Non-switching loss type full-bridge non-isolated photovoltaic grid-connected inverter and switching control sequence

Abstract

The invention discloses a non-isolated photovoltaic grid-connected inverter without switching loss and a switch control sequence, wherein the inverter includes a voltage dividing capacitor branch, a high-frequency main switch unit, a resonant network and a low-frequency commutation switch unit. By adding two sets of resonant networks composed of fully-controlled switches, resonant capacitors and resonant inductors, and auxiliary freewheeling clamp diodes to form a zero-current conversion branch, and with the above-mentioned switch control sequence, the fifth power switch tube S can be realized. 5 and the sixth power switch S 6 The zero-current turn-on and zero-current turn-off conditions of the fifth auxiliary switch tube S a5 and the sixth auxiliary switch S a6 zero-current turn-on and zero-current turn-off conditions, and eliminates low-frequency commutation switch cell diode D 1 ~D 4 reverse recovery and other issues, and ensure that the common-mode voltage of the inverter is always at half of the battery voltage during power transmission, resonance phase and freewheeling phase to eliminate leakage current, so that a non-isolated grid-connected inverter can be realized high frequency and miniaturization.

Description

technical field [0001] The invention relates to the technical field of high-efficiency grid-connected inverter topology, in particular to a full-bridge non-isolated photovoltaic grid-connected inverter without switching loss. Background technique [0002] The non-isolated photovoltaic grid-connected inverter has a simple circuit structure and high conversion efficiency and has been widely used in the industry. Such as figure 1 As shown, the existing technologies all work in the hard switching mode, and the ideal efficiency can only be achieved by operating at a relatively low switching frequency (10-20kHz), and relatively large filter inductors and filter capacitors are required, which increases and The volume weight of the grid inverter increases the cost. [0003] After research, it is found that the main factor limiting the increase of switching frequency of non-isolated grid-connected inverters is the switching loss of high-frequency switches. With the increase of swit...

AI Technical Summary

Problems solved by technology

The existing technology proposes a non-isolated grid-connected inverter soft switching solution for this defect, but there is a problem in the prior art that the resonant capacitor voltage cannot be reliably clamped at a fixed voltage value, so that the peak value of the resonant inductor current in the resonant circuit may be low In the case of high-frequency main switch conduction current, it loses the opportunity of zero current shutdown

[0005] In addition, the turn-on process of the high-frequency main switch is still a hard switch, the turn-off process of the high-frequency auxiliary switch is also a hard switch, and the diode of the low-frequency reversing switch unit still has a reverse recovery problem

Images