Variable-Voltage DC Bus Control Based on Electrical Machine Speed
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Solution Overview
Problem
Existing electrical power systems for vehicles like aircraft, marine vessels, and trains face inefficiencies with fixed-voltage DC buses, which lead to increased semiconductor switching losses and component wear due to high voltage requirements, despite the need for variable power delivery.
Innovation Solution
A variable-voltage DC bus system with a controller that adjusts voltage settings based on the operating speeds of electrical machines, ensuring a minimum voltage requirement is met while allowing for dynamic control and reducing semiconductor losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a fixed-voltage DC bus is used to meet maximum power requirements, then power delivery capability is ensured, but semiconductor switching losses and component wear increase
Solution Approach 1:
The patent implements a variable-voltage DC bus that dynamically adjusts its voltage level based on actual power demands. The controller monitors load requirements and modifies the DC bus voltage accordingly, transitioning from a static fixed-voltage system to a dynamic variable-voltage system. This resolves the contradiction by allowing the system to operate at higher voltages only when maximum power is needed, while operating at lower voltages during normal conditions, thereby reducing semiconductor switching losses without compromising power delivery capability.
Solution Approach 2:
The patent changes the voltage parameter of the DC bus from a fixed value to a variable value that can be adjusted based on operating conditions. The controller modifies the voltage level as a controllable parameter, enabling the system to adapt to different power demands. This parameter change allows the system to optimize between power delivery capability and energy losses by selecting appropriate voltage levels for different operational scenarios.
2Reliability
If a fixed-voltage DC bus is used to ensure reliable power delivery, then system simplicity is maintained, but component life decreases due to increased wear
Solution Approach 1:
The variable-voltage DC bus system dynamically adjusts voltage levels to match actual power demands, reducing unnecessary high-voltage operation that causes component stress and wear. By operating at lower voltages during normal conditions and only increasing to maximum levels when required, the system maintains reliable power delivery while significantly extending component lifespan and reducing degradation over time.
Solution Approach 2:
The patent modifies the voltage parameter from fixed to variable, enabling the system to adapt component stress levels based on operational requirements. This parameter change allows the system to minimize cumulative wear on components by avoiding continuous high-voltage operation, thereby extending component life while maintaining the ability to deliver reliable power when needed.
3Loss of energy
If a variable-voltage DC bus is implemented to reduce semiconductor losses, then energy efficiency improves, but system complexity increases
Solution Approach 1:
The patent implements a feedback control mechanism where the controller monitors the actual power demands of connected loads and adjusts the DC bus voltage accordingly. This feedback loop enables the system to automatically optimize voltage levels based on real-time conditions, reducing semiconductor switching losses without requiring complex manual intervention. The feedback mechanism simplifies the management of system complexity by enabling automatic adaptation to changing operational requirements.
Solution Approach 2:
The variable-voltage DC bus system is designed to self-regulate based on load conditions, with the controller automatically adjusting voltage levels without external intervention. The system serves itself by monitoring its own operational state and making appropriate voltage adjustments, thereby reducing energy losses while managing complexity through autonomous control rather than requiring complex external management systems.
Data Source
AI summary
Electrical power systems having variable-voltage DC busses and methods of controlling voltage settings of such busses. One electrical power system comprises: a variable-voltage DC bus; a number N≥2 of electrical machines, each electrical machine connected to the variable-voltage DC bus via one of a corresponding number N of converters, each electrical machine and corresponding converter having an index n=(1, . . . , N); and a controller configured to select a voltage setting Vdc_bus for the variable-voltage DC bus and to provide control signals to the converters to control the voltage setting of the variable-voltage DC bus according to the selected voltage setting Vdc_bus. The controller configured to select a voltage setting Vdc_bus greater than or equal to a minimum voltage requirement Vdc_min for the bus. The controller is configured to determine the minimum voltage requirement Vdc_min using present operating speeds of each of the N electrical machines.