Restraining method of inverter voltage feed-forward direct-current components and control method for inverter

Abstract

The invention provides a restraining method of inverter voltage feed-forward direct-current components. The restraining method includes: sampling three-phase power grid voltage signals ua, ub and uc; subjecting the three-phase power grid voltage signals to Clark transformation and Park transformation to obtain an active component ud and a reactive component uq after coordinate transformation; dephasing corresponding relation of the active component and the reactive component by 90 degrees and performing sum and difference calculation to obtain an active component control instruction and a reactive component control instruction respectively; and finally eliminating direct-current components of the reactive component control instruction and the active component control instruction completely. The invention further provides a control method for an inverter using the restraining method of the inverter voltage feed-forward direct-current components. The restraining method of the inverter voltage feed-forward direct-current components and the control method for the inverter have the advantages that other components serving as feed-forward control instructions are overlaid on controlled quantity after current goes through a PI (proportional integral) regulator, processing is quick while direct components output by the inverter can be eliminated once thoroughly.

Description

technical field [0001] The invention relates to a method for suppressing inverter voltage feed-forward DC components, and also relates to an inverter control method for eliminating the DC components output by the inverter. Background technique [0002] At present, the control method commonly used by photovoltaic grid-connected inverters is the method of current inner loop plus grid voltage feed-forward. The grid voltage feed-forward control command is obtained as follows: first detect the three-phase grid voltage signal, and then convert the three-phase grid voltage signal through d-q coordinate transformation. The phase-to-grid voltage signal is converted into a 2-phase signal in the rotating coordinate system as a grid voltage feed-forward control command to enhance the inverter's ability to resist grid voltage disturbances. However, in the actual operation of photovoltaic grid-connected inverters, due to the influence of factors such as grid voltage asymmetry, the operati...

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Problems solved by technology

[0008] The shortcomings of the above four methods are mainly: the first method of detecting the inductor current combined with the modulation method needs to increase the hardware circuit, and it cannot fundamentally eliminate the DC component brought by the grid voltage detection link from the source; the second method statically eliminates the DC component Although the method is simple, the processing speed is fast, and the burden of the digital processor is light, it cannot track the change of the DC component; the third average method needs at least one power frequency cycle, and at least one power frequency cycle must be stored in the software The grid voltage coordinate transformation data, when the grid frequency is disturbed, the sampling data will have singular points, which will increase the difficulty of software processing; the fourth method uses a digital low-pass filter to filter out the negative sequence component and Harmonic components, the feedforward control command only contains the components of the grid voltage fundamental positive sequence component coordinate transformation, the ability of the inverter to resist grid voltage disturbances will be reduced, and the digital low-pass filter needs to obtain an ideal filter performance index As a result, typically 5 power frequency cycles are required

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