Observability Analysis for a Single-Phase Inverter Using Linear State-Space Equations

With increasing interest in renewable energy sources, there is a growing number of inverter-based devices that are being interconnected into the grid. This creates a challenge in terms of estimating the states of these devices. This paper presents the analysis of an observer for a single-phase inverter using the average model. The objective is to estimate the states (capacitor voltage and inductor current) of a 170 V inverter rated at 1 kVA and with a total harmonic distortion (THD) of less than 5 %. The proposed method uses the linear state-space equations of the inverter to determine if the system is observable. The type of transient response of the system will be determined using the open-loop transfer function. In order to find the values of the observer gain L, which makes the system stable, the Routh Hurwitz stability criterion is used. MATLAB/Simulink is used to simulate the state-space based single-phase inverter model. Simulation results that demonstrate the estimation of the single-phase inverter voltage and current are presented.