New energy pooling station transient stability analysis method, system, equipment and medium

Abstract

The invention provides a new energy pooling station transient stability analysis method, system and equipment and a medium, and the method comprises the steps: carrying out the operation principle analysis of a constructed power mixed consumption two-machine system which comprises a new energy unit and an energy storage device, wherein the new energy unit and the energy storage device are connected through a connecting line, and obtaining a normal operation power model; according to the established asynchronous machine control model of the new energy converter, fault working condition power angle characteristic analysis is carried out to obtain a corresponding fault power angle characteristic curve, and according to the fault power angle characteristic curve and a normal power angle characteristic curve corresponding to a normal operation power model, the fault power angle characteristic curve is calculated; and obtaining transient stability indexes including a limit clearing angle and limit clearing time under a fault condition based on an equal area rule, and carrying out pooling station transient stability analysis according to the transient stability indexes to obtain a corresponding transient stability evaluation result. According to the method, the comprehensiveness and the reliability of transient stability analysis are effectively improved based on collaborative analysis of interaction influence among different asynchronous machine power supplies.

Description

Technical Field

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

[0002] The rich offshore wind energy resources have huge potential for power generation, which is of great practical significance for reducing dependence on traditional fossil energy. In view of the intermittent, volatile and random characteristics of offshore wind power, the deployment of energy storage inverters in the offshore wind power grid-connected new energy collection stations can effectively compensate for the safety and stability threats brought by the random fluctuations of wind energy to the power system. However, there are a large number of grid-connected converters in the offshore wind power grid-connected new energy collection stations, and in the power system dominated by synchronous machines, the synchronous machines rely on the real physical behavior of the rotor to achieve synchronization, while the non-synchronous machine power supply based on the converter 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 is to a certain extent determined by the power control method and control parameters.

[0003] The existing transient stability analysis of new energy collection stations mainly focuses on the study of transient stability issues after a single non-synchronous power source is connected to the grid, and does not involve a comprehensive coordinated analysis of the interaction between different non-synchronous power sources from a global perspective. The transient stability of new energy collection stations with non-synchronous machine interaction scenarios between new energy (grid-connected) converters and energy storage non-synchronous power sources will inevitably be affected by the coordination between different non-synchronous power sources; that is, the existing transient stability analysis of new energy collection stations cannot effectively guarantee the comprehensiveness and reliability of transient stability analysis under power mixed absorption conditions (part of the power of new energy is used to meet the needs of the receiving 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 targeting a power mixed consumption scenario in which excess power generation of new energy units leads to electricity storage in an energy storage device, a simplified model of two machines in a new energy collection station is constructed, and control models based on different converters are constructed. In combination with the interaction characteristics between asynchronous machine sources, the power angle characteristic curves between the grid-connected converter for new energy grid connection and the grid-connected asynchronous machine source for energy storage device operation are analyzed, and the equal area rule is used to calculate the limit resection angle and the limit resection time for transient stability analysis of the new energy collection station, thereby realizing a collaborative steady-state analysis based on the interaction between different asynchronous machine sources, and effectively improving the comprehensiveness and reliability of transient stability analysis of the new energy collection station.

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

[0006] In a first aspect, an embodiment of the present invention provides a method for transient stability analysis of a new energy collection station, the method comprising 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; The transient stability analysis of the collection station is performed according to the transient stability index to obtain the corresponding transient stability evaluation result.

[0007] Furthermore, the normal operation 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.

[0008] Furthermore, the new energy converter and the energy storage converter are both grid-type converters; and 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, a corresponding asynchronous machine control model is constructed based on the virtual synchronous control principle.

[0009] Furthermore, 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.

[0010] Further, the step of performing power angle characteristic analysis of the fault condition between power sources of the asynchronous machine according to the asynchronous machine control model of the new energy converter and the energy storage converter to obtain the corresponding fault power angle characteristic curve includes: 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.

[0011] Furthermore, 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.

[0012] Furthermore, 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.

[0013] In a second aspect, an embodiment of the present invention provides a transient stability analysis system for a new energy collection station, the system comprising: 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.

[0014] In a third aspect, an embodiment of the present invention further provides a computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the above method when executing the computer program.

[0015] In a fourth aspect, an embodiment of the present invention further provides a computer-readable storage medium having a computer program stored thereon, wherein the computer program implements the steps of the above method when executed by a processor.

[0016] The present invention provides a method, system, computer equipment and storage medium for transient stability analysis of a new energy collection station. The method is used to construct a power hybrid two-machine system including a new energy unit and an energy storage device connected by a connecting 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 operation principle of the power hybrid 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 the power angle characteristics of the fault condition are analyzed according to the non-synchronous machine control model of the new energy converter to obtain the corresponding fault power angle characteristic curve, the transient stability indicators including the limit cut-off angle and the limit cut-off time under the fault condition are obtained based on the equal area law 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 performed according to the transient stability indicator to obtain the corresponding transient stability evaluation result. Compared with the existing technology, the transient stability analysis method of the new energy collection station can realize the collaborative steady-state analysis based on the interaction between different non-synchronous power sources, effectively improve the comprehensiveness and reliability of the transient stability analysis of the new energy collection station, and thus provide reliable guarantee for the safe and stable operation of the power system. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic flow chart of a transient stability analysis method for a new energy collection station in an embodiment of the present invention; Figure 2 2 is a schematic diagram of the structure of a two-machine power hybrid consumption system according to an embodiment of the present invention; Figure 3 It is a schematic diagram of a normal power angle characteristic curve and a fault power angle characteristic curve in the power angle characteristic analysis in an embodiment of the present invention; Figure 4 is a schematic diagram of a test system with a voltage level of 220 kV in an embodiment of the present invention; Figure 5 is based on Figure 2 Schematic diagram of converter power variation obtained by the test system through transient simulation analysis of situation 1; Figure 6 is based on Figure 2 Schematic diagram of converter voltage variation obtained by the test system through transient simulation analysis of situation 1; Figure 7 is based on Figure 2 Schematic diagram of converter power variation obtained by the test system through transient simulation analysis of situation 2; Figure 8 is based on Figure 2 Schematic diagram of converter voltage variation obtained by the test system through transient simulation analysis of situation 2; Fig. 9 It is a structural schematic diagram of a transient stability analysis system for a new energy collection station in an embodiment of the present invention; Fig.10 It is a diagram of the internal structure of a computer device in an embodiment of the present invention. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical scheme and beneficial effects of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. Obviously, the embodiments described below are part of the embodiments of the present invention and are only used to illustrate the present invention, but are not used to limit the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] The transient stability analysis method of the new energy collection station provided by the present invention can be understood as the existing transient stability analysis of the new energy collection station does not involve a comprehensive collaborative analysis of the interaction between different non-synchronous machine sources from a global perspective, and cannot guarantee the comprehensiveness and reliability of the transient stability analysis. Instead, a transient stability analysis method of the new energy collection station is proposed that considers the interaction between the new energy units and the energy storage device in the power hybrid consumption scenario. The following embodiments will explain the transient stability analysis method of the new energy collection station of the present invention in detail.

[0020] In one embodiment, Figure 1 As shown, a transient stability analysis method for a new energy collection station is provided, comprising the following steps: S11. 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; wherein the power hybrid two-machine system can be understood as a simplified system of a new energy collection station with only one new energy grid-connected converter and an energy storage converter designed for an operating scenario in which part of the output power of the offshore wind power new energy unit is used to meet the needs of the receiving power grid and the remaining power is stored in the energy storage device; Figure 2 As shown, the power hybrid consumption two-machine system 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 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) respectively; it should be noted that, Figure 2 The figure shows the power mixed consumption in the two-machine system and They are the voltage phasors at the new energy unit (power source 1) and the energy storage device (power source 2) respectively; and Respectively represent the reactance to ground at the busbars at the two power supply ends; represents the reactance of the tie line between the two power sources, and assumes that the tie line resistance and capacitance can be ignored; and They respectively represent the active power and reactive power transmitted from power source 1 to power source 2 via the tie line; and Respectively and The amplitude of .

[0021] based on Figure 2 The system structure shown in the figure analyzes the operating principle of the power mixed consumption two-machine system, and it is easy to obtain the active power exchanged on the interconnection line of the power mixed consumption two-machine system. (Take machine 2 as the reference node, the phase angle is 0, and ignore the line resistance R=0) as shown in formula (1): (1) 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.

[0022] At the same time, the active power output by the new energy unit (power source 1) and the energy storage device (power source 2) meets the following requirements: (2) in, and They respectively represent the active power output by the new energy units and the energy storage device.

[0023] Since equations (1) and (2) are the normal operating power expressions of the power hybrid absorption two-machine system obtained without considering the fault condition scenario, the required normal operating power model can be obtained by combining the two, and based on this model, the power angle characteristic curve of the new energy collection station under normal operating conditions can be obtained.

[0024] S12. Construct the asynchronous machine control models of the new energy converter and the energy storage converter respectively, and analyze the power angle characteristics of the fault condition 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 curve; wherein, the new energy converter and the energy storage converter are both grid-type converters based on universal adaptability considerations, and the virtual synchronous control based on the asynchronous machine power supply 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 an asynchronous motor model for the scenario of virtual synchronous control of the grid-type converter. Specifically, the steps of constructing the asynchronous machine control models of the new energy converter and the energy storage converter respectively include: According to the DC voltage deviation of the new energy generator set and the energy storage device, respectively, based on the preset limiting rule, the corresponding active power reference value of the non-synchronous machine power supply is generated; wherein, 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 rule can be understood as setting a correction coefficient based on the preset power limit and control ratio and control integral coefficient to correct the DC voltage deviation to obtain a DC voltage deviation control value; the corresponding non-synchronous machine active power reference value is expressed as: (3) (4) in, , , , , , and They respectively represent the active power reference value, power limit, DC voltage, DC voltage reference value, DC voltage deviation control value, control proportion and control integral coefficient of the i-th non-synchronous power supply.

[0025] According to the active power reference values ​​of the non-synchronous power sources of the new energy generator set and the energy storage device, a corresponding non-synchronous machine control model is constructed based on the virtual synchronous control principle; wherein the non-synchronous machine control model is expressed as: (5) in, , , , , , They represent the phase angle, angular frequency, inertia, damping coefficient, active power and active power reference value of the i-th non-synchronous power source respectively. When i=1, it represents the non-synchronous machine control model of the new energy converter, and when i=2, it represents the non-synchronous machine control model of the energy storage converter. Indicates the reference frequency.

[0026] After the asynchronous machine control models of the new energy converter and the energy storage converter are obtained 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 performed based on the control models; specifically, the step of 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 includes: According to the non-synchronous machine control model of the new energy converter and the energy storage converter, the non-synchronous 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 non-synchronous control model; wherein the new energy non-synchronous control model is a converter frequency control model modified based on the synchronous generator rotor motion equation with the flexible DC as the phase reference; since the new energy converter and the energy storage converter are connected in series, the power shortage ΔP is shared by the two converters, ΔP respectively 1 and ΔP 2 (ΔP=ΔP 1 +ΔP 2 ), and ΔP 1 Frequency deviation across renewable energy converters for: (6) In the formula, and They represent the inertia and damping coefficient of the new energy converter respectively.

[0027] ΔP2 frequency deviation caused by passing through the energy storage converter for: (7) In the formula, and represent the inertia and damping coefficient of the energy storage converter respectively.

[0028] Based on the condition of unified system frequency ( ), and the damping coefficient is ignored and We can get: (8) In the formula, Indicates the system frequency.

[0029] Combined with formula (9), we can get formula (11): (9) In the formula, Represents the system equivalent inertia time constant.

[0030] Based on the above derivation, the new energy asynchronous control model can be expressed as: (10) In the formula, (11) in, Indicates the frequency difference between the new energy unit and the energy storage device; Indicates 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 They represent the active power and active power reference value of the new energy unit respectively; Indicates the active power output by the new energy unit.

[0031] 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 characteristics can be understood as the current reaching the saturation value (maximum value) under fault conditions; at this time, the voltage of the new energy unit is , and the voltage at the busbar of the energy storage device is similarly , then the fault operation power model can be expressed as: (12) in, , and They 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 interconnection line between the new energy unit and the energy storage device under fault conditions; , 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; Indicates the phase of the new energy unit relative to the flexible DC converter station; and They represent the saturation current of the new energy converter and the energy storage converter respectively.

[0032] Formula (12) can reflect the active power transmitted by the interconnection line between the new energy unit and the energy storage device under the short-circuit fault condition: The relationship between the phase of the new energy unit and the flexible DC converter station.

[0033] 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, such as Figure 3 Shown as the blue curve in the middle.

[0034] S13. 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; wherein the normal power angle characteristic curve can be understood as a curve of the relationship between the active power and the power angle of the new energy collection station under normal operating conditions, which can be obtained based on the normal operating power model shown in equations (1)-(2), as follows: Figure 3 As shown by the red curve in the figure; Figure 3 As shown in the figure, 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 is constant, and the asynchronous machine control model shown in equation (5) is satisfied. At the same time, if the power balance requirement is taken , then in the transient process of hundreds of milliseconds, the frequency deviation of the non-synchronous machine power supply is small, and the frequency change is mainly affected by the unbalanced power. It is approximately considered that the damping effect can be ignored.

[0035] In order to ensure the efficiency and reliability of transient stability analysis, this embodiment preferably obtains the transient stability evaluation index of the new energy collection station under fault conditions based on the equal area rule; specifically, the step of obtaining the transient stability index under fault conditions based on the equal area rule includes: Based on the power balance analysis between asynchronous machine power sources, the angular frequency difference model between asynchronous machine power sources under fault conditions and the fault duration model are constructed; wherein, the angular frequency difference model between asynchronous machine power sources under fault conditions can be understood as the fault duration reaching The relationship between the angular frequency difference and phase angle difference between the asynchronous machine power supplies is expressed as: (13) 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; represents the active power transmitted on the interconnection line between the new energy unit and the energy storage device under fault conditions, as shown in formula (8); 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 system equivalent inertia time constant.

[0036] To simplify the formula, we can use: (14) in, represents a proportionality factor; and They represent the saturation current of the new energy converter and the energy storage converter respectively.

[0037] Based on formula (14), formula (9) can be transformed into: (15) In the formula, represents a proportional coefficient, as shown in formula (14).

[0038] Similarly, the phase angle difference of the non-synchronous machine power supply under the fault condition can be obtained from the beginning of the fault condition. becomes The required duration, that is, the fault duration model is expressed as: (16) in, Indicates the duration of the fault condition The 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.

[0039] Similarly, based on formula (14), formula (16) can be simplified to: (17) in, represents a proportional coefficient, as shown in formula (14).

[0040] 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, the acceleration area and the deceleration area are calculated; wherein the acceleration area 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 deceleration area 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 acceleration area and the deceleration area is as follows: based on Figure 3 The fault power angle characteristic curve shown in FIG. 1 and the normal power angle characteristic curve shown in FIG. 1 are combined with the angular frequency difference model between the power sources of the non-synchronous machine under the fault condition and the fault duration model shown in equations (15) and (17) to analyze the fault start point and the fault recovery point. That is, When it runs at point A, it corresponds to the normal state, the angular frequency difference between the two power supplies is 0, and there is ,and When a short circuit occurs, the system enters a fault condition, which causes the system to switch to the state corresponding to point B. Subsequently, due to , the system state will move right along curve 2, which is called "acceleration". Obviously, there must be a fault removal point on curve 2. Assuming point C is the fault removal point, at this moment the fault is cleared and the system returns to normal working condition (point E corresponding to curve 1), the corresponding area S ABCD is the acceleration area; then, due to , the system state will move rightward along curve 1 from point E, which is called "deceleration". When the system reaches the operating point F, it enters the critical state of fault recovery, corresponding to the available area S DEF is the deceleration area. It should be noted that according to the equal area law, if the area S ABCD Smaller than area S DEF , it can be considered that the system can maintain transient stability; otherwise, it can be considered that the system has the risk of instability.

[0041] The critical resection phase angle difference and the critical resection time when the acceleration area is equal to the deceleration area are obtained, and the transient stability index is obtained according to the critical resection phase angle difference and the critical resection time; wherein, the critical resection phase angle difference and the critical resection time can be understood as the phase angle difference and the fault duration between the two power supplies corresponding to the critical resection point of the fault on curve 2 (the system can maintain transient stability only if the fault is cleared before reaching this point). The corresponding calculation method can be implemented with reference to the existing equal area method, which will not be described in detail here; the obtained critical resection phase angle difference and the critical resection time can be used as the limit resection angle and the limit resection time in the transient stability index respectively, and the corresponding transient stability index is expressed as: (18) 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.

[0042] S14. Perform transient stability analysis on the collection station according to the transient stability index to obtain corresponding transient stability assessment results; wherein, the process of obtaining the transient stability assessment results can be understood as comparing the obtained actual resection angle and actual fault resection time with the polar resection angle and limit resection time obtained above, respectively. If the actual fault resection time is less than the limit resection time and the actual resection angle is less than the limit resection angle, it is considered that the system can maintain transient stability, otherwise it cannot maintain transient stability, and the final transient stability assessment result is obtained based on the actual analysis situation.

[0043] The embodiment of the present invention constructs a power hybrid 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, analyzes the operation principle of the power hybrid two-machine system to obtain a corresponding normal operating power model, and constructs non-synchronous machine control models of the new energy converter and the energy storage converter respectively. After performing a fault condition power angle characteristic analysis according to the non-synchronous machine control model of the new energy converter to obtain a 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, the equal area law is used to obtain The transient stability indicators including the limit cut-off angle and the limit cut-off time under fault conditions, as well as the scheme for performing transient stability analysis of the collection station according to the transient stability indicators to obtain the corresponding transient stability assessment results, effectively solves the application defects that the existing transient stability analysis of new energy collection stations does not involve comprehensive collaborative analysis of the interaction between different non-synchronous power sources from a global perspective, and cannot ensure the comprehensiveness and reliability of the transient stability analysis. It can realize collaborative steady-state analysis based on the interaction between different non-synchronous power sources, effectively improve the comprehensiveness and reliability of the transient stability analysis of the new energy collection station, and thus provide reliable guarantee for the safe and stable operation of the power system.

[0044] In order to verify the effectiveness of the transient stability analysis method for the new energy collection station proposed in the present invention, this embodiment constructs a Figure 4 The test system with a voltage level of 220 kV is used as an example for simulation comparison experiments; the system contains two new energy units that use grid-type converters, and a storage power station that also uses a grid-type converter. In the scenario where new energy power is generated in large quantities, the energy storage power station is used to absorb the new energy power. In addition, assuming Figure 4 The three grid-type power sources in the test are all controlled by power synchronization; the main parameters of the corresponding test system are shown in Table 1.

[0045] Table 1 Main parameters of the test system exist Figure 4 And in Table 1, is the reference value of active power output by power supply j, j=1, 2, 3; Sj is the capacity of power supply j; is the AC voltage reference value of the power supply j grid side; L Tj is the inductance of the grid-connected transformer of power source j. In this test system, the inductances of the three grid-connected transformers are equal; L j-k is the inductance of the tie line between busbar j and busbar k; ω0 is the rated angular frequency of the system; H sj is the inertia time constant of the grid-type power source j.

[0046] For the above test system, simulations were performed in the electromechanical transient analysis software PSS / E and the electromagnetic transient simulation software PSCAD / EMTDC. The simulation conditions and results are shown in Table 2: 1) Case 1: A three-phase metallic short circuit fault occurs near bus 4 at t=0.5s, and the fault is cleared at t=0.87s; 2) Case 2: A three-phase metallic short circuit fault occurred near bus 4 at t=0.5s, and the fault was cleared at t=0.88s.

[0047] Table 2 Comparison of PSS / E and PSCAD simulation results According to the comparison in Table 2, the electromechanical transient simulation results are basically consistent with the electromagnetic transient simulation results. Figure 5 and Figure 6 The power changes and voltage changes of the three converters in case 1 are shown respectively; Figure 7 and Figure 8 The power changes and voltage changes of the three converters under case 2 are shown respectively. According to cases 1 and 2, under the original conditions, the critical removal time of the fault is about 0.37s. It can be seen that the above simulation results are basically consistent with the critical removal time obtained by the transient stability analysis method of the new energy collection station proposed in the present invention. The analysis results of the present invention are in line with reality and have high accuracy.

[0048] It should be noted that although the steps in the above flowchart are shown in sequence according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise specified in this document, there is no strict order restriction for the execution of these steps, and these steps can be executed in other orders.

[0049] In one embodiment, Fig. 9 As shown, a transient stability analysis system for a new energy collection station is provided, the system comprising: Normal power model acquisition module 1 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 2 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 3 is 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 4 is used to perform transient stability analysis of the collection station according to the transient stability index to obtain a corresponding transient stability evaluation result.

[0050] For the specific limitations of the transient stability analysis system for the new energy collection station, please refer to the limitations of the transient stability analysis method for the new energy collection station mentioned above. The corresponding technical effects can also be equivalently obtained, which will not be repeated here. Each module in the above-mentioned transient stability analysis system for the new energy collection station can be implemented in whole or in part through software, hardware and a combination thereof. The above-mentioned modules can be embedded in or independent of the processor in the computer device in the form of hardware, or can be stored in the memory of the computer device in the form of software, so that the processor can call and execute the operations corresponding to the above modules.

[0051] Fig.10 FIG. 1 shows an internal structure diagram of a computer device in an embodiment, and the computer device may specifically be a terminal or a server. Fig.10 As 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. When the computer program is executed by the processor, a transient stability analysis method for a new energy collection station is implemented. The display screen of the computer device can be a liquid crystal display screen or an electronic ink display screen, and the input device of the computer device can be a touch layer covered on the display screen, or a button, trackball or touchpad set on the computer device housing, or an external keyboard, touchpad or mouse, etc.

[0052] It can be understood by those skilled in the art that Fig.10 The structure shown in the figure is only a block diagram of a part of the structure 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 less components than those shown in the figure, or combine certain components, or have the same component arrangement.

[0053] In one embodiment, a computer device is provided, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the steps of the above method are implemented when the processor executes the computer program.

[0054] In one embodiment, a computer-readable storage medium is provided, on which a computer program is stored, and when the computer program is executed by a processor, the steps of the above method are implemented.

[0055] In summary, an embodiment of the present invention provides a method and system for transient stability analysis of a new energy collection station. The method for transient stability analysis of a new energy collection station realizes the construction of a power hybrid 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, and the operation principle of the power hybrid two-machine system is analyzed to obtain a corresponding normal operation power model, and the non-synchronous machine control models of the new energy converter and the energy storage converter are respectively constructed, and the fault condition power angle characteristic analysis is performed according to the non-synchronous machine control model of the new energy converter to obtain the corresponding fault power angle characteristic curve, and 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 including the limit cut-off angle and the limit cut-off time under the fault condition is obtained based on the equal area rule, and the transient stability analysis of the collection station is performed according to the transient stability index to obtain the corresponding transient stability evaluation result. The technical solution, 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 reliable guarantee for the safe and stable operation of the power system.

[0056] Each embodiment in this specification is described in a progressive manner, and the same or similar parts of each embodiment can be directly referred to each other, and 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 be referred to the partial description of the method embodiment. It should be noted that the technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, all possible combinations of the technical features in the above-mentioned embodiments are not described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0057] The above-mentioned embodiments only express several preferred implementation modes of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this technical field, several improvements and substitutions can be made without departing from the technical principle of the present invention, and these improvements and substitutions should also be regarded as the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be based on 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; The transient stability analysis of the collection station is performed according to the transient stability index to obtain the corresponding transient stability evaluation result.

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, a corresponding asynchronous machine control model is 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 step of obtaining the transient stability index under the fault condition based on the equal area rule comprises: 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.

7. The transient stability analysis method of a new energy collection station according to claim 6, 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.

8. A transient stability analysis system for a new energy collection station, characterized in that: 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.

9. 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 7 are implemented.

10. 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 7 are implemented.

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