DC and dc/ac hybrid distribution and energy storage for shipboard power systems (SPSs) are becoming a major trend due to efficiency improvement, space saving, and maneuverability enhancement. This paper has taken a real hybrid-electric-ferry as a case-study to integrate battery units (BUs) to a dc bus for supplying the propulsion motors. Furthermore, two diesel generators (DGs) are connected to the ac bus to supply the hotel loads, and a bidirectional dc/ac converter with an LCL filter is responsible for the power flow between ac and dc buses. This power topology is flexible for this ferry operation in pure electrics, extended range, and shore power modes. The DC bus voltage is stabilized and its voltage ripple is limited by BUs' interleaved three-phase bidirectional dc/dc converter with its controller considering the operation states of propulsion motors. A coordinated power flow control between DGs and BUs is presented that the system frequency is fixed for the optimal operational efficiency of the diesel engines and a Q - V droop control plus a virtual impedance loop is used to make different ac bus voltages. Synchronization with shore power and the dc/ac converter is facilitated by P - f droop control. Simulation results are presented to validate the proposed control approach in different missions.

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.

The integration of dc power distributed systems in modern shipboard microgrids is receiving much attention recently due to their high efficiency and grid connection flexibility. These dc shipboard microgrids (dc-SMGs) are characterized by having different operating modes and large proportion of electric propulsion, some of which involves severe dynamic/transient conditions. Considering various operation modes of actual ships, this paper proposes a hierarchical coordinated control, which includes primary control level (PCL) and power management system (PMS) for the coordinated operation of the power sources in dc-SMGs. The coordination between the PCL and the PMS provides the following features: First, the PCL includes primary speed regulation (PSR) of diesel generator (DG) and primary voltage control (PVC) of dc bus. The PVC can realize the dynamic/steady load power sharing by adding the virtual impedance loop, and the PSR of DG performs the rotation speed to follow the reference. Second, the PMS includes optimal speed reference setting and secondary voltage recovery control that can realize variable-speed operation of DG according to its optimal energy efficiency characteristic and improve the power quality. The simulation results are carried out under MATLAB/Simulink to verify the effectiveness and robustness of the proposed control.

This paper obtained the average integrated heat transfer coefficient for the thermal resistance of a classic of integrated LED light source and its cooling fin-root on the basis of thermal circuit method. Simulation analysis on its steady-state temperature field distribution using COMSOL Multi-physics finite element method was carried out. This method has high precision and intuitive simulation results. The iteration method of the Numerical Analysis is introduced into method for the first time. The results have significant promotion on the LED cast light structure optimization and the affection of reduced heat coupling on the light temperature distribution. The comparison between thermocouple experimental data and calculation results proved the correctness and validity of the proposed method. This experimental study plays a guiding role to thermal analysis and design of other integrated lights