Reduced order multi-rate LQR controllers for a MVDC shipboard electric distribution system with constant power loads

Abstract

US Navy investment in future warships is focused on DC integrated power systems (IPS). A naval DC IPS will include multiple power generation devices, energy storage devices, and layered power converters. Power converters coupled to high-bandwidth regulators exhibit constant power load (CPL) behavior. CPLs exhibit negative non-linear impedance which reduce stability margins and limit the efficacy of linear control methods. Incorporating megawatt level pulsed loads, such as laser weapons or railguns, challenges the limits of linear control methods. A recently introduced control scheme, Adaptive Select-Matrix LQR (LQR-SM), is a flexible and adaptable centralized control approach to multi-input, multi-rate, high order systems. This paper presents a comparative study of LQR-SM controller performance in a naval medium-voltage DC shipboard electric distribution system with CPLs. The four configurations studied are a full-order adaptive LQR-SM controller, two adaptive reduced-order controllers, and a non-adaptive full order controller. The controllers are compared on the basis of quality of regulation, size of region of attraction (ROA), computation load, and stored-energy efficiency.