Research On The Control Strategy Of Low Voltage Shore Power System

For port cities,the ship’s fuel auxiliary generators are the main source of air pollution.With the deepening of prevention and control of air pollution,the use of shore power instead of port ship’s auxiliary generators has gradually become a new research hotspot.Shore power supply technology has gained wide attention with its unique advantages in power replacement.In view of the existing problems in the development of low voltage shore power supply,this paper has carried on the thorough research from the independent and coordinated control of the electric converter,the converter control considering the ship load characteristic and synchronous parallel opration of the shore power system.Firstly,this paper designs the main circuit parameters of the shore converter by analyzing the working principle of the low voltage ship shore power source,and establishes the mathematical model of the shore electric converter.On this basis,the PI of the shore power source Double ring control,design of the inner loop current and the outer ring voltage controller parameters.Aiming at the three-phase unbalance and nonlinear harmonic characteristics of ship load,an improved double-loop control strategy combining resonant control and predictive control is proposed.The outer ring in the original PI controller on the basis of adding 2 times and 6 times the frequency of the resonant controller,used to improve the resonant frequency of the gain,to eliminate the corresponding output voltage of the negative sequence and harmonic components;inner ring with the predicted current Control,increase the control of the bandwidth to achieve the actual current quickly and accurately track the outer ring given current.The proposed simulation model verifies that the proposed improved double-loop control strategy still has a higher output power quality under the ship’s load characteristics.Secondly,an improved power feedforward control strategy is proposed for the shortcomings of the steady-state dynamic response of the rectifier and the inverter,and the DC voltage fluctuation is large.Because the traditional method based on the instantaneous power theory is based on the coordinate transformation of the fundamental sequence,it can not reflect the influence of the negative sequence component caused by the unbalanced load of the ship on the power.In this paper,the fundamental forward component is included in the power feedforward,and the power change under the unbalanced load of the inverter ship is more accurately fed forward to the rectifying side,which accelerates the dynamic response of shore power,Small DC voltage fluctuation.Finally,this paper proposes an improved droop control strategy for the problem that the traditional shore power source can not accept the ship energy management system(SEMS)scheduling problem.The pre-synchronization control unit is added in the traditional droop controller to realize the shore synchronous and the vehicle;the generator inertia link is introduced in the controller so that the shore power source has the output characteristic of the generator in order to accept the SEMS scheduling and After the smooth implementation of load transfer.The simulation model is used to verify the feasibility of the proposed control strategy.