An Improved Method for Grid Impedance Estimation by Digital Controlled PV Inverters Suitable for ENS Detection

In this paper an improvement to an existing method for impedance estimation based on inter-harmonic current injection is presented, suitable for ENS detection. This feature is integrated directly in the power converter and shares with this power electronics, sensors and DSP for data processing and control. Realistic simulations using Matlab/Simulink tool are made to verify the effectiveness of the proposed solution within a complete photovoltaic (PV) converter model, including panels, input DC-DC converter and controller running the maximum power point tracking algorithm, DC-AC inverter running dc-link voltage and output current control, LC output filter and accurate grid model. Measurement uncertainty, system non-idealities and specific features (e.g. pulse width modulation and power converter model) have been considered and accurately modelled.