Quantitative analysis method for over-current capability demand of network-forming converter and related device

Abstract

The invention relates to a quantitative analysis method and related device for the overcurrent capability demand of a network-forming converter, and the method comprises the steps: building a quantitative relation between the minimum overcurrent capability and critical clearing time, which are required for enabling the converter to meet a transient stability target, based on an equal-area rule; based on the voltage and current phasor diagram when the converter reaches the maximum voltage support, establishing a quantitative relation between the minimum overcurrent capability required by the converter to meet the common coupling point voltage support target and the common coupling point voltage; according to the external power grid working condition of the converter and the key parameters of the converter, the minimum overcurrent capacity meeting the transient stability and common coupling point voltage supporting capacity key indexes is calculated based on the quantitative relation, and the maximum value of the minimum overcurrent capacity is obtained to meet the requirement for the transient stability, the voltage supporting capacity and the overcurrent capacity under the given parameters. According to the method, the minimum over-current capability of the required transient stability and voltage supporting capability of the network construction type converter can be calculated, and the cost of the network construction type converter is optimized.

Description

Technical Field

[0001] The present invention relates to the field of grid-type converters, and in particular to a quantitative analysis method for current capacity requirements of grid-type converters and a related device. Background Art

[0002] my country's new energy industry is developing rapidly, the penetration rate of distributed generators in the power grid is increasing, and the power system is showing a "double 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 power 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 power grid. There are problems such as inability to form an independent network, poor stability in weak power grid conditions, and inability to provide sufficient voltage support and inertial support.

[0003] In order to solve these problems, the grid-forming (GFM) converter was proposed, which has attracted more attention due to its ability to provide sufficient voltage support and frequency support and strong stability in weak power grids. However, the support capacity of the grid-forming converter is limited by its overcurrent capacity, and increasing the overcurrent capacity may increase the hardware cost. Therefore, a method is needed to determine a suitable overcurrent capacity for the grid-forming converter based on actual conditions.

[0004] At present, due to the low overcurrent capacity of power electronic equipment, grid-type converters usually add current limiting methods to prevent excessive current during operation from causing equipment damage. There are two common current limiting methods. 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 link on the transient stability of the converter under the d-axis priority current limiting strategy. By analyzing the converter power angle curve, the instability mechanism of the converter under the influence of large disturbances is pointed out. Similarly, reference [5] analyzes the transient process of the grid-type converter under large disturbances using the q-axis priority current limiting method. The above two articles only study the influence of d-axis priority and q-axis priority current limiting, respectively. Reference [6] discussed the power angle curve of grid-type converter under different current limiting strategies. By analyzing the phasor diagram of the grid-type converter under the conditions of d-axis priority, q-axis priority, and power factor angle priority, 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 clearly pointed out the quantitative relationship between transient stability and overcurrent capacity.

[0005] On the other hand, the overcurrent capacity of the grid-type converter has an impact on its active support capacity, especially its voltage support capacity. Reference [7] analyzed the impact of current limiting on the voltage support capacity of the grid-type converter by studying the phasor diagram of the grid-type converter under different voltage drop levels, and proposed a method of adding a power reference value limiting link and a variable coefficient reactive voltage droop control to improve the voltage support capacity of the converter under current limiting conditions. Reference [8] proposed a method of removing the reactive voltage droop control link when the voltage drops, and introducing a virtual impedance to limit the current, thereby achieving voltage support under current limiting conditions. The above references all analyzed the impact of current limiting on the voltage support capacity of the grid-type converter, but did not conduct in-depth research on the quantitative relationship between the converter's overcurrent capacity and voltage support capacity.

[0006] In summary, many current studies have analyzed the impact of the converter's overcurrent capacity on its transient stability and voltage support capability, but none of them has further established a method to determine the appropriate overcurrent capacity of a grid-connected converter 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 transient voltage support mechanism and improved fault ride-through control of virtual synchronous machine with current limitation [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 System and Clean Energy, 2022, 38(08): 130-7+43. Summary of the invention

[0016] In order to solve the problem of lack of quantitative analysis means for the overcurrent capacity demand of a grid-type current transformer, the present invention proposes a quantitative analysis method and related devices for the overcurrent capacity demand of a grid-type current transformer.

[0017] A quantitative analysis method for current capacity requirements of a grid-connected converter includes the following steps:

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

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

[0020] According to the grid conditions outside the converter 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 quantitative relationship and the second quantitative relationship, and 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 capability I required to meet the transient stability target. sta and critical clearing time t cc The quantitative relationship is affected by the following parameters: active power given value P0, primary frequency modulation power P △ , grid short-circuit ratio SCR, moment of inertia J, rated angular frequency ω0, converter terminal electromotive force E, grid terminal voltage V g ;

[0022] The first quantitative relationship is as follows:

[0023]

[0024] Where P in is the virtual shaft power, which satisfies the relationship P in =P0-P △ .

[0025] Furthermore, the converter meets the minimum overcurrent capability I required for the common coupling point voltage support target. sup The voltage at the common coupling point V pccThe quantitative 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 as follows:

[0027]

[0028] Furthermore, the process of solving the overcurrent capacity requirement taking into account both transient stability and voltage support capability is as follows:

[0029] According to the external grid conditions and converter parameters of the converter, the relevant parameters required for the solution are set, where the external grid condition parameters include: grid short circuit ratio SCR, grid side voltage V g , rated angular frequency ω0, relative distance d between the short-circuit point and the common coupling point, ground short-circuit impedance Z s ; The converter parameters include: active power given value P0, primary frequency modulation power P △ , moment of inertia J, converter terminal electromotive force E; indicator requirements include: critical clearing time t cc , Common coupling point voltage V pcc ;

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

[0031] On this basis, take the minimum overcurrent capacity I sta and minimum overcurrent capability I sup The maximum value is the overcurrent capacity requirement that takes into account both transient stability and voltage support capability under given parameters. Then the overcurrent capacity of the grid-type converter I max The relationship should be satisfied:

[0032] I max ≥max[I sta ,I sup ] (3).

[0033] A quantitative analysis device for current capacity requirements of a grid-connected converter, comprising:

[0034] A first quantitative relationship building module, used for establishing a first quantitative relationship between a minimum overcurrent capacity and a critical clearing time required for the converter to meet a transient stability target based on an equal area law;

[0035] A second quantitative relationship building module is used to establish a second quantitative relationship between the minimum overcurrent capacity and the common coupling point voltage required for the converter to meet the common coupling point voltage support target based on the voltage and current phasor diagram when the converter exerts the maximum voltage support capability;

[0036] An 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 first quantitative relationship and the second quantitative relationship according to the grid conditions outside the converter and its own key parameters, and take the maximum value of the two minimum overcurrent capacities to obtain the overcurrent capacity requirement that takes into account both transient stability and voltage support capacity under given parameters.

[0037] Furthermore, the converter has a minimum overcurrent capability I required to meet the transient stability target. sta and critical clearing time t cc The quantitative relationship is affected by the following parameters: active power given value P0, primary frequency modulation power P △ , grid short-circuit ratio SCR, moment of inertia J, rated angular frequency ω0, converter terminal electromotive force E, grid terminal voltage V g ;

[0038] The first quantitative relationship is as follows:

[0039]

[0040] Where P in is the virtual shaft power, which satisfies the relationship P in =P0-P △ .

[0041] Furthermore, the converter meets the minimum overcurrent capability I required for the common coupling point voltage support target. sup The voltage at the common coupling point V pcc The quantitative 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 as follows:

[0043]

[0044] Furthermore, the current capacity requirement acquisition module is specifically used to:

[0045] According to the external grid conditions and converter parameters of the converter, the relevant parameters required for the solution are set, where the external grid condition parameters include: grid short circuit ratio SCR, grid side voltage V g, rated angular frequency ω0, relative distance d between the short-circuit point and the common coupling point, ground short-circuit impedance Z s ; The converter parameters include: active power given value P0, primary frequency modulation power P △ , moment of inertia J, converter terminal electromotive force E; indicator requirements include: critical clearing time t cc , Common coupling point voltage V pcc ;

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

[0047] On this basis, take the minimum overcurrent capacity I sta and minimum overcurrent capability I sup The maximum value is the overcurrent capacity requirement that takes into account both transient stability and voltage support capability under given parameters. Then the overcurrent capacity of the grid-type converter I max The relationship should be satisfied:

[0048]

[0049] A quantitative analysis system for overcurrent capacity requirements of a grid-type converter, comprising: 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 the executable instructions stored in the computer-readable storage medium and execute the quantitative analysis method of the overcurrent capacity requirement of the grid-connected converter.

[0052] A non-transitory computer-readable storage medium stores a computer program, which, when executed by a processor, implements the quantitative analysis method for the overcurrent capacity requirement of a grid-connected current transformer.

[0053] The present invention takes transient stability and voltage support capability as the main considerations, and establishes the quantitative relationship between the current limiting value of the converter and physical quantities such as the short-circuit ratio, critical clearing time, and grid voltage based on the equal-area rule and phasor diagram analysis, so that the minimum overcurrent capacity of the grid-forming converter with the required transient stability and voltage support capability can be calculated through these conditions, thereby optimizing the cost of the grid-forming converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 A flowchart of a method for quantitatively analyzing the overcurrent capacity requirements of a grid-connected converter according to an embodiment of the present invention;

[0055] Figure 2 This is a control strategy block diagram of a grid-connected converter based on VSG control;

[0056] Figure 3 The voltage and current loop control block diagram of adding current limiting link to the grid-type converter;

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

[0058] Figure 5 is the power angle curve before and after the converter current limiting;

[0059] Figure 6 It is a simplified grid-connected model;

[0060] Figure 7 The phasor diagram for the converter when it exerts its maximum voltage support capability;

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

[0062] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

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

[0064] In terms of transient stability, the quantitative relationship between the minimum overcurrent capacity and the critical clearing time required for the converter to meet the transient stability target is established based on the equal area rule. In terms of voltage support capacity, based on the voltage and current phasor diagram when the converter exerts the maximum voltage support capacity, the quantitative relationship between the minimum overcurrent capacity and the voltage at the common coupling point required for the converter to meet the voltage support target of the common coupling point is established. Finally, according to the grid conditions outside the converter and its own key parameters, the minimum overcurrent capacity that meets the key indicators of transient stability capability and common coupling point voltage support capability is calculated based on the aforementioned quantitative relationship, and the maximum value is taken to obtain the overcurrent capacity requirement that takes into account both transient stability and voltage support capability under given parameters.

[0065] First, the basic control model, principle and strategy of the embodiment of the present invention are described:

[0066] The embodiment of the present invention takes a grid-type converter control strategy based on virtual synchronous generator (VSG) control as an example. Figure 2 As shown. The control part mainly includes reactive power-voltage control link and active power-frequency control link. It is necessary to emphasize the reactive power-voltage control link. This control strategy adopts voltage-current dual-loop control. By adding a limiting link in the dual loop, the current reference value is limited to achieve the purpose of limiting. Figure 3 As shown. There are many kinds of current limiting methods, 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, so the present invention is based on this current limiting method. The current phasor diagram of this method is shown in Figure 4 Reference [6] studies the power angle characteristics and power angle curves of grid-connected converters using different current limiting methods. The reference states that the current reference value expression after using the power factor angle priority current limiting method is as follows:

[0067]

[0068] Correspondingly, it can be seen from the literature [6] that the power angle characteristic of the converter is determined by the following formula:

[0069]

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

[0071] Based on the above control model and principle, quantitative analysis of grid-connected converter is carried out:

[0072] 1. Quantitative analysis of the impact of overcurrent capacity on transient stability of grid-connected converters during low voltage ride-through

[0073] Based on the power angle characteristics after current limiting, the power angle curve of the converter can be drawn, such as Figure 5 shown. Figure 5The figure also shows the operating point operation when the voltage drops under the condition of stable operation of the converter. The current limiting link affects the power angle curve of the grid-type converter, thus affecting its transient stability. Figure 5 Before analyzing its impact, it should be noted that, considering the actual application situation, it is necessary to make the obtained I max There is a certain margin, so the worst case should be considered. Therefore, the following premise is assumed: the low voltage ride-through strategy fails due to the failure of the relevant detection of voltage drop, and the transient stability of the grid-type converter only depends on the current limiting strategy; in addition, the damping link that also helps to improve transient stability is ignored, and the most extreme case of voltage drop to 0 is considered.

[0074] Figure 5 In the figure, point a is the steady-state operating point. When the most serious voltage drop occurs, that is, 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, so that the converter power angle continues to increase until the fault at point c is cleared; after the fault is cleared, the active power output is no longer 0. Since the power angle is large at this time, the current is limited, so the current limiting mode is entered, and the operating point moves to the power angle curve during current limiting. At the moment of clearing, the operating point moves from point c to point d; after the fault is cleared, the converter active power command is less than the actual active power output, but the converter angular frequency is still greater than the rated angular frequency. Due to the existence of the virtual inertia link, the angular frequency will not decrease immediately, and the power angle will continue to increase until the angular frequency is equal to the rated value, that is, point e; after reaching point e, the converter angular frequency is still less than the rated angular frequency, the converter power angle begins to decrease, and finally returns to the steady-state operating point.

[0075] For the above transient process, it should be pointed out that the equal area rule commonly used in transient stability analysis of synchronous machines is also applicable to grid-type converters. When the acceleration area in the transient process is exactly equal to the maximum deceleration area, that is, when point e moves to point e', the converter remains stable. c If it is further increased, the acceleration area will be larger than the deceleration area, and the converter will become unstable. Based on this, the relationship between the current limit value and physical quantities such as short-circuit ratio, critical clearing time, and virtual shaft power can be listed, and the equation group is as follows:

[0076]

[0077] where δ cc is the critical clearance angle, δ0 is the initial power angle, δ m To maintain the maximum power angle that the working point can reach under the premise of stability, P in is the virtual shaft power, V g is the grid terminal voltage, I staWhen considering transient stability, the current limiting amplitude of the grid-type converter is: J is the moment of inertia, ω0 is the rated angular frequency, t cc is the critical clearing time, X is the grid impedance after ignoring the resistance, and SCR is the grid short circuit ratio.

[0078] Further, we can get the following expression:

[0079]

[0080] Based on this formula, the virtual shaft power P can be obtained when the virtual shaft power P is known. in , grid short circuit ratio SCR, critical clearing time t cc As well as the converter control parameters of rotational 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 impact of overcurrent capacity on the voltage support capability of grid-connected converters during low voltage ride-through

[0082] Figure 6 The figure shows a simplified grid-connected model. When the grid voltage drops seriously, in order to give full play to the voltage support capability of the converter, the droop link is disconnected and the active power command and the virtual internal potential command are directly given. The maximum voltage support of the converter under current limiting conditions can be achieved. The circuit phasor diagram at this time is shown in Figure 7 As shown. Based on this, we can get the expression:

[0083]

[0084] Among them, V pcc is the support target of the voltage at the point of common coupling (PCC), V g is the grid terminal voltage, I sup When considering the voltage support capability, the current limiting amplitude of the grid-type converter is Z g is the grid side impedance. The condition involved in this expression is the ideal grid voltage drop, that is, V g , if a three-phase ground short circuit fault occurs at the same position of the line as a condition, that is, Figure 8 In the case shown in (a), the expression will change. The Thevenin equivalent circuit can be obtained as follows: Figure 8 As shown in (b).

[0085]

[0086] Where V g ' is the Thevenin equivalent grid voltage, Zg ' is the Thevenin equivalent grid impedance, d is the relative distance from the short-circuit point to the common coupling point, Z s is the ground short-circuit impedance. By combining the equations in this group of equations, the expression of the current limiting amplitude of the grid-type converter can be obtained:

[0087]

[0088] In the formula, I sup is the current limiting amplitude of the grid-connected converter when considering the voltage support capability, V pcc The target voltage for the common coupling point is V g is the grid side voltage.

[0089] Based on this formula, when the short-circuit ratio is known, it can be calculated that when a three-phase ground short circuit occurs at a certain position in the line, the grid-type converter plays a voltage support role and supports the voltage at the common coupling point to V pcc The minimum current capability required.

[0090] 3. Quantification method of grid-connected converter overcurrent capacity requirements under different constraints

[0091] The overcurrent capacity of the grid-connected converter should meet multiple requirements at the same time. Therefore, considering the transient stability and voltage support capability mentioned above, the overcurrent capacity of the converter satisfies the expression:

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

[0093] Among them I max The minimum overcurrent capacity required for a grid-type converter when both transient stability and voltage support capability are considered comprehensively.

[0094] After obtaining the overcurrent capacity required by the converter to meet transient stability and voltage support capacity respectively, it is obvious that taking the maximum value can meet both requirements.

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

[0096] A first quantitative relationship building module, used for establishing a first quantitative relationship between a minimum overcurrent capacity and a critical clearing time required for the converter to meet a transient stability target based on an equal area law;

[0097] A second quantitative relationship building module is used to establish a second quantitative relationship between the minimum overcurrent capacity and the common coupling point voltage required for the converter to meet the common coupling point voltage support target based on the voltage and current phasor diagram when the converter exerts the maximum voltage support capability;

[0098] An 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 first quantitative relationship and the second quantitative relationship according to the grid conditions outside the converter and its own key parameters, and take the maximum value of the two minimum overcurrent capacities to obtain the overcurrent capacity requirement that takes into account both transient stability and voltage support capacity under given parameters.

[0099] Another aspect of the present invention provides a quantitative analysis system for the overcurrent capacity requirement of a grid-connected 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 the executable instructions stored in the computer-readable storage medium to execute the quantitative analysis method of the overcurrent capacity requirement of the grid-connected converter described in the first aspect.

[0102] Another aspect of 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 requirement of the grid-connected converter described in the first aspect.

[0103] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented in one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that include computer-usable program code.

[0104] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0105] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0106] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0107] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does 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 quantitative analysis method for the overcurrent capacity requirement of a grid-connected converter, characterized in that: The steps include: The first quantitative relationship between the minimum overcurrent capacity and the critical clearing time required for the converter to meet the transient stability target is established based on the equal area rule; Based on the voltage and current phasor diagram when the converter exerts the maximum voltage support capability, a second quantitative relationship between the minimum overcurrent capability and the voltage at the common coupling point required for the converter to meet the voltage support target at the common coupling point is established; According to the grid conditions outside the converter 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 quantitative relationship and the second quantitative relationship, and 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.

2. The quantitative analysis method for the overcurrent capacity requirement of a grid-connected converter according to claim 1, characterized in that: The minimum overcurrent capability I required for the converter to meet the transient stability target sta and critical clearing time t cc The quantitative relationship is affected by the following parameters: active power given value P0, primary frequency modulation power P △ , grid short-circuit ratio SCR, moment of inertia J, rated angular frequency ω0, converter terminal electromotive force E, grid terminal voltage V g ; The first quantitative relationship is as follows: Where P in is the virtual shaft power, which satisfies the relationship P in =P0-P △ .

3. The quantitative analysis method for the current capacity requirement of a grid-connected converter according to claim 2, characterized in that: The converter meets the minimum overcurrent capability I required for the voltage support target at the common coupling point sup The voltage at the common coupling point V pcc The quantitative 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 as follows: 。 4. The quantitative analysis method for the overcurrent capacity requirement of a grid-connected converter according to claim 3, characterized in that: The process of solving the overcurrent capacity requirement taking into account both transient stability and voltage support capability is as follows: According to the external grid conditions and converter parameters of the converter, the relevant parameters required for the solution are set, where the external grid condition parameters include: grid short circuit ratio SCR, grid side voltage V g , rated angular frequency ω0, relative distance d between the short-circuit point and the common coupling point, ground short-circuit impedance Z s ; The converter parameters include: active power given value P0, primary frequency modulation power P △ , moment of inertia J, converter terminal electromotive force E; indicator requirements include: critical clearing time t cc , Common coupling point voltage V pcc ; According to the relevant parameters required in the solution, the minimum overcurrent capacity I required for the converter to meet the transient stability target is obtained based on equations (1) and (2). sta , the minimum overcurrent capability I required for the converter to meet the voltage support target at the common coupling point sup ; On this basis, take the minimum overcurrent capacity I sta and minimum overcurrent capability I sup The maximum value is the overcurrent capacity requirement that takes into account both transient stability and voltage support capability under given parameters. Then the overcurrent capacity of the grid-type converter I max The relationship should be satisfied:

5. A quantitative analysis device for the overcurrent capacity requirement of a grid-connected converter, characterized in that: include: A first quantitative relationship building module, used for establishing a first quantitative relationship between a minimum overcurrent capacity and a critical clearing time required for the converter to meet a transient stability target based on an equal area law; A second quantitative relationship building module is used to establish a second quantitative relationship between the minimum overcurrent capacity and the common coupling point voltage required for the converter to meet the common coupling point voltage support target based on the voltage and current phasor diagram when the converter exerts the maximum voltage support capability; An 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 first quantitative relationship and the second quantitative relationship according to the grid conditions outside the converter and its own key parameters, and take the maximum value of the two minimum overcurrent capacities to obtain the overcurrent capacity requirement that takes into account both transient stability and voltage support capacity under given parameters.

6. The quantitative analysis device for the overcurrent capacity requirement of a grid-connected converter according to claim 5, characterized in that: The minimum overcurrent capability I required for the converter to meet the transient stability target sta and critical clearing time t cc The quantitative relationship is affected by the following parameters: active power given value P0, primary frequency modulation power P △ , grid short-circuit ratio SCR, moment of inertia J, rated angular frequency ω0, converter terminal electromotive force E, grid terminal voltage V g ; The first quantitative relationship is as follows: Where P in is the virtual shaft power, which satisfies the relationship P in =P0-P △ .

7. The quantitative analysis device for the overcurrent capacity requirement of a grid-connected converter according to claim 6, characterized in that: The converter meets the minimum overcurrent capability I required for the voltage support target at the common coupling point sup The voltage at the common coupling point V pcc The quantitative 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 as follows:

8. The quantitative analysis method for the overcurrent capacity requirement of a grid-connected converter as claimed in claim 7, characterized in that: The overcurrent capacity requirement acquisition module is specifically used to: According to the external grid conditions and converter parameters of the converter, the relevant parameters required for the solution are set. The external grid condition parameters include: grid short circuit ratio SCR, grid side voltage V g , rated angular frequency ω0, relative distance d between the short-circuit point and the common coupling point, ground short-circuit impedance Z s ; The converter parameters include: active power given value P0, primary frequency modulation power P △ , moment of inertia J, converter terminal electromotive force E; indicator requirements include: critical clearing time t cc , Common coupling point voltage V pcc ; According to the relevant parameters required in the solution, the minimum overcurrent capacity I required for the converter to meet the transient stability target is obtained based on equations (1) and (2). sta , the minimum overcurrent capability I required for the converter to meet the voltage support target at the common coupling point sup ; On this basis, take the minimum overcurrent capacity I sta and minimum overcurrent capability I sup The maximum value is the overcurrent capacity requirement that takes into account both transient stability and voltage support capability under given parameters. Then the overcurrent capacity of the grid-type converter I max The relationship should be satisfied:

9. A quantitative analysis system for current capacity requirements of a grid-connected converter, comprising: A computer readable storage medium and a processor; The computer-readable storage medium is used to store executable instructions; The processor is used to read the executable instructions stored in the computer-readable storage medium and execute the quantitative analysis method of the overcurrent capacity requirement of the grid-type converter according to any one of claims 1 to 4.

10. 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 requirement of a grid-connected converter according to any one of claims 1 to 4.

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