DEIF LSU-112DG generator set parallel control unit

DEIF LSU-112DG generator set parallel control unit

In distributed power generation, backup power sources, and grid connected power stations, parallel operation of multiple generator units is the key to achieving capacity expansion, improving power supply reliability, and operating economy. However, to achieve stable parallel connection of multiple units, precise load distribution and frequency synchronization control capabilities are necessary. The LSU-112DG launched by DEIF company is a dedicated control unit designed for this purpose. It can accurately regulate the speed of the generator set's prime mover (diesel engine, gas engine, etc.), ensuring that the unit can stably and reasonably share the load when running alone, parallel with the power grid, or parallel with other units. This article provides a comprehensive analysis of the working principle, functional characteristics, technical parameters, and application configuration of LSU-112DG based on official technical materials.

Product Overview and Application Scenarios

LSU-112DG is a generator set prime mover control unit, mainly used to control the prime mover in the generator set (such as diesel engines, gas engines, etc.). Its core task is to adjust the speed of the prime mover according to the grid frequency or power command, thereby controlling the output power and frequency of the generator.

This unit can be applied to the following four main operating modes:

Isolation single machine mode: As an independent power source, LSU-112DG controls the prime mover to maintain a stable frequency (such as 50Hz or 60Hz), supplying power to isolated loads.

Parallel connection mode with the power grid: When the generator unit needs to operate in parallel with the infinite power grid, LSU-112DG can control the unit to deliver the set power to the power grid (constant power control). At this time, the power grid frequency is determined by the large grid, and the unit only needs to adjust the active output.

Multi machine parallel islanding mode: When multiple generator units jointly form an isolated power grid, LSU-112DG achieves real-time frequency and power sharing between units through parallel lines, ensuring load distribution according to unit capacity ratio.

Frequency and power combination control: In certain special applications, coordinated control of frequency and power can be achieved simultaneously.

The LSU-112DG is designed to directly drive the actuator of mechanical speed controllers (by outputting acceleration/deceleration pulses through relay contacts), and can also be used in conjunction with DEIF's electronic potentiometers (such as EPN-110DN or EPQ-96) to control electronic speed controllers, covering a wide range of applications from traditional mechanical speed controllers to modern electronic speed controllers.

Working principle and core measurement

2.1 Measurement principle

The LSU-112DG integrates a frequency transmitter and a power transmitter internally. It calculates the current frequency and power by collecting voltage (single-phase or two-phase) and current (single-phase) signals from the generator.

Frequency measurement: taken from voltage signals, with high accuracy and fast response. If the system requires higher frequency stability, an external common frequency transmitter can be connected to provide a unified frequency reference for all parallel LSU-112DGs, achieving more accurate synchronization.

Power measurement: The built-in power transmitter is based on the I × cos φ principle, which calculates active power by measuring current and power factor angle. This transmitter is suitable for three-phase systems with balanced loads, and the wiring method is 1W3 (two watt meter method, used for three-phase three wire balanced loads) or 1W (single-phase method, used for phase voltage and neutral point). For applications that may experience severe unbalanced loads, it is recommended to connect an external power transmitter such as TAS-331DG recommended by DEIF (outputting 4-20 mA). At this time, the built-in transmitter will automatically disconnect and the external signal will prevail.

2.2 Parallel tracks (PS and FS)

The core parallel mechanism of LSU-112DG relies on two analog parallel lines:

FS line (frequency sharing line): All LSU-112DGs of parallel units output their measured frequency signals (converted into voltage) to the common FS line. The voltage on this line reflects the average frequency of the system. Each unit compares its frequency with the FS line voltage to generate a frequency deviation signal, which is used to adjust the speed and make the frequencies of all units tend to be consistent.

PS line (power sharing line): Each unit outputs its power signal (converted into voltage) to the common PS line. The voltage on the PS line represents the average value of the total load (proportionally). Each unit compares its actual power with the PS line voltage to generate a power deviation signal, which is used to adjust the throttle and distribute the load according to the set ratio.

These two lines are both analog buses (-5V to+5V), corresponding to a frequency offset of ± 2.5Hz or a power of 0-100%. When the unit is disconnected from the bus or the auxiliary power supply loses power, the built-in relay will automatically disconnect its output to avoid interference with the bus.

2.3 Self monitoring function

The LSU-112DG is equipped with a built-in microcontroller and a self-monitoring circuit. The green "POWER" LED is constantly on, indicating that the power supply is normal and the program is running correctly; If the LED flashes at 2-3Hz, it indicates that although the power supply is normal, the program is running abnormally, and the status output terminal (17-18) will be disconnected (fault indication). This design greatly facilitates on-site troubleshooting.

Detailed explanation of core functions

3.1 Speed Control Output (SG ▲/SG ▼)

LSU-112DG provides two relay contact outputs, which are respectively used to control the "speed increase" and "speed decrease" of speed regulating motors or actuators. The controller adopts a P controller (proportional control) internally, which generates pulse width modulation signals based on frequency/power deviation. The key parameters include:

T-N (minimum on-time): Within the proportional band, the minimum duration of the control pulse can be adjusted within a range of 25~500ms.

X_P (Proportional Band): Set a deviation range within which the pulse duty cycle is proportional to the deviation. For frequency control, the proportional band is 0~± 2.5Hz; for power control, it is 0~± 50% of the rated power.

T-P (cycle time): The time interval between the starting points of two adjacent pulses, usually 10 times the T-N, but can also be selected as 5, 15, or 20 times the T-N through jumper wires.

Deadband: Set a deviation zone that does not generate adjustment pulses to avoid frequent actions of the governor. The default power dead zone is ± 2%, and the default frequency dead zone is ± 0.1Hz, both of which can be adjusted through jumper wires.

When using a DC servo motor, it must be driven by an external intermediate relay and a transient suppressor must be connected in parallel to the relay coil to protect the contacts.

3.2 Unload Input

Terminals 33-34 can be connected to a passive normally open contact. When the contact is closed, LSU-112DG will control the unit to reduce load to zero power and automatically disconnect its power output (PS line) from the bus. This function is commonly used for preparation before unit disconnection or quick unloading in emergency situations.

3.3 Reference Input (Ref.) and Local Power Control

Terminal 35 is a reference input terminal used for fixed power control mode (such as the unit delivering constant power to the grid). The input signal is+0.5V to+5V DC (for terminal 36 "⊥"), corresponding to 10% to 100% of the rated power. This input is activated at 0.55V and deactivated at 0.45V. When this input is valid, LSU-112DG is still connected to the PS and FS lines, but the PS line only serves as an output (broadcasting the actual power of the machine to other units) and does not participate in the comparison. This means that the local machine no longer responds to load distribution, but instead sets a fixed output power while still participating in frequency synchronization.

Terminal 37 provides a+5V reference voltage output, which can be used to connect an external potentiometer to form a local power setting circuit.

3.4 Derating setting

The front panel of LSU-112DG is equipped with a derating potentiometer, which can adjust the corresponding generator capacity within the range of 50% to 100% (such as derating a 150kW unit to 100kW). After the reduction, load distribution will be based on the reduced capacity. For example, if a 100kW unit is connected in parallel with a 150kW unit that has been downgraded to 100kW, the total load of 125kW will be evenly distributed as 62.5kW+62.5kW. If the capacity is not reduced, it will be allocated as 50kW+75kW according to the actual capacity ratio. The derating function provides great flexibility for mixing different capacity units.

3.5 External frequency and power transmitter

If higher precision is required or to cope with unbalanced loads, LSU-112DG supports external transmitters:

External power input (terminals 31+, 32-): Connect 4-20mA DC signal, corresponding to 0-100% power. Recommend using DEIF TAS-331DG.

External frequency input (not clearly indicated, but the document mentions that external frequency transmitters can be shared): Please refer to the application notes.

When an external power transmitter is connected, the built-in I × cos φ transmitter is automatically disabled.

Wiring and Configuration Guide

4.1 Overview of Terminal Functions

Terminal identification function description

1.3 X1/X2 auxiliary power input (AC or DC, depending on the model)

17,18 Sta status output (normally open contacts, closed during normal operation)

28,29 IL1 current transformer input (S1 connected to 28, S2 connected to 29)

31,32 Ext. P external power transmitter input (31+, 32-), short circuit when not in use

33,34 Uni load shedding input (connected to passive normally open contacts)

35 Ref. Reference input (0.5-5V corresponds to 10-100% power)

36 ⊥ public area (internally connected to all ⊥ terminals)

37+5V reference voltage output (for local potentiometer)

38,39 FS, ⊥ frequency sharing line and common terminal

40,41 PS, ⊥ power sharing line and common terminal

43,44 SG ▲ Speed up Relay Contact

45,46 SG ▼ Deceleration relay contacts

4.2 Selection of Wiring Types

LSU-112DG supports two standard voltage connections:

1W3 (standard): Suitable for three-phase three wire balanced loads. Connect L1 to terminal 24 and L2 to terminal 26.

1W (phase voltage and neutral point): Suitable for using phase voltage in single-phase or three-phase four wire systems. L1 (P) is connected to terminal 24, and the neutral wire is connected to terminal 26.

The current measurement is always carried out through a single-phase current transformer with terminals 28-29 (usually taking the L1 phase current). Therefore, for three-phase systems, power measurement is based on the approximation of "one phase current+line voltage" of I × cos φ, which is only applicable to balanced loads.

4.3 Important precautions

All terminals marked with "⊥" should be connected internally and reliably grounded to ensure measurement accuracy.

The analog DC input shall not exceed 110% of the nominal value.

The current input shall not exceed 110% of the rated value to ensure accurate power measurement. When selecting, the maximum power and power factor of the generator should be considered. For example, the maximum current should be calculated based on the generator kVA and cos φ=1 to ensure that the secondary side of the current transformer does not exceed 5A (or the set value) at full load.

When the relay contacts drive inductive loads (such as DC motors), external intermediate relays must be used and transient suppressors must be installed.

Technical specifications and performance parameters

5.1 Measurement Input

Rated current (I ₙ): optional 0.3~5.0A AC (set through calibration module). The adjustment range is 75%~100% I. Overload capacity: 4 × I ₙ continuous, 20 × I ₙ 10 seconds (maximum 75A), 80 × I ₙ 1 seconds (maximum 300A). Power consumption per phase ≤ 0.5VA.

Rated voltage (U ₙ): 57.7~690V AC, available in multiple levels. The scope of work is 60%~120% U ₙ. Overload: 1.2 × U ₙ continuous, 2 × U ₙ 10 seconds. Input impedance 2k Ω/V.

Frequency range: 40~70Hz, rated frequency can be set to 45~65Hz.

5.2 Output

Speed control relay: Two normally open contacts, rated capacity AC1/DC1: 250V AC/24V DC, 8A; AC15/DC13：250V AC/24V DC，3A。 The electrical lifespan is 1 × 10 ⁵ times.

Analog parallel line output: PS/FS line output -5~0~5V DC, corresponding to -100%~0~100% power or -2.5Hz~0~+2.5Hz frequency. Accuracy ± 2%.

Reference voltage output:+5V DC ± 1%, maximum load 5mA.

Status output: Optocoupler output, maximum 30V DC/5mA, cut-off in case of fault.

5.3 Power Supply

AC power supply type: 57.7~690V AC ± 20%, power consumption ≤ 3.5VA.

DC power supply type: 24, 48, 110, 220V DC, -25%/+30%, power consumption ≤ 2.5W. UL certification is only limited to 24V DC.

The DC power supply must meet the requirements of Class 2 power supply.

5.4 Environment and Isolation

Working temperature: -25 ℃~+70 ℃ (UL certification upper limit of 60 ℃).

Climate grade: HSE (DIN 40040), suitable for high humidity environments.

Electromagnetic compatibility: Complies with IEC/EN 61000-6-1/2/3/4.

Isolation voltage: Measure voltage, current, relay, analog quantity, and auxiliary power supply between 3250V 50Hz for 1 minute.

Protection level: enclosure IP40, terminal IP20 (IEC 529/EN 60529).

Flame retardant: All plastic components comply with UL94 V-1 self extinguishing.

5.5 Mechanical specifications

Wiring capability: maximum 4.0mm ² single strand wire, 2.5mm ² multi strand wire.

Installation: Panel installation, equipped with a transparent dust cover (can be lead sealed to prevent accidental adjustment).

Settings and Instructions

6.1 Front panel adjustment components

Frequency setting: 45~65Hz continuously adjustable.

Derating: 50%~100% rated power.

T-N (minimum on-time): 25~500ms.

X_P (proportional band): 0~± 50% power or 0~± 2.5Hz.

There are also internal jumpers used to select factors such as TP multiples and dead zone widths, as detailed in the customization manual.

6.2 LED indicator lights

UG (green): The generator voltage is constantly on; Extinguish upon loss of pressure.

Unload (green): It lights up when the unit is in a unloaded state.

SG ▲ (yellow): It lights up when the speed increasing relay is engaged.

SG ▼ (yellow): It lights up when the deceleration relay is engaged.

6.3 Calibration

The unit has been calibrated according to the order requirements when it leaves the factory, and generally only minor adjustments to the derating and proportional parameters are needed on site. If you need to change the measurement range (such as current ratio), you need to send it back to DEIF or use a dedicated calibration module.

Typical application wiring example

7.1 Single machine fixed load operation

The unit is equipped with a fixed load independently. Simply connect the LSU-112DG according to 1W3, and connect the reference input terminal (35) to the set voltage from the potentiometer (or suspend and short-circuit to 36 for internal frequency control). The PS and FS lines can be left unconnected or only used for monitoring. The output of the governor is connected to the actuator.

7.2 Parallel islanding of multiple machines

Multiple units are each equipped with an LSU-112DG, with all FS lines connected in parallel (38 interconnected, 36 grounded) and all PS lines connected in parallel (40 interconnected, 36 grounded). Each unit is equipped with a derating potentiometer based on its actual capacity. When the total load of the system changes, each unit automatically adjusts the throttle to distribute power proportional to the reduced capacity.

7.3 Parallel constant power connection with the power grid

When the unit needs to be connected to the power grid, a 0.5-5V signal (from an external power controller or potentiometer) should be connected to the reference input terminal (35) to set the output power. At this time, LSU-112DG is still connected to the FS line (for frequency synchronization, but the grid frequency is fixed, so the FS line is only used for monitoring), and the PS line is used as the output to broadcast the local power (if any) to other units that may be connected in parallel. The governor will adjust the throttle to track the actual power to the set value.

Selection and Ordering Guide

There are two basic models of LSU-112DG:

291306012001: DC power supply type (24-220V DC wide range).

291306012002: AC power supply type (57.7-690V AC wide range).

The following information must be clearly stated when placing an order:

Coupling method: 1W3 or 1W.

Measurement power: It is necessary to calculate the power once based on the CT ratio and PT ratio (for example, CT 500/5, PT 400/100, then the measured power P=500 × 400=200kW).

Rated power factor (cos φ): used for calibrating power transmitters.

Measure voltage (U ₙ): for example, 400V.

Auxiliary power supply: AC or DC and specific voltage value.

Example order code: 2913060120-01 LSU-112DG 01 1W3 100kW 0.8 100V 24V DC

Maintenance and Precautions

Installation should follow NEC (USA) or CEC (Canada) regulations and only use 60/75 ℃ copper wires.

Regularly check the terminal fastening to prevent looseness.

Due to continuous product improvement, DEIF reserves the right to make changes, and the latest information is subject to the official website.

If UL certification is required, it must be specified at the time of ordering and cannot be customized outside the DEIF factory.