Decentralized Linear Quadratic Gaussian control of multi-generator MVDC shipboard power system with Constant Power Loads

Abstract

A major challenge in MVDC shipboard power systems is maintaining Medium Voltage DC (MVDC) system stability, due to the presence of the negative incremental resistance behavior of Constant Power Loads (CPLs). This paper presents a decentralized Linear Quadratic Gaussian (LQG) control approach for individual local generator side converter to regulate and stabilize the MVDC system. In this control approach, we model the non-linear CPL, which the decentralized controller is responsible for, as a virtual disturbance and consider it as an additional state to be estimated by Extended Local Kalman Filter (ELKF). Using the estimated virtual disturbance, the set-point trajectory in steady state can be obtained and applied in Linear Quadratic Regulator (LQR) with the optimal state feedback gain. Accordingly, linearization of the constant power load is achieved via this accurate estimation of the virtual disturbance; stability is guaranteed via an optimal LQR, as well as the load is shared among the generation units via droop control. Due to the fact that the estimation of each individual virtual disturbance is based only on the local measurements and the local fix model implemented in ELKF, the MVDC system adaptive set-point is achieved in local controllers without communication. This assumption holds true not only in the case of a sudden large load connection or disconnection, but also in case of generator loss.