PARALLEL OPERATION OF ALTERNATORS

Alternators are connected in parallel to
(1) increase the output capacity of a system beyond that of a single unit,
(2) serve as additional reserve power for expected demands, or
(3) permit shutting down one machine and cutting in a standby machine without interrupting power distribution. When alternators are of sufficient size, and are operating at different frequencies and terminal voltages, severe damage may result if they are suddenly connected to each other through a common bus. To avoid this, the machines must be synchronized as closely as possible before connecting them together. This may be accomplished by connecting one generator to the bus (referred to as bus generator), and then synchronizing the other (incoming generator) to it before closing the incoming generator’s main power contactor. The generators are synchronized when the following conditions are set:

1. Equal terminal voltages. This is obtained by adjustment of the incoming generator’s field strength.

2. Equal frequency. This is obtained by adjustment of the incoming generator’s prime-mover speed.

3. Phase voltages in proper phase relation.

Eigen Value Theory

Eigen values tell us the exponential part of the solution of the differential equation system
Three possible values for an eigen value :
1) Positive value: system will increase exponentially
2) Negative value: system will decay exponentially
3) Imaginary value: system will oscillate (note combinations of the above are possible)

NOTE:
Eigen values close to imaginary axis dominated on other value which is far from imaginary axis. Eigen value close to imaginary axis affect the system response.

Effect:
· If any eigenvalue has a positive real part, the system will tend to move away from the fixed point.
· If the real component of at least one eigenvalue is positive, than the system is unstable.
· If there are imaginary eigenvalue components with real positive component than the response will oscillate.
· Stability of linear dynamical systems can be determined from eigenvalues.
· Stability of nonlinear dynamical systems can be locally evaluated using eigenvalues.

Interact with Scope figure properties-Change the colour of background of scope

The ability to interact with Scope figure properties is not available
because the handle of the Scope figure is not turned on. To turn the
handle of your Scope figure on, and show the menus, type the following
at the MATLAB command prompt (after opening the Scope figure):

shh = get(0,'ShowHiddenHandles');
set(0,'ShowHiddenHandles','On')
set(gcf,'menubar','figure')
set(gcf,'CloseRequestFcn','closereq')
set(gcf,'DefaultLineClipping','Off')
set(0,'ShowHiddenHandles',shh)

This will allow you to manipulate your Scope figure just like any
other MATLAB figure, allowing you to make changes such as
- Background/foreground color
- Line color
- Add text or a legend
- Add a print icon
- Print the graph