Power Flow Management and Control in Weak low Voltage DC Grid System

Authors:-M. Prasad, P. Anil Kumar, Dr. T. SrinivasRao

Abstract:-Renewable energy resources such as solar photovoltaic, fuel cell, wind turbine, tidal energy, and bio-mass, etc. are gaining attraction with the depletion of fossils fuels. Most of these sources depends on the atmospheric conditions and hence the generated power fluctuates through the day. In view of this, energy storage devices such as batteries, ultra capacitor etc. are required to provide power to the loads in the absence of source power. Conventionally, a photovoltaic panel and a battery are used in the isolated grid system to supply consistent power to the consumers. The integration of the other resources such as fuel cell in this system can add a potential benefit for the isolated dc-grid such as accessibility of longtime power without power interruption and without adding any pollutants in the atmosphere. In context of this advantage, a hybrid system consisting of SPV (solar photo-voltaic), Fuel cell (FC) and battery is integrated with the common dc bus to form a reliable and efficient isolated dc system. Although this makes the weak dc-grid, yet it can serve the purpose of low cost dc system especially useful for village and remote areas of the developing countries. SPV is a primary source to provide the power to the load and fuel cell is the secondary source to provide power to the load. The power electronic DC-DC converters are used to integrate the SPV, FC and Battery. The power management algorithm to control the flow of power among the SPV, FC, and battery is implemented and executed to best utilize the accessible sources in an efficient way. The Solar photovoltaic can operate in the Maximum Power Point Tracking (MPPT) mode or Desired Power Control mode (DPC) to compensate the load power demand. The extra power required during the low irradiance case is supplied by the fuel cell in power control mode. The battery will work with in the voltage control mode to stabilize the DC load voltage additionally keeps up the state of charge (SOC) limits. The modeling of connected sources and control techniques are presented in this dissertation for the SPC-FC-Battery-Load system. The simulated results of the system consisting of a photovoltaic panel of 250Watt, Fuel cell of 160 Watt and battery of 6.5 Ah, 24 V are provided during all the modes of operation.