Novel Control Strategy for CESS Integrated DC Microgrid with On Grid and Off Grid Application

Due to increasing role of DC generation, such as solar photovoltaic, fuel cells, numerous DC loads, addition of different energy storage systems, such as batteries and supercapacitors, DC microgrid is gaining more importance. Distributed generators, electronically controlled loads and composite energy storage systems make the system complex to control the DC bus voltage as constant. A Novel control strategy for CESS integrated DC Microgrid with On grid and Off Grid Applications is proposed for various modes of operation decided by existing conditions. First, utility grid mode is investigated for normal operation and grid side open circuit fault with supercapacitor and without supercapacitor. DC bus voltage, power flow control, real and reactive power control of three-phase nonlinear load is carried out by grid interface converter. Second, PV mode, when grid as well as battery are not able to control DC bus voltage, PV connected boost converter operation has to shift from MPPT to constant voltage control mode in coordination of supercapacitor. In combined control of PV and supercapacitor, later is mitigating the DC bus voltage ripple and stability problem due to constant power load. Third, energy storage mode, battery and super capacitor control the DC bus voltage by combined control strategy. Battery handles the energy density component, whereas supercapacitor power density. The Proposed scheme is simulated in MATLAB/SIMULINK environment for steady state and various transient/disturbance conditions and the corresponding operation, control and stability aspects are analyzed. The simulation results are verified with the help of Hardware-In-Loop (HIL) OPAL-RT (RT-4210) simulator.