Three-phase photovoltaic inversion device based on transformer cascading technology

Abstract

The invention provides a three-phase photovoltaic inversion device based on the transformer cascading technology. A photovoltaic array is adopted on the direct current side of the inversion device to serve as direct current source input, multiple photovoltaic inversion unit branches are connected to the output end of the photovoltaic array in parallel, the output ends of the photovoltaic inversion unit branches are sequentially connected in series, and the output ends connected in series are directly combined in a medium-voltage power grid. The input end of each photovoltaic inversion unit branch is connected with a bus capacitor in parallel, and the output ends of the bus capacitors are connected with the input end of a photovoltaic inversion unit. The photovoltaic inversion unit is formed by connecting three-phase PWM inverters and transformers in series, the input ends of the three-phase PWM inverters are the input ends of the photovoltaic inversion unit branches, the output ends of the three-phase PWM inverters are connected with primary side windings of the transformers, and secondary side windings of the transformers serve as the output ends of the branches and are in series connection with the output ends of other branches connected in parallel. Compared with traditional phase-shifting transformers, the transformers used in the device have the advantages that the manufacturing process is simplified and the manufacturing cost of a high-power centralized photovoltaic grid-connected inversion system is reduced.

Description

technical field [0001] The invention relates to the technical field of photovoltaic inverters, in particular to a three-phase photovoltaic inverter device based on transformer cascading technology. Background technique [0002] In order to increase the stand-alone capacity of photovoltaic inverters, most high-power grid-connected inverters adopt multi-level methods. The main purpose of adopting multilevel inverter is to realize high voltage output by using low withstand voltage switching devices. Both the cascade method and the multiple superposition method are the main methods to generate multilevel inverters. The cascading method is to take N H bridges (inversion units) with independent DC sources and output voltages of SPWM waves, shift their triangular carrier waves by 2π / N in turn, and directly superimpose the output voltages of the H bridges in series, so that The output voltage becomes a SPWM multi-level ladder wave to achieve the purpose of eliminating carrier harm...

AI Technical Summary

Problems solved by technology

[0005] In order to solve the problems existing in the above-mentioned prior art, the object of the present invention is to provide a three-phase photovoltaic inverter device based on transformer cascading technology, which solves the PID effect of non-isolated cascaded inverter PV components and the common problem of PV components. The problem of mold leakage current overcomes the problem that multiple technologies cannot realize PWM voltage regulation in the application of photovoltaic grid-connected systems, and the problem that the manufacturing process of phase-shifting transformers is not easy to realize, and reduces the cost of high-power centralized photovoltaic grid-connected inverter systems. manufacturing cost

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