Control method of t-type three-level three-phase four-leg photovoltaic grid-connected power generation system

Abstract

The invention discloses a novel three-level grid-connected photovoltaic power generation system. The novel three-level grid-connected photovoltaic power generation system mainly comprises a direct current-direct current converter, a direct current-alternating current converter, a photovoltaic array, a filter circuit and a controller. The photovoltaic array and the controller are respectively and electrically connected with the direct current-direct current converter. The output end of the direct current-direct current converter is electrically connected with the input end of the direct current-alternating current converter. The output end of the direct current-alternating current converter is electrically connected with the input end of the filter circuit. Four relays are arranged at the output end of the filter circuit. The filter circuit is respectively and electrically connected with the input ends of the four relays. Diodes of each bridge arm of the system are two fewer than those adopted in the prior art. A four-wire system connecting mode is adopted. The requirement for simultaneous connection of three-phase load and single-phase load of a small power station is met, and the cost of a whole product is also reduced.

Description

Technical field: [0001] The invention belongs to the technical field of power electronics, and in particular relates to a control method for a T-type three-level three-phase four-bridge-arm photovoltaic grid-connected power generation system. Background technique [0002] With the depletion of energy and the increasingly serious environmental pollution, renewable energy has gradually become an important part of human life, which has led to the rapid development of solar photovoltaic grid-connected power generation technology; photovoltaic power generation system is based on the research of solar photovoltaic grid-connected power generation technology It is mainly a renewable energy device that uses a photovoltaic cell array to convert solar energy into electrical energy and stores it in the battery of the system or directly for load use; photovoltaic power generation systems generally include photovoltaic panels, DC-DC conversion devices, DC- There are five parts: AC convers...

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Problems solved by technology

[0003] Traditional inverters are mainly two-level inverters. Although this type of inverter provides enough power, it has the disadvantage of poor stress of the power switch tube due to excessive voltage or current rise; in order to solve these shortcomings, various Research developers have developed three-level inverters. This kind of inverter increases the number of levels output and the number of steps of the output waveform, making the output waveform closer to a sine wave and generating less harmonic content. It also reduces the rise rate of the output voltage, reduces the requirements for the withstand voltage performance of the switching device, and improves the electromagnetic interference characteristics of the inverter; compared with the two-level inverter, in the case of the same output voltage waveform, three The switching frequency required by the level inverter is low, so the switching loss is small and the efficiency is high;

[0004] At present, commercial three-level inverters are mainly diode-clamped three-level inverters. This clamped inverter usually consists of three bridge arms, and each bridge arm is composed of four diodes working together. , which to a certain extent reduces the loss of the switch and improves the working efficiency of the inverter; but for small power stations, it cannot meet the requirements of connecting both three-phase loads and single-phase loads, and there are certain potential safety hazards , so according to the working characteristics of small power stations, it is necessary to study a three-phase four-wire photovoltaic power generation system

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