Mitigation of DC Bus Voltage Oscillations in Cascaded Systems of DC Microgrids: A Novel Source-Side Virtual RL Damper Approach

Point of load (POL) converter are usually designed to deliver a stable output voltage which makes them ideal to power the downstream loads in cascaded DC-DC converter systems in DCMGs. By maintaining tight regulation of their output voltage, these converters dynamically adjust their input current to meet the constant power demand within their specified control bandwidth. As a result, the input of the POL converter feeding any DC/AC loads demonstrates the constant power behaviour as like a constant power load (CPLs). When these POL converters are connected to any type of distribution network via a suitable source converter, then their negative incremental impedance feature can destabilize the system in terms of severe voltage oscillations at the DC bus. This is due to its impedance interaction with that of the source converter. To mitigate the DC bus voltage oscillations caused by CPLs, this paper introduces a novel source side adaptive parallel virtual resistive-inductive (APVRL) damper using a dependent current source approach. The proposed control topology ensures accurate regulation and robust performance, even during sudden voltage supply fluctuations. Additionally, it supports plug-and-play functionality for CPLs. A theoretical analysis is conducted to evaluate the control and operational principles of the circuit implemented using the proposed technique. The study also explores the physical significance of the circuit in cascaded systems consisting of basic DC/DC converter buck converter supplying CPLs. The proposed active stabilizer is validated through simulations conducted using MATLAB®/Simulink software which demonstrates its effectiveness and reliability.