Research On The Harmonics Detection And Suppresion Of The Grid-Connected Photovoltaic System

With the rapid development of the economy, more and more resources are required. All the world is focused on the exploitation and usage of the new resources in order to relieve the shortage of the resources and the environmental problem. The solar energy draw people’s attention because it is inexhaustible. So PV becomes popular among the scholars, as a result, PV develops fast and a lot of achievement is accomplished. However, there is a lot of negative effects on the power system due to large numbers of PV connected to it(Named as GCPV:Grid Connected PV). For the sake of the safety of the power system, the GCPV need to satisfy some solid requirement. This paper focuses on the research of GCPV harmonics detection method and restraint technology to solve the harmonic pollution.First, this paper analyzes the PV properties, and the mathematical model of the PV is deduced. After that, the PV MPPT problem is discussed and the Perturbation and Observation method is adopted to solve this problem. According to the mathematical model and the theory of the MPPT method, the PV model is finished in MATLAB and the simulation is performed to prove the validity of the model.Second, the FFT and wavelet transformation harmonic detection method is researched. This paper makes some correction of the FFT to solve the problem of frequency spectrum leakage. As to the wavelet transformation harmonic detection method, The selecting principle of wavelet base is introduced. Besides, the multi-resolution analysis and choice of sampling frequency is emphasized. Then Voltage/Current double-loop control PWM harmonic suprression tecnology is applied to perform GCPV to suppress the harmonics.After that,the controller’s parameter design method is research to supress the harmonics better.In the end,the control model is finished in MATLAB.Third, the GCPV model is completed in MATLAB. At the first place, the output of the inverter is detected through FFT harmonic detection method when the temperature and the light intensity is steay. The results show that the harmonic content is within the scope of the standard, so the correctness of the harmonic suppression technology and the controller’s parameter design method is verified preliminarily. After that, the output of the inverter is detected through FFT harmonic detection method considering the change of the temperature and the light intensity, the result is also nice and the dynamic performance of the GCPV is good which proves the effectiveness of the above technology once again.Then the harmonic of the unsteady state GCPV is detected of through the wavelet transformation harmonic detection method. This paper analyzes the advantages and disadvantages of these two methods.Last but not least, for the purpose of validating the performance of the proposed harmonic detection method and harmonic suppression technology in the actual application, this paper designs the GCPV experimental vertification platform hardware and software based on TMS320F2812. The DSP power supply circuit, signal conditioning circuit, communication circuit,drive circuit,GUI circuit,etc are designed in DXP. As to the software part, the main program and the interrupt subroutinte of the GCPV experimental vertification platform are designed.The features of them is analyzed and the design flow charts are also given.Besides,the program of the double-loop control method is written.