【作者】 李鑫；

【导师】 蔡旭；

【作者基本信息】 上海交通大学 ， 电气工程， 2018， 硕士

【摘要】 随着海上风电的发展,风机容量趋向大型化,低压690V风力发电机出口电流将大幅增加,给机组的制造、运行与维护带来一系列挑战。永磁同步发电机(Permanent Magnetic Synchronous Generator,PMSG)具有无齿轮箱、易维护、变速范围广的特性,在海上风电中极具应用价值。为减小机组出口电流,采用永磁直驱中压风力发电机,研究与该发电机配套的中压风电变流器具有现实意义。本文通过对比各种中压拓扑,将研究重点选取为级联H桥型中压变流器,对包含永磁直驱发电机与级联H桥型变流器的风电系统进行选型与设计,对该变流器稳态运行以及故障状态下的控制策略与调制方法进行研究,研究内容与主要工作包括以下几点:(1)在建立PMSG风力发电系统关键环节详细数学模型的基础上,分别研究级联H桥型中压风电变流器的机侧变流器与网侧变流器,分析了理想电网条件下稳态运行时机侧与网侧变流器的常规矢量控制策略与调制方法,按照典型I型、典型II型系统参数设计方法设计控制环路中PI调节器参数,对文中的发电机与变流器进行选型与设计。(2)为提高系统性能:针对该变流器单个功率模块直流母线存在幅值很大的不定频电压波动问题,本文推导了该波动对并网电流低频谐波的影响,综合考虑谐波滤除效果及系统动态性能,提出基于变频陷波的级联H桥风电变流器直流电压波动导致的并网电流低频谐波抑制策略;针对传统级联H桥变流器采用多绕组移相变压器与电网相连增加系统体积与成本的问题,采用双边傅里叶变换研究网侧子变流器不同载波相位对变流器输出性能的影响,提出了应用于网侧变流器的一种载波移相调制方法。(3)研究故障状态下级联H桥式中压风电变流器的控制问题,为使发电机在变流器故障状态下可以容错运行并输出最优的功率,本文提出了中性点偏移与优化的变桨控制分层协调的控制策略,与常规同级旁路方式相比,该控制策略可以使风力发电机在变流器故障状态下始终输出最大功率且不会对电机造成破坏。(4)搭建了基于RT-LAB的级联H桥型变流器硬件在环实时仿真平台,对系统的软硬件进行了精确设计,其实时性与精确性均高于离线仿真,在该平台上对前文研究的控制方案进行验证。更多还原

【Abstract】 With the development of offshore wind power,the capacity of wind turbines tends to be large,and the outlet current of low-voltage 690 V wind turbines will increase drastically,bringing a series of challenges to the manufacture,operation and maintenance of the generating units.Permanent Magnetic Synchronous Generator(PMSG)has the advantages of no gear box,easy maintenance and wide speed range.It has great application value in offshore wind power generation.In order to reduce the outlet current of the unit,it is of practical significance to study the medium voltage wind power converter which is matched with the generator by using the permanent magnet direct drive medium voltage wind power generator.In this paper,by contrasting various medium voltage topologies,the research emphasis is selected as the cascaded H-bridge MV converter,and the selection and design of the wind power system including permanent magnet direct-drive generators and cascaded H-bridge converters,The converter steady state operation and fault control strategy and modulation methods are studied,the research content and main work include the following points:(1)Based on the detailed mathematical model of key aspects of PMSG wind power generation system,the machine-side converter and grid-side converter of cascaded H-bridge medium voltage wind power converter are studied respectively.The steady state operation under ideal grid condition The conventional vector control strategies and modulation methods of timing and grid-side converters are designed according to the typical type I and type II system parameter design methods,and the parameters of the PI regulator in the control loop are designed.The generator and converter in the paper are selected Type and design.(2)In order to improve the system performance,in view of the fact that the DC bus of a single power module has fluctuation voltage with large amplitude and variable frequency,in this paper,the influence of this fluctuation on the low frequency harmonics of grid-connected current is deduced.Based on the harmonic elimination effect and the dynamic performance of the system,the control strategy based on the frequency-variable notch in order to reduce the low frequency harmonics induced by fluctuation voltage of DC bus is proposed.In view of the traditional cascade H Bridge converter is connected to the grid via multi-winding phase-shifting transformer,which is complicated and cumbersome and the system volume and cost are increased.In this paper,an optimized modulation method based on carrier phase shift is proposed to improve the equivalent switching frequency on network side of the converter and with conventional multi-winding transformer instead of phase-shifting transformer.(3)In order to improve the generator fault-tolerant running capacity and output the optimal power in the fault condition of the converter,a control strategy combining the neutral point shifting with the optimized pitch control is proposed in this paper.Compared with the conventional same-level bypass method,this control strategy can make the wind turbine always output the maximum power in the state of inverter fault without damaging the motor.(4)The cascade H-bridge converter real-time hardware-in-loop simulation platform based on RT-LAB is built and the hardware and software of the system are accurately designed.The real-time performance and accuracy of the system are higher than that of offline simulation.更多还原