考虑工作点时变特性的并网变流器全工作区间稳定性分析

Full Working Area Stability Analysis of Grid-connected Converters Considering Time-varying Characteristics of Operating Points

现有工程运行数据显示,并网变流器(grid-connected converter,GCC)的动态特性与工作点密切相关。受新能源出力波动、负载投切等外部因素的影响,变流器工作点呈现随机时变特性。因此,分析整个工作区间中所有工作点的系统稳定性具有重要意义。传统阻抗/导纳分析方法可以有效分析GCC运行于特定工作点时的稳定性,但考虑系统所有可能工作点时则需重复分析,工作量大且难度较高。为解决这一难题,提出一种考虑工作点变量的多元建模方法。将工作点变量引入导纳模型,通过控制环路重构,建立GCC的多变量单输入单输出(single input single output,SISO)模型。所提模型直接包含工作点变量,因此可以有效分析变流器全工作区间动态特性。此外,综合考虑变流器最大传输限制和动态特性,提出一种基于安全运行域的稳定性分析方法,以实现多维工作区间中系统稳定性的直观表征。仿真和实验验证了所提多变量SISO模型和基于安全运行域的分析方法的正确性。所提模型和方法在分析电力电子装置运行极限、指导变流器设计和辅助功率器件发挥极限性能等工程场景中具有广泛应用潜力。

The existing project operation data shows that the dynamic characteristics of grid-connected converters(GCC)are closely related to the operating points.Due to the influence of external factors such as new energy output fluctuation and load throwing,the operating points of the converter show random time-varying characteristics.Therefore,it is important to analyze the system stability at all operating points in the whole operating interval.Conventional impedance/conductance analysis method can effectively analyze the stability of GCCs when they operate at specific operating points,but when all possible operating points of the system are considered,the analysis needs to be repeated several times,which is a large and difficult task.To solve this challenge,a multivariate modeling approach considering the operating points variables is proposed.The operating points variables are introduced into the conductance model,and the multivariate single input single output(SISO)model of the GCC is established through the control loop reconstruction.The proposed model directly includes the operating points variables,and thus can effectively analyze the dynamic characteristics of the converter in the full operating interval.In addition,a stability analysis method based on the safe operation region is proposed to realize the intuitive characterization of the system stability in the multidimensional operating interval by considering the maximum transmission limit and dynamic characteristics of the converter.Simulations and experiments validate the correctness of the proposed multivariate SISO model and the analysis method based on the safe operation region.The proposed method has wide application potential in engineering scenarios such as analyzing the operation limits of power electronic equipment,guiding converter design and assisting power devices to play the extreme performance.