Control of emergency diesel generators not only maintains stable operating conditions, but also maximizes the thermal efficiency of emergency diesel generators and minimizes the release of toxic substances from the engine.




* A Thesis submitted to the committee of Graduate School, Chungnam National University in a partial fulfillment of the requirements for the degree of Master of Engineering Conferred in February 2019.
The purpose of this paper is to develop a computerized model of an emergency diesel generator control system and verify the validity of the model through simulation.
The Emergency Diesel Generator is a diesel engine driven synchronous generator. In case of Loss of Outer Power (LOOP) or Safety Injection (SI), the Emergency Diesel Generator is supplies power to an independent bus (Safety Bus, Class 1E bus). The safety bus is connected to the load by the pump drive motors to cool the reactor. At the moment when each pump is started, a transient state occurs due to the load variation, and the stabilizing characteristics are changed according to the performance of the controller. At this time, governor controls frequency (rotational speed) and active power, and generator output voltage and reactive power are controlled by exciter.
The limits for the emergency diesel generator performance in transient conditions are regulated by the US NRC (Nuclear Regulatory Commission) Reg. Guide 1.9, and the controller should be properly tuned to comply with applicable regulations.
The characteristics of the output signal obtained during the above process can be used as reference data (base line) of the governor setting in the future, and this method has the following advantages.
First, stable power can be supplied to the safety bus (Class 1E Bus) that supplies power to the engineered safety feature, ensuring reactor stability. Second, the acceptance criterion of the control variable becomes clear, so that it is possible to perform a good tuning irrespective of the human factor. Third, the performance of the system can be optimized and the damage of the system can be reduced. Fourth, if the governor is urgently replaced, the test operation procedure can be simplified. Fifth, there is no need to carry out the test after maintenance. Sixth, it can save considerable time. Seventh, since the characteristic signal in the steady state is secured, the operating state of the governor itself can be quickly determined when a problem occurs. Eighth, it can be implemented as commercial equipment without special equipment.