Research on variable frequency system with three-level topology and SVPWM control

Working principle of three-level topology and modulation algorithm of space vector pulse width modulation (SVPWM) has been analyzed. And a mathematical expression of the reference voltage has been deduced. Changing the output voltage and frequency synchronously has been realized by changing the dwell time of each vector. And the V/F control demand of electric motor is achieved. In addition, the balancing control strategy of capacitor neutral point voltage balance is presented based on the proposed SVPWM algorithm by adjusting the dwell time of small vector. Finally, the whole system simulation model has been built under the environment of Matlab. The theoretical derivations and control strategies have been verified by simulations. Simulation results show that there are many advantages by using three-level topology with SVPWM control scheme such as high utilization of DC voltage, low harmonics of output voltage, the constant V/f control strategy has been obtained. An important reference value is offered for digital realization of VVVF system in this paper.