Photovoltaic parallel inverter system having shared capacitor topology

Abstract

Provided is a photovoltaic parallel inverter system having shared capacitor topology. The system comprises a plurality of paths of photovoltaic grid-connected inverter units. Each path of photovoltaic grid-connected inverter unit is connected in series with an independent AC output LC filter unit to form a branch; the plurality of branches are connected in parallel, and the output ends thereof are connected with a shared capacitor unit; the output end of the shared capacitor unit is connected with a power grid; and the LC filter output by each branch and a filter capacitor of the shared capacitor unit and an equivalent inductor at the power grid side form an LCCL filter structure. Since the capacitor of the shared capacitor unit is connected in parallel with the filter capacitor of each branch, the system, on the whole, is still an LCL filter structure; the product of the inductance and capacitance of the AC output LC filter unit is equal to the product of the inductance at the power grid side and the capacitance of the shared capacitor unit, that is, the product of the inductance and the capacitance at the inverter side is equal to the product of the inductance and the capacitance at the power grid side; and the resonant frequency of the LCL filter structure does not change with the number of the branches.

Description

technical field [0001] The invention relates to the technical field of photovoltaic parallel inverter systems, in particular to a photovoltaic parallel inverter system with shared capacitor topology. Background technique [0002] At present, the replacement of traditional fossil energy by renewable energy is becoming the main trend of world energy development. In order to solve the needs of economic development and the resulting environmental problems, the installed capacity of domestic photovoltaic power plants has developed rapidly in recent years. Especially in northwestern provinces, large-scale photovoltaic power plants have become the mainstream of development. With the continuous increase of the capacity of photovoltaic power plants, in order to reduce the cost of photovoltaic power generation, the capacity of inverters has increased accordingly, and modular parallel single-unit and multi-unit parallel inverter systems have become a trend of technological development...

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Problems solved by technology

[0004] In order to solve the above-mentioned problems in the prior art, the present invention provides a photovoltaic parallel inverter system with shared capacitor topology, which solves the problem of parallel inverters with multiple (module) machines in the prior art as the number of parallel machines (modules) increases. The equivalent parameters of the LCL filter of the inverter system change, resulting in the problem that the system resonant frequency gradually decreases

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