In August 2017, Liaoning RongxinXingye Power Technology Co., Ltd. signed the contract of 35kV dynamic reactive power generator SVG for Cangzhou Lingang Mitsubishi metal EAF, with voltage level of 35kV and capacity of 70MVar. The main wiring diagram is as follows:
The figure above shows the curve of three-phase reactive power and active power before and after SVG startup.
It can be seen from the figure that the maximum reactive power impact of the system before compensation is close to 30MVar, and the maximum reactive power impact of the system after compensation is lower than 4MVar. It can be seen from the active power curve that after compensation, the active power of the system has been significantly improved due to the stable grid voltage, which is conducive to improving the smelting speed.
The figure above shows the curve of three-phase average power factor before and after SVG startup.
It can be seen from the figure that the average power factor before the start of SVG is0.9, which is lower than the bottom limit of national standard, and the average power factor after the start of SVG is higher than 0.99.
The short-term flicker Pst curve before and after compensation is shown in the above figure.
The long-term flicker Plt curve before and after compensation is shown in the above figure.
Plt in the figure is calculated by 2-hours moving average. The flicker suppression ratio is about 5. To sum up, SVG realizes the comprehensive compensation for reactive power, harmonic and flicker of EAF load.
In March 2019, the company signed a commercial contract with an overseas steel plant to provide a complete set of power quality solutions for 130T electric arc furnace and supporting refining furnace. The top feeding mode is adopted by the on-site electric arc furnace. The capacity of the furnace transformer is 105MVA, and the grid access point is 35kV. 35kV busbar is supplied by 220kV/35kV special transformer with 160MVA capacity through short distance transmission line.
With data analysis and technical specifications confirmation, our company adopts 35kV/120MVar delta-connection cascade SVG device combined with FC fixed compensation equipment to comprehensively control the reactive power, harmonic, voltage imbalance, grid voltage fluctuation and flicker and other power quality problems in the smelting process of on-site electric arc furnace.
35kV/ 120MVar delta-connection cascade SVG device of the project is an outdoor container structure, including six power unit containers and one control and water-cooling system container. The power valve bank uses water-water cooling system which can provide good heat dissipation conditions for the power valve banksand ensure the safe and stable operation of the equipment.