Research On SVPWM Generator For Neutral Point Clamped Three-level Inverter

Space Vector Pulse Width Modulation (SVPWM) is widely used in the control of multi-level converter for its advantages, such as low-content harmonic, low -switching frequency, convenience of digital realization, high voltage utilization and so on. One of the space vectors generation called table-inquire. It is easy to be accepted, but its algorithm is complex and difficult to realize. In order to simplify the algorithm, many new methods are suggested. There are two main methods in this article. One efficient type of improved algorithm is analyzed; this method is based on the simplification of the space–vector diagram of a three-level inverter into that of a two-level inverter by transforming method: base vector and two-level vector. If simplified by the proposed method, all the remaining procedures necessary for the three-level SVPWM are done like conventional two-level inverter and the execution time is greatly reduced. The dc-link neutral-point potential control algorithms are implemented more easily.And the proposed method can be applied to the multi-level inverters above three-level. The other method is based on the coordinate transformation, with m - n coordinate system and the K - L coordinate system separately replaces traditional coordinate system. This method doesn`t need to involve tedious triangular operation and large numbers of computation during the judgment of vector sector and the time of computation vector.This article separately simulate the table-inquire method and the disassembly of reference voltage method with MATLAB software, then educe the concept of "vector generator". This article in detail introduce two kind of vectors generators' feasible plans:"Based on DSP vector generator"and"based on DSP—CPLD vector generator". It is found that "based on DSP—CPLD vector generator" is easy to realize compared with the another plans.This article has built an experiment system based on the three-levels vector generation.An experiment prototype of 1.5KW three-level inverter has been manufactured,which is driven by "based on DSP—CPLD vector generator".we finally got ideal wave in this experiment system.