Algorithm Research On Grid-connected Control For Single-phase Photovoltaic Power Generation System

With the rapid construction of the power gird,the impact of the quality of the power grid on the social economy is even more profound.The defects of the grid voltage will bring a lot of problems and even loss,so the study of power gird voltage defect detection method is particularly important.In this paper,the advantages and disadvantages of common electric voltage defect detection methods are analyzed,an improved detection algorithm is proposed which is suitable for UPS,and the simulation and analysis are implemented by combining simulation tools(Microsoft,MATLAB and Visual Studio PSIM).Finally,the algorithm is verified by a experimental prototype.The contents of this paper are as follows:(1)In this paper,the research and development trends of voltage defect detection at home and abroad are reviewed,and the advantages and disadvantages of several common methods are analyzed.(2)The important theory and implementation scheme of the rapid detection method of the electric voltage defects are described;the difference between IIR and FIR filter and the design points of IIR filter are analyzed;then the conventional zero crossing digital phase locked loop is analyzed,and the improved digital phase locked loop and discrete implementation method based on d-q transform is proposed;finally,the principle of voltage segment detection algorithm and the scheme of program implementation are presented.(3)The simulation results show that the band pass filter and phase shift filter can effectively filter out the voltage harmonics,which makes the phase locked loop can continue to maintain the normal operation under the condition of power shortage and power loss.The IIR can effectively filter the harmonics in the voltage,so that the voltage segmentation detection function can be easily implemented.Considering the delay of IIR filter and the delay of voltage segment detection,the detection algorithm of the power supply voltage can be less than 6ms;other operating conditions such as voltage amplitude and frequency can be detected in time.(4)The city electric voltage defect algorithm is applied in the UPS prototype,and the actual effect is tested;the bandpass filter and the phase shift introduced in the digital phase locked loop can effectively filter the harmonic and ensure the reliable operation of the phase locked loop;the grid voltage defect detection algorithm can play the expected role.Under the common conditions,city electric voltage defect detection algorithm can response immediately and meet the design requirements.