Hybrid Rectifier Switching for Low-Reactive-Power Electrolysis
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Solution Overview
Problem
Existing electrolysis systems face challenges in managing reactive power exchange with the AC grid, particularly in partial load ranges and with grid voltage amplitudes outside the tolerance band, which is undesirable and often requires complex and inefficient reactive power compensation systems.
Innovation Solution
A hybrid rectifier system combining thyristor and transistor rectifiers, where the thyristor rectifier handles base load and reactive power compensation, while the transistor rectifier provides additional active power and reactive power compensation, enabling grid-forming and grid-supporting modes without additional energy storage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a thyristor rectifier is used for electrolysis systems, then investment costs are reduced, but reactive power exchange with the AC grid increases significantly in partial load range and with grid voltage outside tolerance band
Solution Approach 1:
The patent combines a thyristor rectifier and a transistor rectifier into a hybrid configuration where both rectifiers work together. The thyristor rectifier handles the base load while the transistor rectifier provides reactive power compensation and operates in grid-forming mode, eliminating the need for separate compensation systems and reducing total reactive power exchange with the grid.
Solution Approach 2:
The transistor rectifier in the hybrid system performs multiple functions simultaneously: it provides reactive power compensation, operates in grid-forming mode to support grid stability, and contributes to active power delivery. This multi-functionality replaces what would otherwise require separate dedicated compensation systems.
2Use of energy by moving object
If reactive power compensation systems are added to thyristor rectifiers, then reactive power exchange is reduced, but system complexity and cost increase
Solution Approach 1:
Instead of adding separate compensation systems, the patent merges the compensation function into the rectifier structure itself by using a hybrid configuration. The transistor rectifier is integrated with the thyristor rectifier, and both share common DC link capacitors that serve as energy buffer stores, eliminating the need for additional separate compensation equipment.
Solution Approach 2:
The transistor rectifier serves multiple purposes: reactive power compensation, grid-forming operation, and active power delivery. This multi-functionality means that a single component performs what would otherwise require multiple separate systems, thereby reducing overall system complexity despite the advanced functionality provided.
3Use of energy by moving object
If a transistor rectifier is used for reactive power compensation, then reactive power management is improved, but additional energy storage requirements increase system complexity
Solution Approach 1:
The DC link capacitors of both the thyristor rectifier and transistor rectifier serve dual purposes: they act as energy buffer stores for the respective rectifiers and collectively provide the energy storage needed for the transistor rectifier to operate in grid-forming mode. This eliminates the need for separate dedicated energy storage systems.
Solution Approach 2:
The energy storage function is merged into the existing DC link capacitor structure of the hybrid rectifier system. The capacitors that are already present for voltage stabilization and power decoupling are utilized additionally for grid-forming operation, eliminating redundant energy storage components.
4Use of energy by moving object
If actively controllable rectifiers with transistor technology are used, then reactive power compensation and grid-forming modes are achieved, but investment costs increase compared to thyristor technology
Solution Approach 1:
The patent segments the rectifier functions between two different technologies: the thyristor rectifier handles the majority of active power conversion and base load operation where cost-effectiveness is critical, while the transistor rectifier is used only for reactive power compensation and grid-forming functions. This segmentation allows the system to achieve advanced functionality without fully replacing cost-effective thyristor technology throughout the entire system.
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 hybrid rectifier system effectively minimizes reactive power exchange, optimizes power utilization, and supports grid stability by instantaneously adjusting to frequency and voltage changes, eliminating the need for separate energy storage and reducing conversion losses.
Implementation Method 1
Actively controllable rectifiers have semiconductor switches for rectifying AC voltage and/or AC current into DC voltage and/or DC voltage
Data Source
AI summary
A method for operating a hybrid rectifier includes an AC input, a DC output and a thyristor rectifier arranged in a first path, and a transistor rectifier arranged in a second, parallel path. The method includes when a DC voltage at the DC output of the hybrid rectifier is below a voltage threshold value, operating the hybrid rectifier in a first operating state in which the transistor rectifier is isolated from the DC output and connected to the AC input and the thyristor rectifier is connected both to the AC input and to the DC output. When the DC voltage at the DC output of the hybrid rectifier reaches or exceeds the voltage threshold value, operating the hybrid rectifier in a second operating state in which the thyristor rectifier and the transistor rectifier are each connected to the AC input and to the DC output.