A new energy field group fault transient state equivalent modeling method and device

Abstract

The application relates to a new energy field group fault transient equivalent modeling method and device. The method considers the influence of voltage drop detection, analyzes the fault current transient trajectory of a unit under the control mode of a current limiting link action and the control mode of a current limiting link non-action, and carries out primary grouping according to the control mode adopted by the unit in the transient stage. Based on the grouping result of the primary grouping, whether secondary grouping needs to be carried out is judged by calculating the proportion of the number of the units under the action of the current limiting link; if the secondary grouping needs to be carried out, the units under the action of the current limiting link are secondarily grouped according to the current limiting depth on the basis of the primary grouping result, and the final grouping result is obtained. The grouping index proposed in the application can consider the influence of voltage drop detection on the fault characteristics of the unit, more accurately and specifically reflect the short-circuit current transient trajectory of the unit, and ensure the effectiveness and accuracy of the grouping equivalent scheme under different fault conditions by using the grouping index through primary grouping and secondary grouping.

Description

Technical Field

[0001] This application relates to the field of equivalent modeling technology for faults in new energy power grids, specifically to a method and apparatus for transient equivalent modeling of faults in new energy power grids. Background Technology

[0002] Because the fault characteristics of inverter-type renewable energy power sources differ significantly from those of traditional synchronous motors, traditional relay protection measures cannot operate accurately, which greatly affects the safety and stability of the power system. Therefore, it is urgent to study new relay protection principles using the fault characteristics of renewable energy power plant clusters. However, due to the large number of units in renewable energy power plant clusters, the data processing and calculation workload required to model and simulate detailed models of renewable energy power plant clusters using simulation software is enormous, and sometimes even difficult to solve. Therefore, it is necessary to establish an equivalent model of renewable energy power plant clusters to simulate the output characteristics of renewable energy power plant clusters under different fault conditions.

[0003] However, in existing studies on equivalent modeling of new energy power plants, the research on the transient process of unit fault current often ignores the control delay process caused by voltage detection. It assumes that the unit immediately switches to inverter current-limiting state or inverter current-unlimiting state after fault determination. As a result, the grouping index selected for fault transients cannot accurately and comprehensively reflect the transient trajectory of unit fault current, and cannot guarantee the effectiveness and accuracy of the grouping equivalent scheme under different fault conditions. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, this application provides a method and apparatus for transient equivalent modeling of faults in new energy power plant clusters, specifically adopting the following technical solution:

[0005] A transient equivalent modeling method for faults in a new energy power plant cluster, the method comprising the following steps:

[0006] Taking into account the impact of voltage drop detection on the transient characteristics of each unit in the new energy power plant cluster, the low voltage ride-through control mode of each unit in the new energy power plant cluster is obtained; wherein the low voltage ride-through control mode includes at least a control mode in which the inverter current limiting circuit of the unit does not work and a control mode in which the inverter current limiting circuit of the unit works.

[0007] The new energy power plant group was first grouped according to the control mode of the unit in the transient phase, and the first grouping result was obtained.

[0008] Based on the results of a single clustering, calculate the percentage of units within the new energy power plant cluster affected by current limiting mechanisms.

[0009] Whether to perform secondary grouping is determined based on the quantity ratio results: when secondary grouping is not required, the result of primary grouping is used as the target grouping result; when secondary grouping is required, the current limiting depth of the units affected by the current limiting link in the new energy field group is calculated, and secondary grouping is performed based on the result of primary grouping according to the current limiting depth, and the result of secondary grouping is used as the target grouping result.

[0010] Based on the target clustering results, single-unit equivalent modeling is performed on the units that are grouped into the same cluster after clustering, and multi-unit equivalent modeling results of new energy power plant clusters are obtained.

[0011] The multi-machine equivalent modeling results of the new energy power plant cluster are obtained by constructing multi-machine equivalent models after the single-machine equivalent of each unit in the target cluster results.

[0012] Optional: When considering the impact of voltage sag detection on the transient characteristics of each unit in the renewable energy power plant cluster, a linear function is used to fit the transient process of the voltage sag detection amplitude, where the reference values ​​for the d-axis and q-axis currents output by each unit are:

[0013] ;

[0014] in P 0 represents the initial output power before the unit malfunction; U This refers to the voltage drop detection amplitude. I dref For the unit during low voltage ride-through d shaft current reference value, where i p When the unit's current limiting circuit is not in operation d Shaft current reference value, i m When the current limiting circuit of the unit is in effect d Shaft current reference value, i dref for i p and i m The smaller of the two values; I qref For the unit during low voltage ride-through q Shaft current reference value, I max This is the maximum current value that the inverter is allowed to pass through;

[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 considering the impact of voltage drop detection on the transient characteristics of each unit in the new energy power plant cluster, the low voltage ride-through control mode includes a control mode in which the current limiting link of the unit inverter is not activated, and a control mode in which the current limiting link of the unit inverter is activated.

[0017] When the current limiting circuit of the generating units in the new energy power plant cluster is not in operation, the transient current characteristics of the units under the corresponding control mode are as follows:

[0018] When the voltage drop at the generator terminal exceeds the critical voltage, the voltage drop is calculated based on the voltage drop detection amplitude. i p It is always less than during the fault transient process. i m The inverter output current amplitude never reached the maximum allowable current value. I max At this time, the unit's current limiting circuit does not function, and according to i p Transient analytical output d shaft current, where d The magnitude of the shaft current shows an upward trend in random terminal voltage drops.

[0019] When the current limiting circuit of the generating units in the new energy power plant cluster is in effect, the transient current characteristics of the units under the corresponding control mode are as follows:

[0020] When the voltage drop at the generator terminal is equal to or lower than the critical voltage, the voltage drop is calculated based on the voltage drop detection amplitude. i p Less than the initial stage of the fault i m Subsequently, the detected amplitude continued to drop as the voltage decreased. i p Rise and surpass i m The inverter output current is limited by the maximum allowable current value. I max Limitations; at this time, the unit will, according to the initial stage of the fault... i p Transient analytical output d shaft current, where d The magnitude of the shaft current increases with the random drop in terminal voltage until... i p Rise and surpass i m Subsequently, the unit's current limiting mechanism takes effect, at which point, according to... i m Transient analytical output d shaft current, where d The magnitude of the shaft current decreases randomly with the drop in terminal voltage.

[0021] Optionally: The type of low-voltage ride-through control mode adopted by the generating unit in the new energy power plant cluster is determined based on the value of the d-axis current reference value, wherein the determination process includes:

[0022] List the situations where the current limiting circuits of each unit in the new energy power plant cluster are not functioning during the fault transient process. d Shaft current reference value i p Analytical expression 、 When the flow limiting mechanism is in effect d Shaft current reference value i m Analytical expression, obtaining the initial output power before unit failure. P 0;

[0023] Based on the initial output power of the unit before the fault and the current limiting links of each unit during the fault transient process, when they are active or inactive. d The analytical formula for the shaft current reference value is used to calculate the current limiting circuit under different conditions, whether it is active or not. d Terminal voltages with the same shaft current reference value;

[0024] The calculated terminal voltage is used as the critical voltage for determining the corresponding unit control mode. It is then determined whether the unit terminal voltage has dropped to the critical voltage. Based on the determination result, the type of low voltage ride-through control mode adopted by the unit is determined.

[0025] Optional: When the unit terminal voltage has not dropped to the critical voltage, the voltage drop detection amplitude is used for calculation. i p and i m The transient trajectories do not intersect during the fault transient process, at which point the unit's current limiting circuit does not function; when the unit's terminal voltage drops to or below the critical voltage, the current limiting circuit is calculated based on the voltage drop detection amplitude. i p and i m The transient trajectories intersect during the fault transient process, at which point the unit's current limiting circuit comes into effect;

[0026] The generating units with and without current-limiting mechanisms are divided into two groups, resulting in the first-order grouping of the new energy power plant cluster.

[0027] Optionally: The step of calculating the proportion of units affected by current limiting in the new energy power plant cluster is as follows:

[0028] ;

[0029] Where W represents the percentage of units in the new energy power plant cluster that are subject to current limiting. nx The number of generating units that act as current-limiting mechanisms within the new energy power plant cluster; n This refers to the total number of generating units within the new energy power plant cluster.

[0030] Optional: When determining whether to perform secondary grouping based on the quantity ratio results, first determine whether the quantity ratio of units subject to current limiting in the new energy power plant group is greater than the threshold:

[0031] When the proportion of units affected by the current limiting mechanism exceeds the threshold, the units affected by the current limiting mechanism in the first grouping result are grouped a second time.

[0032] When the proportion of units affected by the current limiting mechanism 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 affected by the current limiting link within the new energy power plant group includes:

[0034] Obtain the initial output power of each unit before the fault. P 0 and critical voltage u x ;

[0035] Based on the initial output power before the unit failure P 0 and critical voltage u x Calculate the effect of the current limiting mechanism on the units during the current limiting phase. d Axis current change and unlimited current stage d Change in shaft current;

[0036] The calculation of the effect of the current limiting mechanism on the unit during the current limiting phase d Axis current change and unlimited current stage d The ratio of the changes in shaft current is used as the current limiting depth.

[0037] Optional: Units subject to current limiting during the current limiting phase d The formula for calculating the change in shaft current is:

[0038] ;

[0039] Units subject to current limiting during the non-current limiting phase d The formula for calculating the change in shaft current is:

[0040] ;

[0041] The formula for calculating the current limiting depth is:

[0042] ;

[0043] in For the unit during the current limiting phase d Change in shaft current; For the unit in the unrestricted current phase d Change in shaft current; P 0 represents the initial output power before the unit malfunction; u x It is the critical voltage; I max This is the maximum current value that the inverter is allowed to pass through.

[0044] Furthermore, this application also discloses a transient equivalent modeling device for faults in new energy field clusters, the device comprising:

[0045] The 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 power plant cluster, and to obtain the low voltage ride-through control mode type of each unit in the new energy power plant cluster; wherein the low voltage ride-through control mode type includes at least 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.

[0046] The primary grouping module is used to perform the first grouping of the new energy power plant according to the control mode of the unit in the transient phase, and obtain the primary grouping result.

[0047] The unit proportion calculation module is used to calculate the proportion of units affected by current limiting in the new energy power plant group based on the results of the first grouping.

[0048] The secondary grouping module is used to determine whether to perform secondary grouping based on the quantity ratio results: when no secondary grouping is required, the result of the primary grouping is used as the target grouping result; when secondary grouping is required, the current limiting depth of the units affected by the current limiting link in the new energy power plant group is calculated, and secondary grouping is performed based on the result of the primary grouping according to the current limiting depth, and the result of the secondary grouping is used as the target grouping result.

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

[0050] The equivalent model output module is used to obtain the multi-machine equivalent modeling results of the new energy power plant group based on the multi-machine equivalent modeling of each unit in the same group after the single-machine equivalent modeling of each unit in the target grouping results.

[0051] Beneficial effects

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

[0053] (1) The transient equivalent modeling method for new energy power plant faults in this application can take into account the impact of voltage drop detection on the transient trajectory of unit fault current, and more accurately and specifically reflect the transient trajectory of unit short-circuit current, according to the unit under different control modes. d The transient trajectory of shaft current is used to propose a grouping index, and the effectiveness of the grouping equivalent scheme for the unit under different fault conditions is ensured by two groupings, thereby improving the accuracy of the field grouping results.

[0054] (2) The transient equivalent modeling method for new energy power plant faults in this application adopts a secondary clustering method. That is, based on the results of the first clustering, the number of units affected by the current limiting link is calculated to determine whether a secondary clustering is needed, and the current limiting depth is used as the clustering index for the secondary clustering. 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. Attached Figure Description

[0055] Figure 1 This is a flowchart of the transient equivalent modeling method for new energy field group faults in the embodiments of this application.

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

[0057] Figure 3 This application describes the current limiting mechanism in the unit where it is active and inactive, as described in the embodiments of this application. d Transient trajectory diagram of shaft current reference value.

[0058] Figure 4 For units where the current limiting circuit does not function in the embodiments of this application d Transient trajectory diagram of shaft current.

[0059] Figure 5 This application describes the current-limiting mechanism of the unit when it is active and when it is not active. d Transient trajectory diagram of shaft current reference value.

[0060] Figure 6 The unit acting as the current limiting link in the embodiments of this application d Transient trajectory diagram of shaft current.

[0061] Figure 7 The detailed model and equivalent model of the photovoltaic power station in the embodiments of this application are shown below. d Transient trajectory diagram of shaft short-circuit current.

[0062] Figure 8 The detailed model and equivalent model of the photovoltaic power station in the embodiments of this application are shown below. q Transient trajectory diagram of shaft short-circuit current.

[0063] Figure 9 This is a structural diagram of the transient equivalent modeling device for new energy field faults in the embodiments of this application.

[0064] Figure 10 This is a structural diagram of an electronic device according to an embodiment of this application. Detailed Implementation

[0065] The present application will now be further described with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present application and should not be construed as limiting the scope of protection of the present application. It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present application.

[0066] Combination Figure 1 As shown in the figure, this application discloses a method for transient equivalent modeling of faults in a new energy power plant cluster. The method includes the following steps:

[0067] Step S1: Taking into account the impact of voltage drop detection on the transient characteristics of each unit in the new energy power plant cluster, obtain the low voltage ride-through control mode of each unit in the new energy power plant cluster; wherein the low voltage ride-through control mode includes at least a control mode in which the inverter current limiting circuit of the unit does not work and a control mode in which the inverter current limiting circuit of the unit works.

[0068] Specifically, in step S1, when considering the impact of voltage dip detection on the transient characteristics of each unit in the new energy power plant cluster, due to the existence of the voltage dip detection step, such as... Figure 2 As shown, there is a delay in the switching of the low-voltage ride-through control of the unit. Because existing grouping equivalent schemes often neglect the control delay caused by voltage detection in their research on the transient process of fault current, they assume that the unit immediately switches to current-limited or unlimited state after fault determination. This results in the grouping index selected for fault transients not accurately and comprehensively reflecting the transient trajectory of the unit's fault current. However, this application's embodiment considers that the voltage drop amplitude detection stage in the low-voltage ride-through control phase will cause a transient process in the voltage drop amplitude detected by the system. Therefore, a linear function is used to fit the transient process of the voltage drop detection amplitude, where the reference values ​​for the d-axis and q-axis currents output by each unit are:

[0069] ;

[0070] in P 0 represents the initial output power before the unit malfunction; U This refers to the voltage drop detection amplitude. I dref For the unit during low voltage ride-through d shaft current reference value, where i p When the unit's current limiting circuit is not in operation dShaft current reference value, i m When the current limiting circuit of the unit is in effect d Shaft current reference value, i dref for i p and i m The smaller of the two values; I qref For the unit during low voltage ride-through q Shaft current reference value, I max This is the maximum current value that the inverter is allowed to pass through;

[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, because each unit in the new energy power plant cluster is connected to a common connection point (… PCC Because the collector line impedances of different generating units vary, the voltage drop at the generator terminals after a fault also differs. This difference in voltage drop level leads to different low-voltage ride-through control modes adopted by the generating units. In this embodiment, the low-voltage ride-through control modes include two types: a control mode where the inverter current-limiting circuit is not activated, and a control mode where the inverter current-limiting circuit is activated. When considering the impact of voltage drop detection on the transient characteristics of each generating unit in the renewable energy cluster, units with different degrees of voltage drop at their generator terminals adopt different low-voltage ride-through control modes, resulting in different corresponding current transient characteristics.

[0073] (1) When the current limiting circuit of the generator unit in the new energy power plant group is not in effect, the current transient characteristics of the unit under the corresponding control mode are:

[0074] When the voltage drop at the generator terminal exceeds the critical voltage, the voltage drop is calculated based on the voltage drop detection amplitude. i p It is always less than during the fault transient process. i m ,like Figure 3 As shown, the inverter output current amplitude never reached the maximum allowable current value. I max At this time, the unit's current limiting circuit does not function, and according to i p Transient analytical output d shaft current, where d The magnitude of the shaft current shows an upward trend in response to the random drop in terminal voltage. d The transient trajectory of the shaft current is as follows Figure 4 As shown;

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

[0076] When the voltage drop at the generator terminal is equal to or lower than the critical voltage, the voltage drop is calculated based on the voltage drop detection amplitude. i p Less than the initial stage of the fault i m Subsequently, the detected amplitude continued to drop as the voltage decreased. i p Rise and surpass i m ,like Figure 5 As shown, the inverter output current is subject to the maximum allowable current value. I max Limitations; at this time, the unit will, according to the initial stage of the fault... i p Transient analytical output d shaft current, where d The magnitude of the shaft current increases with the random drop in terminal voltage until... i p Rise and surpass i m Subsequently, the unit's current limiting mechanism takes effect, at which point, according to... i m Transient analytical output d shaft current, where d The magnitude of the shaft current decreases randomly with the drop in terminal voltage, showing a downward trend. d The transient trajectory of the shaft current is as follows Figure 6 As shown.

[0077] Furthermore, the two low-voltage ride-through control modes adopted in the embodiments of this application have the following characteristics: For units where the current limiting circuit does not function... i p It is always less than during the fault transient process. i m Therefore, there is no fault transient process i p = i m Intersection; Units with current-limiting mechanisms i p The fault started less than i m Subsequently, as the voltage detection value continued to drop... i p Rise and surpass i m Therefore, during the fault transient process, there exists i p = i mThe intersection point.

[0078] Based on the above characteristics, the low-voltage ride-through control mode type adopted by the generating unit in the new energy power plant cluster described in this application embodiment is determined based on the value of the d-axis current reference value, wherein the determination process includes:

[0079] List the situations where the current limiting circuits of each unit in the new energy power plant cluster are not functioning during the fault transient process. d Shaft current reference value i p Analytical expression 、 When the flow limiting mechanism is in effect d Shaft current reference value i m Analytical expression, obtaining the initial output power before unit failure. P 0;

[0080] Based on the initial output power of the unit before the fault and the current limiting links of each unit during the fault transient process, when they are active or inactive. d The analytical formula for the shaft current reference value is used to calculate the current limiting circuit under different conditions, whether it is active or not. d Terminal voltage with the same shaft current reference value; where according to the formula i p = i m The specific expression can be obtained from the formula:

[0081] ;

[0082] The input power of the unit can be utilized according to the above formula. P 0 can be calculated to satisfy i p = i m Terminal voltage.

[0083] The calculated terminal voltage is used as the critical voltage for determining the corresponding unit control mode. u x It also determines whether the unit's terminal voltage has dropped to the critical voltage, and determines the type of low-voltage ride-through control mode used by the unit based on the determination result.

[0084] Specifically, when the generator terminal voltage has not dropped to the critical voltage, the voltage drop is calculated based on the voltage drop detection amplitude. i p and i m The transient trajectories do not intersect during the fault transient process, at which point the unit's current limiting circuit does not function; when the unit's terminal voltage drops to or below the critical voltage, the current limiting circuit is calculated based on the voltage drop detection amplitude. i p andi m The transient trajectories intersect during the fault transient process, at which point the unit's current limiting circuit comes into effect.

[0085] Step S2: Divide the control modes of each unit during the transient phase according to the low-voltage ride-through control mode type to obtain the first grouping result; since the units adopt two control modes d The transient trajectories of shaft short-circuit currents differ significantly, therefore the units adopting different control modes are divided into two groups, which is the first grouping of the plant group.

[0086] It should be noted that this application can divide a farm into two groups based on the results of the first grouping. Since the grouping results of the first grouping are affected by the degree of system failure, when the degree of system failure is deep or shallow, most units in the farm will be in the same control mode and will be assigned to the same group after the first grouping. The grouping effect of the first grouping is severely reduced or even fails. Furthermore, this application proposes a grouping method of second grouping, that is, based on the results of the first grouping, the proportion of units affected by the current limiting link is calculated to determine whether second grouping is needed, and the "current limiting depth" is used as the grouping index for second grouping.

[0087] Step S3: Based on the results of the first clustering, calculate the proportion of units affected by current limiting mechanisms within the new energy power plant cluster; the steps for calculating the proportion of units affected by current limiting mechanisms within the new energy power plant cluster are as follows:

[0088] ;

[0089] Where W represents the percentage of units in the new energy power plant cluster that are subject to current limiting. n x The number of generating units that act as current-limiting mechanisms within the new energy power plant cluster; n This refers to the total number of generating units within the new energy power plant cluster.

[0090] Step S4: Determine whether to perform secondary grouping based on the quantity ratio results: When secondary grouping is not required, the result of the primary grouping is used as the target grouping result; when secondary grouping is required, calculate the current limiting depth of the units affected by the current limiting link in the new energy field group, perform secondary grouping on the primary grouping result according to the current limiting depth, and use the result of secondary grouping as the target grouping result.

[0091] Specifically, in step S4, after one grouping, two groups are obtained based on the unit control mode. If the number of units in the two groups is not significantly different, the equivalence effect after grouping is good, and the result of one grouping is the final grouping result. If the number of units in the two groups is significantly different, the following two situations will occur:

[0092] (1) When the system fault is minor, the voltage drop at the generator terminals of each unit in the power plant is shallow, and the current limiting circuits of most units do not function, the units d The transient trajectories of the axis currents are not significantly different, so secondary grouping is not required.

[0093] (2) When the system fault is severe, the voltage drop at the generator terminals of each unit in the power plant is significant, and the current limiting circuits of most units are activated, the units... d The transient trajectories of the axis currents differ significantly, necessitating secondary grouping.

[0094] Furthermore, when determining whether to perform secondary grouping based on the quantity ratio results, this application first determines whether the quantity ratio of units subject to current limiting mechanisms within the new energy power plant cluster is greater than a threshold:

[0095] When the proportion of units affected by the current limiting mechanism exceeds the threshold, the units affected by the current limiting mechanism in the first grouping result are grouped a second time.

[0096] When the proportion of units affected by the current limiting mechanism 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.

[0097] More specifically, the grouping index for secondary grouping in this application takes into account the impact of voltage drop detection on units affected by current limiting, while also ensuring the equivalent model's accuracy under different fault conditions. When a power plant cluster needs secondary grouping, the current limiting depth of units affected by current limiting is calculated as the grouping index for secondary grouping. Secondary grouping is then performed based on the results of the primary grouping to obtain the final grouping result. The steps for calculating the current limiting depth of units affected by current limiting within the new energy power plant cluster include:

[0098] Obtain the initial output power of each unit before the fault. P 0 and critical voltage u x ;

[0099] Based on the initial output power before the unit failure P 0 and critical voltage u x Calculate the effect of the current limiting mechanism on the units during the current limiting phase. d Axis current change and unlimited current stage d Shaft current change:

[0100] (1) Units under the current limiting effect during the current limiting phase d The formula for calculating the change in shaft current is:

[0101] ;

[0102] (2) Units under current limiting effect during the non-current limiting phased The formula for calculating the change in shaft current is:

[0103] ;

[0104] The calculation of the effect of the current limiting mechanism on the unit during the current limiting phase d Axis current change and unlimited current stage d The ratio of the changes in shaft current, and the obtained ratio is used as the current limiting depth:

[0105] The formula for calculating the current limiting depth is:

[0106] ;

[0107] in For the unit during the current limiting phase d Change in shaft current; For the unit in the unrestricted current phase d Change in shaft current; P 0 represents the initial output power before the unit malfunction; u x It is the critical voltage; I max This is the maximum current value that the inverter is allowed to pass through.

[0108] Step S5: Based on the target grouping results, perform single-machine equivalent modeling on the units divided into the same group to obtain the multi-machine equivalent model after single-machine equivalent modeling of the same group.

[0109] Step S6: Based on the single-unit equivalent model of each unit in the target group in the target group results, obtain the multi-unit equivalent modeling results of the new energy power plant group.

[0110] Furthermore, to verify the feasibility of the method in this application, based on pscad The simulation platform was used to build a detailed model of the photovoltaic power plant. Following the implementation steps described above, a transient equivalent model of the photovoltaic power plant fault, taking into account the impact of voltage drop detection, was constructed. The detailed model of the photovoltaic power plant was output. d, q Shaft fault current and equivalent model output d, q The transient trajectory of the shaft fault current is as follows: Figure 7 , Figure 8 As shown; based on Figure 7 and Figure 8The results show that the fault current transient trajectory of the equivalent model of the photovoltaic power station can fit the fault current transient trajectory of the detailed model of the photovoltaic power station well, verifying the effectiveness of the fault transient equivalent modeling method for inverter-type renewable energy power plant groups that takes into account the influence of voltage drop detection proposed in this application. In summary, the clustering index used in the fault transient equivalent modeling method for renewable energy power plant groups proposed in this application can account for the influence of voltage drop detection on the fault characteristics of the unit, more accurately and specifically reflect the short-circuit current transient trajectory of the unit, and use the clustering index to ensure the effectiveness and accuracy of the clustered equivalent scheme under different fault conditions through primary and secondary clustering.

[0111] like Figure 9 As shown, this application also discloses a device for transient equivalent modeling of faults in a new energy field cluster, the device comprising:

[0112] The 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 power plant cluster, and to obtain the low voltage ride-through control mode type of each unit in the new energy power plant cluster; wherein the low voltage ride-through control mode type includes at least 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.

[0113] The primary grouping module is used to perform the first grouping of the new energy power plant according to the control mode of the unit in the transient phase, and obtain the primary grouping result.

[0114] The unit proportion calculation module is used to calculate the proportion of units affected by current limiting in the new energy power plant group based on the results of the first grouping.

[0115] The secondary grouping module is used to determine whether to perform secondary grouping based on the quantity ratio results: when no secondary grouping is required, the result of the primary grouping is used as the target grouping result; when secondary grouping is required, the current limiting depth of the units affected by the current limiting link in the new energy power plant group is calculated, and secondary grouping is performed based on the result of the primary grouping according to the current limiting depth, and the result of the secondary grouping is used as the target grouping result.

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

[0117] The equivalent model output module is used to obtain the multi-machine equivalent modeling results of the new energy power plant group based on the multi-machine equivalent modeling of each unit in the same group after the single-machine equivalent modeling of each unit in the target grouping results.

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

[0119] like Figure 10 As shown in the illustration, this application also provides an electronic device, including a processor and a memory, and a program or instructions stored in the memory and executable on the processor, which, when executed by the processor, implement as follows: Figure 1 The various processes of the method embodiments shown are all capable of achieving the same technical effect, and will not be described again here to avoid repetition.

[0120] This application embodiment also provides a readable storage medium storing a program or instructions that, when executed by a processor, implement the above-described functionality. Figure 1 The various processes described in the embodiments of the method described herein can achieve the same technical effect, and will not be repeated here to avoid repetition.

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

[0122] It should be understood that the phrase "one embodiment" or "an embodiment" throughout the specification means that a specific feature, structure, or characteristic related to the embodiment is included in at least one embodiment of this application. Therefore, "in one embodiment" or "in an embodiment" appearing throughout the specification does not necessarily refer to the same embodiment. Furthermore, these specific features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. It should be understood that in the various embodiments of this application, the sequence numbers of the above-described processes do not imply a sequential order of execution; 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 this application. The sequence numbers of the above-described embodiments are merely descriptive and do not represent the superiority or inferiority of the embodiments.

[0123] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

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

[0125] The units described above as separate components may or may not be physically separate. The components shown as units may or may not be physical units. They may be located in one place or distributed across multiple network units. Some or all of the units may be selected to achieve the purpose of this embodiment according to actual needs.

[0126] In addition, each functional unit in the various embodiments of this application can be integrated into one processing unit, or each unit can be a separate unit, or two or more units can be integrated into one unit; the integrated unit can be implemented in hardware or in the form of hardware plus software functional units.

[0127] Those skilled in the art will understand that all or part of the steps of the above method embodiments can be implemented by hardware related to program instructions. The aforementioned program can be stored in a computer-readable storage medium. When the program is executed, it performs the steps of the above method embodiments. The aforementioned storage medium includes various media that can store program code, such as mobile storage devices, read-only memory (ROM), magnetic disks, or optical disks.

[0128] Alternatively, if the integrated units described above are implemented as software functional modules and sold or used as independent products, they can also be stored in a computer-readable storage medium. Based on this understanding, the technical solutions of the embodiments of this application, or the parts that contribute to the prior art, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a device (which may be a terminal or platform, etc.) to execute all or part of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as mobile storage devices, ROMs, magnetic disks, or optical disks.

[0129] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A method for transient equivalent modeling of faults in a new energy power plant cluster, characterized in that, The method includes the following steps: Taking into account the impact of voltage dip detection on the transient characteristics of each unit in the new energy power plant cluster, the low voltage ride-through control mode type of each unit in the new energy power plant cluster is obtained; wherein the low voltage ride-through control mode includes at least a control mode in which the inverter current limiting circuit of the unit does not work and a control mode in which the inverter current limiting circuit of the unit works. The new energy power plant group was first grouped according to the control mode of the unit in the transient phase, and the first grouping result was obtained. Based on the results of a single clustering, calculate the percentage of units within the new energy power plant cluster affected by current limiting mechanisms. Whether to perform secondary grouping is determined based on the quantity ratio results: when secondary grouping is not required, the result of primary grouping is used as the target grouping result; when secondary grouping is required, the current limiting depth of the units affected by the current limiting link in the new energy field group is calculated, and secondary grouping is performed based on the result of primary grouping according to the current limiting depth, and the result of secondary grouping is used as the target grouping result. Based on the target clustering results, single-unit equivalent modeling is performed on the units that are grouped into the same cluster after clustering, and multi-unit equivalent modeling results of new energy power plant clusters are obtained. The multi-machine equivalent modeling results of the new energy power plant cluster are obtained based on the multi-machine equivalent modeling results of the single-machine equivalent modeling of each unit in the same group in the target grouping results.

2. The method for transient equivalent modeling of new energy field cluster faults according to claim 1, characterized in that, When considering the impact of voltage dip detection on the transient characteristics of each unit in the renewable energy power plant cluster, a linear function is used to fit the transient process of the voltage dip detection amplitude, where the reference values ​​for the d-axis and q-axis currents output by each unit are: ； in P 0 represents the initial output power before the unit malfunction; U This refers to the voltage drop detection amplitude. I dref For the unit during low voltage ride-through d shaft current reference value, where i p When the unit's current limiting circuit is not in operation d Shaft current reference value, i m When the current limiting circuit of the unit is in effect d Shaft current reference value, i dref for i p and i m The smaller of the two values; I qref For the unit during low voltage ride-through q Shaft current reference value, I max This is the maximum current value that the inverter is allowed to pass through; 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 method for transient equivalent modeling of new energy field cluster faults according to claim 2, characterized in that, When considering the impact of voltage drop detection on the transient characteristics of each unit in the new energy power plant cluster, the low voltage ride-through control mode includes a control mode in which the current limiting link of the unit inverter is not activated and a control mode in which the current limiting link of the unit inverter is activated. When the current limiting circuit of the generating units in the new energy power plant cluster is not in operation, the transient current characteristics of the units under the corresponding control mode are as follows: When the voltage drop at the generator terminal exceeds the critical voltage, the voltage drop is calculated based on the voltage drop detection amplitude. i p It is always less than during the fault transient process. i m The inverter output current amplitude never reached the maximum allowable current value. I max At this time, the unit's current limiting circuit does not function, and according to i p Transient analytical output d shaft current, where d The magnitude of the shaft current shows an upward trend in random terminal voltage drops. When the current limiting circuit of the generating units in the new energy power plant cluster is in effect, the transient current characteristics of the units under the corresponding control mode are as follows: When the voltage drop at the generator terminal is equal to or lower than the critical voltage, the voltage drop is calculated based on the voltage drop detection amplitude. i p Less than the initial stage of the fault i m Subsequently, the detected amplitude continued to drop as the voltage decreased. i p Rise and surpass i m The inverter output current is limited by the maximum allowable current value. I max Limitations; at this time, the unit will, according to the initial stage of the fault... i p Transient analytical output d shaft current, where d The magnitude of the shaft current increases with the random drop in terminal voltage until... i p Rise and surpass i m Subsequently, the unit's current limiting mechanism takes effect, at which point, according to... i m Transient analytical output d shaft current, where d The magnitude of the shaft current decreases randomly with the drop in terminal voltage.

4. The method for transient equivalent modeling of new energy field cluster faults according to claim 3, characterized in that, The low-voltage ride-through control mode type adopted by the generating units in the new energy power plant cluster is determined based on the value of the d-axis current reference value. The determination process includes: List the situations where the current limiting circuits of each unit in the new energy power plant cluster are not functioning during the fault transient process. d Shaft current reference value i p Analytical expression 、 When the flow limiting mechanism is in effect d Shaft current reference value i m Analytical expression, obtaining the initial output power before unit failure. P 0; Based on the initial output power of the unit before the fault and the current limiting links of each unit during the fault transient process, when they are active or inactive. d The analytical formula for the shaft current reference value is used to calculate the current limiting circuit under different conditions, whether it is active or not. d Terminal voltages with the same shaft current reference value; The calculated terminal voltage is used as the critical voltage for determining the corresponding unit control mode. It is then determined whether the unit terminal voltage has dropped to the critical voltage. Based on the determination result, the type of low voltage ride-through control mode adopted by the unit is determined.

5. The method for transient equivalent modeling of new energy field cluster faults according to claim 4, characterized in that, When the generator terminal voltage has not dropped to the critical voltage, the voltage drop is calculated based on the voltage drop detection amplitude. i p and i m The transient trajectories do not intersect during the fault transient process, at which point the unit's current limiting circuit does not function; when the unit's terminal voltage drops to or below the critical voltage, the current limiting circuit is calculated based on the voltage drop detection amplitude. i p and i m The transient trajectories intersect during the fault transient process, at which point the unit's current limiting circuit comes into effect; The generating units with and without current-limiting mechanisms are divided into two groups, resulting in the first-order grouping of the new energy power plant cluster.

6. The method for transient equivalent modeling of new energy field cluster faults according to claim 1, characterized in that, The steps for calculating the percentage of generating units affected by current limiting mechanisms within the new energy power plant cluster are as follows: ； Where W represents the percentage of units in the new energy power plant cluster that are subject to current limiting. n x The number of generating units that act as current-limiting mechanisms within the new energy power plant cluster; n This refers to the total number of generating units within the new energy power plant cluster.

7. The method for transient equivalent modeling of new energy field faults according to claim 6, characterized in that, When determining whether to perform secondary grouping based on the quantity ratio, the first step is to determine whether the quantity ratio of units subject to current limiting mechanisms within the new energy power plant cluster is greater than a threshold: When the proportion of units affected by the current limiting mechanism exceeds the threshold, the units affected by the current limiting mechanism in the first grouping result are grouped a second time. When the proportion of units affected by the current limiting mechanism 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.

8. The method for transient equivalent modeling of new energy field cluster faults according to claim 1, characterized in that, The steps for calculating the current limiting depth of the generating units affected by the current limiting mechanism within the new energy power plant cluster include: Obtain the initial output power of each unit before the fault. P 0 and critical voltage u x ; Based on the initial output power before the unit failure P 0 and critical voltage u x Calculate the effect of the current limiting mechanism on the units during the current limiting phase. d Shaft current change and unlimited current stage d Change in shaft current; The calculation of the effect of the current limiting mechanism on the unit during the current limiting phase d Shaft current change and unlimited current stage d The ratio of the changes in shaft current is used as the current limiting depth.

9. The method for transient equivalent modeling of new energy field cluster faults according to claim 8, characterized in that, Units subject to current limiting during the current limiting phase d The formula for calculating the change in shaft current is: ； Units subject to current limiting during the non-current limiting phase d The formula for calculating the change in shaft current is: ； The formula for calculating the current limiting depth is: ； in For the unit during the current limiting phase d Change in shaft current; For the unit in the unrestricted current phase d Change in shaft current; P 0 represents the initial output power before the unit malfunction; u x It is the critical voltage; I max This is the maximum current value that the inverter is allowed to pass through.

10. A transient equivalent modeling device for faults in a new energy field cluster, characterized in that, The device includes: The 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 power plant cluster, and to obtain the low voltage ride-through control mode type of each unit in the new energy power plant cluster; wherein the low voltage ride-through control mode type includes at least 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. The primary grouping module is used to perform the first grouping of the new energy power plant according to the control mode of the unit in the transient phase, and obtain the primary grouping result. The unit proportion calculation module is used to calculate the proportion of units affected by current limiting in the new energy power plant group based on the results of the first grouping. The secondary grouping module is used to determine whether to perform secondary grouping based on the quantity ratio results: when no secondary grouping is required, the result of the primary grouping is used as the target grouping result; when secondary grouping is required, the current limiting depth of the units affected by the current limiting link in the new energy power plant group is calculated, and secondary grouping is performed based on the result of the primary grouping according to the current limiting depth, and the result of the secondary grouping is used as the target grouping result. The equivalent modeling module for units in the same group is used to perform single-unit equivalent modeling on units that are grouped into the same group after being grouped, based on the target grouping results, to obtain multi-unit equivalent modeling results for new energy power plant groups; 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 of the single-machine equivalent modeling of each group of units in the target grouping results.

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