Research On Model Analysis And Control Strategy Of Photovoltaic Grid-connected Inverter

In order to improve the photovoltaic system output energy utilization efficiency, improve the grid power quality, the grid-connected current control of PV inverter and the two-stage photovoltaic grid-connected inverter control have been studied in this paper, separately carried on the theoretical analysis and simulation verification. The main contents of this article are: PV grid-connected inverter model, LCL filter resonance peak damping method, grid voltage differential feedforward control strategy, photovoltaic battery MPPT control, two-stage photovoltaic grid-connected inverter system coordinated control.This paper establishes three-phase grid-connected inverter model based on LCL filter, it introduces the method of design parameters, due to the existence of the resonance peak in LCL filter easily leading to instability of grid-connected inverter, this paper compares the advantages and disadvantages of various methods of damping, concluding that the active damping method based on capacitor current feedback has good damping effects, and no loss.Comparing with PI regulator, PR regulator has a better accuracy and robustness, it is more suitable for grid-current control, while the high frequency background harmonic of power grid can affect the stability of the grid-connected power quality. Therefore, this paper proposes the strategy of the grid-connected current dual-loop control based on grid voltage differential feedforward and PR regulator, after simplifying the block diagram, the capacitor current loop is equivalent to the inductor voltage differential feedback at the grid-side, the feed-forward of grid voltage is equivalent to the proportion feedforward. The simulation results show that the strategy can basically restrain the influence of harmonics in grid voltage to grid power quality. What is more, we need not eliminate the detection of the capacitor current through using this strategy, it saves a large cost.This paper introduces the two-stage photovoltaic grid-connected inverter control principle, using incremental conductance to track maximum power point control in the first stage, the strategy of the grid-connected current dual-loop control based on grid voltage differential feedforward and PR regulator is adopted in the second stage. Then build the model in MATLAB/Simulink platform, simulation results show that the two-stage photovoltaic power generation system can be of coordinated operation using this method, also it is able to quickly reach the network requirements and meet the network conditions.