Constant power load in DC microgrid system: A passivity based control of two input integrated DC-DC converter

This article investigates the design and implementation of a passivity-based nonlinear control technique for an integrated two input DC-DC converter with constant voltage and power loads in a DC microgrid system. In constant power loads (CPL), when input voltage changes with respect to input current, the converter's performance in terms of power quality, dynamics, and stability are affected by the negative increment impedance characteristic (NII). Due to this, there is undesirable limit cycle behaviour in the system. The nonlinear passivity-based control technique (PBC) is employed to address this issue. The integrated converter system and PBC strategy are modelled using the Euler-Lagrange approach. The controller's resilience is tested under three different uncertainty conditions and robustness with different damping resistances. The PBC control approach ensures the elimination of limit cycles caused by the CPL, and ensures the stable system operation with faster recovery time of approximately 0.15 ss under uncertainty circumstances. The study further examined the PBC resilience across a range of active damping control gains (R_3d=0.095 and R_4d=0.045), and it is shown that lower damping gains give speedy recovery under the uncertainty conditions. A complete system with the proposed controller is simulated in a MATLAB environment, and validated results are presented.