One of the most popular applications of capacitors in industrial electrical engineering is to provide power factor correction. The capacitors store energy and release it every cycle on an AC power distribution network to compensate for the fact that highly inductive loads such as electric motors draw a current which 'lags' behind the applied voltage. This results in poor power factor on the electrical distribution network, which typically means that network assets can not be utilized to their apparent power rating.
By using power factor correction, which for inductive loads means switching capacitors into the supply network, the power factor can be increased close to unity which means network assets such as large transformers don't need to be unnecessarily over sized.
Also, most electrical supply authorities will penalize users who have very poor power factor, since they usually bear the additional cost of over sized & under-utilized distribution assets. There is therefore a financial incentive for large industrial users to install power factor correction equipment.
Capacitors are also used to filter out the ripple when rectifying AC power to DC (eg: in the input stage of a variable-speed drive or inverter circuit).
Also, capacitors are used to 'amplify' DC power supplies (eg: to convert a 5VDC power supply to output 9VDC). These are called 'chopper' circuits.