AC Arc Furnace Power Supply Control for Grid Flicker Isolation
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Solution Overview
Problem
AC arc furnaces cause significant interference to power supply systems due to flicker, asymmetric, and high-order harmonic currents, which existing solutions like STATCOM and modular multilevel converters are costly or complex, and cannot be easily retrofitted to existing systems.
Innovation Solution
A flexible power supply device comprising a rectifier bridge, inverter bridge, arc furnace transformer, rectifier bridge controller, inverter bridge controller, and electrode position controller, with specific control methods to stabilize DC voltage, current, and arc impedance, reducing flicker and harmonic currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If STATCOM is used to compensate dynamic reactive power and reduce flicker, then flicker suppression effect is improved, but equipment capacity requirement increases and cost increases
Solution Approach 1:
The patent introduces a flexible power supply device as an intermediary between the AC arc furnace and the power grid. This device includes a rectifier bridge, inverter bridge, and DC link, which acts as a mediator to decouple the fluctuating load from the grid, thereby reducing flicker without requiring large-capacity STATCOM equipment
Solution Approach 2:
The patent replaces the traditional mechanical/reactive power compensation approach (STATCOM) with a power electronic conversion system. The flexible power supply device uses controlled rectification and inversion to actively manage power flow, substituting the passive reactive power compensation mechanism with an active electronic control system that more efficiently reduces flicker
2Object-affected harmful factors
If multiple power electronic converters with multi-winding phase-shifting transformers are used, then flicker isolation is improved, but system complexity and cost increase
Solution Approach 1:
The patent extracts the essential function of flicker isolation from the complex multi-winding phase-shifting transformer system and implements it through a simplified flexible power supply device. By taking out only the necessary power conversion functionality and implementing it through controlled rectifier-inverter bridges, the system achieves flicker isolation without the complexity of multiple transformers and converters
Solution Approach 2:
The flexible power supply device performs multiple functions including power conversion, flicker reduction, harmonic filtering, and reactive power compensation through a single integrated system. This multi-functional approach replaces the need for separate phase-shifting transformers and multiple converters, significantly reducing system complexity while maintaining effectiveness
3Quantity of substance
If diode rectifier with modular multilevel bridge is used, then cost is reduced, but control complexity increases and harmonic content increases
Solution Approach 1:
The patent employs dynamically controllable power electronic switches (IGBTs or MOSFETs) in the rectifier and inverter bridges, allowing real-time adjustment of switching patterns to optimize performance. This dynamic control enables the system to maintain low harmonic content and manageable control complexity while achieving cost-effective operation, unlike static diode rectifiers
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 device effectively reduces flicker and harmonic currents, simplifies system control, and can be retrofitted to existing AC arc furnaces without additional transformers, providing stable power supply.
Implementation Method 1
a rectifier bridge, an inverter bridge, an arc furnace transformer... The rectifier bridge is connected to an AC power grid
Implementation Method 2
the inverter bridge is connected to the AC arc furnace transformer... an upper inverter bridge arm and a lower inverter bridge arm
Implementation Method 3
an arc furnace transformer... the connection point is connected to the corresponding phase of the electric arc furnace transformer
Implementation Method 4
utilizes high-temperature arcs generated between electrodes and the charge to heat and melt the charge
Data Source
AI summary
The embodiments of the present disclosure provide a flexible power supply device for an AC arc furnace and a control method thereof, which are applied in the technical field of power supply. The flexible power supply device for an AC arc furnace comprises a rectifier bridge, an inverter bridge, an arc furnace transformer, a rectifier bridge controller, an inverter bridge controller and an electrode position controller, wherein the rectifier bridge is connected to an AC power grid, and the inverter bridge is connected to an AC arc furnace transformer; and, the rectifier bridge controller is responsible for controlling the rectifier bridge and stabilizing a DC voltage of the rectifier bridge, and the inverter bridge controller is responsible for controlling the inverter bridge and stabilizing a primary side current of the AC arc furnace transformer. The flexible power supply device for an AC arc furnace realizes the double isolation of the fluctuation of the AC arc furnace from a power supply system through the inverter bridge and the rectifier bridge, thus significantly reducing the flicker of the power grid caused by the fluctuation of the AC arc furnace and reducing the influence of the smelting process of the arc furnace on the power grid.