New energy field group fault transient equivalent modeling method and device

Abstract

The invention relates to a fault transient equivalent modeling method and device for a new energy field group, and the method comprises the steps: considering the influence of voltage drop detection, analyzing a fault current transient trajectory of a unit in a control mode that a current limiting link acts or does not act, and carrying out the primary grouping according to the control mode adopted in a transient stage of the unit; on the basis of the grouping result of the primary grouping, judging whether secondary grouping is needed or not by calculating the number proportion of the units acted by the current limiting link; if secondary grouping needs to be carried out, carrying out secondary grouping on the cluster acted by the current limiting link according to the current limiting depth on the basis of the primary grouping result to obtain a final grouping result; according to the grouping index provided by the invention, the influence of voltage drop detection on the fault characteristics of the unit can be considered, the transient trajectory of the short-circuit current of the unit can be reflected more accurately and specifically, and the effectiveness and accuracy of a grouping equivalence scheme under different fault working conditions are ensured through primary grouping and secondary grouping by using the grouping index.

Description

Technical Field

[0001] The present application relates to the technical field of equivalent modeling of faults in new energy plant groups, and in particular to a method and device for transient equivalent modeling of faults in new energy plant groups. Background Art

[0002] With the advancement of the dual carbon goals, traditional relay protection measures cannot operate accurately due to the significant differences in the fault characteristics of inverter-type renewable energy power sources and traditional synchronous motors, and the safety and stability of the power system are greatly affected. It is urgent to use the fault characteristics of renewable energy clusters to study new relay protection principles; however, due to the large number of units in the renewable energy clusters, the data processing and calculation workload required to use simulation software to model and simulate the detailed model of the renewable energy clusters is very large, and even difficult to solve. Therefore, it is necessary to establish an equivalent model of the renewable energy cluster to simulate the output characteristics of the renewable energy cluster under different fault conditions.

[0003] However, in the existing research on equivalent modeling of new energy field groups, the research on the transient process of unit fault current often ignores the control delay process caused by voltage detection. It is believed that the unit immediately switches to the inverter current limiting state or the inverter non-current limiting state after the fault is determined. As a result, the grouping indicators selected for fault transients cannot accurately and comprehensively reflect the transient trajectory of the unit fault current, and cannot guarantee the effectiveness and accuracy of the grouping equivalent scheme under different fault conditions. Summary of the invention

[0004] In order to overcome the above-mentioned deficiencies of the prior art, the present application provides a method and device for modeling transient equivalent faults of a new energy field group, which specifically adopts the following technical solutions:

[0005] A method for modeling transient equivalent values ​​of faults in a new energy field group, the method comprising the following steps:

[0006] Taking into account the influence of voltage drop detection on the transient characteristics of each unit in the renewable energy cluster, a low voltage ride-through control mode of each unit in the renewable energy cluster is obtained; wherein the low voltage ride-through control mode at least includes a control mode in which the current limiting link of the inverter of the unit is not effective and a control mode in which the current limiting link of the inverter of the unit is effective;

[0007] Perform the first grouping of the new energy field group according to the control mode of the unit in the transient stage, and obtain the primary grouping result;

[0008] According to the results of the primary grouping, calculate the proportion of units that function as current limiting links within the renewable energy cluster;

[0009] Determine whether to perform secondary grouping based on the number percentage results: when secondary grouping is not required, the primary grouping result is used as the target grouping result; when secondary grouping is required, calculate the current limiting depth of the units in the current limiting link of the new energy field group, and perform secondary grouping based on the primary grouping result according to the current limiting depth, and use the secondary grouping result as the target grouping result;

[0010] Based on the target grouping results, the units that are grouped into the same group after grouping are evaluated individually to obtain the multi-machine equivalent modeling results of the new energy field group;

[0011] According to the target grouping results, a multi-machine equivalent model is built after the single-machine equivalent of each unit in the same group is obtained to obtain the multi-machine equivalent modeling results of the new energy field group.

[0012] Optional: When considering the impact of voltage drop detection on the transient characteristics of each unit in the renewable energy field group, a linear function is used to fit the transient process of the voltage drop detection amplitude, where the d and q axis current reference values ​​output by each unit are:

[0013]

[0014] Where P 0 is the initial output power of the unit before failure; U is the voltage drop detection amplitude; i dref is the d-axis current reference value of the unit during low voltage ride-through, where i p is the d-axis current reference value when the unit current limiting link is not working, i m is the d-axis current reference value when the unit current limiting link is in effect, i dref for i p and i m The smaller value between qref is the q-axis current reference value of the unit during low voltage ride-through, I max The maximum current value allowed to pass through the inverter;

[0015] When each unit enters the low voltage ride-through mode, only the current inner loop control is retained. At this time, the transient trajectory of the output current reference value of each unit is used as the transient trajectory of the short-circuit current of each unit.

[0016] Optional: When the influence of voltage drop detection on the transient characteristics of each unit in the new energy field group is taken into account, the low voltage ride-through control mode includes a control mode in which the current limiting link of the unit inverter is not effective and a control mode in which the current limiting link of the unit inverter is effective;

[0017] When the current limiting link of the unit in the new energy field group does not work, the current transient characteristics of the unit in the corresponding control mode are:

[0018] When the unit terminal voltage drops to a level higher than the critical voltage, the voltage drop detection amplitude is calculated byp During the fault transient process, it is always less than i m , the inverter output current amplitude never reaches the maximum current value I max ; At this time, the unit current limiting link does not work, and according to i p The transient analytical formula outputs the d-axis current, where the d-axis current magnitude shows an increasing trend with the random terminal voltage drop;

[0019] When the current limiting link of the unit in the new energy field group works, the current transient characteristics of the unit under the corresponding control mode are:

[0020] When the unit terminal voltage drops to a level equal to or lower than the critical voltage, the voltage drop detection amplitude is calculated by p At the fault initiation stage, it is less than i m , and the subsequent voltage drop detection amplitude continues to drop i p Rise and Beyond m The inverter output current is subject to the maximum current value I max Limit; at this time, the unit will be in the fault initial stage according to i p The transient analytical formula outputs the d-axis current, where the d-axis current magnitude increases with the random terminal voltage drop until i p Rise and Beyond m ; Then the unit current limiting link works, at this time according to i m The transient analytical formula outputs the d-axis current, where the d-axis current shows a downward trend as the random terminal voltage drops.

[0021] Optionally: the type of low voltage ride-through control mode adopted by the unit is judged based on the value of the d-axis current reference value in the new energy field group, wherein the judgment process includes:

[0022] List the d-axis current reference value i of each unit in the renewable energy field group when the current limiting link does not work during the transient fault process p Analytical formula, d-axis current reference value i when the current limiting link is in effect m Analytical formula, obtain the initial output power P of the unit before failure 0 ;

[0023] Based on the initial output power of the unit before the fault and the analytical formula of the d-axis current reference value when the current limiting link is in effect and not in effect during the fault transient process of each unit, the terminal voltage that satisfies the d-axis current reference value when the current limiting link is in effect and not in effect is calculated;

[0024] The calculated terminal voltage is used as the critical voltage for determining the control mode of the corresponding unit, and it is determined whether the terminal voltage of the unit drops to the critical voltage. The type of low voltage ride-through control mode adopted by the unit is determined based on the judgment result.

[0025] Optional: When the unit terminal voltage does not drop to the critical voltage, the i calculated by the voltage drop detection amplitude p with i m The transient trajectory of the fault transient process does not have an intersection point, and the unit current limiting link does not work at this time; when the unit terminal voltage drops to the critical voltage or the terminal voltage drops below the critical voltage, the i calculated by the voltage drop detection amplitude p with i m The transient trajectory of the fault has an intersection point in the transient process, at which time the unit current limiting link comes into play.

[0026] The units with and without current limiting links are divided into two groups respectively, and the primary grouping result of the new energy field group is obtained.

[0027] Optional: The step of calculating the proportion of the number of units in the current limiting link in the new energy field group is:

[0028] W=n x / n;

[0029] Where W is the proportion of units with current limiting function in the new energy cluster; n x is the number of units in the current limiting link within the renewable energy cluster; n is the number of all units in the renewable energy cluster.

[0030] Optional: When judging whether to perform secondary grouping based on the number percentage result, first determine whether the number percentage of units with current limiting links in the new energy field group is greater than the threshold:

[0031] When the proportion of units affected by the current limiting link is greater than the threshold, the units affected by the current limiting link in the primary grouping result are grouped twice;

[0032] When the proportion of units affected by the current limiting link is less than or equal to the threshold, the primary grouping result is not subjected to secondary grouping, and the primary grouping result is the target grouping result.

[0033] Optionally: the step of calculating the unit current limiting depth of the current limiting link in the new energy field group includes:

[0034] Get the initial output power P of each unit before the fault 0 And the critical voltage u x ;

[0035] Based on the initial output power P of the unit before failure 0 And the critical voltage u x Calculate the change of d-axis current in the current limiting stage and the change of d-axis current in the non-current limiting stage of the unit with the current limiting link respectively;

[0036] Calculate the ratio of the change in d-axis current of the unit with the current limiting link in the current limiting stage to the change in d-axis current in the non-current limiting stage, and use the obtained ratio as the current limiting depth.

[0037] Optional: The calculation formula for the change in d-axis current of the unit with current limiting link in the current limiting stage is:

[0038]

[0039] The calculation formula for the change in d-axis current of the unit with current limiting link in the non-current limiting stage is:

[0040]

[0041] The calculation formula of the current limiting depth is:

[0042]

[0043] Where ΔI 2 ΔI is the change in the d-axis current of the unit during the current limiting stage; 1 is the change in d-axis current of the unit in the unlimited current stage; P 0 is the initial output power of the unit before failure; u x is the critical voltage; I max It is the maximum current value allowed to pass through the inverter.

[0044] In addition, the present application also discloses a new energy field group fault transient equivalent modeling device, the device comprising:

[0045] A control mode acquisition module is used to take into account the impact of voltage drop detection on the transient characteristics of each unit in the new energy field group, and obtain the low voltage ride-through control mode type of each unit in the new energy field group; wherein the low voltage ride-through control mode type at least includes a control mode in which the current limiting link of the unit inverter is not effective and a control mode in which the current limiting link of the unit inverter is effective;

[0046] The primary grouping module is used to perform the first grouping of the new energy plant group according to the control mode of the unit in the transient stage and obtain the primary grouping result;

[0047] The unit ratio calculation module is used to calculate the number ratio of units that are affected by the current limiting link in the new energy field group according to the primary grouping result;

[0048] The secondary grouping module of the field group is used to determine whether to perform secondary grouping according to the result of the number ratio: when secondary grouping is not required, the primary grouping result is used as the target grouping result; when secondary grouping is required, the current limiting depth of the units in the current limiting link of the new energy field group is calculated, and secondary grouping is performed on the basis of the primary grouping result according to the current limiting depth, and the secondary grouping result is used as the target grouping result;

[0049] The equivalent modeling module of the same group of units is used to perform single-unit equivalent modeling on the units that are grouped into the same group after grouping based on the target grouping results, and obtain the multi-unit equivalent modeling results of the new energy field group;

[0050] The equivalent model output module is used to build a multi-machine equivalent model according to the multi-machine equivalent of each unit in the same group in the target grouping result to obtain the multi-machine equivalent modeling result of the new energy field group.

[0051] Beneficial Effects

[0052] The technical solution of this application has the following beneficial effects:

[0053] (1) The transient equivalent modeling method of the new energy field group fault of the present application can take into account the impact of voltage drop detection on the transient trajectory of the unit fault current, more accurately and specifically reflect the transient trajectory of the unit short-circuit current, and propose grouping indicators based on the transient trajectory of the d-axis current of the unit under different control modes. The effectiveness of the grouping equivalent scheme of the unit under different fault conditions is guaranteed through two groupings, thereby improving the accuracy of the field group grouping results.

[0054] (2) The transient equivalent modeling method of the new energy field group fault of the present application adopts a secondary grouping method, that is, on the basis of the primary grouping result, the proportion of the number of units affected by the current limiting link is calculated to determine whether secondary grouping is needed, and the current limiting depth is used as the grouping indicator of the secondary grouping; this method takes into account the influence of the voltage drop detection link on the specific current limiting degree of the units affected by the current limiting link, and also ensures the equivalent accuracy of the equivalent model under different fault conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 This is a flow chart of the transient equivalent modeling method of the new energy field group fault in the embodiment of the present application.

[0056] Figure 2 This is the voltage drop trajectory diagram of the inverter-type new energy unit.

[0057] Figure 3 This is a transient trajectory diagram of the d-axis current reference value when the current limiting link of the unit is in effect and not in effect in the embodiment of the present application.

[0058] Figure 4 This is a transient trajectory diagram of the d-axis current of the unit when the current limiting link does not act in the embodiment of the present application.

[0059] Figure 5 This is a transient trajectory diagram of the d-axis current reference value when the current limiting link of the current limiting link action unit in the embodiment of the present application is in effect and not in effect.

[0060] Figure 6This is the transient trajectory diagram of the d-axis current of the unit affected by the current limiting link in the embodiment of the present application.

[0061] Figure 7 This is the transient trajectory diagram of the d-axis short-circuit current of the detailed model and the equivalent model of the photovoltaic power station in the embodiment of the present application.

[0062] Figure 8 This is the transient trajectory diagram of the q-axis short-circuit current of the detailed model and the equivalent model of the photovoltaic power station in the embodiment of the present application.

[0063] Fig. 9 This is the structural diagram of the new energy field group fault transient equivalent modeling device in the embodiment of the present application.

[0064] Fig.10 This is the structural diagram of an electronic device in the embodiment of the present application. Specific embodiments

[0065] The present application will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present application and cannot be used to limit the protection scope of the present application. It should be noted that the following detailed descriptions are all exemplary and are intended to provide further explanations for the present application.

[0066] Combined with Figure 1 As shown, the embodiment of the present application discloses a new energy field group fault transient equivalent modeling method, and the method includes the following steps:

[0067] Step S1: Considering the influence of voltage dip detection on the transient characteristics of each unit in the new energy field group, obtaining the low voltage ride-through control mode of each unit in the new energy field group; wherein the low voltage ride-through control mode at least includes a control mode in which the current limiting link of the unit inverter does not act and a control mode in which the current limiting link of the unit inverter acts;

[0068] Specifically, in this step S1, when considering the influence of voltage dip detection on the transient characteristics of each unit in the new energy field group, due to the existence of the voltage dip detection link, as Figure 2 shown, there is a delay in the switching of the low voltage ride-through control of the unit; since the existing grouped equivalent schemes often ignore the control delay process caused by voltage detection in the study of the transient process of the fault current, it is considered that the unit immediately switches to the current limiting state or the non-current limiting state after the fault is determined, resulting in the grouped index selected for the fault transient not being able to accurately and comprehensively reflect the transient trajectory of the fault current of the unit. And the embodiment of the present application considers that the voltage dip amplitude detection link in the low voltage ride-through control stage will cause a transient process in the voltage dip amplitude detected by the system. Therefore, a linear function is used to fit the transient process of the voltage dip detection amplitude, and the d-axis and q-axis current reference values output by each unit are:

[0069]

[0070] Where P 0 is the initial output power of the unit before failure; U is the voltage drop detection amplitude; i dref is the d-axis current reference value of the unit during low voltage ride-through, where i p is the d-axis current reference value when the unit current limiting link is not working, i m is the d-axis current reference value when the unit current limiting link is in effect, i dref for i p and i m The smaller value between qref is the q-axis current reference value of the unit during low voltage ride-through, I max The maximum current value allowed to pass through the inverter;

[0071] When each unit enters the low voltage ride-through mode, only the current inner loop control is retained. At this time, the transient trajectory of the output current reference value of each unit is used as the transient trajectory of the short-circuit current of each unit.

[0072] Furthermore, since the impedance of the collector lines connected to the common connection point (PCC) of each unit in the new energy field group is different, the terminal voltage drop value of each unit after the fault is also different. The difference in the degree of terminal voltage drop will cause the unit to adopt different low voltage ride-through control modes. The low voltage ride-through control mode described in this embodiment includes two types of control modes: a control mode in which the inverter current limiting link of the unit does not work and a control mode in which the inverter current limiting link of the unit works. When taking into account the impact of voltage drop detection on the transient characteristics of each unit in the new energy field group, units with different terminal voltage drop degrees adopt different low voltage ride-through control modes, and their corresponding current transient characteristics are different.

[0073] (1) When the current limiting link of the unit in the new energy field group does not work, the current transient characteristics of the unit in the corresponding control mode are:

[0074] When the unit terminal voltage drops to a level higher than the critical voltage, the voltage drop detection amplitude is calculated by p During the fault transient process, it is always less than i m ,like Figure 3 As shown in Figure 2, the inverter output current amplitude has never reached the maximum current value I allowed to pass. max ; At this time, the unit current limiting link does not work, and according to i p The transient analytical formula outputs the d-axis current, where the d-axis current magnitude shows an upward trend as the terminal voltage drops randomly. The transient trajectory of the d-axis current is as follows: Figure 4 As shown;

[0075] (2) When the current limiting link of the unit in the new energy field group is in effect, the current transient characteristics of the unit under the corresponding control mode are:

[0076] When the unit terminal voltage drops to a level equal to or lower than the critical voltage, the voltage drop detection amplitude is calculated by p At the fault initiation stage, it is less than i m , and the subsequent voltage drop detection amplitude continues to drop i p Rise and Beyond m ,like Figure 5 As shown, the inverter output current is subject to the maximum current value I max Limit; at this time, the unit will be in the fault initial stage according to i p The transient analytical formula outputs the d-axis current, where the d-axis current magnitude increases with the random terminal voltage drop until i p Rise and Beyond m ; Then the unit current limiting link works, at this time according to i m The transient analytical formula outputs the d-axis current, where the d-axis current magnitude shows a decreasing trend as the terminal voltage drops randomly. The transient trajectory of the d-axis current is as follows: Figure 6 shown.

[0077] Furthermore, the two low voltage ride-through control modes adopted in the embodiments of the present application have the following characteristics: i of the unit where the current limiting link does not work p During the fault transient process, it is always less than i m Therefore, there is no i in the fault transient process. p =i m Intersection point; i of the unit with current limiting link p At the beginning of the fault, it is less than i m , and then the voltage detection value continues to drop p Rise and Beyond m , so there is i in the fault transient process p =i m The intersection of .

[0078] Based on the above characteristics, the type of low voltage ride-through control mode adopted by the unit is judged based on the value of the d-axis current reference value in the new energy field group described in the embodiment of the present application, wherein the judgment process includes:

[0079] List the d-axis current reference value i of each unit in the renewable energy field group when the current limiting link does not work during the transient fault process p Analytical formula, d-axis current reference value i when the current limiting link is in effect m Analytical formula, obtain the initial output power P of the unit before failure 0 ;

[0080] Based on the initial output power of the unit before the fault and the analytical formula of the d-axis current reference value when the current limiting link is working and not working in the transient process of the fault, the terminal voltage that satisfies the d-axis current reference value when the current limiting link is working and not working is calculated; according to formula ip =i m The specific expression of can be obtained as formula:

[0081]

[0082] According to the above formula, the input power P of the unit can be used 0 It can be calculated to satisfy i p =i m The terminal voltage of the machine.

[0083] The calculated terminal voltage is used as the critical voltage u for determining the corresponding unit control mode. x , and judge whether the unit terminal voltage drops to the critical voltage, and determine the type of low voltage ride-through control mode adopted by the unit according to the judgment result:

[0084] Specifically, when the unit terminal voltage does not drop to the critical voltage, the i calculated by the voltage drop detection amplitude p with i m The transient trajectory of the fault transient process does not have an intersection point, and the unit current limiting link does not work at this time; when the unit terminal voltage drops to the critical voltage or the terminal voltage drops below the critical voltage, the i calculated by the voltage drop detection amplitude p with i m The transient trajectory of the fault has an intersection point in the transient process, at which time the unit current limiting link comes into play.

[0085] Step S2: Divide the control mode of each unit in the transient stage according to the low voltage ride-through control mode type to obtain a primary grouping result; since there is a large difference in the transient trajectories of the d-axis short-circuit current of the units adopting the two control modes, the units adopting different control modes are divided into two groups. This process is the primary grouping of the field group.

[0086] It should be noted that the present application can divide the field group into two groups according to the results of the primary grouping. Since the grouping results of the primary grouping of the field group are affected by the degree of system fault, when the degree of system fault is deep or shallow, most of the units in the field group will be in the same control mode and will be divided into the same group after the primary grouping. The grouping effect of the primary grouping is seriously reduced or even ineffective. Furthermore, the present application proposes a secondary grouping method, that is, based on the results of the primary grouping, it is determined whether secondary grouping is needed by calculating the proportion of the number of units affected by the current limiting link, and the "current limiting depth" is used as the grouping indicator for the secondary grouping.

[0087] Step S3: According to the primary grouping result, the proportion of the number of units in the new energy field group that are affected by the current limiting link is calculated; wherein the step of calculating the proportion of the number of units in the new energy field group that are affected by the current limiting link is as follows:

[0088] W=nx / n;

[0089] Where W is the proportion of units with current limiting function in the new energy cluster; n x is the number of units in the current limiting link within the renewable energy cluster; n is the number of all units in the renewable energy cluster.

[0090] Step S4: Determine whether to perform secondary grouping according to the number proportion result: when secondary grouping is not required, the primary grouping result is used as the target grouping result; when secondary grouping is required, the current limiting depth of the units in the current limiting link of the new energy field group is calculated, and the primary grouping result is secondary grouped according to the current limiting depth, and the secondary grouping result is used as the target grouping result;

[0091] Specifically, in step S4, after performing a grouping, two groups are obtained according to the grouping control mode; if the difference in the number of units in the two groups is not large, the equivalent effect after grouping is good, and the result of the grouping is the final grouping result; if the difference in the number of units in the two groups is large, the following two situations will occur:

[0092] (1) When the system fault is relatively minor, the terminal voltage drop of each unit in the field group is relatively shallow, the current limiting links of most units are not effective, and the transient trajectories of the unit D-axis current are not much different, so there is no need for secondary grouping.

[0093] (2) When the system fault is serious, the terminal voltage drop of each unit in the field group is deep, the current limiting links of most units are activated, and the transient trajectories of the unit d-axis current are quite different, so secondary grouping is required.

[0094] Furthermore, when the present application determines whether to perform secondary grouping according to the number ratio result, it first determines whether the number ratio of the units with current limiting links in the new energy field group is greater than the threshold:

[0095] When the proportion of units affected by the current limiting link is greater than the threshold, the units affected by the current limiting link in the primary grouping result are grouped twice;

[0096] When the number of units affected by the current limiting link accounts for less than or equal to the threshold, the primary grouping result is not subjected to secondary grouping, and the primary grouping result is the target grouping result.

[0097] More specifically, the grouping index of the secondary grouping in this application takes into account the impact of the voltage drop detection link on the units affected by the current limiting link, and also ensures the equivalent accuracy of the equivalent model under different fault conditions. When the field group needs to be grouped twice, the current limiting depth of the units affected by the current limiting link is calculated as the grouping index of the secondary grouping, and the secondary grouping is performed on the basis of the primary grouping result to obtain the final grouping result. The steps for calculating the current limiting depth of the units affected by the current limiting link in the new energy field group include:

[0098] Get the initial output power P of each unit before the fault 0 And the critical voltage u x ;

[0099] Based on the initial output power P of the unit before failure 0 And the critical voltage u x Calculate the change of d-axis current in the current limiting stage and the change of d-axis current in the non-current limiting stage of the unit with the current limiting link:

[0100] (1) The calculation formula for the change in d-axis current of a unit with a current limiting link during the current limiting stage is:

[0101]

[0102] (2) The calculation formula for the change in d-axis current of the unit with current limiting function in the non-current limiting stage is:

[0103]

[0104] Calculate the ratio of the change in the d-axis current of the unit in the current limiting stage to the change in the d-axis current of the unit in the non-current limiting stage, and use the obtained ratio as the current limiting depth:

[0105] The calculation formula of the current limiting depth is:

[0106]

[0107] Where ΔI 2 ΔI is the change in the d-axis current of the unit during the current limiting stage; 1 is the change in d-axis current of the unit in the unlimited current stage; P 0 is the initial output power of the unit before failure; u x is the critical voltage; I max It is the maximum current value allowed to pass through the inverter.

[0108] Step S5: Based on the target grouping result, the units divided into the same group are respectively modeled as single units, and a multi-unit equivalent model is obtained after the single unit equivalent of the units in the same group is obtained;

[0109] Step S6: construct a multi-machine equivalent model based on the single-machine equivalent of each unit in the same group in the target grouping result to obtain the multi-machine equivalent modeling result of the new energy field group.

[0110] In addition, in order to verify the feasibility of the application method, a detailed model of the photovoltaic power station is built based on the PSCAD simulation platform, and according to the above implementation steps, a transient equivalent model of the photovoltaic station fault taking into account the influence of voltage drop detection is built. The transient trajectory of the d and q axis fault currents output by the detailed model of the photovoltaic station and the d and q axis fault currents output by the equivalent model are shown in the figure. Figure 7 , Figure 8 shown; based on Figure 7 and Figure 8 The results shown show that the transient trajectory of the fault current of the photovoltaic station equivalent model can better fit the transient trajectory of the fault current of the photovoltaic station detailed model, which verifies the effectiveness of the transient equivalent modeling method of the inverter-type new energy field group fault that takes into account the influence of voltage drop detection proposed in this application. In summary, the grouping index used in the transient equivalent modeling method of the new energy field group fault proposed in this application can take into account the influence of voltage drop detection on the fault characteristics of the unit, and more accurately and specifically reflect the transient trajectory of the short-circuit current of the unit, and use the grouping index to ensure the effectiveness and accuracy of the grouping equivalent scheme under different fault conditions through primary grouping and secondary grouping.

[0111] like Fig. 9 As shown, in addition, the present application also discloses a new energy field group fault transient equivalent modeling device, the device comprising:

[0112] A control mode acquisition module is used to take into account the impact of voltage drop detection on the transient characteristics of each unit in the new energy field group, and obtain the low voltage ride-through control mode type of each unit in the new energy field group; wherein the low voltage ride-through control mode type at least includes a control mode in which the current limiting link of the unit inverter is not effective and a control mode in which the current limiting link of the unit inverter is effective;

[0113] The primary grouping module is used to perform the first grouping of the new energy plant group according to the control mode of the unit in the transient stage and obtain the primary grouping result;

[0114] The unit ratio calculation module is used to calculate the number ratio of units that are affected by the current limiting link in the new energy field group according to the primary grouping result;

[0115] The secondary grouping module of the field group is used to determine whether to perform secondary grouping according to the result of the number ratio: when secondary grouping is not required, the primary grouping result is used as the target grouping result; when secondary grouping is required, the current limiting depth of the units in the current limiting link of the new energy field group is calculated, and secondary grouping is performed on the basis of the primary grouping result according to the current limiting depth, and the secondary grouping result is used as the target grouping result;

[0116] The equivalent modeling module of the same group of units is used to perform single-unit equivalent modeling on the units that are grouped into the same group after grouping based on the target grouping results, and obtain the multi-unit equivalent modeling results of the new energy field group;

[0117] The equivalent model output module is used to build a multi-machine equivalent model according to the multi-machine equivalent of each unit in the same group in the target grouping result to obtain the multi-machine equivalent modeling result of the new energy field group.

[0118] The device provided in the embodiment of the present application can achieve Figure 1 To avoid repetition, the various processes implemented by the method embodiment will not be described again here.

[0119] like Fig.10 As shown, the embodiment of the present application also provides an electronic device, including a processor and a memory, a program or instruction stored in the memory and executable on the processor, and when the program or instruction is executed by the processor, the following is achieved: Figure 1 The various processes of the method embodiment shown in the figure can achieve the same technical effect. To avoid repetition, they will not be described again here.

[0120] The embodiment of the present application also provides a readable storage medium on which a program or instruction is stored. When the program or instruction is executed by a processor, the above Figure 1 The various processes of the method embodiments described above can achieve the same technical effect, and will not be described again here to avoid repetition.

[0121] The present application also provides a computer program product, including computer instructions, which, when executed by a processor, implement the above Figure 1 The various processes of the method embodiments described above can achieve the same technical effect, and will not be described again here to avoid repetition.

[0122] It should be understood that "one embodiment" or "an embodiment" mentioned throughout the specification means that specific features, structures or characteristics related to the embodiment are included in at least one embodiment of the present application. Therefore, "in one embodiment" or "in an embodiment" appearing throughout the specification does not necessarily refer to the same embodiment. In addition, these specific features, structures or characteristics can be combined in one or more embodiments in any suitable manner. It should be understood that in various embodiments of the present application, the size of the sequence number of the above-mentioned processes does not mean the order of execution, and the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application. The above-mentioned sequence numbers of the embodiments of the present application are only for description and do not represent the advantages and disadvantages of the embodiments.

[0123] It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element.

[0124] In the several embodiments provided in the present application, it should be understood that the disclosed devices and methods can be implemented in other ways. The device embodiments described above are only schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation, such as: multiple units or components can be combined, or can be integrated into another device, or some features can be ignored or not executed. In addition, the coupling, direct coupling, or communication connection between the components shown or discussed can be through some interfaces, and the indirect coupling or communication connection of the devices or units can be electrical, mechanical or other forms.

[0125] The units described above as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units; they may be located in one place or distributed on multiple network units; some or all of the units may be selected according to actual needs to achieve the purpose of the present embodiment.

[0126] In addition, all functional units in the embodiments of the present application may be integrated into one processing unit, or each unit may be a separate unit, or two or more units may be integrated into one unit; the above-mentioned integrated units may be implemented in the form of hardware or in the form of hardware plus software functional units.

[0127] A person skilled in the art can understand that all or part of the steps of implementing the above method embodiment can be completed by hardware related to program instructions, and the aforementioned program can be stored in a computer-readable storage medium. When the program is executed, it executes the steps of the above method embodiment; and the aforementioned storage medium includes: mobile storage devices, read-only memories (ROM), magnetic disks or optical disks, etc., various media that can store program codes.

[0128] Alternatively, if the above-mentioned integrated unit of the present application is implemented in the form of a software function module and sold or used as an independent product, it can also be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the embodiment of the present application can essentially or in other words, the part that contributes to the prior art can be embodied in the form of a software product, which is stored in a storage medium and includes several instructions for a device (which can be a terminal or a platform, etc.) to execute all or part of the methods described in each embodiment of the present application. The aforementioned storage medium includes: various media that can store program codes, such as mobile storage devices, ROMs, magnetic disks, or optical disks.

[0129] The above is only a preferred implementation of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present application. These improvements and modifications should also be regarded as the scope of protection of the present application.

Claims

1. A transient equivalent modeling method for faults in new energy fields, characterized in that: The method comprises the following steps: Taking into account the influence of voltage drop detection on the transient characteristics of each unit in the renewable energy cluster, the low voltage ride-through control mode type of each unit in the renewable energy cluster is obtained; wherein the low voltage ride-through control mode at least includes a control mode in which the inverter current limiting link of the unit is not effective and a control mode in which the inverter current limiting link of the unit is effective; Perform the first grouping of the new energy field group according to the control mode of the unit in the transient stage, and obtain the primary grouping result; According to the results of the primary grouping, calculate the proportion of units that function as current limiting links within the renewable energy cluster; Determine whether to perform secondary grouping based on the number percentage results: when secondary grouping is not required, the primary grouping result is used as the target grouping result; when secondary grouping is required, calculate the current limiting depth of the units in the current limiting link of the new energy field group, and perform secondary grouping based on the primary grouping result according to the current limiting depth, and use the secondary grouping result as the target grouping result; Based on the target grouping results, the units that are grouped into the same group after grouping are evaluated individually to obtain the multi-machine equivalent modeling results of the new energy field group; The multi-machine equivalent modeling results of the new energy field group are obtained based on the multi-machine equivalent modeling results after the single-machine equivalent of each unit in the same group in the target grouping results.

2. The transient equivalent modeling method of new energy field group fault according to claim 1 is characterized in that: When considering the impact of voltage drop detection on the transient characteristics of each unit in the renewable energy field group, a linear function is used to fit the transient process of the voltage drop detection amplitude, where the d and q axis current reference values ​​output by each unit are: Where P0 is the initial output power of the unit before failure; U is the voltage drop detection amplitude; i dref is the d-axis current reference value of the unit during low voltage ride-through, where i p is the d-axis current reference value when the unit current limiting link is not working, i m is the d-axis current reference value when the unit current limiting link is in effect, i dref for i p and i m The smaller value between qref is the q-axis current reference value of the unit during low voltage ride-through, I max The maximum current value allowed to pass through the inverter; When each unit enters the low voltage ride-through mode, only the current inner loop control is retained. At this time, the transient trajectory of the output current reference value of each unit is used as the transient trajectory of the short-circuit current of each unit.

3. The transient equivalent modeling method of new energy field group fault according to claim 2 is characterized in that: When the influence of voltage drop detection on the transient characteristics of each unit in the new energy field group is taken into account, the low voltage ride-through control mode includes a control mode in which the current limiting link of the unit inverter is not effective and a control mode in which the current limiting link of the unit inverter is effective; When the current limiting link of the unit in the new energy field group does not work, the current transient characteristics of the unit in the corresponding control mode are: When the unit terminal voltage drops to a level higher than the critical voltage, the voltage drop detection amplitude is calculated by p During the fault transient process, it is always less than i m , the inverter output current amplitude never reaches the maximum current value I max ; At this time, the unit current limiting link does not work, and according to i p The transient analytical formula outputs the d-axis current, where the d-axis current magnitude shows an increasing trend with the random terminal voltage drop; When the current limiting link of the unit in the new energy field group works, the current transient characteristics of the unit under the corresponding control mode are: When the unit terminal voltage drops to a level equal to or lower than the critical voltage, the voltage drop detection amplitude is calculated by p At the initial stage of the fault, it is less than i m , and the subsequent voltage drop detection amplitude continues to drop i p Rise and Beyond m The inverter output current is subject to the maximum current value I max Limit; at this time, the unit will be in the fault initial stage according to i p The transient analytical formula outputs the d-axis current, where the d-axis current magnitude increases with the random terminal voltage drop until i p Rise and Beyond m ; Then the unit current limiting link works, at this time according to i m The transient analytical formula outputs the d-axis current, where the d-axis current shows a downward trend as the random terminal voltage drops.

4. The transient equivalent modeling method of new energy field group fault according to claim 3 is characterized in that: The type of low voltage ride-through control mode adopted by the unit is judged based on the value of the d-axis current reference value in the new energy field group, wherein the judgment process includes: List the d-axis current reference value i of each unit in the renewable energy field group when the current limiting link does not work during the transient fault process p Analytical formula, d-axis current reference value i when the current limiting link is in effect m Analytical formula, obtain the initial output power P0 of the unit before failure; Based on the initial output power of the unit before the fault and the analytical formula of the d-axis current reference value when the current limiting link is in effect and not in effect during the fault transient process of each unit, the terminal voltage that satisfies the d-axis current reference value when the current limiting link is in effect and not in effect is calculated; The calculated terminal voltage is used as the critical voltage for determining the control mode of the corresponding unit, and it is determined whether the terminal voltage of the unit drops to the critical voltage. The type of low voltage ride-through control mode adopted by the unit is determined based on the judgment result.

5. The transient equivalent modeling method of new energy field group fault according to claim 4 is characterized in that: When the unit terminal voltage does not drop to the critical voltage, the i calculated by the voltage drop detection amplitude p with i m The transient trajectory of the fault transient process does not have an intersection point, and the unit current limiting link does not work at this time; when the unit terminal voltage drops to the critical voltage or the terminal voltage drops below the critical voltage, the i calculated by the voltage drop detection amplitude p with i m The transient trajectory of the fault has an intersection point in the transient process, at which time the unit current limiting link comes into play. The units with and without current limiting links are divided into two groups respectively, and the primary grouping result of the new energy field group is obtained.

6. The transient equivalent modeling method of new energy field group fault according to claim 1 is characterized in that: The steps for calculating the proportion of the number of units with current limiting links in the new energy field group are as follows: W=n x / n; Where W is the proportion of units with current limiting function in the new energy cluster; n x is the number of units in the current limiting link within the renewable energy cluster; n is the number of all units in the renewable energy cluster.

7. The transient equivalent modeling method of new energy field group fault according to claim 6 is characterized in that: When judging whether to perform secondary grouping based on the number percentage results, first determine whether the number of units with current limiting links in the new energy field group is greater than the threshold: When the proportion of units affected by the current limiting link is greater than the threshold, the units affected by the current limiting link in the primary grouping result are grouped twice; When the number of units affected by the current limiting link accounts for less than or equal to the threshold, the primary grouping result is not subjected to secondary grouping, and the primary grouping result is the target grouping result.

8. The transient equivalent modeling method of new energy field group fault according to claim 1 is characterized in that: The step of calculating the unit current limiting depth of the current limiting link in the new energy field group includes: Obtain the initial output power P0 and critical voltage u of each unit before the fault x ; Based on the initial output power P0 and critical voltage u before the unit fails x Calculate the change of d-axis current in the current limiting stage and the change of d-axis current in the non-current limiting stage of the unit with the current limiting link respectively; Calculate the ratio of the change in d-axis current of the unit with the current limiting link in the current limiting stage to the change in d-axis current in the non-current limiting stage, and use the obtained ratio as the current limiting depth.

9. The transient equivalent modeling method of new energy field group fault according to claim 8 is characterized in that: The calculation formula for the change in d-axis current of the unit with current limiting link in the current limiting stage is: The calculation formula for the change in d-axis current of the unit with current limiting link in the non-current limiting stage is: The calculation formula of the current limiting depth is: Where ΔI2 is the change in d-axis current of the unit in the current limiting stage; ΔI1 is the change in d-axis current of the unit in the non-current limiting stage; P0 is the initial output power of the unit before failure; u x is the critical voltage; I max It is the maximum current value allowed to pass through the inverter.

10. A transient equivalent modeling device for a new energy field group fault, characterized in that: The device comprises: A control mode acquisition module is used to take into account the impact of voltage drop detection on the transient characteristics of each unit in the new energy field group, and obtain the low voltage ride-through control mode type of each unit in the new energy field group; wherein the low voltage ride-through control mode type at least includes a control mode in which the current limiting link of the unit inverter is not effective and a control mode in which the current limiting link of the unit inverter is effective; The primary grouping module is used to perform the first grouping of the new energy plant group according to the control mode of the unit in the transient stage and obtain the primary grouping result; The unit ratio calculation module is used to calculate the number ratio of units that are affected by the current limiting link in the new energy field group according to the primary grouping result; The secondary grouping module of the field group is used to determine whether to perform secondary grouping according to the result of the number ratio: when secondary grouping is not required, the primary grouping result is used as the target grouping result; when secondary grouping is required, the current limiting depth of the units in the current limiting link of the new energy field group is calculated, and secondary grouping is performed on the basis of the primary grouping result according to the current limiting depth, and the secondary grouping result is used as the target grouping result; The equivalent modeling module of the same group of units is used to perform single-unit equivalent modeling on the units that are grouped into the same group after grouping based on the target grouping results, and obtain the multi-unit equivalent modeling results of the new energy field group; The equivalent model output module is used to obtain the multi-machine equivalent modeling results of the new energy field group based on the multi-machine equivalent modeling results after the single-machine equivalent of each unit in the same group in the target grouping results.

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