key parameters, respectively, according to the first quantification relationship and the second quantification relationship. The maximum value of the two minimum overcurrent capacities is taken to obtain the overcurrent capacity requirement that takes into account both transient stability and voltage support under given parameters.

[0037] Furthermore, the converter has a minimum overcurrent capacity I required to meet the transient stability target. sta With critical clearance time t cc The quantization relationship is affected by the following parameters: active power setpoint P0, primary frequency regulation power P △ Short-circuit ratio (SCR), moment of inertia (J), rated angular frequency (ω0), converter terminal electromotive force (E), and grid terminal voltage (V) g ;

[0038] The first quantization relationship is shown below:

[0039]

[0040] Where P in The virtual axis power satisfies the relation P in =P0-P △ .

[0041] Furthermore, the converter meets the minimum overcurrent capability I required to support the voltage at the point of common coupling. sup voltage V at common coupling point pcc The quantification relationship is affected by the following parameters: grid short-circuit ratio (SCR), grid-side voltage (V). g The relative distance d between the short-circuit point and the common coupling point, and the ground short-circuit impedance Z. s ;

[0042] The second quantization relationship is shown below:

[0043]

[0044] Furthermore, the overcurrent capacity requirement acquisition module is specifically used for:

[0045] Based on the external power grid operating conditions and converter parameters, the relevant parameters required for the solution are set. These external power grid operating condition parameters include: the short-circuit ratio (SCR) and the grid-side voltage (V). gRated angular frequency ω0, relative distance d from the short-circuit point to the common coupling point, and ground short-circuit impedance Z s The converter parameters include: active power setpoint P0, primary frequency regulation power P △ , moment of inertia J, converter terminal electromotive force E; performance requirements include: critical clearing time t cc Common coupling point voltage V pcc ;

[0046] Based on the relevant parameters required in the solution, the minimum overcurrent capacity I required for the converter to meet the transient stability target is obtained according to equations (1) and (2). sta The minimum overcurrent capacity I required for the converter to meet the target of common point of coupling voltage support. sup ;

[0047] Based on this, the minimum overcurrent capacity I is selected. sta and minimum overcurrent capability I sup The maximum value yields the overcurrent capacity requirement that balances transient stability and voltage support under given parameters. Therefore, the overcurrent capacity I of the grid-type converter is... max The following relation should be satisfied:

[0048]

[0049] A quantitative analysis system for the overcurrent capacity requirement of a grid-type converter includes: a computer-readable storage medium and a processor;

[0050] The computer-readable storage medium is used to store executable instructions;

[0051] The processor is used to read executable instructions stored in the computer-readable storage medium and execute the quantitative analysis method for the overcurrent capacity requirement of the grid-type converter.

[0052] A non-transitory computer-readable storage medium storing a computer program that, when executed by a processor, implements a quantitative analysis method for the overcurrent capacity requirements of a grid-type converter.

[0053] This invention focuses on transient stability and voltage support capability. Based on the equal-area rule and phasor diagram analysis, it establishes quantitative relationships between the converter's current limiting value and physical quantities such as short-circuit ratio, critical clearing time, and grid voltage. These conditions allow for the calculation of the minimum overcurrent capacity required for the grid-type converter to achieve the necessary transient stability and voltage support capability, thus optimizing the cost of the grid-type converter. Attached Figure Description

[0054] Figure 1 A flowchart illustrating the quantitative analysis method for the overcurrent capacity requirement of a grid-type converter according to an embodiment of the present invention;

[0055] Figure 2 A block diagram of a grid-type converter control strategy based on VSG control;

[0056] Figure 3 A block diagram of voltage and current loop control for adding current limiting to a grid-type converter;

[0057] Figure 4 A phasor diagram of the current reference value when the converter adopts angle priority;

[0058] Figure 5 The power angle curves of the converter before and after current limiting are shown.

[0059] Figure 6 The simplified grid connection model;

[0060] Figure 7 Phasor diagram for when the converter achieves maximum voltage support capability;

[0061] Figure 8 (a) is a simplified grid connection model when a three-phase short-circuit fault occurs in the power grid, and (b) is the Thevenin equivalent model. Detailed Implementation

[0062] 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.

[0063] like Figure 1 As shown, the first aspect of this invention establishes a quantitative relationship related to overcurrent capacity from two aspects: transient stability and voltage support capability, and proposes a quantitative analysis method for the overcurrent capacity requirement of grid-type converters:

[0064] Regarding transient stability, a quantitative relationship between the minimum overcurrent capacity and critical clearing time required for the converter to meet the transient stability target is established based on the equal area rule. Regarding voltage support capability, a quantitative relationship between the minimum overcurrent capacity and the common coupling point voltage is established based on the voltage-current phasor diagram when the converter operates at its maximum voltage support capability. Finally, based on the external grid conditions and the converter's own key parameters, the minimum overcurrent capacity required to meet the key indicators of transient stability and common coupling point voltage support capability is calculated using the aforementioned quantitative relationship. The maximum value is then taken to obtain the overcurrent capacity requirement that balances transient stability and voltage support capability under given parameters.

[0065] First, the basic control model, principle, and strategy of this invention embodiment will be explained:

[0066] This invention takes a grid-type converter control strategy based on virtual synchronous generator (VSG) control as an example. Figure 2 As shown. The control section mainly includes reactive power-voltage control and active power-frequency control. The reactive power-voltage control section deserves special mention. This control strategy employs a voltage-current dual-loop control. A limiting element is added to the dual loop to restrict the current reference value, achieving the limiting purpose, as shown below. Figure 3 As shown. This current limiting method includes many types, such as d-axis priority current limiting, q-axis priority current limiting, and power factor angle priority current limiting. Among them, power factor angle priority current limiting is more common and widely used; therefore, this invention is based on this current limiting method. The current phasor diagram of this method is shown below. Figure 4 As shown. Reference [6] studies the power angle characteristics and power angle curves of grid-type converters using different current limiting methods. The reference points out that the current reference value expression after using the power factor angle priority current limiting method is as follows:

[0067]

[0068] Accordingly, as can be seen from reference [6], the power angle characteristic of the converter at this time is determined by the following formula:

[0069]

[0070] Where i dref i qref i represents the d-axis reference current and q-axis reference current before limiting. d * i q * I represents the d-axis reference current and q-axis reference current after limiting. max V is the limiting value, E is the electromotive force at the VSG terminal, and V is the limiting value. g X is the grid terminal voltage, X is the line impedance, and δ is the power angle of the VSG.

[0071] Based on the above control model and principles, a quantitative analysis of the grid-type converter is conducted:

[0072] 1. Quantitative Analysis of the Influence of Overcurrent Capacity on the Transient Stability of Grid-Type Converters During Low Voltage Ride

[0073] Based on the power angle characteristics after current limiting, the power angle curve of the converter can be plotted, such as... Figure 5 As shown. Figure 5The paper also demonstrates the operating point of the converter under stable operation conditions when a voltage dip occurs. The current limiting circuit affects the power angle curve of the grid-type converter, thus impacting its transient stability. In conjunction with... Figure 5 Before analyzing its impact, it is important to note that, considering practical applications, the obtained I needs to be... max With a certain margin, the worst-case scenario should be considered. Therefore, the following assumptions are made: the low-voltage ride-through strategy fails due to the failure of the relevant detection of voltage drop, in which case the transient stability of the grid converter depends only on the current limiting strategy; in addition, the damping element, which also helps to improve transient stability, is ignored, while the most extreme case of voltage drop to 0 is considered.

[0074] Figure 5 In the diagram, point a is the steady-state operating point. When the most severe voltage drop occurs, i.e., the grid voltage drops to 0, the active power output also drops to 0, so the operating point moves to point b. At this time, the active power command is greater than the actual active power output, and the converter angular frequency is greater than the rated angular frequency, causing the converter's power angle to continuously increase until the fault at point c is cleared. After the fault is cleared, the active power output is no longer 0. Because the power angle is large at this time, the current is limited, so it enters the current-limiting mode, and the operating point moves to the power angle curve when the current is limited. At the moment of clearing, the operating point moves from point c to point d. After the fault is cleared, the converter's active power command is less than the actual active power output, but the converter's angular frequency is still greater than the rated angular frequency. Due to the existence of the virtual inertial element, the angular frequency will not decrease immediately, and the power angle will continue to increase until the angular frequency equals the rated value, i.e., point e. After reaching point e, the converter's angular frequency is still less than the rated angular frequency, and the converter's power angle begins to decrease, eventually returning to the steady-state operating point.

[0075] Regarding the aforementioned transient process, it should be noted that the equal-area rule, commonly used in the transient stability analysis of synchronous machines, also applies to grid-type converters. When the acceleration area during the transient process is exactly equal to the maximum deceleration area, i.e., when point e moves to point e', the converter just reaches stability. If the fault clearing angle δ c If the area is further increased, the acceleration area will exceed the deceleration area, causing the converter to become unstable. Based on this, the relationships between the current limiting value and physical quantities such as the short-circuit ratio, critical clearing time, and virtual shaft power can be established, as shown in the following system of equations:

[0076]

[0077] Where δ cc The critical clearing angle is δ0, and the initial work angle is δ m To maintain stability, the maximum power angle that the operating point can reach is P. in For virtual axis power, V g I is the grid terminal voltage. staConsidering transient stability, the current limiting amplitude of the grid-type converter is given, where J is the moment of inertia, ω0 is the rated angular frequency, and t... cc Where X is the critical clearing time, X is the grid impedance ignoring resistance, and SCR is the grid short-circuit ratio.

[0078] Furthermore, the following expression can be obtained:

[0079]

[0080] Based on this formula, the power P of the virtual axis can be obtained. in , SCR (Short-Circuit Ratio) of Power Grid, Critical Clearance Time t cc Given the converter control parameters such as moment of inertia J, rated angular frequency ω0, and VSG terminal electromotive force E, the current limiting value required for the converter to maintain transient stability also corresponds to its minimum overcurrent capacity.

[0081] 2. Quantitative Analysis of the Influence of Overcurrent Capacity on the Voltage Support Capacity of Grid-Type Converters During Low Voltage Ride

[0082] Figure 6 The diagram shows a simplified grid-connected model. When the grid voltage drop is severe, to fully utilize the converter's voltage support capability, the method of disconnecting the droop circuit and directly applying active power and virtual internal potential commands can achieve maximum voltage support for the converter under current-limiting conditions. The circuit phasor diagram at this time is as follows. Figure 7 As shown. Based on this, we can obtain the expression:

[0083]

[0084] Among them, V pcc As the supporting target for the point of common coupling (PCC) voltage, V g I is the grid terminal voltage. sup To consider the voltage support capability, the current limiting amplitude of the grid-type converter, Z g Let V be the grid-side impedance. This expression assumes an ideal grid voltage drop, i.e., Vgrid. g If the condition is that a three-phase ground fault occurs at the same location on the line, then... Figure 8 In the case shown in (a), the expression will change. The following system of equations can be obtained through the Thevenin equivalent circuit, as shown in Figure (a). Figure 8 As shown in (b).

[0085]

[0086] Where V g 'Z' represents the Thevenin equivalent grid voltage.g ' is the Thevenin equivalent grid impedance, d is the relative distance from the short-circuit point to the point of common coupling, Z is... s This represents the grounding short-circuit impedance. By simultaneously solving the equations within this system, we can obtain the expression for the current limiting amplitude of the grid-type converter at this point:

[0087]

[0088] In the formula, I sup To consider the current limiting amplitude of the grid-type converter when voltage support capability is taken into account, V pcc To support the target voltage at the common coupling point, V g This is the grid-side voltage.

[0089] Based on this formula, knowing the short-circuit ratio, it is possible to determine how the grid-type converter, when a three-phase ground fault occurs at a certain location in the line, will provide voltage support to raise the voltage at the common coupling point to V. pcc The minimum current capacity required at that time.

[0090] 3. A quantitative method for determining the overcurrent capacity requirement of grid-type converters under different constraints.

[0091] The overcurrent capacity of a grid-type converter should simultaneously meet multiple requirements. Therefore, considering the transient stability and voltage support capabilities mentioned above, the overcurrent capacity of the converter satisfies the following expression:

[0092] I max >max[I sta ,I sup ]

[0093] Where I max The minimum overcurrent capacity required for a grid-type converter when considering both transient stability and voltage support capability.

[0094] After obtaining the overcurrent capacity required for the converter to meet transient stability and voltage support capabilities, it is clear that taking the maximum value among them can satisfy both requirements.

[0095] Another aspect of the present invention provides a quantitative analysis device for the overcurrent capacity requirement of a grid-type converter, comprising:

[0096] The first quantification relationship construction module is used to establish the first quantification relationship between the minimum overcurrent capacity and the critical clearing time required for the converter to meet the transient stability target based on the equal area rule.

[0097] The second quantization relationship construction module is used to establish a second quantization relationship between the minimum overcurrent capacity required for the converter to meet the common coupling point voltage support target and the common coupling point voltage, based on the voltage and current phasor diagram when the converter exerts its maximum voltage support capacity.

[0098] The overcurrent capacity requirement acquisition module is used to calculate the minimum overcurrent capacity required to meet the transient stability target and the common coupling point voltage support target based on the power grid conditions outside the converter and its own key parameters, respectively, according to the first quantification relationship and the second quantification relationship. The maximum value of the two minimum overcurrent capacities is taken to obtain the overcurrent capacity requirement that takes into account both transient stability and voltage support under given parameters.

[0099] Another aspect of the present invention provides a quantitative analysis system for the overcurrent capacity requirement of a grid-type converter, comprising: a computer-readable storage medium and a processor;

[0100] The computer-readable storage medium is used to store executable instructions;

[0101] The processor is used to read executable instructions stored in the computer-readable storage medium and execute the quantitative analysis method for the overcurrent capacity requirement of the grid-type converter described in the first aspect.

[0102] In another aspect, the present invention provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the quantitative analysis method for the overcurrent capacity requirements of a grid-type converter as described in the first aspect.

[0103] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0104] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0105] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0106] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0107] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for quantitatively analyzing the overcurrent capacity requirement of a grid-type converter, characterized in that, Includes the following steps: Based on the equal area rule, a first quantitative relationship is established between the minimum overcurrent capacity required for the converter to meet the transient stability target and the critical clearing time. Based on the voltage-current phasor diagram when the converter exerts its maximum voltage support capability, a second quantitative relationship is established between the minimum overcurrent capability required for the converter to meet the common coupling point voltage support target and the common coupling point voltage. Based on the power grid conditions outside the converter and its own key parameters, the minimum overcurrent capacity required to meet the transient stability target and the voltage support target at the common coupling point is calculated based on the first quantification relationship and the second quantification relationship respectively. The maximum value of the two minimum overcurrent capacities is taken to obtain the overcurrent capacity requirement that takes into account both transient stability and voltage support capacity under given parameters. The converter has a minimum overcurrent capacity I required to meet the transient stability target. sta With critical clearance time t cc The quantization relationship is affected by the following parameters: active power setpoint P0, primary frequency regulation power P △ Short-circuit ratio (SCR), moment of inertia (J), rated angular frequency (ω0), converter terminal electromotive force (E), and grid terminal voltage (V) g ; The first quantization relationship is shown below: （1）； Where P in The virtual axis power satisfies the relation P in = P0 - P △ ; The converter meets the minimum overcurrent capacity I required to support the voltage at the point of common coupling. sup voltage V at common coupling point pcc The quantification relationship is affected by the following parameters: grid short-circuit ratio (SCR), grid-side voltage (V). g The relative distance d between the short-circuit point and the common coupling point, and the ground short-circuit impedance Z. s ; The second quantization relationship is shown below: （2）。 2. The quantitative analysis method for the current capacity requirement of a grid-type converter as described in claim 1, characterized in that, The solution process for the overcurrent capacity requirement that balances transient stability and voltage support capability is as follows: Based on the external power grid operating conditions and converter parameters, the relevant parameters required for the solution are set. These external power grid operating condition parameters include: the short-circuit ratio (SCR) and the grid-side voltage (V). g Rated angular frequency ω0, relative distance d from the short-circuit point to the common coupling point, and ground short-circuit impedance Z s The converter parameters include: active power setpoint P0, primary frequency regulation power P △ , moment of inertia J, converter terminal electromotive force E; performance requirements include: critical clearing time t cc Common coupling point voltage V pcc ; Based on the relevant parameters required in the solution, the minimum overcurrent capacity I required for the converter to meet the transient stability target is obtained according to equations (1) and (2). sta The minimum overcurrent capacity I required for the converter to meet the target of common point of coupling voltage support. sup ; Based on this, the minimum overcurrent capacity I is selected. sta and minimum overcurrent capability I sup The maximum value yields the overcurrent capacity requirement that balances transient stability and voltage support under given parameters. Therefore, the overcurrent capacity I of the grid-type converter is... max The following relation should be satisfied: （3）。 3. A quantitative analysis device for the overcurrent capacity requirement of a grid-type converter, characterized in that, include: The first quantification relationship construction module is used to establish the first quantification relationship between the minimum overcurrent capacity and the critical clearing time required for the converter to meet the transient stability target based on the equal area rule. The second quantization relationship construction module is used to establish a second quantization relationship between the minimum overcurrent capacity required for the converter to meet the common coupling point voltage support target and the common coupling point voltage, based on the voltage and current phasor diagram when the converter exerts its maximum voltage support capacity. The overcurrent capacity requirement acquisition module is used to calculate the minimum overcurrent capacity required to meet the transient stability target and the common coupling point voltage support target based on the power grid conditions outside the converter and its own key parameters, respectively, based on the first quantification relationship and the second quantification relationship. The maximum value of the two minimum overcurrent capacities is taken to obtain the overcurrent capacity requirement that takes into account both transient stability and voltage support under given parameters. The converter has a minimum overcurrent capacity I required to meet the transient stability target. sta With critical clearance time t cc The quantization relationship is affected by the following parameters: active power setpoint P0, primary frequency regulation power P △ Short-circuit ratio (SCR), moment of inertia (J), rated angular frequency (ω0), converter terminal electromotive force (E), and grid terminal voltage (V) g ; The first quantization relationship is shown below: （1）； Where P in The virtual axis power satisfies the relation P in = P0 - P △ ; The converter meets the minimum overcurrent capacity I required to support the voltage at the point of common coupling. sup voltage V at common coupling point pcc The quantification relationship is affected by the following parameters: grid short-circuit ratio (SCR), grid-side voltage (V). g The relative distance d between the short-circuit point and the common coupling point, and the ground short-circuit impedance Z. s ; The second quantization relationship is shown below: （2）。 4. The quantitative analysis device for the current capacity requirement of a grid-type converter as described in claim 3, characterized in that, The overcurrent capacity requirement acquisition module is specifically used for: Based on the external power grid operating conditions and converter parameters, the relevant parameters required for the solution are set. These external power grid operating condition parameters include: the short-circuit ratio (SCR) and the grid-side voltage (V). g Rated angular frequency ω0, relative distance d from the short-circuit point to the common coupling point, and ground short-circuit impedance Z s The converter parameters include: active power setpoint P0, primary frequency regulation power P △ , moment of inertia J, converter terminal electromotive force E; performance requirements include: critical clearing time t cc Common coupling point voltage V pcc ; Based on the relevant parameters required in the solution, the minimum overcurrent capacity I required for the converter to meet the transient stability target is obtained according to equations (1) and (2). sta The minimum overcurrent capacity I required for the converter to meet the target of common point of coupling voltage support. sup ; Based on this, the minimum overcurrent capacity I is selected. sta and minimum overcurrent capability I sup The maximum value yields the overcurrent capacity requirement that balances transient stability and voltage support under given parameters. Therefore, the overcurrent capacity I of the grid-type converter is... max The following relation should be satisfied: （3）。 5. A quantitative analysis system for the overcurrent capacity requirement of a grid-type converter, comprising: Computer-readable storage media and processors; The computer-readable storage medium is used to store executable instructions; The processor is used to read executable instructions stored in the computer-readable storage medium and execute the quantitative analysis method for the overcurrent capacity requirement of the grid-type converter as described in any one of claims 1-2.

6. A non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements a quantitative analysis method for the overcurrent capacity requirements of a grid-type converter as described in any one of claims 1-2.

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