技术领域technical field
本发明属于双馈风力发电机定频模型预测控制技术领域，具体涉及一种电网故障下双馈风力发电机转子磁链定频模型预测控制方法，用于有效提高双馈风力发电机在电网故障下的不脱网运行能力。The invention belongs to the technical field of fixed-frequency model predictive control of doubly-fed wind power generators, in particular to a doubly-fed wind power generator rotor flux fixed-frequency model predictive control method under power grid faults, which is used to effectively improve the performance of doubly-fed wind power generators in power grid faults The ability to operate without going offline.
背景技术Background technique
近年来，可再生能源技术得到快速发展，风能的利用在其中占据很大的比重。风能是一种清洁的能源，具有取之不尽、无污染等优点，是一种非常理想的新能源。风力发电占电力供应比例逐渐增大，双馈风力发电机是目前市场占有率和装机容量最大的机型，受电网故障的影响很大，因此研究电网电压跌落下双馈风力发电系统的控制和保护策略具有重要的理论意义，对提高风电机组的运行可靠性具有很大的实用价值。In recent years, renewable energy technology has developed rapidly, and the utilization of wind energy occupies a large proportion. Wind energy is a kind of clean energy, which has the advantages of inexhaustible and pollution-free, and is a very ideal new energy. The proportion of wind power generation in power supply is gradually increasing. The doubly-fed wind power generator is currently the model with the largest market share and installed capacity. It is greatly affected by grid failures. The protection strategy has important theoretical significance and has great practical value for improving the operation reliability of wind turbines.
在电网电压骤降的情况下，目前部分文献研究了基于撬棒保护控制策略，为了抑制电网电压跌落引起的双馈风力发电机转子侧过电流，撬棒电路被用来将双馈电机转子侧绕组短路，该短接回路为转子冲击电流提供一条通路，适当选择电阻值可以限制转子回路的最大电流，撬棒动作时双馈电机自动从系统中脱离。此种方法增加了硬件成本，故障时从电网吸收大量的无功功率，影响电网的稳定性，对电网的暂态电磁冲击和风力机的机械冲击均很严重。还有一些文献研究了采用了滞环控制器和查表法控制的直接功率控制方法，此方法消除了矢量控制中的电流控制环，简化了控制结构，但这种控制方式有变换器开关频率不固定的缺点，会导致宽频的谐波电流注入电网，造成滤波电抗器设计复杂。控制系统的响应速度和控制器的控制精度直接影响故障电流的抑制效果。本发明提出了电网故障下转子磁链定频模型预测控制方法，此控制算法开关频率恒定，无需较高的采样频率，控制精度高，在故障过程中可有效地控制转子电流在1.5-1.6倍额定电流以内，电磁转矩的波动较小，定子侧有功功率和无功功率波动较小，所有变量基于两相静止坐标系，无需复杂的坐标变换，转子磁链定频模型预测方法的控制频率设为基于定子磁场定向的矢量控制的2倍，提高了控制效率，对故障响应速度快，且避免了电网故障大扰动下控制器的饱和问题。可有效提高双馈风力发电机在电网电压故障下的不脱网运行能力。In the case of grid voltage sag, some literatures have studied the crowbar-based protection control strategy. In order to suppress the overcurrent on the rotor side of the doubly-fed wind turbine caused by the grid voltage drop, the crowbar circuit is used to control the rotor side of the doubly-fed generator The winding is short-circuited. The short-circuit circuit provides a path for the rotor surge current. Proper selection of the resistance value can limit the maximum current of the rotor circuit. When the crowbar moves, the doubly-fed motor is automatically separated from the system. This method increases the cost of hardware, and absorbs a large amount of reactive power from the grid when a fault occurs, which affects the stability of the grid, and the transient electromagnetic impact on the grid and the mechanical impact on the wind turbine are very serious. There are also some literatures that have studied the direct power control method using the hysteresis controller and the look-up table method. This method eliminates the current control loop in the vector control and simplifies the control structure, but this control method has the converter switching frequency The disadvantage of not being fixed will cause broadband harmonic current to be injected into the grid, resulting in complex filter reactor design. The response speed of the control system and the control accuracy of the controller directly affect the suppression effect of the fault current. The invention proposes a predictive control method of the fixed-frequency model of the rotor flux linkage under power grid faults. This control algorithm has a constant switching frequency, does not need a high sampling frequency, and has high control precision. During the fault process, the rotor current can be effectively controlled at 1.5-1.6 times Within the rated current, the fluctuation of electromagnetic torque is small, the fluctuation of active power and reactive power on the stator side is small, all variables are based on the two-phase stationary coordinate system, no complicated coordinate transformation is required, and the control frequency of the rotor flux linkage fixed frequency model prediction method It is set as twice that of the vector control based on stator field orientation, which improves the control efficiency, responds quickly to faults, and avoids the saturation problem of the controller under large disturbances of power grid faults. It can effectively improve the non-off-grid operation capability of the doubly-fed wind turbine under grid voltage failure.
发明内容Contents of the invention
本发明针对现有技术的不足提供了一种双馈风力发电机转子磁链定频模型预测控制方法，该控制方法响应速度快，控制精度高，开关频率固定，无需较高的采样频率，可有效降低纹波电流，在故障过程中控制转子电流在1.5-1.6倍额定电流以内，电磁转矩波动较小，减小了对机组的冲击，同时定子侧有功功率和无功功率波动较小。The present invention provides a doubly-fed wind generator rotor flux fixed-frequency model predictive control method aimed at the deficiencies of the prior art. Effectively reduce the ripple current, control the rotor current within 1.5-1.6 times the rated current during the fault process, the electromagnetic torque fluctuation is small, the impact on the unit is reduced, and the active power and reactive power fluctuation of the stator side are small.
本发明为解决上述技术问题采用如下技术方案，双馈风力发电机转子磁链定频模型预测控制方法，其特征在于：电网电压稳态运行时，双馈风力发电机转子侧变换器采用基于定子磁链定向的矢量控制，电网电压骤降故障运行时，双馈风力发电机采用转子磁链定频模型预测控制，该转子磁链定频模型预测控制的具体步骤为：In order to solve the above technical problems, the present invention adopts the following technical scheme, the doubly-fed wind power generator rotor flux fixed-frequency model predictive control method, which is characterized in that: when the power grid voltage is in steady state operation, the doubly-fed wind power generator rotor side converter adopts a stator-based Flux-oriented vector control, when the power grid voltage sags, the doubly-fed wind turbine adopts the predictive control of the fixed-frequency model of the rotor flux linkage, and the specific steps of the predictive control of the fixed-frequency model of the rotor flux linkage are as follows:
（1）、电网发生骤降故障时，设置转子磁链定频模型预测方法的控制频率为基于定子磁场定向的矢量控制的2倍；(1) When a sudden drop fault occurs in the power grid, set the control frequency of the rotor flux fixed-frequency model prediction method to twice that of the vector control based on the stator field orientation;
（2）、将测得的转子角速度ωr进行积分运算得到θr；(2) Integrating the measured rotor angular velocityωr to obtainθr ;
（3）、采集双馈风力发电机转子三相电压ura、urb、urc，转子三相电流ira、irb、irc和定子三相电流isa、isb、isc经过坐标转换得到定子参考两相静止坐标系下的转子两相电压urα、urβ，转子两相电流irα、irβ和定子两相电流isα、isβ；(3) Collect the rotor three-phase voltagesura ,urb ,urc of the doubly-fed wind turbine, the rotor three-phase currentsira ,irb ,irc and the stator three-phase currentsisa ,isb ,iscc are converted to get the rotor two-phase voltageurα ,urβ , the rotor two-phase currentirα ,irβ and the stator two-phase currentis in the stator reference two-phase static coordinate systemα ,isβ ;
（4）、将定子参考两相静止坐标系下的定子两相电流isα、isβ，转子两相电流irα、irβ，定子自感Ls，转子自感Lr和定转子间互感Lm进行定子磁链和转子磁链计算得到定子磁链α、β轴分量Ψsα、Ψsβ和转子磁链α、β轴分量Ψrα、Ψrβ；(4) Referring the stator to the stator two-phase current isα and isβ in the two-phase stationary coordinate system, the rotor two-phase currentirα andirβ , the stator self- inductanceLs , the rotor self-inductanceLr and The mutual inductanceLm between the stator and the rotor is used to calculate the stator flux and rotor flux to obtain the stator fluxα, β axis components Ψsα , Ψsβ and the rotor fluxα, β axis components Ψrα , Ψrβ ;
（5）、转子侧变换器电压分别由八个电压矢量表示，其中六个V1-V6为有效矢量，二个V0和V7为零矢量，当k=0、7时，Vk=0，当k=1、2、3、4、5、6时， ，Udc为直流侧电压；(5) The rotor-side converter voltage is represented by eight voltage vectors, among which sixV1 -V6 are effective vectors, and twoV0 andV7 are zero vectors. When k=0, 7,Vk =0, when k=1, 2, 3, 4, 5, 6, , Udc is the DC side voltage;
（6）、由定子参考两相静止坐标系下的转子两相电压urα、urβ计算出urα与urβ之间的夹角，进而判断出电压矢量所在的扇区，根据扇区选择的结果选择出扇区相邻的两个有效电压矢量，再加上一个零矢量，共同作用在一个开关周期，则这三个矢量中必然同时有可使转子磁链增加和减小的矢量；(6). Calculate the angle between urα andurβ by referring to the rotor two- phase voltageurα andurβ in the two-phase stationary coordinate system of the stator, and then determine the sector where the voltage vector is located. According to the results of sector selection, two effective voltage vectors adjacent to the sector are selected, plus a zero vector, which act together in one switching cycle, then there must be some of the three vectors that can increase and decrease the rotor flux linkage at the same time. small vector;
（7）、双馈风力发电机转子侧变换器电压在两相定子参考静止坐标系下的转子电压公式表示为：，，式中Rr为转子电阻，将当前选中的作用矢量代入转子电压公式可得到α、β轴磁链的变化率：，，k=0、1、2、3、4、5、6、7，Vk为当前作用的矢量，在当前作用矢量持续时间tn内，α、β轴转子磁链变化量表示为：，，式中：Ψrα(k)和Ψrβ(k)分别为当前矢量开始作用时刻α、β轴转子磁链值，Ψrα(k+1)和Ψrβ(k+1)分别为当前矢量作用结束时刻α、β轴转子磁链值；(7) The rotor voltage formula of the double-fed wind turbine rotor side converter voltage in the two-phase stator reference static coordinate system is expressed as: , , where Rr is the rotor resistance, and substituting the currently selected action vector into the formula of rotor voltage, the rate of change of theα andβ axis flux linkage can be obtained: , , k=0, 1, 2, 3, 4, 5, 6, 7, Vk is the current acting vector, within the duration of the current acting vectortn , the flux linkage variation of theα andβ axis rotors is expressed as: , , where: Ψrα (k) and Ψrβ (k) are the flux linkage values of theα andβ axis rotors at the moment when the current vector starts acting, respectively, Ψrα (k+1) and Ψrβ (k+1) Respectively, the flux linkage values of theα andβ axis rotors at the end time of the current vector action;
（8）、对转子磁链的给定值进行计算，即：Ψrαβ*=MΨsαβ，其中，Ψrαβ*为转子磁链α、β轴的给定值，Ψsαβ为定子磁链α、β轴的实际值，Irαβ为定子参考两相静止坐标系下的转子两相电流额定值，控制转子两相电流在其额定值附近波动，故障期间M随Ψsαβ变换自适应改变，实现对转子磁链的实时最优控制，同时也实现对定转子磁链进行同步弱磁控制；(8) Calculate the given value of the rotor flux linkage, namely: Ψrαβ* =M Ψsαβ , where , Ψrαβ* is the given value of rotor flux linkageα ,β axis, Ψsαβ is the actual value of stator flux linkageα ,β axis,Irαβ is the rotor two-phase current in the stator reference two-phase stationary coordinate system The rated value controls the two-phase current of the rotor to fluctuate around its rated value. During the fault period,M changes adaptively with the transformation of Ψsαβ , realizing real-time optimal control of the rotor flux linkage, and also realizing synchronous flux weakening of the stator and rotor flux linkage control;
（9）、电压矢量作用时间的计算，设定在一个开关周期Ts内所选三个电压矢量的作用时间分为t0、t1、t2，其中t0为零矢量的作用时间，t1、t2为两个有效矢量的作用时间，t0+t1+t2=Ts，则一个开关周期结束，转子磁链跟踪误差用下列函数表示：，，式中：，，eα0、eα1、eα2分别为所选矢量作用下的α轴的转子磁链变化率，eβ0、eβ1、eβ2分别为所选矢量作用下的β轴的转子磁链变化率；(9) Calculation of the action time of the voltage vector, set the action time of the three voltage vectors selected within a switching periodTs intot0 ,t1 ,t2 , wheret0 is the action time of the zero vector,t1 andt2 are the action time of the two effective vectors,t0 +t1 +t2 =Ts , then a switching cycle ends, and the rotor flux linkage tracking error is expressed by the following function: , , where: , , eα 0 , eα 1 , eα 2 are respectively the change rate of the rotor flux linkage of theα- axis under the action of the selected vector, and eβ 0 , eβ 1 , eβ 2 are theβ- axis under the action of the selected vector The rate of change of rotor flux linkage;
（10）、双馈风力发电机转子磁链定频模型预测控制的目标是在每个开关周期结束时刻，使实际转子磁链值与给定转子磁链误差最小，每个控制周期内最大限度的减小α、β轴转子磁链误差，采用最小二乘优化算法定义价值函数为：，以价值函数W最小为约束条件，求出每个控制周期Ts内三个矢量的最佳作用时间；(10) The goal of the doubly-fed wind turbine rotor flux fixed-frequency model predictive control is to minimize the error between the actual rotor flux value and the given rotor flux value at the end of each switching cycle, and to maximize the error in each control cycle. To reduce the flux linkage error of theα andβ axis rotors, the least squares optimization algorithm is used to define the value function as: , with the minimum value function W as the constraint condition, find the best action time of the three vectors in each control cycleTs ;
（11）、电压矢量作用时间的计算满足下列条件：，，由步骤（8）、（9）以及本步骤中的公式求得各矢量的作用时间分别为：，t0=Ts-t1-t2；(11) The calculation of the voltage vector action time satisfies the following conditions: , , the action time of each vector obtained from steps (8), (9) and the formula in this step are: ,t0 =Ts -t1 -t2 ;
（12）、在某个控制周期内，当两个有效电压矢量的作用时间之和t1+t2>Ts时，零矢量不再作用，两个有效电压矢量的作用时间调整为：，，最后采用空间矢量调制得到各桥臂开关的状态。(12) In a certain control period, when the sum of the action time of the two effective voltage vectorst1 +t2 >Ts , the zero vector no longer acts, and the action time of the two effective voltage vectors is adjusted as follows: , , and finally use space vector modulation to obtain the state of each bridge arm switch.
当电网电压发生单相跌落60%或者三相对称跌落60%故障时，目前大多数控制方法对故障期间转子电流值一般控制在其额定电流的2倍左右，电磁转矩波动比较大，对机组的冲击力很大。本发明电网电压骤降故障下双馈风力发电机采用转子磁链定频模型预测控制，主要是对转子侧变换器的控制，通过对转子磁链的实时最优控制，有效抑制转子故障电流；故障期间转子磁链定频模型预测方法可有效避免电网故障大扰动下控制器的饱和问题。故障下控制系统的控制频率调整为基于定子磁场定向的矢量控制的2倍，提高了控制频率，实现对故障的快速响应，进一步提高了电流抑制效果，同时所有变量基于两相静止参考坐标系，无需复杂的坐标变换，在故障瞬间可有效地控制转子电流在其额定电流的1.5-1.6倍以内。When the power grid voltage has a single-phase drop of 60% or a three-phase symmetrical drop of 60%, most of the current control methods generally control the rotor current value during the fault period to about 2 times its rated current, and the electromagnetic torque fluctuation is relatively large. The impact is great. The doubly-fed wind power generator in the present invention adopts the predictive control of the fixed-frequency model of the rotor flux linkage under the grid voltage sag fault, mainly for the control of the converter on the rotor side, and through the real-time optimal control of the rotor flux linkage, the rotor fault current is effectively suppressed; The fixed-frequency model prediction method of rotor flux linkage during the fault period can effectively avoid the saturation problem of the controller under the large disturbance of the power grid fault. The control frequency of the control system under fault is adjusted to twice that of the vector control based on the stator field orientation, which increases the control frequency, realizes a quick response to the fault, and further improves the current suppression effect. At the same time, all variables are based on the two-phase stationary reference frame. Without complex coordinate transformation, the rotor current can be effectively controlled within 1.5-1.6 times of its rated current at the moment of fault.
附图说明Description of drawings
图1为定子参考两相静止α β坐标系中DFIG矢量形式等效电路；Figure 1 is the equivalent circuit of the DFIG vector form in the stator reference two-phase staticα β coordinate system;
图2为控制结构框图；Fig. 2 is a control structure block diagram;
图3为电网电压发生三相对称跌落60%故障时转子磁链定频模型预测控制的运行结果图；Figure 3 is a diagram of the operation results of the predictive control of the fixed-frequency model of the rotor flux linkage when the three-phase symmetrical drop of 60% of the grid voltage occurs;
图4为电网电压发生单相跌落60%故障时转子磁链定频模型预测控制的运行结果图。Figure 4 is a diagram of the operation results of the predictive control of the fixed-frequency model of the rotor flux linkage when the grid voltage has a single-phase drop of 60% fault.
具体实施方法Specific implementation method
下面结合附图对本发明做进一步说明。图1为定子参考两相静止α β坐标系中DFIG矢量形式等效电路，、分别为定子两相电压与转子两相电压；、分别为定子两相电压与转子两相电压；Rs、Rr分别为定子电阻与转子电阻；Lls、Llr、Lm分别表示定子漏感、转子漏感以及定转子之间的互感；、分别表示定子磁链和转子磁链。The present invention will be further described below in conjunction with the accompanying drawings. Figure 1 is the equivalent circuit of the DFIG vector form in the stator reference two-phase staticα β coordinate system, , are the stator two-phase voltage and the rotor two-phase voltage respectively; , are stator two-phase voltage and rotor two-phase voltage respectively;Rs ,Rr are stator resistance and rotor resistance respectively;Lls, Llr, Lm represent stator leakage inductance, rotor leakage inductance and mutual inductance between stator and rotor respectively; , are the stator flux and rotor flux, respectively.
双馈风力发电机在定子参考两相静止坐标系下的基本电压方程如下所示：The basic voltage equation of the double-fed wind turbine in the stator reference two-phase stationary coordinate system is as follows:
（1） (1)
（2） (2)
（3） (3)
（4） (4)
式中：usα、usβ分别为定子参考两相静止坐标系下的定子两相电压，urα、urβ分别为定子参考两相静止坐标系下的转子两相电压，Rs、Rr分别为定子电阻和转子电阻，isα、isβ分别为定子参考两相静止坐标系下的定子两相电流，irα、irβ分别为定子参考两相静止坐标系下的转子两相电流，Ψsα、Ψsβ分别定子参考两相静止坐标系下的定子磁链，Ψrα、Ψrβ分别表示定子参考两相静止坐标系下的转子磁链，ωr表示发电机转子角速度。In the formula:usα andusβ are the stator two-phase voltages in the stator reference two-phase stationary coordinate system respectively,urα andurβ are the rotor two-phase voltages in the stator reference two-phase stationary coordinate system respectively,Rs ,Rr are stator resistance and rotor resistance respectively, isα, isβ are stator two-phase currents in stator reference two-phase stationary coordinate system,ir α,irβ are stator reference two-phase stationary coordinates respectively Ψsα , Ψsβ represent the stator flux linkage in the two-phase stationary coordinate system, Ψrα , Ψrβ respectively represent the rotor flux linkage in the stator reference two-phase stationary coordinate system ,ωr represents the generator rotor angular velocity.
双馈风力发电机定子磁链和转子磁链方程如下所示：The stator flux and rotor flux equations of the doubly-fed wind turbine are as follows:
Ψsα=Lsisα+Lmirα （5）Ψsα =Lsisα +Lmirα (5)
Ψsβ=Lsisβ+Lmirβ （6）Ψsβ =Lsisβ +Lmirβ (6)
Ψrα=Lmisα+Lrirα （7）Ψrα =Lmisα +Lrirα (7)
Ψrβ=Lmisβ+Lrirβ （8）Ψrβ =Lmisβ +Lrirβ (8)
式中：Ls、Lr、Lm分别表示定子自感、转子自感以及定转子之间的互感。In the formula:Ls, Lr, Lm represent stator self-inductance, rotor self-inductance and mutual inductance between stator and rotor, respectively.
由定子参考两相静止坐标系下的转子电压urα、urβ，计算出urα与urβ之间的夹角，进而判断出电压矢量所在的扇区，根据扇区选择的结果，选择出扇区相邻的两个有效电压矢量，再加上一个零矢量，共同作用在一个开关周期，则这三个矢量中必然同时有可使转子磁链增加和减小的矢量。The stator refers to the rotor voltageurα andurβ in the two-phase stationary coordinate system, calculates the angle betweenurα andurβ , and then judges the sector where the voltage vector is located. According to the selected sector As a result, two effective voltage vectors adjacent to the sector are selected, plus a zero vector, to act together in one switching cycle, and there must be a vector that can increase and decrease the rotor flux linkage among the three vectors at the same time.
把当前选中的作用矢量代入转子电压公式（3）、（4）可得到α、β轴磁链的变化率：Substituting the currently selected action vector into the rotor voltage formulas (3) and (4), the rate of change of the α and β axis flux linkage can be obtained:
（9） (9)
（10） (10)
式中：k=0、1、2、3、4、5、6、7；eαi、eβi分别为不同电压矢量作用下转子磁链的变化率；Vk为当前作用的电压矢量。In the formula: k=0, 1, 2, 3, 4, 5, 6, 7; eαi and eβi are the change rates of the rotor flux linkage under different voltage vectors respectively;Vk is the current acting voltage vector.
在当前作用矢量持续时间tn内，α、β轴转子磁链变化量可表示为：Within the duration of the current action vectortn , the flux linkage variation of theα andβ axis rotors can be expressed as:
（11） (11)
（12） (12)
式中：Ψrα(k)和Ψrβ(k)分别为当前矢量开始作用时刻α、β轴转子磁链值；Ψrα(k+1)和Ψrβ(k+1)分别为当前矢量作用结束时刻α、β轴转子磁链值。In the formula: Ψrα (k) and Ψrβ (k) are the flux linkage values of theα andβ axis rotors at the moment when the current vector starts to act, respectively; Ψrα (k+1) and Ψrβ (k+1) are respectively It is the flux linkage value of theα andβ axis rotors at the end time of the current vector action.
对转子磁链的给定值进行计算，如下所示：The given value of the rotor flux linkage is calculated as follows:
Ψrαβ*=MΨsαβ （13）Ψrαβ* =M Ψsαβ (13)
式中：，Ψrαβ*为转子磁链α、β轴的给定值，Ψsαβ为定子磁链α、β轴的实际值，Irαβ为定子参考两相静止坐标系下的转子两相电流额定值。M与转子电流和定子磁链有关，转子两相电流在故障期间取其额定值，这样可以控制转子两相电流在其额定值附近波动，在故障期间M随Ψsαβ变换自适应改变，实现对转子磁链的实时最优控制，同时也实现对定转子磁链进行同步弱磁控制。In the formula: , Ψrαβ* is the given value of rotor flux linkageα ,β axis, Ψsαβ is the actual value of stator flux linkageα ,β axis,Irαβ is the rotor two-phase current in the stator reference two-phase stationary coordinate system rated value.M is related to the rotor current and stator flux linkage. The rotor two-phase current takes its rated value during the fault period, so that the rotor two-phase current can be controlled to fluctuate around its rated value. During the fault period,M changes adaptively with Ψsαβ transformation to realize The real-time optimal control of the rotor flux linkage also realizes the synchronous flux weakening control of the stator and rotor flux linkage.
电压矢量作用时间的计算，设定在一个开关周期Ts内所选三个电压矢量的作用时间分为t0、t1、t2，其中t0为零矢量的作用时间，t1、t2为两个有效矢量的作用时间（t0+t1+t2=Ts）。则一个开关周期结束，转子磁链跟踪误差可用下列函数表示：Calculation of the action time of the voltage vector, set the action time of the three selected voltage vectors in a switching cycleTs intot0 ,t1 ,t2 , wheret0 is the action time of the zero vector,t1 ,t2 is the action time of the two effective vectors (t0 +t1 +t2 =Ts ). Then a switching cycle ends, and the rotor flux tracking error can be expressed by the following function:
（14） (14)
（15） (15)
式中：，；eα0、eα1、eα2分别为所选矢量作用下的α轴的转子磁链变化率；eβ0、eβ1、eβ2分别为所选矢量作用下的β轴的转子磁链变化率。In the formula: , ; eα 0 , eα 1 , eα 2 are respectively the change rate of the rotor flux linkage of theα- axis under the action of the selected vector; eβ 0 , eβ 1 , eβ 2 are theβ- axis under the action of the selected vector The rate of change of rotor flux linkage.
双馈风力发电机转子磁链定频模型预测控制的目标是在每个开关周期结束时刻，使实际转子磁链值与给定转子磁链误差最小。为了在每个控制周期内最大限度的减小α、β轴转子磁链误差，采用最小二乘优化算法定义价值函数为：The goal of fixed-frequency model predictive control of doubly-fed wind turbine rotor flux is to minimize the error between the actual rotor flux value and the given rotor flux at the end of each switching cycle. In order to minimize the flux linkage errors of theα andβ axis rotors in each control cycle, the least square optimization algorithm is used to define the value function as:
（16） (16)
以价值函数最小为约束条件，可以求出每个控制周期内三个矢量的最佳作用时间。value function The minimum is the constraint condition, and each control cycle can be found The optimal action time of the three vectors in .
电压矢量作用时间的计算应满足下列条件：The calculation of voltage vector action time should meet the following conditions:
（17） (17)
（18） (18)
联立式（14）、式（15）、式（16）、式（17）和式（18）可得各矢量作用时间t0、t1、t2为：Simultaneous formula (14), formula (15), formula (16), formula (17) and formula (18) can get each vector action timet0 ,t1 ,t2 as:
（19） (19)
（20） (20)
t0=Ts-t1-t2 （21）t0 =Ts -t1 -t2 (21)
在某个控制周期内，当两个有效电压矢量的作用时间之和t1+t2>Ts时，零矢量不再作用，两个有效电压矢量的作用时间调整为：In a certain control cycle, when the sum of the action time of thetwo effective voltage vectors ist1+t2>Ts , the zero vector is no longer active, and the action time of the two effective voltage vectors is adjusted as follows:
（22） (twenty two)
（23） (twenty three)
采用空间矢量调制得到各桥臂的开关状态。The switching state of each bridge arm is obtained by space vector modulation.
双馈风力发电机转子磁链定频模型预测控制开关频率恒定，可有效降低纹波电流和电流失真。定转子磁链的关系直接影响定转子电流的大小，定频模型预测控制方法根据转子磁链误差选择三个矢量的最佳作用时间，使转子磁链实际大小和最优转子磁链给定误差最小，实现了转子磁链的实时最优控制。所有变量基于两相静止参考坐标系，无需复杂的坐标变换，同时采用倍频的模型预测控制，两者都提高了控制器的响应速度，该控制方法在故障过程中可有效地控制转子电流在1.5-1.6倍额定电流以内，电磁转矩的波动较小，定子侧有功功率和无功功率波动较小。The fixed-frequency model of doubly-fed wind turbine rotor flux linkage predicts and controls the switching frequency to be constant, which can effectively reduce the ripple current and current distortion. The relationship between the stator and rotor flux directly affects the magnitude of the stator and rotor current. The fixed frequency model predictive control method selects the best action time of the three vectors according to the rotor flux error, so that the actual size of the rotor flux and the given error of the optimal rotor flux Minimum, real-time optimal control of the rotor flux linkage is realized. All variables are based on the two-phase stationary reference coordinate system, without complex coordinate transformation. At the same time, the model predictive control of frequency multiplication is adopted, both of which improve the response speed of the controller. This control method can effectively control the rotor current in the fault process. Within 1.5-1.6 times the rated current, the fluctuation of electromagnetic torque is small, and the fluctuation of active power and reactive power on the stator side is small.
图2为电网故障下转子定频模型预测控制框图。其具体步骤如下：（1）、将测得的转子角速度ωr进行积分运算得到θr；（2）、采集双馈风力发电机转子三相电压ura、urb、urc，转子三相电流ira、irb、irc和定子三相电流isa、isb、isc经过坐标转换得到定子参考两相静止坐标系下的转子两相电压urα、urβ，转子两相电流irα、irβ和定子两相电流isα、isβ；（3）、将定子参考两相静止坐标系下的定子两相电流isα、isβ，转子两相电流irα、irβ，定子自感Ls，转子自感Lr和定转子间互感Lm进行定子磁链和转子磁链计算得到定子磁链α、β轴分量Ψsα、Ψsβ和转子磁链α、β轴分量Ψrα、Ψrβ；（4）、转子侧变换器电压可分别有八个电压矢量表示，其中六个为有效矢量（V1-V6），二个为零矢量（V0，V7），当k=0、7时，Vk=0,；当k=1、2、3、4、5、6时，，Udc为直流侧电压；（5）、由定子参考两相静止坐标系下的转子电压urα、urβ计算出urα与urβ之间的夹角，进而判断出电压矢量所在的扇区，根据扇区选择的结果，选择出扇区相邻的两个有效电压矢量，再加上一个零矢量，共同作用在一个开关周期，则这三个矢量中必然同时有可使转子磁链增加和减小的矢量；（6）、双馈风力发电机转子侧变换器电压在两相定子参考静止坐标系下的转子电压公式表示为：，，式中Rr为转子电阻，因此把当前选中的作用矢量代入转子电压公式可得到α、β轴磁链的变化率：，，k=0、1、2、3、4、5、6、7，Vk为当前作用的矢量，在当前作用矢量持续时间tn内，α、β轴转子磁链变化量可表示为：，；式中：Ψrα(k)和Ψrβ(k)分别为当前矢量开始作用时刻α、β轴转子磁链值；Ψrα(k+1)和Ψrβ(k+1)分别为当前矢量作用结束时刻α、β轴转子磁链值；（7）、对转子磁链的给定值进行计算，即：Ψrαβ*=MΨsαβ，其中，Ψrαβ*为转子磁链α、β轴的给定值，Ψsαβ为定子磁链α、β轴的实际值，Irαβ为定子参考两相静止坐标系下的转子电流额定值，这样可以控制转子电流在其额定值附近波动，在故障期间M可以随Ψsαβ变换自适应改变，实现对转子磁链的实时最优控制，同时也实现对定转子磁链进行同步弱磁控制；（8）、电压矢量作用时间的计算，设定在一个开关周期Ts内所选三个电压矢量的作用时间分为t0、t1、t2，其中t0为零矢量的作用时间，t1、t2为两个有效矢量的作用时间（t0+t1+t2=Ts），则一个开关周期结束，转子磁链跟踪误差可用下列函数表示：，，式中：，，eα0、eα1、eα2分别为所选矢量作用下的α轴的转子磁链变化率，eβ0、eβ1、eβ2分别为所选矢量作用下的β轴的转子磁链变化率；（9）、双馈风力发电机转子磁链定频模型预测控制的目标是在每个开关周期结束时刻，使实际转子磁链值与给定转子磁链误差最小，为了在每个控制周期内最大限度的减小α、β轴转子磁链误差，采用最小二乘优化算法定义价值函数为：，以价值函数最小为约束条件，可以求出每个控制周期内三个矢量的最佳作用时间；（10）、电压矢量作用时间的计算应满足下列条件：，；由步骤（8）、（9）以及本步骤中的公式，可以求得各矢量的作用时间为：，t0=Ts-t1-t2；（11）、在某个控制周期内，当两个有效电压矢量的作用时间之和t1+t2>Ts时，零矢量不再作用，两个有效电压矢量的作用时间调整为：，，最后采用空间矢量调制得到各桥臂开关的状态。Figure 2 is a block diagram of the predictive control of the fixed frequency model of the rotor under grid faults. The specific steps are as follows: (1), integrate the measured rotor angular velocityωr to obtainθr ; (2), collect the three-phase voltagesura ,urb ,urc of the double-fed wind turbine rotor, Rotor three-phase currentira ,irb ,irc and stator three-phase current isa ,isb, isc undergo coordinate conversion to obtain the rotor two-phase voltageur in the stator reference two-phase stationary coordinate systemα ,urβ , the rotor two-phase currentirα ,irβ and the stator two-phase current isα ,isβ ; (3), refer the stator to the stator two-phase currentis in the two-phase stationary coordinate systemα , isβ , rotor two-phase currentirα ,irβ , stator self-inductanceLs , rotor self-inductanceLr and mutual inductanceLm between stator and rotor arecalculated for stator flux linkage and rotor flux linkage to obtain stator flux linkageα , β- axis components Ψsα , Ψsβ and rotor flux linkageα, β- axis components Ψrα , Ψrβ ; (4) The converter voltage on the rotor side can be represented by eight voltage vectors, six of which are Effective vector (V1 -V6 ), two zero vectors (V0 ,V7 ), when k=0, 7,Vk =0,; when k=1, 2, 3, 4, 5, 6 o'clock, ,Udc is the DC side voltage; (5), the angle betweenurα andurβ is calculated from the stator reference rotor voltageurα and urβ in the two-phase stationary coordinate system, and then the voltage is judged The sector where the vector is located, according to the result of sector selection, select two effective voltage vectors adjacent to the sector, plus a zero vector, and act together in one switching cycle, then there must be possible The vector that increases and decreases the rotor flux linkage; (6), the rotor voltage formula of the double-fed wind turbine rotor side converter voltage in the two-phase stator reference stationary coordinate system is expressed as: , , whereRr is the rotor resistance, so substituting the currently selected action vector into the rotor voltage formula can obtain the change rate of theα andβ axis flux linkage: , , k=0, 1, 2, 3, 4, 5, 6, 7,Vk is the current acting vector, within the duration of the current acting vectortn , the variation ofα andβ axis rotor flux linkage can be expressed as: , ; where: Ψrα (k) and Ψrβ (k) are the flux linkage values of theα andβ axis rotors at the moment when the current vector starts to act, respectively; Ψrα (k+1) and Ψrβ (k+1) are respectively theα andβ axis rotor flux linkage values at the end of the current vector action; (7), calculate the given value of the rotor flux linkage, namely: Ψrαβ* =M Ψsαβ , where , Ψrαβ* is the given value of the rotor flux linkageα ,β axis, Ψsαβ is the actual value of the stator flux linkageα ,β axis,Irαβ is the rated value of the rotor current in the stator reference two-phase stationary coordinate system , so that the rotor current can be controlled to fluctuate around its rated value. During the fault period,M can be adaptively changed with Ψsαβ transformation, realizing real-time optimal control of the rotor flux linkage, and at the same time realizing synchronous flux weakening of the stator and rotor flux linkage (8) Calculation of the action time of the voltage vector, set the action time of the three selected voltage vectors in a switching cycleTs intot0 ,t1 ,t2 , wheret0 is the action of the zero vector time,t1 andt2 are the action time of the two effective vectors (t0 +t1 +t2 =Ts ), then a switching cycle ends, and the rotor flux tracking error can be expressed by the following function: , , where: , , eα 0 , eα 1 , eα 2 are respectively the change rate of the rotor flux linkage of theα- axis under the action of the selected vector, and eβ 0 , eβ 1 , eβ 2 are theβ- axis under the action of the selected vector (9) The target of the double-fed wind turbine rotor flux fixed-frequency model predictive control is to minimize the error between the actual rotor flux value and the given rotor flux value at the end of each switching cycle, In order to minimize the flux linkage errors of theα andβ axis rotors in each control cycle, the least square optimization algorithm is used to define the value function as: , with the value function The minimum is the constraint condition, and each control cycle can be found The best action time of the three vectors within; (10), the calculation of the voltage vector action time should meet the following conditions: , ; From steps (8), (9) and the formula in this step, the action time of each vector can be obtained as: ,t0 =Ts -t1 -t2 ; (11), in a certain control period, when the sum of the action time of two effective voltage vectors ist1 +t2 >Ts , the zero vector will no longer act , the action time of the two effective voltage vectors is adjusted as: , , and finally use space vector modulation to obtain the state of each bridge arm switch.
图3为电网电压发生三相对称跌落60%故障时转子磁链定频模型预测控制的运行结果图，从图中可以看出，电磁转矩几乎为零，波动较小，在电网稳定运行时，转子电流为2000A，当故障发生时，采用转子磁链定频模型预测控制，此时转子电流为3000A，转子电流控制在1.5倍额定峰值电流以内。Figure 3 is the operation result diagram of the predictive control of the fixed-frequency model of the rotor flux linkage when the grid voltage has a three-phase symmetrical drop of 60%. It can be seen from the figure that the electromagnetic torque is almost zero and the fluctuation is small. When the grid is running stably , the rotor current is 2000A. When a fault occurs, the rotor flux linkage constant frequency model is used for predictive control. At this time, the rotor current is 3000A, and the rotor current is controlled within 1.5 times the rated peak current.
图4为电网电压发生单相跌落60%故障时转子磁链定频模型预测控制的运行结果图，从图中可以看出，电磁转矩几乎为零，波动较小，在电网稳定运行时，转子电流为2000A，当故障发生时，采用转子磁链定频模型预测控制，此时转子电流为3200A，转子电流控制在1.6倍额定峰值电流以内。Figure 4 is the operation result diagram of the predictive control of the fixed frequency model of the rotor flux linkage when the grid voltage has a single-phase drop of 60%. It can be seen from the figure that the electromagnetic torque is almost zero and the fluctuation is small. When the grid is running stably, The rotor current is 2000A. When a fault occurs, the rotor flux linkage constant frequency model predictive control is adopted. At this time, the rotor current is 3200A, and the rotor current is controlled within 1.6 times the rated peak current.
以上实施例描述了本发明的基本原理、主要特征及优点，本行业的技术人员应该了解，本发明不受上述实施例的限制，上述实施例和说明书中描述的只是说明本发明的原理，在不脱离本发明原理的范围下，本发明还会有各种变化和改进，这些变化和改进均落入本发明保护的范围内。The above embodiments have described the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What are described in the above embodiments and description are only to illustrate the principles of the present invention. Without departing from the scope of the principle of the present invention, there will be various changes and improvements in the present invention, and these changes and improvements all fall within the protection scope of the present invention.
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| CN201510393259.1ACN104967377B (en) | 2015-07-07 | 2015-07-07 | Double-fed wind power generator rotor magnetic linkage determines frequency model predictive control method |
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| CN201510393259.1ACN104967377B (en) | 2015-07-07 | 2015-07-07 | Double-fed wind power generator rotor magnetic linkage determines frequency model predictive control method |
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| CB03 | Change of inventor or designer information | Inventor after:Wang Meng Inventor after:Liu Yuwei Inventor after:Shi Yanyan Inventor after:Jing Jianwei Inventor after:Dai Yaying Inventor before:Wang Meng Inventor before:Dai Yaying Inventor before:Shi Yanyan Inventor before:Wang Yan Inventor before:Gao Jinhui | |
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| CF01 | Termination of patent right due to non-payment of annual fee | Granted publication date:20171201 Termination date:20190707 |