Characteristics Of Large-Scale Grid-Connected Photovoltaic Power Plant And Its Control Technologies

With the focus from the whole world on the serious greenhouse effect caused by the excessive consumption of fossil fuel, our country is trying to promote solar and other renewable clean energy in power technologies. In the first two chapters, the principle of photovoltaic(PV) power generation is introduced briefly, focusing on the domestic as well as overseas development status and the prospects of photovoltaic technologies. Due to the randomness and discontinuity of the output of photovoltaic, maximum power point tracking (MPPT) has always been the heat topic. There is a continuous improvement in MPPT in order to meet all the new requirements. Hence, some modified methods of MPPT have been presented, which can not only enhance the system stability, but also fit numerous operating conditions. The grid-connected photovoltaic plant will impact on the grid in many aspects, such as the islanding operation、the problem of harmonic pollution and reactive power compensation, voltage flicker. This article summarizes some methods which are used to solve these problems. The inverter is the key technology of grid-connected PV system. The functions and requirements of the grid-connected inverter are described as well as the evolution of its topology and the issues to be resolved.Currently, the large-scale and grid-connected photovoltaic systems are certainly the major trends in the future. Considering the strong randomness of PV system caused by environmental impacts, the MATLAB/SIMULNK is used to model the PV plant and the characteristics of the PV output in typical cases is analyzed by processing the numerous real environmental data. A low-carbon power dispatch of big-scale grid-connected PV power plant is also proposed. On the other hand, with the increase of the capacity of PV power plant, it’s important to consider as well as resolve more negative effects when PV plant is connecting with the grid, which make more requirements to the inverter. Consequently, this paper propose a multi-mode control strategy which contains the compensation of reactive and harmonic current、 the MPPT and active control. In the end of the paper, the feasibility and the advantages of the proposed control strategy is verified by the MATLAB/SIMULNK.This paper also works on a large-scale centralized grid-connected PV system which can keep supplying the required power to the grid for dispatch instead of supplying the electricity to the load directly. The hybrid electricity storage which consists of battery and supercapacitor is selected for the proposed system in order to obtain higher efficiency. Control strategy is proposed focusing on the required DC power at the DC link before the grid-connected inverter. Two typical groups of real collected data are used for the simulation considering about practicality. At last, the simulation results demonstrate the good performance and feasibility of the proposed system as well as the control strategy.