微电网逆变器交互作用分析及建模方法研究

Relative to the interconnected power system, micro-grid has Smaller system scale and capacity , flexible operation mode and the control complex. Especially when the micro-grid running independently, the voltage lost the support of the external power and so there is the coupling interaction of the frequency bandwidth, wide distribution and many components participated between the various grid-connected inverters and the micro-grid structure parameters. The appearance of this interaction is closely related to the power quality problems within the micro-grid and the stability of synchronization. And it is a system problem. If just making a study on a grid-connected inverter from the control point, we can't grasp the interaction mechanism and analyze the global synchronization stability and steady-state power quality problems of the micro-grid. By means of mathematical homotopy topology, the project proposed a modeling method of a micro-grid to expression the inverter interaction patterns.The homotopy model can maintain the relationship between structure of the original coupling.And the project proposes to establish the unified model method to describe that the interaction of the micro-grid converter is universal and comprehensive, researches the corresponding relationships among the model parameters, control parameters and network parameters and the calculation method of the model decomposition and the relevant feature values, and provides the theoretical and practical basis of the micro-grid power quality assessment and control and micro-grid synchronization stability analysis and control. Combined with the existing new energy generation and power safety test platform, we verify the feasibility of the modeling and analysis methods.

微电网相对于大电网存在系统规模和容量小、运行方式灵活、控制复杂等特点。尤其在微电网独立运行时，失去外部大电源对电压的支撑，使得各种微电网逆变器与微电网结构参数间存在频带宽、分布广、参与元件多的耦合交互作用，这种交互作用的表象与微电网内的电能质量问题及同步稳定性密切相关，且是一个系统的问题。单独从控制角度针对某一台微电网逆变器研究，无法把握交互作用的机理，也无法分析微电网全局的同步稳定性和稳态电能质量问题。项目提出借助于数学拓扑上的同伦，建立微电网逆变器交互作用的一种模型表达方法,在保持原有耦合关系结构的前提下寻求具有普适性、完备性的同伦模型，研究模型参数与控制参数和网络参数的对应关系及模型分解和相关特征值的计算方法，并为微电网的电能质量评估及微电网同步稳定性的分析提供理论和实践上的依据。依托现有新能源发电与电力安全试验平台，验证建模及分析方法的可行性。

随着微电网相关研究的开展，对微电网逆变器交互作用的机理、建模与抑制等问题逐步受到关注。本项目提出了考虑交互作用的微电网逆变器建模与稳定性分析方法，揭示了微电网逆变器交互作用的机理，为微电网多并网逆变器作用下电能质量评估与稳定性问题分析提供了理论基础。本项目的难点是：由于交互作用的影响，同样控制参数下并网逆变器中各种控制模块的特性有较大的变化，因此微电网逆变器本质上是一个复杂时变的非线性系统，其精确建模非常困难。本项目采用了诺顿等效模型、小信号建模与阻抗分析方法，并提出按照主导影响模块分析简化建模，建立了适用不同频带的单相微电网逆变器阻抗模型；采用了动态相对增益矩阵原理，建立了多逆变器微电网的多输入多输出模型。通过以上所研究建立的模型，分析了逆变器交互谐振/振荡特性与逆变器类型及数量、逆变器结构控制参数及电网参数之间的关系。基于以上分析，本项目提出了微电网逆变器交互作用分析统一模型、基于哈密顿作用量的微电网逆变器同调等值判据及参数聚合方法；并针对孤岛模式下提出了微电网多逆变器稳定性判据；本项目还从改进电流控制、增加全局抑制设备等角度，提出了抑制微电网逆变器交互作用引起的谐振/振荡问题的方法。通过仿真与实验验证了相关方法、模型与判据的可行性。