ABB UNITOL 1010/1020 AVR Compact IGBT Automatic Voltage Regulator

ABB UNITOL 1010/1020 Automatic Voltage Regulator: A Practical Guide to the Whole Process from Selection and Debugging to Grid Compliance

In many fields such as distributed generation, ship electric propulsion, diesel locomotives, and wind power, the voltage stability of synchronous generator sets and electric motors directly determines the power supply quality and equipment safety of the power system. As the core of the excitation system, the performance of the automatic voltage regulator (AVR) not only affects the regulation accuracy of the terminal voltage, but also relates to the dynamic response and fault ride through capability of the unit's grid connected operation. ABB UNITROL ®  The UNITROL 1010 and 1020 in the 1000 series are highly integrated and reliable AVR solutions tailored for small and medium power applications.

This article will delve into the hardware architecture, software function package (LIGHT/BISIC/FULL) selection strategy, on-site installation and wiring points, practical skills in using CMT1000 debugging tools, and common troubleshooting methods of UNITROL 1010/1020 from the perspective of frontline engineering personnel. The aim is to provide a detailed technical reference for engineers engaged in generator maintenance, power station debugging, and electrical transformation.

Product positioning and selection: UNITOL 1010 vs 1020 vs PM40

The UNITOL 1000 series is a product family launched by ABB for low-power excitation applications, setting new industry benchmarks in functionality, reliability, and connectivity. Among them, UNITOL 1010 and 1020 are the latest members of the family, sharing the same mechanical installation dimensions and interface definitions, but with significant differences in output capabilities and software functional support.

1. UNITOL 1010: Economical and Compact Selection

Excitation output capability: At an ambient temperature of 55 ℃, the continuous output current is 10 A DC, and the overload can reach 20 A DC for 10 seconds.

Applicable scenarios: small diesel generator sets, small hydropower, synchronous motors that require basic voltage regulation functions.

Software package support: LIGHT (standard) BASIC、BASIC+SYNC。 Note: The FULL version is not applicable to 1010.

Core advantage: Ideal for cost sensitive applications, providing necessary regulator modes (AVR/FCR/PF/VAR) and limiter functions.

2. UNITOL 1020: High Performance Expansion Platform

Excitation output capability: Continuous 20 A DC at 40 ℃, continuous 15 A DC at 55 ℃, and can reach 40 A DC after 10 seconds of overload.

Applicable scenarios: Diesel/gas/steam turbines, water turbines, ship propulsion and auxiliary systems, and traction locomotives that require higher excitation currents.

Software package support: LIGHT, BASIC, BASIC+SYNC, FULL, FULL+PSS. Provide complete control functions.

Core advantage: Through the external power module PM40, the continuous output current can be extended to 40 A DC (55 ℃), with an overload of 80 A DC, covering a wider range of industrial needs.

3. UNITROL 1000-PM40: Power Expansion Module

When the application requirements exceed the 20A output capacity of the UNITOL 1020 body, a PM40 power module can be installed.

PM40 accepts three-phase AC input (0-250V AC) or DC input (0-300V DC), outputs 40 A DC continuous current (55 ℃), and is overloaded for 10 seconds with 80 A DC.

This module communicates seamlessly with UNITOL 1020 via CAN bus for seamless expansion.

Key points of engineering selection:

During the project design phase, engineers should first calculate the excitation current (Ifn) and peak current required for the generator rotor. If Ifn ≤ 10A, UNITROL 1010 can be used; If Ifn is between 10A and 20A, priority should be given to using UNITOL 1020; If Ifn is between 20A and 40A, the combination of UNITOL 1020+PM40 needs to be selected. At the same time, it is necessary to consider the impact of environmental temperature on the output capacity reduction - in a high temperature environment of 55 ℃, the 1020 body can only output 15A, and sufficient margin needs to be left.

Hardware architecture and interfaces: designed specifically for harsh environments

The UNITROL 1010/1020 adopts a separate communication and control processor architecture, which separates control tasks and communication tasks for processing, improving real-time performance and reliability. Its non-volatile flash memory can store event logs and data logs, facilitating fault analysis and quick troubleshooting. It is worth mentioning that the device supports supplying power to the controller through a USB interface, which means that even in the absence of external input power (such as generator shutdown, PT no output), engineers can connect to the computer for parameter configuration or firmware upgrade.

1. Power supply and power input

Excitation power input: three-phase AC, 0-300V AC (maximum sine wave), or DC input 0-420V DC. Usually sourced from permanent magnet generators (PMGs), auxiliary windings, or composite power sources.

Auxiliary power supply (controller power supply): three-phase AC 9-300V, single-phase AC 16-300V, or DC 18-420V. This power supply provides energy for control circuits, communication interfaces, and IGBT drivers. The wide voltage range design enables it to adapt to various start-up and transient conditions.

2. Measure input

Terminal voltage (1, 2 or 3 phases): up to 500V AC (direct input, no PT required).

Network voltage (1-phase): up to 500V AC, used for synchronization or voltage matching.

Terminal current (1 phase): 1-5A AC, usually taken from the CT secondary side, used for reactive power droop compensation and power factor adjustment.

Frequency range: 10-150 Hz, covering various speeds from low-speed water turbines to high-speed gas turbines.

3. Control input/output

Analog I/O: 3-channel input (impedance>240k Ω), 2-channel output (impedance 100 Ω), ± 10V range. Can be configured as external input, PID superposition control, additional limit signal, etc.

Digital I/O: 4 dedicated inputs, 8 configurable inputs/outputs. The digital output has a maximum current of 150mA and can directly drive small relays. Additionally, provide a 24V/600mA output for external relays.

Reference voltage output: ± 10V reference, can be used for external potentiometers or sensors.

4. Communication interface

Ethernet： 10/100 MBit/s， Used for connecting CMT1000 debugging tools, Modbus TCP (BASIC and above versions), or system integration.

USB: Supports 1.0/1.1/2.0, cable length<3m, can be used for power supply and configuration.

RS485: configurable baud rate, cable length<500m, supports Modbus RTU or VDC communication. VDC mode allows up to 31 units to achieve reactive load sharing during islanding operation.

CAN: Only used for communication between internal devices of UNITOL 1000 series (such as dual channel configuration or connection with PM40 module).

5. Local Human Machine Interface (HMI)

The device panel is equipped with a local HMI that can display key parameters such as AVR status, voltage, current, frequency, etc. in real time, and can perform basic settings. This is very helpful for rapid on-site inspections and fault diagnosis.

Installation precautions:

The UNITROL 1010/1020 can be directly installed on the generator (end of machine installation) due to its wide temperature range (-40 to 70 ℃) and robust mechanical design (meeting IEC 60068-2-6 vibration level, DNV B level, seismic level 2), ensuring reliability in harsh environments.

When wiring, the power terminal and measurement terminal are physically separated from the I/O connector, which improves electromagnetic compatibility (EMC) immunity. It is recommended to use spring crimping terminals (provided with the equipment) to ensure reliable wiring and quick replacement.

For applications that require dual channel redundancy, such as critical ships or power stations, two UNITROL 1020 can be connected via CAN bus to achieve automatic switching between primary and backup channels. In the event of a primary channel failure, it can switch to the backup channel without disturbance.

Control software function package: in-depth analysis from LIGHT to PSS

ABB provides three ready-made software feature packages and an optional PSS (Power System Stabilizer) for the UNITOL 1000 series. Engineers should select appropriate functional packages based on project grid specifications, unit importance, and budget.

1. LIGHT version (standard on 1010 and 1020)

This version covers basic excitation control functions and is suitable for cost sensitive scenarios that do not require advanced features.

Regulator mode (disturbance free switching):

Automatic Voltage Regulator (AVR): maintains a constant terminal voltage.

Excitation Current Regulator (FCR): Manual mode, maintains constant excitation current.

Power factor regulator (PF): maintains a specified power factor.

Reactive Power Regulator (VAR): maintains specified reactive power output.

Limiter: Ensure that the synchronous machine operates within a safe and stable area.

Excitation current limiter (minimum/maximum)

P/Q under excitation limiter

Stator current limiter

V/Hz (volts/hertz) limiter

Terminal voltage limiter

Soft start and voltage matching.

2. BASIC version (added on top of LIGHT)

Modbus TCP: Implement standard communication with the upper computer system through Ethernet, facilitating data acquisition and control.

Rotating diode monitoring: For brushless excitation systems, this function can monitor the health status of the rotating rectifier and predict faults.

Analog input connected to PID summation point: allows external signals (such as reactive power settings from the power plant controller) to be superimposed on the PID regulator to achieve higher-level control.

VDC mode: In islanding operation, up to 31 units can automatically distribute reactive load through RS485.

Dual channel/monitoring: Based on self diagnosis and CAN communication for setting value tracking, enabling dual channel redundant operation.

3. FULL version (only UNITOL 1020, added on the basis of BASIC)

Synchronization: Built in fast and reliable automatic synchronization function, without the need for external synchronization devices. It can automatically detect voltage difference, frequency difference, and phase angle difference, and issue closing instructions.

Event Logger: Stores up to 500 timestamp events in non-volatile memory, recording important operations, alarms, and faults.

Data Logger: Automatically saves data records of 12 signals for waveform analysis before and after faults.

Real time clock: provides an accurate time reference for event and data recording, and supports time synchronization through Ethernet (SNTP).

4. Power System Stabilizer (PSS)

As a supplementary option to the FULL version, PSS complies with IEEE 421.5-2005 standard 2A/2B type. Its function is to add excitation control signals, dampen low-frequency power oscillations between the generator and the power grid, and improve dynamic stability. For grid connected power generation projects that require Fault Ride Through, PSS is often a mandatory function.

Software selection suggestions:

Single machine island operation without remote communication requirements: LIGHT is sufficient.

Simple requirement for communication or grid connection with the upper system: BASIC.

Require automatic synchronization and detailed fault recording: FULL.

Need to pass grid compliance testing (such as BDEW, ERCOT, etc.): FULL+PSS.

Debugging and Maintenance: CMT1000 Tool Practice

The standard tool for the UNITOL 1000 series is the PC based CMT1000 debugging and maintenance software, which comes with the device on the CD. This software connects to AVR via Ethernet or USB, providing an intuitive graphical interface.

The main functions of CMT1000 are:

Online parameter settings: All regulator parameters, limiter settings, I/O configurations, communication parameters, etc. can be modified online. Support parameter upload and download.

Real time monitoring: Display real-time data such as terminal voltage, excitation current, power, frequency, etc. in the form of instruments, trend charts, numerical tables, etc.

Event and Data Recorder Reading: Download the event list and fault waveform data stored internally in the device for fault analysis.

Dual channel configuration: For redundant systems, the parameters and switching logic of the primary/backup channels can be configured.

PSS parameter tuning: assists in calculating and setting PSS gain and time constant, and can be used for simulation testing.

Firmware upgrade: Upgrade AVR firmware via USB or Ethernet to obtain the latest features and fixes.

Debugging practical process (taking a newly installed diesel generator set as an example):

Pre check: Confirm that the generator, exciter, CT/PT wiring is correct, and the AVR power input and auxiliary power supply wiring are correct.

USB power configuration: Before starting the generator, connect the laptop and AVR with a USB cable and turn on CMT1000. At this time, the AVR controller is powered on (but the power part is not working), and parameter presets can be performed.

Import parameter file: Based on the generator excitation data table, pre input voltage setpoint, PID initial value, limiter setpoint, etc. Save parameters to device flash memory.

First start-up (pressure building): Start the prime mover and reach the rated speed. AVR will automatically establish the terminal voltage (usually 80% -100% rated value). Monitor the pressure building process through CMT1000.

Voltage regulator tuning: Conduct step response testing (such as 5% voltage step), observe overshoot, adjustment time, and oscillation frequency. Adjust the PID parameters until they meet the requirements.

Limiter verification: Simulate over excitation, under excitation, overcurrent and other working conditions to verify the limiter action value and action time.

Dual channel switching test (if applicable): manually turn off the main channel power and verify that the backup channel has no interference connection.

PSS input (if applicable): After grid connection, input PSS and use white noise or on-site testing instruments to verify the damping effect.

Data logger settings: Configure triggering conditions (such as voltage drop exceeding 10%) to ensure automatic waveform recording in case of future faults.

Common troubleshooting and practical cases

Based on on-site experience, the following are several common types of faults and their troubleshooting methods for UNITOL 1010/1020.

Fault 1: Generator unable to build voltage (no voltage output)

Possible reasons:

No remanence or low remanence voltage.

The auxiliary power supply is not powered on (AVR controller is not working).

Excitation power input missing (PMG output fault, loose wiring).

Open circuit of excitation circuit (poor contact of rotor slip ring carbon brush, broken excitation winding).

Troubleshooting steps:

Check the power indicator light on the AVR panel. If it does not light up, measure whether the input voltage of the auxiliary power supply meets the range of 18-420V DC or AC.

Connect the CMT1000 to the AVR and check for any alarm messages (such as "Field Overcurrent", "Loss of Sensing", etc.).

Check if the excitation power input (three-phase AC) is normal. For PMG excitation, check the output voltage of the PMG stator.

Try the "Field Flashing" function: Many AVRs support external excitation voltage building signals. If the AVR has this input, an external DC power source (such as a battery) can be applied to the excitation output for a short period of time to observe whether the voltage is established. Once pressure is established, the self-excited circuit can usually be maintained.

Measure the resistance between the excitation output terminals to determine if the rotor circuit is open.

Fault 2: Voltage instability or oscillation

Possible reasons:

Improper PID parameter setting (high gain).

Voltage measurement signal interference (poor PT wiring, common mode interference).

The speed regulation of the generator's prime mover is unstable (frequency fluctuations cause voltage fluctuations).

Excitation power source fluctuation (abnormal PMG output).

Troubleshooting steps:

Observe the waveforms of terminal voltage, excitation current, frequency, etc. through CMT1000 to determine the oscillation frequency.

Temporarily reduce the proportional gain (KP) of AVR and observe whether the oscillation weakens. If it weakens, the PID needs to be readjusted.

Check if the PT secondary circuit wiring is secure and if the shielding layer is single ended grounded. You can try changing the voltage measurement mode from three-phase to single-phase to see if it improves.

Check the prime mover speed regulator to ensure that the frequency stability is within the allowable range.

Fault 3: Uneven distribution of reactive power after grid connection

Possible reasons:

Droop compensation settings are inconsistent.

CT polarity or ratio error.

VDC mode (island sharing) is not configured correctly.

Troubleshooting steps:

Check if the voltage sag coefficient of each parallel unit is the same. Usually set at 4%.

Verify CT wiring: Ensure that the CT polarity of all units is consistent, and that the current input phase of AVR corresponds to the voltage.

For multi unit operation on isolated islands, enable VDC mode and configure RS485 communication. Check whether the reactive power readings of each unit are consistent through CMT1000.

Fault 4: The dual channel system cannot automatically switch

Possible reasons:

The CAN communication cable is disconnected or has poor contact.

The set value tracking of the backup channel is not enabled.

Backup channel self diagnosis failure (such as internal fault).

Troubleshooting steps:

Check the CAN bus connection between two UNITOL 1020 cables (cable length<3m).

Check the dual channel configuration in CMT1000 and confirm that the setpoint tracking and switching logic is enabled.

Check the status words of the backup channel for any fault codes.

Manually simulate a main channel fault (such as disconnecting the main channel power) and observe whether the backup channel takes over within a few milliseconds. If not, check the interlock logic of the output contactor.

Fault 5: PSS not working or poor damping effect

Possible reasons:

PSS has not been deployed (usually requiring external contacts or software enablement).

The active power of the generator is lower than the PSS start-up threshold.

PSS parameters are not tuned or do not match the impedance of the power grid.

Abnormal speed/power input signal.

Troubleshooting steps:

Confirm that the PSS function package has been installed and enabled in CMT1000.

Check the PSS startup threshold (usually 10-30% rated active power) and confirm that the current power is above the threshold.

Contact ABB for PSS parameter tuning services (based on on-site measurements or simulation models).

Utilize the "white noise" injection function of PSS (if available) to analyze the system frequency response and optimize parameters.

Lifecycle Management and Technical Support

ABB provides a comprehensive full lifecycle service model for the UNITOL 1000 series, helping customers extend equipment life at the lowest cost.

Life cycle stages:

Active and Classic Stage: Provide complete spare parts, preventive maintenance, fault repair, upgrade and renovation services.

Limited stage: It is recommended to start planning upgrades or renovations to the latest technology.

Available lifecycle services:

Technical optimization support (such as PSS parameter tuning).

Spare parts supply (key spare parts: IGBT module, control board, power board, fan).

Preventive maintenance (regular cleaning, terminal tightening, inspection of cooling fans, capacitor aging testing).

Upgrades and modernization (such as upgrading from LIGHT to FULL, or upgrading from single channel to dual channel).

Technical support channels:

Global 24/7 Hotline:+41 (0) 844 845 845

Dedicated email: unitrol1000support@ch.abb.com

ABB University provides standard and customized training (online and on-site).

Interactive e-Learning program that enables self-learning of product knowledge and operations.

Suggestions for spare parts management:

For critical units, it is recommended to reserve at least the following spare parts:

UNITROL 1020 body (or spare control board)

PM40 module (if used)

cooling fan

Fast melting (for power circuits)

Grid Code Compliance Support

With the increasing proportion of new energy grid connected, grid operators have increasingly strict requirements for generator sets. The UNITOL 1000 series supports grid compliance through the following features:

Built in PSS: damping oscillation to improve dynamic stability.

Fast voltage drop detection: AVR response time<20 ms (three-phase measurement), ensuring fast strong excitation during fault crossing.

Detailed simulation model: ABB provides computer representations of control algorithms and IEEE standard models for system simulation research.

Compliance services: ABB provides PSS parameter calculation, reference step response simulation, stability simulation under different grid conditions, and issues reports.

For example, for grid standards that require "low voltage ride through (LVRT)", the UNITROL 1000 can output the maximum excitation voltage within tens of milliseconds when the grid voltage drops to 0%, maintaining the transient stability of the generator.