The Research On Speed Control Of Permanent Magnent Syncronous Based On Three-level Inverter

With the development of power electronics and power transmission,multilevel inverter technology has become a hotspot in the field of high pressure and high precision.Multilevel inverter not only has low voltage requirements for switchgear,but also makes output waveform have better harmonic spectrum due to the increase of the level number.In practical applications,because of the constraints of hardware and control complexity,usually in the pursuit of performance indicators,not the pursuit of excessive level,and the most practical three-level.Therefore,in the middle and high voltage frequency conversion speed regulation and other fields are widely concerned.The topology and modulation methods of multilevel inverters are analyzed and compared.The structure and working principle of T-type three-level inverter are discussed in detail.The space voltage vector pulse width modulation algorithm is studied in detail.Based on the traditional three-level space voltage vector modulation principle,a simple algorithm for three-level 60° coordinate system space voltage vector is analyzed in detail with the aid of a coordinate system.At the same time,the unbalance problem of DC side capacitance voltage of T-type three-level topology is deduced theoretically,and the method of the software combining with hardware to control the neutral point potential is given.Analyzes the structure characteristics of permanent magnet synchronous motor,the mathematic model and the common control method in each coordinate system,and focuses on the vector control principle of pmsm and the speed estimation method based on sliding mode observer;The simulation platform of speed control system based on three-level permanent magnet synchronous motor is built,Each simulation module is constructed according to the algorithm,and the three-level speed control system is simulated and validated.The simulation results show that the space voltage vector modulation algorithm is correct and advantageous under the three-level topology,and the software combined with the hardware control point potential balance algorithm can effectively control the fluctuation of the midpoint voltage.Finally,a three-level inverter permanent Magnet Synchronous motor control system is designed,which includes T-type three-level inverter main circuit,driving fault protection circuit,signal detection circuit and auxiliary power supply.The software program of the control system was written in CCS 6.0 environment,and the experimental platform was studied.