High-voltage direct current transmission type grid-tied photovoltaic power generation system

Abstract

The invention discloses a high-voltage direct current transmission type grid-tied photovoltaic power generation system, which comprises more than one photovoltaic direct current booster station, a high-voltage direct current transmission line, a third-level DC / AC converter, a transformer and a high-voltage alternating current grid, the photovoltaic direct current booster stations are connected with the input end of the third-level DC / AC converter via the high-voltage direct current transmission line, and the output end of the third-level DC / AC converter is connected with the high-voltage alternating current grid via the transformer. The high-voltage direct current transmission type grid-tied photovoltaic power generation system has the advantages of simple and compact structure, low cost, convenience in installing and use, high efficiency, wide application range and the like.

Description

technical field [0001] The invention mainly relates to the field of photovoltaic power generation equipment, in particular to a high-voltage direct current transmission type grid-connected photovoltaic power generation system. Background technique [0002] With the continuous aggravation of the energy crisis and the increasingly serious climate and environmental problems, the development and utilization of new energy sources is imminent. The earthquake in Japan triggered a serious leak of nuclear radiation in Fukushima, which once again caused the world to reflect on the safety of nuclear power. Germany will shut down its last nuclear power plant in 2022; China has also re-assessed the safety of its planned new nuclear power plant. [0003] Followed by photovoltaic power generation, wind power and other renewable energy has received widespread global attention. In March 2009, "Implementation Opinions on Accelerating the Application of Solar Photovoltaic Buildings" and "Inte...

AI Technical Summary

Problems solved by technology

Since the existing power system mostly uses AC transmission, and photovoltaic power generation produces direct current, it is necessary to convert the direct current generated by photovoltaic power generation into alternating current through a converter. , resulting in large-scale photovoltaic power plants with a large area and low DC system voltage level (the maximum open circuit voltage is below 1000V, and the long-term working voltage is around 700V), while large-scale photovoltaic power plants mostly adopt centralized grid-connected methods (mostly 1MW is used as a photovoltaic power generation unit), which leads to the disadvantage of large DC loss in existing large-scale photovoltaic power plants

Affected by the DC voltage of the photovoltaic power generation system, the AC output voltage of the existing photovoltaic grid-connected inverters is mostly 270V and 315V, and the large-scale photovoltaic power station mostly transmits electric energy through the transmission network with a voltage level of 35kV and above, resulting in the need to go through two stages The grid-connected power transmission of the photovoltaic grid-connected inverter can only be completed in the step-up step, and the step-up transformer in each step-up step will generate losses, which reduces the overall efficiency of the photovoltaic power generation system; since the installed capacity of large-scale photovoltaic power plants is mostly above 10MW , so the same photovoltaic power station needs to use dozens or even hundreds of photovoltaic grid-connected inverters in parallel, which increases the difficulty of power dispatching, and photovoltaic grid-connected inverters are power electronic devices, which will cause certain harmonic interference to the grid. Parallel connection of multiple inverters will exacerbate the harm of harmonic pollution and increase the cost of harmonic control; at the same time, since large-scale photovoltaic power plants in China are mostly built in the northwest desert and Gobi areas with rich sunlight resources, they are far away from grid-connected points, and are generally far away from the site. The high-voltage transmission network is far away (mostly dozens to hundreds of kilometers), and special high-voltage overhead transmission lines need to be built, and the cost of additional construction of transmission lines is relatively high

Moreover, the existing grid-connected photovoltaic power plants on the transmission side are limited by the withstand voltage capability of photovoltaic cell components (maximum withstand voltage 1000V), and the DC voltage level of the system is mostly below 1kV. After the transformer, it is connected to the 10kV AC busbar, and then connected to the 35kV and above transmission network through a step-up transformer

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