高渗透率分布式发电系统中LCL滤波并网逆变器关键技术研究

In distributed power generation systems with high penetration, the performance of a grid-connected inverter is seriously affected by the non-ideal factors at the point of common coupling (PCC) including the grid impedance, the voltage fluctuation and flicker, the background harmonics and unbalanced three-phase grid, the series and parallel resonances and so on. This project studies the core technology of a grid-connected inverter to achieve high performance. By establishing a systematical analysis model of the current control for grid-connected LCL-filtered inverters, this project distinguishes and evaluates the existing control methods, and then explores some novel active damping control methods. Besides, the coupling and interdependent relations between filter parameters and current control are deeply studied. Then, unlike the typical design methods of LCL filters, this project proposes a novel design method integrated with filter and controller optimizations. In addition, the action mechanisms of PCC non-ideal factors to the inverter, as well as the high performance-featured grid impedance estimation, are investigated in this project. Consequently, this project synthesizes a design approach of grid-connected inverters with good capability of adapting to the PCC conditions in distributed power generation systems. Moreover, this project establishes an analytical model to study the harmonic interferences in the grid-connected system with multi-inverter modules in parallel. On the basis of effectively solving the harmonic interference problem, the grid-connected system can work with proper decoupling control and parallel operation methods. The breakthroughs in the above technologies can build a stable foundation for the high-performance and robust grid-connected LCL-filtered inverter in distributed power generation systems with high penetration.

高渗透率分布式发电系统中，公共耦合点(PCC)处存在的电网阻抗、电压波动和闪变、谐波、三相不平衡以及串并联谐振等现象严重影响并网逆变器性能。本课题研究并网逆变器高性能运行的核心技术，包括：建立LCL滤波并网逆变器电流控制的系统化分析模型以甄别、评价现有控制方法并发掘新型有源阻尼方法；与传统的LCL滤波器参数设计方法不同，研究滤波器参数同电流控制间的耦合、制约关系以期形成一套滤波器同控制器相结合的一体化优化设计方法；研究PCC处非理想状况对并网逆变器的作用机制，结合高性能的电网阻抗测量技术以形成一套具备复杂电网状况良好适应性的高性能并网逆变器设计手段与方法；建立分析模型以研究并解决多模块并联并网系统的谐波干扰问题，结合逆变模块解耦控制方法以及并联运行策略以实现可靠的并联并网。上述技术的突破可为LCL滤波并网逆变器在高渗透分布式发电系统中高性能及鲁棒运行奠定坚实的基础。

高渗透率分布式发电系统中，公共耦合点(PCC)处存在的非理想因素（包括电网阻抗、电压谐波、电压波动、三相不平衡等）严重影响并网逆变器性能。本课题旨在解决实际应用中并网逆变器的滤波器及电流控制的选择与设计问题，实现不同电网状况下的逆变器系统的低成本、高性能、强鲁棒性，提高分布式并网发电系统运行可靠性。主要研究内容包括：LCL滤波并网逆变器的系统化分析与一体化优化设计方法研究，具备复杂电网状况自适应能力的并网逆变器控制技术研究，多模块并网逆变器并联运行的关键技术研究。.针对LCL滤波并网逆变器的控制与优化设计，本项目基于有源阻尼统一分析模型提出了系统化的并网逆变器电流控制分析方法，提出了几类新型有源阻尼，尤其提出了一种无附加额外传感器的单电流反馈有源阻尼；基于滤波器参数同电流控制间的耦合、制约关系的研究，提出了一种适用于单电流反馈控制的LCL滤波并网逆变器的控制器及滤波器参数一体化设计方法，采用单电流反馈同滤波器参数的合理配合实现优良的电流质量以及较强的鲁棒性。.针对复杂电网状况下系统鲁棒性不足的问题，本项目基于统一电流控制模型及逆变器输出阻抗模型，在明晰系统谐波失真甚至不稳定机制的基础上，提出了适用于不同电网状况的高性能、强鲁棒性的LCL滤波并网逆变器的控制方法，包括电网电压基波前馈加带相角补偿的准谐振控制的鲁棒电流控制及参数优化设计、电网电压加权前馈策略、无需电网阻抗精确测量的并网变流器自适应电网电压前馈补偿方法，解决了并网逆变器电流质量差、鲁棒性不足的问题。.考虑到多个并网逆变器模块并接于PCC处时电网阻抗同各台逆变器之间存在谐波干扰，影响整个系统的鲁棒运行，本项目建立了多模块并网逆变器并联系统谐振以及电流谐波抑制的分析模型，基于此，研究了锁相环对多模块并联系统鲁棒性的影响，深入分析了多模块逆变器并联的环流现象并提出了基于输出阻抗整形的谐振环流抑制方法。