【作者】 夏正龙；

【导师】 史丽萍；

【作者基本信息】 中国矿业大学 ， 电力电子与电力传动， 2014， 博士

【摘要】 静止同步补偿器(Static Compensator-STATCOM)，可以有效解决配电网无功缺失、电压波动与闪变、电网谐波污染等电能质量问题，是一类兼顾无功补偿与谐波治理的重要电力电子变流装置，链式STATCOM相对于变压器多重化STATCOM，具有占用空间小、运行效率高、可实现冗余运行等优点，近年来得到了广泛关注和应用，对其主电路关键参数设计、装置控制策略以及样机研制实现的研究具有重要的理论与工程实践价值。本文针对LCL滤波器的链式STATCOM，对上述关键技术进行研究。针对LCL滤波器的链式STATCOM的主电路结构、数学模型进行分析，建立三相静止坐标系和两相同步旋转坐标系下装置的数学模型，由数学模型可以看出LCL滤波器的链式STATCOM是一个高阶、非线性、强耦合的多变量系统，并对装置主电路中关键器件：IGBT功率器件、H桥直流侧电容及其指令电压值、链节H桥单元数量、IGBT关断电压缓冲电容及电路类型作了详细的设计与器件选型。LCL滤波器用较小的电感值即可达到与L滤波器同样的滤波性能，不但节省了滤波器成本与体积，而且提高了系统的动态性能，但由于其三阶特性，滤波器的四个关键参数变化对滤波性能、谐振频率、纹波限制、基波电压损失都会造成影响，参数设计比较复杂。目前LCL滤波器应用研究多集中于低压场合，未见中高压，尤其是中高压链式STATCOM应用研究，本文在深入研究LCL滤波器的基本原理与特性的基础上，提出了一种适用于中高压链式STATCOM的LCL滤波器工程设计方法，按照高频开关纹波抑制与电压降、变流器侧电感与网侧电感比值、滤波电容与网侧电感的分流效果、链式STATCOM的补偿带宽与LCL滤波器的谐振频率这四个步骤依次设计与校验，该方法简单易用、物理意义清晰，具有一定的工程应用价值。采用人工鱼群智能算法对LCL滤波器的参数进行优化设计。传统的工程设计方法通常在满足性能指标的海量数据组合中选择成本最低的方案，无法保证LCL滤波器在开关频率处的最佳滤波效果。本文用MATLAB语言设计人工鱼群智能算法对LCL滤波器参数进行寻优的程序，将LCL滤波器的变流器侧电感、网侧电感以及滤波电容作为每个人工鱼的三维搜索空间，以开关频率处的谐波电流衰减函数作为寻优函数，结合装置补偿带宽等性能指标限制条件，能快速有效地求取LCL滤波器全局最优参数，具有一定的理论研究价值。提出一种基于LCL滤波器网侧电流反馈的以PI控制器、二阶低通滤波器作为电流控制内环，结合重复控制器以及对应校正环节作为电流外环的链式STATCOM电流跟踪控制策略，通过电流控制内环中二阶低通滤波器相位延迟特性以及PI控制器的设计解决LCL滤波器的阻尼稳定控制与基波无功电流的无静差跟踪控制，结合重复控制电流外环完成链式STATCOM对谐波电流的跟踪控制，兼顾了装置对补偿带宽内电流跟踪控制的稳态精度与动态性能。针对特定场合选择性谐波补偿的性能需求，提出一种基于二阶带通数字滤波器与二阶低通数字滤波器配合使用的补偿电流指令检测方法，并对相关数字滤波器的装置参数进行了详细的设计，相对传统的多同步旋转参考坐标系法，可以节省大量FPGA内存资源。建立电网电压不平衡时链式STATCOM有功功率交换的数学模型，分析得出电网负序电压以及流过三相换流链的负序电流对装置直流侧电容电压均衡控制均造成影响，针对这种情况提出一种适用于不平衡电网环境下的链式STATCOM直流侧电容电压均衡控制策略，从总体、相内、相间三个层面实现直流侧电容电压的平衡控制。电容电压总体均衡控制借助PI电压外环控制达到装置总体有功功率的平衡；电容电压相内均衡控制利用装置输出电流反馈来叠加误差信号，在每一相内各个H桥单元的调制波上叠加一个与输出电流同相位的电压分量来达到电容电压的相内均衡控制；相间均衡控制采用一种改进的基于负序电压前馈环的直流侧电容电压相间均衡控制策略，在补偿装置并网点的负序电压的同时，通过将每一相电容电压的平均值与指令电压的差值经过PI控制器输出变换为与电网电压同相位的交流量，经过同步旋转变换叠加至电流外环给定值。该方法不但提高了装置在并网点电压不平衡条件下生存能力，而且有效解决了链式STATCOM直流侧电容电压的平衡控制难题。根据本文对LCL滤波器的链式STATCOM相关理论与关键技术的研究基础上，成功开发出6KV配电网±2.8Mvar容量LCL滤波器的链式STATCOM的工业样机装置，给出了详细的样机研制过程。针对装置样机基波无功补偿、基波与谐波综合补偿效果进行了并网实验。实验结果表明，本文研制的LCL滤波器的链式STATCOM的控制策略与关键装置参数设计方法正确有效。最后将工业样机用于山东能源枣庄矿业集团某煤矿地面6KV变电所无功补偿与谐波治理，装置并网运行前后的测量数据证明，基于本文装置关键设备参数设计方法与相关控制策略的LCL滤波器的链式STATCOM实现了较为理想的动态无功补偿与谐波治理效果，达到了预期设计目标。更多还原

【Abstract】 Staic Synchronous Compensatror (STATCOM) is an important power electronicequipment for both reactive compensation and harmonic suppression, which can solvethe problems of power quality, such as lack of reactive power, voltage fluctuation andflicker, harmonic pollution of power grid and so on. Compared with the multiplextransformer structure of STATCOM, Cascaded STATCOM is widely used andconcerned for its following advantages of a small footprint, high efficiency, modulardesign and so no. The design of main circuit parameters and control strategy hasimportant practical value as well as academic value. To solve the above keytechnologies, the research in this dissertation was put forward according to cascadedSTATCOM with LCL filter.Based on the analysis of main circuit and mathematicl model of cascadedSTATCOM with LCL filter, the dissertation deduces the mathematical model in thea-b-c and d-q coordinates under the principle of coordinate transformation. From themathematical model, it can be seen that cascaded STATCOM with LCL filter is atypical high-order, nonlinear systems with multiple variables, close coupling anduncertain parameters. The device choices and detailed designs of IGBT powermodules, dc bus capacitor of H-bridge and its reference voltage, number of H-bridgechain link and snuuber circuit of suppression of IGBT turn-off voltage are given inthis dissertation.LCL filter can achieve the same filter performance with smller inductance valuescompared with L filter, which not only brings cost savings and smaller size, but alsoraises dynamic performance. For third orders nonlinear characteristic, changes inparameters of LCL filter can affect filter performance, resonant frequency, ripplecurrent suppression performance and voltage loss, which is the reason of complexparameters design. Based on the further study of basic principle and characteristics ofLCL filter, a parameters design method suitable for engineering applications isproposed with the following four design steps. The parameters design methodproposed in this dissertation is simple and the physical meaning is clear, which is alsopractical for engineering application.The artificial fish swarm algorithm (AFSA) is adopted to optimize parametersdesign of LCL filter. The traditional parameters design method picks out a plan at thelowest cost on the condition that certain performance indicators and given constraints can be sastisfied, which can not guarantee the best filtering effect. An optimizationparameters design of LCL filter by AFSA is given with Matlab language. By theAFSA, the best filtering performance parameters of LCL filter can be picked outquickly and effectively, which has certain values for theory study and applicationresearch.A grid side current feedback control method using PI controller and typicalsecond order low pass filter as inner current loop and repetitive control as outercurrent loop is proposed. The open-loop magnitude margin and close-loop stability isimproved and ensured by inner current loop. Steady-state performance of current loopis improved by the above double-loop control, ensuring both fast dynamic responseand small steady-state error for current track and compensation in the banwidth ofcascaded STATCOM. For the demands of selective harmonic compensation, a methodfor detecting the harmonic command current is proposed with the combination of2-step band pass digital filters and2nd-order digital lowpass filter which can savememory resource of FPGA. Finally the detailed design of the two above filters ispresented.The mathematicl model of active power exchange between cascaded STATCOMand the grid is developed, from which capacitive voltage balance control influence ofnegative sequence current is gained. Under this circumusance, the balance control ofcapacitive voltage at the DC side under three-phase unbalanced condition is proposedby three levels: overall balance control, phase inside balance control and phase tophase balance control. The proposed method not only enhances the reliability ofcascaded STATCOM with LCL filter, but also solves the difficult capacitive voltagebalance control problem effectively.Based on the further research of related theory and key technique of cascadedSTATCOM with LCL filter in this dissertation, the prototype device is developed withthe capacity of±2.8Mvar and the voltage class of6KV. A detail design procession isgiven. Experiments are carried out to investigate effects of reactive power andharmonic compensation. The results show that the design in this dissertation is correctand effective. Finally, the propotype device is applied in a coal mine of SHANDONGENERGY GROUP CO., LTD. The measuing data before and after compenstationproves that the cascaded STATCOM with LCL filter designed in this dissertation canrealize an ideal dynamic reactive compensation and harmonic suppression effect,which reaches the design target.更多还原