In order to ensure that the unit reaches various technical indexes, the diesel engine and the generator must be well matched when the unit is designed and manufactured, which includes two aspects of power and speed. The power of a diesel engine refers to the effective power of a diesel engine running normally at a rated speed of 12 hours continuously. The power of synchronous generator refers to the rated power output at the rated terminals of the output terminals at a constant speed. The ratio of rated power (horsepower) of diesel engine to the rated power (kilowatt) of synchronous generator is usually referred to as matching ratio. In general, the matching ratio of units used on plains is 1.6:1; for some demanding mobile power stations, the matching ratio is 2:1. The matching of speed is also very strict. The speed is closely related to the power, frequency and voltage of the unit. Therefore, the diesel engine required with the generator must have a better performance and reliable governor to ensure the generator to be carried to its rated speed and stable operation in a short time, and also to meet the speed regulation when the load is changed. Requirement.
The diesel generating set run by the unit can run on a single unit, or run in parallel and join the power system in parallel. The operation of single unit is limited by many conditions: if the power meets the requirement of heavy load condition, the operation of the unit will be reduced when the light load is running, and the standby unit will be the same as the operating unit capacity. The use of multiple units in parallel operation and integration into the power grid can enlarge the power supply capacity and improve the reliability of the power supply. The spare unit has one set, which reduces the capacity of the spare unit relatively. To realize parallel operation, the following four conditions must be satisfied: 1) the terminal voltage is equal; 2) the frequency is equal; 3) the phase is identical; 4) the phase sequence is identical. At the same time, there is also a running protection device, which can automatically and rationally allocate and adjust the active power and reactive power, so that the frequency modulation characteristics and voltage regulation characteristic curves between the units tend to be close to.
Compared with the steam turbine generator set, the characteristic diesel generating set has the following characteristics: (1) the volume of per unit output is small, the weight is light, the system is simple, and generally it is integrated as a whole. Therefore, the construction of diesel electric power station is fast. (2) The thermal efficiency of diesel engine is higher, and the fuel consumption per unit output has little change under partial load or light load. (3) The start-up, load-carrying and shutdown time of diesel generator set are shorter. It can start at any time and is more suitable for emergency power supply. 4. Diesel generator set operation and maintenance is simpler and more convenient than turbo generator set. However, diesel generators also have some shortcomings: 1) only liquid fuel can be used, the fuel price is more expensive, so the cost of electricity is higher. (2) the diesel engine has large abrasion, short life and frequent maintenance. Operation stability and overload capacity are worse than steam power plant. (3) the vibration and noise of the unit are large and the operating conditions of workers are poor. 4. The magnetic pole surface of the generator must be equipped with a brake coil to facilitate the start and stop of the unit.
