Research On Grid-connected Control Of Inverter Interfaced Distributed Generation Considering High Penetration

As the depletion of non-renewable energy such as coal,oil and gas,and increasingly serious environmental problems,the application of distributed generation has been widely concerned.With the increase of the proportion of distributed generation in the power grid,the role of inverter should also change.Inverter should not only provide power to the power grid,but also provide power support to the power grid.Aiming at the grid connection of inverter distributed generation with high permeability,the multi-mode switching control strategy based on offset partition is studied.First of all,the main operation control modes of inverter include PQ control,Vf control,Droop control,etc.The control mode is unable to meet the requirements of grid-connected distributed power supply for power grid considering high permeability.In order to meet this requirement,the operation control mode of inverter is perfected.Maximum active power output control mode,minimum active power output control mode,maximum inductive reactive power output control mode and maximum capacitive reactive power output control mode are designed and verifies the operation through simulation.Secondly,through the relationship between active power and frequency,reactive power and voltage,a partition control strategy based on offset degree is proposed.According to the frequency and voltage of the system,the offset degree is calculated,and the power system is divided into nine areas by offset degree,and the inverter operates in different working modes in the nine regions.The active power and reactive power output by the inverter are dynamically distributed and the frequency and voltage stability of the power grid are guaranteed,and the power support of inverter distributed power supply to the system is realized.The effectiveness of this control strategy is verified by simulation.Finally,Multi-mode switching control strategy based on partition control is studied.In order to solve the problem of frequent switching of inverter operation mode caused by slight fluctuation of system frequency and voltage at partition critical point,in the action criterion of interval switching,the switching margin is increased and the action threshold is raised.And verifies the effectiveness of the interval switching method by simulation.