Impact of Negative Solar Resistance on DC Microgrid Stability: Virtual Damping Voltage and Current Solar Droop Emulated Controller

Abstract

The negative solar resistance, is highly dependent on the solar operating point. The system will become sluggish and unstable during low irradiance. It is reported that the impact of negative solar resistance is nullified by parallel impedance emulated condition (PIEC). During low irradiance, the system stability has been moved to an unstable position which is not fully resolved by PIEC. In this paper, a virtual inertia-damping voltage and current solar droop emulated controller is proposed to improve the voltage oscillation profile, inertia problem and damping of the DC microgrid system. In DC microgrids, the inherent inertia from DC capacitors is low, thus affecting the bus voltage oscillation during a reduction of irradiance. The oscillation of the system has been increased due to the equivalent impedance by negative solar resistance at lower irradiance. Oscillation’s issue and voltage instability of the PV system have been enhanced by the inner current controller. In addition, the steady-state error of the PV voltage is minimized by the virtual inertia-damping voltage restoration droop controller with PIEC. Performance analysis and dynamic characteristics are discussed through a pole-zero plot for the various conditions of negative solar resistance using virtual inertia-damping voltage and current Solar Droop Emulated Controller. This paper focuses on stability analysis to strengthen the DC microgrid. The performance of the solar controller with bidirectional converter (BDC) controller has been discussed to verify the power management between the system to manage the power for the unbalanced load.