Question

QUESTION 1

A) There are two input parameters which need to be manipulated when controlling a syn-
chronous generator. Name these and describe the output parameters each one controls when
the generator is i) stand alone, ii) connected to an in?nite bus.

B) Discuss the difference between forward and backwards synchronization as well as the dif?culties
which may occur with backwards synchronization.

Answer 1

A) Volatge and Frequency are the two ouput parameter which needs to manipulated when controlling a synchronous generator.

When system is in stand alone condition output volatge and frequency simply controlled by the prime mover’s speed but when synchronous generator is connected to a line, there are many factor influences the output voltage and frequency. For example there are two essential factors

• The output voltage of a generator will be reduced (droop) as the load increases.
• The prime mover’s speed will also be reduced (droop) as the load increases

Under load condition

Voltage droop can be controlled - As when load is connected the volatge drops and it seems counter productive . By using decoupling capacitor volatge drop can be prevented.

Frequency(speed) Droop Control- Changes in frequencies or speed seen as power output, will be reacted to by the generators and adjusted for, based on the droop control settings .

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Difficulties in synchronization

Generally a question is comes in picture "Why reverse synchronization is dangerous ? "

When synchronizing the generator and the system is settled already, so if there is a drop little bit, the generator will follow and adjust. But when we consider both the grid and generator are under some load the volatge and frequency of grid can not be adjusted and it can be adjusted by controlling the generator only. There is no sophesticated automatic mechanism is availble for this task so someone have to manually adjust it.