Turn-off circuit for photovoltaic system and control method thereof

Abstract

The invention relates to a turn-off circuit for a photovoltaic system and a control method thereof, the turn-off circuit comprises a photovoltaic string PV, the positive electrode of the photovoltaic string PV is connected with the positive electrode of an inverter through a cut-off switch K1, the negative electrode of the photovoltaic string PV is connected with the negative electrode of the inverter through a cut-off switch K2, the cut-off switch K1 and the cut-off switch K2 are used for controlling the on-off of the photovoltaic string PV, and the photovoltaic string PV is connected with a short circuit module in parallel. According to the short-circuit module, when the cut-off switch on the bus executes a cut-off action, the short-circuit module enables the photovoltaic string to be short-circuited, due to the external characteristics of the photovoltaic module, the output of the photovoltaic panel is reduced, the bus switch acts under relatively low working voltage and working current, the arc discharge phenomenon during switch action is avoided, and the service life of the photovoltaic module is prolonged. And the diodes connected in series in the short-circuit module can prevent uncontrollable short-circuit current from being generated when the photovoltaic group string is reversely connected, so that compared with the original turn-off mode of only using a semiconductor switch, the switch-on loss is obviously reduced, and additional heat dissipation measures do not need to be added to the switch.

Description

technical field [0001] The invention relates to the technical field of photovoltaic power generation, in particular to a shutdown circuit for a photovoltaic system and a control method thereof. Background technique [0002] At present, the proportion of photovoltaic power generation technology in new energy is getting higher and higher. With the continuous increase of photovoltaic installed capacity and the improvement of requirements for photovoltaic power generation efficiency, the problem of photovoltaic power generation is gradually emerging. Such as figure 1 As shown, in order to facilitate the construction of photovoltaic power stations and improve the efficiency of photovoltaic power generation, it is usually used to connect several photovoltaic modules in series to form a photovoltaic string near the modules, and then connect them to the inverter for grid-connected power generation. NEC2017 stipulates: "Outside of the string, the controller is installed within 0.3 m...

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Problems solved by technology

However, after the photovoltaic modules are connected in series, a high DC voltage will be generated. If the connection between the photovoltaic string and the inverter is directly disconnected when the photovoltaic string is working, the DC high voltage generated by the photovoltaic panels will cause arc discharge, resulting in dangerous accident

like figure 2 As shown, the current method for shutting down the photovoltaic string is mainly to connect the semiconductor switch directly between the photovoltaic string and the inverter. However, due to the large conduction loss of the semiconductor switch, the semiconductor switch is used as the shutdown The circuit breaker needs to be equipped with a larger heat dissipation structure, which has a greater impact on power generation efficiency

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