Research On Optimized Control Strategy Of Active Three Level Inverter Based On DSP

With the rapid transformation of Chinese industrial system,equipment with low efficiency and serious pollution can't meet the requirements of industrial and life products.Therefore,there is an urgent need for high-voltage and high-power inverters that can convert unstable DC power into high-quality AC power.The diode-clamped three-level inverter has become one of the research hotspots in the field of high-voltage and large-capacity power conversion because of its advantages of less output harmonic content,lower switching frequency and higher withstand voltage level.In addition,the rapid development of high-performance digital signal processors makes DSP-based digitalization of inverter systems to be a mainstream for future development.This thesis mainly studies the diode clamped three-level inverter SVPWM control,midpoint potential balance control,and inverter system implementation.Firstly,this thesis mainly discusses the application background of three-level inverters.Furthermore,the development and research status of various topological structures,control algorithms and midpoint potential imbalances are analyzed.This thesis takes a diode clamped three-level inverter as the research object,then analyzing its topological structure and working principle and mathematical modeling.Secondly,this thesis introduces the traditional SVPWM control algorithm of three-level inverters,and proposes an optimized three-level inverter SVPWM control algorithm which can solve the problems of traditional algorithms in vectorization and digital implementation in combination with the two-level SVPWM control algorithm.The optimized SVPWM control algorithm is based on a new quadrilateral sector division,which reduces the complexity of sector determination and does not have the problem of sector overlap.The reference voltage vector is then subjected to a three-level to two-level coordinate transformation,a new method for synthesizing the reference voltage vector under the sector division is derived,and the action time of the basic voltage vector is calculated.Because new sector divisions and traditional sector divisions overlap in small areas but do not correspond to each other,new switching sequences are designed.This thesis also analyzes the principle of the midpoint potential imbalance in the diode-clamped three-level inverter,and proposes an optimal control method for the problems that the traditional midpoint potential balance control method can easily introduce new interference.The optimized midpoint potential balance control method divides the midpoint voltage more precisely,and then proposes a more ideal time compensation method based on the role of small vectors.Finally,using MATLAB/Simulink to build the corresponding simulation model and verify the algorithm based on above analysis.Then the hardware design of 15 KW three-level inverter prototype with the control core of TMS320F28335 DSP is completed,and the control software based on the optimized control strategy is written in C language on the CCS3.3 software platform.Through comprehensive debugging on experimental prototype,the experimental waveform is consistent with theoretical analysis and simulation conclusion,indicating that the optimized three-level inverter control strategy is feasible.