Asymmetrical Current Feeding via Sequence Component Superposition
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Solution Overview
Problem
Existing three-phase AC voltage networks face instability and component stress due to asymmetrical loads, which traditional power plants, especially those using synchronous generators, struggle to compensate for, leading to potential malfunctions and increased aging of components.
Innovation Solution
The method involves representing an asymmetrical three-phase AC voltage system as a positive sequence component and a negative sequence component, using separate inverter modules to generate and superimpose these components to form a symmetrical three-phase alternating current, which is then fed into the network, thereby avoiding asymmetrical loading of individual bridge branches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a full converter is operated at permissible power limit to feed asymmetrical current into the AC voltage network, then the power supply capability is improved, but the load limit for individual bridge branches is exceeded causing increased aging and malfunctions
Solution Approach 1:
The invention segments the asymmetrical current feed into two separate symmetrical current feeds: a positive sequence current component and a negative sequence current component. Each component is fed through dedicated converter branches that are designed to handle symmetrical loads, preventing any single branch from exceeding its load limit while maintaining overall power supply capability.
Solution Approach 2:
The invention applies asymmetry by intentionally creating symmetrical current components (positive and negative sequence) that when combined produce the desired asymmetrical effect on the network. The converter uses asymmetrical control strategies to generate balanced current sets that compensate for network asymmetries without overloading individual branches.
2Adaptability or versatility
If traditional synchronous generators are used to feed the AC voltage network, then the power plant can operate, but it is practically impossible to intervene in individual phases to compensate for asymmetry
Solution Approach 1:
The invention replaces the mechanical synchronous generator system with an electrical converter system that uses power electronic switches and control circuits. This substitution enables independent control of each phase and current component, providing the adaptability to compensate for asymmetries while managing complexity through digital control strategies.
Solution Approach 2:
The invention introduces dynamic control capabilities by using a converter system that can rapidly adjust current magnitudes and phases in real-time. The control unit continuously monitors network conditions and dynamically modifies the positive and negative sequence current components to maintain symmetry compensation, unlike the static synchronous generator system.
3Stability of the object's composition
If asymmetrical current is fed into the AC voltage network, then the network asymmetry can be addressed, but excessive deviations can endanger network stability and cause damage to sensitive consumers
Solution Approach 1:
The invention applies preliminary anti-action by proactively injecting positive and negative sequence current components that counteract detected asymmetries before they can cause harmful effects. The control unit continuously monitors voltage asymmetry and preemptively adjusts the current injection to maintain network stability and protect sensitive consumers from excessive deviations.
Data Source
Figure 1~2c
Figure 3
AI summary
The present invention relates to a method for feeding an unbalanced, three-phase current into a three-phase AC voltage system, comprising the following steps: Production of a positive phase-sequence system for the current to be fed in, production of a negative phase-sequence system for the current to be fed in, superimposition of the positive phase-sequence system and of the negative phase-sequence system to form the current to be fed in, and feeding of the current that has been composed in this way into the three-phase AC voltage system.