Research On Cascaded Multilevel Inverter Based EPT And Its Control

Together with the rapid development of smart grid and the higher requirement ofpower quality, the traditional power transformer cannot well meet the requirement of smartgrid because of its scanty control means and unreliable power quality.In such a background,Electronic Power Transformer (EPT) as a new smart power transformer comes out. By themeans of Power electronic technology, EPT can make the active power, reactive power andfrequency of the primary and secondary side completely decouple, so it possesses manyspecial advantages superior to the traditional ones. It can largely improve power quality andsystem stability, therefore its study becomes more and more important.Considering the high voltage of EPT’s output inverter link, this paper proposes a EPTtopology combining cascaded multilevel inverters and CPS-SPWM modulation methodwhich can obtain higher equivalent switching frequency therefore reduces the outputfiltering.As to the controlling strategies of EPT, this paper considers the design of invertercontrolling in active and passive load two situations, and proposes a state feedbackdecoupled controlling based on the PARK transformation. Furthermore, the inverter’ssimulation model was established underMatlab/Simulink environment, and the resultsreviews the state feedback decoupled controlling make the system get a quick dynamic andnon-steady error after stability.Besides, an EPT prototype including cascaded seven-level inverters is set up, whichuses DSP as its control system to sample signal, calculate control and so on. And theexperimental results review that each input and output electric parameters can be controlledperfectly and precisely, which make EPT has a high research value in industry application.