Multi-level photovoltaic grid-connected inverter with isolation transformer

Abstract

The invention discloses a multi-level photovoltaic grid-connected inverter with an isolation transformer. The multi-level photovoltaic grid-connected inverter comprises a power source, a preposed DC / DC converter, a high-frequency SPWM (sinusoidal pulse width modulation) modulation circuit, a high-frequency isolation transformer, a rectification unit, a filtering and inverting unit, a first capacitor and a second capacitor, wherein the power source is connected with the first capacitor in parallel; the preposed DC / DC converter is connected with the first capacitor in parallel and is connected with the second capacitor in parallel; the high-frequency SPWM modulation circuit is connected with the second capacitor in parallel, and is connected with the rectification unit through the high-frequency isolation transformer; the rectification unit is connected with the filtering and inverting unit; and the high-frequency isolation transformer is formed by a first inductor and a second inductor in coupling. With the adoption of the multi-level photovoltaic grid-connected inverter with the isolation transformer, the loss of switch devices is reduced as far as possible; and high conversion efficiency is achieved.

Description

technical field [0001] The invention relates to the technical field of power conversion, in particular to a multi-level photovoltaic grid-connected inverter with an isolation transformer. Background technique [0002] The voltage on the primary side of the high-frequency transformer of the traditional high-frequency isolated photovoltaic grid-connected inverter is constant for a certain period of time. After modulation, the secondary side of the transformer outputs a pulse with a fixed amplitude, and then transmits the energy to the power grid. Since the grid voltage changes sinusoidally, in order to ensure that the energy of the inverter can be transmitted to the grid during the entire grid cycle, the voltage pulse amplitude output by the secondary side of the transformer must be greater than the peak value of the grid. In fact, due to the constant input voltage of the primary side of the transformer, the pulse amplitude output by the secondary side is kept above the peak ...

AI Technical Summary

Problems solved by technology

Therefore, in most of the mains cycle, high pulses will cause loss of filter devices, rectifier device losses, and also cause unnecessary loss of transformer primary modulation devices

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