| The submerged arc furnace is a kind of important load in metallurgical industry. Due to the frequent fluctuations of power in smelting process, the arc furnace is generally connected to large power grid. However, in some regions where is backward in power grid and is rich in mineral resources, the autonomous power plant, which operates as an isolated power grid, is the only option in ferroalloy smelting project. The isolated power grid is easily drawn by load disturbance. The submerged arc furnace, whose power existing random fluctuations and steep fall under the extreme conditions, may cause system frequency, voltage value beyond the allowable range. Under this condition, the isolated power grid may lose stability caused by the generator protection’s operation.This paper established the mathematical models of isolated power grid with submerged arc furnace connected, analysed the power control principle and control strategy of SPLC, and pointed out the critical condition under which the constant power control can be realized. On this basis, the coordinated control strategy of SPLC and braking resistor is presented. Simulation results showed that the proposed method can realize power control under various working conditions, and provide reliable guarantee for the stable operation of isolated power grid for submerged arc furnace.The submerged arc furnace is nonlinear and time varying load, and causes harmonic and three-phase unbalance problem. SPLC and braking resistor also produce harmonic current. Therefore, the comprehensive compensation scheme for the power supply system of submerged arc furnace is researched in this paper, which is based on the delta-connected cascaded static synchronous compensator. The results of simulation showed that the compensator could greatly reduce the harmonic, reactive and negative sequence current of the isolated grid. It not only benefits the generator, but also improves the power quality. |
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