Grid-connected Control Technology And Generation System Design Of Distributed Photovoltaic Power Station

Due to geographical location,solar energy resources with considerable reserves are very abundant in China.The development of photovoltaic grid-connected power generation technology for renewable solar energy is very important to fulfill international commitments for energy conservation and emissions reduction,as well as building a beautiful country.As the PI control technology is greatly affected by system parameters,the output current waveform distortion rate of the grid-connected inverter is large when the inverter system is disturbed.Therefore,it is necessary to innovate the grid control technology with strong grid adaptability and superior performance.Completing the software design of the maximum power tracking control and grid-connected inverter control of the distributed photovoltaic power generation,the system design of distributed photovoltaic power stations with superior operating performance and output power quality meeting grid connection requirements will be continued.The main research contents of this paper are as follows.Firstly,based on the selected MPPT control structure of the two-stage grid-connected inverter,an improved variable step conductance incremental MPPT control algorithm is designed,which could meet the requirements of system reliability.Based on the MATLAB/Simulink simulation platform,a distributed photovoltaic grid-connected power generation model with a pre-stage DC/DC converter is built,and an improved conductance incremental method is implemented at the DC/DC conversion,which links to track the maximum output power of the photovoltaic system.Secondly,a second-order sliding mode control based on the super spiral algorithm is designed to realize the DC/AC inverter process.Under this designed control algorithm,the grid-connected current has a low distortion rate,and the speed of dynamic response change to faster.When the grid voltage is unbalanced,the negative sequence component of the grid-connected current can be eliminated.The designed control does not require the phase-locked loop,which avoids the decomposition of the positive and negative sequence components of the voltage.The simulation results show the designed sliding controller is more robust than the traditional PI controller when the parameters of the photovoltaic grid-connected system change.Thirdly,according to the installed capacity and construction conditions,the photovoltaic cell module types is selected.Based on the average solar radiation data,thephotovoltaic module installation form is ensured.And the number of series and parallel branches of the circuit is calculated.After the grid-connected inverter is selected,a non-isolated single-stage photovoltaic grid-connected topology is established,which is easy to implement.According to the comprehensive efficiency of the power generation system,the estimated power generation of the project is calculated in the future operation period.Finally,the design of 20 MW distributed photovoltaic grid-connected power generation is introduced,and the structure of each component,as well as the design of lightning protection are analyzed.After adopting the super-spiral algorithm sliding mode grid-connected control strategy,the output of photovoltaic power plant verify the effectiveness of the theoretically designed control method in improving the output power quality.The actual operating data of the photovoltaic grid-connected project from May 1,2018 to May 5,2019,are used to calculate the power generation and utilization hours.The operating data under different meteorological conditions are selected,and the influence of the daily power generation and cumulative power generation of the project is analyzed when external environmental changes.