Optimal Placement of Constant Power Loads at Different Buses of a DC Microgrid Ensuring Maximum Stability Margins

Abstract

When a constant power load (CPL) is fed from a dc bus through an LC network, oscillations are observed in the input voltage of the CPL owing to its negative resistance property. These oscillations, if uncontrolled, amplify in magnitude leading to system instability. The behavior of multiple such CPLs connected to a dc microgrid is studied in this article. It has been found that CPLs experience a higher stability margin at the buses with renewable energy sources rather than at the buses with energy storages. This phenomenon is justified by deriving the equivalent resistance seen by the CPLs at the respective buses. In addition, for a large dc microgrid system with multiple buses, the particle swarm optimization algorithm is utilized to predict the best buses in the dc microgrid to connect the CPLs. This has been achieved by formulating an eigenvalue-based objective function. Experimental results obtained from a 4-bus 400-W dc microgrid prototype validate the efficacy of the proposed optimization.