Research On Control Strategy Of LCL Type Grid-connected Inverter For Ship New Energy

Ship transportation consumes large amounts of energy substances and generates large amounts of pollutants.With the trend of energy saving and emission reduction,the application of ship new energy has been gradually promoted.To integrate the electricity generated by new energy into the ship’s power grid,the inverter plays a central role,so it is necessary to adopt appropriate control strategies to control the inverter.The harmonic content of the grid-connected current output by the inverter is relatively large,which will cause impact on the ship’s power station with limited capacity.Therefore,it is necessary to add a filter on the rear side of the inverter.LCL filter are gradually being used,which compared to the traditional L and LC filter,can better filter out the high frequency harmonics;meanwhile,its small size,can reduce the weight of new energy equipment in the grid and reduce costs.However,the LCL filter itself is a third-order system.If the correct control strategy is not adopted for the LCL inverter grid-connected system,resonance will occur in the system and the system will not work properly.This paper takes the ship new energy LCL inverter networked system as the research object,and conducts in-depth research on the issues of resonance suppression,parameter design,grid voltage information synchronization technology,and grid-connected control strategies under different network voltage conditions of the LCL filter.Finally,based on the Matlab / simulink platform for simulation,and do a corresponding analysis.Firstly,establish a mathematical model of the LCL grid-connected system for for ship new energy.Aiming at the problem of system instability caused by resonant peaks of LCL filter,a scheme of damped resonant peaks with capacitive current feedback is designed.For the problem that the parameters of LCL filter are difficult to determine,a genetic algorithm is used to optimize the parameters of the LCL filter.The feasibility of the active damping and genetic algorithm is verified by simulation.Secondly,new energy grid-connected networks require phase-locked loops to track grid voltage information.Describe the requirements of phase-locked loops for shipbuilding power grids.To solve the problem that the general phase-locked loop is difficult to meet the ship’s grid voltage requirements in response speed or accuracy,a phase-locked loop based on an adaptive observer is designed.The focus is on the design process and stability of the observer.Simulation experiments show that the adaptive phase-locked loop can quickly and accurately track grid voltage information and provide accurate grid voltage phase and frequency information for the following grid-connected system research.Then,based on the analysis of system stability,the active damping control strategy using capacitive current feedback is determined,and the controller parameters are designed;the grid-connected reference current instruction is calculated according to the instantaneous power theory;and the principle of SVPWM modulation is introduced.The simulation verifies the feasibility of the modulation method,the correctness of the capacitive current active damping control strategy and the rationality of the controller parameter design.Finally,taking into account that the ship network is prone to three-phase voltage imbalance,the influence of grid voltage on the grid-connected current is analyzed.Based on this,a full-voltage forward-feedback control system is designed.Simulation experiments show that the grid voltage is fully feedforward.The strategy can completely eliminate the disturbance of the grid voltage to the grid-connected current,and realize that the grid-connected current has a sinusoidal,symmetrical and low-harmonic content into the ship’s power grid under the unbalanced grid voltage conditions.