Adaptive, sparse, and multi-rate LQR control of an MVDC shipboard power system with constant power loads

The US Navy is pursuing development of all-electric warships. The future all-electric warship is expected to utilize medium-voltage DC (MVDC) main distribution to supply several load zones. The load zones will convert the MVDC power to lower voltage for use by local loads as well as contain local energy storage for casualty back-up power. A majority, if not totality of loads are expected to exhibit constant-power load (CPL) behavior. Voltage instabilities introduced by CPLs and methods to address the problem in multi-machine MVDC systems are reviewed. This paper presents an LQR based, centralized, control scheme to regulate MVDC distribution bus voltage as well as the low-voltage DC (LVDC) service buses through coordinated use of low-bandwidth MVDC voltage sources and high-bandwidth, low-voltage currents sourced from the local energy storage devices. A sparse-feedback, multi-rate LQR controller (LQR-SM) is designed and implemented in MATLAB software using a hypothetical multi-machine, multi-zone shipboard MVDC electric distribution system with CPLs and energy storage devices. The presented control scheme is able to combine and coordinate all available control inputs to effectively regulate MVDC and LVDC buses in the system while allowing for design flexibility not available through existing control schemes.