High-proportion power electronic system networking converter demand evaluation method

Abstract

The invention discloses a high-proportion power electronic system networking converter demand evaluation method, which comprises the following steps: expressing a dynamic relationship between active power and frequency after a system is disturbed through a synchronous machine rotor motion equation to obtain an active power-frequency dynamic model, and obtaining system equivalent inertia according to the model; establishing a system frequency dynamic response model, and calculating to obtain the minimum inertia requirement of the system considering the frequency shift rate and the maximum frequency deviation constraint; the equivalent inertia of the system is expressed by adopting the weighted average of each inertia source, and the comprehensive inertia of the system is increased by increasing the number of the network-forming converters so as to meet or exceed the minimum inertia requirement of the system. The method has the beneficial effects that the requirements of the network construction type converter under different power system conditions can be accurately evaluated, and the system can still be kept stable when subjected to frequency disturbance.

Description

Technical Field

[0001] The present invention relates to the technical field of novel power systems, and in particular to a method for evaluating grid-connected converter requirements in a high-proportion power electronic system. Background Art

[0002] With the continuous acceleration of the process of building a new power system in my country, the access capacity and proportion of renewable energy generators based on converters will further increase. At the same time, due to the decoupling of the non-synchronous power source from the power system frequency, it does not have the ability to provide inertia support to the system under active disturbance, resulting in a reduction in the inertia level of the entire system. This reduction in inertia may have an adverse effect on the frequency stability of the power grid, especially when the power system is disturbed.

[0003] In order to solve this problem and ensure the stability and reliability of the power system, in recent years, grid-type converters, as a technology that can actively support the frequency and voltage of the power grid, have gradually received attention. Unlike traditional grid-type converters, grid-type converters can simulate the inertia characteristics of rotating machinery and provide virtual inertia through control strategies, thereby improving the frequency response capability of the system. However, when designing high-proportion power electronic systems, there is still a lack of systematic evaluation methods for the configuration and demand evaluation of grid-type converters, which brings uncertainty to the design and operation of high-proportion power electronic systems and affects the stability of the system.

[0004] Existing evaluation methods mainly focus on the impact of traditional synchronous generators on system inertia. However, for the demand evaluation of grid-connected converters in high-proportion power electronic systems, many methods fail to fully consider their role in system frequency response and lack effective tools and models. These methods fail to fully consider the dynamic response characteristics of grid-connected converters under different grid conditions, resulting in inaccurate judgment of converter configuration in system design, affecting the frequency stability and reliability of the system.

[0005] When calculating the grid-connected converter requirements of power electronics systems, existing evaluation methods often ignore the different effects of grid-connected and grid-connected converters on the system frequency response, resulting in insufficient accuracy of the evaluation results. Summary of the invention

[0006] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a method for evaluating the demand for grid-type converters in high-proportion power electronic systems. The method provides a tool for accurately calculating the configuration ratio of grid-type converters by comprehensively analyzing the inertia requirements, frequency response characteristics, and dynamic behaviors of grid-type converters in different operating scenarios of the system, so as to ensure the stability and reliability of the system under frequency disturbances. The method is specifically implemented by the following technical solutions:

[0007] The method for evaluating the demand for grid-connected converters in a high-proportion power electronic system, wherein the high-proportion power electronic system comprises a grid-connected converter and a grid-following converter,

[0008] The dynamic relationship between active power and frequency after the system is disturbed is expressed by the synchronous machine rotor motion equation. The synchronous machine rotor motion equation is equivalently processed to obtain the active power-frequency dynamic model under ramp gradually changing disturbance power. The system equivalent inertia H is obtained according to the model. sys ;

[0009] The system frequency dynamic response model is established, using the inertial center frequency f coi The frequency of the entire system or regional system is represented by combining the time domain formula of the central inertia frequency with the time domain formula of the power system frequency response considering the frequency regulation dead zone to calculate the minimum inertia requirement H of the system considering the frequency shift rate and the maximum frequency deviation constraint. cr ; The equivalent inertia H of the system is expressed by the weighted average of each inertia source sys By increasing the number of grid-type converters, the system's comprehensive inertia can be increased to meet or exceed the system's minimum inertia requirement H. cr .

[0010] The further design of the high-proportion power electronic system grid converter demand assessment method is that the process of obtaining the active power-frequency dynamic model under the ramp gradually changing disturbance power is specifically as follows:

[0011] The synchronous machine rotor swing equation is set as:

[0012]

[0013] In formula (1), H sg,i is the inertia time constant of synchronous machine i; S sg,i is the rated capacity of synchronous machine i; P m,i is the mechanical input power of synchronous machine i; P e,i is the electromagnetic power output by synchronous machine i; ΔP i is the unbalanced power of synchronous machine i; Δf i is the frequency change of the synchronous machine i at the grid connection point; f0 is the rated frequency of the system; D i is the damping coefficient of synchronous machine i;

[0014] Under the set conditions, the whole system or regional system is regarded as an equivalent synchronous machine, and the equivalent swing equation of the system is:

[0015]

[0016] According to formula (3), the Laplace transform of formula (2) is performed to obtain the relationship between the system frequency change in the frequency domain and the system equivalent inertia;

[0017]

[0018] In formula (3), s is the pull operator; ΔP sys is the ramp-varying disturbance power, satisfying ΔP sys (s) = kt, k is the slope of the ramp-changing disturbance power, determined by the PMU power data in the RLS-AF; t is the duration of the ramp-changing disturbance;

[0019] By ΔP sys Substituting Laplace transform into equation (3) yields the relationship between the frequency change under ramp gradual disturbance and the slope of ramp gradual disturbance, the system equivalent inertia and the system equivalent damping coefficient:

[0020]

[0021] By performing an inverse Laplace transform on equation (4), we can get the expression of the frequency change in the time domain. Then, by differentiating the frequency change in the time domain, we can obtain the relationship between RoCoF and the slope of the ramp-varying disturbance power, the system equivalent inertia and the system equivalent damping coefficient, and complete the construction of the active-frequency dynamic model under the ramp-varying disturbance power:

[0022]

[0023] The further design of the high-proportion power electronic system grid converter demand assessment method is to obtain the system equivalent inertia H according to formula (6): sys ,

[0024]

[0025] The further design of the high-proportion power electronic system grid-connected converter demand assessment method is that when the frequency deviation is in the main frequency regulation dead zone, the system enters the inertial response stage, the main frequency regulation equipment plays a role, and the system frequency dynamic response model considering the main frequency regulation dead zone is constructed according to formula (7).

[0026]

[0027] Where ΔP G T is the increase in mechanical power of the prime mover under the control of the speed governor when frequency deviation occurs; m is the time constant of the entire speed regulation system; K G K is the static characteristic coefficient of the power frequency of the generator set. G =1 / δ, where Δf is the speed regulator adjustment coefficient. d It is the main FM dead zone;

[0028] After the frequency regulation is cut off, the system frequency response is:

[0029]

[0030] in,

[0031]

[0032] A1=2H(αsinωt d -ωcosωt d )-(D+K G )sinωt d ;

[0033] A2=2H(-ωsinωt d -αcosωt d )+(D+K G )cosωt d ;

[0034]

[0035] Among them, α, A m 、A1、A2、t d It is an intermediate parameter introduced to simplify the formula. It replaces complex expressions with specific letter symbols and has no actual physical meaning. H is the system equivalent inertia, D is the load frequency response coefficient, T m is the time constant of the speed regulation system, K G is the generator power frequency static characteristic coefficient, ω is the power frequency angular frequency, ΔP0 is the power gain after the system frequency is disturbed, and Δf is the magnitude of the frequency disturbance.

[0036] The further design of the high-proportion power electronic system grid converter demand assessment method is to construct a time domain formula of the power system frequency response considering the primary frequency regulation dead zone according to formula (7) in combination with the system frequency dynamic response model.

[0037]

[0038] In formula (9), K G K is the static characteristic coefficient of the power frequency of the generator set. G =1 / δ, δ is the speed regulator adjustment coefficient, Δf d Main FM dead zone.

[0039] According to formula (10), the time domain formula of the central inertial frequency is constructed:

[0040]

[0041] In formula (10), S in is the rated capacity of the i-th generation traditional and renewable energy generators, H Tiis the inertia time constant of the i-th generation generator.

[0042] The further design of the high-proportion power electronic system grid converter demand assessment method is to obtain the system minimum inertia requirement H according to formula (11): cr ,

[0043] H cr =max{H ROCOF ,H MDF}(11)

[0044] Among them, H ROCOF H is the minimum inertia of the system considering the frequency constraint change rate, MDF is the minimum inertia of the power system considering the maximum deviation.

[0045] The method for evaluating the demand for grid-connected converters in a high-proportion power electronic system is further designed in that the calculation process of the minimum inertia of the system considering the frequency constraint change rate is as follows: Substituting equation (8) into equation (4) and taking the derivative to obtain the maximum value of the inertia center frequency change rate after the system disturbance is obtained:

[0046]

[0047] Where ΔP i The frequency modulation power allocated to the i-th generator;

[0048] Combined with the expression of the equivalent inertia time constant of the power system:

[0049]

[0050] Under the constraint of frequency change rate, the minimum inertia of the system is obtained:

[0051]

[0052] Where ROCOF is the frequency constraint change rate.

[0053] The method for evaluating the demand for grid-connected converters in a high-proportion power electronic system is further designed in that the calculation process of the minimum inertia of the power system considering the maximum deviation is:

[0054] At the minimum frequency, the frequency change rate is 0, and substituting it into the equation gives:

[0055]

[0056] Substituting equation (15) into equation (10), the maximum rate of change of the inertial center frequency after the system is disturbed is:

[0057]

[0058] When the inequality takes the equal sign, the minimum inertia H of the power system considering the maximum deviation is obtained. MDF :

[0059]

[0060] The high-proportion power electronic system grid-connected converter demand assessment method is further designed to express the equivalent inertia of the system by the weighted average of each inertia source according to formula (18);

[0061]

[0062] In the formula, H fo is the inertia of the grid-type converter; M is the number of grid-type converters; H fl is the inertia of the grid-following converter; N is the number of grid-following converters, and the sum of M and N remains unchanged;

[0063] Ensure that the system's comprehensive inertia H sys Meet or exceed the system minimum inertia requirement H cr If it is not satisfied, increase the number of grid-forming converters M and reduce the number of grid-following converters N until the requirements are met. The demand ratio of grid-forming converters at this time is obtained as:

[0064]

[0065] The present invention also provides an electronic device, comprising a memory, a processor and a computer program, wherein the computer program is stored in the memory and is configured to be executed by the processor to implement the method for evaluating grid-connected converter requirements in a high-proportion power electronics system.

[0066] The advantages of the present invention are as follows:

[0067] Accurate converter demand assessment: By considering the overall inertia distribution and dynamic frequency response characteristics of the system, the present invention can accurately assess the demand for grid-connected converters under different power system conditions, ensuring that the system remains stable when subjected to frequency disturbances.

[0068] Optimize the configuration of grid-connected converters: By reasonably configuring the proportion of grid-connected converters, ensure that the system has sufficient inertia under frequency disturbances, and improve the frequency stability and anti-disturbance capability of the system.

[0069] Improve the reliability of the power system: By rationally configuring the grid-connected converter, the present invention can significantly improve the overall frequency stability of the power system, reduce the risk of frequency instability caused by insufficient inertia, and improve the safety and reliability of power grid operation.

[0070] Wide scope of application: This method is applicable to various new power systems, especially power systems with a high proportion of renewable energy access, and provides an important reference for system planning and design. DETAILED DESCRIPTION

[0071] The technical solution of the present invention is described in detail below.

[0072] The embodiment of the present invention discloses a method for evaluating the demand of a grid-connected converter of a high-proportion power electronic system. The high-proportion power electronic system includes a grid-connected converter and a grid-following converter. The method specifically includes:

[0073] Firstly, the dynamic relationship between active power and frequency after the system is disturbed is expressed by the synchronous machine rotor motion equation. The synchronous machine rotor motion equation is equivalently processed to obtain the active power-frequency dynamic model under ramp gradually changing disturbance power. The system equivalent inertia H is obtained according to the model. sys ;

[0074] Then the system frequency dynamic response model was established, using the inertia center frequency f coi The frequency of the entire system or regional system is represented by combining the time domain formula of the central inertia frequency with the time domain formula of the power system frequency response considering the frequency regulation dead zone to calculate the minimum inertia requirement H of the system considering the frequency shift rate and the maximum frequency deviation constraint. cr ;

[0075] Finally, the equivalent inertia H of the system is expressed by the weighted average of each inertia source: sys By increasing the number of grid-type converters, the system's comprehensive inertia can be increased to meet or exceed the system's minimum inertia requirement H. cr .

[0076] The high proportion of renewable energy is one of the main characteristics of the new power system. Therefore, the equivalent inertia evaluation of the system is considered based on the characteristics of the ramp-gradient disturbance power actively output by renewable energy in certain scenarios. In order to realize the inertia evaluation of the new power system under the ramp-gradient disturbance, the dynamic model of the synchronous machine with the inertia time constant must be characterized. The dynamic relationship between the active power and frequency of the system after the disturbance can be reflected by the synchronous machine rotor motion equation. Therefore, the synchronous machine rotor motion equation can be equivalently processed to obtain the active power-frequency dynamic model required at the system level. The process of obtaining the active power-frequency dynamic model under the ramp-gradient disturbance power is as follows:

[0077] For a synchronous machine in the system, in the initial stage after the system is disturbed and before the synchronous machine speed regulator intervenes, taking into account the damping effect of the synchronous machine, its rotor swing equation can be described as:

[0078]

[0079] In formula (1), H sg,i is the inertia time constant of synchronous machine i; S sg,i is the rated capacity of synchronous machine i; P m,i is the mechanical input power of synchronous machine i; P e,i is the electromagnetic power output by synchronous machine i; ΔP i is the unbalanced power of synchronous machine i; Δf i is the frequency change of the synchronous machine i at the grid connection point; f0 is the rated frequency of the system; D i is the damping coefficient of synchronous machine i;

[0080] Under the set conditions, the whole system or regional system is regarded as an equivalent synchronous machine, and the equivalent swing equation of the system is:

[0081]

[0082] According to formula (3), the Laplace transform of formula (2) is performed to obtain the relationship between the system frequency change in the frequency domain and the system equivalent inertia;

[0083]

[0084] In formula (3), s is a pull operator; different from the step disturbance, the ramp gradually changing disturbance power ΔP sys is a time-varying quantity that satisfies ΔP sys (s)=kt, k is the slope of the ramp-changing disturbance power, which is determined by the PMU power data in the RLS-AF; t is the duration of the ramp-changing disturbance.

[0085] By ΔP sys Perform Laplace transform ΔP sys (s) = k / s 2 , substituting into formula (3), we can get the relationship between the frequency change under ramp gradual disturbance and the slope of ramp gradual disturbance, the system equivalent inertia and the system equivalent damping coefficient:

[0086]

[0087] Perform an inverse Laplace transform on equation (4) to obtain the expression of the frequency change in the time domain. Then differentiate the frequency change in the time domain to obtain the relationship between RoCoF and the slope of the ramp-varying disturbance power, the system equivalent inertia and the system equivalent damping coefficient, and complete the construction of the active-frequency dynamic model under the ramp-varying disturbance power:

[0088]

[0089]

[0090] According to formula (6), the system equivalent inertia H is obtained sys ,

[0091]

[0092] The minimum inertia of the power system obtained based on RoCoF and minimum frequency constraint has problems such as inconsistent frequency response process at different nodes, complex model construction, and low solution efficiency. In order to solve the above problems, this embodiment first establishes a mathematical model of the system frequency dynamic response, using the inertia center frequency f coi To represent the frequency of the entire system (or regional system) in order to reduce the adverse effects of inconsistent frequencies of each bus node on the evaluation accuracy after the disturbance. Then, the time domain formula of the central inertia frequency is combined with the time domain formula of the power system frequency response considering the primary frequency regulation dead zone, and an evaluation strategy for the minimum inertia requirement of the system considering the frequency shift rate and the maximum frequency deviation constraints is proposed to determine the frequency stability of the system after the action.

[0093] When the frequency deviation is in the main frequency regulation dead zone, the system enters the inertial response stage, and the main frequency regulation equipment plays a role. According to formula (7), the system frequency dynamic response model considering the main frequency regulation dead zone is constructed.

[0094]

[0095] Where ΔP G T is the increase in mechanical power of the prime mover under the control of the speed governor when frequency deviation occurs; m is the time constant of the entire speed regulation system; K G K is the static characteristic coefficient of the power frequency of the generator set. G =1 / δ, where Δf is the speed regulator adjustment coefficient. d It is the main FM dead zone;

[0096] After the frequency regulation is cut off, the system frequency response is:

[0097]

[0098] in,

[0099]

[0100]

[0101] A1=2H(αsinωt d -ωcosωt d )-(D+K G )sinωt d ;

[0102] A2=2H(-ωsinωtd -αcosωt d )+(D+K G )cosωt d ;

[0103]

[0104] H is the system equivalent inertia, D is the load frequency response coefficient, T m is the time constant of the speed regulation system, K G is the generator power frequency static characteristic coefficient, ω is the power frequency angular frequency, ΔP0 is the power gain after the system frequency is disturbed, and Δf is the magnitude of the frequency disturbance.

[0105] Combined with the system frequency dynamic response model, the time domain formula of the power system frequency response considering the primary frequency regulation dead zone is constructed according to formula (7):

[0106]

[0107] In formula (9), K G K is the static characteristic coefficient of the power frequency of the generator set. G =1 / δ, δ is the speed regulator adjustment coefficient, Δf d Main FM dead zone.

[0108] When the inertia of the power system decreases to a certain critical value, its frequency index will exceed the safety constraint range and trigger the corresponding frequency relay protection device, endangering the reliable operation of the system. Due to the different electrical distances between the interference point and different buses, the discrete distribution of units in the network, and the differences in unit parameters, the frequency dynamic response of the power system has obvious spatiotemporal distribution characteristics: the node frequency changes over time, and the frequency response process of different nodes is inconsistent. Considering the frequency distribution characteristics of the node and the rated capacity and inertia size of each generator, the inertia center frequency f is used. coi To represent the frequency of the entire system (or regional system), it is expressed as:

[0109]

[0110] In formula (10), S in is the rated capacity of the i-th generation traditional and renewable energy generators, H Ti is the inertia time constant of the i-th generation generator.

[0111] When all frequency indicators related to inertia are within the safe range, in order to meet the boundary inertia level after interference, the system's minimum inertia requirement is taken as its maximum value. The system's minimum inertia requirement H cr The expression is as follows:

[0112] H cr =max{HROCOF ,H MDF}(11)

[0113] Among them, H ROCOF H is the minimum inertia of the system considering the frequency constraint change rate, MDF is the minimum inertia of the power system considering the maximum deviation.

[0114] The calculation process of the minimum inertia of the system considering the frequency constraint change rate is:

[0115] At the beginning of the disturbance, the frequency drops fastest and the absolute value of the frequency change rate is the largest. Substituting equation (8) into equation (4) and taking the derivative to obtain the maximum value of the inertia center frequency change rate after the system disturbance is obtained:

[0116]

[0117] Where ΔP i The frequency modulation power allocated to the i-th generator;

[0118] Combined with the expression of the equivalent inertia time constant of the power system:

[0119]

[0120] Under the constraint of frequency change rate, the minimum inertia of the system is obtained:

[0121]

[0122] Where ROCOF is the frequency constraint change rate.

[0123] The calculation process of the minimum inertia of the power system considering the maximum deviation is:

[0124] The maximum frequency deviation of the system is an important measure for evaluating the stability of the system, which can show the degree of frequency drop after the power is disturbed. At the minimum frequency, the frequency change rate is 0, and the substitution is:

[0125]

[0126] Substituting equation (15) into equation (10), the maximum rate of change of the inertial center frequency after the system is disturbed is:

[0127]

[0128] When the inequality takes the equal sign, the minimum inertia H of the power system considering the maximum deviation is obtained. MDF :

[0129]

[0130] Grid-following converters rely on the voltage and frequency of the grid for synchronization and control, usually by measuring the voltage and frequency of the grid and adjusting the output based on these measurements to follow the operating status of the grid. Grid-following converters cannot actively support the frequency and voltage of the grid, and cannot actively adjust the frequency or provide inertia support. Grid-forming converters can actively determine and output voltage and frequency, so they can operate independently and even form a grid without a synchronous power supply. Grid-forming converters do not rely on the existing state of the grid, but can determine the amplitude and phase of the output voltage through their internal control strategy. Therefore, when the frequency of the grid is offset, the grid-forming converter can provide a support effect similar to rotational inertia by adjusting its power output.

[0131] Therefore, by increasing the proportion of grid-connected converters in the system, the comprehensive inertia of the system can be increased. The minimum inertia of the system is usually determined by the frequency stability requirements of the power grid. The minimum inertia requirement H under the frequency change rate constraint has been calculated previously. ROCOF and the minimum inertia requirement H under the maximum deviation constraint MDF , according to formula (18), the equivalent inertia of the system is expressed by the weighted average of each inertia source.

[0132]

[0133] In the formula, H fo is the inertia of the grid-type converter; M is the number of grid-type converters; H fl is the inertia of the grid-following converter; N is the number of grid-following converters, and the sum of M and N remains unchanged;

[0134] Ensure that the system's comprehensive inertia H sys Meet or exceed the system minimum inertia requirement H cr If it is not satisfied, increase the number of grid-forming converters M and reduce the number of grid-following converters N until the requirements are met. According to formula (19), the demand ratio of grid-forming converters at this time is obtained, and the demand assessment of grid-forming converters for high-proportion power electronic systems is completed.

[0135]

[0136] The present invention also provides an electronic device, comprising a memory, a processor and a computer program, wherein the computer program is stored in the memory and is configured to be executed by the processor to implement a method for evaluating grid converter requirements in a high-proportion power electronics system.

[0137] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for evaluating the demand for grid-connected converters in a high-proportion power electronic system, wherein the high-proportion power electronic system comprises a grid-connected converter and a grid-following converter, characterized in that The dynamic relationship between active power and frequency after the system is disturbed is expressed by the synchronous machine rotor motion equation. The synchronous machine rotor motion equation is equivalently processed to obtain the active power-frequency dynamic model under ramp gradually changing disturbance power. The system equivalent inertia H is obtained according to the model. sys ; The system frequency dynamic response model is established, using the inertial center frequency f coi The frequency of the entire system or regional system is represented by combining the time domain formula of the central inertia frequency with the time domain formula of the power system frequency response considering the frequency regulation dead zone to calculate the minimum inertia requirement H of the system considering the frequency shift rate and the maximum frequency deviation constraint. cr ; The equivalent inertia H of the system is expressed by the weighted average of each inertia source sys By increasing the number of grid-type converters, the system's comprehensive inertia can be increased to meet or exceed the system's minimum inertia requirement H. cr .

2. The method for evaluating the demand for grid-connected converters in a high-proportion power electronic system according to claim 1 is characterized in that The process of acquiring the active power-frequency dynamic model under ramp-varying disturbance power is as follows: The synchronous machine rotor swing equation is set as: In formula (1), H sg,i is the inertia time constant of synchronous machine i; S sg,i is the rated capacity of synchronous machine i; P m,i is the mechanical input power of synchronous machine i; P e,i is the electromagnetic power output by synchronous machine i; ΔP i is the unbalanced power of synchronous machine i; Δf i is the frequency change of the synchronous machine i at the grid connection point; f0 is the rated frequency of the system; D i is the damping coefficient of synchronous machine i; Under the set conditions, the whole system or regional system is regarded as an equivalent synchronous machine, and the equivalent swing equation of the system is: According to formula (3), the Laplace transform of formula (2) is performed to obtain the relationship between the system frequency change in the frequency domain and the system equivalent inertia; In formula (3), s is the pull operator; ΔP sys is the ramp-varying disturbance power, satisfying ΔP sys (s) = kt, k is the slope of the ramp-changing disturbance power, determined by the PMU power data in the RLS-AF; t is the duration of the ramp-changing disturbance; By ΔP sys Substituting Laplace transform into equation (3) yields the relationship between the frequency change under ramp gradual disturbance and the slope of ramp gradual disturbance, the system equivalent inertia and the system equivalent damping coefficient: By performing an inverse Laplace transform on equation (4), we can get the expression of the frequency change in the time domain. Then, by differentiating the frequency change in the time domain, we can obtain the relationship between RoCoF and the slope of the ramp-varying disturbance power, the system equivalent inertia and the system equivalent damping coefficient, and complete the construction of the active-frequency dynamic model under the ramp-varying disturbance power:

3. The method for evaluating the demand for grid-connected converters in a high-proportion power electronic system according to claim 2 is characterized in that According to formula (6), the system equivalent inertia H is obtained sys , 4. The method for evaluating the demand for grid-connected converters in a high-proportion power electronic system according to claim 1 is characterized in that When the frequency deviation is in the main frequency regulation dead zone, the system enters the inertial response stage, and the main frequency regulation equipment plays a role. According to formula (7), the system frequency dynamic response model considering the main frequency regulation dead zone is constructed. Where ΔP G T is the increase in mechanical power of the prime mover under the control of the speed governor when frequency deviation occurs; m is the time constant of the entire speed regulation system; K G K is the static characteristic coefficient of the power frequency of the generator set. G =1 / δ, where Δf is the speed regulator adjustment coefficient. d It is the main FM dead zone; After the frequency regulation is cut off, the system frequency response is: in, <h2 style=";text-align:left;direction:ltr">A1 = 2H(αsinωt)<h2 style=";text-align:left;direction:ltr"> d <h2 style=";text-align:left;direction:ltr"> -ωcosωt<h2 style=";text-align:left;direction:ltr"> d <h2 style=";text-align:left;direction:ltr"> )-(D+K<h2 style=";text-align:left;direction:ltr"> G <h2 style=";text-align:left;direction:ltr"> sin<h2 style=";text-align:left;direction:ltr"> d <h2 style=";text-align:left;direction:ltr"> ; A2=2H(-ωsinωt d -αcosωt d )+(D+K G )cosωt d ; Among them, α, A m , A1, A2, t d It is an intermediate parameter introduced to simplify the formula, replacing complex expressions with specific letter symbols, and has no actual physical meaning; H is the system equivalent inertia, D is the load frequency response coefficient, T m is the time constant of the speed regulation system, K G is the generator power frequency static characteristic coefficient, ω is the power frequency angular frequency, ΔP0 is the power gain after the system frequency is disturbed, and Δf is the magnitude of the frequency disturbance.

5. The method for evaluating the demand for grid-connected converters in a high-proportion power electronic system according to claim 4 is characterized in that Combined with the system frequency dynamic response model, the time domain formula of the power system frequency response considering the primary frequency regulation dead zone is constructed according to formula (7): In formula (9), K G K is the static characteristic coefficient of the power frequency of the generator set. G =1 / δ, δ is the speed regulator adjustment coefficient, Δf d It is the main FM dead zone; According to formula (10), the time domain formula of the central inertial frequency is constructed: In formula (10), S in is the rated capacity of the i-th generation traditional and renewable energy generators, H Ti is the inertia time constant of the i-th generation generator.

6. The method for evaluating the demand for grid-connected converters in a high-proportion power electronic system according to claim 5 is characterized in that According to formula (11), the minimum inertia requirement H of the system is obtained: cr , H cr =max{H ROCOF ,H MDF } (11) Among them, H ROCOF is the minimum inertia of the system considering the frequency constraint change rate, H MDF is the minimum inertia of the power system considering the maximum deviation.

7. The method for evaluating the demand for grid-connected converters in a high-proportion power electronic system according to claim 6 is characterized in that The calculation process of the minimum inertia of the system considering the frequency constraint change rate is as follows: Substitute equation (8) into equation (4) and take the derivative to obtain the maximum value of the inertia center frequency change rate after the system disturbance: Among them, ΔP i The frequency modulation power allocated to the i-th generator; Combined with the expression of the equivalent inertia time constant of the power system: Under the constraint of frequency change rate, the minimum inertia of the system is obtained: Where ROCOF is the frequency constraint change rate.

8. The method for evaluating the demand for grid-connected converters in a high-proportion power electronic system according to claim 6 is characterized in that The calculation process of the minimum inertia of the power system considering the maximum deviation is: At the minimum frequency, the frequency change rate is 0, and substituting it into: Substituting equation (15) into equation (10), the maximum rate of change of the inertial center frequency after the system is disturbed is: When the inequality takes the equal sign, the minimum inertia H of the power system considering the maximum deviation is obtained. MDF :

9. The method for evaluating the demand for grid-connected converters in a high-proportion power electronic system according to claim 6 is characterized in that According to formula (18), the equivalent inertia of the system is expressed by the weighted average of each inertia source; In the formula, H fo is the inertia of the grid-type converter; M is the number of grid-type converters; H fl is the inertia of the grid-following converter; N is the number of grid-following converters, and the sum of M and N remains unchanged; Ensure that the system's comprehensive inertia H sys Meet or exceed the system minimum inertia requirement H cr If it is not satisfied, increase the number of grid-forming converters M and reduce the number of grid-following converters N until the requirements are met. The demand ratio of grid-forming converters at this time is obtained as:

10. An electronic device, characterized in that: It comprises a memory, a processor and a computer program, wherein the computer program is stored in the memory and is configured to be executed by the processor to implement the method for evaluating grid converter demand of a high-proportion power electronic system as described in any one of claims 1-9.

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