【作者】 肖飞；

【导师】 徐德鸿； 马伟明；

【作者基本信息】 浙江大学 ， 电力电子与电力传动， 2013， 博士

【摘要】 随着世界各国对风电产业的大力支持和研究,风力发电技术得到了迅猛发展,装机容量大大增加。由于永磁同步电机具有机械损耗小、运行效率高、维护成本低、无增速齿轮箱及可靠性高等优点,逐渐得到广泛应用。但是在直驱方案中,变流器作为风力所发电能回馈至电网的唯一通路,对其容量、可靠性、响应速度和并网特性等要求很高；变流器的设计、制造与试验也一直是直驱式永磁风力发电系统的瓶颈和难点问题,它对于整个系统的稳定、高效运行具有至关重要的意义。本文重点关注了直驱式永磁同步风力发电变流器的建模、限制功率控制、低电压穿越过程中的检测与不对称控制算法、永磁电机无速度传感器算法以及系统构建等关键问题,采用理论分析、仿真与实验验证的方法进行了相对深入与系统的研究：将全功率变流器的控制分为机侧变流器和网侧变流器两个部分进行建模与控制分析。对于机侧变流器的控制而言,为了避免在大风条件下运行时存在的电机超速运转及SVPWM过调制现象,在原有控制策略的基础上增加了限制功率及机端电压的PI调节器,设计了一种新型的机侧变流器控制策略,仿真及现场风场试验验证了算法的可靠性及有效性。对于网侧变流器的控制,建立了LCL型滤波器电压源变流器的数学模型,并设计了针对LCL型滤波的VSC控制算法,仿真及现场风场试验结果验证了算法的可行性。针对直驱风电变流器多电平化的发展需求,为了改善不平衡负载条件下三电平中点钳位型(NPC)电压型并网逆变器的输出电压波形,基于延时信号消除(DSC)算法对电压正负序分量进行分离,分别在正向负向旋转坐标系下进行控制。但是该方法在修正了电压波形的同时,将进一步增加输出电流的不对称性,这将加剧在空间矢量调制下三电平NPC电压型逆变器中点电位的波动。基于此分析了负序电流分量对中点电位波动的影响,找出了一个开关周期内控制冗余小矢量的作用时间对中点电位调整能力的边界,从而建立了中点电位控制的空间矢量调制算法。仿真结果表明该控制方案下,负序电压分量在负方向旋转的坐标系下得到控制,同时负序电流作用使得中点电位的波动加剧,但是在空间矢量中点电位调制下,中点电压波动得到抑制。为了实现永磁直驱式风电机组的低压穿越(LVRT)能力,查明了其关键技术在于：三相电网信息的快速准确提取、电压跌落期间的能量管理和网侧变流器在电网不对称条件下的运行与控制。为了实现对电网信息的快速准确提取,设计了基于级联DSC算法的软件锁相环技术；能量管理的主要措施是在直流侧安装制动单元,将LVTR期间无法送入电网的多余能量消耗掉；针对电网不对称电压跌落下的情况,设计了基于正负序双电流内环控制的控制策略、变流器保护策略以及无功补偿策略,通过风场现场实验验证LVRT技术的可行性和有效性。为了提高风电变流器的设计研发效率与匹配性,模拟实际风场的现场运行情况,搭建了兆瓦级直驱式风力发电模拟实验系统。首先建立了两套绕组间具有300相差的六相永磁同步电机的数学模型,同时鉴于系统的实际需要,提出了一种基于高阶非奇异终端滑模观测器的无传感器控制方法,仿真与实验结果表明算法的有效性。另外,采用脉动高频电压信号注入法,实现了六相永磁同步电机无传感器控制技术的零速启动,仿真结果验证了算法的有效性。设计了一套2MW级直驱式永磁风力发电全功率变流器系统。对该变流器系统的基本组成,参数选取,控制与保护功能的实现,以及现场测试与运行的情况进行了介绍与小结。更多还原

【Abstract】 Nowadays, more and more countries support and develop their own wind power industry with great efforts, so there have been rapid advances in wind power technology, causing a considerable increase in the capacity of wind turbine installation. As the permanent magnet synchronous motor (PMSM) has such advantages as small mechanical loss, high efficiency, low maintenance cost and speedup-free gearbox, which match the special features of wind turbines well, it has become another important type of machine and gradually come into use subsequent to the application of a double fed induction wind turbine. However, the converter, according to the scheme of a directly driven wind turbine, is the only access to the power grid. Therefore, the converter must reach the high standard of performance and meet the requirements of its capacity, reliability, response speed and grid-connection. As far as the direct-drive wind power system is concerned, it is necessary to get over bottlenecks or difficult problems in the design, manufacture and test of the full-rate converter, which is of extreme importance to the stability of the entire system.This paper has made a deep research into the several key techniques related to the converter in the direct-drive wind generation system by use of theoretical analysis, simulation and experimental verification. The specific researches are described as following:To facilitate the analysis of modeling and control, the full power converter is divided into two parts:machine-side and grid-side converter. Firstly, for the machine-side converter, a novel control method has been proposed to avoid the phenomena of the motor driving over the speed limit and of SVPWM over-modulation that appear under strong-wind conditions. The method includes using two PI controllers to limit the power and voltage based on the original control strategy. Furthermore, the reliability and effectiveness of the algorithm has been tested in the wind field and simulation results. Secondly, for the grid-side converter, the analysis of performance of the LCL-style filter has led to the establishment of the mathematical model of VSC with LCL-style filter. The results of the experiments made in the wind field and simulation results show that the control technology is reliable and effective.With the further development of offshore wind power and a continuous increase both in the unit capacity of wind turbines and in the voltage of full-rate converters, there will certainly be a trend towards multi-level converters. In order to improve the waveform of output voltage of three-level neutral point clamped (NPC) voltage source converter (VSC) with unbalanced load, a delay signal cancelling (DSC) method has been used to distinguish and control the positive and negative sequence components. However, when the voltage waveform is modified, the imbalance of the current will be further raised. As a result, the neutral-point voltage will be oscillated seriously under the SVPWM. This paper deals with the impact of the negative sequence current on the neutral-point voltage oscillation, obtains the boundary condition in which to alter the unbalance by controlling small vectors of the redundant voltage, and presents the neutral-point control SVPWM method. Simulations demonstrate that the negative sequence voltage can be controlled while the negative sequence current intensifies the oscillation of the neutral-point voltage. But the oscillation can be suppressed by use of the integrated control strategy.To achieve the low-voltage fault ride-through (LVRT) capability for the permanent magnet direct-drive wind turbine, there is a great need for breakthroughs in three key techniques:the rapid and accurate extraction of three-phase power grid information, the energy management at the time of voltage drop, and the operation and control of grid-side converter under the asymmetric condition of power grid. To obtain the power grid information quickly and accurately, a DSC algorithm based on the software phase-locked loop (SPLL) technology is employed in this paper. To improve energy management, what needs to be done is to install a brake resistor in the DC-bus so as to consume the extra energy which cannot be transmitted to the power grid during the period of LVRT. To achieve the better performance under the condition of asymmetrical voltage drop of the power grid, this paper has worked out the double current loops method based on negative-sequence control strategy, the converter protection policy and the reactive power compensation strategy. The results of the experiments conducted in the wind field verify the feasibility and effectiveness of the LVRT technology.To improve the efficiency and matching of the designed wind power converter and simulate the real operation of the wind field, a M W-level wind power experimental platform needs to be built. First of all, there is need for establishing a mathematical model of the double three-phase PMSM with two sets of Y-connected three-phase symmetrical windings displaced in turn by30°. To obtain better control performance, a sensor-less control method based on non-singular high-order terminal sliding-mode observer is presented in the paper. The simulation and experiment results show that the system has good dynamic and static performances. Moreover, to solve the starting problem under the zero speed conditions, the fluctuating high frequency voltage signal injection method is employed for sensor-less control of dual three-phase PMSM, the simulation results show that the control technology is reliable and effective.A2MW-level directly-drive permanent magnet wind power converter system is designed successfully, and the basic compositions of the converter system are introduced, such as parameter selection, realization of control and protection, field testing and operation.更多还原