Tapped Transformer Control to Minimize Rectifier Reactive Power
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Solution Overview
Problem
Thyristor-based rectifiers in DC load systems, such as electrolysis systems, are unable to actively control reactive power, which poses challenges in maintaining grid stability, especially during network disturbances like voltage drops.
Innovation Solution
A reactive power supporting method for DC load systems in AC networks, which includes a tapped transformer with a tap changer and a control system that uses droop controls to minimize reactive power consumption by adjusting the tap position based on voltage and frequency monitoring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thyristor-based rectifiers are used for DC load systems, then efficiency and reliability are improved, but reactive power control capability deteriorates
Solution Approach 1:
The patent introduces a reactive power compensator as an intermediary device between the thyristor-based rectifier and the AC network. This compensator actively compensates for the reactive power consumed by the rectifier, enabling the system to meet power factor requirements while maintaining the reliability benefits of thyristor-based technology.
2Stress or pressure
If tap changer position is increased to adjust voltage, then voltage level is improved, but power factor deteriorates due to increased reactive power consumption
Solution Approach 1:
The patent implements a control system that continuously monitors the power factor and tap changer position, and automatically adjusts the tap changer to optimal positions. This feedback mechanism ensures that the transformer operates at positions that minimize reactive power consumption while maintaining adequate voltage levels, resolving the contradiction between voltage support and power factor maintenance.
3Stability of the object's composition
If reactive power is reduced to support voltage during network disturbances, then grid stability is improved, but active power consumption must be reduced to minimum operational point
Solution Approach 1:
The reactive power compensator acts as an intermediary that can independently provide or absorb reactive power without affecting the active power flow to the DC load. This allows the system to reduce reactive power consumption to support grid voltage stability during disturbances while maintaining normal active power consumption levels, avoiding the need to reduce production.
Data Source
Figure 1
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AI summary
A reactive power supporting method for a DC load system (1) in an AC network (2), the DC load system (1) comprising a DC load unit (3) and a tapped transformer (4) with a tap changer (5) comprising several tap positions (6), a primary side (7) of the tapped transformer (4) being connected to the AC network (2) and a secondary side (8) of the tapped transformer (4) being connected to the DC load unit (3) via a rectifier (9) for supplying DC power to the DC load unit (3) with an input voltage to the rectifier (9) determined by the selection of a tap position (6) and a firing angle of a phase fired control (10), wherein if frequency or voltage of the AC network (2) are exceeding or falling below specified limits, the tap position (6) is selected such that the firing angle is as small as possible and thus the reactive power is minimized. The invention is also about a DC load system (1) with a reactive power supporting function for an AC network (2).