Non-isolated grid-connected inverter and switch control time sequence thereof

Abstract

The invention provides a non-isolated grid-connected inverter and a switch control time sequence thereof. The non-isolated grid-connected inverter comprises a voltage dividing capacitor branch (1), a clamping branch (2) and a full-bridge basic unit (3), wherein the voltage dividing capacitor branch (1) consists of a first voltage dividing capacitor (Cdc1) and a second voltage dividing capacitor (Cdc2), the clamping branch (2) consists of a first power switch pipe (S1) and a second power switch pipe (S2), and the full-bridge basic unit (3) consists of a third power switch pipe (S3), a fourth power switch pipe (S4), a fifth power switch pipe (S5) and a six power switch pipe (S6). The invention adds two controllable switch pipes and voltage dividing capacitors on the basis of a full-bridge circuit for forming a bidirectional clamping branch, is matched with the switch time sequence, and can realize the battery voltage at a half of the follow current loop potential in the follow current stage, so the leakage current of the non-isolated grid-connected inverter is eliminated, the output current only passes through three switch pipes in the power transmission stage is ensured, and the conduction consumption is effectively reduced.

Description

technical field The invention relates to a non-isolated photovoltaic grid-connected inverter, which belongs to the topology of a grid-connected inverter. Background technique Non-isolated photovoltaic grid-connected inverters have the advantages of high efficiency, small size, light weight and low cost. However, due to the existence of the parasitic capacitance of the solar panel to the ground, the switching action of the switching device of the grid-connected inverter may generate a high-frequency time-varying voltage to act on the parasitic capacitance, and the leakage current induced by this may exceed the allowable range. The generation of high-frequency leakage current will bring conduction and radiation interference, increase the harmonics and loss of the incoming current, and even endanger the safety of equipment and personnel. The unipolar SPWM full-bridge grid-connected inverter has excellent differential mode characteristics, such as high utilization rate of inpu...

AI Technical Summary

Problems solved by technology

However, according to the high-frequency common-mode equivalent model of the full-bridge circuit, in order to eliminate the high-frequency common-mode voltage generated by unipolar SPWM modulation, the potential of the freewheeling circuit in the freewheeling stage must be clamped at half of the input voltage of the solar cell, so that Complete elimination of common-mode voltages rather than simply disconnecting the panels from the grid

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