Improving Stability in Shipboard DC Power Systems with Constant Power Loads

Over the last two decades, the US Navy has invested significantly in developing Integrated Power Systems (IPS) on warships. IPSs present unique challenges to electrical distribution system designers. The inclusion of megawatt energy weapon systems, high-powered radars and increased computation capacity coupled with the planned use of a medium voltage DC (MVDC) architecture result in ever-greater utilization of power electronics within a shipboard electrical distribution system. The power converters used to provide tailored voltage and frequency to each load exhibit constant-power load profiles to the MVDC bus. Constant-power loads destabilize the MVDC bus by introducing nonlinear negative impedance. Large pulsed loads, such as laser weapon systems and electromagnetic railguns, prevent the use of classical linear controls. Energy storage devices (ESDs), such as batteries or flywheels, coupled to bidirectional DC-DC converters, may be used as controlled sources in addition to generator voltages. This paper introduces a multi-input adaptive Linear Quadratic Regulator based control scheme using generator voltage and energy storage device current as control inputs to produce superior MVDC bus voltage regulation in a CPL dominated system while reducing the need for bulk stabilizing capacitance.