In the fields of diesel generator sets, ship electric propulsion, and distributed energy, the DEIF AGC-4 Mk II, as a new generation generator controller, has upgraded its hardware platform based on the standard AGC-4 and expanded its PMS lite, CANshare digital load distribution, enhanced analog input/output, and more flexible M-Logic logic programming capabilities. This controller supports multiple topologies such as single machine, multi machine parallel connection, grid connection, and islanding operation. It has built-in ANSI standard protection, PID regulation, synchronization, and power management functions, which can meet the control needs from emergency backup power to complex microgrid systems. This article is based on the AGC-4 Mk II Designer Manual (software version 6.1.1), which systematically outlines its core functional architecture, configuration process, advanced additional functions, and typical applications, providing comprehensive technical references for power system design and on-site debugging personnel.
Product positioning and major upgrades
The AGC-4 Mk II belongs to the new generation product of the DEIF Multi line 2 platform. Compared with the previous generation AGC-4, its hardware performance has been improved and it supports a richer combination of options. Its core applications include:
Automatic mains fault (AMF): includes two modes: reverse synchronization and no reverse synchronization.
Island operation: Independently loaded, started and stopped according to digital or timed instructions.
Fixed power/base load: When connected to the grid, it outputs constant active power and participates in the frequency support of the power grid.
Peak Shaving: Automatically adjust the output of the unit based on the imported power of the mains.
Load Takeover: Smooth transfer of mains load to the unit to achieve independent power supply.
Mains Power Export: To output or input constant power to the grid.
At the same time, the controller supports power management (option G5, including generators, busbars, and mains controllers) and extended power management (option G7, including group controllers and power plant controllers), and can build large-scale power plants with up to 32 units. In addition, the addition of PMS Lite lightweight power management system (supporting up to 127 generators, automatically assigning IDs through CAN bus) and CANshare digital load distribution (without the need for a master station, automatically sharing active/reactive power) greatly simplifies the configuration and debugging of multi machine parallel connection.
Communicate measurement configuration and rated parameters
The voltage direct input range of the AGC-4 Mk II is 100-690V AC, and the three-phase, phase separated, or single-phase measurement modes can be selected through menu 9130. In phase separation mode, the controller displays the phase voltages of L1 and L3. The voltage of the L1-L3 line is 240V, but the alarm setting is based on the phase neutral voltage (120V). It should be noted that parameters 1201 and 1202 are set to the phase neutral type. In single-phase mode, only one phase and neutral point are measured.
Reactive power calculation method (parameter 9132): The historical version calculates reactive power based on phase to phase voltage and current. If there is a significant voltage imbalance in the system, it can be switched to based on phase to phase voltage and current (Q via U N Ph and I) to improve accuracy. If option A20 (IEEE 1547-2018 Grid Protection) is activated, this parameter will automatically switch.
The four sets of rated parameter sets (6001~6036) support dynamic switching through digital input, AOP or M-Logic to adapt to different voltage/frequency requirements, especially suitable for mobile power stations or seasonal adjustments. There are two sets of rated parameters for the busbar (6051~6063). If there is no busbar PT, 6054 can be set to "BB Unom=G Unom". Voltage scaling (9030) can be set to 100-25000V by default. If the voltage exceeds the limit, it needs to be modified with the master password.
Standard Protection Function (ANSI)
All protections are time limited and can independently set the starting value, delay, output relay, and fail class. The main protection list is basically the same as AGC-4, but with more flexibility added:
Reverse power (32): 2 segments, setting range -50%~0%, delay 0.1~30s.
Overload (32 inverse time limit): 5 segments, based on power percentage.
Overcurrent (50/51): 6-stage fixed time limit+inverse time limit, supporting voltage dependence (51V).
Overvoltage/undervoltage (59/27): Generator 2-stage overvoltage, 3-stage undervoltage; Bus 4-section overvoltage, 5-section undervoltage, supports phase to phase or phase to medium selection (1201/1202).
Over/Under Frequency (81): Generator 3 sections, Bus 5 sections.
Voltage/current imbalance (60): detects three-phase asymmetry.
Demagnetization/overexcitation (40/32RV): Prevent phase instability based on reactive power limitations.
Non essential load trip (NEL): There are 3 groups in total, and the secondary load is cut off according to the current, frequency, or power threshold.
Setting prompt: Taking reverse power as an example, the typical setting is -5%~-15%, with a delay of 5-10 seconds, and the fault level is set to "trip+stop"; The overcurrent reversal time limit can be set with 6 inflection points (such as 110%/5s to 200%/0.5s) to achieve selectivity. Voltage protection should consider measurement accuracy (Class 1), and it is recommended to set the value offset by 1-2% to avoid misoperation.

PID regulator and speed/pressure control
The AGC-4 Mk II is equipped with an independent PID controller for speed regulation (GOV) and voltage regulation (AVR), which respectively manage frequency, power, active power distribution, voltage, reactive power, and reactive power distribution. The parameters of each controller (Kp, Ti, Td) can be adjusted from menu 2500 to 2690.
Proportion (Kp): determines the response speed, excessive will cause oscillation. It is recommended to fully utilize the output range (such as 0-20mA) to avoid large output changes caused by small deviations.
Integral (Ti): Eliminating steady-state errors, the smaller the Ti, the stronger the integral effect, but if it is too small, it is prone to oscillation. When Ti=0, the integral is turned off.
Differential (Td): improves dynamic stability and is beneficial for rapid disturbances (such as static synchronization). It is usually set to 0 or very small, and the differential is turned off when Td=0.
The load distribution controller (parallel mode) adjusts the power regulation intensity through the power weight factor (PWEIGHT, 2544). 100% indicates full effort to eliminate power deviation, while lower values prioritize ensuring frequency stability. If there is a large fluctuation in power during parallel operation, the PWEIGHT can be reduced or the Kp of the frequency PID can be reduced.
Relay output regulation: If relay pulse output is used, the "ON time" (minimum pulse width) and "Period time" (period) need to be set. The regulator automatically adjusts the duty cycle according to the deviation. When the deviation is large, the pulse is long or continuous, and when the deviation is small, the pulse is short. After entering the dead zone, it stops.
Droop mode: When connected in parallel with existing droop units, frequency droop (2514) and voltage droop (2644) can be enabled, with a droop amount of 0-10%, activated through M-Logic, suitable for old units that cannot provide constant speed regulation.
Synchronization principle and parameter settings
The AGC-4 Mk II supports dynamic synchronization (default) and static synchronization (menu 2000 selection).
Dynamic synchronization: Grid connected units catch up with the bus phase at a certain slip frequency (usually positive, slightly faster than the bus). Key parameters: Sync dfMAX/dfMIN (2021/2022) allows maximum positive/negative slip, typically ± 0.3Hz; Sync dUMAX (2023) allows maximum voltage difference, typically 5%; The inherent closing time of Sync tGB/tMB (2025/226) circuit breaker is used to issue closing pulses in advance. The dynamic synchronization speed is fast and suitable for load switching, but it is necessary to ensure that the slip is positive to avoid reverse power tripping after closing.
Static synchronization: First, adjust the frequency to almost the same frequency as the bus (deviation<50mHz), and then fine tune the phase angle by the phase controller (2070). When the phase angle enters the "closing window" (2033, ± 0.1~20 °), issue a closing command. Small impact but slow adjustment, suitable for applications sensitive to impact.
Pre closing excitation (CBE): allows the unit to close without excitation and then re excite after closing, significantly reducing grid connection time and suitable for black start or emergency scenarios. MPU or EIC speed signal needs to be configured, and parameters such as closing speed threshold (2251) and excitation start delay need to be set. When CBE fails, a 2270 alarm is generated, and the fault level can be configured separately. In addition, CBE supports the "rerun" function. During the cooling period, if a new start request is received, the CBE sequence can be directly re executed without stopping the machine. The excitation state during the cooling period can be controlled through parameter 2266 (ExcCtrl cooldown) (following the bus/normally open/normally closed).
Individual synchronous relay: The closing and synchronization signals can be separated through digital input and additional relays to achieve two-step closing and prevent accidental closing.
PMS Lite Lightweight Power Management
PMS Lite is a simplified power management system designed specifically for off grid power stations, supporting up to 127 generators and allowing for quick configuration through a display screen without the need for PC software. Each controller automatically detects and assigns an ID through the CAN bus (options H12.2/H12.8), supporting load dependent start/stop, priority setting, running hour balancing, minimum operating quantity, and multi start strategy.
Load dependent start stop: Parameters 8501 (start threshold, default 90%) and 8503 (stop threshold, default 70%) determine when to request the start/stop of the next priority unit. Stop logic to consider the remaining unit load and avoid overload.
Multi start: It allows multiple units to be started simultaneously during black start or when a large amount of load is applied, and a response strategy can be set after failure (no action or starting all other units).
Priority (8512): 0~127, the smaller the number, the higher the priority. Units of the same priority will start and stop simultaneously. The operating hours can be set to absolute, relative/travel, or load profile modes, and priority can be dynamically adjusted.
PLC control mode: The unit can ignore internal load dependent logic through digital input or M-Logic, and be completely controlled by external PLC for start and stop, suitable for scenarios where it is linked with the upper computer.
Communication fault handling: The minimum number of operating units, ID missing/new alarms, and duplicate ID detection can be set to ensure system robustness.
CANshare Digital Load Distribution
CANshare allows 2-127 generators to achieve percentage sharing of active and reactive power through the CAN bus, without the need for a master station or power management options. Simple configuration: Select the CAN protocol (parameters 7843-7846) and set it to "Canshare", set the application to "Single DG" and do not select mains power. The controller automatically joins or exits the load distribution line without line monitoring, but can set the CANshare fault timeout alarm through parameter 7860. CANshare and PMS lite cannot run on the same CAN line simultaneously.

Advanced Additional Features
1. Idle Running
Used in low-temperature environments, start at idle speed first, and then increase speed after warming up or reaching the temperature standard. By using digital inputs of "low speed" and "temperature control" in conjunction with a timer (6290), the turbocharger can be protected. The oil pressure alarm is still valid during idle.
2. Fan Logic
Control up to 4 fans, start them in stages according to the cooling water temperature (Pt100 or EIC), and automatically rotate the running time to balance wear. Fan fault feedback can be monitored through digital input, and startup delay can disperse peak current.
3. Derate
When the ambient temperature rises or the cooling capacity decreases, the maximum output power of the unit (6250~6266) will be automatically reduced. The derating can be triggered based on 4-20mA, Pt100, EIC temperature, or M-Logic, and the lowest value can be taken for the three independent derating groups. Supports reverse (power decreases with higher temperature) and proportional (power increases with higher temperature) characteristics.
4. Dynamic Frequency Response (DFR)
Suitable for hybrid systems of photovoltaic and diesel engines, when the excess photovoltaic power generation leads to reverse power of the unit, DFR automatically increases the bus frequency, forcing the photovoltaic inverter to reduce power and protect the unit. Frequency upper and lower limits, dead zone, slope, and recovery delay can be set and activated through M-Logic.
5. Non essential load trip (NEL)
According to the unit current or bus frequency, cut off the secondary load in three groups to prevent overload shutdown. Each group can individually set the current/frequency threshold and delay.
6. Engine heater and fuel pump logic
The heater automatically starts and stops based on the cooling water temperature when it is in the shutdown state (6320); The fuel pump maintains the service fuel tank level (6550) based on the level sensor (RMI or 4-20mA) and has a fuel injection check timeout alarm. Add DEF pump logic (6720) and universal fluid pump logic (6730).
7. Circuit breaker management
Supports pulse, continuous (NE/ND), and compact circuit breakers, with configurable closing spring loading time (6230/7080) and "shake out circuit breaker" mode to suppress false alarms when the circuit breaker is in the test position.
8. Battery testing and asymmetric monitoring
Battery testing can be conducted manually or automatically (periodically) to check the load-bearing capacity of the starting battery; The battery asymmetry test (6430) determines the degradation of a single battery by comparing multiple input voltages.
9. Master Clock
In islanding operation, compensating for accumulated cycle errors by adjusting frequency ensures accurate timing of devices that rely on zero crossing points, such as electric clocks.
M-Logic and Programmable Input/Output
M-Logic is a built-in simple logic tool that can be configured through PC software without the need for additional options. It allows the combination of digital input, alarm events, operating status, and other conditions to output to relays, mode switching, or PID control commands. For example, logic such as "activating the fan while the engine is running" and "forcing the maximum speed during the cooling phase" can be implemented.
The digital input function is rich, including remote start stop, mode switching, locking and closing, manual speed/voltage regulation, battery testing, circuit breaker spring loading feedback, PLC control (PMS lite), etc., all of which can be allocated according to needs. Analog input (4-20mA, 0-40V, Pt100, RMI) can be scaled and set with alarms, supporting cable breakage detection.
External analog setting value: External frequency, power, voltage, reactive power, or power factor setting values can be received through terminals 40/41 and 42 of option M12, which need to be activated with digital input. It can also be implemented through Modbus or CIO modules.
Phase compensation of step-up/step-down transformers
When the generator is connected to the grid through a step-up transformer, the phase shift caused by the transformer vector group needs to be considered. The AGC-4 Mk II supports setting phase compensation angles through parameters 9141 (Mother Parameter Set 1) and 9142 (Mother Parameter Set 2). Typical vector group corresponding angles: Dy1 →+30 °, Dy11 → -30 °, Yy6 → 180 ° (actually set as 179 °), Dz4 → -120 °, etc. If measuring transformers are used simultaneously, their phase shift should also be included in the total compensation. For step-down transformers, parameter settings are opposite to step-up (refer to Tables 9.6 and 9.7 in the manual).
Typical troubleshooting and maintenance recommendations
Synchronization failure: Check the slip, voltage difference, and circuit breaker closing time settings; Ensure that the phase of the bus voltage is correct (see 9141 phase compensation).
Unit startup failure: Check the startup relay, fuel solenoid valve, operation feedback signal (digital quantity/MPU/frequency), verify the number of startup attempts (6190) and startup preparation timer (6180).
Uneven load distribution: Adjust PID weights and droop parameters, check the shielding and terminal resistance of the load distribution line (if there are analog quantities).
Alarm misoperation: Confirm whether the fault level setting is too strict, and use the "suppression" function (such as Not run status, GB ON, etc.) to delay the alarm until the unit runs stably and takes effect.
Data loss: Regularly backup parameter files (. usw) through PC software, and be sure to perform a backup (9230) before replacing the internal battery.
CANshare or PMS lite communication abnormality: Check the CAN bus terminal resistance (120 Ω), shielding layer single ended grounding, and protocol selection consistency.
