Key Technology Of Photovoltaic Grid-connected Inverter Based TUV Certification

The depletion of traditional energy and the problem of environmental pollution aremore and more severe. Evolving green energy as alternative energy is Significant. Solarenergy plays an important role in the new energy. As an effective means of solar energyuse, the technology of the PV grid-connected inverter has become more mature.However, after solved the security and reliability issues, the inverter can beconnected to the grid. Take the inverter to be authenticated, is the key to solve the aboveproblem. At present, there is no certification standards for inverter products in ourcountry which restricted the development of the entire PV industry. TUV certificationmark is widely accepted by European countries. And they can take certification of theinverter according to certain criteria. Certification of the inverter of TUV related toconnect to the grid, electromagnetic compatibility and safety. The focus of this paper isthe following four aspects of the support technology: Insulation resistance to the ground,Residual current, EMC and safety design.In this paper, basing on the topology of the inverter, about the above three aspects,the following processing were carried out: analyzed and simulated base on the principle,determined solutions, designed the circuit, and necessary software processing wereintroduced. Bridge method was applied to the insulation resistance testing. As the inputvoltage will affect the result, the data is sent to the main chip after sampling by the AD.Independent module is used in the residual current detection circuit, and the result issent to the main chip. The residual current detection module consists of the residualcurrent sensors, signal conditioning circuits and microprocessors. The input and outputfilter of the inverter is main designed, and for the surge protection, etc. only a briefdescription was put forward. Safety design analysis of the safety problems of theinverter, and make corresponding design in accordance with the certificationrequirements.According to the above scheme, related circuit was designed. and the effect of thecircuit was verified. For different input voltage，detection circuit of insulation resistancecan achieve the detection of the impedance which is less than13KΩ.The residual current detection module, can take accurate detection for residual current limit of300mA and sudden changes in residual current of30,150mA. The filter circuit can filterout common mode and differential-mode signal of interference effectively. The resultsshow that: the circuit can work effectively, and they can meet the requirements.