Multiphase Converter Redundancy Control for DC Component Elimination
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Solution Overview
Problem
Existing power converters with distributed energy stores face challenges in maintaining a symmetrical three-phase voltage system without DC components when a fault occurs, leading to potential issues like neutral point shift and bearing currents, which can cause additional insulation requirements and operational inefficiencies.
Innovation Solution
The method involves controlling a corresponding number of two-pole subsystems in a faulty phase module to set their terminal voltages to zero, and similarly adjusting subsystems in undisturbed phase modules to maintain symmetry, thereby eliminating DC components in the output voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fault occurs in a subsystem of a power converter with distributed energy stores, then the converter can continue operating with reduced capacity, but DC components appear in the output voltages causing neutral point shift and bearing currents
Solution Approach 1:
The patent applies asymmetry by intentionally creating an unbalanced switching state in healthy subsystems to compensate for the faulty subsystem. Specifically, when a subsystem fails, the control method adjusts the switching patterns of remaining healthy subsystems in an asymmetric manner to counterbalance the fault effect, thereby eliminating DC components in output voltages and preventing neutral point shift while maintaining converter operation continuity
Solution Approach 2:
The patent changes the switching parameters of healthy subsystems dynamically in response to faults. By modifying the switching states and terminal voltage amplitudes of healthy subsystems based on detected fault conditions, the control method adjusts system parameters to maintain symmetry in output voltages and eliminate harmful DC components while preserving operational reliability
2Object-generated harmful factors
If the amplitude of terminal voltages of healthy subsystems is reduced to compensate for faults, then DC components are eliminated, but the overall output voltage amplitude decreases
Solution Approach 1:
The patent employs dynamic control where the switching states and terminal voltage amplitudes of healthy subsystems are continuously adjusted based on real-time fault detection. This dynamic adaptation allows the system to optimize the balance between eliminating DC components and maintaining sufficient output voltage amplitude, rather than using fixed reduced amplitudes that would unnecessarily limit power output
3Reliability
If a subsystem is completely switched off to ensure safety, then fault propagation is prevented, but the converter loses symmetry and generates DC components
Solution Approach 1:
The patent prepares compensatory control strategies in advance for potential subsystem failures. When a fault is detected, the control method immediately activates pre-planned asymmetric switching patterns in healthy subsystems that cushion against the loss of symmetry, preventing DC component generation while maintaining fault isolation. This prior preparation allows rapid response that preserves both safety and voltage system symmetry
Data Source
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AI summary
The invention relates to a method for controlling a converter having at least two phase modules (100) that comprise an upper and a lower valve branch (T1,..., T6), each of which is equipped with at least three bipolar systems (10) connected in series, in case at least one subsystem (10) of a valve branch (T1,..., T6) fails. In said method, the valve branch (T1,..., T6) having the disturbed subsystem (10) is determined, and one subsystem (10) of a valve branch (T1,..., T6) of each undisturbed phase module (100) is controlled such that the terminal voltages (UX21) of said subsystems (10) amounts to zero, said valve branch (T1,..., T6) of each undisturbed phase module (100) corresponding to the disturbed valve branch (T1,..., T6). According to the invention, a subsystem (10) of a valve branch (T1,..., T6) of the disturbed phase module (100) is controlled such that the terminal voltage (UX21) thereof equals zero, said valve branch (T1,..., T6) of the disturbed phase module (100) corresponding to the disturbed valve branch (T1,..., T6), and one subsystem (10) of a valve branch (T1,..., T6) of each undisturbed phase module (100) is controlled such that the terminal voltages (UX21) of said subsystems (10) amounts to zero, said valve branch (T1,..., T6) of each undisturbed phase module (100) corresponding to the valve branch (T1,..., T6) that corresponds to the disturbed valve branch (T1,..., T6). In the disclosed control method for using redundancy in case a multiphase converter having distributed energy stores (9) is disturbed, generated output voltages (UL10, UL20, UL30) have no more direct voltage portion.