Research On Control Strategies Of Electrical Compound Charging System

The electric compound charging system can effectively improve the response capability of diesel engines in low engine speed,but a proper control strategy is the precondition to ensure the charging system to work normally and to switch charging modes smoothly.In this paper,the transient control strategies of the electric compound charging system were studied with the method of simulation.Firstly,two different arrangement schemes of the electric compound charging system were put forward according to the position relationship between the electric compressor and the turbocharger compressor.And the performance of the electric compound charged engine at low engine speed was targeted,according to which,the electric compressor could be preselected with theoretical calculation.After that,the GT-Power simulation models of the electric compound charged diesel engine under the two different arrangement scheme were set up based on a 6V single stage turbocharged diesel engine.According to the simulation results,the charging system presented better engine speed adaptability and charging mode switching performance when the electric compressor was placed after the turbocharger compressor,and therefore,this arrangement scheme was selected as the follow-up simulation models.In order to reflect the real response performance of the electric compressor,a closedloop PID speed regulation model was set up in Matlab/Simulink platform with PWM speed regulating method,and the PID parameters was adjusted to achieve a satisfying speed regulation performance.Finally,a dynamic accelerating condition in which the charging modes switch at 1400 rpm engine speed was set up and the influence of the change rate of the rotational speed of the electric compressor and the open timing of the bypass valve on the electric compressor cutting-out transient process was studied.And an acceleration condition in which the electric compressor was cut out at different engine speeds was set up and the influence of the electric compressor cutting-out engine speed and its charging load was studied.According to the study results,a transient control strategy of the electric compound charging system was put forward and its control effect was estimated with a dynamic acceleration simulation.