Dynamic DC Bus Control for Motoring and Regenerating AFE Power Converters
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Solution Overview
Problem
Existing power conversion systems face inefficiencies in managing DC bus voltage regulation and power limiting, particularly in applications where power flow direction alternates between motoring and regenerating operations, leading to suboptimal energy harvesting and increased system size and cost.
Innovation Solution
A power converter with a controller that dynamically regulates DC bus voltage between specific limits and limits power according to direction-specific parameters, employing linear and nonlinear power limiting strategies to optimize energy storage and retrieval from DC bus capacitors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If DC bus voltage is regulated using conventional methods, then voltage stability is maintained, but system efficiency is suboptimal and energy harvesting is reduced
Solution Approach 1:
The patent implements dynamic bus control that adapts voltage limits and power limiting parameters based on operating conditions. The controller dynamically adjusts between motoring and regenerating voltage limits, and modifies power limiting behavior based on DC bus voltage level, enabling optimal energy harvesting during regeneration while maintaining stability during motoring operations
Solution Approach 2:
The system changes operational parameters based on power flow direction and voltage levels. During regeneration, the controller applies different voltage limits and power limiting strategies compared to motoring mode. The power limiting parameter is adjusted as a function of DC bus voltage to maximize energy recovery while preventing overvoltage conditions
2Use of energy by moving object
If power limiting is applied during regeneration, then energy storage is maximized, but overvoltage trips may occur
Solution Approach 1:
The controller continuously monitors DC bus voltage and uses this feedback to dynamically adjust power limiting behavior. When voltage approaches the regenerating voltage limit, the controller increases power limiting to prevent overvoltage trips. This closed-loop control ensures energy is maximized within safe operating boundaries
Solution Approach 2:
The system preemptively applies power limiting before overvoltage conditions occur. By monitoring voltage levels and adjusting power limits in advance, the controller prevents overvoltage trips from occurring in the first place, rather than reacting after the problem arises
3Loss of energy
If separate voltage limits are used for motoring and regenerating operations, then energy harvesting is optimized, but control complexity increases
Solution Approach 1:
The controller dynamically switches between motoring and regenerating modes based on power flow direction. Each mode has optimized voltage limits and power limiting parameters stored in lookup tables or defined by equations. The system seamlessly transitions between modes, applying the appropriate control strategy for each operating condition to maximize energy harvesting
Solution Approach 2:
Different voltage limits and power limiting parameters are applied based on the operating mode. During regeneration, higher voltage limits and aggressive power limiting are used to maximize energy recovery. During motoring, different parameters maintain stable operation. This parameter adaptation resolves the contradiction by optimizing for each mode separately
Data Source
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AI summary
A power converter having a dynamic bus controller to control a rectifier DC output for motoring and regenerating power flow directions, in which the controller controls a DC bus voltage between first and second regenerating voltage limits and limits power at the DC output in an increasing fashion with increasing values of the DC bus voltage according to a regenerating power limit parameter for a regenerating direction of power flow at a DC output. For a motoring direction of power flow at the DC output, the controller controls the DC bus voltage at the DC output between first and second motoring voltage limits and limits the power at the DC output in a decreasing fashion with increasing values of the DC bus voltage according to a motoring power limit parameter.