Design of Suboptimal Controller for Improved Dynamic Response in DC Microgrid Linked to Multiple Constant Power Loads

Abstract

The high switching frequency electronics linked to the DC microgrid are used to keep the load power constant. These constant power loads(CPLs), due to the high bandwidth, are nonlinear by nature and may cause system instability. This work suggests a robust suboptimal controller design built on semidefinite programming (SDP) to control the CPLs connected to the DC microgrid. The objectives are to keep the bus voltage steady during transients and to alter the injecting current from the energy storage system (ESS) as efficiently as possible. A nonlinear mathematical representation of a DC microgrid is used for the suboptimal controller design procedure, and the problem is solved using the SDP method. The microgrid's performance is assessed in the framework of parameter uncertainty and measurement noises. The obtained simulation results show that the suggested technique is very effective and attains stability fast during faults and transients compared to the conventional PI control even when external disturbances are present. The efficacy of the suggested design approach is evaluated in MATLAB/SIMULINK and compared to the standard PI controller using mathematical simulations. The obtained results verify the usefulness of the suggested suboptimal controller architecture for the DC microgrid connected to the CPLs.