Method for determining critical thermal power proportion of electric power system with high wind power permeability

Abstract

The invention belongs to the technical field of power system monitoring and maintenance, and relates to a high wind power permeability power system critical thermal power proportion determination method, which comprises the following steps: 1, establishing a wind turbine generator inertia evaluation model considering wind speed fluctuation; 2, deducing a system critical thermal power proportion based on RoCoF constraint; 3, simulation verification; by comparing the output of the wind turbine generator with inertia response control and the output of the wind turbine generator only containing MPPT control when system disturbance occurs and the frequency change conditions of the two systems influenced by the disturbance, it is proved that the fan participates in system frequency modulation under inertia response control by means of the kinetic energy of the rotor of the fan, and the positive effect on the system frequency stability is achieved.

Description

Technical Field

[0001] This invention belongs to the field of power system monitoring and maintenance technology, specifically relating to a method for determining the critical thermal power ratio in power systems with high wind power penetration. Background Technology

[0002] Wind power, as a widely used new energy source, accounts for a significant proportion of new energy installations due to its mature technology and low development costs. Wind turbines, as rotating devices, possess considerable rotational inertia. If feedback control between the power of the wind turbine and the system frequency can be achieved, the wind turbine can also provide some inertial support to the system. Existing coordinated control strategies combining variable coefficient integral inertial control and virtual capacitor control of the turbine-side converter effectively provide inertial support to the system, but these only address single wind turbine units and do not address the coordinated control issues when multiple units are connected to the grid. Furthermore, a hybrid control strategy that optimizes power point tracking methods and pitch angles utilizes wind turbine inertia to provide frequency support for microgrids primarily powered by wind turbines and supplemented by thermal power generation, but it does not consider that fluctuations in actual wind speed may cause real-time changes in initial rotational speed, thus affecting control performance.

[0003] Regarding system inertia requirements, most studies fall into the categories of simulation trial-and-error methods and mechanism derivation methods. However, in terms of wind turbine inertia, while existing technologies consider the time-varying characteristics of inertia, they have not established a mapping model between wind speed fluctuations and effective inertia, making it difficult to assess the inertia support capacity of wind turbines under non-rated wind speeds. Regarding system inertia requirements, existing technologies do not consider the impact of fluctuating environmental conditions such as sunlight and wind speed on the inertia response of renewable energy units, assuming that the renewable energy units are in their rated operating state, resulting in an overestimation of the minimum system inertia. Moreover, existing renewable energy units generally adopt a power-frequency decoupled control method, which prevents them from providing rotational inertia support for the system, thus compromising system safety and stability.

[0004] Therefore, there is an urgent need for a method that can accurately assess the inertia support capacity of wind turbines under non-rated wind speeds, so as to make the minimum inertia assessment results of the system more accurate, in order to solve the above-mentioned technical problems. Summary of the Invention

[0005] This invention aims to provide a method for determining the critical proportion of thermal power in a high wind power penetration power system, taking into account the virtual inertia of wind turbines and the RoCoF constraint of the system. The method specifically includes the following steps: Step 1: Establish a wind turbine inertia assessment model that takes into account wind speed fluctuations; Step 2: Derive the system's critical thermal power ratio based on RoCoF constraints; Step 3: Simulation verification.

[0006] Preferably, in step 1, the frequency domain expression of the equivalent inertia of the wind turbine is: The time-domain expression for the equivalent inertia of the wind turbine is: ;in, Frequency domain representation of the equivalent inertia of a wind turbine. The time-domain representation of the equivalent inertia of the wind turbine. This represents the differential coefficient for virtual inertia control. This represents the proportional coefficient for virtual inertia control. Indicates the initial speed of the fan. Indicates the initial synchronization angular velocity of the system. Indicates the filter time constant. Represents the complex frequency domain operator, t represents time.

[0007] Preferably, in step 1, the equivalent inertia of a wind turbine under actual wind speed conditions is:

[0008] In the formula, This indicates the rated capacity of the corresponding fan. This represents the kinetic energy loss of the wind turbine rotor during the inertial response phase. This represents the equivalent inertia of a wind turbine under actual wind speed conditions. Indicates air density, Indicates the area swept by the blade. The time-varying function representing the wind energy utilization coefficient as a function of time t. Indicates the pitch angle. Indicates wind speed. This indicates the mechanical power of the fan before the disturbance occurred. , These represent the start and end points of time t, respectively.

[0009] Preferably, in step 2, the critical power generation ratio of the thermal power unit is:

[0010] in, This indicates the critical power generation ratio of thermal power units. This represents the constraint on the maximum rate of change of the system's frequency. This represents the unbalanced power of the system at time t. Indicates the system frequency. This refers to the rated capacity of newly built wind turbines when replacing thermal power generators with wind turbines. With the rated capacity of the replaced thermal power generator Relationship, , Indicates the inertia between wind turbine units. Indicates the system's reserve capacity. This represents the inertia between thermal power units.

[0011] More preferably, in step 2, when hour, If the result of the expression is less than or equal to 0 or greater than 1, the system can be entirely composed of wind turbine generators with additional inertia control; where, This indicates the maximum value of the RoCoF constraint. This indicates the system load.

[0012] The beneficial effects of this invention are: 1. This invention demonstrates, by comparing the output of wind turbines with inertial response control and wind turbines with only MPPT control during system disturbances and the frequency changes of the two systems affected by disturbances, that wind turbines using their own rotor kinetic energy to participate in system frequency regulation under inertial response control has a positive effect on system frequency stability.

[0013] 2. Under the critical thermal power ratio, the frequency stability of the system is quantified by the system RoCoF when a disturbance occurs, and the results verify the accuracy of the critical thermal power ratio evaluation model of the present invention.

[0014] 3. Based on RoCoF constraints, this invention proposes the critical proportion of thermal power units from the perspective of inertia, which is more intuitive than the system critical inertia index and is beneficial for dispatchers to monitor and maintain the safety and stability of the power system. Attached Figure Description

[0015] Figure 1 This is a system frequency response diagram of a method for determining the critical thermal power ratio in a power system with high wind power penetration according to the present invention, which includes wind turbine units; Figure 2 This is a graph of the virtual inertia time constant function of the wind turbine according to the present invention; Figure 3 This is a graph showing the relationship between the operating speed and output power of the fan under all wind speed conditions according to the present invention. Figure 4 This is a diagram illustrating the virtual inertia response process of the wind turbine according to the present invention. Figure 5 The present invention is and The graph shows the variation of the difference under different Pt and k. Figure 6 This is a simulation diagram of the improved New England 10-machine 39-node system of the present invention; Figure 7 This is a diagram showing the system frequency variation under the same disturbance according to the present invention; Figure 8 This is a diagram showing the rate of change of system frequency when a disturbance occurs according to the present invention. Figure 9 This is a graph showing the frequency change rate of the entire wind power system under disturbance conditions according to the present invention. Figure 10 This is a scatter plot showing the variation of the propeller pitch angle with wind speed according to the present invention. Detailed Implementation

[0016] The related technologies of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0017] like Figures 1-10 As shown, the method for determining the critical thermal power ratio in a high wind power penetration power system, taking into account the virtual inertia of wind turbines and the RoCoF constraint of the system, specifically includes: 1. Establish a wind turbine inertia assessment model that considers wind speed fluctuations: Step 1-1: Based on the block diagram of the wind turbine's participation in the system's inertia response control, obtain the per-unit value of the wind turbine's electromagnetic torque increment. In the formula, This represents the per-unit value of the electromagnetic torque increment of the fan. This represents the per-unit value of the incremental electromagnetic power of the wind turbine. These are the differential coefficients for virtual inertia control. This is the proportional coefficient for virtual inertia control. This represents the per-unit value of the system frequency deviating from the rated value. The filtering time constant is The converter response time constant, This represents the complex frequency domain operator. The frequency response of a system containing wind turbines is as follows: Figure 1 As shown.

[0018] Step 1-2: Considering the change in the rotational speed of the wind turbine, the rotor motion equation of the wind turbine is obtained as follows: In the formula, Let be the mechanical inertia time constant of the fan. This is the initial speed of the fan. This represents the increment of the fan rotor angular velocity. This represents the initial mechanical torque of the wind turbine. This represents the initial electromagnetic torque of the generator.

[0019] Steps 1-3: Express the rotor motion equations in increments to obtain... .

[0020] Steps 1-4: Transform the rotor motion equations expressed in increments into frequency domain expressions to obtain...

[0021] Steps 1-5: [The text appears to be incomplete and contains several grammatical errors. A more accurate translation would require the full context.] Substitute and get .

[0022] Steps 1-6: Consider and Equal, we get In the formula, This is the system's synchronous angular velocity increment.

[0023] Steps 1-7: Since the wind turbine uses virtual inertia control, the wind turbine is coupled with the system, meaning the turbine speed is coupled with the system speed. Therefore, the change in kinetic energy during the response process should be the same before and after. In the formula: , , These are the number of pole pairs, rated capacity, and inherent moment of inertia of the wind turbine unit, respectively. The virtual moment of inertia of a wind turbine system including integrated inertial control. This represents the initial angular velocity of the system synchronization.

[0024] Steps 1-8: We can obtain .

[0025] Steps 1-9: According to the definition formula of inertia ,get .

[0026] Steps 1-10: [The text appears to be incomplete and contains several grammatical errors. A more accurate translation Substituting this into the equation, and considering that the converter's response speed is much faster than the inertial response and electromechanical transient response processes, i.e. The time constant of the converter Setting it to 0 yields the frequency domain expression for the wind turbine's equivalent inertia. .

[0027] Step 1-11: Perform an inverse Laplace transform on the frequency domain expression to obtain the time domain expression of the wind turbine's equivalent inertia. .

[0028] Steps 1-12: The rated rotor speed of the wind turbine generator is 1800 rpm, the system frequency during disturbance is 50 Hz, and the filter time constant is... It is 0.01s. , The time-varying characteristics of the virtual inertial time constant of wind turbine units are as follows: Figure 2 As shown.

[0029] Steps 1-13: At different wind speeds Under certain conditions, the rotor speed of the fan Significant differences emerge, and the corresponding virtual inertia of the wind turbine changes accordingly. The wind turbine's rotational speed across the entire wind speed range... The relationship with output power P is as follows Figure 3 As shown, the entire wind speed range is divided into four zones: A is the start-up zone, B is the maximum power point tracking zone, C is the constant speed zone, and D is the constant power zone.

[0030] Steps 1-14: Calculate the fan speed based on the operating range of the fan in different wind speed zones. With wind speed The correspondence between them. The wind speed in area A is less than... The fan rotor speed is The wind turbines in the area are operational, with a usable inertia of 0. The wind turbines in Zone B reach their maximum wind energy conversion efficiency. The relationship between turbine speed and wind speed is as follows: In zone C, the turbine rotor speed approaches its upper limit, overspeed control ceases, and pitch control is switched to alter the turbine's power capture. Approximating this region linearly yields the relationship between rotor speed and wind speed: In zone D, where the wind speed exceeds the rated speed, the rotor operates at its maximum speed and is unaffected by wind speed changes. , This means that the mechanical power of the fan reaches its maximum value.

[0031] Steps 1-15: Mechanical power is a function of blade angular velocity and blade pitch angle, and is usually expressed as a nonlinear relationship: In the formula: air density; The area swept by the blade; Wind speed; The wind energy utilization coefficient; To the speed ratio of the blade tip Related intermediate variables; The blade angular velocity; This is a reference value for the blade angular velocity; and This is the PI adjustment parameter for the blade pitch angle. The maximum wind energy capture coefficient under different wind speed conditions can be obtained from the above formula. Optimal tip speed ratio .

[0032] Steps 1-16: Considering the impact of the additional virtual inertia control on the speed change under the unit's operating conditions, analyze the change in system inertia provided by the turbine rotor with wind speed. When the system experiences disturbances, the virtual inertia response duration is short, and it can be assumed that the wind speed remains constant during the process, and there is no pitch adjustment. At the same time, such as Figure 4 As shown, under additional virtual inertia control, the inertia support power As the speed gradually decreases, the fan speed changes approximately linearly with time. Therefore, the function of speed change with time can be used... Approximate fitting. This leads to the function of the tip speed ratio versus time under different initial wind speeds. In the formula , .

[0033] Steps 1-17: [The text appears to be incomplete and contains several grammatical errors. A more accurate translation would require the full context.] Substitution And order hour, We can obtain the simplified time-varying function of the wind energy utilization coefficient as a function of time t when the wind speed is above the cut-in wind speed and below the rated wind speed. When the wind speed exceeds the rated wind speed, the wind turbine operates in the constant speed and constant power range. Due to the control of the blade pitch angle, Depend on Calculations were performed. In the constant speed region, the blade pitch angle was recorded at different wind speeds. In the constant power region, the calculations were combined with... When the power value is constant The pitch angle at high wind speeds is obtained by reverse calculation under the given conditions, and the result is as follows: Figure 10 As shown, a scatter plot of the pitch angle versus wind speed is obtained, and the expression for the pitch angle with respect to wind speed is obtained by function fitting. Then substitute it in, and the subsequent steps are the same as in the MPPT section.

[0034] Steps 1-18: The wind turbine's virtual inertia response provides short-term additional active power support to the grid. This process is divided into two stages: virtual inertia response and rotor kinetic energy recovery. Figure 4 As shown. When the system experiences frequency fluctuations, the virtual inertia control section of the wind turbine responds, and the wind turbine rotor changes from its initial speed. Decrease to the critical speed of inertial response After the wind turbine completes its virtual inertia response, the system performs primary and secondary frequency responses, and the wind turbine rotor speed... The turbine speed is gradually restored to the optimal speed under the current wind speed conditions. In this implementation, the turbine inertia assessment under wind speed fluctuation conditions is only related to the virtual inertia response order of the turbine. Figure 4 The area enclosed by the three points A, B, and C The area represented in part represents the kinetic energy loss of the wind turbine rotor during the inertial response phase, used for frequency support during power disturbances, and can be equivalent to the virtual inertia of the wind turbine participating in the inertial response. You can get .

[0035] Steps 1-19: In actual operation, because the wind speed will not remain constant at the rated wind speed, the fan's moment of inertia will change with the wind speed. Therefore... In the formula: This refers to the rated capacity of the corresponding fan; The equivalent inertia of a wind turbine under actual wind speed conditions.

[0036] 2. Derivation of the system's critical thermal power ratio based on RoCoF constraints: Step 2-1: Under rated conditions, the inertial time constant of the generator set is defined as follows: In the formula: This refers to the rated capacity of the generator; This is the rated mechanical speed. With the system's rated frequency The relationship between the number of rotor pole pairs p and the number of rotor pole pairs p satisfies: .

[0037] Step 2-2: The relationship between the unbalanced power of the fan and the inertial time constant of the unit is as follows: In the formula: This refers to the mechanical power of the wind turbine. Electromagnetic power of wind turbine generator sets; Let be the unbalanced power of the system at time t. The asterisk (*) in the formula represents the per-unit value. Steps 2-3: In the formula: Let the system's moment of inertia be denoted by . Let be the rotor angular frequency of the system.

[0038] Steps 2-4: Combining the above four equations, we can obtain... In the formula: This represents the system's minimum inertia requirement. Let t be the rated capacity of the unit in operation at time t; This refers to the system frequency.

[0039] Steps 2-5: System inertia can be represented by the equivalent inertial time constant. If the n generator sets in the system are divided into m thermal power units and nm wind power units, then the equivalent inertial time constant of the system is: In the formula: Let i be the capacity of the i-th unit; Let be the inertial time constant of the i-th unit.

[0040] Steps 2-6: Considering the uncertainty of wind power, and ensuring that the load capacity of the power plant remains unchanged, when replacing thermal power generators with wind turbines, what is the rated capacity of the newly built wind turbines? It should be greater than the rated capacity of the thermal power generator being replaced. Introducing coefficients Describe their relationship. .

[0041] Steps 2-7: Combined , The numerator and denominator are simultaneously affected Taking the partial derivative, we get In the formula: It is the system load; Let be the inertia of the i-th thermal power unit; Let be the inertia of the k-th wind turbine unit at inertial response time t seconds; take . , Numerical analysis results, take .

[0042] Steps 2-8: From It can be concluded that at the rated wind speed, conditions, It can be known that This indicates that as the proportion of thermal power generation increases, the actual rate of change of inertia is greater than the rate of change of the system's required inertia. Combined with the fact that traditional power systems have sufficient inertia, this leads to... , Sometimes, Based on the actual situation that high-proportion new energy systems have insufficient anti-disturbance capabilities, Sometimes, Therefore, the actual inertia change curve and the system demand inertia change curve must intersect at some point. Assuming that the inertia of each thermal power unit is the same... The moment of inertia of each wind turbine is the same. The system's reserve capacity can be obtained as follows:

[0043] Steps 2-9: Let , can be obtained In the formula: This represents the critical power generation ratio of thermal power units. This is a constraint on the system's maximum rate of change of frequency. It should be noted that when... hour, The result of the expression is less than or equal to 0 or greater than 1, which means that the system can be composed entirely of wind turbine units with additional inertia control.

[0044] Step 2-10: Consider the wind turbine operating in the MPPT range with additional inertia control. , ,Depend on Know ,set up At this time, At this point, the system's inertia is entirely provided by the wind turbine generators, which satisfies the RoCoF constraint; [Setting] At this time, This means the system requires a minimum of 12.56% of thermal power units; [Setting] At this time .

[0045] Step 2-11: [Regarding...] and The differenceu The assessment is conducted in accordance with changes in the proportion of thermal power and unbalanced power. u The plane with =0 and and The difference u The intersection of the planes formed is the curve of the critical power generation ratio of thermal power as a function of unbalanced power. To verify the rationality of the conclusion, the wind speed was set to 8 m / s, and the maximum frequency change rate of the system was ±1 Hz / s. The result is as follows: Figure 5 The system's critical thermal power generation ratio is shown in the figure. k Indicates the proportion of thermal power; It represents the ratio of unbalanced power to system load.

[0046] 3. Simulation verification: Step 3-1: Select the New England 10-machine 39-node system for simulation verification, such as... Figure 6 As shown, based on the different proportions of thermal power in the system, wind farms W1, W3, and W5 with virtual inertia control were used to replace the original G1, G3, and G5 units, respectively. The wind turbines in the wind farms are convergent equivalent doubly-fed turbines, with a single turbine having a rated capacity of 1.5 MW, a rated wind speed of 13 m / s, a rotor radius of 170 m, and the optimal tip speed ratio corresponding to a pitch angle of 0°. The maximum wind energy utilization coefficient is 6.3249. The value is 0.4382; the blade angular velocity reference value is 2.056 rad / s, corresponding to the synchronous speed; the safe range of blade angular velocity is 0.7~1.2 pu; the maximum permissible electromagnetic torque is... The per-unit power rating is 1.35 pu; the grid-side inverter capacity is limited to 0.25 pu, and the initial grid-side reactive power is 0.03 pu. It is worth noting that the per-unit power rating for wind farms is their rated power; air density... The concentration is 1.295 kg / m³. The wind turbine participates in grid frequency regulation using integrated inertial control, and the control parameters are: , The system simulation diagram is as follows: Figure 6 As shown.

[0047] Step 3-2: To visually observe the effect of wind turbine inertia response on system frequency stability, a 75% thermal power ratio was selected as the research object. An experimental group with wind turbine inertia support function disabled and a control group with wind turbine inertia control retained under different wind speeds were set up to verify the frequency regulation effect of wind turbine inertia response. To illustrate the correctness of the proposed effect of wind speed on wind turbine inertia in this implementation method, a comparative experiment with different wind speeds was first designed. The rated wind speed of the wind turbine was set to 13 m / s. Wind speeds of 13 m / s and 7 m / s with and without inertia response control were compared. The results were then compared with the system frequency and wind turbine inertia response output of the system without inertia response control under the same disturbance. At times, disturbances occur. The system frequency changes are as follows Figure 7 As shown.

[0048] Step 3-3: As shown in the figure, in the wind turbine system with inertial response control, the lowest system frequency after a disturbance is 49.832 Hz when the simulated wind speed is 13 m / s, and 49.811 Hz when the wind speed is 7 m / s. The lowest system frequency under the influence of disturbance in the system without inertial response control is 49.807 Hz. The simulation results show that comparing the system frequency changes after disturbances at wind speeds of 13 m / s and 7 m / s with the results of the system without inertial control, it can be concluded that setting inertial response control on the wind turbine is beneficial to system frequency stability. Furthermore, the effect of wind turbines operating under rated wind speed conditions on system frequency stability is better than that of wind-thermal hybrid systems operating below rated wind speeds. Simulations under different wind speed conditions yielded Table 1. The results in the table show the changes in wind turbine inertia under different wind speeds.

[0049]

[0050] Steps 3-4: Taking the unbalanced power at the time of disturbance as 10% of the system load, the derived critical proportion of thermal power is 44.90%. Simulation verification is then performed on systems with different thermal power ratios. The total active load of the system is 6150 MW, the system reserve capacity is 15%, all composed of thermal power units, and the actual wind power output is 50% of its installed capacity. Table 2 shows the unit replacement situation and the output of each unit under different thermal power ratios. The system frequency change rate at the time of disturbance is as follows: Figure 8 As shown.

[0051]

[0052] Steps 3-5: Based on simulation results Figure 8It can be seen that when the proportion of thermal power is 45%, the system RoCoF reaches 0.963 Hz / s at the moment of disturbance, which is within the safety threshold of 1 Hz / s. The calculation error is due to factors such as the different distances between the power deficit port and each generator caused by the complex simulation system, which affects the spatial distribution characteristics of the system frequency stability. However, it can still be concluded that the critical proportion of thermal power is slightly lower than 45%. Therefore, under the boundary conditions given in Section 2, the conclusion that the critical proportion of thermal power is 44.90% is credible.

[0053] Steps 3-6: Next, verify whether the system frequency change rate of the entire wind power system conforms to the theoretical derivation when the unbalanced power is 5% of the system load. The simulation results are as follows: Figure 9 As shown.

[0054] Steps 3-7: From Figure 9 It can be seen that when the system consists entirely of wind turbines, the system RoCoF reaches its lowest point of 0.922 Hz / s at the moment of disturbance, satisfying the system frequency change rate constraint. The maximum frequency change rate after the disturbance is very close to 1 Hz / s, thus verifying the theoretically derived... The rationality is demonstrated by the fact that, compared to systems with larger unbalanced power but containing thermal power units, the frequency decrease rate is more pronounced from 10 s to 10.2 s, exhibiting the system's low inertia characteristics. Combined with the aforementioned verification, it can be seen that when the boundary conditions change, substituting the corresponding conditions into the thermal power critical ratio solution formula yields the appropriate result, proving the rationality of the derivation. The inability of RoCoF to converge to 0 after 10.2 s in the simulation is because the all-wind turbine system lacks the primary frequency regulation function of a traditional power system, preventing the system frequency from maintaining long-term stability. RoCoF constraints can only be achieved in the initial stage of disturbance under the support of the wind turbine inertia response.

[0055] In summary, this invention, by comparing the output of wind turbines with inertial response control and those with only MPPT control during system disturbances, as well as the frequency changes of the systems affected by disturbances, verifies that wind turbines utilizing their own rotor kinetic energy to participate in system frequency regulation under inertial response control has a positive effect on system frequency stability. Furthermore, this invention proposes a critical proportion for thermal power units based on RoCoF constraints from an inertial perspective, which is more intuitive than the system critical inertia index and is beneficial for dispatchers to monitor and maintain the safety and stability of the power system.

[0056] It should be emphasized that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A method for determining the critical proportion of thermal power in a power system with high wind power penetration, characterized in that, Includes the following steps: Step 1: Establish a wind turbine inertia assessment model that takes into account wind speed fluctuations; Step 2: Derive the system's critical thermal power ratio based on RoCoF constraints; Step 3: Simulation verification.

2. The method for determining the critical thermal power ratio in a power system with high wind power penetration according to claim 1, characterized in that, In step 1, the frequency domain expression of the equivalent inertia of the wind turbine is: The time-domain expression for the equivalent inertia of the wind turbine is: ;in, Frequency domain representation of the equivalent inertia of a wind turbine. The time-domain representation of the equivalent inertia of the wind turbine. This represents the differential coefficient for virtual inertia control. This represents the proportional coefficient for virtual inertia control. Indicates the initial speed of the fan. Indicates the initial synchronization angular velocity of the system. Indicates the filter time constant. Let represent a complex frequency domain operator, and t represent time.

3. The method for determining the critical thermal power ratio in a power system with high wind power penetration according to claim 1, characterized in that, In step 1, the equivalent inertia of a wind turbine under actual wind speed conditions is: In the formula, This indicates the rated capacity of the corresponding fan. This represents the kinetic energy loss of the wind turbine rotor during the inertial response phase. This represents the equivalent inertia of a wind turbine under actual wind speed conditions. Indicates air density, Indicates the area swept by the blade. The time-varying function representing the wind energy utilization coefficient as a function of time t. Indicates the pitch angle. Indicates wind speed. This indicates the mechanical power of the fan before the disturbance occurred. , These represent the start and end points of time t, respectively.

4. The method for determining the critical thermal power ratio in a power system with high wind power penetration according to claim 1, characterized in that, In step 2, the critical power generation ratio of the thermal power unit is: in, This indicates the critical power generation ratio of thermal power units. This represents the constraint on the maximum rate of change of the system's frequency. This represents the unbalanced power of the system at time t. Indicates the system frequency. This refers to the rated capacity of newly built wind turbines when replacing thermal power generators with wind turbines. With the rated capacity of the replaced thermal power generator Relationship, Indicates the inertia between wind turbine units. Indicates the system's reserve capacity. This represents the inertia between thermal power units.

5. The method for determining the critical thermal power ratio in a power system with high wind power penetration according to claim 4, characterized in that, In step 2, when hour, If the result of the expression is less than or equal to 0 or greater than 1, then the entire system consists of wind turbines controlled by additional inertia; where, This indicates the maximum value of the RoCoF constraint. This indicates the system load.

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