An intelligent junction box for eliminating pid decay and its working method

Abstract

The invention discloses a smart junction box for eliminating potential induced degradation (PID) and a working method thereof. The smart junction box for eliminating the PID comprises a junction box shell; and a central processing unit, a photoelectric sampling module, a carrier signal coupling element, a switching signal driving circuit, a working power supply module, a carrier signal transmitter module, a negative electrode connector, a positive electrode connector, multiple MOS type electronic switches, a bypass diode and the like are mounted in the junction box shell. The working method of the smart junction box for eliminating the PID comprises: by utilizing programming operations of an intelligent control circuit and an electronic diverter switch in the junction box, synchronous and regular periodical overturning is performed on voltage output polarity of whole battery modules mounted on a photovoltaic power generation array, so that sodium ions in glass are pulled back to the original place by a subsequent negative electric field when the sodium ions in the glass are far from a battery piece in a process of migrating to the battery piece; therefore, such PID long-term decay effect on a photovoltaic cell module is eliminated, power generation efficiency is improved, and effective service life of the photovoltaic cell module is prolonged.

Description

Technical field: [0001] The invention belongs to the technical field of safety protection devices for photovoltaic power generation systems, and in particular relates to an intelligent junction box for eliminating PID decay and a working method thereof. Background technique: [0002] According to the long-term observation and experimental analysis of European photovoltaic power plants by researchers, a photovoltaic power plant with the middle potential of the output voltage of the string as the protective grounding point has a PID (Potential Induced Degradation) in half of the components that are in the negative output of the ground potential. Potential-induced attenuation effect refers to the fact that after a long period of operation of the photovoltaic panel, for the components in the potential negative output, when the dust and water vapor on the glass surface of the photovoltaic module form a conductive film, which is conducted through the grounded aluminum frame. Form ...

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Problems solved by technology

[0007] 1) If the negative pole is grounded, a high voltage will be formed between the positive pole and the ground, which may easily cause electric shock accidents;

[0008] 2) If a ground fault occurs in the positive pole or the cable between strings, a fault current or arc discharge will be generated through the ground wire, which may easily cause a fire

[0009] 3) The cost is relatively high, and the space occupied by the isolation transformer is relatively large;

[0010] 4) Because the photovoltaic networking method in Europe is different from that in North American countries, in the European photovoltaic standard, the system voltage is 1000 volts, and most of them adopt the method of series combination of 35 battery modules, so the middle grounding scheme is adopted. So that the ground voltage of the positive and negative terminals is about + / -500 volts. If the negative pole is grounded at one end, all the original photovoltaic inverters cannot be used, and the voltage of the positive terminal to ground is as high as 1000 volts, which greatly increases the system risk factor

[0014] The PV panel is connected to a forward bias voltage to pull back the sodium ions that migrate to the battery due to the PID effect during operation. The limitation of this solution is that this device can only work at night when the battery panel is not generating power, and The forward bias voltage generator itself consumes a lot of power every day

[0015] The above three solutions, no matter in terms of practicality or economy, do not seem to provide operators with a satisfactory solution

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