Hybrid Three-level ANPC Topology And Its Capacitor Voltage Balance Control

With the continuous updating of power electronic devices and the development of power electronic technology,400Hz medium frequency inverters have been widely used in the aerospace field.With the proposal of a new architecture with higher voltage level,multi-level power electronic inverters,as the core components of aircraft power system,have received more and more attention and research.Based on the active neutral-point clamped(ANPC)three-level converter topology,a hybrid three-level ANPC topology composed of SiC and Si devices is deeply studied in this paper.On the basis of comparative analysis of the comprehensive performance of the topology,the unbalanced mechanism of capacitor voltage and its balancing control strategy in the hybrid three-level ANPC topology are further studied,and experiments are carried out through designing an experimental platform.1.On the basis of introducing the mainstream three-level topology,the formation idea of hybrid ANPC three-level topology and the corresponding modulation strategy based on SPWM are analyzed,and the circuit commutation process of hybrid ANPC three-level topology under the corresponding modulation strategy is analyzed.At the same time,the switching loss of hybrid ANPC three-level topology,Si-based ANPC three-level topology and SiC-based ANPC three-level topology are compared and analyzed.It is concluded that the switching loss of hybrid ANPC three-level topology inverters in high power applications is slightly higher than that of SiC-based ANPC three-level topology and much lower than that of Si-based ANPC three-level topology.2.Firstly,a mathematical model for the voltage variation of hybrid ANPC three-level topological capacitor is constructed based on the switching state and output current.Based on the model,the relationship between zero sequence component and neutral point current is discussed.On this basis,the voltage balance control strategy of the neutral capacitor injected with zero sequence component is introduced.This strategy has the advantages of less computation and simple control.Finally,the effectiveness of the neutral capacitor voltage balance control strategy with zero sequence component inj ection is verified in the simulation.3.The three-phase hybrid ANPC three-level topology experimental platform is introduced,and the modulation strategy based on SPWM and the neutral-point potential balance control strategy based on zero-sequence voltage injection are experimentally validated.The design of the experimental platform is described from three aspects:structure,hardware and software.The effectiveness of capacitor voltage balance control is verified respectively.