弱电网下LCL型并网逆变器控制策略研究

发布时间：2018-05-05 00:12

本文选题：弱电网 + 有源阻尼　；参考：《湘潭大学》2017年硕士论文

【摘要】：为了应对能源紧缺和环境问题,基于以风能和太阳能为代表的可再生能源的分布式发电系统迅速崛起,其中作为核心组件的并网逆变器应用广泛。考虑到处于偏远地区的分布式发电系统,较长的电能传输线路以及存在的大量变压环节给电网引入一个不可忽略的等效电网阻抗,致使电网具有弱电网特性。因此,对于与弱电网连接的并网逆变器系统,电网阻抗会对其稳定性及动态性能等造成一定影响。为此,本文针对弱电网下的并网逆变器,从电网阻抗检测技术、优化控制方法等方面提出改善并网逆变器性能的具体措施和控制策略,确保其在弱电网下可靠稳定运行。本文主要研究弱电网对并网逆变器性能的影响并提出优化策略。首先,对理想电网情况下的三相LCL型并网逆变器进行建模与分析,并给出电流控制器及无源阻尼谐振抑制等的参数设计方法。接着,构建弱电网模型,分析电网阻抗对并网逆变器系统的具体影响,包括电网阻抗对LCL滤波器谐振特性、系统动态性能和稳定性等的影响。然后,论文进一步分析相对于无源阻尼抑制谐振更有优势的有源阻尼控制方法,并将并网电流有源阻尼方法应用到弱电网下的并网逆变器系统中,用于抑制系统谐振。最后,针对弱电网具有电网阻抗变化的特性,提出一种即时触发型阻抗测量方法在线检测电网阻抗,结合该阻抗在线检测技术,行成基于并网电流有源阻尼的并网逆变器的自适应控制策略,实时修正电流控制器与有源阻尼控制器的控制参数,使得并网逆变器系统在电网阻抗大范围变化下稳定运行。本文采用MATLAB软件中SIMULINK工具箱对系统进行仿真分析,论证了理论的正确性。为了进一步验证所提理论的有效性,通过设计硬件电路及编写系统控制程序,搭建一台以TMS320F2812为控制芯片的三相LCL型并网逆变器实物平台,接着在平台上完成电网阻抗对并网逆变器性能的影响实验,并验证论文中所提自适应控制策略的正确性和有效性。
[Abstract]:In order to deal with the energy shortage and environmental problems, distributed power generation systems based on renewable energy, such as wind and solar energy, are emerging rapidly, among which grid-connected inverters, as core components, are widely used. Considering the distributed generation system in remote area, the long power transmission line and a large number of transformer links introduce a non-negligible equivalent network impedance to the power network, which leads to the weak network characteristics. Therefore, for grid-connected inverters connected with weak grids, grid impedance will affect its stability and dynamic performance. Therefore, aiming at the grid-connected inverter under the weak electric network, this paper puts forward the concrete measures and control strategies to improve the performance of grid-connected inverter from the aspects of impedance detection technology and optimization control method, so as to ensure its reliable and stable operation under the weak grid. In this paper, the influence of weak grid on the performance of grid-connected inverter is studied and the optimization strategy is proposed. Firstly, the modeling and analysis of three-phase LCL grid-connected inverter under ideal grid condition are carried out, and the parameter design methods of current controller and passive damping resonance suppression are given. Then, a weak grid model is constructed to analyze the influence of grid impedance on grid-connected inverter system, including the influence of grid impedance on resonant characteristics of LCL filter, dynamic performance and stability of the system. Then, the paper further analyzes the active damping control method which has more advantages than the passive damping suppression resonance, and applies the grid-connected current active damping method to the grid-connected inverter system under the weak electric grid, which is used to suppress the system resonance. Finally, in view of the characteristic that the weak electric network has the characteristic of the network impedance change, a kind of real-time trigger type impedance measurement method is put forward to measure the power network impedance on line, combined with the impedance on-line detection technology. The adaptive control strategy of grid-connected inverter based on active damping of grid-connected current is established, and the control parameters of current controller and active damping controller are corrected in real time, so that the grid-connected inverter system can run stably under the condition of wide variation of grid impedance. This paper uses the SIMULINK toolbox of MATLAB software to simulate and analyze the system, and proves the correctness of the theory. In order to further verify the validity of the proposed theory, a physical platform of three-phase LCL grid-connected inverter with TMS320F2812 as the control chip is built by designing the hardware circuit and writing the system control program. Then the influence of grid impedance on the performance of grid-connected inverter is completed on the platform, and the correctness and effectiveness of the adaptive control strategy proposed in this paper are verified.
【学位授予单位】：湘潭大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM464

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