Rectifier-Inverter Arc Furnace Power Supply for Flicker Decoupling
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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, primary side current, and electrode manipulation, 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 is improved, but the cost and equipment capacity requirements increase significantly
Solution Approach 1:
The patent divides the power conversion system into two separate bridges: a rectifier bridge for AC-DC conversion and an inverter bridge for DC-AC conversion. This segmentation allows each bridge to be optimized independently, with the rectifier bridge handling power factor correction and the inverter bridge handling flicker compensation, thereby reducing the overall equipment capacity required compared to a single large STATCOM unit.
Solution Approach 2:
The dual-bridge converter performs multiple functions simultaneously: it provides power factor correction, flicker compensation, and harmonic filtering. The rectifier bridge handles active power conversion while the inverter bridge manages reactive power compensation and flicker reduction, making the system multi-functional and reducing the need for separate dedicated equipment.
2Object-affected harmful factors
If multiple power electronic converters with multi-winding phase-shifting transformers are used, then flicker isolation is improved, but the system complexity and cost increase
Solution Approach 1:
The patent extracts the phase-shifting function from traditional multi-winding transformers and implements it through control strategies in the dual-bridge converter. The rectifier and inverter bridges work together to provide galvanic isolation and flicker decoupling through controlled power flow, eliminating the need for complex multi-winding phase-shifting transformers while achieving the same isolation effect.
Solution Approach 2:
The DC link capacitor serves as an intermediary between the rectifier bridge and inverter bridge, providing galvanic isolation and decoupling the AC grid from the arc furnace load. This intermediate energy storage element allows independent control of active and reactive power, achieving flicker isolation without requiring complex transformer configurations.
3Device complexity
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 dynamic control strategies for both the rectifier bridge and inverter bridge, allowing real-time adjustment of switching patterns and power flow. The rectifier bridge uses pulse-width modulation (PWM) control to achieve sinusoidal input current, while the inverter bridge dynamically compensates for load fluctuations, thereby reducing harmonic content through active control rather than passive filtering.
Solution Approach 2:
The system implements feedback control mechanisms where the rectifier bridge controller and inverter bridge controller continuously monitor system parameters and adjust their operation accordingly. The controllers use feedback signals to maintain unity power factor, minimize harmonics, and compensate for flicker, replacing the need for complex passive filter networks with simpler active control.
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 isolates AC arc furnace fluctuations from the power grid, reduces flicker and harmonic currents, and can be retrofitted to existing AC arc furnaces without additional transformers, providing stable power supply.
Implementation Method 1
a rectifier bridge, connected to an AC power grid... The rectifier bridge includes three-phase rectifier bridge arms
Implementation Method 2
an inverter bridge, connected to the AC arc furnace transformer... the inverter bridge includes at least one-phase inverter bridge arm
Implementation Method 3
AC arc furnace uses scrap steel and iron as the main raw materials, and utilizes high-temperature arcs generated between electrodes and the charge to heat and melt the charge
Data Source
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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.