Selection steps of DC switch in the hottest photov

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Selection steps of DC switch in photovoltaic system

the selection of photovoltaic DC switch is generally based on preliminary estimation of key parameters and sufficient margin. In the photovoltaic system, the output power of the photovoltaic panel itself is affected by weather, ambient temperature, inverter power point tracking, etc; Secondly, the photovoltaic inverter itself has the limitation and protection of input power, the maximum allowable input voltage, and the limitation and protection of current; Finally, the rated breaking capacity of the DC switch itself is also related to the ambient temperature

when the environment is certain, the output of the battery board (battery array) is affected by the power tracking at the DC side of the inverter. With the increase of the voltage, the ability of the DC switch to make and break the current will decline (affected by thermal effect). In general, the DC switch used can turn on and off the actual output voltage and current of the battery board. Weather, environmental stability, inverter power tracking and so on need to be taken into account

the simplest way is to select a DC switch (both external and internal) that meets the requirements of formulas 1.1 and 1.2 above. Since the battery board cannot work on the maximum short-circuit voltage and open circuit current, the external DC switch generally uses the maximum power point voltage and current for reference:

voltage =nsxvm is the starting mark of engineering utilization of modern hydraulic technology px1.15 (formula 1.3)

current =npximpx1.25 (formula 1. Shrinkage reduction 4) for the built-in DC switch, it may also be limited by the maximum input voltage and current of the inverter itself, In order to reasonably save the system cost, the actual output voltage and current of the battery are generally based on the fact that the DC switch can turn on and off the battery. Compared with the current EU regulations on plastic materials and products in contact with food, the actual output voltage and current of the panel are not higher than the protection voltage and current of the selected inverter. In general, the on-off V-1 curve of the DC switch needs to envelope the DC voltage and current curve that the inverter allows to input. In general, the selection of photovoltaic DC switch can be based on the following steps:

1 Determine the system voltage

the maximum allowable voltage of the selected DC switch needs to meet the average system voltage requirements of the bare coating. The common ones are 600V and 1000V. Generally, the system voltage connected to single-phase inverter is up to 600V, and the system voltage of three-phase series inverter or power station inverter is up to 1000V

2. Determine the number of independent battery strings

if it is a built-in DC switch, it is integrated in the inverter, so it is related to the number of independent MPPT of the inverter. Common inverters are single channel MPPT and dual channel MPPT, and there are also a few parallel inverters with 3-channel MPPT on the market. Generally, the inverter with power level of 1kw-3kw is designed as a single channel MPPT; 3kw-30kw is a two-way MPPT, and a few companies also have three-way MPPT inverters; Large inverters above 100kW are generally input into one circuit of MPPT after converging through the combiner box. The number of independent mppts of the inverter determines the number of independent pass sections of the selected built-in DC switch

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