ANPC Three-level Inverter SSVPWM Strategy

Compared with the Neutral point clamped(NPC)three-level topology,the Active neutral point clamped(ANPC)three-level structure can optimize the loss distribution of switching devices.In the high power transmission system application advantage is more obvious.In order to reduce the switching loss,the high power transmission system usually operates at a lower switching frequency.In this case,the multi-mode segmented modulation strategy is used to optimize the harmonics.Among them,Synchronous space vector pulse width modulation(SSVPWM)is easier to realize online modulation than other synchronous modulation strategies,which gradually becomes a research focus.This paper takes the modulation strategy of ANPC three-level inverter as the research object,and studies the realization of multi-mode SSVPWM of ANPC three-level inverter and the switching strategy between different pulse numbers.Firstly,the structure and principle of ANPC three-level inverter are briefly described,and the sampling point distribution,sequence design and time calculation method of SSVPWM strategy are discussed.In order to realize the loss balance of the ANPC three-level inverter in multi-period,the mathematical model of the loss calculation of the main switching tube and diode of the power device is designed.With the loss balance of the switching device as the constraint,the relationship between the commutating mode and the loss distribution of the ANPC three-level inverter is deeply studied by combining SSVPWM strategy.In this paper,a commutation mode is presented to realize loss balance in multiple cycles by alternating commutationSecondly,based on stator flux continuity,this paper proposes an ANPC three-level multi-mode SSVPWM switching strategy based on pulse insertion by reconstructing stator flux tracks in different modes.Due to the switching impact phenomenon of different sampling points between different pulse numbers in multi-mode SSVPWM strategy of ANPC three-level inverter,the proposed strategy in this paper combines the characteristics of SSVPWM algorithm to obtain stator flux vector deviation online and select ANPC redundant zero state at the switching time.Finally,the flux trajectory is modified to compensate the deviation by inserting switch state.To achieve a smooth transition between different modes.Finally,a simulation model was built in MATLAB/Simulink to simulate the ANPC three-level multi-mode SSVPWM and its switching strategy.At the same time,the switching strategy was tested on the ANPC three-level traction platform.The effectiveness of the proposed switching strategy was verified by simulation and experiment.