Global accurate estimation of positive‐ and negative‐sequence voltage components for variable frequency AC systems

Abstract

In this study, a global observer-based method is proposed for variable frequency AC systems of more electric aircraft (MEA) to estimate positive- and negative-sequence components and their parameters. Looking at the measurable grid voltage as a parameterised system containing the unknown coefficient - voltage frequency, a mathematical model based on three-phase grid voltage is established. According to the obtained dynamic model, a global observer is developed to achieve the estimation of positive- and negative-sequence voltage components and their frequency, amplitudes and phase angles with zero steady-state error. Different from most existing methods which are developed for constant frequency AC grids and only have local convergence, a Lyapunov-based argument proof provided in this study shows that the proposed observer is able to achieve global asymptotic convergence in theoretical sound. Also, it ensures that the addressed global observer method has a better stability and faster dynamic performance for variable frequency AC grids of MEA. Both simulations and experimental results are provided to validate the proposed global observer scheme.