基于改进图像法的变压器严格无源暂态模型建立方法

Research of establishment transformer strictly passive transient model based on the modified image method

电力系统电磁暂态仿真中,一个稳定的电力变压器的仿真模型的建立是至关重要的。"图像法"直接根据测量或计算所得参数的幅值频变曲线特性,采用参数值为正值的电阻、电感、电容等元件进行电路综合,从而实现了电路模型的严格无源性。但该方法只是针对阻抗幅值频变曲线的单个谐振峰值点进行计算,对于更为复杂的具有多个谐振峰值点的变压器频变曲线并不适用。针对该问题,对"图像法"进行了相应的改进,即首先对具有多个谐振峰值点的变压器频变曲线利用Levenberg-Marquardt结合通用全局优化法进行多步迭代计算,然后利用非线性最小二乘曲线拟合函数Lsqcurvefit对所得元件参数值进行整体优化,使拟合效果达到最佳,在保证所实现电路严格无源的同时,又具有了广泛的通用性。最后对实验室一台实际的10 k V单相变压器进行了研究,仿真结果与实验结果对比表明了建模方法的有效性和准确性。

In the power system electromagnetic transient simulation,the establishment of a stable power transformer simulation model can be crucial.＂Image method＂ is based on the amplitude of frequency-dependent parameters and the RLC circuit elements are used to the integration of the circuit.This method can make all of the parameters of components positive and realize the strict passivity of the circuit model.However,it only calculates for single resonance peak point of impedance amplitude frequency and cannot be applied to calculate for the complex transformer frequency dependent which has several resonance peak points.In order to solve this problem,＂image method＂ has been improved in this paper.The first step of the method is making multiple iterative computations for the transformer frequency dependent on using the method of Levenberg-Marquardt and global optimization algorithms ; then the imitative effect can reach the most optimal performance after the total elements＇ parameters have been optimized by the nonlinear least square curve fitting method （lsqcurvefit）.The modified method can realize the strict passivity of circuits as well as it can be widely used.The improved ＂image method＂ has been adopted in this paper and a 10 kV single-phase transformer model is established,and the simulation results confirm the validity of the proposed method.