Research On Isolated Cuk Three-Level AC-AC Converter

Paper introduces the current research status of the three-level DC converter and the three-level AC-AC Converter. It conclude that the three-level AC-AC direct converter has advantages of lower switch voltage stress, low harmonic content, high power density and bi-directional power flow. From the Buck-Boost Converter and Flyback converter, the rule of transforming non-isolated converters to corresponding isolated converters was derived. So a family of isolated high-frequency three-level DC-DC converter topologies and a family of isolated high-frequency three-level AC-AC converter topologies are proposed applying three-level technology. The Isolated Cuk Three-level AC-AC converter topology is consists of two isolated Cuk converters combined, using the AC switch unit instead of single switch to achive AC chopping, by which, an unstable power grid voltage could be transformed into an stable and adjustable sinusoidal alternating current.Paper research the isolated Cuk three-level AC-AC converter in detail. It focus on topology derivation process, operational modal analysis, input-output relations and the working principle. Besides, transient voltage feedback control strategy with high frequency AC chopping was developed. By modeling and simulation in Saber software, the correctness of operating principle analysis and control strategy has been verified. The parameters of the main components are optimized, which prepare for the experiment sample production. Finally, the article describes the process of parameter designing, circuit making and debugging. By resistive full load, inductive load and capacitive load tests, results show that the converter has excellent performance, which has met the design requirements.