An Over Modulation Strategy and Simulation Study for Matrix Converter

The over modulation strategy of matrix converter(MC) is put forward on the basis of conventional AC/DC/AC MC control theory. Firstly,imaginary AC/DC converter is over modulated to get the greatest fictitious DC voltage,secondly,imaginary DC/AC converter is over modulated,which effectively improve the voltage transfer ratio. Two voltage transfer ratio is emphatically analyzed with Fourier transform. At last,different modulation method is simulated with MATLAB,the simulation results verified the theoretical analysis and validity of the over modulation strategy,which provide a theoretical basis for the further research.

Evaluation of High Step-up Power Conversion Systems for Large-capacity Photovoltaic Generation Integrated into Medium Voltage DC Grids

With the increase of dc based renewable energy generation and dc loads,the medium voltage dc(MVDC)distribution network is becoming a promising option for more efficient system integration.In particular,large-capacity photovoltaic(PV)-based power generation is growing rapidly,and a corresponding power conversion system is critical to integrate these large PV systems into MVDC power grid.Different from traditional ac grid-connected converters,the converter system for dc grid interfaced PV system requires large-capacity dc conversion over a wide range of ultra-high voltage step-up ratios.This is an important issue,yet received limited research so far.In this paper,a thorough study of dc-dc conversion system for a medium-voltage dc grid-connected PV system is conducted.The required structural features for such a conversion system are first discussed.Based on these features,the conversion system is classified into four categories by series-parallel connection scheme of power modules.Then two existing conversion system configurations as well as a proposed solution are compared in terms of input/output performance,conversion efficiency,modulation method,control complexity,power density,reliability,and hardware cost.In-depth analysis is carried out to select the most suitable conversion systems in various application scenarios.

How to build good inverters from nanomaterial-based transistors

As promising components of future integrated circuits(ICs),field-effect transistors(FETs)based on semiconducting nanomaterials are being extensively investigated.As the most essential component of ICs,inverters are favored to be demonstrated at the infant stage of emerging technologies.However,systematic research is absent to reveal how the parameters of transistors affect the performance of inverters,e.g.the voltage transfer characteristics(VTCs).In this work,systematic analysis about the dependency between transistor-and inverter-level metrics have been carried out for both complementary metal-oxide-semiconductor(CMOS)and monotype(p-type-only and n-type-only)technologies,which is further experimentally demonstrated by carbon nanotube FETs and ICs.We also propose guidelines towards the high noise margin and rail-to-rail inverter design based on nanomaterials.