Method, device, medium and terminal for evaluating voltage strength of power grid at receiving end

Abstract

The present application discloses a method and device, medium, and terminal for evaluating the voltage strength of a power grid at the receiving end, which relates to the technical field of power systems. The main purpose is to improve the current problem that the accuracy of evaluating the voltage strength of the power grid at the receiving end based on the short-circuit ratio is low due to the substantial increase in the proportion of new energy power generation systems connected to the power grid at the receiving end, which changes the operating characteristics of the power grid. It includes: in response to an evaluation instruction for the voltage strength of the power grid at the receiving end, obtaining a simulated jump voltage after the fault of the target DC inverter bus is cleared; calculating the voltage stiffness of the target DC inverter bus based on the simulated jump voltage, the voltage stiffness is used to characterize the ratio between the jump voltage of the target DC inverter bus at the moment of recovery after the DC commutation failure occurs and the no-load voltage of the power grid at the receiving end; determining the voltage strength level of the power grid at the receiving end according to the voltage stiffness.

Description

Technical Field

[0001] The present application relates to the technical field of power systems, and in particular to a method and device, medium, and terminal for evaluating voltage strength of a power grid at a receiving end. Background Art

[0002] With the vigorous development of new energy, more and more large-scale wind and solar energy bases, which are typical of deserts, Gobi and wastelands, are under planning and construction. Since the clean energy resource bases and load centers in my country are distributed inversely, it is necessary to transmit new energy electricity from the clean energy resource bases to the load center areas through high-voltage direct current transmission channels, and then connect the new energy electricity to the receiving-end power grid through the DC inverter bus. With the rapid increase in the number and capacity of DC transmission channels in the receiving-end power grid, an ultra-large-scale multi-feed DC receiving-end power grid has been formed. For the receiving-end power grid, if it is planned to add new high-voltage direct current transmission channels, it is necessary to evaluate the voltage strength of the receiving-end power grid to ensure the stability of large-scale new energy power transmission.

[0003] At present, the short circuit ratio (SCR) is usually used to evaluate the voltage strength of the receiving-end power grid. In order to extend the concept of short circuit ratio to multi-infeed DC systems, the CIGRE multi-infeed short circuit ratio (MISCR) can also be used. Furthermore, on the basis of the multi-infeed short circuit ratio, the multi-infeed effective short circuit ratio (MESCR) can also be used.

[0004] However, since the short-circuit ratio is only applicable to the short-circuit current provided by the synchronous power supply (i.e., the synchronous generator power supply, which is the traditional power supply type in the power grid, drives the generator to rotate through mechanical energy, such as water power and thermal power, and then generates electrical energy), it cannot reflect the supporting role of the non-synchronous power supply to the power grid (i.e., the power supply controlled by the power electronic converter, such as wind power generation, photovoltaic power generation and other new energy power generation systems). As the proportion of new energy power generation systems connected to the receiving-end power grid has increased significantly, the operating characteristics of the power grid have changed, resulting in the low accuracy of the above-mentioned assessment of the voltage strength of the receiving-end power grid based on the short-circuit ratio. Summary of the invention

[0005] In view of this, the present application provides a method and device, medium, and terminal for evaluating the voltage strength of the receiving-end power grid. The main purpose is to improve the existing problem of low accuracy in evaluating the voltage strength of the receiving-end power grid based on the short-circuit ratio due to a substantial increase in the proportion of new energy power generation systems connected to the receiving-end power grid, which changes the operating characteristics of the power grid.

[0006] According to one aspect of the present application, a method for evaluating the voltage strength of a power grid at a receiving end is provided, comprising:

[0007] In response to an evaluation instruction for a voltage strength of a power grid at a receiving end, a simulated jump voltage after a target DC inverter bus fault is cleared is obtained, wherein the power grid at the receiving end is a power grid at the receiving end fed with a new energy power system;

[0008] The voltage stiffness of the target DC inverter bus is calculated based on the simulated jump voltage, wherein the voltage stiffness is used to characterize the ratio between the jump voltage of the target DC inverter bus at the moment of recovery after the DC commutation failure occurs and the no-load voltage of the receiving-end power grid, and the jump voltage is obtained by subtracting the influence voltage of each other commutation failure DC inverter bus in the receiving-end power grid and the voltage drop caused by reactive power in the target DC inverter bus from the simulated jump voltage;

[0009] The voltage strength level of the power grid at the receiving end is determined according to the voltage stiffness.

[0010] Preferably, the calculating the voltage stiffness of the target DC inverter bus based on the simulated jump voltage includes:

[0011] Based on the following formula, the sum of the influence voltages of the other commutation failure DC inverter buses in the receiving-end power grid is subtracted from the simulated jump voltage to obtain the jump voltage of the target DC inverter bus after removing the influence of multiple commutation failure DCs.

[0012]

[0013] Among them, U L It represents the jump voltage after removing the influence of multiple commutation failure DC, U0 represents the simulated jump voltage, n represents the number of commutation failure DC inverter busbars, VRPS i It represents the voltage reactive power sensitivity index of the ith commutation failure DC inverter bus, Q aci represents the rated reactive power of the i-th DC line;

[0014] The voltage drop caused by reactive power in the target DC inverter bus is subtracted from the jump voltage after removing the impact of multiple commutation failure DC to obtain the jump voltage of the target DC inverter bus at the moment of recovery after the DC commutation failure occurs, wherein the voltage drop is calculated based on the following formula:

[0015]

[0016] Where dU represents the voltage drop, X sys Represents the reactance parameter of the power grid impedance at the receiving end, Q acN Indicates the rated reactive power that the target DC inverter bus needs to absorb from the receiving-end grid when connected to the receiving-end grid, U L Indicates the jump voltage after removing the DC influence of multiple commutation failure.

[0017] Preferably, before the sum of the influence voltages of other commutation failure DC inverter buses in the receiving-end power grid is subtracted from the simulated jump voltage to obtain the jump voltage of the target DC inverter bus after removing the influence of multiple commutation failure DC, the method further includes:

[0018] Based on the following formula, the voltage reactive power sensitivity index of each of the other commutation failure DC inverter buses is calculated respectively:

[0019]

[0020] Among them, VRPS i represents the voltage reactive power sensitivity index of the ith commutation failure DC inverter bus, ΔU represents the voltage change value of the target DC inverter bus, and ΔQ i It represents the reactive power change value of the i-th other commutation failed DC inverter bus.

[0021] Preferably, the step of obtaining the simulated jump voltage after the target DC inverter bus fault is cleared includes:

[0022] In the simulation software for the receiving-end power grid, it is set that the DC inverter busbar where the commutation failure occurs does not resume commutation after the fault is cleared, and the fault parameters are set according to business requirements;

[0023] A simulation operation is performed on the power receiving end power grid, and a simulated jump voltage after the target DC inverter bus fault is cleared is recorded.

[0024] Preferably, determining the voltage strength level of the receiving-end power grid according to the voltage stiffness includes:

[0025] If the voltage stiffness is less than a preset voltage stiffness threshold, it is determined that the voltage strength level of the receiving-end power grid is a low level, and a prompt message prohibiting direct current from being connected to the receiving-end power grid is output;

[0026] If the voltage stiffness is greater than the preset voltage stiffness threshold, it is determined that the voltage strength level of the receiving-end power grid is a high level, and a DC access operation is performed to connect the DC to the receiving-end power grid based on the target DC inverter bus.

[0027] Preferably, if the voltage stiffness is less than a preset voltage stiffness threshold, it is determined that the voltage strength level of the receiving-end power grid is a low level, and after outputting a prompt message prohibiting direct current from being connected to the receiving-end power grid, the method further includes:

[0028] A preset number of phase regulators are added to the receiving-end power grid, and reactive power is output when a commutation failure occurs in the target DC inverter bus.

[0029] According to another aspect of the present application, a device for evaluating voltage strength of a power grid at a receiving end is provided, comprising:

[0030] A simulated jump voltage acquisition module is used to obtain a simulated jump voltage after the target DC inverter bus fault is cleared in response to an evaluation instruction for the voltage strength of the receiving-end power grid, wherein the receiving-end power grid is a receiving-end power grid fed by a new energy power system;

[0031] A voltage stiffness calculation module, used for calculating the voltage stiffness of the target DC inverter bus based on the simulated jump voltage, wherein the voltage stiffness is used to characterize the ratio between the jump voltage of the target DC inverter bus at the moment of recovery after a DC commutation failure occurs and the no-load voltage of the receiving-end power grid, and the jump voltage is obtained by subtracting the influence voltage of each other commutation failure DC inverter bus in the receiving-end power grid and the voltage drop caused by reactive power in the target DC inverter bus from the simulated jump voltage;

[0032] A voltage strength level determination module is used to determine the voltage strength level of the receiving-end power grid according to the voltage stiffness.

[0033] Preferably, the voltage stiffness calculation module is used to:

[0034] Based on the following formula, the sum of the influence voltages of the other commutation failure DC inverter buses in the receiving-end power grid is subtracted from the simulated jump voltage to obtain the jump voltage of the target DC inverter bus after removing the influence of multiple commutation failure DCs.

[0035]

[0036] Among them, U L It represents the jump voltage after removing the influence of multiple commutation failure DC, U0 represents the simulated jump voltage, n represents the number of commutation failure DC inverter busbars, VRPS i It represents the voltage reactive power sensitivity index of the ith commutation failure DC inverter bus, Q aci represents the rated reactive power of the i-th DC line;

[0037] The voltage drop caused by reactive power in the target DC inverter bus is subtracted from the jump voltage after removing the impact of multiple commutation failure DC to obtain the jump voltage of the target DC inverter bus at the moment of recovery after the DC commutation failure occurs, wherein the voltage drop is calculated based on the following formula:

[0038]

[0039] Where dU represents the voltage drop, X sysRepresents the reactance parameter of the power grid impedance at the receiving end, Q acN Indicates the rated reactive power that the target DC inverter bus needs to absorb from the receiving-end grid when connected to the receiving-end grid, U L Indicates the jump voltage after removing the DC influence of multiple commutation failure.

[0040] Preferably, the voltage stiffness calculation module is also used for:

[0041] Based on the following formula, the voltage reactive power sensitivity index of each of the other commutation failure DC inverter buses is calculated respectively:

[0042]

[0043] Among them, VRPS i represents the voltage reactive power sensitivity index of the ith commutation failure DC inverter bus, ΔU represents the voltage change value of the target DC inverter bus, and ΔQ i It represents the reactive power change value of the i-th other commutation failed DC inverter bus.

[0044] Preferably, the simulated jump voltage acquisition module is used to:

[0045] In the simulation software for the receiving-end power grid, it is set that the DC inverter busbar where the commutation failure occurs does not resume commutation after the fault is cleared, and the fault parameters are set according to business requirements;

[0046] A simulation operation is performed on the power receiving end power grid, and a simulated jump voltage after the target DC inverter bus fault is cleared is recorded.

[0047] Preferably, the voltage intensity level determination module includes:

[0048] A DC access prevention unit, configured to determine that the voltage strength level of the receiving-end power grid is a low level if the voltage stiffness is less than a preset voltage stiffness threshold, and output a prompt message prohibiting DC access to the receiving-end power grid;

[0049] The DC access allowing unit is used to determine that the voltage strength level of the receiving-end power grid is a high level if the voltage stiffness is greater than the preset voltage stiffness threshold, and perform a DC access operation to connect the DC to the receiving-end power grid based on the target DC inverter bus.

[0050] Preferably, the DC access blocking unit is further used for:

[0051] A preset number of phase regulators are added to the receiving-end power grid, and reactive power is output when a commutation failure occurs in the target DC inverter bus.

[0052] According to another aspect of the present application, a storage medium is provided, in which at least one executable instruction is stored, and the executable instruction enables a processor to execute operations corresponding to the above-mentioned method for evaluating the voltage strength of the power grid at the receiving end.

[0053] According to another aspect of the present application, a terminal is provided, comprising: a processor, a memory, a communication interface and a communication bus, wherein the processor, the memory and the communication interface communicate with each other through the communication bus;

[0054] The memory is used to store at least one executable instruction, and the executable instruction enables the processor to execute operations corresponding to the above-mentioned method for evaluating the voltage strength of the power grid at the power receiving end.

[0055] By means of the above technical solution, the technical solution provided by the embodiment of the present application has at least the following advantages:

[0056] The present application provides a method and device, medium, and terminal for evaluating the voltage strength of a receiving-end power grid. First, in response to an evaluation instruction for the voltage strength of a receiving-end power grid, a simulated jump voltage after a target DC inverter bus fault is cleared is obtained, wherein the receiving-end power grid is a receiving-end power grid fed by a new energy power system; secondly, based on the simulated jump voltage, a voltage stiffness of the target DC inverter bus is calculated, wherein the voltage stiffness is used to characterize the ratio between the jump voltage of the target DC inverter bus at the moment of recovery after a DC commutation failure occurs and the no-load voltage of the receiving-end power grid; the jump voltage is obtained by subtracting the influence voltages of each other DC inverter bus with commutation failure in the receiving-end power grid and the voltage drop caused by reactive power in the target DC inverter bus from the simulated jump voltage; finally, the voltage strength level of the receiving-end power grid is determined according to the voltage stiffness. Compared with the prior art, the embodiment of the present application utilizes the voltage stiffness of the target DC inverter bus (that is, the ratio between the jump voltage of the target DC inverter bus at the moment of recovery after the DC commutation failure and the no-load voltage of the receiving-end power grid) to determine the voltage strength level of the receiving-end power grid fed by the new energy power system, thereby overcoming the problem that the grid operation characteristics are changed due to the increase in the proportion of new energy power generation systems connected to the grid in the receiving-end power grid, which leads to the inability to accurately assess the voltage strength of the receiving-end power grid, and improves the assessment accuracy of the voltage strength of the receiving-end power grid; and on the basis of the simulated jump voltage, the impact voltages of each other DC inverter bus with commutation failure in the receiving-end power grid and the voltage drop caused by reactive power in the target DC inverter bus are subtracted to obtain the jump voltage, taking into account the transient voltage stability of the receiving-end power grid and the mutual influence between DCs in a system with multiple DC feeds, further improving the assessment accuracy of the voltage strength of the receiving-end power grid.

[0057] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present application. Also, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0059] Figure 1 A flow chart of a method for evaluating voltage strength of a power grid at a receiving end provided in an embodiment of the present application is shown;

[0060] Figure 2 A flow chart of another method for evaluating the voltage strength of a power grid at a receiving end provided in an embodiment of the present application is shown;

[0061] Figure 3 A schematic diagram of a DC recovery circuit provided in an embodiment of the present application is shown;

[0062] Figure 4 A DC inverter bus voltage jump waveform diagram provided in an embodiment of the present application is shown;

[0063] Figure 5 A schematic diagram of transient simulation results provided by an embodiment of the present application is shown;

[0064] Figure 6 A block diagram of a device for evaluating voltage strength of a power grid at a receiving end provided in an embodiment of the present application is shown;

[0065] Figure 7 A schematic diagram of the structure of a terminal provided in an embodiment of the present application is shown. DETAILED DESCRIPTION

[0066] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0067] At the same time, it should be understood that for the convenience of description, the sizes of the various parts shown in the drawings are not drawn according to the actual proportional relationship.

[0068] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the present application, its application, or uses.

[0069] Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered as part of the specification.

[0070] It should be noted that like reference numerals and letters refer to similar items in the following figures, and therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0071] The embodiments of the present application can be applied to computer systems / servers, which can operate with many other general or special computing system environments or configurations. Examples of well-known computing systems, environments and / or configurations suitable for use with computer systems / servers include, but are not limited to: personal computer systems, server computer systems, thin clients, thick clients, handheld or laptop devices, microprocessor-based systems, set-top boxes, programmable consumer electronics, network personal computers, small computer systems, large computer systems, and distributed cloud computing technology environments including any of the above systems, etc.

[0072] Computer systems / servers may be described in the general context of computer system executable instructions (such as program modules) executed by a computer system. In general, program modules may include routines, programs, object programs, components, logic, data structures, etc., which perform specific tasks or implement specific abstract data types. Computer systems / servers may be implemented in a distributed cloud computing environment where tasks are performed by remote processing devices linked through a communication network. In a distributed cloud computing environment, program modules may be located on local or remote computing system storage media including storage devices.

[0073] The present application embodiment provides a method for evaluating the voltage strength of a power grid at a receiving end, such as Figure 1 As shown, the method includes:

[0074] 101. In response to an evaluation instruction for a voltage strength of a power grid at a power receiving end, a simulated jump voltage after a target DC inverter bus fault is cleared is obtained.

[0075] Among them, the receiving-end power grid is a receiving-end power grid fed by a new energy power system. It can be understood that since the clean energy resource base is often distributed inversely with the load center, it is necessary to transmit the new energy power from the clean energy resource base to the load center area through a high-voltage direct current transmission channel, and then connect the new energy power to the receiving-end power grid through a direct current inverter bus; the simulated jump voltage is obtained based on the simulation software. In the embodiment of the present application, the current execution end can be a voltage strength assessment module of the receiving-end power grid. Before planning to add a new high-voltage direct current transmission channel, the voltage strength of the receiving-end power grid is assessed to determine whether it can be connected to direct current, so as to avoid large voltage fluctuations in the receiving-end power grid caused by direct access to direct current, which affects the stable operation of the receiving-end power grid.

[0076] It should be noted that the method for evaluating the voltage strength of the receiving-end power grid provided in the embodiment of the present application is not only applicable to the receiving-end power grid fed by the new energy power system, but can also be used for the traditional receiving-end power grid.

[0077] 102. Calculate the voltage stiffness of the target DC inverter bus based on the simulated jump voltage.

[0078] Among them, voltage stiffness is used to characterize the ratio between the jump voltage of the target DC inverter bus at the moment of recovery after the DC commutation failure and the no-load voltage of the receiving-end power grid; the jump voltage is obtained by subtracting the impact voltage of each other commutation failure DC inverter bus in the receiving-end power grid and the voltage drop caused by reactive power in the target DC inverter bus on the basis of the simulated jump voltage. In the embodiment of the present application, based on the infinite bus and in combination with the transient voltage stability of the receiving-end power grid, based on the Thevenin equivalent principle, the ratio of the DC inverter bus port voltage to the no-load voltage of the receiving-end power grid is used as a judgment index of voltage stiffness to determine the voltage strength level of the receiving-end power grid fed by the new energy power system, thereby overcoming the problem that the grid operation characteristics are changed due to the increase in the proportion of new energy power generation systems connected to the grid in the receiving-end power grid, which leads to the inability to accurately evaluate the voltage strength of the receiving-end power grid; and on the basis of the simulated jump voltage, the impact voltage of each other DC inverter bus with commutation failure in the receiving-end power grid and the voltage drop caused by reactive power in the target DC inverter bus are subtracted to obtain the jump voltage, taking into account the transient voltage stability of the receiving-end power grid and the mutual influence between DC in a system with multiple DC feeds, thereby improving the evaluation accuracy of the voltage strength of the receiving-end power grid.

[0079] 103. Determine the voltage strength level of the receiving-end power grid based on the voltage stiffness.

[0080] In the embodiment of the present application, since the voltage stiffness is the ratio between the jump voltage of the target DC inverter bus at the moment of recovery after the DC commutation failure and the no-load voltage of the receiving-end power grid, if the no-load voltage of the receiving-end power grid is large enough, the deviation between the voltage after the DC connection and the no-load voltage will not be large, which is reflected in a larger voltage stiffness. Based on this, the voltage strength level of the receiving-end power grid can be divided by setting a voltage stiffness threshold.

[0081] Compared with the prior art, the embodiment of the present application utilizes the voltage stiffness of the target DC inverter bus (that is, the ratio between the jump voltage of the target DC inverter bus at the moment of recovery after the DC commutation failure and the no-load voltage of the receiving-end power grid) to determine the voltage strength level of the receiving-end power grid fed by the new energy power system, thereby overcoming the problem that the grid operation characteristics are changed due to the increase in the proportion of new energy power generation systems connected to the grid in the receiving-end power grid, which leads to the inability to accurately assess the voltage strength of the receiving-end power grid, and improves the assessment accuracy of the voltage strength of the receiving-end power grid; and on the basis of the simulated jump voltage, the impact voltages of each other DC inverter bus with commutation failure in the receiving-end power grid and the voltage drop caused by reactive power in the target DC inverter bus are subtracted to obtain the jump voltage, taking into account the transient voltage stability of the receiving-end power grid and the mutual influence between DCs in a system with multiple DC feeds, further improving the assessment accuracy of the voltage strength of the receiving-end power grid.

[0082] The present application embodiment provides another method for evaluating the voltage strength of the power grid at the receiving end, such as Figure 2 As shown, the method includes:

[0083] 201. Obtain a simulated jump voltage after a target DC inverter bus fault is cleared.

[0084] In an embodiment of the present application, first, in the simulation software for the receiving-end power grid, all DC inverter buses that have commutation failures are set to not restore commutation after the fault is cleared. Specifically, this can be achieved by modifying the control parameters or fault recovery strategy of the DC inverter bus. Further, the fault parameters are set according to business requirements. For example, the fault type can be selected as a three-phase short circuit fault of the target DC inverter bus, the fault duration is 100 milliseconds, and the fault is cleared after 100 milliseconds. Further, based on the above settings, simulation operations are performed, and the simulated jump voltage U0 after the target DC inverter bus fault is cleared is recorded.

[0085] It should be noted that, since the dynamic behaviors of the load, new energy units and synchronous generators have been combined in the simulation process, the simulated jump voltage U0 also reflects the impact of the above dynamic behaviors on the simulated jump voltage U0. In addition, in the simulation process, it is assumed that other DC systems have no direct impact on the voltage jump of the target DC inverter bus, or their impact is negligible. Therefore, in the voltage stiffness calculation, the simulated jump voltage U0 cannot be used as the no-load voltage of the receiving-end power grid. It is understandable that if the fault causes the DC inverter bus to have N-1 (i.e., a DC line is out of operation), then in the subsequent calculations, it is necessary to re-evaluate the voltage stiffness and stability of the system according to the N-1 condition, that is, it is necessary to reset the simulation conditions, consider the impact of the missing DC line on the system, and re-execute the simulation operation.

[0086] Correspondingly, step 201 of the embodiment includes: setting in the simulation software for the receiving-end power grid that the DC inverter bus that has failed to switch phase does not resume switching after the fault is cleared, and setting fault parameters according to business requirements; executing the simulation operation for the receiving-end power grid, and recording the simulated jump voltage after the target DC inverter bus fault is cleared.

[0087] 202. Calculate the voltage reactive power sensitivity index of each other commutation failed DC inverter busbar respectively.

[0088] Specifically, the voltage reactive power sensitivity index of other commutation failure DC inverter buses can be calculated based on the following formula:

[0089]

[0090] Among them, VRPS i represents the voltage reactive power sensitivity index of the ith commutation failure DC inverter bus, ΔU represents the voltage change value of the target DC inverter bus, and ΔQ i It represents the reactive power change value of the i-th other commutation failed DC inverter bus.

[0091] It should be noted that the voltage reactive power sensitivity index is used to characterize the influence of reactive power changes at a certain node in the receiving-end power grid on the voltage changes at other nodes, that is, after a certain amount of reactive power is injected into a certain node in the receiving-end power grid, the voltage change at other nodes, that is, the ratio of voltage change to reactive power change. i The larger the value, the greater the impact on the target DC inverter bus voltage when the same reactive power changes occur in the i-th DC inverter bus. In addition, the voltage reactive power sensitivity index can be obtained from the Jacobian matrix of power and voltage. The Jacobian matrix can be expressed as the following matrix:

[0092]

[0093] Among them, U j represents the voltage of the jth DC inverter bus in the receiving end grid, Q i It represents the reactive power of the i-th DC inverter bus in the receiving-end power grid. Assume that there are m nodes in the receiving-end power grid, of which the k-th node is the target DC inverter bus and the i-th node is the DC inverter bus of other DC converter stations. J(Q,U) ik Represents the element in the i-th row and k-th column of the Jacobian matrix.

[0094] 203. Calculate the jump voltage of the target DC inverter bus after removing the DC influence of multi-phase commutation failure.

[0095] Specifically, based on the following formula, the sum of the voltages affected by the DC inverter buses with other commutation failures in the receiving-end power grid can be subtracted from the simulated jump voltage to obtain the jump voltage of the target DC inverter bus after removing the influence of multiple commutation failures.

[0096]

[0097] Among them, U L It represents the jump voltage after removing the influence of multiple commutation failure DC, U0 represents the simulated jump voltage, n represents the number of commutation failure DC inverter busbars, VRPS i It represents the voltage reactive power sensitivity index of the ith commutation failure DC inverter bus, Q aci represents the rated reactive power of the ith DC line.

[0098] It should be noted that in a receiving-end power grid with multiple DC feeds, when a DC line fails to commutate, the DC current cannot be maintained, and the voltage and current phase relationship on the AC side changes, so that the receiving-end power grid needs to provide more reactive power to support the voltage, resulting in the line needing to absorb a large amount of reactive power, which in turn affects other DC lines to fail to commutate at the same time. This is the chain reaction of the receiving-end power grid with multiple DC feeds when the commutation fails. Furthermore, during the fault period, the active power and reactive power of the DC are both 0. At the moment of fault clearance, the recovery speed of the active power is much slower than the recovery speed of the reactive power. Therefore, it can be considered that the reactive power is restored instantly, while the active power is not restored. The assessment at this time is a conservative estimate of the voltage stability. Therefore, considering the impact of supporting other DC commutation faults on the voltage stability of the target DC inverter bus connected to the DC, the DC with commutation fault can be regarded as a reactive load. Based on this, in the embodiment of the present application, the influence voltage of each other commutation failure DC inverter bus in the receiving-end power grid is subtracted from the simulated jump voltage, taking into account the mutual influence between DC in the system with multiple DC feeds, which can effectively improve the assessment accuracy of the voltage strength of the receiving-end power grid. In addition, since the influence of load, synchronous motor, new energy and other DC is already included in the jump voltage U after removing the influence of multiple commutation failure DC L Therefore, when calculating the system impedance, there is no need to consider the influence of the above dynamic components, and it is only necessary to use the system impedance consistent with the steady state.

[0099] 204. Calculate the instantaneous jump voltage of the target DC inverter bus after the DC commutation failure occurs.

[0100] Specifically, the voltage drop caused by reactive power in the target DC inverter bus is subtracted from the jump voltage after removing the impact of multiple commutation failure DC, to obtain the jump voltage of the target DC inverter bus at the moment of recovery after the DC commutation failure occurs, wherein the voltage drop is calculated based on the following formula:

[0101]

[0102] Where dU represents the voltage drop, X sys Represents the reactance parameter of the power grid impedance at the receiving end, Q acN Indicates the rated reactive power that the target DC inverter bus needs to absorb from the receiving-end grid when connected to the receiving-end grid, U L Indicates the jump voltage after removing the DC influence of multiple commutation failure.

[0103] It should be noted that, in the early stage of the DC recovery commutation fault of the target DC inverter bus, the reactive power can be approximately considered to have recovered to the rated value, while the active power has not yet recovered. Therefore, when calculating the instantaneous jump voltage of the target DC inverter bus after the DC commutation failure occurs, the Figure 3 The circuit shown is used to calculate, Figure 3 U0 represents the simulated jump voltage, Z sys represents the initial Thevenin equivalent impedance, Z ext Indicates the additional impedance caused by external dynamic components (such as induction motors, etc.). When no DC is connected, the additional impedance Z ext The resulting jump voltage is U L ,according to Figure 3 Circuit, the voltage drop dU caused by the reactive power of the DC system can be expressed as follows:

[0104]

[0105] Among them, X sys Represents the reactance parameter of the power grid impedance at the receiving end, R sys The resistance parameter representing the impedance of the power grid at the receiving end, Q acN Indicates the rated reactive power that the target DC inverter bus needs to absorb from the receiving-end grid when connected to the receiving-end grid, U L Indicates the additional impedance Z ext Furthermore, in high-voltage transmission networks, the line resistance is usually much smaller than the reactance value, so the role of resistance in the system equivalent impedance can be ignored and the pure reactance X can be used. sys To simulate the system equivalent impedance, the voltage drop can be simplified to the following formula.

[0106]

[0107] Furthermore, the instantaneous jump voltage of the target DC inverter bus after the DC commutation failure can be calculated according to the following formula:

[0108] U re =U L -dU

[0109] Among them, U re It indicates the instantaneous jump voltage of the target DC inverter bus after the DC commutation failure occurs. L It represents the jump voltage after removing the DC influence of multi-phase commutation failure, and dU represents the voltage drop caused by reactive power in the target DC inverter bus.

[0110] 205. Calculate the voltage stiffness of the target DC inverter bus in the receiving-end power grid.

[0111] Specifically, the voltage stiffness is determined by the ratio between the jump voltage of the target DC inverter bus at the moment of recovery after the DC commutation failure and the no-load voltage of the power grid at the receiving end, which can be expressed as the following formula:

[0112]

[0113] Among them, K vtg Indicates the voltage stiffness of the target DC inverter bus, U re It indicates the instantaneous jump voltage of the target DC inverter bus after the DC commutation failure occurs. state Indicates the no-load voltage of the power grid at the receiving end.

[0114] In one embodiment of the present application, for further limitation and explanation, step 103 determines the voltage strength level of the receiving-end power grid according to the voltage stiffness, including: if the voltage stiffness is less than a preset voltage stiffness threshold, the voltage strength level of the receiving-end power grid is determined to be a low level, and a prompt message prohibiting DC access to the receiving-end power grid is output; if the voltage stiffness is greater than the preset voltage stiffness threshold, the voltage strength level of the receiving-end power grid is determined to be a high level, and a DC access operation is performed to connect DC to the receiving-end power grid based on the target DC inverter bus.

[0115] Among them, the preset voltage stiffness threshold can be set to 0.8, and can also be adjusted according to the importance of the receiving-end power grid. For example, if the receiving-end power grid is a power grid in important areas such as Beijing and Shanghai, the voltage stiffness threshold can be adjusted to 0.9 or even 0.95, etc., to improve the standard for allowing access to DC, thereby ensuring the stable operation of the receiving-end power grid. In the embodiment of the present application, if the voltage stiffness is less than the preset voltage stiffness threshold, the voltage strength level of the receiving-end power grid is determined to be a low level, that is, the risk of voltage instability caused by access to DC is relatively high. At this time, a prompt message prohibiting DC access can be output; if the voltage stiffness is greater than the preset voltage stiffness threshold, the voltage strength level of the receiving-end power grid is determined to be a high level, that is, the receiving-end power grid is strong enough, and the access to DC has little effect on it, and the risk of voltage instability caused by access to DC is relatively low. At this time, the DC can be directly connected to the receiving-end power grid based on the target DC inverter bus.

[0116] In an embodiment of the present application, further optionally, if the voltage stiffness is less than a preset voltage stiffness threshold, then the voltage strength level of the receiving-end power grid is determined to be a low level, and a prompt message prohibiting DC access to the receiving-end power grid is output, the embodiment method also includes: adding a preset number of phase regulators in the receiving-end power grid, and outputting reactive power when a DC commutation failure occurs in the target DC inverter bus.

[0117] Among them, the role of the phase regulator is similar to that of a generator. When the target DC inverter bus fails to commutate, since it absorbs a large amount of reactive power, multiple phase regulators can be added near the target DC inverter bus to output reactive power, thereby ensuring the stable operation of the receiving-end power grid.

[0118] In a specific embodiment, the real data of a certain power grid is taken as an example to verify the above-mentioned evaluation method of the voltage strength of the receiving-end power grid. In this power grid, the power generation of new energy is about 69 million kilowatts, and the penetration rate of new energy reaches 42.2%; induction motors account for 58% of the loads, and the remaining static loads include constant impedance loads, 53%, constant current loads, 34%, and constant power loads. 13%. In this power grid, there are 13 DC feeds into the receiving-end power grid A, of which 4 DC feeds into the receiving-end power grid B, which belongs to a multi-DC receiving-end power grid. The receiving-end power grid B is selected as the verification object, and its DC type is conventional DC (LCC). The main parameters are shown in Table 1. Table 1 Main parameters of the receiving-end power grid B

[0119]

[0120] Under full connection conditions, the multi-feed short-circuit ratio of the DC inverter bus a of the receiving-end grid B is calculated to be 3.05, which is a relatively strong system. Based on the above-mentioned evaluation method of the voltage strength of the receiving-end grid, firstly, through simulation calculation, it is assumed that the DC voltage has not recovered when the commutation failure occurs. After the short-circuit fault of the target DC inverter bus is cleared, the DC inverter bus voltage of the receiving-end grid B jumps to 0.91pu, and the waveform is as follows: Figure 4 It is known that when a short circuit occurs in the DC inverter bus a, in addition to the commutation failure of the DC inverter bus a, the commutation failures of the DC inverter bus b and the DC inverter bus c will also occur at the same time. Therefore, it is necessary to calculate the VRPS index between the inverter buses of these two DCs and the DC inverter bus a, as shown in Table 2.

[0121] Table 2 VRPS index between different DC system inverter bus and this DC inverter bus

[0122]

[0123] Based on the above method, the voltage stiffness of the DC inverter bus a is calculated to be 0.74, which belongs to a low level of voltage strength.

[0124] Finally, according to Figure 5From the transient simulation results shown, it can be seen that even in the fully connected state, the DC inverter bus a cannot recover from the commutation failure immediately after the short-circuit fault is cleared, but only starts to recover from the commutation fault nearly 400 milliseconds after the fault is cleared. According to the AC voltage waveform, although the bus voltage can be restored to a higher level after the short-circuit fault is cleared, this is because the DC inverter bus a has not recovered and the absorbed reactive power is 0, which cannot reach this level. If the DC inverter bus a begins to recover, it is equivalent to instantly connecting a large number of reactive loads, causing the AC bus voltage to drop sharply. Therefore, the voltage stability of the DC inverter bus a drop point is poor. In summary, the evaluation results obtained based on the short-circuit ratio are not accurate, while the evaluation results obtained based on the above-mentioned evaluation method of the voltage strength of the receiving-end power grid are accurate.

[0125] The present application provides a method for evaluating the voltage strength of a receiving-end power grid. First, in response to an evaluation instruction for the voltage strength of the receiving-end power grid, a simulated jump voltage after a target DC inverter bus fault is cleared is obtained, wherein the receiving-end power grid is a receiving-end power grid fed by a new energy power system; secondly, based on the simulated jump voltage, a voltage stiffness of the target DC inverter bus is calculated, wherein the voltage stiffness is used to characterize the ratio between the jump voltage of the target DC inverter bus at the moment of recovery after a DC commutation failure occurs and the no-load voltage of the receiving-end power grid; the jump voltage is obtained by subtracting the impact voltages of each other DC inverter bus with commutation failure in the receiving-end power grid and the voltage drop caused by reactive power in the target DC inverter bus from the simulated jump voltage; finally, the voltage strength level of the receiving-end power grid is determined according to the voltage stiffness. Compared with the prior art, the embodiment of the present application utilizes the voltage stiffness of the target DC inverter bus (that is, the ratio between the jump voltage of the target DC inverter bus at the moment of recovery after the DC commutation failure and the no-load voltage of the receiving-end power grid) to determine the voltage strength level of the receiving-end power grid fed by the new energy power system, thereby overcoming the problem that the grid operation characteristics are changed due to the increase in the proportion of new energy power generation systems connected to the grid in the receiving-end power grid, which leads to the inability to accurately assess the voltage strength of the receiving-end power grid, and improves the assessment accuracy of the voltage strength of the receiving-end power grid; and on the basis of the simulated jump voltage, the impact voltages of each other DC inverter bus with commutation failure in the receiving-end power grid and the voltage drop caused by reactive power in the target DC inverter bus are subtracted to obtain the jump voltage, taking into account the transient voltage stability of the receiving-end power grid and the mutual influence between DCs in a system with multiple DC feeds, further improving the assessment accuracy of the voltage strength of the receiving-end power grid.

[0126] Furthermore, as a response to the above Figure 1 In order to realize the method shown in the figure, the embodiment of the present application provides a device for evaluating the voltage strength of the power grid at the receiving end, such as Figure 6 As shown, the device comprises:

[0127] A simulation jump voltage acquisition module 31, a voltage stiffness calculation module 32, and a voltage strength level determination module 33;

[0128] A simulated jump voltage acquisition module is used to obtain a simulated jump voltage after the target DC inverter bus fault is cleared in response to an evaluation instruction for the voltage strength of the receiving-end power grid, wherein the receiving-end power grid is a receiving-end power grid fed by a new energy power system;

[0129] A voltage stiffness calculation module, used for calculating the voltage stiffness of the target DC inverter bus based on the simulated jump voltage, wherein the voltage stiffness is used to characterize the ratio between the jump voltage of the target DC inverter bus at the moment of recovery after a DC commutation failure occurs and the no-load voltage of the receiving-end power grid, and the jump voltage is obtained by subtracting the influence voltage of each other commutation failure DC inverter bus in the receiving-end power grid and the voltage drop caused by reactive power in the target DC inverter bus from the simulated jump voltage;

[0130] A voltage strength level determination module is used to determine the voltage strength level of the receiving-end power grid according to the voltage stiffness.

[0131] In a specific application scenario, the voltage stiffness calculation module is used to:

[0132] Based on the following formula, the sum of the influence voltages of the other commutation failure DC inverter buses in the receiving-end power grid is subtracted from the simulated jump voltage to obtain the jump voltage of the target DC inverter bus after removing the influence of multiple commutation failure DCs.

[0133]

[0134] Among them, U L It represents the jump voltage after removing the influence of multiple commutation failure DC, U0 represents the simulated jump voltage, n represents the number of commutation failure DC inverter busbars, VRPS i It represents the voltage reactive power sensitivity index of the ith commutation failure DC inverter bus, Q aci represents the rated reactive power of the i-th DC line;

[0135] The voltage drop caused by reactive power in the target DC inverter bus is subtracted from the jump voltage after removing the impact of multiple commutation failure DC to obtain the jump voltage of the target DC inverter bus at the moment of recovery after the DC commutation failure occurs, wherein the voltage drop is calculated based on the following formula:

[0136]

[0137] Where dU represents the voltage drop, Xsys Represents the reactance parameter of the power grid impedance at the receiving end, Q acN Indicates the rated reactive power that the target DC inverter bus needs to absorb from the receiving-end grid when connected to the receiving-end grid, U L Indicates the jump voltage after removing the DC influence of multiple commutation failure.

[0138] In a specific application scenario, the voltage stiffness calculation module is also used to:

[0139] Based on the following formula, the voltage reactive power sensitivity index of each of the other commutation failure DC inverter buses is calculated respectively:

[0140]

[0141] Among them, VRPS i represents the voltage reactive power sensitivity index of the ith commutation failure DC inverter bus, ΔU represents the voltage change value of the target DC inverter bus, and ΔQ i It represents the reactive power change value of the i-th other commutation failed DC inverter bus.

[0142] In a specific application scenario, the simulated jump voltage acquisition module is used to:

[0143] In the simulation software for the receiving-end power grid, it is set that the DC inverter busbar where the commutation failure occurs does not resume commutation after the fault is cleared, and the fault parameters are set according to business requirements;

[0144] A simulation operation is performed on the power receiving end power grid, and a simulated jump voltage after the target DC inverter bus fault is cleared is recorded.

[0145] In a specific application scenario, the voltage intensity level determination module includes:

[0146] A DC access prevention unit, configured to determine that the voltage strength level of the receiving-end power grid is a low level if the voltage stiffness is less than a preset voltage stiffness threshold, and output a prompt message prohibiting DC access to the receiving-end power grid;

[0147] The DC access allowing unit is used to determine that the voltage strength level of the receiving-end power grid is a high level if the voltage stiffness is greater than the preset voltage stiffness threshold, and perform a DC access operation to connect the DC to the receiving-end power grid based on the target DC inverter bus.

[0148] In a specific application scenario, the DC access blocking unit is further used for:

[0149] A preset number of phase regulators are added to the receiving-end power grid, and reactive power is output when a commutation failure occurs in the target DC inverter bus.

[0150] The present application provides a device for evaluating the voltage strength of a receiving-end power grid. First, in response to an evaluation instruction for the voltage strength of the receiving-end power grid, a simulated jump voltage after a target DC inverter bus fault is cleared is obtained, wherein the receiving-end power grid is a receiving-end power grid fed by a new energy power system; secondly, based on the simulated jump voltage, a voltage stiffness of the target DC inverter bus is calculated, wherein the voltage stiffness is used to characterize the ratio between the jump voltage of the target DC inverter bus at the moment of recovery after a DC commutation failure occurs and the no-load voltage of the receiving-end power grid; the jump voltage is obtained by subtracting the influence voltages of each other DC inverter bus with commutation failure in the receiving-end power grid and the voltage drop caused by reactive power in the target DC inverter bus from the simulated jump voltage; finally, the voltage strength level of the receiving-end power grid is determined according to the voltage stiffness. Compared with the prior art, the embodiment of the present application utilizes the voltage stiffness of the target DC inverter bus (that is, the ratio between the jump voltage of the target DC inverter bus at the moment of recovery after the DC commutation failure and the no-load voltage of the receiving-end power grid) to determine the voltage strength level of the receiving-end power grid fed by the new energy power system, thereby overcoming the problem that the grid operation characteristics are changed due to the increase in the proportion of new energy power generation systems connected to the grid in the receiving-end power grid, which leads to the inability to accurately assess the voltage strength of the receiving-end power grid, and improves the assessment accuracy of the voltage strength of the receiving-end power grid; and on the basis of the simulated jump voltage, the impact voltages of each other DC inverter bus with commutation failure in the receiving-end power grid and the voltage drop caused by reactive power in the target DC inverter bus are subtracted to obtain the jump voltage, taking into account the transient voltage stability of the receiving-end power grid and the mutual influence between DCs in a system with multiple DC feeds, further improving the assessment accuracy of the voltage strength of the receiving-end power grid.

[0151] According to an embodiment of the present application, a storage medium is provided, wherein the storage medium stores at least one executable instruction, and the computer executable instruction can execute the method for evaluating the voltage strength of the power grid at the receiving end in any of the above method embodiments.

[0152] Based on this understanding, the technical solution of the present application can be embodied in the form of a software product, which can be stored in a non-volatile storage medium (which can be a CD-ROM, a USB flash drive, a mobile hard disk, etc.), and includes a number of instructions for enabling a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each implementation scenario of the present application.

[0153] Figure 7 A schematic diagram of the structure of a terminal provided according to an embodiment of the present application is shown, and the specific embodiment of the present application does not limit the specific implementation of the terminal.

[0154] like Figure 7 As shown, the terminal may include: a processor (processor) 402 , a communication interface (Communications Interface) 404 , a memory (memory) 406 , and a communication bus 408 .

[0155] The processor 402 , the communication interface 404 , and the memory 406 communicate with each other via a communication bus 408 .

[0156] The communication interface 404 is used to communicate with other devices such as clients or other servers.

[0157] The processor 402 is used to execute the program 410, and specifically can execute the relevant steps in the above-mentioned embodiment of the method for evaluating the voltage strength of the power grid at the power receiving end.

[0158] Specifically, the program 410 may include program codes, which include computer operation instructions.

[0159] The processor 402 may be a central processing unit (CPU), or an application-specific integrated circuit (ASIC), or one or more integrated circuits configured to implement the embodiments of the present application. The one or more processors included in the computer device may be processors of the same type, such as one or more CPUs; or processors of different types, such as one or more CPUs and one or more ASICs.

[0160] The memory 406 is used to store the program 410. The memory 406 may include a high-speed RAM memory, and may also include a non-volatile memory (non-volatile memory), such as at least one disk memory.

[0161] The program 410 may be specifically configured to enable the processor 402 to perform the following operations:

[0162] In response to an evaluation instruction for a voltage strength of a power grid at a receiving end, a simulated jump voltage after a target DC inverter bus fault is cleared is obtained, wherein the power grid at the receiving end is a power grid at the receiving end fed with a new energy power system;

[0163] The voltage stiffness of the target DC inverter bus is calculated based on the simulated jump voltage, wherein the voltage stiffness is used to characterize the ratio between the jump voltage of the target DC inverter bus at the moment of recovery after the DC commutation failure occurs and the no-load voltage of the receiving-end power grid, and the jump voltage is obtained by subtracting the influence voltage of each other commutation failure DC inverter bus in the receiving-end power grid and the voltage drop caused by reactive power in the target DC inverter bus from the simulated jump voltage;

[0164] The voltage strength level of the power grid at the receiving end is determined according to the voltage stiffness.

[0165] The storage medium may also include an operating system and a network communication module. The operating system is a program that manages the hardware and software resources of the physical device of the above-mentioned method for evaluating the voltage strength of the power grid at the receiving end, and supports the operation of the information processing program and other software and / or programs. The network communication module is used to realize the communication between the components inside the storage medium, and the communication with other hardware and software in the information processing physical device.

[0166] Each embodiment in this specification is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the system embodiment, since it basically corresponds to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment.

[0167] The method and system of the present application may be implemented in many ways. For example, the method and system of the present application may be implemented by software, hardware, firmware, or any combination of software, hardware, and firmware. The above order of steps for the method is for illustration only, and the steps of the method of the present application are not limited to the order specifically described above, unless otherwise specifically stated. In addition, in some embodiments, the present application may also be implemented as a program recorded in a recording medium, which includes machine-readable instructions for implementing the method according to the present application. Therefore, the present application also covers a recording medium storing a program for executing the method according to the present application.

[0168] Obviously, those skilled in the art should understand that the above modules or steps of the present application can be implemented by a general computing device, they can be concentrated on a single computing device, or distributed on a network composed of multiple computing devices, and optionally, they can be implemented by a program code executable by a computing device, so that they can be stored in a storage device and executed by the computing device, and in some cases, the steps shown or described can be executed in a different order from that herein, or they can be made into individual integrated circuit modules, or multiple modules or steps therein can be made into a single integrated circuit module for implementation. Thus, the present application is not limited to any specific combination of hardware and software.

[0169] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for evaluating the voltage strength of a power grid at a receiving end, characterized in that: include: In response to an evaluation instruction for a voltage strength of a power grid at a receiving end, a simulated jump voltage after a target DC inverter bus fault is cleared is obtained, wherein the power grid at the receiving end is a power grid at the receiving end fed with a new energy power system; The voltage stiffness of the target DC inverter bus is calculated based on the simulated jump voltage, wherein the voltage stiffness is used to characterize the ratio between the jump voltage of the target DC inverter bus at the moment of recovery after the DC commutation failure occurs and the no-load voltage of the receiving-end power grid, and the jump voltage is obtained by subtracting the influence voltage of each other commutation failure DC inverter bus in the receiving-end power grid and the voltage drop caused by reactive power in the target DC inverter bus from the simulated jump voltage; Determining the voltage strength level of the receiving-end power grid according to the voltage stiffness; The calculating the voltage stiffness of the target DC inverter bus based on the simulated jump voltage includes: Based on the following formula, the sum of the influence voltages of the other commutation failure DC inverter buses in the receiving-end power grid is subtracted from the simulated jump voltage to obtain the jump voltage of the target DC inverter bus after removing the influence of multiple commutation failure DCs. Among them, U L It represents the jump voltage after removing the influence of multiple commutation failure DC, U0 represents the simulated jump voltage, n represents the number of commutation failure DC inverter busbars, VRPS i It represents the voltage reactive power sensitivity index of the ith commutation failure DC inverter bus, Q aci represents the rated reactive power of the i-th DC line; The voltage drop caused by reactive power in the target DC inverter bus is subtracted from the jump voltage after removing the impact of multiple commutation failure DC to obtain the jump voltage of the target DC inverter bus at the moment of recovery after the DC commutation failure occurs, wherein the voltage drop is calculated based on the following formula: Where dU represents the voltage drop, X sys Represents the reactance parameter of the power grid impedance at the receiving end, Q acN Indicates the rated reactive power that the target DC inverter bus needs to absorb from the receiving-end grid when connected to the receiving-end grid, U L It indicates the jump voltage after removing the DC influence of multi-phase commutation failure; The step of obtaining a simulated jump voltage after the target DC inverter bus fault is cleared includes: In the simulation software for the receiving-end power grid, it is set that the DC inverter busbar where the commutation failure occurs does not resume commutation after the fault is cleared, and the fault parameters are set according to business requirements; A simulation operation is performed on the power receiving end power grid, and a simulated jump voltage after the target DC inverter bus fault is cleared is recorded.

2. The method according to claim 1, characterized in that Before obtaining the jump voltage of the target DC inverter bus after removing the influence of multiple commutation failure DC by subtracting the sum of the influence voltages of other commutation failure DC inverter buses in the receiving-end power grid from the simulated jump voltage, the method further includes: Based on the following formula, the voltage reactive power sensitivity index of each of the other commutation failure DC inverter buses is calculated respectively: Among them, VRPS i represents the voltage reactive power sensitivity index of the i-th commutation failure DC inverter bus, ΔU represents the voltage change value of the target DC inverter bus, ΔQ i It represents the reactive power change value of the i-th other commutation failed DC inverter bus.

3. The method according to claim 1, characterized in that The step of determining the voltage strength level of the power grid at the receiving end according to the voltage stiffness comprises: If the voltage stiffness is less than a preset voltage stiffness threshold, it is determined that the voltage strength level of the receiving-end power grid is a low level, and a prompt message prohibiting direct current from being connected to the receiving-end power grid is output; If the voltage stiffness is greater than the preset voltage stiffness threshold, it is determined that the voltage strength level of the receiving-end power grid is a high level, and a DC access operation is performed to connect the DC to the receiving-end power grid based on the target DC inverter bus.

4. The method according to claim 3, characterized in that If the voltage stiffness is less than the preset voltage stiffness threshold, it is determined that the voltage strength level of the receiving-end power grid is a low level, and a prompt message prohibiting direct current from being connected to the receiving-end power grid is output, and the method further includes: A preset number of phase regulators are added to the receiving-end power grid, and reactive power is output when a commutation failure occurs in the target DC inverter bus.

5. A device for evaluating the voltage strength of a power grid at a receiving end, characterized in that: include: A simulated jump voltage acquisition module is used to obtain a simulated jump voltage after the target DC inverter bus fault is cleared in response to an evaluation instruction for the voltage strength of the receiving-end power grid, wherein the receiving-end power grid is a receiving-end power grid fed by a new energy power system; A voltage stiffness calculation module, used for calculating the voltage stiffness of the target DC inverter bus based on the simulated jump voltage, wherein the voltage stiffness is used to characterize the ratio between the jump voltage of the target DC inverter bus at the moment of recovery after a DC commutation failure occurs and the no-load voltage of the receiving-end power grid, and the jump voltage is obtained by subtracting the influence voltage of each other commutation failure DC inverter bus in the receiving-end power grid and the voltage drop caused by reactive power in the target DC inverter bus from the simulated jump voltage; A voltage strength level determination module, used to determine the voltage strength level of the receiving-end power grid according to the voltage stiffness; The voltage stiffness calculation module is used for: Based on the following formula, the sum of the influence voltages of the other commutation failure DC inverter buses in the receiving-end power grid is subtracted from the simulated jump voltage to obtain the jump voltage of the target DC inverter bus after removing the influence of multiple commutation failure DCs. Among them, U L It represents the jump voltage after removing the influence of multiple commutation failure DC, U0 represents the simulated jump voltage, n represents the number of commutation failure DC inverter busbars, VRPS i It represents the voltage reactive power sensitivity index of the ith commutation failure DC inverter bus, Q aci represents the rated reactive power of the i-th DC line; The voltage drop caused by reactive power in the target DC inverter bus is subtracted from the jump voltage after removing the impact of multiple commutation failure DC to obtain the jump voltage of the target DC inverter bus at the moment of recovery after the DC commutation failure occurs, wherein the voltage drop is calculated based on the following formula: Where dU represents the voltage drop, X sys Represents the reactance parameter of the power grid impedance at the receiving end, Q acN Indicates the rated reactive power that the target DC inverter bus needs to absorb from the receiving-end grid when connected to the receiving-end grid, U L It indicates the jump voltage after removing the DC influence of multi-phase commutation failure; The simulated jump voltage acquisition module is used for: In the simulation software for the receiving-end power grid, it is set that the DC inverter busbar where the commutation failure occurs does not resume commutation after the fault is cleared, and the fault parameters are set according to business requirements; A simulation operation is performed on the power receiving end power grid, and a simulated jump voltage after the target DC inverter bus fault is cleared is recorded.

6. A storage medium, wherein at least one executable instruction is stored in the storage medium, characterized in that: The executable instructions enable the processor to execute operations corresponding to the method for evaluating the voltage strength of the power grid at the receiving end according to any one of claims 1 to 4.

7. A terminal, comprising: A processor, a memory, a communication interface and a communication bus, wherein the processor, the memory and the communication interface communicate with each other via the communication bus; The memory is used to store at least one executable instruction, wherein the executable instruction enables the processor to perform operations corresponding to the method for evaluating the voltage strength of the receiving-end power grid according to any one of claims 1-4.

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