Coupled Converter Intermediate Circuits for Power Oscillation Buffering
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Solution Overview
Problem
Conventional drive systems for electric motors face challenges in efficiently managing power supply from the public grid, particularly in generator-mode operations, where power oscillations and magnetic stray fields can disrupt motor performance and require costly buffering solutions.
Innovation Solution
A drive system comprising a first converter with a small intermediate circuit and a second converter with a larger intermediate circuit, connected via inductivities and capacitances, which support each other to stabilize power supply and minimize oscillations, using foil or polar capacitors for efficient voltage buffering and reducing magnetic interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a converter has a small intermediate circuit, then the converter size and cost are reduced, but the converter cannot effectively buffer power fluctuations and support other converters during generator-mode operation
Solution Approach 1:
Multiple converters are electrically connected via inductivities to form a combined intermediate circuit system. The intermediate circuits of different converters are merged through coupling inductivities L1, allowing them to support each other during generator-mode operation while each converter maintains its own small intermediate circuit capacitance.
Solution Approach 2:
Coupling inductivities L1 are introduced as intermediary elements between the intermediate circuits of different converters. These inductivities enable power transfer and mutual support between converters while isolating the small intermediate circuit capacitances from direct interaction, thus maintaining buffering capability without requiring large capacitances in individual converters.
2Productivity
If converters are connected via inductivities, then power can be shared between converters during generator-mode operation, but oscillations and magnetic stray fields may disrupt motor performance
Solution Approach 1:
The coupling inductivities L1 are extracted as separate, externally mounted components rather than being integrated inside the converter housings. This separation allows for optimized design of the inductivities to minimize magnetic stray fields while maintaining the power sharing functionality between converters.
Solution Approach 2:
Instead of integrating all magnetic components inside converter housings, the patent inverts the approach by placing the coupling inductivities L1 outside the housings. This inversion allows better control over magnetic field distribution and reduces interference with motor operation while maintaining electrical connectivity for power sharing.
3Stability of the object's composition
If the intermediate circuit capacitance is increased to buffer power fluctuations, then power supply stability is improved, but the converter size and cost increase
Solution Approach 1:
The patent merges the intermediate circuit functions of multiple converters through electrical connection via inductivities L1. This allows the combined system to provide adequate power buffering and voltage stability support during generator-mode operation, eliminating the need for each individual converter to have a large intermediate circuit capacitance.
Solution Approach 2:
Each converter with its small intermediate circuit capacitance serves itself and simultaneously supports other converters in the system. During generator-mode operation, the generated power is transferred through the coupling inductivities to support motor-mode converters, creating a self-sufficient system where each unit contributes to overall stability without requiring large local buffering capacity.
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 configuration allows for efficient power supply to electric motors, reducing power fluctuations and magnetic interference, enabling rpm-controlled operation with lower grid power consumption and cost-effective buffering, while minimizing oscillations and resonances.
Implementation Method 1
A first inductivity L1 connects the DC-voltage-side terminal of the first inverter to the DC-voltage-side terminal of the second inverter, enabling power transfer between converters
Implementation Method 2
A first capacitance C1 is connected in parallel with the DC-voltage-side terminal of the first inverter, and a second capacitance C2 is connected in parallel with the DC-voltage-side terminal of the second inverter
Data Source
AI summary
A drive system includes a first converter and at least one second converter. The first converter has, inside its housing, a first rectifier whose DC-voltage-side terminal is connected, e.g., directly connected, to the DC-voltage-side terminal of a first inverter of the first converter. A first capacitance is connected in parallel with the DC-voltage-side terminal of the first inverter. The second converter, or each second converter, has, inside its housing, a second rectifier whose DC-voltage-side terminal is connected via inductivities, i.e., for example, restrictors, to the DC-voltage-side terminal of a second inverter of the second converter. A second capacitance is connected in parallel with the DC-voltage-side terminal of the second inverter, and the DC-voltage-side terminal of the first inverter is connected via first inductivities to the DC-voltage-side terminal of the second inverter.