Research On Inverter Control Strategy Based On Line Voltage Modulation

At present, Pulse width modulation technology is the main inverter control strategy in inverter technology system. According to different performance indicators to choose the op-timum pulse width control strategy is a technical problem. In this thesis, the theoretical analy-sis has been done for the general performance of the control strategy, put forward a new con-trol strategy based on line voltage (hereinafter referred to as LSPWM) pulse width modula-tion, and has carried on the simulation and experiment analysis of actual system.Firstly, in this thesis, the principle of sine voltage SPWM modulation technology and harmonic characteristic and four kinds of implementation method are introduced, sampling method for the optimal results show that the symmetry rules is the best which computer the most easily to implement. Widely applied in recent years is also introduced in this thesis, the working principle of space voltage vector SVPWM control technology, the specific imple-mentation method, and the switching sequence, the length of each voltage vector, the SVPWM are analyzed.Secondly, Aiming at dc voltage utilization rate of SPWM is low, Actual system switching frequency is higher, the total harmonic distortion rate is bigger, SVPWM vector sector high time complexity and low harmonics, this thesis presents a new method based on line voltage modulation, effectively reduce the system output waveform harmonic, switching frequency and switching loss, improve the utilization rate of dc voltage, and successfully applied to asynchronous motor, the output of the stator voltage, stator current is much better than that of the SVPWM control strategy.Finally, in this thesis, on the basis of previous work, the conventional SPWM and SVPWM and LSPWM modulation strategies are analyzed in comparison from utilization rate of dc voltage, the inverter output voltage, the motor voltage and moter current, points out the connection between them, concluded LSPWM actually is applying SVPWM switching strat-egy to SPWM modulation, so as to improve the utilization rate of dc voltage, absorbed the advantages of low total harmonic distortion rate of SPWM than SVPWM at same switch fre-quency. Theory analysis and simulation results and practical system based on DSP show that under the same switching frequency, LSPWM both applied to the inverter power supply and used in the asynchronous motor, superior than SPWM and SVPWM, and LSPWM under the condition of the lower switching frequency can reach the output effect of SPWM and SVPWM of high switch frequency.