New energy network tracking / constructing converter capacity configuration method based on power angle stability boundary

Abstract

The invention discloses a new energy tracking / networking converter capacity configuration method based on a power angle stability boundary, and the method comprises the steps: firstly, building a new energy sending end system simulation model containing a networking converter, and calculating a steady-state operation point of a system; then, carrying out dynamic equivalence on the network construction type converter and a synchronous generator to obtain equivalent machine parameters, and simplifying an original simulation system into an equivalent machine and a network following type new energy sending end system; deriving mechanical power and electromagnetic power of the equivalent machine before, during and after the fault to obtain a power angle characteristic curve of the equivalent machine; calculating the acceleration area and the maximum deceleration area of an equivalent machine under different proportions of the network construction type converter, and obtaining the proportion of the network construction type new energy under the stable critical power angle of the system by adopting a dichotomy method; simulation is carried out based on a PSASP platform, and the rationality of the proposed configuration principle is verified. According to the scheme provided by the invention, the network construction investment of the system can be reduced while the safety and stability of the system are ensured, and the admitting ability of the power grid to new energy is improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of power system safety and stability analysis and capacity configuration, and particularly relates to a new energy follow / network converter capacity configuration method based on a power angle stability boundary. BACKGROUND

[0002] With the overall promotion of the "double carbon" target, the installed capacity of wind power, photovoltaic and other new energy sources is showing explosive growth. Because new energy units are flexibly connected to the grid through power electronic devices, their strong fluctuation, weak inertia and low anti-disturbance characteristics pose new challenges to the safe and stable operation of the power system. New energy generation is generally connected to the grid through follow-network type converters, which track the grid voltage based on a phase-locked loop (PLL), but lack the ability to actively support the grid. As the capacity of new energy connected to the grid continues to increase, the power angle stability problem of high-proportion new energy sending-end systems is becoming increasingly prominent. Network type converters autonomously construct the voltage and frequency of the grid by simulating the external characteristics of synchronous generators, and currently represent a breakthrough technology for improving system stability. Therefore, constructing a new energy generation system that combines follow / network hybridization enables the system to have both the voltage source characteristics of network type converters (weak grid adaptability) and the current source characteristics of follow-network type converters (strong grid adaptability), becoming a key path for the coordinated development of new energy large-scale grid connection and power electronic converters.

[0003] The capacity optimization configuration of existing follow / network and network converters is divided into three categories: in order to improve the voltage stability of the system, a stability criterion is constructed based on short-circuit ratio constraints, and the optimal capacity ratio threshold of network converters is derived; in order to improve the oscillation stability of the system, the dominant oscillation mode of the follow-network and network hybrid system under different grid strengths is determined, and a multi-converter coordinated control strategy suitable for weak grids is proposed to improve the modal damping ratio of the system under multiple frequency bands; in order to improve the frequency stability of the system, based on the damping ratio and norm index, the coupling mechanism of the proportion of network type converters and control parameters on the steady-state and dynamic characteristics of the system frequency is revealed. The existing technology lacks a consideration of the network and follow converter ratio scheme under power angle stability, and also lacks a network / follow converter ratio research targeting power angle stability constraints. Against this background, how to improve the power angle stability of the system through network / follow converter ratio methods has become a problem to be solved in the field. SUMMARY

[0004] The present application provides a new energy follow / network converter capacity configuration method based on a power angle stability boundary, which aims to solve the power angle stability problem of high-proportion new energy sending-end systems. In the process of follow / network converter capacity configuration, the power angle stability boundary of the system is determined based on the equal-area rule, and the capacity ratio of network converters under the critical power angle stability of the system is obtained through the bisection method, which can effectively reduce the network investment of new energy while improving the power angle stability of new energy sending-end systems.

[0005] Technical solution: A new energy follow / structure network converter capacity configuration method based on power angle stability boundary, comprising the following steps:

[0006] Step 1, based on wind power new energy data and synchronous generator power, a new energy sending end system simulation model including follow network type converter and structure network type converter is constructed, and the steady state operating point of the new energy sending end system is calculated;

[0007] Step 2, based on the steady state operating point, the structure network type converter and the synchronous generator in the new energy sending end system are dynamically equivalent, and the equivalent machine parameters are obtained;

[0008] Step 3, the mechanical power and electromagnetic power of the equivalent machine before, during and after the fault are obtained, the power angle characteristic curve of the equivalent machine is obtained, the acceleration area and the maximum deceleration area of the equivalent machine are calculated, and the power angle stability of the new energy sending end system is judged;

[0009] Step 4, the proportion of structure network type new energy of the equivalent machine under critical power angle stability is obtained by using dichotomy, which is taken as the proportion of structure network type converter under the power angle stability boundary, and the capacity configuration of new energy follow / structure network converter is completed.

[0010] Further, step 1 is: based on power system analysis and synthesis program PSASP platform to establish wind power sending out system, wind power new energy is connected to the grid through follow network type converter and structure network type converter respectively, synchronous generator is boosted through transformer and gathered with wind power new energy, and then connected to infinite system through two return transmission lines; according to network parameters, wind power and synchronous generator power, based on power flow equation, the steady state values of each node voltage, virtual internal potential of structure network type wind power and virtual power angle , internal potential of synchronous generator and power angle steady state value are calculated.

[0011] Further, step 2 specifically includes the following steps:

[0012] Step 2.1, according to the voltage source characteristics of structure network type wind power and synchronous generator, the structure network type wind power and synchronous generator are dynamically equivalent, and the equivalent parameters are:

[0013] (1)

[0014] (2)

[0015] Wherein: and are the internal potential and power angle of the equivalent machine respectively; x1 represents the equivalent reactance of the equivalent machine; x GFMVirtual reactance of grid-connected wind power; Transient reactance of synchronous generator; T and x L1 are the reactances of transformer and single-circuit line 1 passed by the synchronous generator, respectively; G* and T GFM* are the inertia time constants of the synchronous generator and grid-connected wind power, respectively, and are based on the system base capacity S B ; G and S GFM are the rated capacities of the synchronous generator and grid-connected wind power, respectively; G and T GFM are the inertia time constants of the synchronous generator and grid-connected wind power based on their respective capacities S G and S GFM , respectively, and the conversion relationship is:

[0016] (3)

[0017] Step 2.2, star-delta transformation is performed on the equivalent machine grid-connected system to obtain the impedance of the grid-connected system, including the equivalent ground impedance of the equivalent machine, the equivalent ground impedance of the infinite power source, and the equivalent impedance between the equivalent machine and the infinite power source.

[0018] Further, step 3 specifically includes the following steps:

[0019] Step 3.1, when the system is normally running, the active power of the grid-connected wind turbine is P w , the reactive power is 0, and the port voltage is U w ; let the reactive compensation capacity of the wind farm be Q c , and the equivalent ground impedance Z f of the grid-connected wind power is:

[0020] (4)

[0021] wherein Z w represents the equivalent impedance of the wind farm, and j represents the imaginary unit;

[0022] The electromagnetic power of the equivalent machine is:

[0023] (5)

[0024] wherein x2 represents the total line reactance between the synchronous generator and the new energy grid-connected point and the infinite power source; U is the voltage of the infinite power source; x2=0.5x L2 , and x L2 is the line reactance between the synchronous generator and the new energy grid-connected point and the infinite power source;

[0025] Step 3.2, during the fault, the grid-connected wind power enters a low-voltage ride-through state, the active power P w and the reactive power Q w of the grid-connected wind turbine are:

[0026] (6)

[0027] wherein k q is a reactive support coefficient, U in is a threshold value for the new energy unit to enter the low-voltage ride-through state, k p is an active current coefficient, I p is the active current of the grid-connected wind farm, I p0 is the active current of the grid-connected wind farm in normal operation;

[0028] The equivalent ground impedance of the grid-connected wind farm is:

[0029] (7)

[0030] wherein x e is the ground reactance at the fault point, and j is an imaginary unit;

[0031] The electromagnetic power of the equivalent machine is expressed as:

[0032] (8)

[0033] Step 3.3, after the fault is eliminated, the electromagnetic power expression of the equivalent machine is consistent with formula (5), but x2=x L2 .

[0034] Step 3.4, assuming that the steady-state output of the synchronous generator is P G , the total active power of the new energy station is P T , wherein the active power of the grid-connected wind turbine and the grid-forming converter is P w and P GFM , respectively, and satisfies P w +P GFM =P T , the capacity ratio of the grid-forming converter is defined as λ=P GFM / P T , then the mechanical power of the equivalent machine in normal operation, during the fault, and after the fault is eliminated is:

[0035] (9)

[0036] Step 3.5, calculate the acceleration area and deceleration area of the equivalent machine, and judge the power angle stability of the system.

[0037] Further, step 4 specifically includes the following steps:

[0038] Step 4.1, according to the definition of the capacity proportion of the network type converter λ, the numerical lower limit a0=0 and the numerical upper limit b0=1 of λ are obtained, and the bisection method is used

[0039] λ0= (a0+b0) / 2=0.5

[0040] The system power flow under λ0=0.5 is calculated, and the synchronous generator and the network type converter are equivalent;

[0041] Step 4.2, the mechanical power and electromagnetic power of the equivalent machine under λ0=0.5 before, during and after the fault are calculated, and the acceleration area S of the equivalent machine is calculated + And the maximum deceleration area S -max ;

[0042] Step 4.3, if S + >S -max , increase λ0; if S + <S -max , decrease λ0; when λ0 increases or decreases, the bisection method is used; when increasing: a n+1 =λ n , b n+1 =b n , when decreasing: a n+1 =a n , b n+1 =λ n ; wherein λ n 、 a n 、 b n respectively represent the capacity proportion of the network type converter and its lower limit and upper limit at the nth iteration, and λ n+1 、 a n+1 、 b n+1 respectively represent the capacity proportion of the network type converter and its lower limit and upper limit at the (n+1)th iteration;

[0043] Step 4.4, repeat steps 4.2-4.3, and loop iteration until |S + -S -max |<ε, ε is a positive value set; after iteration, the λ result is output.

[0044] The application also discloses a new energy follow / network converter capacity configuration system based on power angle stability boundary, comprising:

[0045] The equivalent unit: the network type wind power and the synchronous generator are dynamically equivalent, and the equivalent machine parameters are obtained;

[0046] The computing unit: the electromagnetic power and the mechanical power of the equivalent machine before the fault, during the fault and after the fault are calculated, the power angle characteristic curve of the equivalent machine is obtained, and the acceleration area and the maximum deceleration area are calculated;

[0047] The searching unit: the binary method is adopted to search the network configuration converter capacity proportion of the equivalent machine under the power angle stability boundary.

[0048] The simulation unit: the high-proportion new energy sending system model containing the network configuration type wind power is established based on the PSASP platform, and the power angle stability of the system under different network configuration converter capacity proportions is analyzed through setting disturbance simulation.

[0049] The application further discloses a computer device, which comprises a memory, a processor and a computer program stored in the memory, and the processor executes the computer program to realize the steps of the method of the application.

[0050] The application further discloses a computer readable storage medium, which stores a computer program / instruction, and the computer program / instruction is executed by a processor to realize the steps of the method of the application.

[0051] The application further discloses a computer program product, which comprises a computer program / instruction, and the computer program / instruction is executed by a processor to realize the steps of the method of the application.

[0052] Advantages: compared with the prior art, the application has the following remarkable advantages: the application proposes a high-proportion new energy sending system follow / network configuration converter capacity configuration method considering the power angle stability boundary, the simulation model is established, the network configuration type converter and the synchronous generator are dynamically equivalent, the system analysis is simplified, and the power angle characteristic curve is derived, the acceleration area and the maximum deceleration area under different network configuration type converter proportions can be accurately calculated, and the binary method is adopted, so that the optimal network configuration proportion under the critical power angle stability boundary is determined. The method not only effectively improves the power angle stability of the power system, enhances the safety and reliability of the new energy grid connection, but also reduces the system investment cost through optimizing the configuration proportion of the network configuration type converter, improves the accommodation capacity of the power grid to the high-proportion new energy, and provides key technical support for the large-scale grid connection of new energy and the coordinated development of power electronic converters. BRIEF DESCRIPTION OF DRAWINGS

[0053] Figure 1 It is a method flowchart of the application;

[0054] Figure 2 It is a new energy sending end grid connection system diagram;

[0055] Figure 3 It is a new energy sending end system circuit diagram; wherein, (a) is Figure 2 the circuit diagram of the system; (b) is the equivalent circuit diagram;

[0056] Figure 4 The star-delta conversion equivalent circuit diagram of the new energy sending end system;

[0057] Figure 5 The equivalent machine power angle curve diagram under different proportions of the network construction converter;

[0058] Figure 6 The power angle curve diagram of the equivalent machine under different proportions of the network construction converter;

[0059] Figure 7 The power angle curve diagram of the synchronous generator and the network construction type wind power, wherein (a) is the equivalent machine power angle instability case, and (b) is the equivalent machine power angle stability case. DETAILED DESCRIPTION

[0060] The technical solutions of the present application will be further described below in combination with the drawings.

[0061] Example 1: As Figure 1 shown, the flow of the present application is as follows:

[0062] Step 1, establish a new energy sending end system simulation model containing a network construction type converter, and calculate the steady state operating point of the system.

[0063] Based on the PSASP platform, the sending end grid-connected system containing the network construction type new energy is constructed as shown in Figure 2 , the wind power is connected to the grid through the network following type converter and the network construction type converter respectively, the synchronous generator is boosted through the transformer and connected with the new energy, and then connected to the infinite system through 2 transmission lines. Figure 3 (a) in Figure 2 is the circuit diagram of the system, Figure 3 (b) is the equivalent circuit, and the system parameters are shown in Table 1.

[0064] Table 1 Parameters of the sending end grid-connected system containing the network construction type wind power

[0065]

[0066] Among them, and are the internal potential and power angle of the synchronous generator respectively; and are the internal potential and power angle of the network construction converter respectively; is the transient reactance of the synchronous generator; is the internal reactance of the network construction converter; and are the voltages of the wind power grid connection point and the infinite power supply respectively;I G and I wI0 represents the output current of the synchronous generator and the grid-connected wind farm, respectively; I2 represents the transmission line current; the grid-connected wind farm uses an impedance of Z0. w Impedance model; x T x L1 and x L2 The reactances of the transformer, single-circuit line 1, and single-circuit line 2 are respectively; x e This refers to the grounding reactance at the short-circuit point during the fault.

[0067] Step 2: Dynamically equivalence the grid-type converter and synchronous generator in the system to obtain the equivalent machine parameters. Based on this, the original simulation system is simplified into an equivalent machine and a grid-connected new energy transmission system.

[0068] (1)

[0069] Where: x1 represents the equivalent reactance of the equivalent machine; and These are the internal electromotive force and power angle of the isoelectric machine, respectively; T G* and T GFM* The inertial time constants of synchronous generators and grid-connected wind power, respectively (based on the system reference capacity S). B (Based on); S G and S GFM Rated capacity for synchronous generators and grid-connected wind power; T G and T GFM Synchronous generators and grid-connected wind power, respectively, are represented by their respective capacities S. G and S GFM The inertia time constant is the reference value; the conversion relationship between the two is as follows:

[0070] (2)

[0071] Will Figure 3 Performing a star-triangular transformation on (b) in the equation, we can obtain... Figure 4 The equivalent impedance of the grid-connected system is shown. It includes: Z 10 and Z 20 The equivalent grounding impedances of the equivalent machine and the infinite power supply, respectively, Z eq This is the equivalent impedance between the equivalent machine and the infinite power supply point.

[0072] (3)

[0073] Where: x2 represents the reactance of line 2, Z f This indicates the equivalent grounding impedance of the wind farm connected to the grid.

[0074] Step 3, derive the mechanical power and electromagnetic power of the equivalent machine before, during and after the fault, and obtain the power angle characteristic curve of the equivalent machine; calculate the acceleration area and maximum deceleration area of the equivalent machine, and judge the power angle stability of the system.

[0075] When the system is running normally, the active power of the grid-connected wind turbine is P w , the reactive power is 0, and the port voltage is U w ; assuming that the reactive power compensation capacity of the wind farm is Q c , the equivalent grounding impedance Z f of the grid-connected wind power is:

[0076] (4)

[0077] The electromagnetic power of the equivalent machine is:

[0078] (5)

[0079] Wherein, x2 represents the total line reactance between the synchronous generator and the new energy grid connection point and the infinite power source; U is the voltage of the infinite power source; x2=0.5x L2 , x L2 is the line reactance between the synchronous generator and the new energy grid connection point and the infinite power source.

[0080] During the system fault, assuming that the grid-connected wind power enters the low voltage ride through state, the active power P w and the reactive power Q w of the grid-connected wind turbine are:

[0081] (6)

[0082] Wherein, k q is the reactive power support coefficient, U in is the threshold value of the new energy unit entering the low voltage ride through, k p is the active current coefficient, I p0 is the active current when the grid-connected wind farm is working normally.

[0083] The equivalent grounding impedance of the grid-connected wind farm is:

[0084] (7)

[0085] The electromagnetic power of the equivalent machine is expressed as:

[0086] (8)

[0087] After the fault is removed, the electromagnetic power expression of the equivalent machine is consistent with formula (5), but x2=x L2 .

[0088] Mechanical power: let the steady-state output of the synchronous generator be P G , the total active output of the new energy station be P T , the output of the grid-connected wind power and the grid-forming converter be P w and P GFM respectively, and satisfy P w + P GFM = P T , the capacity proportion of the grid-forming converter be λ defined as λ = P GFM / P T , then the mechanical power of the equivalent machine during normal operation, fault and after fault removal is:

[0089] (9)

[0090] According to the mechanical power and electromagnetic power of the equivalent machine before, during and after the fault, and taking λ as 0 and 15%, the equivalent machine power angle curve of the grid-forming converter under different proportions is obtained as shown in Figure 5 . In the figure, the solid line is the power angle characteristic curve of the equivalent machine when the output of the synchronous generator is 300 MW, the total output of the new energy is 360 MW, and the capacity of the grid-forming new energy is 0. At this time, ABCD is the acceleration area of the equivalent machine, and CEF represents the maximum deceleration area of the equivalent machine. When the proportion of the grid-forming new energy is 15%, the virtual straight line af represents the mechanical power of the equivalent machine, the virtual line bc represents the electromagnetic power of the equivalent machine during the fault, and the virtual line df represents the electromagnetic power of the equivalent machine after the fault is removed. At this time, abcd is the acceleration area of the equivalent machine, and cef represents the maximum deceleration area. It can be seen that after the proportion of the grid-forming new energy increases, the acceleration area of the equivalent machine decreases, the maximum deceleration area increases, and the stability of the system power angle is improved.

[0091] Step 4, obtain the proportion of the grid-forming new energy under the critical power angle stability of the equivalent machine by using the bisection method, and take it as the proportion of the grid-forming converter under the power angle stability boundary of the system;

[0092] Step 4.1, according to the definition of λ, the numerical lower limit a0 of λ is 0, and the numerical upper limit b0 of λ is 1. According to the bisection method, λ0 = (a0 + b0) / 2 = 0.5, calculate the power flow of the system under λ0 = 0.5, and equivalent the synchronous generator and the grid-forming converter.

[0093] Step 4.2, calculate the mechanical power and electromagnetic power of the equivalent machine before, during and after the fault under λ0 = 0.5, and calculate the acceleration area S + and the maximum deceleration area S -max of the equivalent machine according to this;

[0094] Step 4.3, if S + > S -maxIncrease λ0; if S + -max Then decrease λ0. When λ0 increases or decreases, the dichotomy principle applies. When it increases: a n+1 =λ n b n+1 =b n When decreasing: a n+1 =a n b n+1 =λ n (n=0,1,2,…), where λ n , a n , b n Let λ represent the capacity ratio of the grid-type converter and its lower and upper limits, respectively, in the nth iteration. n+1 , a n+1 , b n+1 These represent the capacity ratio of the grid-type converter and its lower and upper limits, respectively, in the (n+1)th iteration.

[0095] Step 4.4: Return to step 4.1 and iterate until |S + -S -max |<ε (ε is a set small positive value). The iteration ends, and the result λ is output.

[0096] The acceleration area and maximum deceleration area of ​​the equivalent machine under different λ values ​​were calculated using the bisection method, as shown in Table 2.

[0097] Table 2. Acceleration area and maximum deceleration area of ​​the equivalent machine under different λ values.

[0098]

[0099] As shown in Table 2, when the grid-connected converter accounts for 10% of the total power, the difference between the acceleration area and the maximum deceleration area is 0.0083, indicating that the system is close to the critical power angle stability. When this proportion is increased, the maximum deceleration area is greater than the acceleration area, and the system's transient power angle stabilizes.

[0100] Step 5: Perform simulation based on the PSASP platform to verify the rationality of the proposed configuration principle.

[0101] Based on the PSASP platform, Figure 2 Taking the system shown as an example, the system base capacity is 250MVA, where the synchronous generator output power is 1.0+j0.5, and the active power output of the renewable energy power station is 300MW. The disturbance is set as a grounding event occurring at the beginning of one circuit of transmission line 2 at t=1s, with a reactance of x. e ​=0.04p.u.three-phase short-circuit fault, the fault lasts for 1s and ends, and one loop is cut off after the fault. Figure 6 .

[0102] From Figure 6 it can be seen that when the grid-connected converter ratio is 6.6% and 7%, the equivalent machine power angle is unstable, and when the grid-connected converter ratio is 6.6%, the system power angle is more unstable. When the grid-connected converter ratio is 10%, the critical power angle of the equivalent machine is stable. When the grid-connected converter ratio increases to 50%, the system power angle is stable. The calculation result is consistent with the bisection method.

[0103] The power angle curves of the synchronous generator and the grid-connected converter in the two working conditions of equivalent machine power angle instability and critical power angle stability are shown in Figure 7 From Figure 7 it can be seen that the power angle of the synchronous generator and the grid-connected converter changes synchronously, which shows the feasibility of dynamic equivalence of the two.

[0104] The application also discloses a high-proportion new energy sending-end system grid-connected / converter capacity configuration system considering power angle stability boundary, which comprises:

[0105] An equivalent unit: the grid-connected wind power and the synchronous generator are dynamically equivalent, and equivalent machine parameters are obtained;

[0106] A calculation unit: electromagnetic power and mechanical power of the equivalent machine before, during and after the fault are calculated, and the power angle characteristic curve of the equivalent machine is obtained, and the acceleration area and the maximum deceleration area are further calculated;

[0107] A search unit: the bisection method is used to search the grid-connected converter capacity ratio of the equivalent machine under the power angle stability boundary;

[0108] A simulation unit: a high-proportion new energy sending-out system model containing the grid-connected wind power is established based on the PSASP platform, and the power angle stability of the system under different grid-connected converter capacity ratios is analyzed by setting disturbance simulation.

Claims

1. A method for configuring capacity of a new energy grid-connected / inverter based on a power angle stability boundary, characterized in that, Comprise the following steps: Step 1, based on wind power new energy data and synchronous generator power, build new energy sending end system simulation model including follow network type converter and network type converter, calculate new energy sending end system steady state operating point; Step 2, based on steady state operating point, dynamic equivalent of network type converter and synchronous generator in new energy sending end system is carried out, and equivalent machine parameter is obtained; Step 3, the mechanical power and electromagnetic power of equivalent machine before, during and after fault are obtained, the power angle characteristic curve of equivalent machine is obtained, the acceleration area and maximum deceleration area of equivalent machine are calculated, and the power angle stability of new energy sending end system is judged; Step 4, the proportion of network type new energy under critical power angle stability is obtained by dichotomy, which is taken as the proportion of network type converter under system power angle stability boundary, and the configuration of new energy follow / network converter capacity is completed. 2.The method of claim 1, wherein, The step 1 is specifically: based on a power system analysis integrated program (PSASP) platform, a wind power sending system is established, wind power new energy is connected to the grid through a grid-following type converter and a grid-constructing type converter respectively, a synchronous generator is boosted through a transformer and is gathered with the wind power new energy, and then is connected to an infinite system through two transmission lines; according to network parameters, wind power and synchronous generator power, based on a power flow equation, steady-state values of each node voltage, virtual internal electric potential of the grid-constructing type wind power and virtual power angle, internal electric potential of the synchronous generator and power angle steady-state values are calculated. .​​​ 3. The method of claim 2, wherein, Step 2 specifically comprises the following steps: Step 2.1, according to the voltage source characteristics of network type wind power and synchronous generator, the network type wind power and synchronous generator are dynamically equivalent, and the equivalent parameter is: (1) (2) Wherein: and are the internal potential and power angle of the equivalent machine, respectively; x1 represents the equivalent reactance of the equivalent machine; x GFM represents the virtual reactance of the grid-connected wind power; is the transient reactance of the synchronous generator; x T and x L1 are the reactances of the transformer and the single-circuit line 1 passed by the synchronous generator, respectively; T G* and T GFM* are the inertia time constants of the synchronous generator and the grid-connected wind power, respectively, and are based on the system reference capacity S B ; S G and S GFM are the rated capacities of the synchronous generator and the grid-connected wind power; T G and T GFM are the inertia time constants of the synchronous generator and the grid-connected wind power based on their respective capacities S G and S GFM , and the conversion relationship is: (3) Step 2.2, the star-delta transformation of equivalent machine grid-connected system is carried out, the impedance of grid-connected system is obtained, including equivalent machine equivalent grounding impedance, infinite power equivalent grounding impedance and equivalent impedance between equivalent machine and infinite power point.

4. The method of claim 3, wherein, Step 3 specifically comprises the following steps: Step 3.1, when the system is running normally, the active power of the grid-connected wind turbine is P w , the reactive power is 0, and the port voltage is U w ; assuming that the reactive power compensation capacity of the wind farm is Q c , the equivalent ground impedance Z f of the grid-connected wind power is: (4) wherein Z w represents the equivalent impedance of the wind farm, and j represents the imaginary unit; The electromagnetic power of equivalent machine is: (5) Wherein, x2 represents the total line reactance between the synchronous generator and the new energy grid connection point and the infinite power supply; U is the voltage of the infinite power supply; x2=0.5x L2 , x L2 is the line reactance between the synchronous generator and the new energy grid connection point and the infinite power supply; Step 3.2, during the fault, the grid-following wind power enters a low voltage ride through state, the active power P w and the reactive power Q w Specifically: (6) wherein k q is the reactive support coefficient, U in is the threshold for the low-voltage ride-through of the new energy unit, k p is the active current coefficient, I p is the active current of the grid-connected wind farm; and I p0 is the active current of the grid-connected wind farm in normal operation. The equivalent grounding impedance of follow network wind farm is: (7) where x e is the fault point grounding reactance, j is the imaginary unit; The electromagnetic power of equivalent machine is expressed as: (8) Step 3.3, After the fault is removed, the electromagnetic power expression of the equivalent machine is consistent with formula (5), but x2=x L2 ; Step 3.4, set the steady-state output of the synchronous generator as P G , the total active power of the new energy station as P T , wherein the active power of the grid-connected wind turbine and the grid-forming converter is P w and P GFM , respectively, and P w + P GFM =P T , the capacity proportion of the grid-forming converter is defined as λ=P GFM / P T , and the mechanical power of the equivalent machine during normal operation, fault, and after fault elimination is: (9) Step 3.5, the acceleration area and deceleration area of equivalent machine are calculated, and the power angle stability of system is judged.

5. The method of claim 4, wherein, Step 4 specifically comprises the following steps: Step 4.1, according to the definition of network type converter capacity proportion λ, the numerical lower limit a0=0 and the numerical upper limit b0=1 of λ are obtained, and according to dichotomy λ0=(a0+b0) / 2=0.5 The system power flow under λ0=0.5 is calculated, and the synchronous generator and network type converter are equivalent; Step 4.2, Calculate the mechanical power and electromagnetic power of the equivalent machine under λ0=0.5 before the fault, during the fault and after the fault, and calculate the accelerating area S of the equivalent machine + and the maximum decelerating area S -max ; Step 4.3, if S + > -max , increase λ0; if S + < S -max , decrease λ0; when λ0 increases or decreases, the bisection principle is adopted; when increasing: a n+1 = λ n , b n+1 = b n , when decreasing: a n+1 = a n , b n+1 = λ n ; wherein λ n 、 a n 、 b n respectively represent the capacity proportion of the grid-forming type converter and its lower limit and upper limit at the n th iteration, λ n+1 、 a n+1 、 b n+1 respectively represent the capacity proportion of the grid-forming type converter and its lower limit and upper limit at the n+1 th iteration; Step 4.

4. Repeat Step 4.2-4.3, loop iteration until |S + - S -max | < ε, ε is a positive value set; after iteration, output λ result.

6. A new energy follow / network converter capacity configuration system based on power angle stability boundary, for realizing the method of claim 1, characterized in that, Comprise: Equivalent unit: dynamically equivalent network type wind power and synchronous generator, and obtain equivalent machine parameter; Calculation unit: calculate the electromagnetic power and mechanical power of equivalent machine before, during and after fault, obtain the power angle characteristic curve of equivalent machine, and calculate the acceleration area and maximum deceleration area; Search unit: dichotomy is adopted to search the network type converter capacity proportion of equivalent machine under power angle stability boundary; Simulation unit: based on PSASP platform, the high proportion new energy sending out system model containing network type wind power is established, and the disturbance simulation is set to analyze the power angle stability of system under different network type converter capacity proportion.

7. A computer apparatus comprising a memory, a processor, and a computer program stored on the memory, wherein the computer program, when executed by the processor, causes the processor to perform the method of any one of claims 1 to 6. The processor executes the computer program to realize the steps of the method of claim 1.

8. A computer readable storage medium having stored thereon computer programs / instructions, characterized in that, The computer program / instruction is executed by the processor to realize the steps of the method of claim 1.

9. A computer program product comprising computer programs / instructions, characterized in that, The computer program / instruction is executed by the processor to realize the steps of the method of claim 1.

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