Research On Control Strategy Of Asynchronous Generation For DC Grids

With the development of the ship power system,the requirement for more convenient operation,more reliable control,safer navigation and more energy saving are proposed for the ship performance.In order to meet many high-level requirements,the ship's DC integrated power system gradually developed.Under the circumstance that the ship-borne DC power grid is developing greatly,this paper aims at reducing the fuel consumption and the stability and reliability of the variable-speed asynchronous power generation system based on the DC power grid,and carries out research on its integrated control strategy.The research on the control strategy of asynchronous power generation system for shipboard DC power grids is mainly carried out in the following aspects:1.Given the structure of asynchronous variable-speed power generation system based on shipboard DC grid,and elaborated the mathematical model of diesel engine and governor,asynchronous motor for power generation,power electronic converter and other major equipment.2.Study the characteristic curve of a typical diesel engine type,deeply analyze the relationship between torque,speed and power,and fuel consumption rate;propose a piecewise linear fitting method to perform mathematical analysis on each variable curve.The implementation of the control strategy provides the conditions.3.With the diesel generator set as the object,combined with the analysis of universal characteristics,a stepwise step speed control strategy was proposed for the problem of variable speed and fuel economy operation.Using this strategy,the speed planning in the unit's full power range can be performed;this can effectively solve the problem of high fuel consumption when the generator set's constant speed is running at medium and low power.4.For the problem of DC voltage stability of variable-speed generator sets,starting from the DC-side power balance,the introduction of a direct torque control strategy based on the instantaneous torque control of the instantaneous torque converter converter torque control strategy can be better To solve the problem of DC bus voltage stability control in asynchronous power generation systems,with reliability.5.In order to study the power distribution problem of parallel operation of multi-machines in DC power grids,the power-voltage(P-U)droop control characteristics of the DC power grid are designed based on the AC grid power distribution strategy,and the power of the DC grid can be autonomously divided equally.The DC power sharing control method provides a certain theoretical basis.6.Using computer simulation experiments and small-scale physical experiments to verify the control strategies described in the paper.The correctness of the shift strategy and the fuel-saving characteristics were verified by simulation experiments,and the feasibility of coordinated control of speed and torque and droop control strategy was verified by a small proportion of physical experiments.