Matlab simulation of nonlinear electrical networks via volterra series expansion and multidimensional NILT

The paper deals with a simulation of nonlinear networks based on a classical approach of Volterra series expansion. It is known that a multidimensional Laplace transform (MLT) of a time-domain nonlinear impulse response results in the respective Laplace-domain transfer function which helps in finding Volterra kernels, for example via a harmonic input method. After solving the system in the Laplace domain, a final step is to transfer the solution back into the time domain. For this purpose proper multidimensional numerical inverse Laplace transforms (MNILT) are applied with advantages avoiding the usage of rather impractical associate variables method required to receive a single-variable Laplace image. To ensure good convergence and stability of the method the networks are limited to be rather weakly nonlinear when usually the kernels into the third order already yield reasonable results. That is why, methods for up to the third-dimensional NILT (3D NILT) are discussed in the paper, both the FFT-based one with a quotient-difference algorithm and a hyperbolic one with the Euler transformation. All the discussed methods are programmed and tested in Matlab language while considering a proper model of a nonlinear electrical network.