Research On Control Strategy Of DC Converters For New Energy Ships

With the development of green ships,the DC microgrid of new energy ships has become a hot research topic in the shipbuilding industry.Changes in the navigation status of ships due to environmental and emergency situations may disturb the load power,leading to oscillation of the ship’s DC bus voltage,and even endangering the stability of the system.The DC converter is an important component for stability of ship DC microgrid,and the control algorithm of the DC converter has great effect on the DC bus voltage.Therefore,this thesis will study the control strategy of ship DC converters.This thesis uses the state space averaging method to model a ship boost DC converter with a constant power load and obtain its dynamic equation.Then the state feedback precise linearization and coordinate transformation are used to obtain the linear system model of the ship boost DC converter with constant power load and disturbance.On this basis,a fixed time convergence control algorithm for ship boost DC converter is proposed.Using disturbance observer,fixed time stability theory,and backstepping control method,a fixed time disturbance observer and a fixed time convergence backstepping controller for ship DC converters were designed,respectively.The stability of the designed controller was verified through Lyapunov stability theory.Finally,through simulation and comparison with traditional PI control under load interference and voltage changes on the power supply side,the simulation results show that the proposed controller has the advantages of fast response speed,high tracking accuracy,and strong anti-interference ability.A voltage current droop control strategy is adopted to address the issue of uneven power distribution during parallel operation of ship DC boost converters in the system.Firstly,the principle of droop control was introduced and its limitations and improvement methods were pointed out.Then,a parallel current sharing control strategy for ship boost DC converters based on improved droop method is proposed to address the issues of DC bus voltage drop and system current sharing accuracy caused by droop control.The proposed parallel current sharing control can compensate for the voltage drop of the DC bus,achieve current distribution between ship DC converters,and improve current sharing accuracy to a certain extent,ensuring system stability and anti-interference ability.Finally,by comparing the proposed parallel current sharing control with traditional droop translation control under load interference,the simulation results show that the proposed parallel current sharing control has the advantages of fast current sharing speed and high current sharing accuracy.