ABB PCS8000 AC Excitation SYSTEM DRIVES

ABB PCS 8000 AC Excitation

Introduction and Main Technical Features

Pumped Hydro Energy Storage Plants have an essential role in electric power grids. They provide spinning reserve and permit the

operation of base load power plants at their optimal efficiency by consuming power during low load times to pump up the water to

the reservoir at higher altitudes.

Customer’s challenge

A drawback of conventional Pumped Hydro plants with pumpturbines

is the operation at constant speed when the motorgenerator

is a synchronous machine. This results in a lower

than necessary overall efficiency because the design allows for

one optimized operation point only. The reasons are: Optimal

speed for pumping is higher than optimal speed for turbining

and speed adjustment to adapt to varying heads is not possible.

An additional drawback is that power/frequency control is not

possible in the pumping mode. The possibility of speed

adjustment eliminates those drawbacks.

Solution

Using a wound rotor induction machine for the motorgenerator

and controlling the slip frequency of the rotor with a

power electronics converter makes the necessary speed

variation possible. Operation at maximum hydraulic efficiency

is enabled in both, turbining and pumping mode, over a larger

range of head variation and power/frequency control is possible

in the pumping mode as well. Since the power needed in the

rotor is only a fraction of the machine rating (roughly

proportional to the slip), the rating of the converter and

therefore its cost as well as its space demand is minimized.

Because of the semiconductor loss optimizing design of the

PCS 8000 it is the ideal converter for this kind of application.

Benefits