General-Purpose Computation Method of a Power Converter for Frequency Characteristics: Application to Stability Analysis of a Grid Inverter

A grid-connected inverter is becoming more important for photovoltaic power generation and smart grid systems, and it must be designed for stable operation. For stability analysis of a system based on the impedance method, its frequency characteristics are needed to assure its stability. This paper proposes a new simple and accurate frequency analysis method for a grid-connected inverter system with a digital controller and a new frequency analysis method that considers parameter tolerances. It is a type of tolerance analysis based on the Monte Carlo method. The frequency characteristics are computed numerically and efficiently using the modified nodal analysis and they are validated by simulations and experiments. The proposed computation method is general for any linear time-invariant averaged grid-connected system.