| The power electronic devices based on the new wide band gap semiconductor materials have been developed and commercially available.The high switching speed characteristics of the power electronic devices have brought great challenges to the converters with traditional bridge arm structure while improving the efficiency and switching frequency of the converter.In some applications,the traditional converter structure can not maximize the performance of the new semiconductor devices.SiC MOSFET has become one of the best wide band gap semiconductor devices due to its fast switching speed,high voltage withstand capacity and low switching loss.Because of the fast switching speed,SiC MOSFET is seriously affected by parasitic parameters.When SiC MOSFET is applied to converters with traditional bridge arm structure,dv/dt caused by high switching speed will generate a large charging current and serious crosstalk in devices and load parasitic capacitors.Another big challenge for traditional bridge arm structure converter is the performance degradation of the converter caused by dead zone.Dead band not only reduces DC voltage utilization of converter,but also increases harmonic content of the system.And when the switching frequency of converter is too high,the dead band may swallow some narrow switch state.Therefore,the system of adjustment must be reduced properly.This will also reduce the DC voltage utilization.This paper introduces a three-level split output converter,and studies its topology and control method.Three level split output converter is a topology of the converter based on T-type three-level converter.In this paper,the one-phase switching function of the topology is established based on the topology.The current path,potential state and voltage stress of each switch state in the switch function are analyzed.Three switch states are selected to design SPWM deadband modulation strategy of the topology by comparing the switch states.A deadband modulation program for three-level split topology is developed.Three level split output converter and three-level T-type converter with power of 2.6kw are built.The reliability of deadband free modulation is verified at 600 V voltage.The principle of crosstalk suppression of three-level split output converter is analyzed by comparison experiments.The experiment results show that the topology has the advantages of reducing high frequency harmonic and improving power quality.The paper analyzes the shortcomings of the three-level split output topology,and points out that the insulation of the AC output side inductors in the field of high voltage applications will be an important factor affecting the development of the three-level split output topology.There are 58 pictures,7 tables and 80 references in this paper. |
