Single-phase single-stage current type photovoltaic grid inverter and control method thereof

Abstract

The invention discloses a single-phase single-stage current type photovoltaic grid inverter and a control method thereof, the single-phase single-stage current type photovoltaic grid inverter is composed of a direct current (DC) side capacitor C, a current transforming module and an output filter; the DC side capacitor C is connected to a photovoltaic battery; the current transforming module is composed of a direct current inductance L and five reverse blocking power switches, namely SWL(Safe Working Load), SWP1, SWp(Safe Working Pressure)2, SWn(Switching Network)1and SWn2, respectively, the output filter is formed by connecting a capacitor Cf (Cross fire) and an inductance Lf (Low frequency), the capacitor Cf is connected to two output ends of the current transforming module. According to the invention, the single-phase single-stage current type photovoltaic grid inverter is free of a transformer, with a boosting function, through the least power inversion stage and the smallest passive element parameter.

Description

technical field [0001] The invention belongs to the field of photovoltaic grid-connected power generation, and relates to a single-phase single-stage current-type photovoltaic grid-connected inverter and a control method thereof. Background technique [0002] With the acceleration of my country's urbanization process, the increase in total energy consumption and the backward energy consumption structure lead to increasingly serious problems of energy supply and environmental pollution in the process of urbanization. Urban residential areas are high-density areas of energy consumption and environmental pollution, and their energy and environmental conditions are directly related to the success or failure of urbanization. Large-scale development of green energy is an important way to alleviate the urban energy crisis and reduce environmental pollution. Photovoltaic grid-connected power generation technology is an important development direction in the field of green energy in...

AI Technical Summary

Problems solved by technology

Existing single-phase photovoltaic grid-connected inverters mainly include transformerless voltage-type grid-connected inverters, single-stage voltage-type inverters and current-source inverters based on step-up transformer structures, but these solutions are not widely used in urban residential areas. It is difficult to apply and promote in photovoltaic systems, the main reasons are: 1) Transformerless voltage grid-connected inverter is the most commonly used topology in photovoltaic systems, but it can only work when the DC voltage is constant and higher than the peak voltage of the grid , the photovoltaic system generally adopts a two-stage or multi-stage circuit topology, which makes the circuit structure complex, low reliability, and power loss increase; 2) using multiple photovoltaic cells in series to obtain a large enough DC voltage can realize transformerless single-stage power conversion structure, but the system has safety issues such as complex insulation design and difficult control of leakage current; 3) The single-stage voltage inverter based on the step-up transformer can achieve electrical isolation, but the introduction of the transformer will increase the size of the system and reduce the cost. 4) The voltage-type inverter based on the Z-source network has the function of single-stage step-up and grid-connected power generation, but the main circuit contains many passive components, which makes the structure of the inverter complex and its reliability difficult to guarantee; 5) The traditional current-source inverter can also realize single-stage grid-connected power generation, and has strong short-circuit protection capability and flexible capacity expansion, but the DC side needs to be connected in series with a large inductor, which makes the system efficiency, volume and cost difficult to meet urban living District photovoltaic system requirements

Therefore, there is still no ideal and mature solution for grid-connected inverters suitable for photovoltaic systems in urban residential areas.

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