Suppression method of current zero-crossing distortion of three-phase double-buck grid-connected inverter

Abstract

The invention discloses a method for suppressing the current zero-crossing distortion of a three-phase double-buck grid-connected inverter. By collecting the grid voltage, according to the phase angle θ of the grid voltage obtained by the software phase-locked loop, judge the critical point at which the inductance current on the inverter side of the three-phase dual-buck grid-connected inverter controlled by half-period SPWM enters the discontinuous zone, The duty cycle function compensated at this time is obtained by calculation, and superimposed on the original modulation wave, so that the current ripple in the intermittent interval of the inductor current on the inverter side gradually decreases, and the average value of the inductor current is before and after zero crossing. The discontinuous interval tends to be sinusoidal, and the zero-crossing distortion of the current is effectively eliminated without adding additional devices and ensuring system stability.

Description

Technical field [0001] The invention belongs to the technical field of electric energy conversion, and particularly relates to a method for suppressing current zero-crossing distortion of a three-phase dual-buck grid-connected inverter. Background technique [0002] In today’s society, there is a large demand for energy, pollution-free, renewable new energy power generation and electric energy recovery and utilization have received extensive attention, and three-phase grid-connected inverters are important equipment for new energy generation and electric energy recovery and utilization. The research on key technologies is a hot spot in the field of power electronics, and the waveform quality of grid-connected current is particularly important. The traditional three-phase bridge inverter has a simple structure and high efficiency, but it has the problem of through-through of the bridge arm power tube, and its reliability is low. In order to avoid the through problem, it is necess...

AI Technical Summary

Problems solved by technology

The full-cycle control is that the two power transistors of each phase bridge arm are turned on complementary, and each filter inductor on the bridge arm side flows a current of a power frequency cycle. Due to the double-buck structure, additional losses will be brought, resulting in low efficiency. On the half-cycle control bridge arm side, each filter inductor only flows the current of half the power frequency cycle, which reduces the loss, but it will bring the problem of zero-crossing distortion of the grid-connected current.

[0004] Under half-cycle control, the two power tubes of each phase bridge arm work alternately and switch at the zero-crossing point of the current. At the moment of switching, the ripple direction of the inductor current on the inverter side caused by the switching of the power tube will occur at the zero-crossing point. change, resulting in zero-crossing distortion of the grid-connected current

At present, the method to solve the zero-crossing distortion of the double-buck grid-connected inverter is to adopt the method of multi-channel double-buck grid-connected inverter input parallel connection and output cascading to make the current ripple cancel each other, thereby eliminating the zero-crossing distortion, but this method Only suitable for cascaded topologies with independent input DC sources

Another method is to use the ripple current negative feedback method to perform negative feedback on the ripple component to compensate the pulsation at the current zero crossing, but this method has an impact on the stability of the system, and sometimes additional active damping control is required , increasing the complexity of the control

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