Svpwm Synchronized Modulation Strategy For Vector Control System Under Low Switching Frequency

In recent years,the development of rail transit technology in China is very rapid.In the traction drive inverters,in order to reduce the switching loss of the inverters and avoid serious fever,the highest switching frequency of power devices is usually only a few hundred hertz,at which time the output harmonics of the inverters are more serious.The harmonic suppression effect of SVPWM synchronous modulation strategy is remarkable,and it has good flexibility in practical application,which can meet the requirements of traction motor running in the full speed range.Therefore,it is of practical engineering significance to study how SVPWM synchronous modulation strategy is applied to vector control system.Firstly,the principles of SVPWM asynchronous modulation strategy and synchronous modulation strategy are briefly introduced.Secondly,aimin g at the problem that the SVPWM synchronous modulation strategy is compatible with the rotor field orientation process in the vector control system of three-phase asynchronous motor,an angle instruction correction method is studied,and then a specific method for calculating the pulse occurrence comparison value and dividing the sampling sector is given.On this basis,a set of multi-mode SVPWM modulation strategy is designedr,and the smooth switching of each mode is completed in the full speed range.A complete SVPWM synchronous modulation strategy implementation scheme based on vector control is constructed.Using 3kW and 3.9MW asynchronous motors as simulation objects,the basic functions of the scheme are simulated and verified,and the line voltage WTHD is simulated and analyzed.Finally,because the experimental conditions of MW power level are not easy to obtain,a small power experiment has been completed on a 3 kW experimental prototype.In theory,different power levels do not affect the judgment of whether the scheme is correct an d feasible.The results show that the proposed vector control multi-mode SVPWM modulation strategy can effectively reduce the output harmonics of the inverters under low switching frequencies,and smoothly switch between different modulation modes.The speed control performance of the vector control system based on this scheme is good.