AC excitation system and variable-speed control panel for pumped storage plants
Variable-speed control panel and AC exciter for pumped storage plants with adjustable rotational speed. The set works together with the variable-speed motor-generator and the pump-turbine. The controller is duplicated, and the exciter feeds the rotor through slip rings.
- Purpose
- control of a variable-speed pumped storage unit
- Input signals
- grid active and reactive power (voltage), turbine rotational speed
- Controller
- redundant, two high-speed calculation controllers
- Excitation
- AC converter feeding the rotor through slip rings
Price, availability and lead time on request. We help with analogue selection, customs clearance and delivery.
Description
The variable-speed control panel and the AC exciter form the basis of the control system of a pumped storage plant with adjustable rotational speed. The set is supplied together with the variable-speed motor-generator and the pump-turbine, and the joint operation of the unit with the power system depends on it. In pumping mode such a unit can regulate the power drawn from the grid, and in turbine mode it responds faster to load changes.
The control panel receives signals of grid active and reactive power (voltage) and of turbine rotational speed, calculates and issues control commands to hold the set values. It is responsible for the main regulation functions: changing the unit speed, independent control of active and reactive power, and automatic frequency regulation in pumping mode. The controller that performs high-speed calculations has a duplicated circuit of two controllers, so the unit continues operating if one of them fails.
The AC exciter feeds the three-phase winding of the cylindrical rotor with current of adjustable frequency through slip rings. This is what allows the machine to rotate at a speed different from the synchronous one and to raise the rotor current almost instantly during a grid voltage dip. The exciter and the controller are designed as one system, because the response speed of regulation depends on how well they are matched.
A variable-speed exciter has been supplied, among others, for the Takami plant (Hokkaido Electric). There a 105 MVA variable-speed motor-generator works with a 103 MW Deriaz diagonal pump-turbine. At the Okutataragi plant the rotor of a 350 MVA motor-generator was converted from a fixed-speed machine to a variable-speed one. Applications: new variable-speed pumped storage plants and conversion of existing fixed-speed units to variable speed.
The project requires data on the pumped storage scheme, including the unit rating and rated speed, the regulation range, grid parameters and operating mode requirements. The control panel is configured for these requirements, and the exciter is selected according to the rotor power. Next to them at the plant stand an excitation transformer and auxiliary main-circuit equipment. Speed regulation is verified on a rotating machine, so commissioning is carried out together with the unit.
Technical specifications
| Purpose | control of a variable-speed pumped storage unit |
|---|---|
| Input signals | grid active and reactive power (voltage), turbine rotational speed |
| Controller | redundant, two high-speed calculation controllers |
| Excitation | AC converter feeding the rotor through slip rings |
| Deliveries | Takami plant (Hokkaido Electric) |
Request a price and lead time
AC excitation system and variable-speed control panel for pumped storage plants. We reply within one business day.
Or email sales@usk.ua or call 044 339-50-20.
Questions and answers
What is included in the set for a variable-speed pumped storage plant?
The variable-speed control panel and the AC exciter. They are supplied together with the variable-speed motor-generator and the pump-turbine.
How does the exciter allow operation at a non-synchronous speed?
It feeds the three-phase winding of the cylindrical rotor with current of adjustable frequency through slip rings. Therefore the rotational speed can differ from the synchronous one.
Is the set suitable for converting an existing unit to variable speed?
Yes, at the Okutataragi plant the rotor of a 350 MVA motor-generator was converted from a fixed-speed machine to a variable-speed one. For the Takami plant the exciter was supplied for a 105 MVA unit.
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