Controlling method for grid-connected photovoltaic system including two-stage voltage inverter

Abstract

The invention provides a controlling method for a grid-connected photovoltaic system including a two-stage voltage inverter. The method comprises: step one, a direct-current-side voltage value and alternating-current-side three-phase voltage and current values of an inverter and an input voltage value of a boosted circuit of the inverter are collected; step two, according to practical measurement data, whether the direct-current-side voltage value of the inverter reaches the 1.1 times of a rated voltage is determined, and an input direct-current voltage of the inverter is controlled correspondingly or an outlet voltage of a photovoltaic array is controlled to be a maximum power point voltage; and step three, on the basis of the practical measurement data, whether a threshold determination system is in a normal or faulted state is calculated and determined; if the threshold determination system is in a normal state, dual-loop controlling is carried out on the inverter by ways of voltage outer loop controlling and current inner loop controlling and if the threshold determination system is in a faulted state, positive-sequence and negative-sequence controlling is carried out on the inverter. Under the circumstance that the system works normally, the photovoltaic array can work at a maximum power point; and the direct-current-side voltage of the inverter can be stabilized and a certain reactive power is sent based on the drop degree of the alternating-current-side voltage of the inverter, and thus the grid-side voltage is supported.

Description

technical field [0001] The invention relates to a control method for a grid-connected photovoltaic power generation system, in particular to a control method suitable for a grid-connected photovoltaic power generation system including a two-stage voltage inverter. Background technique [0002] Photovoltaic power generation is divided into two working modes: off-grid and grid-connected. In recent years, photovoltaic power generation and grid-connected technologies have developed rapidly, and solar energy is developing from a "supplementary energy source" to one of the next-generation new "alternative energy sources". Photovoltaic power generation adopts power electronic equipment with extremely fast dynamic process to achieve grid connection, which is completely different from the dynamic characteristics of traditional synchronous machines, so its control method is different from that of traditional synchronous machines. In the actual application process, when the photovolta...

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Problems solved by technology

In the actual application process, when the photovoltaic power station is connected to the grid, the corresponding grid system becomes a multi-power system, which will affect the power flow of the system, and the power flow control is difficult; when the inverter outputs a light load, the photovoltaic power station is input to the The harmonic content in the power grid system will increase significantly; when the output side of the inverter fails, the voltage on the AC side of the inverter will decrease, which will reduce the utilization rate of the power switching device, and will generate unbalanced power, affecting photovoltaic power generation. normal operation of the array

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