The Challenge

Industrial plants with on-site power generation depend on synchronous generators to supply stable electrical power to their internal distribution network and, in many cases, to export power to the external grid. The excitation system is the key control element that determines a generator's terminal voltage and reactive power contribution. Without precise excitation control, terminal voltage fluctuates in response to load changes, threatening the integrity of the plant's electrical supply and the generator's compliance with grid connection requirements. Inadequate excitation control also reduces the generator's fault ride-through capability and limits the operator's ability to contribute reactive support during grid disturbances.

The ANDRITZ Solution

ANDRITZ designs and supplies complete excitation systems for synchronous generators in industrial plants, co-generation facilities, and hydropower installations. Each system is engineered to the specific generator rating, application, and grid connection requirements of the installation. The core of the ANDRITZ excitation system is a digital Automatic Voltage Regulator (AVR) that continuously measures terminal voltage and adjusts field current output to maintain the generator at the specified operating setpoint — under all load conditions and across the full reactive power operating range.

How It Works

The excitation system supplies direct current to the generator's rotor field winding through a static thyristor rectifier or rotating exciter configuration, depending on the generator design. The digital AVR processes real-time measurements of terminal voltage, current, and reactive power to calculate and apply the correct field current command. In voltage regulation mode, the AVR maintains terminal voltage at setpoint while the generator absorbs or delivers reactive power within rated limits. The system can also operate in reactive power or power factor control mode, depending on the requirements of the active grid connection agreement. Protection functions integrated within the AVR safeguard the generator against field overcurrent, loss of excitation, and underexcitation conditions.

Key Benefits

Digital AVR technology provides precise, stable voltage regulation across the full operating range, reducing voltage fluctuations that can affect sensitive plant equipment and production processes. Integrated protection functions reduce the risk of generator damage from overexcitation, loss of field, and other fault conditions. Configurable control modes allow operators to select voltage regulation, reactive power, or power factor control to meet grid operator requirements. ANDRITZ engineering and commissioning support ensures the excitation system is configured to the specific generator and network characteristics of each installation.

Integration & Compatibility

ANDRITZ excitation systems are designed to interface with the plant DCS, power management system, and protection relay infrastructure. Communication interfaces support integration with turbine governors, generator protection relays, and synchronisation systems for coordinated generator management. Remote monitoring capabilities can be configured to support online supervision of excitation performance and field current status from plant control rooms.