CN102355192B

CN102355192B - Control method of reactive power of doubly fed wind power generator

Info

Publication number: CN102355192B
Application number: CN2011102794331A
Authority: CN
Inventors: 杨柳; 刘嫣红; 毛志怀
Original assignee: China Agricultural University
Current assignee: China Agricultural University
Priority date: 2011-09-20
Filing date: 2011-09-20
Publication date: 2013-09-18
Anticipated expiration: 2031-09-20
Also published as: CN102355192A

Abstract

A method for controlling the reactive power of a doubly-fed wind power generator, the doubly-fed wind power generator has a doubly-fed motor, the motor has a stator that supplies power to a power grid, and the power grid has a voltage of a rated value; Drive the rotor, one end of the rotor is connected to the wind turbine through a variable speed gear, the rotor winding is a three-phase wound rotor winding, the power grid supplies power to the rotor through the converter, and the stator voltage and stator flux linkage are decomposed into synchronous rotation dq On the coordinate axis, the rotor current can be adjusted to control the reactive power output by the generator stator. This method does not need complex transformation and calculation such as vector rotation changes, the control sensitivity of the current control module is low, the circuit parameters of the converter system and the measurement delay have little influence on the current control, the control technology is simple, and the controller Therefore, the cost is reduced, which is suitable for the application of small-power wind turbines.

Description

Control Method of Reactive Power of Double-fed Wind Turbine Generator

技术领域 technical field

本发明涉及一种风力发电机，特别涉及连接到电网双馈风力发电机无功功率的控制方法。The invention relates to a wind power generator, in particular to a control method for reactive power of a doubly-fed wind power generator connected to a grid.

背景技术 Background technique

在能源消耗日益增长、环境污染日渐严重的今天，作为可再生绿色能源的风能受到世界各国的普遍重视，风力发电技术也成为近年来各国学者竞相研究的热点。风能是一种变化频繁的随机能源，变速恒频风力发电技术可以保证在绝大多数风速下的风能得到最大限度的捕获和利用，并具有传统恒速恒频风力发电技术所无法比拟的优越性，而双馈风力发电机能很好地满足变速恒频风力发电的技术要求，成为目前比较优化的一种控制策略。它是通过双PWM变流器在双馈发电机的转子侧施加三相交流电进行励磁，通过调节励磁电流的有效值、相位和频率，实现定子侧输出有功和无功功率的控制。Today, with increasing energy consumption and increasingly serious environmental pollution, wind energy, as a renewable green energy, has received widespread attention from all over the world, and wind power generation technology has also become a hot research topic among scholars from various countries in recent years. Wind energy is a random energy that changes frequently. The variable-speed constant-frequency wind power generation technology can ensure that the wind energy can be captured and utilized to the maximum at most wind speeds, and has incomparable advantages over the traditional constant-speed constant-frequency wind power generation technology. , and the doubly-fed wind turbine can well meet the technical requirements of variable-speed constant-frequency wind power generation, and has become a relatively optimized control strategy at present. It applies three-phase alternating current to the rotor side of the doubly-fed generator for excitation through the dual PWM converter, and realizes the control of the output active and reactive power of the stator side by adjusting the effective value, phase and frequency of the excitation current.

双馈风力发电机的的基本硬件拓扑如图1所示，发电机的定子直接连接到电网，转子绕组通过集电环经变流器与电网相连，通过控制转子电流的频率、有效值，相位和相序，利用双PWM变流器，通过SPWM控制技术，可以获得正弦波转子电流，以减小发电机中的谐波转矩，实现定子侧输出有功和无功功率的控制。The basic hardware topology of the double-fed wind turbine is shown in Figure 1. The stator of the generator is directly connected to the grid, and the rotor winding is connected to the grid through the collector ring through the converter. By controlling the frequency, effective value, and phase of the rotor current And phase sequence, using dual PWM converters, through SPWM control technology, can obtain sine wave rotor current to reduce the harmonic torque in the generator, and realize the control of stator side output active and reactive power.

由于双馈发电机的电路存在磁路上的耦合，且其三相坐标系下的数学模型是非线性、时变的高阶系统。为了实现有功、无功解耦控制，通常采用矢量控制法，矢量控制根据矢量变换理论，采用按定子磁场方向定向，把转子电流矢量分解为在同步旋转坐标系中的两个互相垂直的电流分量，实现对发电机有功功率和无功功率的解耦调节。但为使电机实现解耦，需要简化电机模型，还要进行矢量旋转变化等复杂的变换和计算，而且电流控制模块控制敏感度较高，变流器系统的电路参数、测量延时以及锁相环性能对电流控制都具有较大的影响，这些因素造成了矢量控制法的鲁棒性偏低。当电路参数，测量延时以及其他系统因素发生变化时，控制器稳定性会发生明显改变，加大了控制器参数的调试难度。Due to the coupling on the magnetic circuit of the doubly-fed generator circuit, and its mathematical model in the three-phase coordinate system is a nonlinear, time-varying high-order system. In order to realize the decoupling control of active and reactive power, the vector control method is usually adopted. According to the vector transformation theory, the vector control adopts the orientation according to the direction of the stator magnetic field, and decomposes the rotor current vector into two mutually perpendicular current components in the synchronous rotating coordinate system. , to realize the decoupling regulation of the active power and reactive power of the generator. However, in order to achieve decoupling of the motor, it is necessary to simplify the motor model and perform complex transformations and calculations such as vector rotation changes, and the control sensitivity of the current control module is high. The circuit parameters of the converter system, measurement delay and phase-locking The performance of the loop has a great influence on the current control, and these factors cause the robustness of the vector control method to be low. When the circuit parameters, measurement delay and other system factors change, the stability of the controller will change significantly, which increases the difficulty of debugging the controller parameters.

发明内容 Contents of the invention

本发明的目的在于克服现有双馈风力发电机无功功率控制方法的不足，提供一种不需要进行矢量旋转变化等复杂的变换和计算的双馈风力发电机无功功率控制方法。The purpose of the present invention is to overcome the shortcomings of the existing doubly-fed wind generator reactive power control method, and provide a doubly-fed wind generator reactive power control method that does not require complex transformations and calculations such as vector rotation changes.

设发电机的定子电压、电流、磁链矢量为

和

转子电压、电流、磁链矢量为和则在稳态运行时，电机电压方程为：Let the stator voltage, current and flux linkage vector of the generator be

and

The rotor voltage, current and flux vector are and Then in steady state operation, the motor voltage equation is:

${\overset{\cdot \cdot}{U u}}_{s the s} = = {R R}_{s the s} {\overset{\cdot \cdot}{I I}}_{s the s} + + j j {ω ω}_{s the s} {\overset{\cdot \cdot}{ψ ψ}}_{s the s} - - - - - - ((11))$

${\overset{\cdot &Center Dot;}{U u}}_{r r} = = {R R}_{r r} {\overset{\cdot \cdot}{I I}}_{r r} + + j j (({ω ω}_{s the s} - - {ω ω}_{r r})) {\overset{\cdot &Center Dot;}{ψ ψ}}_{s the s} - - - - - - ((22))$

其中R_s、R_r、ω_s、ω_r分别为电机定子、转子每相电阻，定子同步旋转磁场、转子旋转磁场的旋转角速度，式中矢量在空间相对静止，均以同步速度旋转，在同步旋转坐标dq轴系下Among them, R _s , R _r , ω _s , ω _r are the resistances of each phase of the motor stator and rotor, the rotational angular velocity of the synchronous rotating magnetic field of the stator and the rotating magnetic field of the rotor respectively. Under the rotating coordinate dq axis system

U_sd＝R_sI_sd+ω_sψ_sq (3)U _sd =R _s I _sd +ω _s ψ _sq (3)

U_sq＝R_sI_sq-ω_sψ_sd (4)U _sq ＝ R _s I _sq -ω _s ψ _sd (4)

其中ψ_sd、ψ_sq为

在d、q轴上的分量，其值为：Among them, ψ _sd and ψ _sq are

The components on the d and q axes are:

ψ_sd＝L_sI_sd+L_MI_rd (5)ψ _sd = L _s I _sd + L _M I _rd (5)

ψ_sq＝L_sI_sq+L_MI_rq (6)ψ _sq ＝ L _s I _sq + L _M I _rq (6)

其中，I_sd、I_sq分别为

在d、q轴上的分量，I_rd、I_rq分别为

在d、q轴上的分量。L_s为定子绕组自感，L_M为定转子绕组互感，由式(3)、(4)可得：Among them, I _sd and I _sq are respectively

The components on the d and q axes, I _rd and I _rq are respectively

Components on the d and q axes. L _s is the self-inductance of the stator winding, and L _M is the mutual inductance of the stator and rotor windings. From formulas (3) and (4), we can get:

${I I}_{sd sd} = = \frac{{U u}_{sd sd} - - {ω ω}_{s the s} {ψ ψ}_{sq sq}}{{R R}_{s the s}} - - - - - - ((77))$

${I I}_{sq sq} = = \frac{{U u}_{sq sq} + + {ω ω}_{s the s} {ψ ψ}_{sd sd}}{{R R}_{s the s}} - - - - - - ((88))$

将(7)、(8)代入(5)、(6)可得Substitute (7), (8) into (5), (6) to get

${U u}_{sd sd} = = \frac{{R R}_{s the s} {ψ ψ}_{sd sd} - - {R R}_{s the s} {L L}_{M m} {I I}_{rd rd}}{{L L}_{s the s}} + + {ω ω}_{s the s} {ψ ψ}_{sq sq} - - - - - - ((99))$

${U u}_{sq sq} = = \frac{{R R}_{s the s} {ψ ψ}_{sq sq} - - {R R}_{s the s} {L L}_{M m} {I I}_{rq rq}}{{L L}_{s the s}} - - {ω ω}_{s the s} {ψ ψ}_{sd sd} - - - - - - ((1010))$

而定子侧的无功功率Q为：And the reactive power Q on the stator side is:

Q＝U_sqI_sd-U_sdI_sq (11)Q＝U _sq I _sd -U _sd I _sq (11)

将式(9)、(10)代入(11)得：Substitute formulas (9), (10) into (11) to get:

$Q Q = = \frac{{ω ω}_{s the s}}{{L L}_{s the s}} (({ψ ψ}_{s the s}^{22} - - {ψ ψ}_{sd sd} {I I}_{rd rd} - - {ψ ψ}_{sq sq} {I I}_{rq rq})) - - - - - - ((1212))$

设X₁＝ψ_sdI_rd+ψ_sqI_rq Let X ₁ =ψ _sd I _rd +ψ _sq I _rq

则but

$Q Q = = \frac{{ω ω}_{s the s}}{{L L}_{s the s}} (({ψ ψ}_{s the s}^{22} - - {X x}_{11})) - - - - - - ((1313))$

当电机并联到无穷大电网时，Us恒定，ψ_s可近似为常数，Ls、ω_s也为常数，因此发电机定子输出的无功功率只与X₁有关，控制X₁就能实现对定子输出无功的控制，图2是定子磁链，转子电流矢量在dq同步旋转坐标轴上的分布，由图2可知，When the motor is connected in parallel to the infinite power grid, Us is constant, ψ _s can be approximated as a constant, and Ls and ω _s are also constant, so the reactive power output by the generator stator is only related to X ₁ , and controlling X ₁ can achieve output to the stator For reactive power control, Figure 2 shows the distribution of stator flux linkage and rotor current vector on the dq synchronous rotating coordinate axis, as can be seen from Figure 2,

其中A、B分别为与d轴的夹角，

为定子磁链与转子电流矢量间的夹角，则双馈风力发电机无功功率控制方法如图3。where A and B are respectively The angle with the d-axis,

is the angle between the stator flux linkage and the rotor current vector, then the reactive power control method of the doubly-fed wind turbine is shown in Figure 3.

发电机预先给定一转子励磁电流

在风力涡轮机拖动下，并入电网，则可测量定子输出的电压、电流U、I，并计算出定子输出的无功功率Q，根据磁链模型，可以计算出定子磁链。The generator pre-sets a rotor excitation current

When the wind turbine is dragged and connected to the power grid, the voltage, current U, and I output by the stator can be measured, and the reactive power Q output by the stator can be calculated. According to the flux linkage model, the stator flux linkage can be calculated.

给定定子输出无功功率为Q*，比较Q*与定子输出的无功功率Q，得到二者差值，利用PI调节算法可得到转子励磁电流Ir的给定值

控制器根据给定值调节变流器控制脉冲，得到转子励磁电流的输出。Given that the stator output reactive power is Q*, compare Q* with the reactive power Q* output by the stator to obtain the difference between the two, and use the PI adjustment algorithm to obtain the given value of the rotor excitation current Ir

The controller according to the given value Adjust the control pulse of the converter to obtain the output of the rotor excitation current.

由于本发明采用上述技术方案，在风力发电稳态运行中，无需进行矢量旋转变化等复杂的变换和计算，电流控制模块控制敏感度较低，变流器系统的电路参数、测量延时对电流控制都具有的影响较小，虽然控制的实时性和精度有所降低，但控制技术非常简单，控制器的成本也因此降低，适合小功率风力发电机的应用。Because the present invention adopts the above-mentioned technical scheme, in the steady-state operation of wind power generation, complex transformations and calculations such as vector rotation changes are not required, and the control sensitivity of the current control module is relatively low. The influence of the control is small, although the real-time and precision of the control are reduced, but the control technology is very simple, and the cost of the controller is therefore reduced, which is suitable for the application of small-power wind turbines.

附图说明 Description of drawings

图1是双馈风力发电机的的基本硬件拓扑结构；Figure 1 is the basic hardware topology of a doubly-fed wind turbine;

图2是根据本发明的双馈风力发电机定子磁链、转子电流矢量关系图；Fig. 2 is according to the doubly-fed wind power generator stator flux linkage of the present invention, rotor current vector diagram;

图3是根据本发明的双馈风力发电机无功功率控制框图。Fig. 3 is a block diagram of reactive power control of a doubly-fed wind power generator according to the present invention.

具体实施方式 Detailed ways

下面结合具体实施例对本发明做进一步的详细说明。The present invention will be further described in detail below in conjunction with specific embodiments.

双馈风力发电机的基本硬件拓扑结构如图1所示，电网通过变流器为双馈风力发电机的转子供电，发电机在风机驱动下，其定子向电网输出有功和无功。发电机参数测定有很多公知的方法，最常用的方法是利用空载和堵转试验来测定电机参数。利用文献1中的方法，也可以得到该发电机的参数，例如定子电阻R_s、定子绕组电感Ls、定转子绕组互感L_M等参数。The basic hardware topology of the DFIG is shown in Figure 1. The grid supplies power to the rotor of the DFIG through the converter. The generator is driven by the wind turbine, and its stator outputs active and reactive power to the grid. There are many known methods for measuring generator parameters, and the most commonly used method is to use no-load and locked-rotor tests to measure motor parameters. Using the method in Document 1, parameters of the generator can also be obtained, such as stator resistance R _s , stator winding inductance Ls, stator and rotor winding mutual inductance L _M and other parameters.

文献1：《矢量控制系统中异步电动机参数的估算和测量》，马小亮，电气传动，2010年第40卷第7期。Document 1: "Estimation and Measurement of Asynchronous Motor Parameters in Vector Control System", Ma Xiaoliang, Electric Drive, Volume 40, Issue 7, 2010.

通过光电编码盘可以检测发电机转子位置，进而通过微分可求出转子转速，从而得到电机转差频率ω₂。而观测定子磁链有三类方法：直接检测法、间接计算法，基于高频信号注入的方法。直接检测法是在定子α轴和β轴的气隙处嵌放磁敏元件，直接检测出定子磁链在定子α轴和β轴的分量ψ_αs和ψ_βs。据此可求得定子磁链的有效值ψ_s以及与α轴的夹角。间接计算法通过定子电压、电流等物理量建立磁链观测模型，在控制中实时推算定子磁链的有效值和相位。传统的方法是采用电压模型来观测定子磁链，并通过对反电动势信号的积分计算来得到定子磁链。由于这种方法具有需要的电机参数少和不需要转速信息的优点而得到了广泛应用，其表达式为：The rotor position of the generator can be detected through the photoelectric encoder disc, and then the rotor speed can be obtained through differentiation, so as to obtain the motor slip frequency ω ₂ . While observing the stator flux linkage There are three types of methods: direct detection methods, indirect calculation methods, and methods based on high-frequency signal injection. The direct detection method is to embed magnetic sensitive elements in the air gap between the stator α-axis and β-axis, and directly detect the components ψ _αs and ψ _βs of the stator flux linkage on the stator α-axis and β-axis. Based on this, the effective value ψ _s of the stator flux linkage and the included angle with the α axis can be obtained. The indirect calculation method establishes the flux linkage observation model through stator voltage, current and other physical quantities, and calculates the effective value and phase of the stator flux linkage in real time during control. The traditional method is to use the voltage model to observe the stator flux linkage, and obtain the stator flux linkage through the integral calculation of the back electromotive force signal. Because this method has the advantages of requiring less motor parameters and no speed information, it has been widely used, and its expression is:

ψ_s＝∫(U_s-i_sR_s)dtψ _s = ∫(U _s -i _s R _s )dt

基于高频信号注入的方法需要在异步电机的定子绕组中注入高频信号，通过电机的非理想特性如磁饱和效应等获取电机磁链的有效值和方向。The method based on high-frequency signal injection needs to inject a high-frequency signal into the stator winding of the asynchronous motor, and obtain the effective value and direction of the motor flux linkage through the non-ideal characteristics of the motor, such as the magnetic saturation effect.

在对双馈风力发电机无功功率控制时，首先利用空载和堵转试验来测定电机定子电阻R_s、定子绕组电感Ls、定转子绕组互感L_M等参数，发电机预先给定一转子励磁电流I_r，在风力涡轮机拖动下，并入电网，则可测量定子输出的电压、电流U、I，并计算出定子输出的无功功率Q，根据磁链模型，可以计算出定子磁链的有效值ψ_s和在αβ坐标轴相位，将其转化到dq旋转轴上，将预先给定的转子励磁电流I_r也映射到dq旋转轴上，则在该坐标轴上，定子磁链与转子励磁电流的夹角为令

给定定子输出无功功率为Q^*，比较Q^*与定子输出的无功功率Q，得到给定定子输出无功功率与定子实际输出的无功功率的差ΔQ＝Q^*-Q，利用PI增量调节算法可得到X₁的增量ΔX_K的值，When controlling the reactive power of doubly-fed wind turbines, first use no-load and locked-rotor tests to measure parameters such as motor stator resistance R _s , stator winding inductance Ls, and stator-rotor winding mutual inductance L _M . The excitation current I _r is connected to the power grid under the drag of the wind turbine, then the voltage, current U, and I output by the stator can be measured, and the reactive power Q output by the stator can be calculated. According to the flux linkage model, the stator flux can be calculated The effective value ψ _s of the chain and the phase on the αβ coordinate axis are converted to the dq rotation axis, and the pre-given rotor excitation current I _r is also mapped to the dq rotation axis, then on this coordinate axis, the stator flux linkage The included angle with the rotor excitation current is make

Given that the stator output reactive power is Q ^* , compare Q ^* with the reactive power Q output by the stator, and obtain the difference between the given stator output reactive power and the actual output reactive power of the stator ΔQ=Q ^* -Q, using PI The incremental adjustment algorithm can obtain the value of the increment ΔX _K of X ₁ ,

$Δ Δ {X x}_{K K} = = {K K}_{Q Q} ((Δ Δ {Q Q}_{K K} - - Δ Δ {Q Q}_{k k - - 11} + + \frac{T T}{{T T}_{Q Q}} Δ Δ {Q Q}_{K K}))$

其中，K_Q为比例系数，T_Q为积分时间常数，可通过常规的参数整定方法确定。而ΔQ_K、ΔQ_k-1为第K次与第K-1次采样周期中给定定子输出无功功率与定子实际输出的无功功率的差，T为一个采样周期的时间。则应输入的控制量为X_K＝X₁+ΔX_K，令

在X_K为一定值时，为使转子电流有效值不至太大，可以给定

为在0到60度之间任一角度

由于定子磁链的相位已根据磁链模型得出，令其与同步旋转轴的d轴夹角为A，

为dq轴上定子磁链与转子电流矢量间的夹角，因此可求出转子电流在dq轴上的相位，根据图2，可知，它与d轴夹角为

而转子电流矢量有效值为

因而，在变流控制器的控制作用下，向转子绕组输出与d轴夹角为

有效值为

转差频率的转子电流，即可输出需要的无功功率。Among them, K _Q is a proportional coefficient, and T _Q is an integral time constant, which can be determined by conventional parameter tuning methods. And ΔQ _K , ΔQ _k-1 are the difference between the given stator output reactive power and the actual output reactive power of the stator in the Kth and K-1th sampling periods, and T is the time of one sampling period. Then the control quantity that should be input is X _K ＝X ₁ +ΔX _K , let

When X _K is a certain value, in order to make the effective value of the rotor current not too large, it can be given

for any angle between 0 and 60 degrees

Since the phase of the stator flux linkage has been obtained according to the flux linkage model, the angle between it and the d-axis of the synchronous rotation axis is A,

is the angle between the stator flux linkage and the rotor current vector on the dq axis, so the phase of the rotor current on the dq axis can be obtained. According to Figure 2, it can be seen that the angle between it and the d axis is

The effective value of the rotor current vector is

Therefore, under the control of the variable current controller, the angle between the output to the rotor winding and the d-axis is

Valid values are

The rotor current at the slip frequency can output the required reactive power.

Claims

1. the control method of a double-fed wind power generator reactive power, described double-fed wind power generator has double feedback electric engine, and this motor has the stator to mains supply, and described electrical network has the voltage of rated value; Driving rotor with described stator coupling, described rotor one end is connected to wind turbine by change-speed gearing, described rotor winding is the three-phase wound rotor winding, electrical network is the rotor power supply by current transformer, described current transformer is connected with the rotor winding with collector ring by brush, and described method comprises the steps:

(a) utilize zero load and locked rotor test to measure the motor stator resistance R _s, stator winding inductance L s, rotor winding mutual inductance L _M, turn step (b);

(b) rotor excitation current given in advance

Under wind turbine drags, be connected to the grid, turn step (c);

(c) given stator output reactive power is Q ^*, turn step (d);

(d) given sampling period T detects generator rotor position by photoelectric coded disk, and then can obtain rotor speed by differential, thereby obtains motor slip frequency ω ₂, measure voltage, the current phasor U of the K time output of stator _K, I _K, and calculate the reactive power Q that stator is exported for the K time _K, wherein, K=1,2 ..., compare Q ^*With Q _K, obtain Q ^*With Q _KPoor Δ Q _K=Q ^*-Q _K, and with Δ Q _KStore in the memory cell of controller, measure or according to flux linkage model, calculate the effective value ψ of stator magnetic linkage _sAnd the phase place on static α β reference axis, its conversion to the dq synchronization rotational coordinate ax, is obtained the stator magnetic linkage vector and d axle clamp angle is A, with rotor excitation current

Also be mapped on the dq synchronization rotational coordinate ax, on the dq synchronization rotational coordinate ax, can obtain the angle of stator magnetic linkage and rotor excitation current

Order

Turn step (e);

(e) at Δ Q _KThe basis on, utilize PI incremental adjustments algorithm can obtain X ₁Increment Delta X _K, turn step (f);

(f) obtain X _K=X ₁+ Δ X _K, turn step (g);

(g) given For unspecified angle between 0 to 60 degree, under the control action of current-variable controller, upper and d axle clamp angle is to rotor winding output transform to synchronization rotational coordinate ax dq

Effective value is

Frequency is slip frequency ω ₂Rotor current; Turn step (h);

(h) make K=K+1, dq makes at synchronization rotational coordinate ax

Effective value be

Itself and d axle clamp angle are

Turn step (c).

2. the control method of double-fed wind power generator reactive power as claimed in claim 1, wherein in the step (e), PI incremental adjustments algorithm obtains X ₁Increment Delta X _KMethod be:

Δ X_{K} = K_{Q} (Δ Q_{K} - {ΔQ}_{K - 1} + \frac{T}{T_{Q}} Δ Q_{K})

Wherein, K _QBe proportionality coefficient, T _QBe integration time constant, can determine by conventional parameter tuning method, and Δ Q _K, Δ Q _K-1Be reactive power poor of given stator output reactive power and the actual output of stator in the K time and the K-1 time sampling period, T is the time in a sampling period.

3. the control method of double-fed wind power generator reactive power as claimed in claim 1, wherein in the step (C), flux linkage model is the u-i Voltage-Current model.

4. the control method of double-fed wind power generator reactive power as claimed in claim 1 wherein in the step (d), embeds magneto sensor at the air gap place of stator α axle and β axle, and direct-detection goes out stator magnetic linkage at the component ψ of stator α axle and β axle _{α s}And ψ _{β s}, can try to achieve accordingly the effective value ψ of stator magnetic linkage _sAnd with the angle of α axle.