| The quality of the marine AC power system is reflected through voltage and frequency, as voltage stability depends on automatic excitation regulator system, the frequency stability depends on the speed control system of prime mover. Therefore, the speed control of marine diesel generator is an important content of marine power system stability control.This thesis mainly researches the speed governing system of marine generator set which is driven by diesel engine. First, it analysis the composition and operation characteristics of the speed governing system of marine diesel generating set, and it emphasizes on speed control strategies. Taking into account the frequently and rapidity of load changes of marine power system, in this thesis, the speed controlled by the strategy that called compound control, which is combine speed feedback control with load feed-forward control. It can compensate for the load turbulence and suppress the disturbance to the marine power system, improving the frequency stability of marine AC power system. The compound control system is optimized by the using PID control theory and fuzzy control theory. The feed-forward compensation controller, which takes load current as an input, reacts to the load turbulence quickly with the use of fuzzy decision. Feedback controller using PID make a further control on the system deviation together with feed-forward control. Next, it creates a mathematical model of the speed governing system of the marine diesel generator, and then using MATLAB/SIMULINK simulation software to build a power generation diesel engine speed control system simulation model. Through the simulation, it concludes that feed-forward/feedback compound control can reduce the stable time and the fluctuation of speed, making the speed governing steady and rapidly. Finally, it designs the speed governing system of marine diesel power generation based on S7-300PLC, especially designs hardware and software processes of the speed control system. |
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