Series were initiated to solve voltage flicker include;

Series capacitors

In a circuit, series capacitors are connected in series and
this feature makes it possible to carry the full line current. Series
capacitors play an important role in transmission and distribution line
compensation. The voltage rise across the capacitor acts like a voltage
regulator as it is a function of the circuit current. Such effects are
necessary in radial feeders to lower the voltage drops and flicker effects. If
series compensation goes is used, it increases the power transfer capability. (Natarajan, 2005, p. 155)

Some of the old methods that were initiated to solve voltage
flicker include; upgrading the system voltage, re-conducting the feeder,
getting a new feeder or installing other compensating equipment. Hence this
makes a series capacitor a solution to the flicker problem.  The inductive reactance feeder is cancelled
out by or nullified by the capacitive reactance of the series capacitor. (Natarajan, 2005, p. 159)

Series capacitors in transmission lines are used to increase
power transfer capability. They are lso used to adjust the stability in the
system of long transmission lines. In overall this helps with the increase of
maximum power. (Natarajan, 2005, p. 165)

Series capacitor also offers a means of smooth current flow
in arc furnace power as the current in used in the melting process is not
stable. (Natarajan, 2005, p. 175)

They are also used for voltage regulation in stand-alone
generators and can be used in coal and mining industry to maintain voltage at
the remote end. (Natarajan, 2005, p. 176)

Shunt Capacitors

An amplifier is needed at times to have a certain or
specific cutoff frequency. A shunting capacitor can be used at the output of a
selected emitter circuit to select the upper frequency. (Bell, n.d.)

Shunt capacitors improve voltage regulation in the sense
that they are fixed to a bank that can be switched on and off with varying
feeder load conditions. (Beaty, 1998, p. 101)

Shunt Reactors

Shunt reactors control the over voltages under no load,
light load and load reaction, this is achieved by compensation of the
capacitive line charging current. Shunt reactors also control the switching
over voltages to some extent. (Limited, 1987)

Ferranti Effect

This is found in transmission lines where by the open line
receiving end voltage is more than the sending end voltage. This processes of
voltage rise at the receiving end on an open line is known as the Ferranti
Effect. (Bandyopadhyay, n.d.)

It is important not to keep open the receiving end of a
transmission line due to Ferranti effect. This is because the receiving end
voltage is found larger or more than the sending end voltage at the open
circuit condition, the terminal equipment may be subjected to high voltage.