Marine Power Distribution System with Reverse Blocking Diodes
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Solution Overview
Problem
Marine power distribution systems face challenges in maintaining power availability and compliance with dynamic positioning (DP) requirements, particularly in scenarios where a total power loss occurs on one of the ac busbar sections, as existing systems may experience interruptions and fail to ensure continuous operation of critical propulsion motors and thrusters.
Innovation Solution
The implementation of a power distribution system with reverse blocking means, such as diodes or other power semiconductor devices, in the dc interfaces between active rectifier/inverters, which allows automatic disconnection from a non-functional ac busbar section, preventing fault propagation and ensuring continuous power supply to the electric motor through the other busbar section, along with a monitoring circuit for failure detection and a common mode inductor filter to limit circulating currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a marine vessel uses a single ac busbar section to power a bow thruster, then the system is simpler, but power supply is interrupted when that busbar section experiences total power loss
Solution Approach 1:
The system divides the power supply into two independent ac busbar sections (first and second sections) that can operate independently. The bow thruster is connected to both sections through separate active rectifier/inverter units, allowing the thruster to receive power from either section, thus ensuring continuous operation even if one section fails.
Solution Approach 2:
The patent implements different functional characteristics in different parts of the system. The first and second active rectifier/inverter units have reverse blocking means that allow them to block reverse power flow, enabling selective power path activation. This local functional differentiation allows automatic fault isolation and continuous power supply from the healthy busbar section.
2Reliability
If reverse blocking means are added to prevent fault propagation, then system reliability improves, but device complexity increases
Solution Approach 1:
The patent introduces reverse blocking means (such as reverse blocking valves or circuit breakers) as intermediary devices in the dc interfaces between the active rectifier/inverter units and the common dc busbar. These intermediaries automatically block reverse power flow when a fault is detected, preventing fault propagation while maintaining normal bidirectional power flow during healthy operation.
Solution Approach 2:
The reverse blocking means are designed to automatically detect and respond to fault conditions without external intervention. When a total power loss or fault occurs on one ac busbar section, the reverse blocking means automatically activate to block the faulty path, enabling the system to self-isolate the fault and continue operation from the healthy section.
3Reliability
If the system automatically switches power paths during faults, then power availability is maintained, but control system complexity increases
Solution Approach 1:
The control system automatically detects faults on either ac busbar section and autonomously switches the power path by activating the reverse blocking means on the faulty side. This self-service capability allows the system to maintain power availability to the bow thruster without requiring complex manual intervention or sophisticated control algorithms, as the reverse blocking means inherently provide the switching function.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution ensures uninterrupted power supply to electric motors during faults, maintaining operational compliance with DP standards by automatically isolating the motor from a faulty busbar section and redirecting power from the healthy section, thus ensuring continuous operation of propulsion motors and thrusters.
Implementation Method 1
Each active rectifier/inverter will typically have a conventional topology... The implementation of a power distribution system with reverse blocking means, such as diodes or other power semiconductor devices, in the dc interfaces between active rectifier/inverters
Implementation Method 2
along with a monitoring circuit for failure detection and a common mode inductor filter to limit circulating currents
Implementation Method 3
In normal operation, the ac supply-side active rectifier/inverter will operate as an active rectifier to supply power to the dc link
Implementation Method 4
the motor-side active rectifier/inverter will operate as an inverter to supply power to the electric motor
Implementation Method 5
a first ac busbar section electrically connected to a first active rectifier/inverter... a second ac busbar section electrically connected to a second active rectifier/inverter... a first dc interface assembly electrically connected to the first active rectifier/inverter and to a dc busbar... a second dc interface assembly electrically connected to the second active rectifier/inverter and to the dc busbar
Data Source
Figure 1
Figure 2
AI summary
A power distribution system (e.g., a marine power distribution and propulsion system) is described. The system includes first and second ac busbars (2a, 2b) connected to ac generators (G1, G2). A first active rectifier/inverter (12a) has ac input terminals electrically connected to the first ac busbar (2a). A second active rectifier/inverter (12b) has ac input terminals electrically connected to the second ac busbar (2b). A first dc interface (22a) is electrically connected to dc output terminals of the first active rectifier/inverter (12a) and a second dc interface (22b) is electrically connected to dc output terminals of the second active rectifier/inverter (12b). The first and second dc interfaces (22a, 22b) include reverse blocking means, e.g., diodes (30a, 30b) or other suitable power semiconductor devices that provide a reverse blocking action. A third active rectifier/inverter (38) operates as a drive and has dc input terminals electrically connected in the parallel to dc output terminals of the first and second dc interfaces (22a, 22b) by means of an interposing dc busbar (34). An electric motor, that can optionally form part of a marine thruster T1, is electrically connected to ac output terminals of the third active rectifier/inverter (38).