Harmonic characteristics of power generation unit of centralized photovoltaic power station connected to Tibet power grid

摘要

Centralized photovoltaic power station is an important part of building a new power system, whose power generation unit is the main equipment of the photovoltaic power station. Therefore, it is the basis of analyzing the harmonic characteristics of photovoltaic power generation to study the harmonic generation mechanism and influencing factors of power generation units and establish the harmonic equivalent model of photovoltaic power generation units. In this paper, firstly, the harmonic generation mechanism is analyzed from the aspects of sinusoidal pulse width modulation (SPWM) and dead time of inverter. Secondly, the correlation analysis of influencing factors of output power of photovoltaic power generation unit is carried out, and then the influence of output power on harmonics is analyzed. Thirdly, the harmonic characteristic model of photovoltaic power generation unit based on actual photovoltaic power station and influencing factors is constructed. Finally, the theoretical simulation of SPWM modulation and dead time is verified and analyzed, and the simulation results of harmonic characteristics are compared with the measured data. The results show that the harmonic characteristic of the centralized photovoltaic power station is mainly to generate high-frequency odd-order harmonics, which will generate extra high-frequency even-order harmonics when the irradiation is too high or too low, and cause interharmonics when the irradiance fluctuates on the DC side of the inverter.