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Parallel Operation of Diesel Generator Set

Oct. 15, 2019

Most diesel generator sets are used in multiple generatorsets to increase load and automatically distribute load capacity, which can increase the power supply capacity. It is a suitable and economical method. So what is the concrete concept and function of diesel generator set merger?

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The Concepts of Diesel generating Sets Parallel Operation


It is a measure to save the cost and increase the power supply capacity by combining several running generators together to form a large capacity power supply to the load or to supply the power to the power grid together. A system for generating two or more generating units to supply power to the load when the power supply is needed in the event of a power failure. When the load is less than 60% (adjustable) of the rated capacity of a single generating set, the system will send out a "subtraction" signal, unload the reserve into the generator set and disassemble the automatic shutdown. If the load is more than 80% (adjustable) of the rated capacity of a single generator, the system automatically sends out the "booster instruction", the standby generator set starts automatically, and after the automatic synchronization, the power load is automatically distributed equally. The operating conditions of the parallel machine are same voltage, frequency and phase of the two machines.

The function of parallel operation between diesel generator set 


Improve the reliability and continuity of power supply system. Since multiple generator sets are connected into a single grid, the voltage and frequency of the power supply are stable and can withstand the shock of large load variation.

Maintenance. Maintenance is more convenient. Multiple units in parallel use, can centralized dispatch, distribution of active and reactive load, can make maintenance, maintenance convenient and timely.

More economical. According to the size of the load on the network, a suitable number of small power units can be put in order to reduce the fuel oil and oil waste caused by the small load operation of the large power unit.

Future expansion is more flexible. We only need to install the power generation and parallel equipment, and when the company needs to expand the power network capacity, we can add the generating units, and can easily realize the expansion of the unit, so that the initial investment is more economical.



Once the external power supply is interrupted, the diesel generator set should be started automatically to play the role of emergency power supply. What are the three starting modes of diesel generator set in automatic mode?



Boot according to demand


In automatic mode, when the on-off input port is effective, the module with the highest priority starts first. When the load is greater than the maximum percentage set by the module, the sub-priority module starts up and synchronizes. Average load distribution.


When the load is less than the minimum percentage of the downtime set by the module, when the sub-priority module is delayed, the switch and heat dissipation stop.


The sub-priority module is turned on when the load generating set is shut down.


Full boot

In the automatic mode, when the on-off input port is effective, all the modules are turned on, first the module with load condition is closed first, and the other modules, after the load condition is reached, synchronize one by one. Then the module detects the load, and when the load is less than the minimum percentage of the downtime set by the module, the module with small priority is delayed, and the switch and heat dissipation stop.


When the load is greater than the maximum percentage set by the module, all the remaining unpowered generating units are automatically turned on.


When the load generating set is stopped, all the remaining unturned-on generating units are automatically turned on.



Balanced engine running time

In automatic mode, the generator set with small engine running time will start up first when the switch input port is remotely started with load (according to demand).


When the operating time of the generating set with load is longer than that of the equalized engine set by other generating units, the other units are scheduled to start up (can start according to the demand, all the two modes), and the other units synchronize and merge. Open and unload your own downtime.


All generators turn on and off in turn according to the running time of the equalization engine.


When a diesel generator works in parallel, it often occurs that the load current cannot be balanced distribution, or that the current and power oscillate periodically, which results in the instability of rotational speed, voltage and path. That is, the generator can not work in parallel stably. For such problems, electricians tend to think that they are caused by mechanical causes of diesel engines, while crew members think that they are caused by electrical equipment. And both parties can prove that the relevant part of each unit is normal in performance. In this way, the problem is difficult to solve because of the lack of clear analysis of the fault cause and the mutual prevarication. It should be pointed out that the mechanical and electrical properties of most diesel generators with poor parallel performance are good when they are operated separately. This show that the problem is caused by the establishment of a certain relationship after the parallel connection of the generator set. Therefore, when analyzing these problems, we must start with the cooperation of the characteristics and parameters of the parallel gensets. All the same time, the factors that affect the parallel operation of generator sets are often ignored or considered irrelevant when the gensets are used separately.



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