Wind turbine generator set variable climbing frequency modulation strategy considering kinetic parameters and frequency modulation requirements

Abstract

The invention provides a wind turbine generator set variable climbing frequency modulation strategy considering kinetic parameters and frequency modulation requirements. Firstly, in the frequency modulation response stage of the wind turbine generator, the active climbing absolute value upper limit of the frequency modulation response stage of the wind turbine generator is dynamically adjusted based on the kinetic parameter of the bending fatigue life margin of a transmission chain of the wind turbine generator and the frequency modulation requirement of the active climbing absolute value of the wind turbine generator in the frequency modulation response stage expected by an electric power system. Secondly, in the frequency modulation recovery stage of the wind turbine generator, the optimal active climbing absolute value of the frequency modulation recovery stage of the wind turbine generator is solved based on the kinetic parameter of the rotor speed of the wind turbine generator and by considering the frequency modulation requirement that the power system hopes that the active climbing absolute value of the wind turbine generator is as small as possible in the frequency modulation recovery stage; according to the method, the wind turbine generator frequency modulation process meets the system frequency modulation requirement, meanwhile, bending fatigue damage of the wind turbine generator is reduced, and the rotating speed of the wind turbine generator is stable.

Description

Technical Field

[0001] The present invention relates to the field of wind turbine power control, and in particular to a variable ramp frequency regulation strategy for wind turbines that takes dynamic parameters and frequency regulation requirements into consideration. Background Art

[0002] The continuous increase in installed wind turbine capacity has led to an increasingly significant adverse impact on power system frequency stability. On the one hand, the uncertainty of wind turbine active power output leads to more frequent and severe fluctuations in the power system's active power supply and demand, resulting in more frequent and severe deviations from the rated power system frequency. On the other hand, the increasing proportion of installed wind turbine capacity has led to a continuous decline in the installed capacity of conventional synchronous generators, which provide frequency regulation services and inertia support. This has led to a continuous decrease in the power system's overall equivalent frequency regulation capacity and equivalent inertia. To improve power system frequency stability and quality, it is inevitable that wind turbines will participate in power system frequency regulation, just like conventional energy sources.

[0003] Depending on the source of frequency regulation energy, wind turbine frequency regulation strategies can be categorized as rotor kinetic energy control-based frequency regulation strategies, rotor speed control-based frequency regulation strategies, variable pitch control-based frequency regulation strategies, energy storage control-based frequency regulation strategies, supercapacitor control-based frequency regulation strategies, and a combination of these strategies. Wind turbines employing rotor speed control and variable pitch control frequency regulation strategies achieve frequency regulation by varying the rotor speed and pitch angle during frequency regulation, thereby altering the wind turbine's active power output. This strategy offers the advantage of maintaining frequency regulation for extended periods of time. However, it requires reducing active power during daily operation through speed and pitch control to reserve reserve capacity for frequency regulation, which reduces the wind turbine's power generation revenue. When frequency regulation is achieved through energy storage control or supercapacitor control, the advantage is that frequency regulation can be maintained for extended periods of time without requiring a reduction in active power during daily operation. However, it requires the deployment of energy storage and supercapacitors, increasing the wind farm's investment and operation and maintenance costs.

[0004] The frequency regulation strategy for wind turbines based on rotor kinetic energy control is also known as the inertia control strategy. The basic idea is that when the power system frequency is normal, the wind turbine outputs active power in a maximum power point tracking mode. When the power system frequency deviates from the rated value, the wind turbine uses the rotor to release or absorb kinetic energy, thereby changing the wind turbine's active power to achieve frequency regulation. This phase is called the frequency response phase. When the wind turbine completes the frequency response task, it is necessary to restore the rotor speed to the optimal rotor speed to continue achieving maximum power point tracking. This phase is called the frequency recovery phase. Depending on the active power reference given during the wind turbine frequency response phase, the inertia control strategy can be further divided into step inertia control, torque limit inertia control, integrated inertia control, and optimal inertia control. Among them, the step inertia control strategy sets the active reference of the wind turbine during frequency regulation to a fixed value. The active reference of the wind turbine during frequency regulation set in the torque limit inertia control strategy will make the wind turbine just reach the torque limit. The comprehensive inertia control strategy substitutes the system frequency information into a predetermined formula to calculate the active reference of the wind turbine during frequency regulation. The optimal inertia control optimizes the active reference of the wind turbine during frequency regulation as a decision variable.

[0005] Extensive research has examined methods for regulating active power and setting active power references during wind turbine frequency regulation, but little attention has been paid to active power ramp control during wind turbine frequency regulation. For wind turbines using a comprehensive inertia control strategy for frequency regulation, if the upper limit of the active power ramp during the frequency response phase is too small, the active power may not adjust quickly to frequency fluctuations, thus affecting the frequency regulation effect. If the upper limit of the active power ramp during the frequency response phase is too large, the active power may change rapidly, leading to significant torque fluctuations in the transmission chain, which can cause significant bending fatigue damage to the wind turbine transmission chain. To recover the speed deviation caused by the frequency response phase, the active power change trend during the wind turbine frequency recovery phase is opposite to that during the frequency response phase. Therefore, the active power change during the wind turbine frequency recovery phase is detrimental to system frequency recovery. A larger absolute value of the active power ramp during the frequency recovery phase increases the adverse effect on system frequency. However, if the absolute value of the active power ramp during the frequency regulation recovery phase of the wind turbine is too small, the active power cannot be changed from the frequency regulation response state to the speed recovery state in time, and the speed may not be able to recover in time, resulting in a loss of speed stability.

[0006] Therefore, appropriate active power ramping absolute values ​​or upper limits should be set for wind turbines at different stages and under different conditions. Specifically, during the frequency response phase, when the system frequency change rate increases, the power system expects the wind turbine to have a larger upper limit on the active power ramping absolute value so that it can quickly track the system frequency and adjust the active power. Conversely, the wind turbine does not need a large upper limit on the active power ramping absolute value. A larger bending fatigue life margin for the wind turbine drive train indicates that the wind turbine drive train can withstand greater torque fluctuations, thus allowing the wind turbine to have a larger upper limit on the active power ramping absolute value. Conversely, a smaller upper limit on the active power ramping absolute value should be set for the wind turbine. Therefore, during the frequency response phase, the dynamic parameter of the wind turbine drive train bending fatigue life margin and the power system's desired absolute value of the wind turbine active power ramping absolute value during the frequency response phase should be considered to dynamically adjust the upper limit on the active power ramping absolute value of the wind turbine. During the frequency regulation recovery phase, the power system aims to minimize the absolute value of the wind turbine's active power ramp during this phase. This minimizes the impact of active power changes on the system frequency. However, if the wind turbine's active power ramp is too small, its speed may not recover in time, leading to speed instability. Therefore, while ensuring rotor speed safety, the wind turbine's minimum absolute value of active power ramp should be determined as the absolute value of its active power ramp during the frequency regulation recovery phase.

[0007] In the invention patent application number 202311534106.5, the inventor disclosed an optimal control strategy for wind power frequency regulation based on gradual inertia control. The steps are: first, introduce a power transition phase between the frequency response phase and the frequency recovery phase of the wind turbine; second, solve the active power reference of the wind turbine during the power transition phase with the goal of maintaining the system frequency unchanged. This method sets an appropriate active power reference to avoid system frequency deterioration caused by excessive absolute values ​​of active power ramping during the transition phase and the frequency recovery phase. However, this method does not consider the safety of the wind turbine rotor speed when setting the active power reference. Improper active power reference setting may cause the absolute values ​​of active power ramping of the wind turbine during the transition phase and the frequency recovery phase to be too small, which may cause the wind turbine rotor speed to lose stability. The invention patent with application number 202311612789.1 discloses a method and system for energy storage control to assist wind power in participating in the primary frequency regulation of the power grid. This method determines the primary frequency regulation demand of the power grid for the wind power generation system based on the rated installed power of the wind power generation system, but this method does not consider the control of the ramping of the wind turbine during the frequency regulation period. The invention patent with application number 202010121561.2 proposes a method for frequency regulation of wind turbines that takes into account the fatigue load of the unit. This method limits the torque of the wind turbine during the frequency regulation period based on the fatigue life of the wind turbine, effectively reducing the fatigue load of the main shaft of the wind turbine. The invention patent with application number 202010398633.8 proposes a frequency regulation control method for a speed-increasing wind turbine, which can suppress the active power change rate during the process of the wind turbine participating in the primary frequency regulation of the power grid, thereby suppressing the thrust fluctuation of the wind rotor and the torque fluctuation of the transmission system, and thus reducing the fatigue load of the speed-increasing wind turbine. However, the above two invention patents do not take into account the frequency regulation requirement of the system power system, that is, the absolute value of the active power ramp of the wind turbine in the frequency regulation response stage. Therefore, the frequency regulation effect of the wind turbine may not meet the system requirements. Summary of the Invention

[0008] In order to make up for the deficiencies in the existing research on wind turbine frequency regulation control methods, the present invention proposes a variable ramp frequency regulation strategy for wind turbines that takes into account dynamic parameters and frequency regulation requirements. The strategy is based on the identification results of the wind turbine dynamic parameters and the analysis results of the power system's frequency regulation requirements for the wind turbine. In the frequency regulation response stage, the upper limit of the absolute value of the active ramp of the wind turbine is dynamically adjusted, and in the frequency regulation recovery stage, the absolute value of the active ramp of the wind turbine is optimized, so that the frequency regulation process of the wind turbine meets the system frequency regulation requirements while reducing the bending fatigue damage of the wind turbine and ensuring the stability of the wind turbine speed.

[0009] The present invention discloses a variable ramp frequency modulation strategy for wind turbines that takes into account dynamic parameters and frequency modulation requirements, and the steps include: Step S1: During the frequency modulation response phase of the wind turbine generator, based on the dynamic parameter of the wind turbine generator transmission chain bending fatigue life margin and the frequency modulation requirement of the power system, the upper limit of the absolute value of the active power ramp of the wind turbine generator during the frequency modulation response phase is dynamically adjusted. The wind turbine generator controls the active power to modulate the power system frequency under the constraint of the changing upper limit of the active power ramp. Step S2: During the frequency regulation recovery phase of the wind turbine, based on the dynamic parameter of the wind turbine rotor speed and taking into account the frequency regulation requirement of the power system that the absolute value of the active power ramp of the wind turbine during the frequency regulation recovery phase is as small as possible, the optimal absolute value of the active power ramp during the frequency regulation recovery phase of the wind turbine is solved. The wind turbine controls the active power with the optimal absolute value of the active power ramp to recover the speed of the unit.

[0010] In step S1, when dynamically adjusting the upper limit of the absolute value of the active power ramp during the frequency regulation response phase of the wind turbine generator set, the upper limit of the absolute value of the active power ramp during the frequency regulation response phase of the wind turbine generator set is set using fuzzy logic, including the following steps: Step S1-1: Based on the existing wind turbine transmission chain bending fatigue damage measurement technology, the wind turbine transmission chain bending fatigue damage is obtained and normalized; the wind turbine transmission chain bending fatigue life margin, a dynamic parameter denoted as F, is obtained by subtracting the wind turbine transmission chain bending fatigue damage from 1, and is identified, normalized, and fuzzified in real time, and divided into 9 fuzzy sets, including {very small (VS), medium small (MS), small (S), relatively small (LS), medium (M), relatively large (LL), large (L), medium large (ML), and extremely large (VL)}; Step S1-2: The frequency regulation demand of the wind turbines in the power system during the frequency regulation response phase is recorded as |V|. This demand is measured by the absolute value of the power system frequency change rate obtained by real-time measurement. This demand is normalized and fuzzified in real time and divided into seven fuzzy sets, including {Vs, MS, S, M, L, ML, VL}. Step S1-3: The upper limit of the absolute value of the active power ramp during the frequency regulation response phase of the wind turbine is denoted as |G|, which is normalized and fuzzified and divided into eight fuzzy sets, including {very small (VS), medium small (MS), small (S), relatively small (LS), medium (M), large (L), medium large (ML), and very large (VL)}; Step S1-4: Based on the two experiences that the larger the bending fatigue life margin of the wind turbine transmission chain, the larger the upper limit of the absolute value of the active power climbing of the wind turbine should be set, and the larger the absolute value of the active power climbing of the wind turbine desired by the power system in the frequency regulation response stage is, the larger the upper limit of the absolute value of the active power climbing of the wind turbine should be set, the fuzzy logic of the upper limit of the absolute value of the active power climbing of the wind turbine is obtained from the dynamic parameter of the bending fatigue life margin of the wind turbine transmission chain and the frequency regulation requirement of the absolute value of the active power climbing of the wind turbine desired by the power system in the frequency regulation response stage is as shown in Table 1 below.

[0011] Table 1. Fuzzy logic for the absolute upper limit of active power ramping of wind turbines

[0012] Among them, when solving the optimal active power ramp absolute value of the wind turbine generator set during the frequency regulation recovery phase in step S2, the active power ramp absolute value of the wind turbine generator set during the frequency regulation recovery phase is used as the optimization variable, which is recorded as |K| By establishing the optimization objective and constraint conditions, the optimal active power ramp absolute value of the wind turbine frequency recovery stage is solved, which is recorded as |K| opt , including the following steps: Step S2-1: Considering the power system's frequency regulation requirement that the absolute value of the active power ramp of the wind turbine generator set during the frequency regulation recovery phase be as small as possible, the optimization objective is to minimize the absolute value of the active power ramp of the wind turbine generator set during the frequency regulation recovery phase, as shown in the following formula: (1) Step S2-2: Considering that the wind turbine rotor speed is a dynamic parameter with a safe range, the constraint conditions include the relationship between the absolute value of the active power ramp during the wind turbine frequency modulation recovery phase and the wind turbine rotor speed, a dynamic parameter, and that the wind turbine rotor speed does not exceed its safe range, as shown in the following formula: (2) In the above formula, t For time, tr is the start time of the wind turbine frequency regulation recovery phase, td is the end time of the wind turbine frequency regulation recovery phase, is the active power reference of the wind turbine, Active reference for maximum power point tracking of wind turbines, Fixed parameters for maximum power point tracking of wind turbines, is the wind turbine rotor speed, For wind turbines tr The rotor speed at the moment, is the moment of inertia of the wind turbine, is the actual active power of the wind turbine, For wind turbines tr Always be practical, is the power system frequency deviation, is the wind turbine rotor speed change rate, J is the moment of inertia of the wind turbine, Wind energy capture for wind turbines, is the lower limit of the safe range of wind turbine rotor speed, is the upper limit of the safe range of the wind turbine rotor speed; when =0, the wind turbine does not need frequency regulation, so the above formula does not take into account =0; Step S2-3: Based on the optimization objectives and constraints described in steps S2-1 and S2-2, the optimal active power ramp absolute value in the frequency regulation recovery phase of the wind turbine generator is solved.

[0013] Compared to the closest existing technology, the variable ramp frequency regulation strategy for wind turbines proposed in this invention, which considers dynamic parameters and frequency regulation requirements, takes into account the impact of the absolute value of wind turbine ramps on the power system frequency regulation effect, fatigue damage to wind turbines, and the stability of wind turbine rotor speed. It innovatively proposes a method for dynamically setting the absolute value of wind turbine ramps based on wind turbine dynamic parameters and power system frequency regulation requirements. Therefore, the technical solution provided by this invention has the following beneficial effects: 1) The wind turbine variable ramp frequency regulation strategy proposed in this invention, which considers dynamic parameters and frequency regulation requirements, is based on the dynamic parameter of the wind turbine transmission chain bending fatigue life margin and the power system's desired frequency regulation requirement of the wind turbine's absolute active power ramp during the frequency regulation response phase. Fuzzy logic is used to dynamically adjust the upper limit of the wind turbine's absolute active power ramp during the frequency regulation response phase. When the power system frequency change rate is large and the power system expects the wind turbine to quickly adjust the active power to support the system frequency, the upper limit of the wind turbine's absolute active power ramp will be adjusted to a larger value. When the wind turbine transmission chain has significant bending fatigue damage and cannot withstand large torque mutations, the upper limit of the wind turbine's absolute active power ramp will be adjusted to a smaller value. Therefore, this solution ensures that the wind turbine frequency regulation process meets the power system's frequency regulation requirements while reducing wind turbine fatigue damage.

[0014] 2) The proposed wind turbine variable ramp frequency regulation strategy, which considers dynamic parameters and frequency regulation requirements, is based on the wind turbine rotor speed as a dynamic parameter and takes into account the power system's frequency regulation requirement of minimizing the absolute value of the wind turbine's active power ramp during the frequency recovery phase. The optimal absolute value of the wind turbine's active power ramp during the frequency recovery phase is calculated, and the wind turbine controls its active power using this optimal absolute value to restore the unit's speed. This strategy minimizes the absolute value of the wind turbine's active power ramp during the frequency recovery phase while ensuring the safety of the wind turbine's rotor speed. This strategy minimizes the adverse effects of active power variations on the system frequency during the frequency recovery phase while ensuring the safety of the wind turbine's rotor speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is the active reference for actual active power, wind energy capture, and maximum power point tracking during wind turbine frequency regulation.

[0016] Figure 2 This is a block diagram of the steps of the variable ramp frequency regulation strategy for wind turbines taking into account dynamic parameters and frequency regulation requirements in the present invention.

[0017] Figure 3 Represents the actual active power changes of wind turbines during frequency regulation under four simulation scenarios.

[0018] Figure 4 Represents the frequency changes of the power system during frequency regulation under four simulation scenarios. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solutions and advantages of this application more clear, the following further describes this application in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0020] When a wind turbine adopts a comprehensive inertia control strategy for frequency regulation, the active power reference during the frequency regulation response period is as follows: (3) In the above formula, tf is the start time of the frequency regulation response phase of the wind turbine, tr It is the end time of the frequency response phase of the wind turbine (also the start time of the frequency recovery phase). is the active power reference of the wind turbine, Active reference for maximum power point tracking of wind turbines, It is the reference change of active power during the frequency regulation response period when the wind turbine adopts the comprehensive inertia control strategy for frequency regulation. T J is the equivalent inertia time constant of the wind turbine, It is the frequency regulation ratio coefficient when the wind turbine adopts the comprehensive inertia control strategy for frequency regulation. f N is the rated frequency of the power system, is the power system frequency deviation, df / dt is the rate of change of power system frequency. It is the active power of the wind turbine at the beginning of the frequency regulation response phase of the wind turbine.

[0021] It can be seen that the greater the rate of change of the system frequency, the The faster the change, the faster the active power reference of the wind turbine during the frequency regulation period changes, and the greater the upper limit of the absolute value of the active power ramp of the wind turbine in the frequency regulation response stage that the power system expects. In this way, the actual active power of the wind turbine can track the active power reference faster and more accurately, and better regulate the frequency of the power system.

[0022] The motion equation of the wind turbine transmission chain is shown as follows: (4) In the above formula, is the moment of inertia of the wind turbine, is the wind turbine rotor speed change rate, is the mechanical torque of the wind turbine, is the electrical torque of the wind turbine, Wind energy capture for wind turbines, is the actual active power of the wind turbine, is the wind turbine rotor speed.

[0023] It can be seen that the larger the absolute upper limit of the wind turbine's active power ramping, the faster the wind turbine's active power changes, the faster the torque mutation on the wind turbine's drive chain, and the greater the bending fatigue damage to the wind turbine's drive chain. Therefore, when the wind turbine's drive chain's bending fatigue life is long, the wind turbine can withstand a larger absolute upper limit of the active power ramping. When the wind turbine's drive chain's bending fatigue life is short, the absolute upper limit of the wind turbine's active power ramping should be reduced.

[0024] Therefore, the upper limit of the absolute value of the active power ramp of the wind turbine during the frequency response period should be dynamically set by comprehensively considering the dynamic parameter of the wind turbine transmission chain bending fatigue life margin and the frequency regulation requirement of the power system, namely the absolute value of the active power ramp of the wind turbine during the frequency response stage.

[0025] Taking the power system frequency drop as an example, when the wind turbine adopts the integrated inertia control strategy to adjust the frequency, the actual active power (i.e. ), wind energy capture (i.e. ), the active reference of maximum power point tracking (i.e. )like Figure 1As shown. It can be seen that the wind turbine generator system is in the frequency response period (i.e. tf-tr ) Active power increases to prevent the system frequency from dropping. At this time, the actual active power of the wind turbine is greater than the wind energy captured, resulting in a decrease in rotor speed. During the frequency regulation recovery period (i.e. tr-td ) Wind turbines need to reduce their actual active power so that it is less than the wind energy captured to restore the rotor speed. The decrease in active power during the frequency modulation recovery phase will cause the system frequency to drop again. The greater the slope of active power decrease, the more severe the system frequency drop. Therefore, during the frequency modulation recovery phase of wind turbines, the power system hopes that the slope of active power decrease during the frequency modulation recovery phase of wind turbines is as small as possible. However, if Figure 1 As shown in the figure, if the active power of the wind turbine is too low during the frequency modulation recovery phase, the actual active power of the wind turbine will decrease too slowly, which will cause the actual active power to be unable to fall below the wind energy capture. The wind turbine rotor speed will continue to decrease and cannot be recovered, and the wind turbine rotor may lose stability.

[0026] Therefore, during the frequency modulation recovery period, the absolute value of the wind turbine active power ramp should be reduced as much as possible while ensuring the safety of the rotor speed.

[0027] Based on the above analysis, if Figure 2 As shown, the present invention discloses a variable ramp frequency regulation strategy for wind turbines that considers dynamic parameters and frequency regulation requirements. The method is characterized in that, based on the identification results of the dynamic parameters of the wind turbine and the analysis results of the frequency regulation requirements of the power system for the wind turbine, the upper limit of the absolute value of the active ramp of the wind turbine is dynamically adjusted in the frequency regulation response phase and the absolute value of the active ramp of the wind turbine is optimized in the frequency regulation recovery phase, so that the frequency regulation process of the wind turbine meets the frequency regulation requirements of the system while reducing the bending fatigue damage of the wind turbine and ensuring the stability of the speed of the wind turbine. The steps include: Step S1: During the frequency modulation response phase of the wind turbine generator, based on the dynamic parameter of the wind turbine generator transmission chain bending fatigue life margin and the frequency modulation requirement of the power system, the upper limit of the absolute value of the active power ramp of the wind turbine generator during the frequency modulation response phase is dynamically adjusted. The wind turbine generator controls the active power to modulate the power system frequency under the constraint of the changing upper limit of the active power ramp. Step S2: During the frequency regulation recovery phase of the wind turbine, based on the dynamic parameter of the wind turbine rotor speed and taking into account the frequency regulation requirement of the power system that the absolute value of the active power ramp of the wind turbine during the frequency regulation recovery phase is as small as possible, the optimal absolute value of the active power ramp during the frequency regulation recovery phase of the wind turbine is solved. The wind turbine controls the active power with the optimal absolute value of the active power ramp to recover the speed of the unit.

[0028] In step S1, when dynamically adjusting the upper limit of the absolute value of the active power ramp during the frequency regulation response phase of the wind turbine generator set, the upper limit of the absolute value of the active power ramp during the frequency regulation response phase of the wind turbine generator set is set using fuzzy logic, including the following steps: Step S1-1: Based on the existing wind turbine transmission chain bending fatigue damage measurement technology, the wind turbine transmission chain bending fatigue damage is obtained and normalized; the wind turbine transmission chain bending fatigue life margin, a dynamic parameter denoted as F, is obtained by subtracting the wind turbine transmission chain bending fatigue damage from 1, and is identified, normalized, and fuzzified in real time, and divided into 9 fuzzy sets, including {very small (VS), medium small (MS), small (S), relatively small (LS), medium (M), relatively large (LL), large (L), medium large (ML), and extremely large (VL)}; Step S1-2: The frequency regulation demand of the wind turbines in the power system during the frequency regulation response phase is recorded as |V|. This demand is measured by the absolute value of the power system frequency change rate obtained by real-time measurement. This demand is normalized and fuzzified in real time and divided into seven fuzzy sets, including {Vs, MS, S, M, L, ML, VL}. Step S1-3: The upper limit of the absolute value of the active power ramp during the frequency regulation response phase of the wind turbine is denoted as |G|, which is normalized and fuzzified and divided into eight fuzzy sets, including {very small (VS), medium small (MS), small (S), relatively small (LS), medium (M), large (L), medium large (ML), and very large (VL)}; Step S1-4: Based on the two experiences that the larger the bending fatigue life margin of the wind turbine transmission chain, the larger the upper limit of the absolute value of the active power climbing of the wind turbine should be set, and the larger the absolute value of the active power climbing of the wind turbine desired by the power system in the frequency regulation response stage is, the larger the upper limit of the absolute value of the active power climbing of the wind turbine should be set, the fuzzy logic of the upper limit of the absolute value of the active power climbing of the wind turbine is obtained from the dynamic parameter of the bending fatigue life margin of the wind turbine transmission chain and the frequency regulation requirement of the absolute value of the active power climbing of the wind turbine desired by the power system in the frequency regulation response stage is as shown in the following table.

[0029] Table 1. Fuzzy logic for the upper limit of active power ramp of wind turbines

[0030] Based on the above fuzzy logic, it can be seen that when the power system frequency is changing rapidly and the power system requires the wind turbine to quickly adjust its active power to support the system frequency, the absolute upper limit of the wind turbine's active power ramping will be adjusted to a larger value. When the wind turbine's drive train suffers from severe bending fatigue damage and cannot withstand large torque changes, the absolute upper limit of the wind turbine's active power ramping will be adjusted to a smaller value. Therefore, this solution ensures that the wind turbine frequency regulation process meets the power system's frequency regulation requirements while reducing wind turbine fatigue damage.

[0031] Among them, when solving the optimal active power ramp absolute value of the wind turbine generator set during the frequency regulation recovery phase in step S2, the active power ramp absolute value of the wind turbine generator set during the frequency regulation recovery phase is used as the optimization variable, which is recorded as |K| By establishing the optimization objective and constraint conditions, the optimal active power ramp absolute value of the wind turbine frequency recovery stage is solved, which is recorded as |K| opt , including the following steps: Step S2-1: Considering the power system's frequency regulation requirement that the absolute value of the active power ramp of the wind turbine generator set during the frequency regulation recovery phase be as small as possible, the optimization objective is to minimize the absolute value of the active power ramp of the wind turbine generator set during the frequency regulation recovery phase, as shown in the following formula: (1) Step S2-2: Considering that the wind turbine rotor speed is a dynamic parameter with a safe range, the constraint conditions include the relationship between the absolute value of the active power ramp during the wind turbine frequency modulation recovery phase and the wind turbine rotor speed, a dynamic parameter, and that the wind turbine rotor speed does not exceed its safe range, as shown in the following formula: (2) In the above formula, t For time, tr is the start time of the wind turbine frequency regulation recovery phase, td is the end time of the wind turbine frequency regulation recovery phase, is the active power reference of the wind turbine, Active reference for maximum power point tracking of wind turbines, Fixed parameters for maximum power point tracking of wind turbines, is the wind turbine rotor speed, is the moment of inertia of the wind turbine, For wind turbines tr The rotor speed at the moment, is the actual active power of the wind turbine, For wind turbines tr Always be practical, is the power system frequency deviation, is the wind turbine rotor speed change rate, J is the moment of inertia of the wind turbine, Wind energy capture for wind turbines, is the lower limit of the safe range of wind turbine rotor speed, is the upper limit of the safe range of the wind turbine rotor speed; when =0, the wind turbine does not need frequency regulation, so the above formula does not take into account =0; Step S2-3: Based on the optimization objectives and constraints described in steps S2-1 and S2-2, the optimal active power ramp absolute value in the frequency regulation recovery phase of the wind turbine generator is solved.

[0032] It can be seen that this scheme minimizes the absolute value of the active power ramp of the wind turbine during the frequency regulation recovery stage while ensuring the safety of the wind turbine rotor speed. That is, it minimizes the adverse impact of the active power change of the wind turbine during the frequency regulation recovery stage on the system frequency while ensuring the safety of the wind turbine rotor speed.

[0033] In order to verify the variable ramp frequency regulation strategy of wind turbines considering dynamic parameters and frequency regulation requirements proposed in the present invention, four scenarios were simulated and compared.

[0034] Scenario 1: The wind turbine does not perform frequency regulation.

[0035] Scenario 2: The wind turbine is frequency-regulated, and the upper limit of its active and reactive power ramping absolute value is fixed and large.

[0036] Scenario 3: The wind turbine performs frequency regulation, and the upper limit of the absolute value of its active and reactive power ramp is fixed and small.

[0037] Scenario 4: Wind turbines are frequency regulated. The variable ramp frequency regulation strategy for wind turbines proposed in the present invention that considers dynamic parameters and frequency regulation requirements is adopted. The upper limit of the absolute value of the active power ramp is dynamically adjusted in the frequency regulation response phase, and the absolute value of the active power ramp is optimized in the frequency regulation recovery phase.

[0038] The scene results are as follows Figure 3 and Figure 4 As shown, Figure 3 Represents the actual active power changes of wind turbines during frequency regulation under four scenarios, Figure 4The following table represents the power system frequency changes under four scenarios. As can be seen, in Scenario 1, wind turbines do not perform frequency regulation, and their active power output remains unchanged during the power system frequency disturbance. The lowest power system frequency in this scenario is the lowest among the four scenarios. In Scenario 2, the wind turbines have a large and fixed upper limit for active power ramping. Therefore, their active power can increase rapidly during the frequency response phase and can track system frequency changes in real time to adjust their active power output, thus preventing a drop in system frequency. The lowest system frequency in Scenario 2 is improved compared to Scenario 1. However, in Scenario 2, the wind turbines' active power decreases rapidly during the frequency recovery phase, causing a secondary frequency drop in the power system, which affects the frequency regulation effect. In Scenario 3, the wind turbines have a small and fixed upper limit for active power ramping, and their active power decreases slowly during the frequency recovery phase, preventing a secondary frequency drop in the power system. However, their active power increases and changes slowly during the frequency response phase, affecting the frequency regulation effect, resulting in a lower lowest power system frequency than in Scenario 2. In Scenario 4, the absolute upper limit of the wind turbine's active power ramp during the frequency response phase is adaptively adjusted based on system requirements and turbine dynamic parameters. This upper limit satisfies the wind turbine's frequency regulation requirements, rapidly increasing active power and enabling real-time tracking and adjustment of active power output to system frequency changes. This prevents a decrease in power system frequency. Consequently, the system's lowest frequency point in Scenario 4 is larger than in Scenarios 1 and 3. In Scenario 4, the absolute upper limit of the wind turbine's active power ramp during the frequency recovery phase is optimized based on system requirements and turbine dynamic parameters. Active power decreases slowly, preventing a secondary frequency dip. Consequently, Scenario 4 achieves the best overall frequency regulation, both increasing the lowest system frequency point and preventing a secondary frequency dip.

[0039] The above-described embodiments are merely illustrative of the technical solutions of the present invention and should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art may make various modifications and improvements without departing from the spirit of the present application, and these modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A variable ramp frequency regulation strategy for wind turbines considering dynamic parameters and frequency regulation requirements is characterized by: The strategy is based on the identification results of wind turbine dynamic parameters and the analysis results of the power system's frequency regulation requirements for wind turbines. It dynamically adjusts the upper limit of the wind turbine's active power ramping absolute value during the frequency regulation response phase and optimizes the wind turbine's active power ramping absolute value during the frequency regulation recovery phase. This ensures that the wind turbine frequency regulation process meets the system frequency regulation requirements while reducing bending fatigue damage to the wind turbine and ensuring stable wind turbine speed. The strategy specifically includes the following steps: Step S1: During the frequency modulation response phase of the wind turbine generator, based on the dynamic parameter of the wind turbine generator transmission chain bending fatigue life margin and the frequency modulation requirement of the power system, the upper limit of the absolute value of the active power ramp of the wind turbine generator during the frequency modulation response phase is dynamically adjusted. The wind turbine generator controls the active power to modulate the power system frequency under the constraint of the changing upper limit of the active power ramp. Step S2: During the frequency regulation recovery phase of the wind turbine, based on the dynamic parameter of the wind turbine rotor speed and taking into account the frequency regulation requirement of the power system that the absolute value of the active power ramp of the wind turbine during the frequency regulation recovery phase is as small as possible, the optimal absolute value of the active power ramp during the frequency regulation recovery phase of the wind turbine is solved. The wind turbine controls the active power with the optimal absolute value of the active power ramp to recover the speed of the unit.

2. The variable ramp frequency modulation strategy for wind turbines considering dynamic parameters and frequency modulation requirements according to claim 1 is characterized in that: When dynamically adjusting the upper limit of the absolute value of the active power ramp during the frequency regulation response phase of the wind turbine generator set in step S1, the upper limit of the absolute value of the active power ramp during the frequency regulation response phase of the wind turbine generator set is set using fuzzy logic, including the following steps: Step S1-1: Based on the existing wind turbine transmission chain bending fatigue damage measurement technology, the wind turbine transmission chain bending fatigue damage is obtained and normalized; the wind turbine transmission chain bending fatigue life margin, a dynamic parameter denoted as F, is obtained by subtracting the wind turbine transmission chain bending fatigue damage from 1, and is identified, normalized, and fuzzified in real time, and divided into 9 fuzzy sets, including: extremely small VS, medium and small MS, small S, relatively small LS, medium M, relatively large LL, relatively large L, medium and large ML, and extremely large VL; Step S1-2: The frequency regulation demand of the wind turbines during the frequency regulation response phase, which is the absolute value of the active power ramping expected by the power system, is recorded as |V|. This demand is measured using the absolute value of the power system frequency change rate obtained in real time. This demand is measured in real time and normalized and fuzzified to form seven fuzzy sets: minimum VS, medium-small MS, small S, medium M, large L, medium-large ML, and maximum VL. Step S1-3: The upper limit of the absolute value of the active power ramp during the frequency regulation response phase of the wind turbine is recorded as |G|, which is normalized and fuzzified and divided into 8 fuzzy sets, including: minimum VS, medium and small MS, small S, relatively small LS, medium M, large L, medium and large ML, and maximum VL; Step S1-4: Based on the two experiences that the larger the bending fatigue life margin of the wind turbine transmission chain, the larger the upper limit of the absolute value of the wind turbine active power ramp should be set, and the larger the absolute value of the active power ramp of the wind turbine desired by the power system during the frequency modulation response phase, the larger the upper limit of the absolute value of the wind turbine active power ramp should be set, the fuzzy logic of the upper limit of the absolute value of the wind turbine active power ramp is obtained from the dynamic parameter of the bending fatigue life margin of the wind turbine transmission chain and the frequency modulation requirement of the absolute value of the active power ramp of the wind turbine desired by the power system during the frequency modulation response phase is as shown in the following table: 。 3. The variable ramp frequency modulation strategy for wind turbines considering dynamic parameters and frequency modulation requirements according to claim 1 is characterized in that: When solving the optimal active power ramp absolute value of the wind turbine generator set during the frequency regulation recovery phase in step S2, the active power ramp absolute value of the wind turbine generator set during the frequency regulation recovery phase is used as the optimization variable, which is recorded as |K| By establishing the optimization objective and constraint conditions, the optimal active power ramp absolute value of the wind turbine frequency recovery stage is solved, which is recorded as |K| opt , including the following steps: Step S2-1: Considering the power system's frequency regulation requirement that the absolute value of the active power ramp of the wind turbine generator set during the frequency regulation recovery phase be as small as possible, the optimization objective is to minimize the absolute value of the active power ramp of the wind turbine generator set during the frequency regulation recovery phase, as shown in the following formula: （1） Step S2-2: Considering that the wind turbine rotor speed is a dynamic parameter with a safe range, the constraint conditions include the relationship between the absolute value of the active power ramp during the wind turbine frequency modulation recovery phase and the wind turbine rotor speed, a dynamic parameter, and that the wind turbine rotor speed does not exceed its safe range, as shown in the following formula: （2） in, t For time, tr is the start time of the wind turbine frequency regulation recovery phase, td is the end time of the wind turbine frequency regulation recovery phase, is the active power reference of the wind turbine, Active reference for maximum power point tracking of wind turbines, Fixed parameters for maximum power point tracking of wind turbines. is the wind turbine rotor speed, For wind turbines tr The rotor speed at the moment, is the moment of inertia of the wind turbine, is the actual active power of the wind turbine, For wind turbines tr Always be practical, is the power system frequency deviation, is the wind turbine rotor speed change rate, J is the moment of inertia of the wind turbine, Wind energy capture for wind turbines, is the lower limit of the safe range of wind turbine rotor speed, is the upper limit of the safe range of the wind turbine rotor speed; when =0, the wind turbine does not need frequency regulation, so the above formula does not take into account =0; Step S2-3: Based on the optimization objectives and constraints described in steps S2-1 and S2-2, the optimal active power ramp absolute value in the frequency regulation recovery phase of the wind turbine generator is solved.

Images