Multiparallel Variable Frequency Drive Without DC Bus Links
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Solution Overview
Problem
High-power variable frequency drives face issues with power loss and increased costs due to the need for multiple parallel power stages, which result in current imbalance, thermal differences, and oversized components, leading to reduced efficiency and higher costs per watt.
Innovation Solution
The solution involves controlling each power stage individually and eliminating connections between DC buses, allowing for balanced current distribution and scalable parallel configurations, enabling greater redundancy and flexibility in power management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple parallel power stages are connected to increase drive power, then the power output increases, but current imbalance and thermal differences occur between stages
Solution Approach 1:
The invention divides the control system into independent control modules, with each module independently controlling a parallel power stage. This segmentation allows each stage to be controlled individually, compensating for component tolerances and preventing current imbalance, while still achieving high power output through parallel connection of multiple stages.
Solution Approach 2:
The invention applies different control strategies to different parallel power stages based on their individual characteristics. Each control module adjusts its control signals locally to account for variations in components such as input coils, ensuring that each stage operates optimally and contributes equally to the total power output, thereby maintaining current balance.
2Power
If multiple parallel power stages are connected to increase drive power, then the power output increases, but oversized components and extra ventilation are required
Solution Approach 1:
The invention segments the power stages and their control systems, allowing each stage to use standard-sized components rather than requiring oversized components for the entire system. By distributing the power delivery across multiple independently controlled stages, the system achieves high power output without needing excessively large individual components or ventilation infrastructure.
3Device complexity
If a single control module governs all parallel power stages, then the control system is simplified, but current imbalance and thermal differences occur
Solution Approach 1:
The control system is segmented into multiple independent control modules, each responsible for controlling a specific parallel power stage. This segmentation enables individualized control of each stage, allowing compensation for component variations and maintenance of current balance, while the modular structure keeps overall system complexity manageable.
Solution Approach 2:
Each control module incorporates feedback mechanisms that monitor the operating conditions of its associated power stage, including current and temperature. Based on this feedback, each controller dynamically adjusts its control signals to maintain optimal operation and current balance across all parallel stages, preventing thermal differences and ensuring reliable power delivery.
Data Source
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AI summary
The present invention relates to a multiparallel variable frequency drive (1) without a DC bus connection between power stages (3, 4i,...,n) connected in parallel and the control method thereof, which allows eliminating the power loss of the drive derived from increasing the power stages. The drive has a master control module (5) for the master power stage (3) and N-slave control modules (6i,...,n) for N-power stages (4i,...n). The drive additionally comprises ring control lines (8) and synchronization lines (7). The master control module is configured for controlling the motor to which the drive is connected and sending the control setpoints (voltage and current) to the slave control modules in such a way that all power stages deliver the same voltage and the same current to the motor.