考虑多控制环耦合的并网逆变器非线性建模及仿真分析

随着新能源发电技术的快速发展和电力电子化设备的规模化应用，电力电子化已成为新型电力系统的重要发展趋势。并网逆变器作为新能源接入电网的重要接口，其暂态稳定性对电力系统的稳定可靠运行尤为重要。并网逆变器具有多控制环耦合与强非线性的特征，因此建立其非线性数学模型是分析其暂态稳定性的重要基础。然而，已有的研究大多是基于小信号建模或只考虑单一控制环节的简化非线性建模，不能完全表征并网逆变器在大扰动条件下的暂态响应。因此，充分考虑并网逆变器多控制环耦合特性，建立其全阶非线性暂态模型，包含功率下垂控制环、锁相环，电压电流双闭环控制。为了便于模型应用，采用奇异摄动法推导了非线性降阶模型。利用Matlab/Simulink时域仿真和RT-Lab实时仿真，验证了全阶模型和降阶模型在小扰动和大扰动下的准确性。在非线性降阶模型的基础上进行线性化，并利用小信号方法分析了系统参数对稳定性的影响。所建立的并网逆变器非线性暂态模型具有较高的模型精度和实用性，可为电力电子化电力系统的暂态稳定性分析提供数学模型基础。

Nonlinear Modeling and Simulation Analysis of Grid-connected Inverter Considering Multi-loop Coupling

With the rapid development of renewable energy power generation technologies and the large-scale application of power electronics equipment, the power-electronics-enabled power system has become an important trend for novel power systems. The transient stability of a grid-connected inverter, which is a crucial interface for renewable energy integration, is particularly important for the stable operation of power systems. Since the grid-connected converter has characteristics of multi-loop coupling and high nonlinearity, the establishment of its nonlinear mathematical model is an important basis for analyzing its transient stability. However, most of the existing studies focus on small-signal modeling or simplified nonlinear modeling with the consideration of only one single control loop, which cannot fully characterize the transient response of the grid-connected inverter under large disturbances. In this paper, considering the multi-loop coupling characteristics of the grid-connected inverter, its full-order nonlinear transient model is established, covering the power droop control loop, phase-locked loop, and voltage and current double closed-loop control. Moreover, for the easy application of this model, the singular perturbation method is adopted to derive the nonlinear reduced-order model. Matlab/Simulink time-domain simulations and RT-Lab real-time simulations are performed to verify the accuracy of the proposed full- and reduced-order models under small and large disturbances. Linearization is also performed on the basis of the nonlinear reduced-order model, and the small signal method is used to analyze the influence of system parameters on the stability. The non-linear transient model of grid-connected inverter established in this paper has a high model accuracy and a high practicability, providing a mathematical model basis for the transient stability analysis of power-electronics-enabled power systems.