Photovoltaic system, control method of turn-off device of photovoltaic system and switch control device

Abstract

The invention discloses a photovoltaic system, a control method of a turn-off device of the photovoltaic system and a switch control device. According to the scheme, after the switch control device ispowered on, the starting time of the turn-off device connected with the switch control device is generated, wherein the generated starting time is longer than the time for tracking the maximum powerpoint of the photovoltaic system; the starting time of the plurality of turn-off devices is different; it is judged whether a control signal is received or not; after the control signal is received and the starting time is passed, the turn-off device at the output end of the photovoltaic module connected with the turn-off device is turned on; and the possibility that the input voltage of the photovoltaic inverter changes suddenly all the time due to the fact that the output voltage of the photovoltaic module reaches an under-voltage protection point is reduced, the influence on the service life of components is reduced, and the stability of a photovoltaic system is improved.

Description

technical field [0001] The invention relates to the field of electric energy conversion, in particular to a control method and a switch control device for a photovoltaic system and its shut-off device. Background technique [0002] In the prior art, in order to meet the requirements of safety regulations, the photovoltaic system includes a shutdown device, a photovoltaic inverter, a signal generator, a detection control module, and multiple photovoltaic modules. The photovoltaic inverter includes a DC-DC (Direct current-Directcurrent , DC-DC) module and DC-AC (Direct current-Alternating current, DC-AC) module, wherein the output terminal of the DC-DC module is connected to the input terminal of the DC-AC module, and the output terminal of the DC-AC module, That is, the output end of the photovoltaic inverter is connected to the grid, and multiple photovoltaic modules are connected in series through the switch control device, and the output ends of the series pass through, su...

AI Technical Summary

Problems solved by technology

[0005] When the shaded M components resume work at the same time and the switch control device connected to them is powered on immediately, the output voltage of the entire string of photovoltaic components is pulled up to V ’ in =V in +M×V m , the bus voltage is pulled up to V ’ out =V ’ in / (1-D), in order to quickly stabilize the bus voltage, the DC-AC module will increase its own output current, thereby stabilizing the bus voltage at V out , because the time for the DC-AC module to stabilize the bus voltage is very short, which is shorter than the time for the DC-DC module to adjust the output voltage of the photovoltaic module to reach the voltage when the output maximum power is reached, therefore, the output voltage of the L+M photovoltaic module is controlled pulled down to V in , that is, the output voltage of each component is V in / (L+M), however, at this time, the output voltage of some photovoltaic modules may be too low to reach the undervoltage protection point, and the shutdown device connected to it is turned off, and the output voltage of photovoltaic modules is also DC-DC The input voltage of the module is reduced, which leads to the reduction of the bus voltage of the DC-AC module, and the instability of the photovoltaic system is introduced.

Moreover, when the photovoltaic modules that reach the undervoltage protection point resume work at the same time, and repeat the above steps, there will always be photovoltaic modules that reach the undervoltage protection point and are turned off, resulting in the system not being able to reach steady-state power generation quickly and affecting the power generation.

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