Research On Simplified Model Of Photovoltaic Power Generation System For Engineering Application

In recent years, PV(photovoltaic) generation system has been rapidly developed in the world with its clean, renewable and other advantages. With a large number of PV systems accessed to the grid, the influence of it on the grid is increasingly significant, so it is necessary for further research. However, as the detailed theoretical model of PV system is complex, and the simulation calculation needs multiple iterations, it will lead to low efficiency and poor stability of numerical calculation when simulation with detailed theoretical model for each PV system. In order to solve this problem, the research on simplified model of PV system for engineering application is necessary.Respectively from the perspective of function equivalent and external characteristics, this paper puts forward three equivalent modeling methods for PV system:(1) Simplified modeling method for PV system based on function equivalence(modelâ… ), in which the DC part and the inverter with its control strategy are simplified equivalently based on functional equivalence. DC part consisting of PV array and the MPPT is simplified to maximum output model; and inverter with its control strategy, of which the function is to achieve decoupling control of active and reactive power, are simplified to controlled voltage source with control module.(2) Simplified modeling method for PV system based on functional control(modelâ…¡). Based on the analysis of steady-state and transient characteristics of photovoltaic power generation systems, the dynamic model is equivalent to a controlled voltage source circuit model with a second order dynamic characteristic. It only need to use the light intensity, temperature, and the fault information as input, and calculate the steady-state output current before and after the fault. After determining its relevant parameters, the modeling is completed.(3) Simplified modeling method for PV system based on voltage source model(model â…¢). At first, calculating the port voltage and current before and after the fault according to the structure of the distribution network and fault information. Then calculating the equivalent circuit parameters based on the port voltage and current. Finally, modeling the simplified model in the form of voltage source cascading with impedanceBased on Matlab/Simulink platform, simulation models of grid-connected PV system are set up, with the PV system models adopting respectively the detailed model and three kinds of simplified model. The simulation results show that the output characteristic of simplified models is same as that of the detailed model, and that simplified models has a good engineering practical value which can improve the simulation efficiency effectively. Respectively, as three models have different advantages, so in engineering application, ideal effect can be obtained by selecting the corresponding simplified model according to the different requirements and conditions.