Research On Inverter System Robust Voltage Control Based On Single-phase Photovoltaic Generation

The excessive consumption of traditional energy has caused the energy crisis and serious impact on the ecology,the new energy distributed generation(DG)came into being,and photovoltaic power generation,with its unique advantages,has been widely concerned,becoming a very promising power generation mode in the future.As the core part of photovoltaic power generation,inverters often operate in parallel.How to achieve power sharing,suppress the circulation between inverters and improve the quality of inverter output waveform has become a hot topic of domestic and foreign scholars.Based on the single-phase photovoltaic power generation system,the operation control of photovoltaic inverter system is studied in this thesis.Firstly,the structure of photovoltaic power generation system,the principle of photovoltaic cell and the maximum power tracking of photovoltaic array are analyzed.The two-stage structure and the former DC boost circuit are designed to provide the premise for the research of the later stage photovoltaic inverter system.Secondly,for the single-phase photovoltaic inverter system,through the establishment of equivalent circuit for the parallel inverter operation mode,the shortcomings of the traditional droop control method in the power share mechanism are analyzed,and it is difficult to suppress the circulation between inverters and the steady-state deviation of system frequency and bus voltage caused by the inherent droop characteristics.In order to solve these problems,a improve droop control strategy based on second-order generalized integration(SOGI)is proposed.It can effectively suppress the circulation between parallel inverters,accurately share the active and reactive power,and enhance the ability to adapt to the power network.Finally,a fast terminal sliding mode control(FTSMC)method based on nonlinear extended state observer(ESO)is proposed to solve the power quality problem of common bus voltage caused by parameter perturbation and load change in photovoltaic inverter system.The disturbance effects such as parameter perturbation and load variation are regarded as a lumped uncertainty,and the state space model of the uncertain inverter system is established.Then,a nonlinear ESO based on hyperbolic tangent function is constructed to estimate the uncertainty in real time.Based on the ESO,a sliding mode controller with fast terminal attractor is designed.The output voltage of the inverter system can track its reference voltage quickly and accurately,and the system robustness can be enhanced.