Operation Control for Improving Energy Efficiency of Shipboard Microgrid Including Bow Thrusters and Hybrid Energy Storages

Abstract

The frequent start/stop operation of a bow thruster presents a high pulsating power demand in shipboard microgrids while reducing the fuel efficiency of the diesel engines, which may induce potential instabilities. In this paper, a hybrid energy storage system, including batteries and ultra-capacitors, is connected to the DC bus of the thruster driver, and a hierarchical controller is proposed for the bidirectional DC/DC converters that interface storages thus providing the following functions: (1) the diesel-generator sets provide the required average power to the bow thruster; (2) the batteries smooth the active power fluctuations; and (3) the ultra-capacitors provide the pulsating active power due to the slow charging response of batteries. A V-I droop control and high/low-pass filters are used inside the primary controller to proper power sharing between storages in different time-scales. The secondary controller is developed to ensure the power from the diesel-generator sets to the bow thruster being equal to the required average power. Simulation results shows this control scheme can effectively reduce the capacity of diesel generator sets and batteries, and can improve the fuel consumption efficiency. When the thruster machine operates as a generator during fast breaking, the hybrid energy storage can absorb the braking energy.

A Review of DC Shipboard Microgrids—Part II: Control Architectures, Stability Analysis, and Protection Schemes

“…The primary level control consists of the inner current and voltage control loops and the virtual output-impedance loop, which is designed according to the characteristics of the power source, aiming at sharing the load. One basic principle of power sharing is the rated capacity of power sources, while with the increasing demand for fast load response and the integration of hybrid ESS (HESS), power sharing according to the sources' characteristics become popular [29], [30]. The secondary level control focuses on the DC bus voltage restoration with or without communicating with neighbor converters.…”

Dynamic Modeling, Stability Analysis, and Power Management of Shipboard DC Hybrid Power Systems

“…[11] proposes a nonlinear droop curve to secure the bus voltage regulation in the low load range and to have better current sharing accuracy in the heavy load range. [12] proposes V-I based droop control for diesel generators for the conventional AC power system and a hierarchical controller for the bidirectional DC-DC converters that interface energy storages installed inside the propulsion drive. In [12], a power control loop is added in the DC-DC converter control in order to compensate for the DG power fluctuations.…”

“…[12] proposes V-I based droop control for diesel generators for the conventional AC power system and a hierarchical controller for the bidirectional DC-DC converters that interface energy storages installed inside the propulsion drive. In [12], a power control loop is added in the DC-DC converter control in order to compensate for the DG power fluctuations. In spite of the simple implementation, the droop control may be also challenging since the droop parameters and the reference voltage should be continuously updated with new power references.…”

Coordinated Control of Diesel Generators and Batteries in DC Hybrid Electric Shipboard Power System

“…The IPS allows for the electrification of the propulsion system, therefore enabling a more flexible operation [2]. Among the IPSs, the DC distribution networks attract more attention compared with the AC networks, for various benefits provided from the aspects of manipulability, flexibility, energy efficiency, and environmental impacts [3]. On the other hand, the electric propulsion motors, high power radar, and even the electromagnetic guns in naval ships introduce many challenges in the shipboard microgrid (SMG) design.…”