UPS Inverter Phase Balancing via Bypass Mediator
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Solution Overview
Problem
Multi-phase UPS systems face challenges in addressing phase imbalance in loads, particularly when operating in high-efficiency bypass mode, as they reflect unbalanced loading to the utility source, leading to inefficiencies and potential power losses.
Innovation Solution
The implementation of an UPS system with an inverter that selectively loads phases and transfers power between phases or an auxiliary power source to compensate for load imbalances, utilizing a control circuit to manage phase balancing and potentially incorporating variably available power sources like solar or wind power to support this compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the bypass circuit is used to couple the AC input directly to the AC output for high efficiency operation, then energy losses in the rectifier/inverter chain are minimized, but phase imbalance in the load is not compensated and unbalanced loading is reflected to the utility source
Solution Approach 1:
The inverter is introduced as an intermediary component between the bypass circuit and the load. When phase imbalance is detected, the inverter is activated to compensate for the imbalance by injecting corrective currents, while the bypass circuit continues to provide efficient power transfer for the balanced portion of the load. This mediator approach allows the system to maintain high efficiency while providing phase balance compensation when needed.
2Ease of operation
If the inverter is activated to compensate for phase imbalance, then phase balance is maintained and utility source is protected from unbalanced loading, but energy efficiency is reduced due to rectifier/inverter processing
Solution Approach 1:
The system applies partial action by activating the inverter only for the portion of the load that requires phase balance compensation. The bypass circuit handles the majority of the power transfer efficiently, while the inverter is engaged only when and to the extent that phase imbalance exists. This partial engagement minimizes energy losses while providing necessary phase balance compensation.
3Ease of operation
If the inverter selectively loads phases and transfers power between phases, then phase imbalance is compensated, but device complexity increases
Solution Approach 1:
The inverter is designed with multi-functionality to perform both phase balance compensation and auxiliary functions such as integrating renewable energy sources and providing backup power capability. By making the inverter universal, the system avoids adding separate dedicated devices for each function, thereby managing complexity while providing comprehensive phase balance compensation and additional benefits.
Data Source
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AI summary
An uninterruptible power supply (UPS) system that includes a multiphase AC output configured to be coupled to a load, an inverter having an output coupled to the AC output and a control circuit operatively associated with the inverter and configured to cause the inverter to compensate for a phase imbalance of a load coupled to the AC output while power is being delivered to the load from an AC power source independently of the inverter.