Parallel Transformer Zero-Sequence Current Limiting
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing power supply systems connected to AC networks experience significant homopolar current, which is not adequately limited, leading to inefficiencies and potential issues in power transmission.
Innovation Solution
A power supply system incorporating a transformer with two electromagnetic coils connected in parallel to the converter, along with passive elements, to create a current feedback loop that effectively limits zero-sequence current by reinjecting opposing currents at the input terminals, thereby minimizing homopolar current injection into the network.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a converter is connected directly to the AC network without a transformer, then the device complexity is reduced and power transmission efficiency is improved, but zero-sequence current is not adequately limited causing harmful effects on the network
Solution Approach 1:
The patent introduces a transformer as an intermediary component between the converter and the AC network. This transformer includes a primary winding connected to the network and a secondary winding connected to the converter, serving as a mediator that blocks zero-sequence current from entering the network while allowing power transmission to continue efficiently.
Solution Approach 2:
The patent segments the power transmission path by separating the converter and the AC network through a transformer with distinct primary and secondary windings. This segmentation allows the system to maintain direct converter-to-network connection benefits while adding targeted zero-sequence current limitation capability through the transformer structure.
2Object-generated harmful factors
If a transformer is added to limit zero-sequence current, then the harmful effects on the network are reduced, but the device complexity and power loss increase
Solution Approach 1:
The patent applies local quality by designing the transformer with specific winding configurations (primary and secondary windings with particular turns ratios) that provide zero-sequence current limitation only where needed at the network interface, while maintaining efficient power transmission through the converter connection. This localized approach minimizes overall energy loss while providing targeted harmful factor reduction.
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
The system significantly reduces or eliminates zero-sequence current circulation between the network and the load, enhancing power supply efficiency and stability by forming a current feedback loop that compensates for zero-sequence currents.
Implementation Method 1
a transformer (36) connected in parallel to the converter (22), between the input terminals (18) and the output terminals (20), the transformer (36) comprising a first (38) and a second (40) electromagnetic coil
Data Source
Figure 1
Figure 2
AI summary
The system has input terminals (18) designed to be connected to a power grid (12), and output terminals (20) designed to be connected to a load (14). A converter (22) converts an input voltage into an output voltage, where the converter is connected between the input terminals and the output terminals. A limiting device (24) limits a residual current flow between the power grid and the load. The limiting device includes a transformer (36) connected in parallel to the converter, between the input and output terminals, where the transformer includes two electromagnetic coils (38, 40). An independent claim is also included for a drive chain.