阅读说明：本技术 一种风电机组变桨稳转速控制系统及控制方法 (Variable-pitch stable-rotating-speed control system and control method for wind turbine generator ) 是由 徐枪声 和海涛 郭霖涛 张喜东 张文彬 于 2021-09-16 设计创作，主要内容包括：本发明公开了一种风电机组变桨稳转速控制系统及控制方法,其中系统包括：编码器模块获取发电机转速信号并发送至卡尔曼滤波器；卡尔曼滤波器还接收发电机电磁转矩值和风力矩估计值,并进行滤波处理,并将其滤波结果发送至非线性微分跟踪器；非线性微分跟踪器对其进行再次滤波计算后,得到转速信号反馈值并发送至比较器；比较器将其与转速预设值进行比较,得到转速误差值并将其发送至PID控制器；PID控制器接收转速微分信号,并依据转速信号误差值得到风轮的变桨控制指令,并将其发送至风电机组的变桨控制系统。通过结合PI控制算法,组成了完整的PID算法,提高控了制系统稳定裕度,当风电场风速大幅波动时,转速更稳定,电能输出更平稳。(The invention discloses a variable-pitch stable-rotating-speed control system and a control method for a wind turbine generator, wherein the system comprises: the method comprises the following steps that an encoder module acquires a rotating speed signal of a generator and sends the rotating speed signal to a Kalman filter; the Kalman filter also receives an electromagnetic torque value and an air torque estimated value of the generator, carries out filtering processing and sends a filtering result to the nonlinear differential tracker; after the nonlinear differential tracker carries out filtering calculation again on the signal, a rotating speed signal feedback value is obtained and sent to the comparator; the comparator compares the rotation speed error value with a rotation speed preset value to obtain a rotation speed error value and sends the rotation speed error value to the PID controller; and the PID controller receives the rotating speed differential signal, obtains a variable pitch control instruction of the wind wheel according to the rotating speed signal error value, and sends the variable pitch control instruction to a variable pitch control system of the wind turbine generator. By combining with a PI control algorithm, a complete PID algorithm is formed, the stability margin of a control system is improved, and when the wind speed of a wind power plant fluctuates greatly, the rotating speed is more stable and the electric energy output is more stable.)

1. The utility model provides a steady rotational speed control system of wind turbine generator system becomes oar which characterized in that includes: the system comprises an encoder module, a Kalman filter, a nonlinear differential tracker, a comparator, a PID controller and a wind moment estimation module;

the encoder module acquires a rotating speed signal of the generator and sends the rotating speed signal to the Kalman filter;

the Kalman filter also receives a generator electromagnetic torque feedback value and a wind torque estimation value of the wind torque estimation module, carries out filtering processing and sends the filtered rotating speed signal to the nonlinear differential tracker;

the nonlinear differential tracker performs filtering processing on the filtered rotating speed signal again to obtain a rotating speed signal feedback value and sends the rotating speed signal feedback value to the comparator;

the comparator compares the rotating speed signal feedback value with a rotating speed preset value to obtain a rotating speed error value and sends the rotating speed error value to the PID controller;

the PID controller receives the rotating speed differential signal sent by the nonlinear differential tracker, obtains a variable pitch control instruction of the wind wheel according to the rotating speed error value, and sends the variable pitch control instruction to a variable pitch control system of the wind turbine generator;

and the wind moment estimation module calculates the wind moment estimation value according to the variable pitch control instruction, the pitch angle feedback value and the wind moment detection value of the wind wheel.

2. The wind turbine generator pitch-controlled speed stabilizing control system according to claim 1,

the calculation formula of the wind moment estimated value is as follows:

T_w＝kθ+b；

and the theta is a pitch angle, the k is a first parameter of the weighted least square method in-line identification, and the b is a second parameter of the weighted least square method in-line identification.

3. The wind turbine generator pitch-controlled stable rotation speed control system according to claim 2,

the calculation formula of the weighted least square method online identification first parameter k and the weighted least square method online identification second parameter b is as follows:

Y＝[T_w(n),T_w(n-1),…T_w(n-m)]^T；

wherein, T_wAnd (n) is a detected value of the wind torque in the nth sampling period, theta (n) is a feedback value of the pitch angle in the nth sampling period of the rotating speed, and m can be an integer of 2-6.

4. The wind turbine generator pitch-controlled speed stabilizing control system according to claim 1,

the Kalman filteringFirstly, calculating prior estimation of state x in the current sampling period according to the driving moment estimation value in the last sampling periodThe variance calculation method of the error comprises the following steps:then calculating the output of the filter according to the measured value z of the rotating speed of the generator

The Kalman filter outputThe variance of the error is:

5. the wind turbine generator pitch-controlled speed stabilizing control system according to claim 1,

the function of the nonlinear differential tracker is:

wherein h is the sampling period of the rotating speed v (t) of the generator, x₁(k) For the filtered rotational speed value, x, of the non-linear differential tracker₂(k) Calculating a differential value of the rotational speed for the non-linear differential tracker.

6. The wind turbine generator pitch-controlled speed stabilizing control system according to claim 1,

the output function of the PID controller is:

wherein e (k) ═ v_s-x₁(k) I.e. error value of rotation speed, v_sIs a reference value of the rotational speed of the generator, P_PIs the proportional coefficient, P, of the PID controller_IIs the integral coefficient, P, of the PID controller_DIs the differential coefficient, x, of the PID controller₁(k) Is a feedback signal of the rotational speed of the generator, x₂(k) Is an approximation of the true speed differential signal.

7. A control method of a variable-pitch stable-rotating-speed control system of a wind turbine generator is characterized by being used for controlling the variable-pitch stable-rotating-speed control system of the wind turbine generator as set forth in any one of claims 1-6, and comprising the following steps:

acquiring a rotating speed signal of the generator through an encoder module and sending the rotating speed signal to a Kalman filter;

receiving the electromagnetic torque value and the wind moment estimated value of the generator based on the Kalman filter, filtering the electromagnetic torque value and the wind moment estimated value, and sending the filtered wind moment estimated value to a nonlinear differential tracker;

filtering and calculating the rotation speed signal again based on the nonlinear differential tracker to obtain a rotation speed signal feedback value, and sending the rotation speed signal feedback value to a comparator;

comparing the rotation speed error value with a preset rotation speed value through the comparator to obtain a rotation speed error value, and sending the rotation speed error value to the PID controller;

and receiving a rotating speed differential signal based on the PID controller, obtaining a variable pitch control instruction of the wind wheel according to the rotating speed signal error value, and sending the variable pitch control instruction to a variable pitch control system of the wind turbine generator.

Technical Field

The invention relates to the technical field of wind power control, in particular to a variable-pitch stable-rotating-speed control system and a control method for a wind turbine generator.

Background

Through the rapid development of recent decades, the wind power generation technology is basically mature, but is not perfect enough, and the system stability is yet to be optimized under the working condition of strong wind. Under the working condition of strong wind, the wind speed change amplitude is large, and the rotating speed and the power of the generator are easy to fluctuate, so that the quality of electric energy is reduced or the generator is in overspeed failure. With the development of the wind power market, the competition of the wind power technology is intensified day by day. The urgent need of wind power technology is to improve the stability and reduce the failure rate of wind power generators.

As shown in fig. 1, in the conventional variable pitch and constant speed control system, an encoder acquires a rotating speed signal of a generator, the rotating speed signal is filtered by a linear filter and then is used as a feedback signal of a controller to be compared with a rotating speed set value, a variable pitch instruction is obtained after PID calculation, and the variable pitch system adjusts a pitch angle under the action of the variable pitch instruction, so that the driving torque of the generator, namely the rotating torque from a wind wheel, is changed. The filter in fig. 1 generally adopts a linear first order or linear second order filter, and such a filter may cause phase lag and reduce the stability of the control system. Although the PID control algorithm can compensate the phase lag of the filter, the controller adopts the PI algorithm because the filtered speed signal still has noise interference, and in order to avoid the adverse effect of the noise signal on the control system, the PI algorithm can cause the phase of the control system to lag further, so the stability margin of the control system is low.

The method is characterized in that strong interference exists in the rotating speed measurement of the wind driven generator, decoding errors can occur in the decoding process of an encoder, harmonic interference and electromagnetic radiation generated by power electronic equipment can cause rotating speed measurement noise, the differential calculation of the rotating speed of the generator is sensitive to the measurement noise, and for this reason, the wind driven generator adopts a PI control algorithm. When the fluctuation peak value of the rotating speed exceeds the upper limit of the rotating speed, an overspeed fault is triggered to cause a shutdown phenomenon, and the generating capacity is further influenced.

Disclosure of Invention

The invention aims to provide a variable-pitch stable-rotating-speed control system and a control method for a wind turbine generator.

In order to solve the above technical problem, a first aspect of an embodiment of the present invention provides a variable-pitch and stable-rotation-speed control system for a wind turbine, including: the system comprises an encoder module, a Kalman filter, a nonlinear differential tracker, a comparator, a PID controller and a wind moment estimation module;

the encoder module acquires a rotating speed signal of the generator and sends the rotating speed signal to the Kalman filter;

the Kalman filter also receives the electromagnetic torque of the generator and the wind torque estimation value of the wind torque estimation module, carries out filtering processing on the rotating speed signal and sends the rotating speed signal after filtering to the nonlinear differential tracker;

the nonlinear differential tracker performs filtering processing on the filtered rotating speed signal again to obtain a rotating speed signal feedback value and sends the rotating speed signal feedback value to the comparator;

the comparator compares the rotating speed signal feedback value with a rotating speed preset value to obtain a rotating speed error value and sends the rotating speed error value to the PID controller;

the PID controller receives the rotating speed differential signal sent by the nonlinear differential tracker, obtains a variable pitch control instruction of the wind wheel according to the rotating speed error value, and sends the variable pitch control instruction to a variable pitch control system of the wind turbine generator;

and the wind moment estimation module calculates the wind moment estimation value according to the variable pitch control instruction, the pitch angle feedback value and the wind moment detection value of the wind wheel.

Further, the calculation formula of the wind moment estimation value is as follows:

T_w＝kθ+b；

and the theta is a pitch angle, the k is a first parameter of the weighted least square method in-line identification, and the b is a second parameter of the weighted least square method in-line identification.

Further, the calculation formula of the weighted least square method online identification first parameter k and the weighted least square method online identification second parameter b is as follows:

Y＝[T_w(n),T_w(n-1),…T_w(n-m)]^T；

wherein, T_wAnd (n) is a detected value of the wind torque in the nth sampling period, theta (n) is a feedback value of the pitch angle in the nth sampling period of the rotating speed, and m can be an integer between 2 and 6.

Further, the kalman filter calculates a priori estimated value of state x in the current sampling period according to the driving moment estimated value in the last sampling period The variance calculation method of the error comprises the following steps:where P, Q are the excitation noise variance and the measurement noise variance,the variance of the error isThen calculating the output of the filter according to the input value z of the rotating speed of the generator

The Kalman filter outputThe variance of the error is:

further, the function of the nonlinear differential tracker is:

wherein h is the sampling period of the rotating speed of the generator, x₁(k) For the filtered rotational speed value, x, of the non-linear differential tracker₂(k) Calculating a differential value of the obtained rotation speed for the non-linear differential tracker.

Further, the output function of the PID controller is:

wherein e (k) ═ v_s-x₁(k)，v_sIs a reference value of the rotational speed of the generator, P_PIs the proportional coefficient, P, of the PID controller_IIs the integral coefficient, P, of the PID controller_DIs the differential coefficient, x, of the PID controller₁(k) Is a feedback signal of the rotational speed of the generator, x₂(k) Is an approximation of the true speed differential signal.

Correspondingly, a second aspect of the embodiment of the present invention provides a control method for a variable-pitch stable-rotation-speed control system of a wind turbine generator, including the following steps:

acquiring a rotating speed signal of the generator through an encoder module and sending the rotating speed signal to a Kalman filter;

receiving the electromagnetic torque value and the wind moment estimated value of the generator based on the Kalman filter, filtering the electromagnetic torque value and the wind moment estimated value, and sending the filtered wind moment estimated value to a nonlinear differential tracker;

filtering and calculating the rotation speed signal again based on the nonlinear differential tracker to obtain a rotation speed signal feedback value, and sending the rotation speed signal feedback value to a comparator;

comparing the rotation speed error value with a preset rotation speed value through the comparator to obtain a rotation speed error value, and sending the rotation speed error value to the PID controller;

and receiving a rotating speed differential signal based on the PID controller, obtaining a variable pitch control instruction of the wind wheel according to the rotating speed signal error value, and sending the variable pitch control instruction to a variable pitch control system of the wind turbine generator.

The technical scheme of the embodiment of the invention has the following beneficial technical effects:

by combining with a PI control algorithm, a complete PID algorithm is formed, so that the stability margin of a control system of the wind driven generator is increased, when the wind speed of a wind power plant fluctuates greatly, the rotating speed of the wind driven generator is more stable, the electric energy output of the wind driven generator is more stable, the occurrence frequency of overspeed faults can be reduced, and the normal operation time and the annual generating capacity are increased.

Drawings

FIG. 1 is a schematic diagram of a variable-pitch stable-rotating-speed control system of a wind turbine generator in the prior art;

fig. 2 is a schematic diagram of a variable-pitch stable-rotation-speed control system of a wind turbine generator according to an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings in conjunction with the following detailed description. It should be understood that the description is intended to be exemplary only, and is not intended to limit the scope of the present invention. Moreover, in the following description, descriptions of well-known structures and techniques are omitted so as to not unnecessarily obscure the concepts of the present invention.

Referring to fig. 2, a first aspect of an embodiment of the present invention provides a variable-pitch and stable-rotation-speed control system for a wind turbine, including: the system comprises an encoder module, a Kalman filter, a nonlinear differential tracker, a comparator, a PID controller and a wind moment estimation module. The method comprises the following steps that an encoder module acquires a rotating speed signal of a generator and sends the rotating speed signal to a Kalman filter; the Kalman filter also receives a generator electromagnetic torque value and a wind torque estimation value of a wind torque estimation module, carries out filtering processing and sends a rotating speed signal after filtering to the nonlinear differential tracker; the nonlinear differential tracker performs filtering processing on the filtered rotating speed signal again to obtain a rotating speed signal feedback value and sends the rotating speed signal feedback value to the comparator; the comparator compares the rotating speed signal feedback value with a rotating speed preset value to obtain a rotating speed error value and sends the rotating speed error value to the PID controller; the PID controller receives the rotating speed differential signal sent by the nonlinear differential tracker, obtains a variable pitch control instruction of the wind wheel according to the rotating speed error value, and sends the variable pitch control instruction to a variable pitch control system of the wind turbine; and the wind moment estimation module calculates a wind moment estimation value according to the variable pitch control instruction, the pitch angle sampling value and the wind moment detection value of the wind wheel.

The wind turbine generator pitch-variable stable rotating speed control system adopts the Kalman filter to replace a common linear filter, except for the rotating speed signal output by the encoder, the wind torque estimation value and the electromagnetic torque of the generator are used as the input of the Kalman filter, the rotating speed signal output by the Kalman filter is output to the nonlinear differential tracker, and the nonlinear differential tracker further filters the rotating speed signal, extracts the rotating speed differential signal and then sends the rotating speed differential signal to the PID controller to execute complete PID control operation.

Specifically, the wind moment in the invention refers to the rotation moment of wind on a wind wheel, the sampling period of a control system of the wind driven generator can reach 0.01 second, and the wind speed and the rotating speed of the generator in two adjacent sampling periods are approximately equal. On the premise that the wind speed and the rotating speed of the generator are unchanged in two adjacent periods, a linear function relation between the wind moment and the pitch angle theta can be obtained. The calculation formula of the wind moment estimated value is as follows:

T_w＝kθ+b；

and the step b is a second parameter of the weighted least square method online identification.

And identifying the first parameter k and the second parameter b on line by a weighted least square method, and predicting the wind moment Tw according to the pitch angle instruction. The wind wheel rotation speed acceleration a and the wind wheel rotation speed omega can be measured according to the wind wheel rotation speed sensor, the electromagnetic torque of the generator is equivalent to the wind wheel side to obtain the wind wheel resistance torque Te, and the wind moment measurement value T is obtained by setting zeta as the wind wheel rotational inertia_w＝T_e+ζa+μ_rOmega. Parameter mu_rThe moment loss coefficient corresponding to the rotation of the wind wheel.

Further, the calculation formula of the weighted least square method online identification first parameter k and the weighted least square method online identification second parameter b is as follows:

Y＝[T_w(n),T_w(n-1),…T_w(n-m)]^T； (2)

wherein, T_wAnd (n) is a detected value of the wind torque in the nth rotating speed sampling period, theta (n) is a feedback value of the pitch angle in the nth rotating speed sampling period, and m can be an integer of 2-6.

And in each sampling period, identifying a first parameter k and a second parameter b by using a weighted least square method according to the measured value of the wind moment, and then estimating the wind moment Tw of the wind wheel according to the pitch angle instruction.

Specifically, the generator drive torque u is T_wh-(T_e+μω),T_whIs equivalent to the wind moment on the generator side, mu is the friction loss corresponding to the generator speed, omega is the generator speed, and the reduction ratio of the gear box is K

Furthermore, the general filtering algorithm can cause signal phase lag, so that the stability of the control system is reduced, and the phase lag of the Kalman filter is small, thereby being beneficial to the stability of the control system. The application method of the Kalman filter in the variable-pitch and constant-speed control system is as follows:

the generator state equation is as follows:

where x (k) is the rotational speed of the generator for the k-th sampling period, and ζ is the sum of the rotational inertia of the rotor of the generator and the high-speed shaft of the gearbox. If μ is a friction loss coefficient corresponding to the generator rotation speed, T is a sampling period, and u is the generator driving torque, u is T_wh-(T_e+ μ x); i.e. the drive torque of the generator is the equivalent of the wind torque of the rotor to the drive torque T on the generator shaft_whAnd the difference value of the resistance torque of the generator, namely the sum of the electromagnetic torque and the friction torque, wherein w is excitation noise, the excitation noise comes from the estimation error of the driving torque of the generator, and the variance of the excitation noise w is Q according to the online statistical result.

The observation equation is:

z(k)＝x(k)+v(k) (6)

wherein z (k) is a sampling value of the rotating speed of the generator in the kth sampling period, namely the rotating speed corresponding to the output signal of the encoder, v is observation noise, and the observation noise variance R is obtained according to field test. And filtering the generator rotating speed signal according to the state equation (3) and the observation equation (4) in combination with a Kalman filtering formula. The method comprises the following specific steps:

initialization: p is 0, x is z (0)

Firstly, neglecting excitation noise, and calculating the prior estimation value of the state x of the period by using a state equation (3) according to the driving moment estimation value u of the previous periodThis estimate will have errors, letThe variance of the error is The variance of the error is calculated as follows:

the second step calculates the filter output based on the filter velocity input z and the first state estimate x

Updating filter outputVariance of error

And the first step and the second step are carried out once every sampling period, so that the filtered value of the rotating speed of the generator can be obtained.

Noise interference in the generator rotating speed signal is weakened after the generator rotating speed signal is filtered by the Kalman filter.

Specifically, after being filtered by a Kalman filter, the generator rotating speed signal can be directly extracted by a differential tracker. The calculation process of the nonlinear differential tracker is as follows

Where h is the period of rotation of the generator, h₀The value of 1.5, the value of r is 2, v (t) is a rotating speed signal input by the nonlinear tracker, x₁,x₂The rotation speed value filtered by the nonlinear differential tracker and the differential value of the rotation speed are not distinguished. The variable fh in the formula is calculated as follows:

fsg(x,d)＝[sign(x+d)-sign(x-d)]/2

d＝rh₀ ²

a₀＝h₀x₂

y＝x₁+a₀

a₂＝a₀+sign(y)(a₁-d)/2

a＝(a₀+y)fsg(y,d)+a₂[1-fsg(y,d)]

where sign () is a sign function i.e

The rotating speed signal of the generator is processed by a nonlinear differential tracker to obtain a rotating speed filtering value x₁Noise interference in the generator speed signal is further weakened, and an approximate value x of the real speed signal differential is obtained₂。

Specifically, the output function of the PID controller is:

wherein e (k) ═ v_s-x₁(k) I.e. the output value of the comparator, v_sIs a reference value of the rotational speed of the generator, P_PIs proportional coefficient of PID controller, P_IIs the integral coefficient, P, of a PID controller_DIs a PID controller differential coefficient, x₁(k) As a feedback signal of the rotational speed of the generator, x₂(k) Is an approximation of the true differential rotational speed signal.

The above formula is a complete PID control algorithm, and the controller can show a lead or lag property by adjusting PID parameters, so that conditions are provided for improving the stability margin of the variable pitch speed stabilizing control system.

Because the differential extraction process of the current wind driven generator control strategy is too sensitive to noise interference in the rotating speed signal of the wind driven generator, the current variable-pitch speed-stabilizing controller abandons differential operation and only adopts a PI part of a PID controller algorithm, thereby leading to smaller stability margin of a control system. The invention uses Kalman filtering algorithm to reduce noise interference in the generator rotating speed signal, then uses the nonlinear differential tracker to further reduce the noise interference, extracts a differential value close to a real signal from the noise interference, and uses the differential signal extracted by the nonlinear differential tracker and the rotating speed filtering signal to form a complete PID controller, thereby providing conditions for improving the stability margin of the variable-pitch speed-stabilizing control system.

Correspondingly, a second aspect of the embodiment of the present invention provides a method for controlling a variable-pitch stable rotating speed of a wind turbine generator, including the following steps:

acquiring a rotating speed signal of the generator through an encoder module and sending the rotating speed signal to a Kalman filter;

receiving the electromagnetic torque value and the wind moment estimated value of the generator based on the Kalman filter, filtering the electromagnetic torque value and the wind moment estimated value, and sending the filtered wind moment estimated value to a nonlinear differential tracker;

filtering and calculating the rotation speed signal again based on the nonlinear differential tracker to obtain a rotation speed signal feedback value, and sending the rotation speed signal feedback value to a comparator;

comparing the rotation speed error value with a preset rotation speed value through the comparator to obtain a rotation speed error value, and sending the rotation speed error value to the PID controller;

and receiving a rotating speed differential signal based on the PID controller, obtaining a variable pitch control instruction of the wind wheel according to the rotating speed signal error value, and sending the variable pitch control instruction to a variable pitch control system of the wind turbine generator.

The embodiment of the invention aims to protect a variable-pitch stable-rotating-speed control system and a control method of a wind turbine generator, and the control method comprises the following steps: the system comprises an encoder module, a Kalman filter, a nonlinear differential tracker, a comparator, a PID controller and a wind moment estimation module; the method comprises the following steps that an encoder module acquires a rotating speed signal of a generator and sends the rotating speed signal to a Kalman filter; the Kalman filter also receives a generator electromagnetic torque value and a wind torque estimation value of a wind torque estimation module, carries out filtering processing and sends a rotating speed signal after filtering to the nonlinear differential tracker; the nonlinear differential tracker carries out secondary filtering on the filtered rotating speed signal to obtain a rotating speed signal feedback value and sends the rotating speed signal feedback value to the comparator; the comparator compares the rotating speed signal feedback value with a rotating speed preset value to obtain a rotating speed error value and sends the rotating speed error value to the PID controller; the PID controller receives the rotating speed differential signal sent by the nonlinear differential tracker, obtains a variable pitch control instruction of the wind wheel according to the rotating speed error value, and sends the variable pitch control instruction to a variable pitch control system of the wind turbine; the wind moment estimation module calculates a wind moment estimation value according to the variable pitch control instruction, the pitch angle feedback value and the wind moment detection value of the wind wheel. The technical scheme has the following effects:

by combining with a PI control algorithm, a complete PID algorithm is formed, so that the stability margin of a control system of the wind driven generator is increased, when the wind speed of a wind power plant fluctuates greatly, the rotating speed of the wind driven generator is more stable, the electric energy output of the wind driven generator is more stable, the occurrence frequency of overspeed faults can be reduced, and the normal operation time and the annual generating capacity are increased.

It is to be understood that the above-described embodiments of the present invention are merely illustrative of or explaining the principles of the invention and are not to be construed as limiting the invention. Therefore, any modification, equivalent replacement, improvement and the like made without departing from the spirit and scope of the present invention should be included in the protection scope of the present invention. Further, it is intended that the appended claims cover all such variations and modifications as fall within the scope and boundaries of the appended claims or the equivalents of such scope and boundaries.