An Observer-Based Current Sensor-Less Control Scheme for Grid-Following Converters

Distributed energy resources based on grid-following inverters are the dominant part of future modern power systems. To achieve a higher performance, the reliability enhancements and cost reductions of such inverters are the most important demands. In this respect, the sensors are one of the elements which greatly determine the cost and reliability of the inverters, and minimizing the number of sensors may achieve both lower costs and higher reliability. In addition, sensor data are prone to cyber-attacks, and sensor-less control techniques would improve the cyber-physical tolerance capabilities of the system. This paper proposes a grid-side current sensor-less control technique for grid-following inverters. In the proposed scheme, an observer is suggested which estimates the grid-side currents by processing the measured DC-link voltage. The estimated grid-side currents are fed to the control loops of the inverter. To verify the effectiveness of the proposed scheme, the stability of the overall control structure is analyzed, including the nonlinear dynamics of the DC-link voltage in the various operating points, using eigen value analysis and time domain simulations. The results demonstrate that the proposed scheme preserves the proper stability margin and performance of the GF-VSC, even in the presence of uncertainty in output filter inductance.