阅读说明：本技术 基于电力系统频率二阶微分的双馈风机惯性控制方法 (Double-fed fan inertia control method based on second-order frequency differential of power system ) 是由 赵熙临 林震宇 马艺菡 曹娅 吴恒 于 2019-08-29 设计创作，主要内容包括：本发明公开一种基于电力系统频率二阶微分的双馈风机惯性控制方法。该方法包括：对电力系统频率的偏差求二阶导数得出其变化的加速度；计算风机输出的有功功率与电力系统频率的二阶导数之间的函数关系；计算考虑Δf的二阶导数的双馈风机虚拟惯性因子；双馈风机含有Δf二阶导数的惯性控制回路的构建。该控制方法具有更快速的双馈风机动能提取特性,可以更好的用于双馈风机的有功平滑输出技术。相比于传统基于频率一阶导数的惯性控制方法,可以更大程度上利用的风机转子所储存的旋转动能以补偿电力系统有功的缺失,减小电力系统频率的波动。(The invention discloses a double-fed fan inertia control method based on second-order frequency differential of a power system. The method comprises the following steps: solving a second derivative of the deviation of the frequency of the power system to obtain the changing acceleration of the power system; calculating a functional relation between active power output by the fan and a second derivative of the frequency of the power system; calculating a virtual inertia factor of the doubly-fed fan considering the second derivative of the delta f; the doubly-fed wind turbine generator comprises an inertia control loop of a second derivative of delta f. The control method has the characteristic of faster extraction of the kinetic energy of the double-fed fan, and can be better used for the active smooth output technology of the double-fed fan. Compared with the traditional inertia control method based on the first-order frequency derivative, the method can utilize the rotational kinetic energy stored by the fan rotor to a greater extent to compensate the loss of the power system, and reduce the fluctuation of the frequency of the power system.)

1. The doubly-fed wind turbine inertia control method based on the second order differential of the frequency of the electric power system is characterized by comprising the following steps:

step 1: sampling the frequency of a power system, and simultaneously sampling the rotating speed of the wind driven generator;

step 2: taking the real-time frequency of the power system as a feedback signal, and solving a second derivative of the frequency of the power system;

and step 3: calculating a functional relation between a second derivative of the frequency of the electric power system and the active output variable quantity of the double-fed fan;

and 4, step 4: calculating a virtual inertia factor of the doubly-fed fan considering the second derivative of the frequency according to the functional relation in the step 3;

and 5: and (4) constructing an inertia control loop of the fan according to the functional relation in the step (3) and the virtual inertia factor in the step (4).

2. The doubly-fed wind turbine inertia control method based on the second order differential of the power system frequency according to claim 1, wherein the method for calculating the second order derivative of the power system frequency in the step 2 is as follows:

setting a sampling period as T, and sampling values of three adjacent sampling periods as f_(n-1)T、f_nTAnd f_(n+1)TAnd n represents the nth sampling period, the second derivative of the power system frequency can be represented as:

wherein the content of the first and second substances,

3. the doubly-fed wind turbine inertia control method based on the second order differential of the power system frequency according to claim 2, wherein the functional relationship between the second order derivative of the power system frequency and the active output variation of the doubly-fed wind turbine in the step 3 can be expressed as:

wherein, δ P_WTIs the variation of active output of the doubly-fed fan, H_eqIs the equivalent inertia time constant of the fan, K_virIs a virtual inertia coefficient, omega, of the fan_r0Is the same as the current fanStep speed, omega_sThe rotational speed is synchronized for the power system.

4. The doubly-fed wind turbine inertia control method based on the second order frequency differential of the power system as claimed in claim 3, wherein the virtual inertia factor δ f of the doubly-fed wind turbine considering the second order frequency derivative in the step 4 is_koptCan be expressed as:

wherein, K_optFor optimum working coefficient, omega, of the fan_gIs the generator speed.

5. The doubly-fed wind turbine inertia control method based on the second order differential of the power system frequency as claimed in claim 4, wherein the inertia control loop of the wind turbine in the step 5 is: the input signal is a frequency signal f of the power system_sRespectively obtaining the first derivative f thereof through two differential links_s' and second derivative f_s"; wind driven generator rotation speed omega through sampling module_gSampling to output omega_r0(ii) a Connecting the output ends of the two differential links and the output end of the sampler with the calculating module of the formula (2) to calculate the delta P through the formula (2)_WT(ii) a Connecting the output end of the formula (2) with the input end of the calculation module of the formula (3), and calculating delta f through the formula (3)_kopt。

6. The doubly-fed wind turbine inertia control method based on the second order differential of the power system frequency as claimed in claim 5, wherein δ f is_koptIs the adjusting factor of the active output of the wind driven generator, and passes through delta f under the condition that the wind speed is not changed_koptAnd adjusting the active output of the wind driven generator, and further changing the rotating speed of a rotor in the wind driven generator, so that the rotational kinetic energy stored by the wind driven generator is extracted.

Technical Field

The invention relates to double-fed wind driven generator control, fan inertia control, fan smooth output technology and wind driven generator frequency modulation technology, in particular to a method for controlling the active output of a wind driven generator through second-order differentiation of the frequency of a power system.

Background

The inertia control technology of wind power generators is mainly used for adjusting the active power output of a fan by extracting the rotational kinetic energy stored in a generator rotor. When the frequency of the power system fluctuates, the inertia controller of the fan responds to the fluctuation and adjusts the machine side converter of the wind driven generator, so that the kinetic energy of the fan is extracted, and the drop of the power grid frequency is supported.

The traditional inertia control modes comprise droop inertia control, virtual inertia control and suboptimal power working curve control. The control modes are all applied in industry and achieve better control effect. However, the inertia response of the fan needs to be realized by adjusting the rotating speed of the rotor, so that the fan has large hysteresis and cannot respond to the change speed of the frequency of the power system well. Therefore, the control technology for rapidly extracting the kinetic energy of the fan becomes an important research field of various colleges and universities and scientific research institutions.

Disclosure of Invention

In order to solve the problems existing in the background technology, the invention aims to provide a control method for controlling the inertia of a fan by calculating the second derivative of the frequency of a power system.

In order to achieve the purpose, the invention adopts the technical scheme that: the doubly-fed wind turbine inertia control method based on the second order differential of the frequency of the electric power system is characterized by comprising the following steps:

step 1: sampling the frequency of a power system, and simultaneously sampling the rotating speed of the wind driven generator;

step 2: taking the real-time frequency of the power system as a feedback signal, and solving a second derivative of the frequency of the power system;

and step 3: calculating a functional relation between a second derivative of the frequency of the electric power system and the active output variable quantity of the double-fed fan;

and 4, step 4: calculating a virtual inertia factor of the doubly-fed fan considering the second derivative of the frequency according to the functional relation in the step 3;

and 5: and (4) constructing an inertia control loop of the fan according to the functional relation in the step (3) and the virtual inertia factor in the step (4).

Further, the method for calculating the second derivative of the power system frequency in step 2 comprises:

setting a sampling period as T, and sampling values of three adjacent sampling periods as f_(n-1)T、f_nTAnd f_(n+1)TAnd n represents the nth sampling period, the second derivative of the power system frequency can be represented as:

wherein the content of the first and second substances,

further, in step 3, the functional relationship between the second derivative of the power system frequency and the active output variation of the doubly-fed wind turbine can be represented as:

wherein, δ P_WTIs the variation of active output of the doubly-fed fan, H_eqIs the equivalent inertia time constant of the fan, K_virIs a virtual inertia coefficient, omega, of the fan_r0For the current synchronous speed, omega, of the fan_sThe rotational speed is synchronized for the power system.

Further, in step 4, the virtual inertia factor δ f of the doubly-fed wind turbine with the frequency second derivative taken into account_koptCan be expressed as:

wherein, K_optFor optimum working coefficient, omega, of the fan_gIs the generator speed.

Further, inertia of the fan in step 5The control loop is as follows: the input signal is a frequency signal f of the power system_sRespectively obtaining the first derivative f thereof through two differential links_s' and second derivative f_s"; wind driven generator rotation speed omega through sampling module_gSampling to output omega_r0(ii) a Connecting the output ends of the two differential links and the output end of the sampler with the calculating module of the formula (2) to calculate the delta P through the formula (2)_WT(ii) a Connecting the output end of the formula (2) with the input end of the calculation module of the formula (3), and calculating delta f through the formula (3)_kopt。

Further, δ f_koptIs the adjusting factor of the active output of the wind driven generator, and passes through delta f under the condition that the wind speed is not changed_koptAnd adjusting the active output of the wind driven generator, and further changing the rotating speed of a rotor in the wind driven generator, so that the rotational kinetic energy stored by the wind driven generator is extracted.

Compared with the prior art, the invention has the beneficial effects that: compared with the traditional first derivative method, the method for introducing the second derivative of the frequency of the power system obtains more frequency change information; compared with the traditional inertia control method based on the first derivative of the frequency, the inertia control method based on the frequency information can utilize the rotational kinetic energy stored by the wind turbine rotor to a greater extent to compensate the loss of the power system and reduce the fluctuation of the frequency of the power system.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.

FIG. 1; and a fan inertia control block diagram considering second-order differential.

FIG. 2; and controlling the operation of the fan.

FIG. 3; frequency ripple diagram of power system.

FIG. 4; the active power output diagram of the fan.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The invention aims to provide a fan inertia control method based on the second derivative of the frequency of a power system, which has the characteristic of rapidly extracting the kinetic energy of a fan. The method comprises the following steps: sampling the frequency of the power system by using a sampler, and storing sampling values at three continuous moments; calculating a second derivative of the frequency of the power system at the moment through sampling values and sampling periods at three continuous moments; and calculating a virtual inertia factor considering the second order differential of the frequency through the second order derivative of the frequency of the power system at the moment.

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.

Step 1: the method comprises the steps of sampling frequency signals of a power system and sampling the rotating speed of the wind driven generator.

Step 2: and taking the real-time frequency of the power system as a feedback signal and solving a second derivative of the frequency of the power system.

And step 3: calculating a functional relation between a second derivative of the frequency of the electric power system and the active output variable quantity of the double-fed fan;

and 4, step 4: calculating a virtual inertia factor of the doubly-fed fan considering the second derivative of the frequency according to the functional relation in the step 2;

and 5: and (4) constructing an inertia control loop of the fan according to the functional relation in the step (3) and the virtual inertia factor in the step (4).