Research On Multilevel SVG

With the rapid development of electric power network and FACTS devices, theadvantage of reactive power compensation with SVG is gradually being recognized; its effecton the high voltage transmission network reactive power compensation is especially striking.In today’s trend of high voltage transmission network improving in the voltage level andsmart grid’s development in the word, SVG has become the attention and research target forboth national and foreign experts and scholars. After the adoption of multiple transformer andtraditional2H chain structure, how to further improve the SVG output voltage level andcapacity, how to make the SVG been used in modern high voltage transmission network, hasbecome the problem need to consider in today’s SVG research.In order to improve the SVG output voltage level and capacity, this paper uses DCvoltage1E-2E2H-2H of hybrid cascaded seven-level unit as basic power unit of multilevelcascade SVG that based on summarizing the basic principle and reactive current detectionmethod, through the analysis of the hybrid cascaded inverter structure, considered from theoutput voltage can be completely PWM control. This main circuit structure does not needmultiple transformers, all hybrid cascaded seven level units in each phase connect in cascade,and this structure can effectively improve the SVG output voltage and voltage level number.The SVG use Part Carrier Stacking PWM control method and Carrier Phase Shifting PWMcontrol method to control hybrid cascaded seven-level units, so the SVG performance can befurther improved. And the capacitor voltage imbalance of multilevel cascade SVG can becontrolled within a certain range through the improving of Carrier Phase Shifting PWMcontrol method. Finally, this paper uses SIMULINK of MATLAB to simulate this multilevelcascade SVG system, and compares with the traditional2H cascade SVG. The simulationresults show that the multilevel cascade SVG using hybrid cascaded seven-level units has agood performance and has some practical significance.