Dual active bridge circuit modulation strategy suitable for photovoltaic power generation application

Abstract

The invention discloses a dual active bridge circuit modulation strategy suitable for photovoltaic power generation application . In the premise of ensuring normal operation of a dual active bridge circuit in a high voltage direct grid connected current converter, a modulation strategy for improvement is proposed. The strategy acts on a primary-secondary side H bridge duty ratio and control over the dual active bridge is realized through adjustment of a phase shift angle by a controller. Therefore, the strategy is compatible to a control system. The modulation algorithm can improve the performance of the high voltage direct grid connected current converter, promotes scale application of the high voltage direct grid connected current converter and has positive impetus on development of photovoltaic power generation systems.

Description

technical field [0001] The invention belongs to the technical field of power electronics and photovoltaic power generation, and relates to a dual active bridge circuit modulation strategy suitable for photovoltaic power generation applications. Background technique [0002] At present, most large-scale photovoltaic power generation systems adopt a low-voltage grid-connected structure, and its basic components are DC combiner boxes, inverters and step-up transformers. The output of photovoltaic panels is aggregated through the combiner box, and the output is provided to the inverter. The inverter converts the DC power into AC power, and finally supplies it to the medium-voltage power grid through the power frequency transformer. The schematic diagram of the framework is shown in figure 1 shown. The technology of this mode is mature, but there are still a series of disadvantages in the application. First of all, the working conditions of the inverter are limited by the input...

AI Technical Summary

Problems solved by technology

[0004] Although the structure has obvious advantages, there are still some problems in some working conditions

In photovoltaic power generation applications, the output voltage of photovoltaic panels varies greatly, and a wide range of input voltage will have a great impact on the core link of high-voltage photovoltaic grid-connected, the dual active bridge circuit. The impact mainly comes from several aspects. First The effective value of the current in the circuit will increase, which will affect the loss of the conversion link; secondly, the peak value of the current will increase, which will increase the electrical stress of the device; finally, it will be difficult for the switching device to achieve zero-voltage turn-on, which will increase the loss of the device

On the other hand, in the high-voltage photovoltaic grid-connected converter, it is composed of a large number of power modules, which will bring a large number of parallel communications and calculations. In actual engineering applications, only FPGA control chips that can support parallel communications and calculations can be used. However, it is difficult to process complex algorithms in FPGA, and the time required for algorithm realization is short.

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