ABBPCS 8000 AC Excitation AC Excitation for hydro pump energy storage plants

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. 

ABB

ABB Switzerland Ltd

Advanced Power Electronics 

CH - 5300 Turgi, Switzerland 

Tel.: +41 58 589 32 35

Fax: +41 58 589 26 18 

E-Mail: pes@ch.abb.com 

Internet: www.abb.com/powerelectronics 

Benefits 

9 Operation at optimal efficiency in turbine and pump 

mode 

9 Speed adoption to varying heads for additional 

efficiency improvement 

9 Enabling power/frequency control during pumping 

operation 

Reliability runs in the family 

The PCS 8000 AC Excitation is a further development of 

ABB’s PCS 6000 family which are used for a wide range of 

applications. The standardization of these power electronic 

modules delivers substantial advantages in terms of cost and 

quality. 

MV converter 

PCS 8000 converter units are based on three-level IGCT phase 

modules. The IGCT (Integrated Gate Commutated Thyristor) is 

the state-of-the-art semiconductor element for this power 

range. The converter units are connected by a medium voltage 

DC link (intermediate circuit). The converter modules are 

water cooled with a virtually maintenance free closed loop 

water system equipped with redundant circulating pumps. 

Key facts 

Application: AC Excitation 

Type: PCS 8000 AC Excitation 

Installation: Indoor or Container 

Nominal output power: project specific 

Nominal frequency: 50 / 60 Hz 

Nominal voltage: project specific 

Ambient temperatures: -25 … 40 °C