The ship power station is composed of a prime mover, a generator and a main power distribution unit. Due to the small capacity of the ship power station, the large load on the power station has a large impact on the power station; the working environment of the ship power station is special, and the reliability of the power station operation is high. Therefore, it is very important to realize the automation of the ship power station and the level of management. We take the power station on the current ocean-going ship as the research object, and use the S7-300 programmable controller widely used in the field of automation and approved by the national classification societies to realize various control functions of the ship power station automation, only the generator set is operated according to the power station. The situation and the actual load are required, and the standby unit is automatically started in a predetermined order, and the situation of automatic investment and automatic shutdown is introduced. 2 Preparation before starting (1) The heating cylinder in the stop state is electrically heated, the temperature is controlled at 6568 C; the periodic pre-lubrication method is used, the lubrication time is 3 min, the interval time is 1; the disc bar is placed in place, melon 2=1 The temperature and pressure of oil, fuel oil, cooling water, etc. are normal, M0. 0=1; the reset button on the main switchboard is “resetâ€, 10.3=1. The above conditions are the logical relationship of “andâ€, when they are all 1, the unit Standby status flag M0.1=1. 3 Automatic start and automatic stop command formation The system issues a start or stop command according to the principle of grid operation power, so that the total power of the generator running on the grid matches the actual power consumption of the grid. The corpse = 15% /, the single machine bears 85% of the corpse B is the maximum power margin, taking five = 1.5 /,. 4 Heavy load Before inquiring about the large load to invest in the power grid, it is necessary to first check the power running of the power station to allow the start of large loads. If the power reserve of the grid is less than D after a large load is input, the standby unit must be automatically started first, and the vehicle can be loaded with a large load after the vehicle is loaded and confirmed. The system connects the analog load to the PLC through the button and compares it with the operating power of the grid. The analog load is obtained by using a potentiometer to obtain a DC voltage signal, which is then converted into the power equivalent to the large load to be input. The overloaded query expression is: - corpse - a corpse x This program is completed using the RS trigger command, the AND gate, the NAND gate logic instruction, and the controllable pulse generator and pulse distributor (start sequence selection) programmed by the S7-300 PLC. 6 automatic start control program of the prime mover The system adopts electric mode, and the starting time does not exceed 2s each time to prevent burning of the starter motor. When the starting speed exceeds 250 RPM, it indicates that the starting is successful. Each time the number of repeated starts is not more than 3 times, the number of repeated start intervals set to 003TMD60 speed is converted to floating point number, and the stored LMD76SET is stored in the memory double word MD64. L0 4=1, when the prime mover speed is less than 250rom, Q4.1=1. Then the restart start interval timer T2 starts the start timing, and the repeat start interval time is 5 (the actual speed of the prime mover is physically converted to the engineering value A Q5.4 6 =1 Repeated start. 7=1 is the first successful start. 0=1 is the first start failure. 1=1 is the second successful start. There is an increase command Ml.0=1, the start condition satisfies 1=1, there is no emergency brake command 11.0=0, no start failure command Q5.3=0, then Q5.4= 1 start chain release, the start motor can Get electricity. =1 is the second start failure. If the starting time is too long, then Q4. Using two extended pulse timers SE to report 3 = 1 is the third successful start. 瞥 pulse generator. D2 = 1 is the third start failure. If the start failure is Q5.3=1, the Q5.6 control alarm light will flash. Three start failures Q5.2=l or one start 7 control report ringing. The time is too long (2s) Q4.2 10.3=1 to reset the alarm. 3=1 indicates that the start failed, and the start is terminated and an alarm is issued. 7 Conclusion S7-300PLC is widely used in ship automation power station management, host remote control, cabin monitoring report and other fields. This article is limited to the length of the article, only the automatic start control process and some application procedures of the ship power plant generator set. This section of the program is repeatedly debugged by the laboratory to achieve the desired function. 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