A wind turbine maximum power tracking method and device

Abstract

The present invention discloses a method and device for tracking the maximum power of a wind turbine. The method obtains the equivalent wind speed of the impeller surface at a set distance in front of the impeller in real time and estimates the time required for the wind speed to reach the impeller surface; within the estimated time range, obtains the wind speed time series from the current moment to the moment when the wind speed reaches the impeller surface according to a set time period; calculates the standard deviation of the wind speed within the estimated time range, and when the wind speed standard deviation is less than a set threshold, turns on the maximum tip speed ratio tracking function, otherwise turns off the function. The present invention uses a laser radar to detect the wind speed changes in a future period in advance. When it is detected that the wind speed changes are relatively stable, the optimal tip speed ratio tracking function is turned on. Through the designed closed-loop control system, the theoretically optimal tip speed ratio is accurately tracked, the maximum wind energy capture of the blades is achieved, and the power generation of the unit is increased.

Description

Technical Field

[0001] The invention relates to a method and a device for tracking the maximum power of a wind generator. Background Art

[0002] Modern large-scale wind turbines are nonlinear systems with high inertia and time lag. Different control strategies are employed in different operating ranges to achieve different control objectives. Generally speaking, within the operating wind speed range, the turbine's operating range is divided into the minimum speed range, the maximum wind energy capture range, the transition range, and the full power range. In the minimum speed and transition ranges, the turbine uses torque control, using the minimum and maximum speeds as reference values, respectively, and ensuring speed stability through PID closed-loop (or PI) control. In the maximum wind energy capture range (which varies with wind speed), the turbine operates in a variable speed state to achieve the optimal tip speed ratio and thus maximize Cp. In the full power range, the turbine generally adopts a constant power strategy, using the variable pitch system to remove excess wind energy and maintain constant output power. When operating in the maximum wind energy capture range, the turbine detects the rotor speed as input, and a control algorithm calculates the generator electromagnetic torque, thereby controlling the rotor speed so that the tip speed ratio tracks the optimal tip speed ratio and maximizes wind energy absorption.

[0003] In the maximum wind energy capture section, there are two methods to calculate the generator electromagnetic torque: one is to calculate the generator electromagnetic torque by simulation by calculating the theoretical optimal gain:

[0004]

[0005] Where: k opt is the optimal gain; R is the impeller radius; λ opt is the optimal tip speed ratio, which is related to the blade model; C pmax is the maximum wind energy utilization coefficient of the blade obtained under the conditions of optimal tip speed ratio and optimal theoretical pitch angle; ω g is the generator speed, ω g =G*ω r , G is the gearbox speed ratio, ω r is the impeller speed. For direct-drive generators, G=1.

[0006] It should be noted that the above-mentioned optimal tip speed ratio and maximum wind energy utilization coefficient were obtained under simulation conditions. Under certain air density conditions (generally standard air density), the optimal gain in actual use is a fixed value (theoretical optimal gain). When the unit operates under conditions with lower air density, the actual optimal gain of the unit will differ significantly from the theoretical optimal gain, leading to deviations in the electromagnetic torque calculation, resulting in a significant difference between the actual tip speed ratio of the unit blades and the theoretical optimal tip speed ratio.

[0007] On the other hand, the air density can be estimated in real time by the ambient temperature T(t) and altitude H during unit operation, and the optimal gain can be estimated in real time according to the above formula:

[0008]

[0009] It can be seen that the optimal gain changes with the ambient temperature (the altitude H is a fixed value). However, in actual operating conditions, the ambient temperature changes slowly, while the wind speed changes rapidly, resulting in a certain difference between the calculated gain and the actual gain, causing the actual optimal tip speed ratio of the unit to be non-optimal. Summary of the Invention

[0010] In order to solve the problem, the present invention provides a method and device for tracking the maximum power of a wind turbine.

[0011] The present invention adopts the following technical solutions to solve the above technical problems:

[0012] A method for tracking maximum power of a wind turbine generator, the method comprising the following steps:

[0013] Step 1: Obtain the equivalent wind speed of the impeller surface at a set distance in front of the impeller in real time, and estimate the time required for the wind speed to reach the impeller surface;

[0014] Step 2: within the time range estimated in step 1, obtain the wind speed time series from the current moment to the moment when the wind speed reaches the impeller surface according to the set time period;

[0015] Step 3: Calculate the wind speed standard deviation within the time range estimated in step 1. When the wind speed standard deviation is less than the set threshold, enable the maximum tip speed ratio tracking function; otherwise, disable the function.

[0016] Furthermore, in step 1, the equivalent wind speed of the impeller surface at a set distance in front of the impeller is obtained in real time by a laser radar installed at the top of the wind turbine nacelle.

[0017] Furthermore, the time required for the wind speed to reach the impeller surface is T0=L / V, where L represents the set distance and V represents the equivalent wind speed of the impeller surface at the set distance in front of the impeller.

[0018] Furthermore, in step 2, the wind speed time series is obtained by using a lidar installed on the top of the cabin.

[0019] Furthermore, in step 3, the maximum tip speed ratio tracking function is enabled and the control strategy is as follows:

[0020] 1) Determine whether the unit is operating in the maximum wind energy capture section;

[0021] 2) Calculate the average wind speed v within the time range estimated in step 1avg , and calculate the impeller set speed;

[0022] 3) The generator speed detected by the generator speed sensor is recorded as the sliding average of the generator speed within the time range estimated in step 1;

[0023] 4) The deviation between the impeller set speed and the detected generator speed is input into the torque controller and converted into a torque given compensation value ΔT e ;

[0024] 5) Calculate the basic given torque that changes with ambient temperature:

[0025] T e =k opt (T(t),H)*ω g 2

[0026] Where, ω g is the detected generator speed; C pmax represents the maximum wind energy utilization coefficient of the blade under the conditions of optimal tip speed ratio and optimal theoretical pitch angle; R is the impeller radius; λ opt is the optimal tip speed ratio; ρ(·) represents the air density, T(t) is the air temperature at the current time t, and H is the altitude;

[0027] 6) The electromagnetic torque applied to the generator side is expressed as:

[0028] T set =T e +ΔT e ;

[0029] 7) To prevent the given torque from jumping significantly, set the torque upper limit T max and the lower limit T min ,

[0030]

[0031] Where T represents the electromagnetic torque given value finally output to the wind turbine.

[0032] Furthermore, in step 1), when the unit is in normal power generation state and there is no power restriction, the average impeller speed w within the set time is calculated. r_avg , the unit is determined to be operating in the maximum wind energy capture section when the following conditions are met:

[0033] δ1*ω min <ω r_avg <δ2*ω max

[0034] Where ωmin Indicates the minimum impeller speed, ω max represents the maximum impeller speed, δ1 and δ2 represent ω min and ω max The coefficient of .

[0035] Furthermore, in step 2), the impeller set speed ω is calculated by the following formula: ref :

[0036]

[0037] Where λ opt is the theoretical optimal gain, obtained through simulation.

[0038] Furthermore, the torque controller in step 4) is a PID controller or a PI controller, and the parameters of the PID controller or the PI controller can be adjusted so that the dynamic response and static response of the unit meet the design requirements. The output of the PID controller or the PI controller is the given torque of the generator. Through torque control, the impeller speed is controlled to achieve the purpose of tracking the optimal tip speed ratio.

[0039] Furthermore, in step 1), the wind speed range of the maximum wind energy capture section is set through simulation. When the average wind speed within the time range estimated in step 1 is within the wind speed range, it is determined that the unit is operating in the maximum wind energy capture section.

[0040] A maximum power tracking device for a wind turbine generator, comprising a laser radar mounted on top of a wind turbine nacelle, a control module, and an optimal tip speed ratio tracking module, wherein the optimal tip speed ratio tracking module comprises a given speed calculation module, a torque controller, a basic given torque calculation module, and a limiter;

[0041] The laser radar obtains the equivalent wind speed of the impeller surface at a set distance in front of the impeller in real time;

[0042] The control module activates the maximum tip speed ratio tracking module according to the above method when the wind speed standard deviation is less than the set threshold, and deactivates the maximum tip speed ratio tracking module when the wind speed standard deviation is greater than or equal to the set threshold;

[0043] The limiter is connected to the wind generator;

[0044] The given speed calculation module calculates the impeller set speed according to the method described in step 2) of claim 5;

[0045] The input of the torque controller is the difference between the impeller set speed and the wind turbine generator speed detected in real time, and the output is the torque given compensation value;

[0046] The basic given torque calculation module calculates the basic given torque that changes with the ambient temperature;

[0047] The input of the limiter is the sum of the torque given compensation value and the basic given torque, and the input is the electromagnetic torque given value of the wind turbine.

[0048] Compared with the existing technology, the present invention adopts the above technical solution and has the following technical effects: the present invention uses laser radar to design a closed-loop control system to improve the tracking accuracy of the unit for the optimal tip speed ratio in the maximum wind energy capture section, improve the wind energy utilization coefficient of the blade, and thus improve the power generation capacity of the unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 This is a schematic diagram of the installation of the laser radar;

[0050] Figure 2 It is a structural diagram of the device of the present invention. DETAILED DESCRIPTION

[0051] The technical solution of the present invention will be further described below in conjunction with the accompanying drawings.

[0052] The control strategy of a wind turbine in the maximum wind energy capture section is generally open-loop control, and the tracking effect of the optimal tip speed ratio is poor. The present invention uses a laser radar to detect the wind speed changes in the future in advance. When the wind speed changes are detected to be relatively stable, the optimal tip speed ratio tracking function is turned on. Through the designed closed-loop control system, accurate tracking of the theoretical optimal tip speed ratio is achieved, achieving maximum wind energy capture of the blades and increasing the power generation of the unit.

[0053] like Figure 1 As shown, the equivalent wind speed V of the impeller surface 1 at a certain distance L in front of the impeller is obtained in real time by the laser radar 2 installed on the top of the nacelle, and the time T0 = L / V required for the wind speed to reach the impeller surface is estimated. Within the time range of T0, according to a certain time period (for example, 1s), the wind speed time series from the current time t to the time T0 is obtained by the laser radar, as shown in the following formula:

[0054] V(t)=[V(t),V(t+1),V(t+2),…,V(t+T0)]

[0055] At the same time, the wind speed standard deviation Vstd within the time period T0 is calculated. When the wind speed standard deviation is less than a certain preset value Vstd0, the maximum tip speed ratio tracking function is turned on, otherwise it is turned off:

[0056] 1) When 0<=Vstd<=Vstd0, the maximum tip speed ratio tracking function is enabled;

[0057] 2) When Vstd>Vstd0, the maximum tip speed ratio tracking function is turned off.

[0058] When the free flow wind speed in front of the impeller is monitored to meet the above condition 1, the above maximum tip speed ratio tracking function is turned on and the following Figure 2 The control strategy shown is performed:

[0059] To determine whether the unit is operating in the maximum wind energy capture section, it is generally determined based on the impeller speed. When the unit is in normal power generation and there is no power restriction, the average impeller speed w within a period of time T is calculated. r_avg , the unit is determined to be operating in the maximum wind energy capture section when the following conditions are met:

[0060] δ1*ω min <ω r_avg <δ2*ω max

[0061] In the above formula, ω min Indicates the minimum impeller speed, ω max Indicates the maximum impeller speed; δ1, δ2 represent ω min and ω max The coefficients range from 1.0≤δ1≤1.1 to 0.85≤δ2≤0.95.

[0062] 2) Calculate the average wind speed v during the above T0 period avg The impeller set speed ω is calculated by the following formula ref :

[0063]

[0064] In the above formula, λ opt is the theoretical optimal gain, obtained through simulation.

[0065] 3) The generator speed ω detected by the generator speed sensor is the sliding average of the generator speed in the T0 period;

[0066] 4) Calculate the impeller speed ω ref The deviation between the actual speed ω and the torque controller is used as the input of the torque controller and converted into the torque compensation value ΔT by the torque controller. e , where the torque controller can be a PID controller or a PI controller;

[0067] 5) Calculate the basic given torque that changes with ambient temperature:

[0068] T e =k opt (T(t),H)*ω g 2 ;

[0069] 6) In this way, the electromagnetic torque applied to the generator side can be expressed as:

[0070] T set =T e +ΔT;

[0071] 7) To prevent the given torque from jumping significantly, a limiter is designed to set the torque upper limit T max and the lower limit T min , and the final electromagnetic torque given value output to the wind turbine is obtained:

[0072]

[0073] 8) In the next T0 period, repeat the above steps 1 to 7.

[0074] Furthermore, based on the use of lidar, the torque controller parameters are redesigned and readjusted according to the model of the whole machine. If the torque controller is a PI controller, the proportional coefficient Kp and the integral coefficient Ki are adjusted. If it is a PID controller, the proportional coefficient Kp, the integral coefficient Ki, and the differential coefficient Kd are adjusted so that the dynamic response and static response of the unit meet the design requirements (meet the phase margin and phase margin indicators). The basic given torque calculation module is removed, and the output torque of the PI or PID controller is the given torque of the generator. Through torque control, the impeller speed is controlled to achieve the purpose of tracking the optimal tip speed ratio.

[0075] Furthermore, the maximum wind energy capture section of the unit operation can be determined by setting a certain range of wind speed sections according to the simulation: V1<V<V2, when the average wind speed v in a certain time period T0 is avg When within the above range, the unit can be considered to be operating in the maximum wind energy capture section.

[0076] It should be pointed out that the description of the above embodiments is only used to help understand the method of this application and its core idea. For ordinary technicians in this technical field, without departing from the principles of this application, several improvements and modifications can be made to this application, and these improvements and modifications are also within the scope of protection of the claims of this application.

Claims

1. A method for tracking maximum power of a wind turbine, characterized in that: The method comprises the following steps: Step 1: Obtain the equivalent wind speed of the impeller surface at a set distance in front of the impeller in real time, and estimate the time required for the wind speed to reach the impeller surface; Step 2: within the time range estimated in step 1, obtain the wind speed time series from the current moment to the moment when the wind speed reaches the impeller surface according to the set time period; Step 3: Calculate the wind speed standard deviation within the time range estimated in Step 1. When the wind speed standard deviation is less than the set threshold, enable the maximum tip speed ratio tracking function; otherwise, disable the function. In step 3, the maximum tip speed ratio tracking function is enabled and the control strategy is as follows: 1) Determine whether the unit is operating in the maximum wind energy capture section; 2) Calculate the average wind speed v within the time range estimated in step 1 avg , and calculate the impeller set speed; 3) The generator speed detected by the generator speed sensor is recorded as the sliding average of the generator speed within the time range estimated in step 1; 4) The deviation between the impeller set speed and the detected generator speed is input into the torque controller and converted into a torque given compensation value ΔT e ; 5) Calculate the basic given torque that changes with ambient temperature: T e =k opt (T(t),H)*ω g 2 Where, ω g is the detected generator speed; c pmax represents the maximum wind energy utilization coefficient of the blade under the conditions of optimal tip speed ratio and optimal theoretical pitch angle; R is the impeller radius; λ opt is the optimal tip speed ratio; ρ(·) represents the air density, T(t) is the air temperature at the current time t, and H is the altitude; 6) The electromagnetic torque applied to the generator side is expressed as: T set =T e +ΔT e ; 7) To prevent the given torque from jumping significantly, set the torque upper limit T max and the lower limit T min , Where T represents the electromagnetic torque given value finally output to the wind turbine.

2. A wind turbine maximum power tracking method according to claim 1, characterized in that: In step 1, the equivalent wind speed of the impeller surface at a set distance in front of the impeller is obtained in real time by a laser radar installed on the top of the wind turbine nacelle.

3. A wind turbine maximum power tracking method according to claim 1, characterized in that: The time required for the wind speed to reach the impeller surface is T0 = L / V, where L represents the set distance and V represents the equivalent wind speed of the impeller surface at the set distance in front of the impeller.

4. A wind turbine maximum power tracking method according to claim 1, characterized in that: In step 2, the wind speed time series is obtained by installing a lidar on the top of the cabin.

5. The method for tracking the maximum power output of a wind turbine according to claim 1, wherein: In step 1), when the unit is in normal power generation state and there is no power restriction, calculate the average impeller speed w within the set time r_avg , the unit is determined to be operating in the maximum wind energy capture section when the following conditions are met: d1*h min <oh r_avg <δ2*ω max Where ω min Indicates the minimum impeller speed, ω max represents the maximum impeller speed, δ1 and δ2 represent ω min and ω max The coefficient of .

6. A wind turbine maximum power tracking method according to claim 5, characterized in that: In step 2), the impeller set speed ω is calculated by the following formula: ref : Where λ opt is the theoretical optimal gain, obtained through simulation.

7. A wind turbine maximum power tracking method according to claim 1, characterized in that: The torque controller in step 4) is a PID controller or a PI controller. The parameters of the PID controller or the PI controller can also be adjusted so that the dynamic response and static response of the unit meet the design requirements. The output of the PID controller or the PI controller is the given torque of the generator. Through torque control, the impeller speed is controlled to achieve the purpose of tracking the optimal tip speed ratio.

8. A wind turbine maximum power tracking method according to claim 1, characterized in that: In step 1), the wind speed range of the maximum wind energy capture section is set through simulation. When the average wind speed within the time range estimated in step 1 is within the wind speed range, it is determined that the unit is operating in the maximum wind energy capture section.

9. A maximum power tracking device for a wind turbine, characterized in that: The device includes a laser radar installed on the top of the wind turbine nacelle, a control module and an optimal tip speed ratio tracking module. The optimal tip speed ratio tracking module includes a given speed calculation module, a torque controller, a basic given torque calculation module and a limiter. The laser radar obtains the equivalent wind speed of the impeller surface at a set distance in front of the impeller in real time; The control module activates the maximum tip speed ratio tracking module according to the method described in steps 1 to 3 of claim 1 when the wind speed standard deviation is less than a set threshold, and deactivates the maximum tip speed ratio tracking module when the wind speed standard deviation is greater than or equal to the set threshold; The limiter is connected to the wind generator; The given speed calculation module calculates the impeller set speed according to the method described in step 2) of claim 1; The input of the torque controller is the difference between the impeller set speed and the wind turbine generator speed detected in real time, and the output is the torque given compensation value; The basic given torque calculation module calculates the basic given torque that changes with the ambient temperature; The input of the limiter is the sum of the torque given compensation value and the basic given torque, and the input is the electromagnetic torque given value of the wind turbine.

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