Simplified overlap-time compensation strategy for three-phase current source inverter based on SVPWM
[Objective]Current source inverter(CSI)is a highly promising power electronic converter.Because of its large inductance connected in series on the DC side,the CSI exhibits a boost characteristic.Moreover,its power circuit can endure a short shoot-through state,providing relatively high reliability.At present,CSI is applied in fields such as photovoltaic power generation and high-power motor drives and is an important equipment for electrical energy conversion.Many characteristics of CSI include duality attributes with the voltage source inverter(VSI).To prevent shoot-through failure,a dead time must be added between complementary drive signals in the VSI.Correspondingly,in the CSI,an overlap region between the complementary drive pulses must be added to provide a freewheeling path.The overlap-time effect of CSI is similar to the dead-time effect of the VSI,which can also increase the output current harmonics.The overlap-time effect must be compensated to improve the quality of output power.Meanwhile,conventional space vector pulse-width modulation(SVPWM)requires a series of complex steps,such as sector determination,time calculation,and allocation.Simplified SVPWM can be applied in VSI to reduce the computational complexity.However,there is limited research on simplified SVPWM for three-phase CSI.If the overlap-time compensation strategy is implemented using conventional SVPWM,the implementation process becomes complex and computationally intensive.[Methods]Therefore,in this paper,the conventional SVPWM implementation method is analyzed for three-phase CSI.Accordingly,a simplified SVPWM for generating saddle-shaped modulation waves is proposed,which can avoid a series of complex steps.Furthermore,the current deviation vector generated by the overlap-time effect is analyzed.A simplified overlap-time compensation strategy based on SVPWM is proposed.[Results]A three-phase CSI simulation model was built in MATLAB/Simulink to verify the proposed simplified overlap-time compensation strategy based on SVPWM.The overlapping area times were set to 3 and 5 μs,respectively.The proposed simplified overlap-time compensation strategy based on SVPWM is enabled at 0.04 s.The output current waveforms before and after the overlap-time compensation are analyzed and compared.The fast Fourier transform results of output currents are presented.As can be seen from the results in this paper,the output current is severely distorted before compensation,and the total harmonic distortions(THDs)of the currents with 3-and 5-μs overlap times are 4.25%and 7.48%,respectively.After the overlap-time compensation,the distortions of the output currents were significantly reduced,and the corresponding THDs were 1.49%and 1.35%,respectively.At the same time,the 5th,7th,11th,and 13th harmonics in output currents are significantly reduced.[Conclusions]Using theoretical analysis and simulation results,this study proved that the proposed simplified overlap-time compensation strategy based on SVPWM can effectively reduce the impact of the overlap time and improve the quality of output currents.Moreover,the proposed method can effectively simplify the implementation process and reduce the computational complexity of the overlap-time compensation strategy.
current source inverterspace vector pulse-width modulationoverlap-time effectsimplified overlap-time compensation
万方数据
维普
