| The grid-connected certification of new energy power generation is an important means to supervise and evaluate the quality of large-scale stations and ensure the safe operation of new energy power generation.Among them,the simulation analysis and harmonic control of harmonic characteristics of photovoltaic grid-connected inverters is also one of the long-term challenges in the field of power quality.This paper is devoted to constructing a detailed transient model of photovoltaic grid-connected inverter based on measured and simulated data and proposes a corresponding harmonic control scheme,which provides reference for grid-connected certification of photovoltaic power generation system.On the one hand,the harmonic problem caused by the investment of a large number of power electronic equipment is the main source of the output harmonics of the photovoltaic power station,which leads to the complex mechanism of the harmonic generation of the photovoltaic power station.The simple superposition of the harmonic detection of the power generation unit is used to analyze the power station.Characteristic harmonics are not sufficient and accurate.On the other hand,the photovoltaic power station has a wide frequency distribution of harmonics,contains a large number of high-order harmonics,and mostly uses LC-type filters.The resonant point introduced by the filter is likely to cause amplification of a certain output harmonic of the inverter,making the high-frequency Harmonic governance has become more difficult.Based on the two points raised above,this paper focuses on the analysis of harmonic characteristics and harmonic control of photovoltaic power generation units.This type of problem is often more prominent in power grids that are not directly connected to power grids.Solving these two kinds of problems depends on the research of the dynamic harmonic model of the photovoltaic power generation system,which is integrated into the photovoltaic power station,the photovoltaic inverter and the filter.Based on the analysis of the harmonic characteristics and harmonic influence factors of photovoltaic power generation system,this paper proposes a new active filter structure for solving high frequency harmonics,which can output to the photovoltaic inverter.High frequency harmonics are effectively managed.The paper mainly includes the following three parts:The first part first summarizes the mechanism and the essential causes of harmonic problems,and summarizes the harmonic amplitude and specific times generated by each mechanism,including modulation,dead zone,DC side fluctuation and other factors.The part that has a high content and needs to be treated with emphasis.Then,the factors affecting the harmonic output of the photovoltaic power generation system are analyzed and summarized.The external factors include the output of the power generation unit,the grid voltage distortion and the component parameters affect the inverter output harmonics,and the internal control factors are low-inverse.The converter output power and the high inverter output power are discussed and analyzed separately.The second part studies how to establish a dynamic harmonic model of a photovoltaic power station.Firstly,the basic principle of each step of the two-stage photovoltaic power station is expounded,and according to the mathematical model of the control parameter analysis part in Chapter 2,the control strategy of the photovoltaic power generation system is determined,and then the photovoltaic inverter details are established based on the above.The transient model is verified by the accuracy of the model.Finally,the PV inverter output harmonic engineering test is completed with the cooperation project platform,which verifies the correctness of the theoretical analysis and corrects the model according to the actual data..The third part is mainly for the problem of the treatment of characteristic secondary high-frequency harmonics of photovoltaic power plants.This part firstly analyzes and summarizes the deterioration of higher harmonics in the power grid.Based on the active filter,a new high frequency active filter(SiC-APF)based on SiC switching device is proposed.Its control structure ensures a good amplitude-frequency response near the resonant frequency.The application of it in typical engineering application scenarios is analyzed.Firstly,the simulation model of the new active filter is built for the practical engineering application from the perspective of impedance model,and the voltage and current management of each busbar is carried out in the PSCAD simulation platform.The simulation verification is carried out.Finally,the experimental verification corresponding to the simulation analysis is carried out through the RT-LAB hardware-in-the-loop simulation platform,and the effectiveness of the proposed device is verified again.The harmonic characteristics analysis,harmonic domain modeling and corresponding high-frequency harmonic control technology of photovoltaic power generation system are the key issues that restrict the large-scale popularization and application of photovoltaic and grid-connected inverters.We believe that through the above analysis and technology for the future The grid-connected certification and harmonic control of photovoltaic inverters have good guiding significance. |
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