Thyristor Power Converter Voltage Compensation Modules
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Solution Overview
Problem
Thyristor-based line-commutated polyphase power converters face operational challenges on weak AC-voltage grids due to voltage dips, leading to commutation errors and instabilities, making it difficult to maintain reliable operation.
Innovation Solution
A method and arrangement that utilize a series circuit of modules with electronic switching elements and energy stores to generate additional voltage temporarily during commutation, compensating for voltage dips and ensuring stable operation by increasing the voltage at the AC-voltage terminal, thereby ensuring successful commutation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a thyristor-based power converter is operated on a weak AC-voltage grid, then the power converter can be deployed in more locations (including HVDC transmission), but commutation errors and instabilities occur due to voltage dips
Solution Approach 1:
The patent introduces series-connected voltage source modules as intermediary devices between the weak AC grid and the thyristor-based power converter. These modules generate compensating voltages that mediate the interaction between the grid and converter, ensuring reliable commutation by supplementing the voltage during critical commutation periods despite grid voltage dips
Solution Approach 2:
The patent dynamically changes the output voltage parameter of the series-connected modules based on grid conditions. When voltage dips are detected, the modules adjust their output voltage to compensate, thereby maintaining the required voltage-time integral for successful commutation. This parameter adaptation enables operation on weak grids while preserving commutation stability
2Reliability
If additional voltage is generated by series circuit of modules to compensate for voltage dips, then commutation is ensured, but device complexity increases
Solution Approach 1:
The patent divides the voltage compensation function into multiple independent series-connected modules, each with its own switching elements and energy store. This segmentation allows the system to achieve the required voltage compensation while maintaining modular simplicity and enabling selective activation of modules based on the severity of voltage dips
Solution Approach 2:
The patent employs periodic switching of the electronic switching elements in the series modules to generate the required additional voltage. The switching operates in synchronisation with the grid frequency and commutation timing, providing voltage supplementation only during critical periods when needed, thereby reducing average complexity and energy consumption
3Reliability
If additional voltage is generated continuously to maintain stable operation, then commutation is always safe, but energy consumption increases
Solution Approach 1:
The patent implements periodic or event-triggered voltage generation by the series modules rather than continuous generation. The modules activate only during voltage dips or commutation events, switching their energy stores periodically or on-demand based on grid conditions, thereby ensuring stable operation while minimising energy consumption from the energy stores
Solution Approach 2:
The control system monitors grid voltage and automatically activates the series modules only when voltage dips are detected, allowing the system to self-regulate energy usage. The modules serve themselves by switching their energy stores based on real-time grid conditions, providing compensation only when necessary and avoiding unnecessary energy consumption during normal grid operation
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 solution allows for reliable operation of thyristor-based power converters on weak AC-voltage grids by compensating for voltage dips, ensuring fault-free commutation and reducing reactive power consumption, which is advantageous for both economic and operational efficiency.
Implementation Method 1
each module has a first electronic switching element, a second electronic switching element and an electrical energy store
Data Source
AI summary
A method of operating a thyristor-based line-commutated multi-phase power converter on a multi-phase AC voltage connection point, which is supplied by an AC voltage network. Between the AC voltage connection point and an AC voltage connection of the power converter, a series circuit of modules is arranged for each phase. Each of the series circuits has a first electronic switching element, a second electronic switching element, and an electric energy storage device. The voltages of the phases of the AC voltage connection point are measured and, if an undervoltage is detected on a phase of the AC voltage connection point, an additional voltage adding to the voltage of that phase is generated by way of the series circuit of modules allocated to that phase in such a way that the voltage of that phase is increased, at least temporarily.