Why Is a Synchronous Generator Used for Generating Electricity

There are a few reasons why synchronous generators are used to supply electric power

Constant Voltage.

Constant frequency.

Capability to deliver active as well as reactive power.

Appropriate synchronization between all alternators to an infinite bus bar (V=1<0 p.u constant).

Various generators from across the country synchronize with this infinite bus which can supply electric power from anywhere in the country. This has flexibility to increase the number of generating units synchronized with the infinite bus bar.

On the other hand if we use induction generators instead of synchronous generators, there will be two aspects

Reactive power requirement of I.G

2. Harmonic content in output power spectrum.

The I.G requires reactive power for its operation which needs to be provided either by capacitor banks or I.G. units must be connected to a stable grid where reactive power is available. If we use I.G’s for generation of electric power we will have severe active and reactive power issues and hence voltage will have imbalance. If we have to install capacitor banks, there will be huge costing in installation of these equipment s.

The output frequency of Induction Generator is variable which will create uncertainties in deciding ratings for electric equipment and load side equipment will have problems with varying frequency. To deal with this we need to convert Variable AC power to DC power and back to Fixed frequency AC power using power electronic equipment which induces high amount of harmonic content in output spectrum which is undesirable and design of Harmonic filters and their implementation will increase cost.

Hence Synchronous Generator is used to supply power which are mainly large generation units like thermal, hydro, nuclear and Gas power plant etc. Induction Generators are installed mainly in wind power plants and small hydro power plants.

Synchronous generators unlike induction generators have the capability to produce both active power and reactive and they have armature on stator so it is easy to collect power from them can be designed for high voltages. They remain synchronized with the bus and other alternators too and thus we have one common working frequency and one common voltage as that of bus. If induction generators were being used there would be problem of speed differences in generators working in parallel and thus of voltage produced thus causing disbalance in the generation unit.