Three-phase dual-buck grid-connected inverter current zero-crossing distortion inhibition method

Abstract

The present invention discloses a three-phase dual-buck grid-connected inverter current zero-crossing distortion inhibition method. The voltage of a power grid is collected, the critical point of inductive current of the inverter of a three-phase dual-buck grid-connected inverter controlled by half cycle SPWM entering an intermittent region is determined according to the voltage phase angle [Theta] of the power grid obtained through software phase-locked loop, a compensation duty ratio function at present is obtained through calculation and is overlapped into an original modulated wave to allow the current ripple in the intermittent interval of the inductive current of the inverter to be gradually reduced, and the average value of the inductive current tends to sinusoidal variation in the intermittent interval around the zero crossing so as to effectively eliminate the current zero-crossing distortion on the premise without extra adding devices and ensuring the system stability.

Description

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

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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