New energy multi-station cooperative fault ride-through control method

Abstract

The invention discloses a new energy multi-station cooperative fault ride-through control method, and belongs to the technical field of power supply. The invention discloses a new energy multi-station cooperative fault ride-through control method, and the method comprises the steps: analyzing the interaction influence between stations; establishing a current and voltage interaction influence mathematical model of each new energy station under the fault condition; solving positive sequence active current and positive sequence reactive current; solving a proportionality coefficient of the active current and the reactive current constrained by the current amplitude limiting value; providing an output current priority discrimination method under the fault condition; determining a current limiting the fluctuation of the active power; a virtual node control strategy is combined, and an active current and reactive current local optimal ratio is introduced; introducing an optimal proportion calculation method into a virtual node control ring; and each station completes fault ride-through according to the calculated current instruction value. By adopting the new energy multi-station cooperative fault ride-through control method provided by the invention, the problems that the voltage is out of limit during the fault period of the new energy multi-station grid-connected system and the optimal support is difficult to realize are solved.

Description

Technical Field

[0001] The present invention relates to the field of power supply technology, and in particular to a new energy multi-station coordinated fault ride-through control method. Background Art

[0002] New energy stations are often geographically dispersed and experience significant fluctuations in output characteristics. In practice, multiple stations are often connected to the grid via aggregated lines. The increasing prevalence of large numbers of stations connected to weak grids via aggregated lines presents unique challenges to the safe and stable operation of the power grid.

[0003] Weak power grids inherently have low inertia and weak anti-disturbance capabilities. New energy generators are constructed using power electronic devices, and the integration of a large number of these devices gradually weakens the power grid. When a fault occurs in a weak power grid, each new energy generator is required to maximize its voltage support capabilities to ensure the system can safely ride through the fault. Asymmetric faults are the most common type of fault in power grids. When they occur in a weak power grid, the voltage support capacity of some new energy stations is insufficient, which may cause a significant drop in the voltage at the grid connection point, or even trigger serious fault conditions such as a chain reaction. At other stations, excessive reactive power injection can cause voltage overshoots, which also endangers system safety.

[0004] Therefore, it is particularly important to give full play to the voltage support capabilities of various new energy stations in the weak power grid and ensure the safe operation of the system under the background of weak power grid. Summary of the Invention

[0005] The purpose of the present invention is to provide a new energy multi-station coordinated fault ride-through control method to solve the problem of voltage exceeding the limit during a fault in the new energy multi-station grid-connected system and difficulty in achieving optimal support.

[0006] To achieve the above objectives, the present invention provides a new energy multi-station coordinated fault ride-through control method, comprising the following steps: S1. Consider the topological structure of multiple new energy stations and analyze the interaction between stations; S2. Establish a mathematical model of the interaction between current and voltage of each renewable energy station under fault conditions; S3. Determine the optimal ratio of positive-sequence active current and positive-sequence reactive current based on the mathematical model of the interaction between current and voltage at the new energy station; S4. Combined with the current limit of the new energy station, solve the proportional coefficient of the optimal ratio of active current and reactive current constrained by the current limit value; S5. Propose a collaborative determination method for output current priority under fault conditions of different new energy stations; S6. Determine the current for limiting active power fluctuations based on the active power fluctuation limits of the new energy station; S7. Combined with the virtual node control strategy, the local optimal ratio of active current and reactive current and the collaborative priority control method are introduced; S8. Introduce the optimal ratio calculation method into the virtual node control loop to obtain the overall calculation formula; S9. Each station sends the command value to the units within the station based on the calculated current command value to complete the fault ride-through.

[0007] Preferably, in said S1, the specific analysis process of the interaction impact between stations is: simplifying the topology of the new energy multi-station aggregation access to the weak power grid system into the mutual impact of the impedance on the new energy station side and the impedance from the public collection point to the fault point; Among them, the impedance of the new energy station side is the impedance from each new energy station to the public collection point. i The impedance from each new energy station to the public collection point Z i for Z i = R i + uX i ， Where, R i For the i The active loss resistance component from each new energy station to the public collection point, X i For the i The reactive reactance component from each new energy station to the public collection point, u is an imaginary unit; the impedance from the common collection point to the fault point Z S for Z S = R S + uX S , where R S is the active loss resistance component from the public collection point to the fault point, X S It is the reactive reactance component from the public collection point to the fault point; The influence of the current and voltage output of each new energy station fault is realized through the above two types of impedance. The interaction between stations depends on R i 、 X i 、 R S 、 X S .

[0008] Preferably, in S2, the mathematical model of the interaction between current and voltage of the new energy station is: ; Where, For the i The positive sequence voltage of the grid connection point of each new energy station, Input the positive sequence voltage of the new energy station to the system, For the i The positive sequence current output by each new energy station, For the j Positive sequence current output by each new energy station; For the i Negative sequence voltage of each new energy station grid connection point, Input the negative sequence voltage of the new energy station to the system, For the i The negative sequence current output by each new energy station, For the j The negative sequence current output by each new energy station, n is the total number of energy stations in the system.

[0009] Preferably, in S3, the specific process of solving the optimal ratio of active power and reactive power according to the mathematical model of the interaction between current and voltage of the new energy station is: S31. The output current of the new energy station includes positive-sequence active current and positive-sequence reactive current, and the proportional relationship is: ; Where, is the positive sequence active current, is the positive sequence reactive current, k is the proportionality coefficient; S32. During a fault, the positive sequence voltage is optimally supported. The relationship between the positive sequence voltage at the grid connection point and the output current of the new energy station is: ; Where, is the positive sequence voltage at the grid connection point, R is the resistance component of the collection line impedance, X is the reactance component of the collection line impedance; Taking the derivative of the positive sequence voltage at the grid connection point, we get: ; S33. The positive sequence reactive current that enables the grid connection point positive sequence voltage to obtain optimal support is: .

[0010] Preferably, in said S4, the specific process of solving the optimal ratio coefficient of active current and reactive current constrained by the current limit value is: No. i The constraints satisfied by the positive sequence active current and positive sequence reactive current output by each new energy station are: ; Where, For the i The positive sequence active current of each new energy station, For the i Positive sequence reactive current of each new energy station, is the current limit value; According to the proportional relationship between the positive sequence active current and the positive sequence reactive current, we can get: ; Substitute the above formula into the positive sequence reactive current solution formula in S33 to obtain: .

[0011] Preferably, in said S5, the method for collaboratively determining the output current priority under fault conditions of different new energy stations is specifically as follows: S51, the system n Conduct voltage detection on each new energy station and divide the new energy stations into different queues according to the degree of voltage drop; S52: For new energy stations 1 to new energy stations where the voltage drops below 0.6 pu , No. i New energy stations meet , then it is in the high priority output station queue H Z Otherwise, it is in the low priority output station queue L Z ; For voltage drops above 0.6 pu New energy stations, j New energy stations meet , For the j The impedance from the new energy station to the public collection point is the second highest priority output station queue H. F Otherwise, it is in the second lowest priority output station queue L F ; S53. Calculate the optimal proportional coefficient of each new energy station k , the calculation sequence and the current command value setting sequence are: H Z >H F >L Z >L F .

[0012] Preferably, in S6, the current setting method for limiting active power fluctuation is specifically: For the i For each new energy station, the calculation formula for the active power fluctuation amplitude is: ; Where, For the i The active power fluctuation amplitude of each new energy station, For the i Negative sequence voltage of each new energy station grid connection point, For the i Positive sequence voltage of each new energy station grid connection point; For the i Negative sequence reactive current of new energy stations, For the i Negative sequence active current of each new energy station; In order to minimize the active power fluctuation, the square term on the right side of the formula is set to 0, and we get: .

[0013] Preferably, in said S7, The virtual node control equation is: ; Where, is the virtual node positive sequence voltage, is the positive sequence voltage of the grid connection point of the new energy station, is the virtual resistance component, is the positive sequence active current, is the virtual reactance component, is the positive sequence reactive current, is the virtual node negative sequence voltage, is the negative sequence voltage of the grid connection point of the new energy station, is the negative sequence active current, is the negative sequence reactive current; Prioritize the positive sequence reactive current and ignore the positive sequence active current in the formula. The positive sequence reactive current reference value and the positive sequence active current reference value are: ; Where, is the positive sequence reactive current reference value, is the positive sequence voltage reference value, It is the positive sequence active current reference value.

[0014] Preferably, in S8, the overall calculation formula is: ; Where, is the negative sequence reactive current reference value; During the calculation process, all stations must meet the following constraints: ; Where, For the i Output of new energy stations Three-phase current, is the current limit value of the new energy station, For the i New energy stations and grid connection points Three-phase voltage, The upper limit of the voltage limit value of the new energy station, V set is the lower limit of the voltage limit value of the new energy station, For the i Output of new energy stations Three-phase power, It is the power fluctuation limit of new energy stations.

[0015] The advantages and positive effects of the new energy multi-station coordinated fault ride-through control method described in the present invention are: 1. The present invention realizes the coordinated fault ride-through control of multiple renewable energy stations based on the optimal ratio of active and reactive power. It has small calculation amount, fast calculation speed and high calculation accuracy, and is easy to apply and promote in actual engineering.

[0016] 2. By solving the optimal ratio of active and reactive currents and combining strategies such as current limiting coefficient and priority collaborative judgment, the present invention can achieve optimal support for new energy stations with severe voltage drops, effectively avoid large voltage drops and over-limit problems, and control the voltage of each station's grid connection point within a reasonable range.

[0017] 3. The present invention proposes a collaborative judgment method for the fault output current priority of different new energy stations, combined with a current setting method for active power fluctuation limitation, to achieve efficient collaborative control among multiple stations, avoiding control confusion caused by different voltage drop levels at each station.

[0018] 4. The present invention uses a current setting method to limit active power fluctuations, which can suppress the double-frequency oscillation of the station's output active power during asymmetric voltage drops, avoid the impact of the DC bus voltage's same-frequency oscillation on the life of the capacitor, and extend the service life of the equipment.

[0019] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1is a flow chart of the present invention; Figure 2 This is the basic topological structure diagram of the new energy multi-station aggregation access to the weak power grid of the present invention; Figure 3 The voltage at each station's grid connection point under the existing national standard control method; Figure 4 It is the grid connection point voltage of each station under the control method of the present invention. DETAILED DESCRIPTION

[0021] In this application, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs. In the event of any inconsistency, the meaning described in this specification or the meaning derived from the contents recorded in this specification shall prevail. In addition, the terms used herein are only for the purpose of describing the embodiments of this application and are not intended to limit this application.

[0022] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0023] like Figure 1 As shown, a new energy multi-station coordinated fault ride-through control method includes the following steps: S1. Consider the topological structure of multiple new energy stations and analyze the interaction between stations.

[0024] The impedance of the new energy station side is the impedance from each new energy station to the public collection point. i The impedance from each new energy station to the public collection point Z i for Z i = R i + uX i ， Where, R i For the i The active loss resistance component from each new energy station to the public collection point, X i For the i The reactive reactance component from each new energy station to the public collection point, u The impedance from the common collection point to the fault point is Z S for Z S = R S + uX S , where R Sis the active loss resistance component from the public collection point to the fault point, X S It is the reactive reactance component from the public collection point to the fault point.

[0025] The influence of the current and voltage output of each new energy station fault is realized through the above two types of impedance. The interaction between stations depends on R i 、 X i 、 R S 、 X S .

[0026] S2. Establish a mathematical model of the interaction between current and voltage of each renewable energy station under fault conditions.

[0027] The mathematical model of the interaction between current and voltage at new energy stations is: ; Where, For the i The positive sequence voltage of the grid connection point of each new energy station, Input the positive sequence voltage of the new energy station to the system, For the i The positive sequence current output by each new energy station, For the j Positive sequence current output by each new energy station; For the i Negative sequence voltage of each new energy station grid connection point, Input the negative sequence voltage of the new energy station to the system, For the i The negative sequence current output by each new energy station, For the j The negative sequence current output by each new energy station, n is the total number of energy stations in the system.

[0028] It can be seen that for the i The positive and negative sequence voltages of each station are due to the location of the fault point after the fault. Z S It cannot be obtained in real time. The interaction between stations is mainly realized through the output current and the impedance of the collection line between stations, that is, through I i and Z i to achieve.

[0029] S3. Determine the optimal ratio of positive-sequence active current and positive-sequence reactive current based on the mathematical model of the interaction between current and voltage at new energy stations.

[0030] The specific process is: S31. For a single new energy station, based on the above analysis, its output current is related to the grid connection point voltage through the impedance of the collection line. Since the station output current can be divided into positive sequence active current and positive sequence reactive current, their outputs meet a certain proportional relationship: ; Where, is the positive sequence active current, is the positive sequence reactive current, k is the proportional coefficient.

[0031] S32. During a fault, the positive sequence voltage is optimally supported. The relationship between the positive sequence voltage at the grid connection point and the output current of the new energy station is: ; Where, is the positive sequence voltage at the grid connection point, R is the resistance component of the collection line impedance, X is the reactance component of the collection line impedance; Since we hope to obtain the best possible voltage support effect, it can be assumed from the above formula that there is a certain functional relationship between the positive sequence voltage at the grid connection point and the positive sequence reactive current output by the station. By taking the derivative of the positive sequence voltage at the grid connection point, we can obtain: .

[0032] S33. Based on the above formula, the positive sequence reactive current that maximizes the positive sequence voltage support effect can be obtained as follows: .

[0033] S4. Combined with the current limit of the new energy station, solve the proportional coefficient of the optimal ratio of active current and reactive current constrained by the current limit value.

[0034] The specific process is: The above analysis has made it clear that the proportion of solutions during the fault period k However, in this process, only the best support effect of the grid connection point voltage is considered, and whether there is a risk of current exceeding the limit when each station outputs current, that is, the current limit value constraint, is not considered.

[0035] No. i The constraints satisfied by the positive sequence active current and positive sequence reactive current output by each new energy station are: ; Where, For the i The positive sequence active current of each new energy station, For the iPositive sequence reactive current of each new energy station, is the current limit value; According to the proportional relationship between the positive sequence active current and the positive sequence reactive current, we can get: ; Substituting the above formula into the positive sequence reactive current solution formula in S33, we can get the new energy station at this time i Obtain the optimal voltage support effect while meeting the current limit value constraint ratio k for: .

[0036] S5. A collaborative method for determining output current priority under fault conditions of different new energy stations is proposed.

[0037] During a fault, for a renewable energy multi-station grid-connected system, the voltage drop degree of each station is inconsistent. Stations with greater voltage drops need to be calculated and given current command values ​​first. This involves a priority coordination problem. The coordination method is as follows: S51, the system n Voltage detection is carried out on each new energy station, and the new energy stations are divided into different queues according to the degree of voltage drop.

[0038] S52: For new energy stations 1 to new energy stations where the voltage drops below 0.6 pu , No. i New energy stations meet , then it is in the high priority output station queue H Z On the contrary, if it satisfies , then it is in the low priority output station queue L Z .

[0039] For voltage drops above 0.6 pu New energy stations, j New energy stations meet , then it is in the second highest priority output station queue H F On the contrary, if it satisfies , For the j The impedance from the new energy station to the public collection point is located in the second lowest priority output station queue L F .

[0040] S53. Calculate the optimal proportional coefficient of each new energy station k , the calculation sequence and the current command value setting sequence are: H Z >H F >L Z >LF .

[0041] S6. Determine the current that limits active power fluctuations based on the active power fluctuation limits of new energy stations.

[0042] The current setting method for limiting active power fluctuation is as follows: During an asymmetric voltage drop, the station's output active power may oscillate at twice the frequency, causing the DC bus voltage to oscillate at the same frequency. This oscillation will significantly affect the life of the DC bus capacitor. Therefore, the station's output active power oscillation must be suppressed by appropriate means.

[0043] For the i For each new energy station, the calculation formula for the active power fluctuation amplitude is: ; Where, For the i The active power fluctuation amplitude of each new energy station, For the i Negative sequence voltage of each new energy station grid connection point, For the i Positive sequence voltage of each new energy station grid connection point; For the i Negative sequence reactive current of new energy stations, For the i Negative sequence active current of each new energy station; It can be seen that in order to minimize the active power fluctuation, the square term on the right side of the formula is set to 0. In this case, the relationship between the two currents is: .

[0044] Therefore, during a fault, the relationship between the positive-sequence reactive current and the negative-sequence reactive current output by the new energy station can be determined by the above formula. Based on this formula, the active power fluctuation amplitude can be limited during a fault.

[0045] S7. Combined with the virtual node control strategy, the local optimal ratio of active current and reactive current and the collaborative priority control method are introduced.

[0046] The virtual node control equation is: ; Where, is the virtual node positive sequence voltage, is the positive sequence voltage of the grid connection point of the new energy station, is the virtual resistance component, is the positive sequence active current, is the virtual reactance component, is the positive sequence reactive current, is the virtual node negative sequence voltage, is the negative sequence voltage of the grid connection point of the new energy station, is the negative sequence active current, is the negative sequence reactive current; Prioritize the positive sequence reactive current and ignore the positive sequence active current in the formula. The positive sequence reactive current reference value and the positive sequence active current reference value are: ; Where, is the positive sequence reactive current reference value, is the positive sequence voltage reference value, It is the positive sequence active current reference value.

[0047] S8. Introduce the optimal ratio calculation method into the virtual node control loop to obtain the overall calculation formula.

[0048] Combined with the above calculation steps, during the fault period, the calculations that each station should complete are as follows (the order of the formulas is the order of calculation): ; Where, is the negative sequence reactive current reference value; During the calculation process, all new energy stations must meet the following constraints: ; Where, For the i Output of new energy stations Three-phase current, is the current limit value of the new energy station, For the i New energy stations and grid connection points Three-phase voltage, The upper limit of the voltage limit value of the new energy station, V set is the lower limit of the voltage limit value of the new energy station, For the i Output of new energy stations Three-phase power, It is the power fluctuation limit of new energy stations.

[0049] Based on the output currents of high and low priority, the system calculates the output current of each renewable energy station and checks whether it exceeds the current limit. For stations that exceed the limit, the system re-determines the priority based on the previous iterative calculation value and performs the next calculation cycle.

[0050] S9. Each station sends the command value to the units within the station based on the calculated current command value to complete the fault ride-through.

[0051] In order to further illustrate the performance of the present invention, a detailed description is given in conjunction with an embodiment. Figure 2 The three-station grid connection example is shown in Figure 1. The specific system parameters are shown in Table 1.

[0052] Table 1 System parameters ; The fault occurred on the grid side in 1 second and lasted for 0.5 seconds. This paper uses the latest 2021 national standard for low voltage ride-through control for wind and solar power stations as a comparison.

[0053] After the fault occurs, the new energy station detects the fault and calculates its own priority as described in S5 above. After clarifying its own priority queue, the results are uniformly transmitted to the centralized control station. The centralized control station will first calculate the priority queue in queue H (H Z 、H F ) in the optimal proportional coefficient of each station. After the calculation is completed, the optimal proportional coefficient and voltage command value are uniformly sent to the closed-loop control structure of the present invention assembled in each station, and then the same method is used to calculate the number of stations in queue L (L Z 、L F ) and transmits the optimal proportional coefficient for each station to the corresponding control structure at each station. Each station's control system automatically adjusts its output active and reactive current command values ​​based on its own grid connection point voltage and command information (similar to an integral control process), gradually aligning its own voltage command value with the voltage command value issued by the centralized control station. During this process, the control structure ensures that current and power output do not exceed limits. Once the grid connection point voltage reaches the voltage command issued by the centralized control station, the output current is maintained unchanged, completing closed-loop coordinated control. After the fault is resolved, each station exits closed-loop control and adopts normal operating control.

[0054] In order to better illustrate the effect of the control method of the present invention, the control method of the present invention is compared with the effect of the existing national standard control method. Figure 3 、 Figure 4 As shown. It can be seen that under the existing national standard control method, the voltage of each phase of the new energy station 1 has dropped significantly, and the voltage of each phase of the new energy stations 2 and 3 has exceeded the limit to varying degrees. In the scenario where multiple new energy stations are connected to a weak power grid, this limit-crossing will cause great harm to the grid-connected operation of the new energy stations. After adopting the method proposed in the present invention, the voltage of each phase of the new energy station is controlled within a reasonable range, and the voltage support effect is good, and the optimal voltage support effect can be achieved within the voltage boundary, which reflects the superiority of the method of the present invention.

[0055] Therefore, the new energy multi-station collaborative fault ride-through control method described in the present invention can achieve optimal support for new energy stations with a deeper voltage drop. At the same time, it can effectively support the grid connection point voltage of the new energy multi-station while ensuring that it does not exceed the limit when the system has serious voltage exceeding the limit, solving the problem of voltage exceeding the limit during the fault of the new energy multi-station grid connection system and difficulty in achieving optimal support.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A new energy multi-station coordinated fault ride-through control method, characterized in that: The following steps are involved: S1. Consider the topological structure of multiple new energy stations and analyze the interaction between new energy stations; S2. Establish a mathematical model of the interaction between current and voltage of each renewable energy station under fault conditions; S3. Determine the optimal ratio of positive-sequence active current and positive-sequence reactive current based on the mathematical model of the interaction between current and voltage at the new energy station; S4. Combined with the current limit of the new energy station, solve the proportional coefficient of the optimal ratio of active current and reactive current constrained by the current limit value; S5. Propose a collaborative determination method for output current priority under fault conditions of different new energy stations; S6. Determine the current for limiting active power fluctuations based on the active power fluctuation limits of the new energy station; S7. Combined with the virtual node control strategy, the local optimal ratio of active current and reactive current and the collaborative priority control method are introduced; S8. Introduce the optimal ratio calculation method into the virtual node control loop to obtain the overall calculation formula; S9. Each station sends the command value to the units within the station based on the calculated current command value to complete the fault ride-through.

2. A new energy multi-station coordinated fault ride-through control method according to claim 1, characterized in that: In S1, the specific analysis process of the interaction between stations is as follows: the topology of the new energy multi-station aggregation and access to the weak power grid system is simplified to the mutual influence of the impedance on the new energy station side and the impedance from the public collection point to the fault point; Among them, the impedance of the new energy station side is the impedance from each new energy station to the public collection point. i The impedance from each new energy station to the public collection point Z i for Z i = R i + uX i ， Where, R i For the i The active loss resistance component from each new energy station to the public collection point, X i For the i The reactive reactance component from each new energy station to the public collection point, u is an imaginary unit; the impedance from the common collection point to the fault point Z S for Z S = R S + uX S , where R S is the active loss resistance component from the public collection point to the fault point, X S It is the reactive reactance component from the public collection point to the fault point; The influence of the current and voltage output by each new energy station is realized through the above two types of impedance. The interaction between new energy stations depends on R i 、 X i 、 R S 、 X S .

3. A new energy multi-station coordinated fault ride-through control method according to claim 2, characterized in that: In S2, the mathematical model of the interaction between current and voltage of the new energy station is: ； Where, For the i The positive sequence voltage of the grid connection point of each new energy station, Input the positive sequence voltage of the new energy station to the system, For the i The positive sequence current output by each new energy station, For the j Positive sequence current output by each new energy station; For the i Negative sequence voltage of each new energy station grid connection point, Input the negative sequence voltage of the new energy station to the system, For the i The negative sequence current output by each new energy station, For the j The negative sequence current output by each new energy station, n is the total number of energy stations in the system.

4. The new energy multi-station coordinated fault ride-through control method according to claim 3 is characterized by: In S3, the specific process of solving the optimal ratio of active power and reactive power based on the mathematical model of the interaction between current and voltage of the new energy station is as follows: S31. The output current of the new energy station includes positive-sequence active current and positive-sequence reactive current, and the proportional relationship is: ； Where, is the positive sequence active current, is the positive sequence reactive current, k is the proportionality coefficient; S32. During a fault, the positive sequence voltage is optimally supported. The relationship between the positive sequence voltage at the grid connection point and the output current of the new energy station is: ； Where, is the positive sequence voltage at the grid connection point, R is the resistance component of the collection line impedance, X is the reactance component of the collection line impedance; Taking the derivative of the positive sequence voltage at the grid connection point, we get: ； S33. The positive sequence reactive current that enables the grid connection point positive sequence voltage to obtain optimal support is: 。 5. A new energy multi-station coordinated fault ride-through control method according to claim 4, characterized in that: In S4, the specific process of solving the optimal ratio coefficient of active current and reactive current constrained by the current limit value is as follows: No. i The constraints satisfied by the positive sequence active current and positive sequence reactive current output by each new energy station are: ； Where, For the i The positive sequence active current of each new energy station, For the i Positive sequence reactive current of each new energy station, is the current limit value; According to the proportional relationship between the positive sequence active current and the positive sequence reactive current, we can get: ； Substitute the above formula into the positive sequence reactive current solution formula in S33 to obtain: 。 6. A new energy multi-station coordinated fault ride-through control method according to claim 5, characterized in that: In S5, the method for collaboratively determining the output current priority under different new energy station fault conditions is specifically as follows: S51, the system n Conduct voltage detection on each new energy station and divide the new energy stations into different queues according to the degree of voltage drop; S52: For new energy stations 1 to new energy stations where the voltage drops below 0.6 pu , No. i New energy stations meet , then it is in the high priority output station queue H Z Otherwise, it is in the low priority output station queue L Z ; For voltage drops above 0.6 pu New energy stations, j New energy stations meet , For the j The impedance from the new energy station to the public collection point is the second highest priority output station queue H. F Otherwise, it is in the second lowest priority output station queue L F ; S53. Calculate the optimal proportional coefficient of each new energy station k , the calculation sequence and the current command value setting sequence are: H Z >H F >L Z >L F .

7. A new energy multi-station coordinated fault ride-through control method according to claim 6, characterized in that: In S6, the current setting method for limiting active power fluctuation is specifically as follows: For the i For each new energy station, the calculation formula for the active power fluctuation amplitude is: ； Where, For the i The active power fluctuation amplitude of each new energy station, For the i Negative sequence voltage of each new energy station grid connection point, For the i Positive sequence voltage of each new energy station grid connection point; For the i Negative sequence reactive current of new energy stations, For the i Negative sequence active current of each new energy station; In order to minimize the active power fluctuation, the square term on the right side of the formula is set to 0, and we get: 。 8. A new energy multi-station coordinated fault ride-through control method according to claim 7, characterized in that: In said S7, The virtual node control equation is: ； Where, is the virtual node positive sequence voltage, is the positive sequence voltage of the grid connection point of the new energy station, is the virtual resistance component, is the positive sequence active current, is the virtual reactance component, is the positive sequence reactive current, is the virtual node negative sequence voltage, is the negative sequence voltage of the grid connection point of the new energy station, is the negative sequence active current, is the negative sequence reactive current; Prioritize the positive sequence reactive current and ignore the positive sequence active current in the formula. The positive sequence reactive current reference value and the positive sequence active current reference value are: ； Where, is the positive sequence reactive current reference value, is the positive sequence voltage reference value, It is the positive sequence active current reference value.

9. A new energy multi-station coordinated fault ride-through control method according to claim 8, characterized in that: In S8, the overall calculation formula is: ； Where, is the negative sequence reactive current reference value; During the calculation process, all stations must meet the following constraints: ； Where, For the i Output of new energy stations Three-phase current, is the current limit value of the new energy station, For the i New energy stations and grid connection points Three-phase voltage, The upper limit of the voltage limit value of the new energy station, V set is the lower limit of the voltage limit value of the new energy station, For the i Output of new energy stations Three-phase power, It is the power fluctuation limit of new energy stations.

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