GE EX2100e Excitation System Complete Guide

GE EX2100e Excitation Regulator System: Architecture Analysis and Engineering Application Guide

In the field of excitation control in power plants, GE's EX2100e series, as the fourth generation digital excitation control system, is widely used in the construction and renovation projects of steam turbine, gas turbine, and hydro generator units. This article is aimed at on-site engineers and system integrators, providing an in-depth analysis of the hardware architecture, control software core functions, redundant configuration, technical specifications, and engineering application points of the EX2100e 35A/120A regulator system. It helps readers quickly locate problems and optimize system operation during debugging, maintenance, and troubleshooting.

System Overview and Application Scenarios

EX2100e is the fourth generation digital excitation control platform launched by GE based on over 40 years of engineering experience in over 6000 sets of thyristors and excitation systems worldwide. Prior to this, over 4000 sets of GE's first and second generation digital excitation equipment were in operation in 60 countries worldwide. EX2100e is not only suitable for new units, but also optimized for the renovation of old units. It can seamlessly integrate with various on-site equipment, including:

Saturated Current Transformer/Power Potential Transformer (SCT/PPT) Excitation System

brushless excitation system 

DC Rotating Excitation System

This system can effectively "desensitize" the influence of the excitation machine time constant, and improve the response speed to the transient process of the system by directly measuring the generator magnetic field voltage and current.

Engineering value: For renovation projects, EX2100e supports bulk shipping and on-site cabinet assembly, allowing for Modbus communication with the original DCS system ® Ethernet or serial communication integration greatly reduces the difficulty of renovation and downtime.

Deep disassembly of hardware architecture

2.1 Power Conversion Module (PCM)

Both 35A and 120A systems use IGBT based pulse width modulation (PWM) power conversion modules. PCM integrates six IGBTs internally to form a three-phase inverter bridge. In practical applications, two IGBTs are used to generate the DC PWM output required for excitation, and the third IGBT, in conjunction with an external dynamic discharge (DD) resistor, quickly releases the energy of the DC bus capacitor during load transients or unit trips to prevent overvoltage.

Input power characteristics:

35A system: Main AC input 90-280V rms, maximum frequency 480Hz (can come from permanent magnet generator PMG, plant bus or generator terminal)

120A system: Main AC input up to 480V rms

Backup DC input: 125-250V DC (station battery), isolated by diodes and connected in parallel with rectifier bridge output

Output capability:

35A system: 250V DC/35A DC continuous output, strong excitation capability can reach 210% (i.e. 73.5A)

120A system: 250V DC/120A DC continuous output, strong excitation 252A

Engineering Tip: At the renovation site, if the original excitation system is powered by PMG, its 480Hz, three-phase output can be directly connected to EX2100e. If energy needs to be taken from the generator end or plant power, an input PPT (power potential transformer) must be configured for isolation and voltage reduction.

2.2 Dual Controller Redundancy (Warm Backup)

For units with high reliability requirements, EX2100e provides hot standby (WBU) configuration:

Includes two completely independent controllers (M1 controller one and M2 controller two) and their respective PCMs

Each controller has built-in automatic/manual adjustment function

Determine which set of bridge arms is currently supplying power to the excitation winding through the output selection module (SCM or TCM)

During normal operation, the active bridge receives trigger commands from the current active control, and the trigger loop of the backup bridge is disabled

When the activity control self diagnosis detects a fault or operation failure, it can automatically switch to backup control and power bridge without disturbance

Bidirectional disturbance free switching: The operator can manually select the active bridge, and the switching process does not affect the excitation output. This provides great convenience for online maintenance.

2.3 Control cabinet and environmental adaptability

The standard control cabinet is NEMA 1/IP20 or IP21, installed on the floor indoors, with an optional IP54 protection level. In terms of size:

Standard cabinet: 800 × 2290 × 830 mm (width × height × depth)

35A simple cabinet: 610 × 2286 × 508 mm

Environmental requirements:

Working temperature 0~40 ℃ (derating should be considered at 50 ℃)

Meet the seismic requirements of IBC 2006/Universal Building Code Zone 4

Compliant with UL508C, CSA 22.2 No.14, OSHA, and the EU EMC and Low Voltage Directive

Installation suggestion: In high temperature, dusty or vibrating environments, IP54 cabinets should be selected, and ensure smooth air intake at the bottom and exhaust at the top of the cabinet. If the ambient temperature remains above 40 ℃ for a long time, the rated output current should be reduced according to the derating curve provided by GE.

Control software and core functional modules

The control software of EX2100e is controlled through ToolboxST ™ Perform configuration, loading, and debugging. The software uses Function Block Diagram (FBD) to display signal flow, and all control, restriction, and protection functions are presented in modular form.

3.1 Signal acquisition and preprocessing

The voltage and current signals of the PT/CT at the generator end are connected to the ESYS (EX2100e system interface board), which completes signal isolation, filtering, and scaling. The controller synchronously samples the AC waveform at high speed and calculates the following key variables through mathematical algorithms:

Terminal voltage, active current, reactive current

Frequency and slip (reflecting changes in rotor speed)

Power, reactive power V/Hz、 Power factor, magnetic flux amplitude

3.2 Automatic Voltage Regulator (AVR) and Manual Regulator

AVR: Maintain a constant voltage at the generator terminal during normal operation, responding to changes in load and operating conditions.

Manual regulator (FVR/FCR): When PT is disconnected or AVR fails, the manual regulator directly controls the excitation voltage or current. The GE standard uses FVR (Field Voltage Regulator) instead of FCR (Field Current Regulator) because FCR weakens the signal independence of the over excitation limiter.

Tracking mechanism: The inactive regulator automatically tracks the output of the active regulator through a software ramp function, ensuring no disturbance during switching.

3.3 Key limiters and protection functions

Function Name Function Description

Over excitation limiter (OEL) prevents long-term overcurrent of magnetic field, complies with ANSI C50.13 standard, and adopts inverse time limit curve

Underexcitation limiter (UEL) limits the demand of AVR for underexcited reactive current, avoiding exceeding the static stability limit or overheating of the stator core end

When the stator current exceeds the rated value, the AVR automatically switches to the preset reactive power control mode

V/Hz limiter and protection limit V/Hz ratio (typical value ± 5% rated), exceeding 1.10 p.u. inverse time limit alarm, 1.18 p.u. delayed tripping for 2 seconds

PT disconnection detection (PTFD) detects feedback voltage loss, issues an alarm, and switches to manual regulator (if a disconnection is detected and there is no single-phase fault, the system first forces the output to the top value for 0.5 seconds before switching)

Generator overvoltage trip (59G) monitoring terminal voltage, triggering trip when exceeding the set value

Demagnetization protection (40) based on impedance and reactance two zone timed tripping

Engineering application scenario: When the hydrogen pressure of a hydrogen cooled generator changes, the hydrogen pressure/temperature compensation function will automatically adjust the parameters of UEL, OEL, and stator current limiter to avoid misoperation.

3.4 Power System Stabilizer (PSS)

The PSS of EX2100e adopts a multi input scheme, which comprehensively utilizes the active power and internal frequency (approximate rotor speed) of the synchronous motor to generate a signal proportional to the rotor speed. This signal is obtained by integrating the acceleration power and effectively attenuating the shaft torsional vibration signal, thereby improving the dynamic stability of the power system.

3.5 Reactive Power Compensation and Line Drop (RCC/Line Drop)

RCC mode: Achieving balanced distribution of reactive current between parallel connected groups

Line Drop mode: provides better voltage regulation for a certain point downstream of the generator bus

3.6 Generator Simulator (GEN SIM)

As a detailed generator model built into the software, GEN SIM can be configured to match the actual generator characteristics. During the shutdown of the unit, it can be used for operator training, testing of regulator and limiter functions, and verification of protection logic.

3.7 Communication and Integration

Unit Data Highway (UDH): Based on the EGD protocol, it connects the excitation system with the turbine control system HMI、 Data center, supporting ToolboxST configuration and maintenance

DCS interface: Supports Modbus RTU/TCP over Ethernet 10/100baseT, can receive lifting commands and data

Integration with Mark VIe: When the excitation system is coordinated with the GE Mark VIe turbine control system, VAR/PF control is typically implemented on the turbine side

Engineering Practice: Debugging, Testing, and Troubleshooting Approach

4.1 Factory testing and on-site witnessing

Each EX2100e undergoes routine testing before leaving the factory:

Circuit continuity check

Dielectric (withstand voltage) test (compliant with IEEE 421 standard)

All component functionality verification

Customers can choose:

Option A (free): Check appearance and craftsmanship, review engineering and testing documents

Option B (chargeable): Witness hardware and software demonstrations on-site

Suggestion: For critical units, it is recommended to choose option B, familiarize yourself with the operating interface in advance, and verify the customized logic.

4.2 Common on-site problems and solutions

Communication failure (EGD/Modbus)

Check Ethernet physical connection and switch configuration

Confirm if the IP address, port, and data mapping table are correct

Monitor UDH status words using ToolboxST

PT disconnection false alarm

Verify PT secondary circuit wiring and insurance

Confirm PTFD parameter settings (such as detection threshold, delay)

If the generator is not connected to the grid, the PTFD function can be temporarily disabled, but it needs to be restored before grid connection

Frequent overexcitation restriction actions

Check if the actual excitation current exceeds the OEL curve setting

Verify the calculation of generator magnetic field temperature (through field voltage/current ratio)

If the system operates at the edge of strong excitation for a long time, it should be considered to increase the OEL setting value or improve reactive power balance

V/Hz protection tripping

Check the frequency change rate during the start stop process of the unit

Adjust the setting value of the V/Hz limiter (typically 1.05~1.10 p.u.)

Attention: At the moment of load shedding or disconnection of the unit, V/Hz may exceed the limit instantaneously, and a reasonable delay should be set to avoid false tripping

Dynamic discharge (DD) resistor frequently activated

Check if the DC bus voltage frequently exceeds the set threshold

Confirm whether the DC contactor in the demagnetization circuit is opening and closing normally

Assess whether there are frequent demagnetization operations or load fluctuations on site

4.3 Spare parts management and lifecycle

Due to the fact that EX2100e is based on IGBT technology (fourth generation), compared to old-fashioned SCR excitation, its power module has a longer lifespan and lower maintenance requirements

Suggest keeping key spare parts on hand: one PCM, one ESYS board, one UCSB controller, and one set of DD resistors

Regularly (every 5 years) conduct capacity tests on the DC bus capacitor and replace it if necessary

4.4 Interface precautions with old systems in renovation projects

If the original excitation system uses PMG power supply, confirm that the PMG frequency is compatible with EX2100e (≤ 480Hz)

If the original system uses a DC battery as a backup power source, the voltage should be within the range of 125-250V dc

For SCT/PPT excitation mode, EX2100e can directly replace the original SCR control cabinet, but the excitation transformer parameters need to be reconfigured

Communication with DCS: It is recommended to use Modbus TCP, and address mapping can be customized through ToolboxST

Technical Specification Quick Reference Table

Project 35A System 120A System

Main AC input range: 90-280V rms, maximum 480V rms

Input frequency ≤ 480Hz ≤ 480Hz

DC backup input 125-250V DC 125-250V DC

Rated output 250V DC/35A 250V DC/120A

Strong motivation ability 210% (73.5A) 210% (252A)

IGBT switching frequency is approximately 1000Hz

Control cabinet size 610/800mm wide, optional 800mm wide

Protection level IP20/IP21 (optional IP54) IP20/IP21 (optional IP54)

Environmental temperature 0~40 ℃ (50 ℃ derating) 0~40 ℃ (50 ℃ derating)

Applicable standards UL508C, CSA22.2, EN50178, IEEE421 series are the same as the left