On-Board Power Conversion for Charging From Weak Shore Networks
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Solution Overview
Problem
Current charging systems for vehicles, particularly watercraft, face inefficiencies due to weak land-side charging networks, which limit the ability to charge energy storage devices within a reasonable time, leading to the need for continuous land-side energy storage and inefficient energy conversion between alternating and direct voltage.
Innovation Solution
A partial on-board electrical system with a power converter that operates as both a DC/DC controller during charging and an AC/DC controller during independent operation, utilizing a switching device and inductance to optimize energy transfer and reduce losses, allowing for direct voltage charging and flexible operation with existing components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If shore-side charging stations use conventional AC/DC conversion to charge vehicle energy storage devices, then charging can be performed, but the weak power supply network cannot provide sufficient power to charge the vehicle energy storage unit within a reasonable time
Solution Approach 1:
The shore-side energy storage device is pre-charged from the weak power supply network during periods when the vehicle is not docked. This preliminary charging action allows the energy to be stored and then rapidly transferred to the vehicle when needed, bypassing the limitation of the weak grid during the actual vehicle charging process.
Solution Approach 2:
The shore-side energy storage device acts as an intermediary between the weak power supply network and the vehicle energy storage device. It buffers the power conversion process, allowing the weak grid to charge the shore-side storage at its limited capacity while enabling rapid charging of the vehicle from the shore-side storage without directly loading the weak grid.
2Loss of energy
If conventional charging systems continuously convert AC to DC and back to AC for charging, then charging can be performed, but energy losses occur during multiple conversion processes
Solution Approach 1:
The invention extracts the AC/DC conversion step from the charging path by using DC/DC conversion between the shore-side energy storage device and the vehicle energy storage device. This eliminates the lossy AC/DC conversion process that would otherwise be necessary, reducing energy losses during charging.
Solution Approach 2:
The system changes the voltage parameters directly in the DC domain using DC/DC conversion rather than converting through AC. This parameter transformation approach maintains energy in the DC form throughout the charging process, avoiding the energy losses associated with AC/DC conversion cycles.
3Speed
If shore-side charging stations are designed with high power converters to enable fast charging, then charging speed improves, but the weak power supply network cannot support such high power requirements
Solution Approach 1:
The shore-side energy storage device is pre-charged during off-peak periods when the vehicle is not docked, accumulating energy in advance. This allows the system to provide high-power charging to the vehicle without requiring the weak power supply network to continuously deliver high power, as the energy was stored when the vehicle was absent.
Solution Approach 2:
The shore-side energy storage device serves as a power buffer that decouples the high-power charging demand from the weak power supply network. The converter only needs to handle the limited power available from the weak grid when charging the shore-side storage, while being capable of delivering high power to the vehicle from the stored energy during docking.
4Ease of manufacture
If separate AC/DC and DC/DC converters are used for charging operations, then charging functionality is achieved, but device complexity and cost increase
Solution Approach 1:
The shore-side power converter is designed with multi-functionality to perform both AC/DC conversion when charging the shore-side energy storage device and DC/DC conversion when transferring energy to the vehicle. This universal converter design eliminates the need for separate converters, reducing system complexity and cost while maintaining full charging functionality.
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 enhances charging efficiency by eliminating lossy conversion processes, reduces the power requirements for land-side converters, and allows for cost-effective design of on-board electrical systems, ensuring reliable and efficient energy transfer regardless of the voltage level, thus improving the overall charging process.
Implementation Method 1
the power converter is configured by means of the control device to operate the energy sub-network as a direct current network during the charging process and as an alternating current network during the independent operation of the vehicle
Data Source
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AI summary
The invention concerns an on-board power subsystem (1) for a vehicle (30), wherein the on-board power subsystem (1) has at least one energy storage unit (2) and a control device (9) for charging the energy storage unit (2) of the vehicle (30). To improve the charging of the energy storage unit, it is proposed for the on-board power subsystem also to have an on-board power connection (3) for connection to electrical components (31) of the vehicle (30), a DC voltage connection (4) for connection to a land-based charging station (20) and an energy subsystem (5), wherein a switching device (6) is arranged between the on-board power connection (3) and the energy subsystem (5), wherein a charger (7) is arranged between the energy storage unit (2) and the energy subsystem (5), wherein the DC voltage connection (4) is electrically conductively connected to the energy subsystem (5), wherein the on-board power subsystem (1) has at least one power converter (8) that is connected on the AC voltage side to the energy subsystem (5) and is able to be operated both as an AC/DC converter and as a DC/DC converter, wherein the power converter (8) is configured, by way of the control device (9), to operate the energy subsystem (5) as a DC voltage grid during the charging process and to operate it as an AC voltage grid during independent operation of the vehicle (20). The invention furthermore relates to a vehicle having such an on-board power subsystem, to a land-based charging station, and to a charging system. The invention furthermore relates to a method for operating such an on-board power subsystem (1) or such a vehicle (20) or such a charging system (40), wherein the power converter (8) is operated as a DC/DC converter during a charging process and as an AC/DC converter during independent operation.