Research On The Integrated Compensation Of Reactive And Negative Currents For Unbalanced Load

With the rapid development of various industries, the scale of modern power system is increasing quickly. The new contradictions and new problems of the power system are becoming more prominent. On the one hand, a variety of complex, accurate electrical equipment, such as arc furnace, rolling mill and electrical locomotive, which are sensitive for power quality are increasing continuously, allowing users need higher power grid reliability and power quality. These loads, which have the electric characteristics of asymmetry or impact, bring so much power quality problems as low power factor, voltage fluctuation and flicker, three phase voltage and current unbalanced, and etc. These contradictions and problems will not only affect the performance of electrical equipment, moreover they will also threat to the entire power system normal operation.Therefore, improving the power quality and system stability has aroused a high concern of academic and engineering at home and abroad, and has become one of the hot topics in electrical technical research. In this paper, the main job is that analyzes and researches synthetic compensation of negative sequence and reactive current in response to unbalanced load in power grid.First, in the article, analyzes the synthetic compensation principle of the negative sequence and reactive power. And on the basis of the compensation principle, introduces two compensation devices which are continuously adjustable, including the Static Var Compensator (SVC) and Static Synchronous Compensator (STATCOM), and discusses their basic structure and compensation principle, respectively.Then, based on SVC and STATCOM's respective compensation characteristics, introduces a deduced method of compensation susceptance, which is suitable for SVC compensation device and current detection control method which is suitable for STATCOM compensation device.Finally, based on the unbalanced compensation principle and unbalanced detection control method, uses MATLAB/SIMULINK simulation software to achieve synthetic compensation simulation of unbalanced load about the SVC and STATCOM compensation device designed using inverse-system technique and variable structure control method. Through simulation results, compare their methods of the detection control, respectively, as well as analyzes their compensation advantages and disadvantages of these compensation devices.