New Energy Aggregation Station Transient Stability Analysis Method, System, Equipment and Medium

Abstract

The present invention provides a method, system, device and medium for transient stability analysis of a new energy collection station. The method is to analyze the operating principle of a power hybrid consumption two-machine system constructed including a new energy unit and an energy storage device connected by a tie line to obtain a normal operating power model, and to analyze the power angle characteristics under fault conditions according to the constructed non-synchronous machine control model of the new energy converter to obtain the corresponding fault power angle characteristic curve. Then, based on the equal area criterion, transient stability indexes including the critical clearing angle and the critical clearing time are obtained under fault conditions according to the fault power angle characteristic curve and the normal power angle characteristic curve corresponding to the normal operating power model, and the transient stability analysis of the collection station is carried out according to the transient stability indexes to obtain the corresponding transient stability evaluation result. The present invention effectively improves the comprehensiveness and reliability of transient stability analysis based on the collaborative analysis of the interaction effects between different non-synchronous machine power sources.

Description

Technical Field

[0001] The present invention relates to the technical field of power systems, and particularly to a transient stability analysis method, system, device and medium for a new energy collection station. Background Art

[0002] Offshore wind energy resources are rich and have great power generation potential, which is of great practical significance for reducing the dependence on traditional fossil energy. In view of the intermittency, volatility and randomness of offshore wind power, the layout of energy storage inverters in a new energy collection station for offshore wind power grid connection can effectively make up for the safety and stability threats brought by the random fluctuation of wind energy to the power system. However, there are a large number of grid-connected converters in the new energy collection station for offshore wind power grid connection, and in a power system dominated by synchronous machines, the synchronization between synchronous machines depends on the real physical behavior of the rotors. The converter-based asynchronous machine power supply needs to achieve synchronization with other power supplies in the system by controlling the voltage or current vector, that is, whether the power system dominated by it can maintain synchronization depends to a certain extent on the power supply control mode and control parameters.

[0003] The existing transient stability analysis of new energy collection stations mainly focuses on the research of transient stability problems after a single asynchronous machine power supply is connected to the grid, and does not involve a comprehensive collaborative analysis from a global perspective of the interaction between different asynchronous machine power supplies. The transient stability of a new energy collection station with an asynchronous machine interaction scenario between a new energy (grid-connected) converter and an energy storage asynchronous machine power supply will inevitably be affected by the coordination between different asynchronous machine power supplies; that is, the existing transient stability analysis of new energy collection stations cannot effectively guarantee the comprehensiveness and reliability of transient stability analysis under the power mixing and consumption condition (part of the power of new energy is used to meet the demand of the receiving-end power grid, and the remaining power is stored in the energy storage module), and it is difficult to truly and effectively guarantee the safe and stable operation of the power system. Summary of the Invention

[0004] The purpose of the present invention is to provide a transient stability analysis method for a new energy collection station. By constructing a two-machine simplified model of the new energy collection station for the power mixing and consumption scenario where the energy storage device stores electricity due to the excess power generation of new energy units, and based on the construction of control models of different converters, combined with the interaction characteristics between asynchronous machine power supplies, the power angle characteristic curves between the network-forming converter for new energy grid connection and the network-forming asynchronous machine power supply for energy storage device operation are analyzed, and the equal area criterion is used to calculate the critical clearing angle and critical clearing time for the transient stability analysis of the new energy collection station, so as to realize the collaborative steady-state analysis based on the interaction between different asynchronous machine power supplies, and effectively improve the comprehensiveness and reliability of the transient stability analysis of the new energy collection station.

[0005] In order to achieve the above object, it is necessary to provide a transient stability analysis method, system, device and medium for a new energy collection station in view of the above technical problems.

[0006] In a first aspect, an embodiment of the present invention provides a method for analyzing the transient stability of a new energy collection station. The method includes the following steps:

[0007] Construct a two-machine system for power hybrid consumption, and analyze the operating principle of the two-machine system for power hybrid consumption to obtain a corresponding normal operating power model; the two-machine system for power hybrid consumption includes a new energy unit and an energy storage device connected by a tie line; the new energy unit and the energy storage device are respectively connected to the power grid through corresponding new energy converters and energy storage converters;

[0008] Respectively construct the non-synchronous machine control models of the new energy converter and the energy storage converter, and perform the power angle characteristic analysis of the fault conditions between the non-synchronous machine power supplies according to the non-synchronous machine control models of the new energy converter and the energy storage converter to obtain corresponding fault power angle characteristic curves;

[0009] According to the fault power angle characteristic curve and the normal power angle characteristic curve corresponding to the normal operating power model, obtain the transient stability index under the fault condition based on the equal area criterion; the transient stability index includes the critical clearing angle and the critical clearing time;

[0010] Perform the transient stability analysis of the collection station according to the transient stability index to obtain a corresponding transient stability evaluation result.

[0011] Further, the normal operating power model is expressed as:

[0012]

[0013] Wherein, and respectively represent the voltage amplitudes of the new energy unit and the energy storage device; represents the reactance value of the tie line between the new energy unit and the energy storage device; represents the active power transmitted from the new energy unit to the energy storage device through the tie line; represents the phase angle difference of the new energy unit relative to the energy storage device; and respectively represent the active powers output by the new energy unit and the energy storage device.

[0014] Further, both the new energy converter and the energy storage converter are network-forming converters; the steps of respectively constructing the non-synchronous machine control models of the new energy converter and the energy storage converter include:

[0015] Respectively generate corresponding reference values of the active power of the non-synchronous machine power supply based on the preset limiting rules according to the DC voltage deviations of the new energy unit and the energy storage device;

[0016] Based on the active power reference values of the asynchronous machine power supplies of the new energy unit and the energy storage device respectively, corresponding asynchronous machine control models are constructed based on the virtual synchronous control principle.

[0017] Furthermore, the asynchronous machine control model is expressed as:

[0018]

[0019] In the formula,

[0020]

[0021]

[0022] wherein, 、 、 、 、 、 、 、 、 、 、 and respectively represent the phase angle, angular frequency, inertia, damping coefficient, active power, active power reference value, power limit, DC voltage, DC voltage reference value, DC voltage deviation regulation value, control ratio and control integral coefficient of the i-th asynchronous machine power supply; represents the reference frequency.

[0023] Furthermore, the steps of analyzing the power angle characteristics under the fault conditions among the asynchronous machine power supplies according to the asynchronous machine control models of the new energy converter and the energy storage converter, and obtaining the corresponding fault power angle characteristic curves include:

[0024] According to the asynchronous machine control models of the new energy converter and the energy storage converter, the asynchronous machine control model of the new energy converter is converted with the phase of the flexible DC converter station as the reference phase to obtain the new energy asynchronous control model;

[0025] Based on the current source characteristics of the new energy unit and the energy storage device under the fault conditions, the normal operation power model is transformed into a fault operation power model;

[0026] According to the fault operation power model, the fault power angle characteristic curve is obtained.

[0027] Furthermore, the steps of obtaining the transient stability index under the fault conditions based on the equal area criterion include:

[0028] Based on the power balance analysis between asynchronous machine power sources, an angular frequency difference model and a fault duration model between asynchronous machine power sources under fault conditions are constructed; the angular frequency difference model and the fault duration model between asynchronous machine power sources under fault conditions are respectively expressed as:

[0029]

[0030]

[0031] where, and respectively represent the angular frequency difference and phase angle difference between asynchronous machine power sources after the fault condition duration ; and respectively represent the angular frequency difference and phase angle difference between asynchronous machine power sources at the start of the fault condition; represents the active power transmitted on the connection line between the new energy unit and the energy storage device under the fault condition; represents the reference value of the active power of the new energy unit; represents the phase of the new energy unit relative to the flexible DC converter station; represents the system equivalent inertia time constant; represents the base frequency;

[0032] According to the angular frequency difference model between asynchronous machine power sources under the fault condition, the fault duration model, the fault power angle characteristic curve and the normal power angle characteristic curve, calculate the accelerating area quantity and the decelerating area quantity;

[0033] Obtain the critical clearing phase angle difference and the critical clearing time when the accelerating area quantity is equal to the decelerating area quantity, and obtain the transient stability index according to the critical clearing phase angle difference and the critical clearing time.

[0034] Furthermore, the transient stability index is expressed as:

[0035]

[0036] In the formula,

[0037]

[0038]

[0039] where, and respectively represent the critical clearing angle and the critical clearing time; and respectively represent the phase angle differences at the fault start critical point and the fault recovery critical point; represents the phase of the new energy unit relative to the flexible DC converter station; represents the system equivalent inertia time constant; represents the base frequency; represents the active power reference value of the new energy unit; and respectively represent the voltage amplitudes of the new energy unit and the energy storage device; represents the reactance value of the connection line between the new energy unit and the energy storage device; 、 and respectively represent the reactance value to ground at the bus of the new energy unit, the reactance value to ground at the bus of the energy storage device, and the reactance value of the connection line between the new energy unit and the energy storage device under fault conditions; and represent a proportionality coefficient; and respectively represent the saturation currents of the new energy converter and the energy storage converter.

[0040] In a second aspect, an embodiment of the present invention provides a transient stability analysis system for a new energy collection station, and the system includes:

[0041] A normal power model acquisition module, configured to construct a power hybrid consumption two-machine system, analyze the operating principle of the power hybrid consumption two-machine system, and obtain a corresponding normal operating power model; the power hybrid consumption two-machine system includes a new energy unit and an energy storage device connected by a connection line; the new energy unit and the energy storage device are respectively connected to the power grid through corresponding new energy converters and energy storage converters;

[0042] A fault power angle characteristic analysis module, configured to respectively construct an asynchronous machine control model for the new energy converter and the energy storage converter, and perform fault condition power angle characteristic analysis between asynchronous machine power supplies according to the asynchronous machine control models of the new energy converter and the energy storage converter to obtain corresponding fault power angle characteristic curves;

[0043] A transient stability index acquisition module, configured to obtain a transient stability index under fault conditions based on the equal area rule according to the fault power angle characteristic curve and the normal power angle characteristic curve corresponding to the normal operating power model; the transient stability index includes a critical clearing angle and a critical clearing time;

[0044] A transient stability analysis module, configured to perform transient stability analysis of the collection station according to the transient stability index to obtain a corresponding transient stability evaluation result.

[0045] In a third aspect, an embodiment of the present invention further provides a computer device, including a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the computer program, the steps of the above method are implemented.

[0046] In a fourth aspect, an embodiment of the present invention further provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the steps of the above method are implemented.

[0047] The present invention provides a method, a system, a computer device, and a storage medium for analyzing the transient stability of a new energy collection station. By using the method, a power hybrid consumption two-machine system is constructed, which includes a new energy unit and an energy storage device connected by a tie line, and the new energy unit and the energy storage device are respectively connected to the power grid through corresponding new energy converters and energy storage converters. The operating principle of the power hybrid consumption two-machine system is analyzed to obtain a corresponding normal operating power model, and the non-synchronous machine control models of the new energy converter and the energy storage converter are respectively constructed. After analyzing the power angle characteristics under fault conditions according to the non-synchronous machine control model of the new energy converter to obtain a corresponding fault power angle characteristic curve, based on the equal area criterion, transient stability indicators including the critical clearing angle and the critical clearing time are obtained under fault conditions according to the fault power angle characteristic curve and the normal power angle characteristic curve corresponding to the normal operating power model, and the transient stability of the collection station is analyzed according to the transient stability indicators to obtain a corresponding transient stability evaluation result. Compared with the prior art, the method for analyzing the transient stability of the new energy collection station can realize collaborative steady-state analysis based on the interaction between different non-synchronous machine power sources, effectively improve the comprehensiveness and reliability of the transient stability analysis of the new energy collection station, and thus provide a reliable guarantee for the safe and stable operation of the power system. Description of the Drawings

[0048] Figure 1 is a schematic flowchart of the method for analyzing the transient stability of a new energy collection station according to an embodiment of the present invention;

[0049] Figure 2 is a schematic structural diagram of the power hybrid consumption two-machine system according to an embodiment of the present invention;

[0050] Figure 3 is a schematic diagram of the normal power angle characteristic curve and the fault power angle characteristic curve in the power angle characteristic analysis according to an embodiment of the present invention;

[0051] Figure 4 is a schematic diagram of a test system with a voltage level of 220 kV according to an embodiment of the present invention;

[0052] Figure 5 is based on Figure 2 a schematic diagram of the converter power change obtained by transient simulation analysis of Case 1 based on the test system;

[0053] Figure 6 is based on Figure 2Schematic diagram of the converter voltage variation obtained by the test system through transient simulation analysis of Case 1;

[0054] Figure 7 is based on Figure 2 Schematic diagram of the converter power variation obtained by the test system through transient simulation analysis of Case 2;

[0055] Figure 8 is based on Figure 2 Schematic diagram of the converter voltage variation obtained by the test system through transient simulation analysis of Case 2;

[0056] Figure 9 Schematic diagram of the structure of the transient stability analysis system for the new energy collection station in the embodiment of the present invention;

[0057] Figure 10 Internal structure diagram of the computer device in the embodiment of the present invention. Detailed implementation manners

[0058] In order to make the objectives, technical solutions and beneficial effects of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Obviously, the following described embodiments are part of the embodiments of the present invention and are only used to illustrate the present invention, but not to limit the scope of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0059] The transient stability analysis method for the new energy collection station provided by the present invention can be understood as the application status that the existing transient stability analysis of the new energy collection station does not involve comprehensive collaborative analysis from a global perspective on the interaction effects between different asynchronous machine power sources, and cannot ensure the comprehensiveness and reliability of the transient stability analysis. Therefore, a transient stability analysis method for the new energy collection station considering the interaction effects between new energy units and energy storage devices in the power hybrid consumption scenario is proposed. The following embodiments will detail the transient stability analysis method for the new energy collection station of the present invention.

[0060] In one embodiment, as Figure 1 shown, a transient stability analysis method for the new energy collection station is provided, including the following steps:

[0061] S11. Construct a two-machine system for power hybrid consumption, and analyze the operating principle of the two-machine system for power hybrid consumption to obtain the corresponding normal operating power model; among them, the two-machine system for power hybrid consumption can be understood as a simplified system of the new energy collection station designed for the operating scenario where a part of the output power of the offshore wind power new energy unit is used to meet the demand of the receiving-end power grid and the remaining power is stored in the energy storage device, and there is only one new energy grid-connected converter and an energy storage converter; asFigure 2 As shown, the two - machine system for power hybrid consumption includes a new - energy unit and an energy - storage device connected by a tie - line. The new - energy unit and the energy - storage device are respectively connected to the power grid through corresponding new - energy converters (IGBT (Insulated Gate Bipolar Transistor) in the figure) and energy - storage converters (IGBT (Insulated Gate Bipolar Transistor) in the figure). It should be noted that Figure 2 shows the two - machine system for power hybrid consumption and are the voltage phasors at the new - energy unit (Power Source 1) and the energy - storage device (Power Source 2) ends respectively; and respectively represent the reactances to ground at the busbars of the two power - source machine ends; represents the reactance of the tie - line between the two power sources, and it is assumed that the resistance and capacitance of the tie - line can be ignored; and respectively represent the active power and reactive power transmitted from Power Source 1 to Power Source 2 through the tie - line; and respectively represent and the amplitudes of.

[0062] Based on Figure 2 the system structure shown, analyzing the operation principle of the two - machine system for power hybrid consumption, it is easy to obtain that the active power exchanged on the tie - line of the two - machine system for power hybrid consumption (taking Machine 2 as the reference node, with a phase angle of 0 and ignoring the line resistance R = 0) is as shown in Equation (1):

[0063] (1)

[0064] where, and respectively represent the voltage amplitudes of the new - energy unit and the energy - storage device; represents the reactance value of the tie - line between the new - energy unit and the energy - storage device; represents the active power transmitted from the new - energy unit to the energy - storage device through the tie - line; represents the phase - angle difference of the new - energy unit relative to the energy - storage device.

[0065] Meanwhile, the active powers output by the new - energy unit (Power Source 1) and the energy - storage device (Power Source 2) satisfy:

[0066] (2)

[0067] where, and respectively represent the active power output by the new energy unit and the energy storage device.

[0068] Since equations (1) and (2) are the normal operating power expressions of the power hybrid absorption two-machine system analyzed without considering the fault condition scenario, aggregating the two can obtain the required normal operating power model, and based on this model, the power angle characteristic curve of the new energy collection station under normal operating conditions can be obtained.

[0069] S12. Respectively construct the non-synchronous machine control models of the new energy converter and the energy storage converter, and perform power angle characteristic analysis of the faults between non-synchronous machine power supplies according to the non-synchronous machine control models of the new energy converter and the energy storage converter to obtain the corresponding fault power angle characteristic curves; among them, the new energy converter and the energy storage converter are both network-forming converters based on general adaptability considerations, and the virtual synchronous control based on non-synchronous machine power supplies can enhance the stability of the power system, improve the power quality, have flexibility and autonomy, and have the advantages of simple control structure and fast response speed. This embodiment conducts a non-synchronous motor model for the scenario of virtual synchronous control network-forming converters. Specifically, the steps of respectively constructing the non-synchronous machine control models of the new energy converter and the energy storage converter include:

[0070] Respectively generate the corresponding non-synchronous machine power supply active power reference values based on the preset limiting rules according to the DC voltage deviations of the new energy unit and the energy storage device; among them, the DC voltage deviation can be understood as the deviation between the DC voltage of the converter and the DC voltage reference value, and the preset limiting rules can be understood as setting a correction coefficient based on the preset power limit, control ratio, and control integral coefficient to correct the DC voltage deviation to obtain the DC voltage deviation regulation value; the corresponding non-synchronous machine active power reference value is expressed as:

[0071] (3)

[0072] (4)

[0073] where 、 、 、 、 、 and respectively represent the active power reference value, power limit, DC voltage, DC voltage reference value, DC voltage deviation regulation value, control ratio, and control integral coefficient of the i-th non-synchronous machine power supply.

[0074] Based on the active power reference values of the asynchronous machine power supplies of the new energy unit and the energy storage device respectively, corresponding asynchronous machine control models are constructed based on the principle of virtual synchronous control; among them, the asynchronous machine control model is expressed as:

[0075] (5)

[0076] Among them, , , , , , respectively represent the phase angle, angular frequency, inertia, damping coefficient, active power and active power reference value of the i-th asynchronous machine power supply. When i = 1, it represents the asynchronous machine control model of the new energy converter. When i = 2, it represents the asynchronous machine control model of the energy storage converter; represents the reference frequency.

[0077] After obtaining the asynchronous machine control models of the new energy converter and the energy storage converter through the above method steps, the power angle characteristic curve analysis under the short-circuit fault state between the new energy unit and the energy storage device can be carried out based on this; specifically, the steps of analyzing the power angle characteristics under the fault conditions between the asynchronous machine power supplies according to the asynchronous machine control models of the new energy converter and the energy storage converter to obtain the corresponding fault power angle characteristic curves include:

[0078] According to the asynchronous machine control models of the new energy converter and the energy storage converter, the asynchronous machine control model of the new energy converter is converted with the phase of the flexible DC converter station as the reference phase to obtain a new energy asynchronous control model; among them, the new energy asynchronous control model is a converter frequency control model modified based on the rotor motion equation of a synchronous generator with the flexible DC as the phase reference. Since the new energy converter and the energy storage converter are connected in series, the power deficit ΔP is shared by the two converters, ΔP 1 and ΔP 2 (ΔP = ΔP 1 +ΔP 2 ), and ΔP 1 passes through the frequency deviation generated by the new energy converter, which is:

[0079] (6)

[0080] In the formula, and respectively represent the inertia and damping coefficient of the new energy converter.

[0081] The frequency deviation generated by ΔP2 passing through the energy storage converter is:

[0082] (7)

[0083] Wherein, and respectively represent the inertia and damping coefficient of the energy storage converter.

[0084] Based on the condition of unified system frequency ( ), and ignoring the damping coefficient and we can obtain:[[]]

[0085] (8)

[0086] Wherein, represents the system frequency.

[0087] Combining with Equation (9), we can obtain Equation (11):

[0088] (9)

[0089] Wherein, represents the equivalent inertia time constant of the system.

[0090] Based on the above derivation, the new energy asynchronous control model can be expressed as:[[]]

[0091] (10)

[0092] Wherein,

[0093] (11)

[0094] Among them, represents the frequency difference between the new energy unit and the energy storage device; represents the phase of the new energy unit relative to the flexible DC converter station; represents the equivalent inertia time constant of the system; and respectively represent the inertia of the new energy unit and the energy storage device; and respectively represent the active power and the active power reference value of the new energy unit; represents the active power output by the new energy unit.

[0095] Based on the current source characteristics of the new energy unit and the energy storage device under fault conditions, the normal operation power model is transformed into a fault operation power model. Among them, the current source characteristic can be understood as that under fault conditions, the current reaches the saturation value (maximum value); at this time, the voltage of the new energy unit is , and the voltage at the bus of the energy storage device is similarly , then it is easy to obtain that the fault operation power model is expressed as:[[]]

[0096] (12)

[0097] Wherein, 、 and respectively represent the active power of the new energy unit, the active power of the energy storage device, and the active power transmitted on the connection line between the new energy unit and the energy storage device under the fault condition; 、 and respectively represent the reactance value to the ground at the bus of the new energy unit, the reactance value to the ground at the bus of the energy storage device, and the reactance value of the connection line between the new energy unit and the energy storage device under the fault condition; represents the phase of the new energy unit relative to the flexible DC converter station; and respectively represent the saturation currents of the new energy converter and the energy storage converter.

[0098] The active power transmitted on the connection line between the new energy unit and the energy storage device under the short-circuit fault condition can be reflected by Equation (12) and the relationship between the phase of the new energy unit relative to the flexible DC converter station.

[0099] According to the fault operation power model, the fault power angle characteristic curve is obtained; wherein, the fault power angle characteristic curve can be understood as a curve describing the relationship between the active power and the power angle of the new energy collection station under the fault condition, as shown by Figure 3 the blue curve in

[0100] S13. According to the fault power angle characteristic curve and the normal power angle characteristic curve corresponding to the normal operation power model, the transient stability index under the fault condition is obtained based on the equal area criterion; the transient stability index includes the critical clearing angle and the critical clearing time; wherein, the normal power angle characteristic curve can be understood as a curve describing the relationship between the active power and the power angle of the new energy collection station in the normal operation state, and can be obtained based on the normal operation power model shown in Equations (1)-(2), as shown by Figure 3 the red curve in Figure 3 ; as shown by each point to the left of the highest point on the curve corresponds to a steady state under a certain control reference value, and since both power sources are operating normally, it can be considered that the voltage amplitude of the new energy unit and the voltage amplitude of the energy storage device are constant, and at this time, the non-synchronous machine control model shown in Equation (5) is satisfied; meanwhile, if

[0101] To ensure the efficiency and reliability of transient stability analysis, in this embodiment, preferably, transient stability evaluation indexes of a new energy collection station under fault conditions are obtained based on the equal area criterion; specifically, the steps of obtaining the transient stability indexes under fault conditions based on the equal area criterion include:

[0102] Based on the power balance analysis between asynchronous machine power supplies, an angular frequency difference model and a fault duration model between asynchronous machine power supplies under fault conditions are constructed; among them, the angular frequency difference model between asynchronous machine power supplies under fault conditions can be understood as the relationship formula of the angular frequency difference and phase angle difference between asynchronous machine power supplies after the fault duration reaches which is expressed as:

[0103] (13)

[0104] where and respectively represent the angular frequency difference and phase angle difference between asynchronous machine power supplies after the fault duration ; and respectively represent the angular frequency difference and phase angle difference between asynchronous machine power supplies at the beginning of the fault condition; represents the active power transmitted on the connection line between the new energy unit and the energy storage device under the fault condition, as shown in formula (8); represents the reference value of the active power of the new energy unit; represents the phase of the new energy unit relative to the flexible DC converter station; represents the equivalent inertia time constant of the system.

[0105] To simplify the formula, it can be set that:

[0106] (14)

[0107] where represents a proportionality coefficient; and respectively represent the saturation currents of the new energy converter and the energy storage converter.

[0108] Based on formula (14), formula (9) can be converted to:

[0109] (15)

[0110] In the formula, represents a proportionality coefficient, as shown in formula (14).

[0111] Similarly, conversely, it can also be obtained that the phase angle difference of the asynchronous machine power supply under the fault condition changes from at the beginning of the fault condition to The required duration, that is, the fault duration model is expressed as:

[0112] (16)

[0113] where represents the phase angle difference between the asynchronous machine power supplies after the fault condition duration; and and respectively represent the angular frequency difference and phase angle difference between the asynchronous machine power supplies at the start of the fault condition; represents the active power transmitted on the connection line between the new energy unit and the energy storage device under the fault condition; represents the active power reference value of the new energy unit; represents the phase of the new energy unit relative to the flexible DC converter station; represents the system equivalent inertia time constant; represents the base frequency.

[0114] Similarly, based on Equation (14), Equation (16) can be simplified to:

[0115] (17)

[0116] where represents a proportionality coefficient, as shown in Equation (14).

[0117] According to the angular frequency difference model between the asynchronous machine power supplies under the fault condition, the fault duration model, the fault power angle characteristic curve, and the normal power angle characteristic curve, calculate the accelerating area quantity and the decelerating area quantity; among them, the accelerating area quantity can be understood as the area where the power angle characteristic curve is lower than the input mechanical power of the prime mover, and the decelerating area quantity is the area where the power angle characteristic curve is higher than the input mechanical power of the prime mover; the specific analysis process of the accelerating area quantity and the decelerating area quantity is as follows:

[0118] Based on Figure 3 the shown fault power angle characteristic curve and the normal power angle characteristic curve, combined with the angular frequency difference model between the asynchronous machine power supplies under the fault condition and the fault duration model shown in Equations (15) and (17) for analysis, obtain that the operating point A is the fault start point and the operating point F is the fault recovery point, that is when it operates in the normal state corresponding to point A, the angular frequency difference between the two power supplies is 0, and there is and when a short-circuit fault occurs, causing the system to enter the fault condition, that is, causing the system to switch to the state corresponding to point B; subsequently, due to , the system state will shift to the right along curve 2, which is called "acceleration". Obviously, there must be a fault clearing point on curve 2. Assume point C is the fault clearing point. At this moment, the fault is cleared and the system returns to the normal operating condition (point E corresponding to curve 1), and the corresponding area S can be obtained. ABCD is the acceleration area; subsequently, due to , the system state will shift to the right along curve 1 from point E, which is called "deceleration". When reaching the operating point F, the system enters the critical state of fault recovery, and the corresponding area S DEF is the deceleration area. It should be noted that according to the equal area criterion, if the area S ABCD is less than the area S DEF , it can be considered that the system can maintain transient stability; otherwise, it can be considered that the system has a risk of instability.

[0119] Obtain the critical clearing phase angle difference and critical clearing time when the acceleration area quantity is equal to the deceleration area quantity, and obtain the transient stability index according to the critical clearing phase angle difference and the critical clearing time; among them, the critical clearing phase angle difference and critical clearing time can be understood as the phase angle difference and fault duration between two power sources corresponding to the fault critical clearing point on curve 2 (the system can only maintain transient stability if the fault is cleared before reaching this point). The corresponding calculation method can be implemented by referring to the existing equal area method and will not be elaborated here; the obtained critical clearing phase angle difference and critical clearing time can be used as the limit clearing angle and limit clearing time in the transient stability index respectively, and the corresponding transient stability index is expressed as:

[0120] (18)

[0121] In the formula,

[0122]

[0123]

[0124] Among them, and represent the limit clearing angle and limit clearing time respectively; and represent the phase angle differences at the fault start critical point and the fault recovery critical point respectively; represents the phase of the new energy unit relative to the VSC-HVDC converter station; represents the equivalent inertia time constant of the system; represents the base frequency; represents the active power reference value of the new energy unit; and represent the voltage amplitudes of the new energy unit and the energy storage device respectively; represents the reactance value of the connection line between the new energy unit and the energy storage device; , and respectively represent the reactance value to the ground at the bus of the new energy unit, the reactance value to the ground at the bus of the energy storage device, and the reactance value of the connection line between the new energy unit and the energy storage device under the fault condition; and represent a proportionality coefficient; and respectively represent the saturation currents of the new energy converter and the energy storage converter.

[0125] S14. Perform transient stability analysis on the substation according to the transient stability index to obtain the corresponding transient stability evaluation result; among them, the process of obtaining the transient stability evaluation result can be understood as comparing the obtained actual cut-off angle and actual fault cut-off time with the pole cut-off angle and limit cut-off time obtained above respectively. If the actual fault cut-off time is less than the limit cut-off time and the actual cut-off angle is less than the limit cut-off angle, it is considered that the system can maintain transient stability, otherwise it cannot maintain transient stability, and the final transient stability evaluation result is obtained based on the actual analysis situation.

[0126] In the embodiment of the present invention, by constructing a two-machine system for power hybrid consumption including a new energy unit and an energy storage device connected by a connection line, and the new energy unit and the energy storage device are respectively connected to the power grid through corresponding new energy converters and energy storage converters, analyze the operation principle of the two-machine system for power hybrid consumption to obtain the corresponding normal operation power model, and respectively construct the non-synchronous machine control models of the new energy converter and the energy storage converter. After analyzing the power angle characteristics under the fault condition according to the non-synchronous machine control model of the new energy converter to obtain the corresponding fault power angle characteristic curve, based on the equal area criterion, the transient stability index including the limit cut-off angle and the limit cut-off time under the fault condition is obtained according to the fault power angle characteristic curve and the normal power angle characteristic curve corresponding to the normal operation power model, and the scheme of performing transient stability analysis on the substation according to the transient stability index to obtain the corresponding transient stability evaluation result effectively solves the application defect that the existing transient stability analysis of the new energy substation does not involve comprehensive collaborative analysis from the perspective of studying the interaction between different non-synchronous machine power sources globally, and cannot ensure the comprehensiveness and reliability of the transient stability analysis, and can realize collaborative steady-state analysis based on the interaction between different non-synchronous machine power sources, effectively improve the comprehensiveness and reliability of the transient stability analysis of the new energy substation, and further provide a reliable guarantee for the safe and stable operation of the power system.

[0127] To verify the effectiveness of the transient stability analysis method for the new energy substation proposed by the present invention, this embodiment constructs a Figure 4Taking the test system with a voltage level of 220 kV shown as an example for simulation comparison experiments; this system includes two new energy units both using grid-forming converters, and a energy storage power station also using a grid-forming converter. In the scenario of large-scale new energy power generation, the energy storage power station is used to absorb the new energy power. In addition, assume Figure 4 The three grid-forming power supplies in use power synchronization control; the main parameters of the corresponding test system are shown in Table 1.

[0128] Table 1 Main parameters of the test system

[0129]

[0130] In Figure 4 and Table 1, is the reference value of the active power output by power supply j, j = 1, 2, 3; Sj is the capacity of power supply j; is the reference value of the AC voltage on the grid side of power supply j; L Tj is the inductance of the grid-connected transformer of power supply j. In this test system, the inductances of the three grid-connected transformers are equal; L j-k is the inductance of the connection line between bus j and bus k; ω0 is the rated angular frequency of the system; H sj is the inertia time constant of grid-forming power supply j.

[0131] For the above test system, simulations are carried out in the electromechanical transient analysis software PSS / E and the electromagnetic transient simulation software PSCAD / EMTDC respectively. The simulation conditions and results are shown in Table 2:

[0132] 1) Condition 1: A three-phase solid short-circuit fault occurs near bus 4 at t = 0.5 s, and the fault is cleared at t = 0.87 s;

[0133] 2) Condition 2: A three-phase solid short-circuit fault occurs near bus 4 at t = 0.5 s, and the fault is cleared at t = 0.88 s.

[0134] Table 2 Comparison table of PSS / E and PSCAD simulation results

[0135]

[0136] It can be seen from the comparison in Table 2 that the electromechanical transient simulation results and the electromagnetic transient simulation results are basically the same. Figure 5 and Figure 6 respectively show the power change situation and voltage change situation of the three converters under Condition 1; Figure 7 and Figure 8The power variation and voltage variation of three converters under Case 2 are respectively shown. According to Case 1 and Case 2, under the original conditions, the critical clearing time of this fault is about 0.37 s. It can be seen that the above simulation results are basically consistent with the critical clearing time obtained by the transient stability analysis method of the new energy collection station proposed by the present invention. The analysis results of the present invention conform to the actual situation and have high accuracy.

[0137] It should be noted that although the steps in the above flowchart are sequentially shown according to the indication of the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless there is a clear description in this article, the execution of these steps has no strict order limit, and these steps can be executed in other orders.

[0138] In one embodiment, as Figure 9 shown, a transient stability analysis system for a new energy collection station is provided. The system includes:

[0139] A normal power model acquisition module 1, configured to construct a power hybrid consumption two-machine system, analyze the operation principle of the power hybrid consumption two-machine system, and obtain a corresponding normal operation power model; the power hybrid consumption two-machine system includes a new energy unit and an energy storage device connected by a tie line; the new energy unit and the energy storage device are respectively connected to the power grid through corresponding new energy converters and energy storage converters;

[0140] A fault power angle characteristic analysis module 2, configured to respectively construct an asynchronous machine control model of the new energy converter and the energy storage converter, and perform power angle characteristic analysis of the fault conditions between asynchronous machine power supplies according to the asynchronous machine control models of the new energy converter and the energy storage converter, to obtain corresponding fault power angle characteristic curves;

[0141] A transient stability index acquisition module 3, configured to obtain a transient stability index under fault conditions based on the equal area criterion according to the fault power angle characteristic curve and the normal power angle characteristic curve corresponding to the normal operation power model; the transient stability index includes a critical clearing angle and a critical clearing time;

[0142] A transient stability analysis module 4, configured to perform transient stability analysis of the collection station according to the transient stability index, and obtain a corresponding transient stability evaluation result.

[0143] For the specific limitations of the new energy collection station transient stability analysis system, reference can be made to the limitations of the new energy collection station transient stability analysis method in the above text, and the corresponding technical effects can also be equivalently obtained, which will not be elaborated here. Each module in the above new energy collection station transient stability analysis system can be implemented in whole or in part by software, hardware, or a combination thereof. The above modules can be embedded in the processor of the computer device in hardware form or independent of it, or stored in the memory of the computer device in software form, so that the processor can call and execute the operations corresponding to each of the above modules.

[0144] Figure 10 FIG. shows the internal structure diagram of a computer device in an embodiment. The computer device may specifically be a terminal or a server. As Figure 10 shown, the computer device includes a processor, a memory, a network interface, a display, a camera, and an input device connected through a system bus. Among them, the processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The network interface of the computer device is used to communicate with an external terminal through a network connection. The computer program, when executed by the processor, implements the new energy collection station transient stability analysis method. The display screen of the computer device may be a liquid crystal display screen or an electronic ink display screen. The input device of the computer device may be a touch layer covering the display screen, or a button, a trackball, or a touchpad provided on the outer shell of the computer device, or an external keyboard, a touchpad, or a mouse, etc.

[0145] Those of ordinary skill in the art can understand that Figure 10 the structure shown in is only a block diagram of some structures related to the solution of the present invention, and does not constitute a limitation on the computer device to which the solution of the present invention is applied. The specific computing device may include more or fewer components than those shown in the figure, or combine some components, or have the same component arrangement.

[0146] In one embodiment, a computer device is provided, including a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the computer program, the steps of the above method are implemented.

[0147] In one embodiment, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by the processor, the steps of the above method are implemented.

[0148] In summary, the transient stability analysis method and system for a new energy collection station provided by the embodiments of the present invention realize the construction of a power hybrid consumption two-machine system including a new energy unit and an energy storage device connected by a tie line, and the new energy unit and the energy storage device are respectively connected to the power grid through corresponding new energy converters and energy storage converters. The operating principle of the power hybrid consumption two-machine system is analyzed to obtain the corresponding normal operating power model, and the non-synchronous machine control models of the new energy converter and the energy storage converter are respectively constructed. After analyzing the power angle characteristics under fault conditions according to the non-synchronous machine control model of the new energy converter to obtain the corresponding fault power angle characteristic curve, based on the equal area criterion, the transient stability indexes including the critical clearing angle and the critical clearing time under fault conditions are obtained according to the fault power angle characteristic curve and the normal power angle characteristic curve corresponding to the normal operating power model, and the transient stability evaluation result corresponding to the transient stability analysis of the collection station is obtained according to the transient stability indexes. This method can realize the collaborative steady-state analysis based on the interaction between different non-synchronous machine power sources, effectively improve the comprehensiveness and reliability of the transient stability analysis of the new energy collection station, and thus provide a reliable guarantee for the safe and stable operation of the power system.

[0149] Each embodiment in this specification is described in a progressive manner. For parts that are the same or similar in each embodiment, they can be referred to each other. Each embodiment focuses on the differences from other embodiments. In particular, for the system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can refer to the partial description of the method embodiment. It should be noted that the technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0150] The above embodiments only represent several preferred implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be pointed out that for those of ordinary skill in the art in this technical field, without departing from the technical principle of the present invention, several improvements and substitutions can be made, and these improvements and substitutions should also be regarded as the protection scope of the present invention. Therefore, the protection scope of the invention patent should be subject to the protection scope of the claims.

Claims

1. A transient stability analysis method for a new energy collection station, characterized in that: The method comprises the following steps: Constructing a power hybrid two-machine system, and analyzing the operating principle of the power hybrid two-machine system to obtain a corresponding normal operating power model; the power hybrid two-machine system comprises a new energy unit and an energy storage device connected by a tie line; the new energy unit and the energy storage device are connected to the power grid through corresponding new energy converters and energy storage converters respectively; Constructing the asynchronous machine control models of the new energy converter and the energy storage converter respectively, and performing the power angle characteristic analysis of the fault condition between the power sources of the asynchronous machine according to the asynchronous machine control models of the new energy converter and the energy storage converter to obtain the corresponding fault power angle characteristic curve; According to the fault power angle characteristic curve and the normal power angle characteristic curve corresponding to the normal operating power model, a transient stability index under a fault condition is obtained based on the equal area rule; the transient stability index includes a limit cut-off angle and a limit cut-off time; Performing transient stability analysis of the collection station according to the transient stability index to obtain corresponding transient stability evaluation results; The step of obtaining the transient stability index under the fault condition based on the equal area rule includes: Based on the power balance analysis between asynchronous machine power sources, an angular frequency difference model between asynchronous machine power sources under fault conditions and a fault duration model are constructed; the angular frequency difference model between asynchronous machine power sources under fault conditions and the fault duration model are respectively expressed as: in, and Respectively represent the duration of the fault condition The angular frequency difference and phase angle difference between the asynchronous machine power supplies; and They represent the angular frequency difference and phase angle difference between the non-synchronous machine power supplies at the beginning of the fault condition respectively; Indicates the active power transmitted on the interconnection line between the new energy unit and the energy storage device under fault conditions; Indicates the active power reference value of the new energy unit; Indicates the phase of the new energy unit relative to the flexible DC converter station; represents the equivalent inertia time constant of the system; Indicates the reference frequency; Calculate the acceleration area and the deceleration area according to the fault condition asynchronous machine power source angular frequency difference model, the fault duration model, the fault power angle characteristic curve and the normal power angle characteristic curve; A critical cut-off phase angle difference and a critical cut-off time when the acceleration area amount is equal to the deceleration area amount are obtained, and the transient stability index is obtained according to the critical cut-off phase angle difference and the critical cut-off time.

2. The transient stability analysis method of a new energy collection station according to claim 1, characterized in that: The normal operating power model is expressed as: in, and Respectively represent the voltage amplitudes of the new energy unit and the energy storage device; Indicates the reactance value of the interconnection line between the new energy unit and the energy storage device; Indicates the active power transmitted by the new energy unit to the energy storage device via the interconnection line; Indicates the phase angle difference between the new energy unit and the energy storage device; and They respectively represent the active power output by the new energy units and the energy storage device.

3. The transient stability analysis method of a new energy collection station according to claim 1, characterized in that: The new energy converter and the energy storage converter are both grid-type converters; The steps of respectively constructing the asynchronous machine control models of the new energy converter and the energy storage converter include: Generate a corresponding active power reference value of the asynchronous machine power supply according to the DC voltage deviation of the new energy generator set and the energy storage device based on a preset limiting rule; According to the active power reference values ​​of the asynchronous machine power supplies of the new energy unit and the energy storage device, corresponding asynchronous machine control models are constructed based on the virtual synchronous control principle.

4. The transient stability analysis method of a new energy collection station according to claim 3, characterized in that: The asynchronous machine control model is expressed as: In the formula, in, , , , , , , , , , , and Respectively represent the phase angle, angular frequency, inertia, damping coefficient, active power, active power reference value, power limit, DC voltage, DC voltage reference value, DC voltage deviation control value, control ratio and control integral coefficient of the i-th non-synchronous machine power supply; Indicates the reference frequency.

5. The transient stability analysis method of a new energy collection station according to claim 1, characterized in that: The step of analyzing the power angle characteristics of the fault condition between the power sources of the asynchronous machine according to the control model of the asynchronous machine of the new energy converter and the energy storage converter to obtain the corresponding fault power angle characteristic curve comprises: According to the asynchronous machine control model of the new energy converter and the energy storage converter, the asynchronous machine control model of the new energy converter is converted with the phase of the flexible DC converter station as the reference phase to obtain a new energy asynchronous control model; Based on the current source characteristics of the new energy unit and the energy storage device under fault conditions, the normal operating power model is transformed into a fault operating power model; The fault power angle characteristic curve is obtained according to the fault operation power model.

6. The transient stability analysis method of a new energy collection station according to claim 1, characterized in that: The transient stability index is expressed as: In the formula, in, and Represent the limit resection angle and limit resection time respectively; and Respectively represent the phase angle difference between the critical point of fault initiation and the critical point of fault recovery; Indicates the phase of the new energy unit relative to the flexible DC converter station; represents the equivalent inertia time constant of the system; Indicates the reference frequency; Indicates the active power reference value of the new energy unit; and Respectively represent the voltage amplitudes of the new energy unit and the energy storage device; Indicates the reactance value of the interconnection line between the new energy unit and the energy storage device; , and They respectively represent the reactance value to ground at the busbar of the new energy generating unit, the reactance value to ground at the busbar of the energy storage device, and the reactance value of the interconnection line between the new energy generating unit and the energy storage device under fault conditions; and represents a proportionality factor; and They represent the saturation current of the new energy converter and the energy storage converter respectively.

7. A transient stability analysis system for a new energy collection station, characterized in that: The transient stability analysis method for a new energy collection station according to claim 1, wherein the system comprises: A normal power model acquisition module is used to construct a power hybrid two-machine system, and analyze the operating principle of the power hybrid two-machine system to obtain a corresponding normal operating power model; the power hybrid two-machine system includes a new energy unit and an energy storage device connected by a tie line; the new energy unit and the energy storage device are connected to the power grid through the corresponding new energy converter and energy storage converter respectively; A fault power angle characteristic analysis module is used to construct the asynchronous machine control models of the new energy converter and the energy storage converter respectively, and perform the power angle characteristic analysis of the fault condition between the power sources of the asynchronous machine according to the asynchronous machine control models of the new energy converter and the energy storage converter to obtain the corresponding fault power angle characteristic curve; A transient stability index acquisition module, used to obtain a transient stability index under a fault condition based on the equal area rule according to the fault power angle characteristic curve and the normal power angle characteristic curve corresponding to the normal operating power model; the transient stability index includes a limit cut-off angle and a limit cut-off time; The transient stability analysis module is used to perform transient stability analysis of the collection station according to the transient stability index to obtain the corresponding transient stability evaluation result.

8. A computer device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 6 are implemented.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 6 are implemented.

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