Alternating current and direct current system power angle stability analysis method and system

Abstract

The invention discloses a power angle stability analysis method and system for an AC-DC system, and relates to the technical field of safety and stability analysis of a power system.The topological structure of the AC-DC system is obtained, steady-state power flow analysis is conducted on the topological structure according to preset output combination parameters, and initial operation parameters are obtained; and performing power angle stability margin evaluation on the system on the basis to obtain a thermal power generating unit instability interval, determining a second thermal power generating unit power angle and a critical removal power angle according to the initial operation parameters on the basis of the thermal power generating unit instability interval, and performing non-periodic instability analysis by adopting the second thermal power generating unit power angle, the critical removal power angle and the initial operation parameters. And obtaining a power angle stability margin evaluation value. The technical problem that the accuracy of stability margin evaluation of the alternating-current and direct-current system is low due to the fact that the influence of direct-current control mode switching is not fully considered when the power angle stability analysis of the alternating-current and direct-current system is carried out in the existing research is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of power system security and stability analysis, and particularly relates to a method and system for analyzing the power angle stability of an AC-DC system. Background Art

[0002] With the increasing access capacity of new energy devices such as wind power, photovoltaic power, and direct current. The increase in the DC feeding capacity makes the coupling effect between the AC-DC system and between DC converter stations closer. At the same time, the transient stability problems such as power angle and voltage caused after system faults are becoming more prominent, which has a serious impact on the safe and stable operation of the system. In the AC-DC system, the disturbance of active power may cause the system to lose power angle stability. In the existing research on the power angle stability margin of the AC-DC hybrid system, the influence of the DC control mode switching during the transient process is not fully considered, resulting in a low accuracy of the stability margin evaluation of the AC-DC system. Summary of the Invention

[0003] The present invention provides a method and system for analyzing the power angle stability of an AC-DC system, which solves the technical problem that the existing research does not fully consider the influence of DC control mode switching when analyzing the power angle stability of the AC-DC system, resulting in a low accuracy of the stability margin evaluation of the AC-DC system.

[0004] A method for analyzing the power angle stability of an AC-DC system provided by the first aspect of the present invention includes:

[0005] Obtain the topological structure of the AC-DC system, and perform a steady-state power flow analysis on the topological structure according to preset output combination parameters to obtain the initial operating parameters corresponding to the AC-DC system;

[0006] Based on the initial operating parameters, perform a power angle stability assessment on the AC-DC system to obtain the unstable interval of the thermal power unit;

[0007] Based on the unstable interval of the thermal power unit, determine the power angle of the second thermal power unit and the critical clearing angle corresponding to the AC-DC system according to the initial operating parameters;

[0008] Perform aperiodic instability analysis using the power angle of the second thermal power unit, the critical clearing angle, and the initial operating parameters to obtain the power angle stability margin evaluation value corresponding to the AC-DC system.

[0009] Optionally, the step of performing a steady-state power flow analysis on the topological structure according to preset output combination parameters to obtain the initial operating parameters corresponding to the AC-DC system includes:

[0010] Construct a simulation model of the thermal power unit near the DC feeding drop point using the topological structure;

[0011] Input the preset output combination parameters into the simulation model of the thermal power unit near the DC feeding point to obtain the target AC-DC system simulation model;

[0012] Conduct a system power flow analysis on the target AC-DC system simulation model to obtain the initial operating parameters corresponding to the AC-DC system.

[0013] Optionally, the step of performing a power angle stability assessment on the AC-DC system based on the initial operating parameters to obtain the instability interval of the thermal power unit includes:

[0014] Input the initial operating parameters and the characteristic parameters of the AC-DC system into a preset first power angle function to obtain the power angle of the first thermal power unit;

[0015] Input the initial operating parameters and the power angle of the first thermal power unit into a preset thermal power unit power angle characteristic model to obtain the electromagnetic power of the first thermal power unit and the electromagnetic power of the second thermal power unit;

[0016] Construct the instability interval of the thermal power unit by using the electromagnetic power of the first thermal power unit and the electromagnetic power of the second thermal power unit.

[0017] Optionally, the step of determining the power angle of the second thermal power unit and the critical clearing angle corresponding to the AC-DC system based on the instability interval of the thermal power unit according to the initial operating parameters includes:

[0018] Judge whether the actual output of the thermal power unit in the initial operating parameters is within the instability interval of the thermal power unit;

[0019] If the actual output of the thermal power unit is within the instability interval of the thermal power unit, adjust the output combination parameters, and jump to execute the step of performing a steady-state power flow analysis on the topological structure according to the preset output combination parameters to obtain the initial operating parameters corresponding to the AC-DC system;

[0020] If the actual output of the thermal power unit is not within the instability interval of the thermal power unit, perform a fault clearing analysis on the initial operating parameters by using the piecewise calculation method to obtain the power angle of the second thermal power unit corresponding to the AC-DC system;

[0021] Input the power angle of the second thermal power unit and the initial operating parameters into a preset critical clearing angle function to obtain the critical clearing angle corresponding to the AC-DC system.

[0022] Optionally, the step of performing an aperiodic instability analysis by using the power angle of the second thermal power unit, the critical clearing angle and the initial operating parameters to obtain the power angle stability margin evaluation value corresponding to the AC-DC system includes:

[0023] Perform power angle characteristic analysis using the power angle of the second thermal power unit, the critical clearing power angle, and the initial operating parameters to obtain the acceleration area and the maximum deceleration area corresponding to the AC / DC system;

[0024] Determine whether the acceleration area is greater than or equal to the maximum deceleration area;

[0025] If the acceleration area is greater than or equal to the maximum deceleration area, adjust the output combination parameters and jump to execute the step of performing steady-state power flow analysis on the topological structure according to the preset output combination parameters to obtain the initial operating parameters corresponding to the AC / DC system;

[0026] If the acceleration area is less than the maximum deceleration area, determine the critical clearing power angle as the power angle stability margin evaluation value corresponding to the AC / DC system.

[0027] Optionally, the step of performing power angle characteristic analysis using the power angle of the second thermal power unit, the critical clearing power angle, and the initial operating parameters to obtain the acceleration area and the maximum deceleration area corresponding to the AC / DC system includes:

[0028] Construct a maximum deceleration interval using the critical clearing power angle and the power angle of the second thermal power unit;

[0029] Based on the maximum deceleration interval, perform a differential operation on the difference between the electromagnetic power output of the thermal power unit in the initial operating parameters and the actual output of the thermal power unit to obtain the maximum deceleration area corresponding to the AC / DC system;

[0030] Perform a difference operation on the power angle of the second thermal power unit and the initial power angle of the thermal power unit in the initial operating parameters to obtain a first difference;

[0031] Perform a multiplication operation on the actual output of the thermal power unit and the first difference to obtain the power angle acceleration area corresponding to the AC / DC system.

[0032] A power angle stability analysis system provided in the second aspect of the present invention includes:

[0033] An acquisition module for obtaining the topological structure of the AC / DC system and performing steady-state power flow analysis on the topological structure according to the preset output combination parameters to obtain the initial operating parameters corresponding to the AC / DC system;

[0034] A stability evaluation module for performing power angle stability evaluation on the AC / DC system based on the initial operating parameters to obtain the unstable interval of the thermal power unit;

[0035] An analysis module, configured to determine the power angle of the second thermal power unit and the critical clearing power angle corresponding to the AC-DC system according to the initial operating parameters based on the instability interval of the thermal power unit;

[0036] A margin evaluation module, configured to perform aperiodic instability analysis by using the power angle of the second thermal power unit, the critical clearing power angle, and the initial operating parameters, so as to obtain a power angle stability margin evaluation value corresponding to the AC-DC system.

[0037] An electronic device provided in the third aspect of the present invention includes a memory and a processor. When a computer program stored in the memory is executed by the processor, the processor is caused to execute the steps of the power angle stability analysis method for an AC-DC system as described in any one of the above.

[0038] A computer-readable storage medium provided in the fourth aspect of the present invention has a computer program stored thereon. When the computer program is executed, the power angle stability analysis method for an AC-DC system as described in any one of the above is implemented.

[0039] A computer program product provided in the fifth aspect of the present invention includes a computer program stored on a non-transitory computer-readable storage medium. The computer program includes program instructions. When the program instructions are executed by a computer, the computer is caused to execute the power angle stability analysis method for an AC-DC system as described in any one of the above.

[0040] As can be seen from the above technical solutions, the present invention has the following advantages:

[0041] By obtaining the initial operating parameters of the AC-DC system, and based on this, evaluating the power angle stability margin of the system to obtain the instability interval of the thermal power unit, and then evaluating the power angle stability margin of the AC-DC system according to the instability interval of the thermal power unit and the initial operating parameters, the accurate evaluation of the power angle stability margin of the DC control is realized, overcoming the technical problem that in the prior art research on the power angle stability analysis of the AC-DC system, the influence of the DC control mode switching is not fully considered, resulting in a low accuracy of the stability margin evaluation of the AC-DC system. Compared with the traditional power angle stability margin evaluation method, the present invention evaluates the power angle stability margin of the AC-DC system according to the instability interval of the thermal power unit and the initial operating parameters, considers the power angle characteristics of the thermal power unit under different control strategies, clarifies the influence of the DC control switching on the power angle stability of the thermal power unit, realizes the accurate evaluation of the AC-DC system, and improves the reliability of the AC-DC system. Description of the Drawings

[0042] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0043] Figure 1 It is a flowchart of the steps of a method for analyzing the power angle stability of an AC-DC system provided in Embodiment 1 of the present invention;

[0044] Figure 2 It is a flowchart of the steps of a method for analyzing the power angle stability of an AC-DC system provided in Embodiment 2 of the present invention;

[0045] Figure 3 It is a schematic structural diagram of an LCC-HVDC system provided in Embodiment 2 of the present invention;

[0046] Figure 4 It is a schematic control diagram of a rectifier in an LCC-HVDC system provided in Embodiment 2 of the present invention;

[0047] Figure 5 It is a schematic control diagram of an inverter in an LCC-HVDC system provided in Embodiment 2 of the present invention;

[0048] Figure 6 It is a schematic diagram of the voltage-current characteristic curve corresponding to the DC control strategy provided in Embodiment 2 of the present invention;

[0049] Figure 7 It is a schematic structural diagram of an AC-DC system provided in Embodiment 2 of the present invention;

[0050] Figure 8 It is a schematic diagram of the output curve of a thermal power unit under the second output combination provided in Embodiment 2 of the present invention;

[0051] Figure 9 It is a schematic diagram of the power angle curve of a thermal power unit under the second output combination provided in Embodiment 2 of the present invention;

[0052] Figure 10 It is a schematic diagram of the terminal voltage curve of the DC feeding point under the second output combination provided in Embodiment 2 of the present invention;

[0053] Figure 11 It is a schematic diagram of the DC output power curve under the second output combination provided in Embodiment 2 of the present invention;

[0054] Figure 12 It is a schematic diagram of the output curve of a thermal power unit under the third output combination provided in Embodiment 2 of the present invention;

[0055] Figure 13Schematic diagram of the power angle curve of a thermal power unit under the third output combination provided in the second embodiment of the present invention;

[0056] Figure 14 Schematic diagram of the terminal voltage curve of the DC feeding point under the third output combination provided in the second embodiment of the present invention;

[0057] Figure 15 Schematic diagram of the DC output power curve under the third output combination provided in the second embodiment of the present invention;

[0058] Figure 16 Schematic diagram of the output curve of a thermal power unit under the fifth output combination provided in the second embodiment of the present invention;

[0059] Figure 17 Schematic diagram of the power angle curve of a thermal power unit under the fifth output combination provided in the second embodiment of the present invention;

[0060] Figure 18 Schematic diagram of the terminal voltage curve of the DC feeding point under the fifth output combination provided in the second embodiment of the present invention;

[0061] Figure 19 Schematic diagram of the DC output power curve under the fifth output combination provided in the second embodiment of the present invention;

[0062] Figure 20 Equivalent circuit diagram of the AC-DC system under normal operating conditions provided in the second embodiment of the present invention;

[0063] Figure 21 Equivalent circuit diagram of the AC-DC system under fault conditions provided in the second embodiment of the present invention;

[0064] Figure 22 Power angle characteristic curve diagram of a thermal power unit considering DC control switching provided in the second embodiment of the present invention;

[0065] Figure 23 Schematic diagram of the DC receiving-end voltage curve during the power angle stability analysis of the AC-DC system under the first output ratio provided in the second embodiment of the present invention;

[0066] Figure 24 Schematic diagram of the power angle curve of a thermal power unit during the power angle stability analysis of the AC-DC system under the first output ratio provided in the second embodiment of the present invention;

[0067] Figure 25 Schematic diagram of the DC receiving-end voltage curve during the power angle stability analysis of the AC-DC system under the second output ratio provided in the second embodiment of the present invention;

[0068] Figure 26 Schematic diagram of the power angle curve of a thermal power unit during the power angle stability analysis of the AC-DC system under the second output ratio provided in the second embodiment of the present invention;

[0069] Figure 27 It is a structural block diagram of an AC-DC system power angle stability analysis system provided in Embodiment 3 of the present invention;

[0070] Figure 28 It is a structural block diagram of an electronic device provided in Embodiment 4 of the present invention. Specific embodiments

[0071] The embodiments of the present invention provide an AC-DC system power angle stability analysis method and system, which are used to solve the technical problem that in the existing research on AC-DC system power angle stability analysis, the influence of DC control mode switching is not fully considered, resulting in low accuracy of the stability margin evaluation of the AC-DC system.

[0072] In order to make the object, features, and advantages of the present invention more obvious and understandable, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the embodiments described below are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0073] Please refer to Figure 1 , Figure 1 It is a step flowchart of an AC-DC system power angle stability analysis method provided in Embodiment 1 of the present invention.

[0074] An AC-DC system power angle stability analysis method provided by the present invention includes:

[0075] Step 101: Obtain the topological structure of the AC-DC system, and perform steady-state power flow analysis on the topological structure according to the preset output combination parameters to obtain the initial operating parameters corresponding to the AC-DC system;

[0076] The AC-DC system refers to the local system of thermal power units near the DC feeding point.

[0077] The initial operating parameters refer to the initial power angles of thermal power units before the fault of the AC-DC system obtained through power flow calculation, the initial voltages of each node, the initial active power of each branch, etc.

[0078] The output combination parameters refer to the preset DC output / capacity and thermal power output / capacity.

[0079] In an embodiment of the present invention, the topological structure of the AC-DC system is obtained, and a local simulation model of a thermal power unit near the DC feeding point is constructed using the topological structure. The preset output combination parameters are input into the local simulation model of the thermal power unit near the DC feeding point to obtain a target simulation model. Steady-state power flow analysis is performed on the target simulation model to obtain the initial operating parameters corresponding to the AC-DC system.

[0080] Step 102: Based on the initial operating parameters, perform a power angle stability assessment on the AC-DC system to obtain the unstable interval of the thermal power unit;

[0081] In an embodiment of the present invention, the initial operating parameters and the characteristic parameters of the AC-DC system are input into a preset first power angle function to obtain the first thermal power unit power angle. The initial operating parameters and the first thermal power unit power angle are input into a preset thermal power unit power angle characteristic model to obtain the electromagnetic power of the first thermal power unit and the electromagnetic power of the second thermal power unit. The unstable interval of the thermal power unit is constructed using the electromagnetic power of the first thermal power unit and the electromagnetic power of the second thermal power unit.

[0082] It should be noted that the first power angle function is specifically:

[0083]

[0084] Where, is that the DC receiving-end voltage is lower than the command value, is the second simplification coefficient, is the third simplification coefficient, is the reactance of the i-th line, is the first simplification coefficient, is the first action coefficient, is the second action coefficient, is the internal electromotive force of the thermal power unit, is the infinite bus voltage, is the first thermal power unit power angle, and i is the line number.

[0085] It should be noted that the thermal power unit power angle characteristic model is specifically:

[0086] Thermal power unit power angle characteristic model under normal conditions:

[0087]

[0088] Thermal power unit power angle characteristic model under fault conditions:

[0089]

[0090] Where, is the electromagnetic power output by the thermal power unit, is the reactance of the first line, is the reactance of the third line, is the power angle of the thermal power unit, is the DC output current, is the voltage phase angle, is the receiving-end voltage of the DC, is the phase angle,

[0091] Step 103: Based on the instability interval of the thermal power unit, determine the second power angle of the thermal power unit and the critical clearing angle corresponding to the AC-DC system according to the initial operating parameters;

[0092] The second power angle of the thermal power unit refers to the power angle of the thermal power unit at the moment of fault clearing.

[0093] The critical clearing angle refers to the critical clearing angle of the thermal power unit.

[0094] In the embodiment of the present invention, it is judged whether the actual output of the thermal power unit with the initial operating parameters is in the instability interval of the thermal power unit. When the actual output of the thermal power unit is in the instability interval of the thermal power unit, the output combination parameters are adjusted and Step 101 is re-executed. When the actual output of the thermal power unit is not in the instability interval of the thermal power unit, the second power angle of the thermal power unit and the critical clearing angle corresponding to the AC-DC system are calculated through the initial operating parameters.

[0095] Step 104: Perform aperiodic instability analysis using the second power angle of the thermal power unit, the critical clearing angle, and the initial operating parameters to obtain the power angle stability margin evaluation value corresponding to the AC-DC system.

[0096] In the embodiment of the present invention, the second power angle of the thermal power unit, the critical clearing angle, and the initial operating parameters are input into the preset power angle instability function of the thermal power unit to obtain the accelerating area and the maximum decelerating area. It is judged whether the accelerating area is greater than or equal to the maximum decelerating area. When the accelerating area is less than the maximum decelerating area, the critical clearing angle is determined as the power angle stability margin evaluation value corresponding to the AC-DC system.

[0097] In the embodiment of the present invention, by obtaining the initial operating parameters of the AC-DC system and performing a power angle stability margin evaluation on the system based on this, the instability interval of the thermal power unit is obtained, and then the power angle stability margin of the AC-DC system is evaluated according to the instability interval of the thermal power unit and the initial operating parameters, thus realizing an accurate evaluation of the power angle stability margin of the DC control. It solves the technical problem that in the existing research on the power angle stability analysis of the AC-DC system, the influence of the DC control mode switching is not fully considered, resulting in a low accuracy of the stability margin evaluation of the AC-DC system. Compared with the traditional power angle stability margin evaluation method, the present invention evaluates the power angle stability margin of the AC-DC system according to the instability interval of the thermal power unit and the initial operating parameters, considers the power angle characteristics of the thermal power unit under different control strategies, clarifies the influence of the DC control switching on the power angle stability of the thermal power unit, realizes an accurate evaluation of the AC-DC system, and improves the reliability of the AC-DC system.

[0098] Please refer to Figure 2 , Figure 2 which is the flowchart of the steps of a method for analyzing the power angle stability of an AC-DC system provided in the second embodiment of the present invention.

[0099] A method for analyzing the power angle stability of an AC-DC system provided by the present invention includes:[[]]

[0100] Step 201: Obtain the topological structure of the AC-DC system, and perform a steady-state power flow analysis on the topological structure according to preset output combination parameters to obtain the initial operating parameters corresponding to the AC-DC system;

[0101] Further, step 201 includes the following sub-steps:

[0102] S11: Use the topological structure to construct a simulation model of the thermal power units near the DC feeding point;

[0103] In the embodiment of the present invention, obtain the topological structure of the AC-DC system, and use the topological structure to construct a simulation model of the thermal power units near the DC feeding point.

[0104] S12: Input the preset output combination parameters into the simulation model of the thermal power units near the DC feeding point to obtain a target AC-DC system simulation model;

[0105] In the embodiment of the present invention, adjust the model parameters of the simulation model of the thermal power units near the DC feeding point according to the preset output combination parameters to obtain a target AC-DC system simulation model.

[0106] S13: Perform a system power flow analysis on the target AC-DC system simulation model to obtain the initial operating parameters corresponding to the AC-DC system.

[0107] In the embodiment of the present invention, use the target AC-DC system simulation model to perform a system power flow analysis to obtain the initial operating parameters corresponding to the AC-DC system.

[0108] It is worth mentioning that the specific conventional DC control strategy in the AC-DC system is: select LCC-HVDC as the research object, and its system structure is as Figure 3 shown. The control block diagram of the rectifier (Rec) can be seen in Figure 4 , and its control strategy is mainly divided into minimum trigger angle control (CIA), constant current control (CC), and voltage-dependent current limiting control (VDCOL). The relevant parameters of the rectifier control are shown in Table 1. The control block diagram of the inverter (Inv) can be seen in Figure 5 , and its control strategy is mainly divided into constant extinction angle control (CEA), constant current control (CC), voltage-dependent current limiting control (VDCOL), and current error control (CEC). The relevant parameters of the inverter control are shown in Table 2. The U-I characteristic curve corresponding to the LCC-HVDC DC control strategy is asFigure 6 as shown

[0109] Table 1

[0110]

[0111] Table 2

[0112]

[0113] It is worth mentioning that, referring to Figure 7 as shown, in the scenario of power angle instability in the AC / DC system (i.e., the scenario of power angle instability in the local system of a thermal power plant near the DC landing point), the system parameters are shown in Table 3. The system operation scenarios under different output ratios of the conventional DC and thermal power units are constructed. A three-phase short-circuit fault occurs at a location near bus L of Line-II, and Line-II is disconnected after 0.1 s, so as to study the possible power angle instability scenarios and the evolution trend of power angle stability in the system under different output ratios of DC and thermal power.

[0114] Table 3

[0115]

[0116] Based on this local system, keeping the output of the conventional DC unchanged at 2700 MW and changing the output of the thermal power unit, the transient simulation results of the system are as follows. From Table 4 and Figures 8 - 19 the simulation results, it can be seen that when the output of the thermal power is low, the power angle can recover during the transient process and there will be no power angle instability phenomenon; when the output of the thermal power is high, the power angle of the thermal power unit will swing and diverge during the transient process, and when the thermal power is fully loaded, the power angle of the thermal power unit will even show an asynchronous instability phenomenon. It can be seen that: the connection of the conventional DC weakens the damping characteristics of the synchronous machine, and the higher the output ratio of the synchronous machine, the worse its damping characteristics.

[0117] Table 4

[0118]

[0119] According to the above analysis, as the output ratio of the thermal power unit in the system increases continuously, the power angle of the thermal power unit will show a swinging and divergent instability phenomenon, and in severe cases, an asynchronous instability phenomenon will occur. The DC side voltage U di of the conventional DC inverter and the feeder point terminal voltage U W satisfy:

[0120] (1)

[0121] where is the turns ratio of the transformer between the inverter and the receiving grid, is the DC filter inductor. It can be seen that when a fault occurs in the receiving system, the feeder point terminal voltage UW decreases, resulting in a decrease in the DC-side voltage U of the inverter di decreases, and the control of the inverter and rectifier switches. The switching process is as follows: 1. Under normal operating conditions, the rectifier operates in the CC control mode, and the inverter operates in the CEA control mode. 2. When a system fault occurs and Udi decreases, the U-I characteristic curve of the inverter control moves downward. The DC rectifier operates under VDCOL control, and the inverter operates in the CEC control mode.

[0122] Step 202: Input the initial operating parameters and the characteristic parameters of the AC-DC system into a preset first power angle function to obtain the power angle of the first thermal power unit;

[0123] The power angle of the first thermal power unit refers to the power angle of the thermal power unit corresponding to the time when the DC receiving-end voltage is equal to U WL at the start of DC control switching.

[0124] The characteristic parameters refer to the inherent attribute parameters of the AC-DC system, including but not limited to line reactance, etc.

[0125] In the embodiment of the present invention, the initial operating parameters and the characteristic parameters of the AC-DC system are input into a preset first power angle function, and the first power angle function is solved to obtain the power angle of the first thermal power unit.

[0126] Step 203: Input the initial operating parameters and the power angle of the first thermal power unit into a preset thermal power unit power angle characteristic model to obtain the electromagnetic power of the first thermal power unit and the electromagnetic power of the second thermal power unit;

[0127] The electromagnetic power of the first thermal power unit refers to the electromagnetic power of the thermal power unit corresponding to δ GC (i.e., the thermal power angle corresponding to the control switching moment) when the DC is under Control 1

[0128] The electromagnetic power of the second thermal power unit refers to the electromagnetic power of the thermal power unit corresponding to δ GC (i.e., the thermal power angle corresponding to the control switching moment) when the DC is under Control 2

[0129] It should be noted that, as shown in Figure 22 , the solid line represents the power angle characteristic curve of the thermal power unit when the DC control is under Control 1: constant current at the rectifier side (CC) and constant extinction angle at the inverter side (CEA) control mode. The dashed line represents the power angle characteristic curve of the thermal power unit when the DC control is under Control 2: voltage-dependent current limiting control (VDCOL) and current deviation control at the inverter side (CEC) mode. When the power angle of the thermal power unit is less than δ GC , the DC receiving-end voltage level is relatively high, and the DC is under Control 1; when the power angle of the thermal power unit is greater than δ GC , the DC receiving-end voltage level is relatively low, and the DC is under Control 2.

[0130] In an embodiment of the present invention, the initial operating parameters and the power angle of the first thermal power unit are used as inputs to a preset power angle characteristic model of the thermal power unit, and the electromagnetic power of the first thermal power unit and the electromagnetic power of the second thermal power unit are obtained.

[0131] It should be noted that under normal operating conditions, the rectifier side operates in the CC control mode. At this time, the DC side current I of the LCC-HVDC d satisfies:

[0132] (2)

[0133] where is the DC side current under normal operating conditions.

[0134] The inverter side operates in the CEA control, and the extinction angle of the inverter side is a fixed value . Substituting Equation (2) and into Equation (1) gives:

[0135] (3)

[0136] Let , then Equation (3) can be rewritten as:

[0137] (4)

[0138] Equation (4) shows that the output characteristic of the conventional DC under normal operating conditions can be equivalent to a constant current source. Equivalent the thermal power unit to a voltage source and represent the receiving-end network with an infinite power source. The equivalent circuit of the system under normal operating conditions is as follows Figure 20 shown. The mathematical model of the power angle characteristic curve of the thermal power unit can be obtained, and the derivation process is as follows:

[0139] The expression of the electromagnetic power output by the thermal power unit is:

[0140] (5)

[0141] where the output current of the thermal power unit is the combined result of the infinite power source, the thermal power unit, and the current injected into node G by the DC receiving end, denoted as , , respectively, and the specific expressions are:

[0142] (6)

[0143] where is the voltage of the infinite power source, is the internal potential of the thermal power unit.

[0144] According to the principle of linear network superposition, the mathematical expression of the output current of the thermal power unit can be obtained as follows:

[0145] (7)

[0146] Substituting Equation (7) into Equation (5), the mathematical expression of the electromagnetic power of the thermal power unit can be obtained:

[0147] (8)

[0148] Among them, is the electromagnetic power of the thermal power unit, is the internal electromotive force of the thermal power unit, is the infinite bus voltage, is the power angle of the thermal power unit, is the phase angle of the receiving-end voltage of the conventional DC.

[0149] It can be seen that the mathematical expression of the electromagnetic power of the thermal power unit is affected by the DC output current II and the phase angle of the terminal voltage . Therefore, it is necessary to analyze the and the power angle of the thermal power unit The corresponding mathematical relationship between them is used to clarify the influence of DC connection on the power angle characteristic curve of the thermal power unit. Refer to Figure 20 As shown, it can be seen that the receiving-end voltage of the conventional DC is the combined result of the voltages generated by the injected currents at nodes S, G, and W at node W, which are respectively denoted as , , , and its expression is as shown in Equation (9):

[0150] (9)

[0151] Among them, is the DC output current.

[0152] According to the principle of linear network superposition, it is the sum of the three, as shown in Equation (10):

[0153] (10)

[0154] Among them, is the receiving-end voltage of the conventional DC.

[0155] The DC uses the grid voltage orientation, and the power factor , the d-axis component I of the output current d is I I , and the q-axis component I q is 0. Taking the d-axis of the terminal voltage as the real-axis reference direction, perform dq decomposition on Equation (10) and substitute U d , U q, I d , I q The expressions for the d-axis and q-axis components of the DC receiving-end voltage can be obtained:

[0156] (11)

[0157] Where, is the d-axis component of the terminal voltage, is the q-axis component of the terminal voltage.

[0158] Through equation (11), U W can be transformed into the corresponding relational expression. By simplifying equation (11) using trigonometric functions, we get:

[0159] (12)

[0160] From equation (4), it can be seen that under normal operating conditions, I I = 1.0 pu. At this time, the magnitude of the conventional DC receiving-end voltage U W is:

[0161] (13)

[0162] According to the functional relationship between U W and , substituting equation (13) into equation (10), a mathematical expression between and can be established:

[0163] (14)

[0164] By performing Euler expansion on equation (14), the imaginary parts on both sides of the equal sign satisfy:

[0165] (15)

[0166] By simplifying equation (15) using trigonometric functions, the corresponding mathematical expression between and can be obtained:

[0167] (16)

[0168] Where, the phase angle is equal to:

[0169] (17)

[0170] Thus, the mathematical model of the power angle characteristic curve of the thermal power unit under normal operating conditions can be determined as:

[0171] (18)

[0172] Under fault conditions, the rectifier side operates in the VDCOL control mode. At this time, the DC side current I of the LCC-HVDC d satisfies:

[0173] (19)

[0174] where is the rectifier side DC voltage command value corresponding to VDCOL control, taken as 0.9 pu, is the U-I curve slope corresponding to VDCOL control. The inverter side operates in CEC control, and the inverter side trigger lead angle is a fixed value , and the inverter side DC voltage U di satisfies:

[0175] (20)

[0176] Let , then equation (20) can be rewritten as:

[0177] (21)

[0178] The inverter side DC voltage U di and the rectifier side DC voltage U dr satisfy:

[0179] (22)

[0180] Combining (19) - equation (22), it can be obtained that the DC side current I d and the DC receiving-end voltage U W satisfy:

[0181] (23)

[0182] From this, the relationship between the current I I and the DC receiving-end voltage U W is:

[0183] (24)

[0184] From equation (21) and equation (23), it can be seen that at this time, the output characteristic of the conventional DC is a current source controlled by U W . The equivalent circuit of the system is as shown in Figure 21 . The electromagnetic power expression of the thermal power unit is the same as equation (8). Since I d is affected by U W , the electromagnetic power mathematical expression of the thermal power unit is affected by U W and δ WTherefore, it is necessary to analyze U W and δ W The corresponding mathematical relationship with the power angle δ of the thermal power unit is obtained, and the influence of DC access on the power angle characteristic curve of the thermal power unit is clarified. The DC receiving-end voltage G is as shown in Equation (10). The expressions of the d-axis component and q-axis component of the DC receiving-end voltage are the same as Equation (11). Through Equation (11), U can be transformed into the corresponding relationship with δ W . By simplifying Equation (11) through trigonometric functions, Equation (12) can be obtained. Combining Equation (12) and Equation (23), it can be seen that at this time, the amplitude U of the conventional DC receiving-end voltage G is: W

[0185] (25)

[0186] By solving Equation (24), it can be known that the mathematical expression of U W with respect to δ G is:

[0187] (26)

[0188] The mathematical expression between δ W and δ G is the same as Equation (14) and can be summarized as follows:

[0189] (27)

[0190] Thus, the mathematical model of the power angle characteristic curve of the thermal power unit under fault conditions can be clarified as:

[0191] (28)

[0192] Step 204: Construct the instability interval of the thermal power unit by using the electromagnetic power of the first thermal power unit and the electromagnetic power of the second thermal power unit.

[0193] In the embodiment of the present invention, the electromagnetic power P of the first thermal power unit M1 and the electromagnetic power P of the second thermal power unit M2 are used to construct the instability interval [P M1 , P M2 of the thermal power unit.

[0194] Step 205: Based on the instability interval of the thermal power unit, determine the power angle and critical clearing angle of the second thermal power unit corresponding to the AC-DC system according to the initial operating parameters;

[0195] Further, Step 205 includes the following sub-steps:

[0196] ​S21. Determine whether the actual output of the thermal power unit with the initial operating parameters is within the instability range of the thermal power unit;

[0197] In the embodiment of the present invention, it is determined that the actual output of the thermal power unit with the initial operating parameters is within the instability range of the thermal power unit.

[0198] It should be noted that when the output of the thermal power unit is between P M1 and P M2 , at this time, the thermal power unit has no stable power angle, and the thermal power unit will exhibit a swing divergence instability phenomenon; when the output of the thermal power unit is between P M1 and P M2 , at this time, the thermal power unit has no stable power angle, and the thermal power unit will exhibit a swing divergence instability phenomenon. When the output of the thermal power unit further increases and the output of the thermal power unit is higher than P M2 , at this time, the accelerating area of the power angle of the thermal power unit will be greater than the maximum decelerating area, and the thermal power unit will exhibit a non-periodic instability phenomenon of the power angle.

[0199] S22. If the actual output of the thermal power unit is within the instability range of the thermal power unit, then adjust the output combination parameters, and jump to execute the step of performing a steady-state power flow analysis on the topological structure according to the preset output combination parameters to obtain the initial operating parameters corresponding to the AC-DC system;

[0200] In the embodiment of the present invention, if the actual output of the thermal power unit is within the instability range of the thermal power unit, then the thermal power unit has no stable power angle, adjust the output combination parameters, and jump to execute step 201.

[0201] S23. If the actual output of the thermal power unit is not within the instability range of the thermal power unit, then use the piecewise calculation method to perform a fault removal analysis on the initial operating parameters to obtain the second power angle of the thermal power unit corresponding to the AC-DC system;

[0202] In the embodiment of the present invention, if the actual output of the thermal power unit is not within the instability range of the thermal power unit, then the thermal power unit will exhibit a non-periodic instability phenomenon of the power angle, and use the piecewise calculation method to perform a fault removal analysis on the initial operating parameters to obtain the second power angle of the thermal power unit corresponding to the AC-DC system.

[0203] It should be noted that the step of performing a fault removal analysis on the initial operating parameters using the piecewise calculation method is specifically: input the initial operating parameters into the preset piecewise calculation function to obtain the second power angle of the thermal power unit corresponding to the AC-DC system.

[0204] The piecewise calculation function is specifically:

[0205]

[0206] Among them, is the second power angle of the thermal power unit, is the actual output of the thermal power unit, is the sectional coefficient, is the initial power angle of the thermal power unit, is the rated angular velocity of the system, with a value of 18000° / s, is the inertia time constant of the thermal power unit, is the solution interval of the sectional calculation method, with a value of 0.05 s.

[0207] S24. Input the power angle and initial operating parameters of the second thermal power unit into the preset critical clearing power angle function to obtain the corresponding critical clearing power angle of the AC-DC system.

[0208] In the embodiment of the present invention, the power angle and initial operating parameters of the second thermal power unit are used as the input of the preset critical clearing power angle function to obtain the corresponding critical clearing power angle of the AC-DC system.

[0209] It should be noted that the critical clearing power angle function is specifically:

[0210]

[0211] Step 206. Perform aperiodic instability analysis using the power angle of the second thermal power unit, the critical clearing power angle, and the initial operating parameters to obtain the corresponding power angle stability margin evaluation value of the AC-DC system.

[0212] Furthermore, step 206 includes the following sub-steps:

[0213] S31. Perform power angle characteristic analysis using the power angle of the second thermal power unit, the critical clearing power angle, and the initial operating parameters to obtain the corresponding accelerating area and maximum decelerating area of the AC-DC system;

[0214] Furthermore, S31 includes the following sub-steps:

[0215] S311. Construct the maximum deceleration interval using the critical clearing power angle and the power angle of the second thermal power unit;

[0216] S312. Based on the maximum deceleration interval, perform a differential operation on the difference between the output electromagnetic power of the thermal power unit of the initial operating parameters and the actual output of the thermal power unit to obtain the corresponding maximum decelerating area of the AC-DC system;

[0217] In the embodiment of the present invention, the critical clearing power angle, the power angle of the second thermal power unit, the output electromagnetic power of the thermal power unit of the initial operating parameters, and the actual output of the thermal power unit are input into the preset maximum decelerating area function to obtain the corresponding maximum decelerating area of the AC-DC system.

[0218] It should be noted that the maximum decelerating area function is specifically:

[0219]

[0220] Among them, is the maximum deceleration area, is the output electromagnetic power of the thermal power unit, is the actual output of the thermal power unit, is the power angle of the thermal power unit, δ GF is the power angle of the second thermal power unit, δ Gcr is the critical clearing power angle.

[0221] S313. Perform a difference operation on the power angle of the second thermal power unit and the initial power angle of the thermal power unit with the initial operating parameters to obtain a first difference;

[0222] S314. Perform a multiplication operation on the actual output of the thermal power unit and the first difference to obtain the power angle acceleration area corresponding to the AC-DC system.

[0223] In an embodiment of the present invention, the power angle of the second thermal power unit, the initial power angle of the thermal power unit, and the actual output of the thermal power unit are input into a preset power angle acceleration area function to obtain the power angle acceleration area corresponding to the AC-DC system.

[0224] It should be noted that the power angle acceleration area function is specifically:

[0225]

[0226] Among them, is the power angle acceleration area.

[0227] S32. Determine whether the acceleration area is greater than or equal to the maximum deceleration area;

[0228] S33. If the acceleration area is greater than or equal to the maximum deceleration area, adjust the output combination parameters and jump to execute the step of performing a steady-state power flow analysis on the topological structure according to the preset output combination parameters to obtain the initial operating parameters corresponding to the AC-DC system;

[0229] In an embodiment of the present invention, determine whether the acceleration area is greater than or equal to the maximum deceleration area. If the acceleration area is greater than or equal to the maximum deceleration area, it indicates that the power angle of the thermal power unit has an aperiodic instability. Adjust the output combination parameters and jump to execute step 201.

[0230] S34. If the acceleration area is less than the maximum deceleration area, determine the critical clearing power angle as the power angle stability margin evaluation value corresponding to the AC-DC system.

[0231] In an embodiment of the present invention, if the acceleration area is less than the maximum deceleration area, it indicates that the power angle of the thermal power unit does not have an aperiodic instability. Determine the critical clearing power angle as the power angle stability margin evaluation value corresponding to the AC-DC system.

[0232] It should be noted that the smaller the stability margin evaluation value is, the more stable the AC-DC system is.

[0233] It is worth mentioning that, taking the Figure 7 shown system as an example, combining with the AC-DC system power angle stability analysis method in steps 201-206, the Figure 7 corresponding system power angle stability margin is evaluated. The obtained results are shown in Table 5, and the corresponding simulation results are as Figures 23 - 26 shown.

[0234]

[0235] Table 5

[0236] In the embodiment of the present invention, by obtaining the initial operation parameters of the AC-DC system and based on this, the power angle stability margin of the system is evaluated to obtain the unstable interval of the thermal power unit. Then, according to the unstable interval of the thermal power unit and the initial operation parameters, the power angle stability margin of the AC-DC system is evaluated, thereby realizing the accurate evaluation of the power angle stability margin of the DC control, and solving the technical problem that the existing research does not fully consider the influence of the DC control mode switching when analyzing the power angle stability of the AC-DC system, resulting in a low accuracy of the stability margin evaluation of the AC-DC system. Compared with the traditional power angle stability margin evaluation method, the present invention evaluates the power angle stability margin of the AC-DC system according to the unstable interval of the thermal power unit and the initial operation parameters, considers the power angle characteristics of the thermal power unit under different control strategies, clarifies the influence of the DC control switching on the power angle stability of the thermal power unit, realizes the accurate evaluation of the AC-DC system, and improves the reliability of the AC-DC system.

[0237] Please refer to Figure 27 , Figure 27 which is the structural block diagram of a power angle stability analysis system for an AC-DC system provided in Embodiment 3 of the present invention.

[0238] A power angle stability analysis system for an AC-DC system provided by the present invention includes:

[0239] An acquisition module 301, configured to obtain the topological structure of the AC-DC system, and perform a steady-state power flow analysis on the topological structure according to preset output combination parameters to obtain the initial operation parameters corresponding to the AC-DC system;

[0240] A stability evaluation module 302, configured to perform a power angle stability evaluation on the AC-DC system based on the initial operation parameters to obtain the unstable interval of the thermal power unit;

[0241] An analysis module 303, configured to determine the power angle of the second thermal power unit and the critical clearing power angle corresponding to the AC-DC system based on the unstable interval of the thermal power unit and according to the initial operation parameters;

[0242] A margin evaluation module 304, which is used to perform aperiodic instability analysis by using the power angle of the second thermal power unit, the critical clearing power angle, and the initial operating parameters, so as to obtain the power angle stability margin evaluation value corresponding to the AC-DC system.

[0243] Furthermore, the acquisition module 301 includes:

[0244] A first construction sub-module, which is used to construct a simulation model of the thermal power unit near the DC feeding point by using the topological structure;

[0245] A loading sub-module, which is used to input the preset output combination parameters into the simulation model of the thermal power unit near the DC feeding point to obtain the target AC-DC system simulation model;

[0246] A power flow analysis sub-module, which is used to perform system power flow analysis on the target AC-DC system simulation model to obtain the initial operating parameters corresponding to the AC-DC system.

[0247] Furthermore, the stability evaluation module 302 includes:

[0248] A first analysis sub-module, which is used to input the initial operating parameters and the characteristic parameters of the AC-DC system into a preset first power angle function to obtain the power angle of the first thermal power unit;

[0249] A second analysis sub-module, which is used to input the initial operating parameters and the power angle of the first thermal power unit into a preset thermal power unit power angle characteristic model to obtain the electromagnetic power of the first thermal power unit and the electromagnetic power of the second thermal power unit;

[0250] A second construction sub-module, which is used to construct an instability interval of the thermal power unit by using the electromagnetic power of the first thermal power unit and the electromagnetic power of the second thermal power unit.

[0251] Furthermore, the margin evaluation module 304 includes:

[0252] A third analysis sub-module, which is used to judge whether the actual output of the thermal power unit of the initial operating parameters is within the instability interval of the thermal power unit;

[0253] If the actual output of the thermal power unit is within the instability interval of the thermal power unit, adjust the output combination parameters, and jump to execute the step of performing steady-state power flow analysis on the topological structure according to the preset output combination parameters to obtain the initial operating parameters corresponding to the AC-DC system;

[0254] If the actual output of the thermal power unit is not within the instability interval of the thermal power unit, perform fault clearing analysis on the initial operating parameters by using the piecewise calculation method to obtain the power angle of the second thermal power unit corresponding to the AC-DC system;

[0255] A fourth analysis sub-module, which is used to input the power angle of the second thermal power unit and the initial operating parameters into a preset critical clearing power angle function to obtain the critical clearing power angle corresponding to the AC-DC system.

[0256] Further, the margin evaluation module 304 includes:

[0257] The power angle characteristic analysis sub-module is used to perform power angle characteristic analysis by using the power angle of the second thermal power unit, the critical clearing power angle, and the initial operating parameters to obtain the corresponding accelerating area and the maximum decelerating area of the AC-DC system;

[0258] The fifth analysis sub-module is used to determine whether the accelerating area is greater than or equal to the maximum decelerating area;

[0259] If the accelerating area is greater than or equal to the maximum decelerating area, adjust the output combination parameters, and jump to execute the step of performing steady-state power flow analysis on the topological structure according to the preset output combination parameters to obtain the initial operating parameters corresponding to the AC-DC system;

[0260] If the accelerating area is less than the maximum decelerating area, determine the critical clearing power angle as the power angle stability margin evaluation value corresponding to the AC-DC system.

[0261] Further, the power angle characteristic analysis sub-module includes:

[0262] The first analysis unit is used to construct the maximum decelerating interval by using the critical clearing power angle and the power angle of the second thermal power unit;

[0263] The second analysis unit is used to perform differential operation on the difference between the output electromagnetic power of the thermal power unit and the actual output of the thermal power unit of the initial operating parameters based on the maximum decelerating interval to obtain the maximum decelerating area corresponding to the AC-DC system;

[0264] The third analysis unit is used to perform difference processing on the power angle of the second thermal power unit and the initial power angle of the thermal power unit of the initial operating parameters to obtain the first difference;

[0265] The fourth analysis unit is used to perform multiplication processing on the actual output of the thermal power unit and the first difference to obtain the power angle accelerating area corresponding to the AC-DC system.

[0266] Please refer to Figure 28 , Figure 28 which is a structural block diagram of an electronic device provided in Embodiment 4 of the present invention.

[0267] An electronic device according to an embodiment of the present invention, the electronic device includes: a memory 401 and a processor 402, and a computer program is stored in the memory 402; when the computer program is executed by the processor 402, the processor 402 is caused to execute the AC-DC system power angle stability analysis method as described in any one of the above embodiments.

[0268] The memory 401 can be an electronic memory such as a flash memory, an EEPROM (Electrically Erasable Programmable Read-Only Memory), an EPROM, a hard disk, or a ROM. The memory 401 has a storage space 403 for the program code 413 for executing any of the method steps in the above-described method. For example, the storage space 403 for the program code can include respective program codes 413 for implementing the various steps in the above method. These program codes can be read from or written into one or more computer program products. These computer program products include program code carriers such as hard disks, compact discs (CDs), memory cards, or floppy disks. The program code can be compressed in an appropriate form, for example. When these codes are run by a computing processing device, they cause the computing processing device to execute each of the steps in the method described above.

[0269] Embodiment 5 of the present invention also provides a computer-readable storage medium, on which a computer program is stored, and when the computer program is executed by a processor, it implements the AC-DC system power angle stability analysis method according to any of the foregoing embodiments.

[0270] Embodiment 6 of the present invention also provides a computer program product, which includes a computer program stored on a non-transitory computer-readable storage medium, and the computer program includes program instructions. When the program instructions are executed by a computer, the computer is caused to execute the AC-DC system power angle stability analysis method according to any of the foregoing embodiments.

[0271] Those skilled in the art can clearly understand that for the convenience and brevity of description, the specific working processes of the systems, devices, and units described above can refer to the corresponding processes in the foregoing method embodiments and will not be elaborated herein.

[0272] In the several embodiments provided in the present application, it should be understood that the disclosed systems, devices, and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For example, the division of units is only a logical function division, and there can be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the displayed or discussed couplings or direct couplings or communication connections to each other can be through some interfaces, and the indirect couplings or communication connections of devices or units can be in electrical, mechanical, or other forms.

[0273] The unit described as a separation component may or may not be physically separated, and the component displayed as a unit may or may not be a physical unit, that is, it may be located in one place or may be distributed across multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0274] In addition, each functional unit in various embodiments of the present invention can be integrated in a processing unit, or each unit can exist physically alone, or two or more units can be integrated in one unit. The above integrated unit can be implemented in the form of hardware or in the form of a software functional unit.

[0275] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on such an understanding, the technical solution of the present invention, in essence, or the part that makes a contribution to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods in various embodiments of the present invention. The foregoing storage medium includes: various media such as USB flash drives, mobile hard disks, read-only memories (ROM, Read-Only Memory), random access memories (RAM, Random Access Memory), magnetic disks, or optical discs that can store program codes.

[0276] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of various embodiments of the present invention.

Claims

1. A method for analyzing power angle stability of an AC / DC system, characterized in that: include: Acquire a topological structure of an AC / DC system, and perform a steady-state power flow analysis on the topological structure according to preset output combination parameters to obtain initial operating parameters corresponding to the AC / DC system; Based on the initial operating parameters, the power angle stability of the AC / DC system is evaluated to obtain an instability range of the thermal power unit; Based on the instability interval of the thermal power unit, determining the power angle and critical cut-off power angle of the second thermal power unit corresponding to the AC / DC system according to the initial operating parameters; The power angle of the second thermal power unit, the critical cut-off power angle and the initial operating parameters are used to perform non-periodic instability analysis to obtain a power angle stability margin assessment value corresponding to the AC / DC system.

2. The AC / DC system power angle stability analysis method according to claim 1, characterized in that: The step of performing steady-state power flow analysis on the topological structure according to the preset output combination parameters to obtain initial operating parameters corresponding to the AC / DC system includes: The topological structure is used to construct a simulation model of a thermal power unit near a DC feed point; Inputting the preset output combination parameters into the simulation model of the DC feed-in point near the thermal power unit to obtain a target AC / DC system simulation model; Performing system power flow analysis on the target AC / DC system simulation model to obtain initial operating parameters corresponding to the AC / DC system.

3. The AC / DC system power angle stability analysis method according to claim 1, characterized in that: The step of performing a power angle stability assessment on the AC / DC system based on the initial operating parameters to obtain an instability interval of the thermal power unit comprises: Inputting the initial operating parameters and the characteristic parameters of the AC / DC system into a preset first power angle function to obtain a power angle of a first thermal power unit; Inputting the initial operating parameters and the power angle of the first thermal power unit into a preset thermal power unit power angle characteristic model to obtain the electromagnetic power of the first thermal power unit and the electromagnetic power of the second thermal power unit; The electromagnetic power of the first thermal power unit and the electromagnetic power of the second thermal power unit are used to construct an instability interval of the thermal power unit.

4. The AC / DC system power angle stability analysis method according to claim 1, characterized in that: The step of determining the power angle and critical cut-off power angle of the second thermal power unit corresponding to the AC / DC system based on the instability interval of the thermal power unit and according to the initial operating parameters comprises: Determining whether the actual output of the thermal power unit with the initial operating parameters is within the instability range of the thermal power unit; If the actual output of the thermal power unit is in the instability interval of the thermal power unit, the output combination parameter is adjusted, and the step of performing steady-state power flow analysis on the topological structure according to the preset output combination parameter to obtain the initial operating parameters corresponding to the AC / DC system is executed; If the actual output of the thermal power unit is not in the instability range of the thermal power unit, a segmented calculation method is used to perform a fault removal analysis on the initial operating parameters to obtain a power angle of the second thermal power unit corresponding to the AC / DC system; The power angle of the second thermal power generating unit and the initial operating parameters are input into a preset critical power removal angle function to obtain a critical power removal angle corresponding to the AC / DC system.

5. The AC / DC system power angle stability analysis method according to claim 1, characterized in that: The step of performing a non-periodic instability analysis by using the power angle of the second thermal power unit, the critical cut-off power angle and the initial operating parameters to obtain a power angle stability margin evaluation value corresponding to the AC / DC system comprises: The power angle of the second thermal power unit, the critical cut-off power angle and the initial operating parameters are used to perform a power angle characteristic analysis to obtain an acceleration area and a maximum deceleration area corresponding to the AC / DC system; Determining whether the acceleration area is greater than or equal to the maximum deceleration area; If the acceleration area is greater than or equal to the maximum deceleration area, the output combination parameter is adjusted, and the step of performing a steady-state power flow analysis on the topological structure according to the preset output combination parameter to obtain the initial operating parameters corresponding to the AC / DC system is executed; If the acceleration area is smaller than the maximum deceleration area, the critical power cut-off angle is determined as a power angle stability margin evaluation value corresponding to the AC / DC system.

6. The AC / DC system power angle stability analysis method according to claim 5, characterized in that: The step of performing power angle characteristic analysis by using the power angle of the second thermal power unit, the critical cut-off power angle and the initial operating parameters to obtain the acceleration area and the maximum deceleration area corresponding to the AC / DC system comprises: The critical cut-off power angle and the power angle of the second thermal power unit are used to construct a maximum deceleration interval; Based on the maximum deceleration interval, a differential operation is performed on the difference between the output electromagnetic power of the thermal power unit of the initial operating parameters and the actual output of the thermal power unit to obtain a maximum deceleration area corresponding to the AC / DC system; Performing difference processing on the power angle of the second thermal power generation unit and the initial power angle of the thermal power generation unit of the initial operating parameters to obtain a first difference; The actual output of the thermal power unit is multiplied by the first difference to obtain a power angle acceleration area corresponding to the AC / DC system.

7. An AC / DC system power angle stability analysis system, characterized in that: include: An acquisition module is used to obtain the topological structure of the AC / DC system, and perform steady-state power flow analysis on the topological structure according to preset output combination parameters to obtain initial operating parameters corresponding to the AC / DC system; A stability assessment module, used to perform a power angle stability assessment on the AC / DC system based on the initial operating parameters to obtain an instability interval of the thermal power unit; An analysis module, configured to determine a power angle and a critical cut-off power angle of a second thermal power unit corresponding to the AC / DC system based on the instability interval of the thermal power unit and according to the initial operating parameters; The margin assessment module is used to perform non-periodic instability analysis using the power angle of the second thermal power unit, the critical cut-off power angle and the initial operating parameters to obtain a power angle stability margin assessment value corresponding to the AC / DC system.

8. An electronic device, characterized in that: The method comprises a memory and a processor, wherein a computer program is stored in the memory, and when the computer program is executed by the processor, the processor executes the steps of the AC / DC system power angle stability analysis method according to any one of claims 1 to 6.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed, the method for analyzing power angle stability of an AC or DC system according to any one of claims 1 to 6 is implemented.

10. A computer program product, characterized in that The computer program product comprises a computer program stored on a non-transitory computer-readable storage medium, wherein the computer program comprises program instructions, wherein when the program instructions are executed by a computer, the computer is caused to execute the AC / DC system power angle stability analysis method according to any one of claims 1 to 6.

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