Study On Loss Of ANPC Three-Level Grid-Connected Converter

The Active Neutral Point Clamped (ANPC) three-level converter is studied in this thesis. The main work includes the analysis on distribution of semiconductor losses, electro-thermal, low loss control and the low loss design of LCL filter. The main contents of this thesis are as follows:(1) A model based on parasitic parameters (Miller capacitance and parasitic inductance) was proposed in this thesis. The mathematical expression of Miller capacitance and transfer characteristic was established by fitting method respectively, and the voltage and current mathematical expression in this model are derived. The voltage and current oscillation behind turn-off are analyzed by means of an equivalent physical circuit.(2) The characteristic of various modulation strategies of ANPC three-level converter are analyzed. We focus on the distribution of semiconductor losses among the ANPC devices, and the semiconductor junction model was established. One modulation strategy with low loss was chosen to reduce the switching loss and the junction temperature.(3) The LCL filter mathematic model was establishedf the double current loops control strategy was selected to reduce the influence of grid voltage through the voltage feed forward control. The loss model of filter inductor and capacity of LCL filter was proposed.(4) The control strategies of this thesis are carried on under the MATLAB/Simulink simulation environment. A prototype of 5kW ANPC three-level converter has been developed, and the design method of part hardware has been provided. The correctness and feasibility of control strategies ware verified through the simulation and experimental results.The work is supported by the Natural Science Foundation of Anhui Province (1308085ME81), Natural science foundation of colleges and universities of Anhui Province (KJ2013A011) and National Natural Science Foundation of China (51307002).