变工作点下的逆变器并网系统建模与稳定性分析

Impedance Modeling and Stability Analysis for Grid-connected Inverter Containing Operating Point Variables

并网逆变器作为电能变换接口装置广泛应用于新能源并网系统中。在光伏和风电新能源并网系统中,其出力受到风速与光照强度等因素的影响,进而并网逆变器的工作点也会发生变化,而其系统在不同的工作点下会呈现出不同的稳定特征。针对该问题,以逆变器并网系统为研究对象,首先分析了其系统中工作点变量之间的关系,建立了考虑工作点变量的并网逆变器阻抗模型。在含工作点变量的逆变器阻抗模型的基础上,提出了一种新的稳定性分析方法,该方法可以得到逆变器并网系统在不同工作点下的稳定裕度,分析出系统的稳定性。仿真和实验结果验证了文中所建模型与分析方法的准确性和有效性。

The three-phase grid-connected inverter,as important interface,is widely used in the renewable energy-grid systems.Its output power in the renewable energy systems,such as in the PV or wind energy systems,is easily affected by the strengths of the wind or solar radiation.Then its operating points are changed along with the output power.Moreover,its system stability under various operating points appears different characteristics.As for this phenomenon,this paper analyzes the relationships between the operating point variables,based on the inverter-grid system.An impedance model is built considering the operating point variables.On the basis of this model,a new analysis method is proposed to analyze the inverter-grid system stabilities under different operating points.This method obtains the phase margin of the system under different operating points and then acquires the system stability.Simulation and experiment are conducted to demonstrate the effectiveness of the impedance model and the analysis method.