A parabolic current control based digital current control strategy for high switching frequency voltage source inverters

Since parabolic current control has fast transient response and high control precision with constant switching frequency, it is an attractive current control strategy for voltage source inverters. The employment of parabolic current control delivers great performance on current waveform control or voltage waveform control. The implementation of parabolic current control usually requires high speed digital-to-analog converters (DACs) to generate a pair of parabolic carriers as the control band. With increases in switching frequency, this requirement becomes more critical because the speed of DAC limits the update rates of the parabolic carriers. This impacts the smoothness and punctuality of the parabolic control band. To solve this issue, a parabolic current control based digital current control strategy is proposed in this paper. The proposed method uses the sensed current of the output inductor to calculate the next duty-cycle. To improve the transient response speed, a duty-cycle adjustment is presented. The performance of the proposed digital control method is verified in simulation.