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Neutral point clamped non-isolated photovoltaic grid-connected inverter

A non-isolation and inverter technology, applied in photovoltaic power generation, single-network parallel feed arrangement, AC power input conversion to DC power output, etc., can solve problems affecting system efficiency and low conversion efficiency, and eliminate leakage current , Efficiency improvement, reducing switching loss and electromagnetic interference

Inactive Publication Date: 2011-08-24
NANJING UNIV OF AERONAUTICS & ASTRONAUTICS
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Problems solved by technology

However, compared with unipolar SPWM, bipolar SPWM has obvious disadvantages: switching loss and AC filter inductance loss are twice that of unipolar SPWM, which affects the efficiency of the system
The literature "Ma Lin, Jin Xinmin. Analysis of Common Mode Leakage Current in Photovoltaic Grid-connected System with Transformerless Structure, Journal of Solar Energy Sinica, 2009, vol.30(7): Page(s): 883-888." In the isolated grid-connected inverter topology, by adding two switching tubes, two diodes and two voltage dividing capacitors, the potential of the freewheeling circuit in the freewheeling stage is clamped at half of the input voltage of the photovoltaic cell, but its current path always passes through Four switching devices, so the conversion efficiency is low

Method used

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Embodiment Construction

[0043] In order to make the technical means, creative features, goals and effects achieved by the present invention easy to understand, the present invention will be further described below in conjunction with specific illustrations.

[0044] attached figure 1 It is the first embodiment of the circuit topology of the neutral point clamped non-isolated photovoltaic grid-connected inverter, including the input voltage dividing capacitor branch 1, the neutral point clamping branch 2, the full bridge switch unit 3 and the grid filter branch 4; Among them, the input voltage dividing capacitor branch 1, the midpoint clamping branch 2, the full bridge switch unit 3, and the network filter branch 4 are connected in sequence;

[0045] The input voltage dividing capacitor branch 1 consists of a first voltage dividing capacitor C dc1 , the second voltage dividing capacitor C dc2 ;

[0046] The midpoint clamping branch 2 includes the seventh power switch tube S 7 , the eighth power sw...

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Abstract

The invention discloses a neutral point clamped non-isolated photovoltaic grid-connected inverter, belonging to the field of power electronic converters. The inverter is constituted by an input divided capacitor branch, a neutral point clamped branch, a full-bridge switch unit and a network accessing filter branch. The inverter is characterized in that two switching tubes and an input divided capacitor are added to form a neutral point clamped branch on the basis of a basic full-bridge circuit, so that the potential of a follow current return circuit is half of a battery voltage at a follow current stage, thus eliminating leakage current of the non-isolated grid-connected inverter. Relative to the topology of an existing non-isolated photovoltaic grid-connected inverter, the inverter provided by the invention has the advantages that the maximum voltage stress of parts of power switching tubes and the voltage regulation factors of all power switching tubes are half of that of the battery voltage; electromagnetic interference and switching loss are reduced; and the inverter is applied to transformer-free isolated photovoltaic grid-connected occasions.

Description

technical field [0001] The invention relates to a neutral-point clamped non-isolated photovoltaic grid-connected inverter, which belongs to the technical field of power electronic converters, and in particular relates to photovoltaic grid-connected power generation. Background technique [0002] Non-isolated photovoltaic grid-connected inverters have the absolute advantages of high efficiency, small size, light weight and low cost. However, due to the existence of the parasitic capacitance of the photovoltaic 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 resulting leakage current may exceed the allowable range. The generation of high-frequency leakage current will also bring conduction and radiation interference, increase the harmonics and loss of the network current, and even endanger the safety of equipment and personnel. [00...

Claims

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Application Information

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IPC IPC(8): H02J3/38H02M7/487H02M7/5387
CPCH02M2001/123Y02E10/56Y02E10/563H02M7/5388H02M1/123
Inventor 张犁邢岩冯兰兰
Owner NANJING UNIV OF AERONAUTICS & ASTRONAUTICS
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