Speed Control Of Diesel Generating Set Based On Load Feedforward

As a prime mover,diesel engines are widely used in the fields of automobiles,ships,engineering machinery and aviation.Electronic control technology for diesel engines is a technology that uses microprocessors to achieve optimal control of diesel engine work processes.Electronic speed adjustment technology is the core of diesel engines electronic control technology.It is significance for diesel engine to study electronic speed adjustment technology,which can optimize performance,reduce fuel consumption rate,and improve exhaust emissions.At present,the governor widely used in diesel engines is a digital electronic governor,which consists of three parts: an electromagnetic sensor,a controller,and an actuator.The controller is composed of a dedicated microprocessor and a customized circuit board.In addition to the input and output signals,all parts of the control system are implemented by software programs,which reduce the dependence on the signal,with strong adaptability and expansion capabilities.However,because the electronic governor is adjusted according to the speed deviation delta n,that is,after the change of speed is detected,the electronic governor starts to operate.This speed regulation will inevitably lag behind,resulting in a large fluctuation of diesel engine speed.This paper aims to further improve the speed control accuracy of diesel engines used in generator.For diesel generating sets,stabilizing its speed not only improved the performance of the diesel engine,but also optimized the performance level of the output voltage and frequency of the diesel generator set,which enable the control system to have better dynamic and static characteristics.For this reason,this paper has done the following two tasks:The working principle and control strategy of the existing digital electronic governor are analyzed to improve the deficiency of the current electronic governor control algorithm.The control strategy of adopting speed feedback-load feedforward is proposed.That is,when the load has occurred and the speed has not yet reached the difference,the load disturbance is fed forward to the controller to adjust the fuel supply in advance and stabilize the speed of diesel generator.A digital simulation model was built in the Simulink.By comparing the simulation models of PID,adaptive fuzzy-PID,speed feedback,and load feedforward,it is found that the control strategy using speed feedback-load feedforward has good control performance.A embedded system of diesel electronic governor based on feedforward control was designed.In terms of hardware,MC9S12XS128 microcontroller of Freescale is used as an embedded system microcontroller,and a series of peripheral hardware circuits such as speed interface circuit for diesel engine,current feedback and power drive circuit for actuator,overcurrent protection circuit for actuator,communication module circuit and stator conditioning circuit for motor are designed to meet the requirements of actual function.In terms of software,we built an embedded system by porting the μC/OS-Ⅱ real-time operating system to the MC9S12XS128 microcontroller of Freescale.The multi-task management mechanism of μC/OS-Ⅱ real-time operating system to balance the requirements of the various tasks in the electronic governor to the CPU,so that each task can work in coordination.The μC/OS-Ⅱ operating system not only enabled the microcontroller to ultilize the limited system resources more effectively,but also significantly improved the real-time performance of the microcontroller.The software and hardware of electronic governor embedded system were designed to carry on experiments,and the result shows that compared to the original speed feedback control system,the speed regulating function of embedded system of diesel electronic governor is significantly improved by using speed feedback and load feedforward control.