【作者】 肖磊；

【导师】 黄守道；

【作者基本信息】 湖南大学 ， 电气工程， 2013， 博士

【摘要】 随着直驱式永磁同步风电机组容量的不断增加，它对电网的重要性也日益明显，直接影响到所并电网运行的稳定性和电能质量，因此，电网运营商从电网安全角度出发，提出了风电机组在外部电网故障时还应有不脱网运行（穿越）能力。目前，我国现有的直驱式永磁同步风电机组控制仅局限于平衡电网下运行，但真实的电网时刻有可能存在着电压瞬变及不对称故障。直驱式永磁同步风电机组变速恒频运行采用理想大电网条件下的控制策略，不能适应我国风电机组一般所并弱电网的现实，也不能从控制上保证风电系统的运行安全，因此，必须建立适应故障穿越的控制新模型，确立新的控制策略和技术。在此背景下，本文选择直驱式永磁同步风力发电机为研究对象，将对直驱风电系统在不平衡电网电压下的运行与控制进行研究。本文利用空间矢量法建立了直驱式永磁同步风力发电机的统一数学模型，然后在此模型基础上研究了电网电压正常时，电网稳态小值不平衡电网电压时与电网发生不对称故障所引起的大值不平衡电网电压时的直驱式永磁同步风力发电机控制策略。本文以湘潭电机股份有限公司(XE-82型)2MW永磁同步风力电机为例，对不平衡电网电压下永磁同步风力发电机的运行与控制技术进行了仿真分析，同时以2kW背靠背双PWM变流器为例进行了实验分析，实现了采用背靠背全功变流器直驱式永磁同步风力发电机在小值与大值不平衡电网电压下的运行控制，仿真与实验表明本文所提的控制策略运用于永磁同步风力发电机的故障运行时可行的，对实现永磁同步风力发电机不对称故障穿越具有参考意义，本文主要研究内容和创新性的成果如下：(1)在直驱式永磁同步风力发电机数学模型的基础上研究了电网电压正常时适用于该系统的一种稳态控制策略并进行了仿真验证。为进一步研究直驱式永磁同步风力发电机在电网异常条件下的运行与控制奠定了基础。通过在直流侧母线侧加入能量泄放环节在仿真中实现了电网电压对称跌落至额定电压20%工况下的穿越运行。(2)通过对内置式永磁同步风力发电机数学模型的推导，本文提出了一种新型的通用型滑模观测模型，既适用于Ld=Lq的情况，又适用于Ld≠Lq的情况。并从观测系统中影响位置观测精度的因素出发，对观测器中滤波器的选择与角度补偿的原则进行较深入分析，并进行了仿真验证来证明所提算法的正确性。(3)对在正负序同步旋转坐标系下正序电流与负序电流分别采用PI控制器与在正序同步坐标系下采用比例积分谐振控制器两种抑制小值不平衡电网电压下并网电流中的负序含量的方法进行了详细的对比研究。提出一种机侧变流器电流控制策略来抑制在小值不平衡电网电压下直流侧母线电压2倍电网频率波动引起机侧变流器转矩2倍电网频率脉动。(4)提出了在电网电压发生不对称跌落故障时的逻辑控制，通过理论分析，将直流侧能量泄放回路分别与网侧变流器正负序电压分别定向正负序同步旋转坐标系正负序双电流环控制策略、正负序电压分别定向正序坐标系采用PI-RES控制器单电流环矢量控制策略以及本文提出的基于比例积分谐振控制器的空间矢量调制直接功率控制策略相结合实现了不平衡度超过50%的不对称故障穿越。。(5)本文在2MW永磁同步电机实验平台上对本文所提的对称电网电压下直驱式永磁同步风力发电机变流器网侧变流器控制策略与机侧变流器无位置传感器控制策略进行了实验验证，实验证明了控制策略的有效性。同时本文建立2kW背靠背双PWM变流器对本文所提在大值不平衡电网电压下的控制策略结合直流侧能量泄放回路进行了详细的实验研究，以实验结果来验证相关分析的正确性。更多还原

【Abstract】 With the increasement of the capacity of the direct-driven permanent magnetsynchronous generator (D-PMSG), its importance to the grid has become increasinglyevident so that it would have a direct impact on the stability and power quality of theconnected grid. Therefore, considering the security of the grid, power authorityproposed that wind turbines should have the ability to operate without disconnectfrom the grid and ride through the grid fault when external grid was fault. Currently,the existing D-PMSG control methods are limited to running under the balanced gridvoltage, while the real grid always exists voltage transients and asymmetric fault. Thevariable speed constant frequency (VDCF) operation of D-PMSG uses traditioncontrol strategies under the condition of ideal large power grid, which could not meetthe reality that wind turbines in China was usually connected to the weak power grid,neither could ensure the security operation of the wind power system from thecontrolling. In that case, a new control model must be established to adapt the realgrid and new control strategies must be discussed to ride through the grid fault. In thiscontext, a D-PMSG was chosen for the study and research on its operation and controlstrategy under unbalanced grid voltage.In this dissertation, the unified mathematical model of D-PMSG was establishedby using space vector method. Then based on the model, the paper discussed theD-PMSG control strategy under such conditions: normal grid voltage, the small valueunbalanced grid voltage, and large value unbalance grid voltage caused by the gridasymmetric fault.By taking the2MW permanent magnet synchronous generator (PMSG)(XE-82)made by the Xiangtan Electric Manufacturing Group (XEMC) as an example, thethesis analyses the simulation of the operation and control strategy of the PMSGunder unbalanced grid voltage. At the same time, the thesis analyzed the experimentresult by taking a2kW back-to-back PWM converter as an example. And it achievedthe operation and control of the D-PMSG under small and large value unbalanced gridvoltage. The simulation and experiment results have shown that the proposed controlstrategy applied to the D-PMSG were correctness and availability, which has referentvalue to realize the asymmetry fault ride-through of the PMSG. The main researchcontents and innovation results of this thesis are listed as follows:(1) Based on the PMSG mathematical model, a steady-state control strategy suitable for the system under normal voltage was proposed and validated bysimulation, which laid the foundation of further study of the D-PMSG operation whenthe grid voltage under abnormal conditions. Then, the low voltage ride through withthe grid voltage symmetrically fall to the20%of rated voltage was achieved insimulation by adding an energy discharge unit on the DC bus.(2) By deducing the mathematical model of interior permanent magnetsynchronous wind turbine, the thesis proposed a new universal sliding mode observermodel which applied to conditions of both Ld=Lq and Ld≠Lq. Then starting fromthe factors affecting the observer’s precision of position from the observation system,the principle of filter selection and angle compensation in observer was deeplyanalyzed. Moreover, a simulation was carried out to prove the correctness of theproposed algorithm.(3) Dual current control loop by using PI controller in positive and negativesynchronous rotating coordinate and single current control loop by using PI-REScontroller in positive synchronous rotating coordinate were adopt respectively indetailed comparative study on inhibiting the negative sequence current under smallvalue unbalanced grid voltage. In this dissertation, a motor-side converter currentcontrol strategy to suppress generator torque pulsating caused by dc-bus voltagefluctuations under small value unbalanced grid voltage.(4) A control strategy in the asymmetry drop fault of grid voltage was putforward. By theoretical analysis, an energy discharge unit on the DC bus was usedrespectively with dual current control loop strategy by using PI controller in positiveand negative synchronous rotating coordinate, single current control loop strategy byusing PI-RES controller in positive synchronous rotating coordinate and a SVM-DPCcontrol strategy by using PI-RES proposed by this dissertation to achieve50%unbalanced grid voltage fault ride through.(5) In this dissertation, the control strategies of grid side converter and thenon-position-sensor control of machine side converter of the D-PMSG were verifiedby the experiment on a2MW PMSM experiment platform under the symmetricvoltage condition. The experiment proves the effectiveness of the proposed controlstrategy. At the same time，combining the energy discharging device of DC side withthe control strategy under large value unbalanced grid voltage，this thesis validatedthe proposed method by detailed experiment on a established2kW back-to-backdouble PWM converter. The experimental results verified the correctness of the correlation analysis.更多还原