A comprehensive analysis of the electrical principles of diesel generator set controllers:popular science of core technologies of the”brain”of the generator set

Many people only know that the generator set is the control panel of the unit,but they are not aware that it is the electrical control central brain of the entire control central brain of the entire power supply system,consisting of five core modules;series excitation voltage regulation,generator winding,engine sensors,ATS dual power cabinets,and starting batteries.The mainstream controllers on the market,such as SmartGen and DEEPSEA,are equipped with built in acquisition circuits,computing chips and relay output units,integrating a complete set of electrical algorithms fot monitoring,control,protection and remote communication.Whether it’s the selection of units for sales,on site wiring and debugging,or daily fault maintenance,electrical principles such as three-phase electrical parameters,excitation regulation,short-circuit/reverse power protection,and zero-sequence leakage protection are all essential and practical knowledge.Today’s article breaks down the underlying technical down the underlying technical logic,which can be understood by operation and maintenance,engineering,and foreign trade practitioners.

Mainstream controller model and compatible scenarios

The two mainstream brands in the industry are domestic SmartGren HGM and imported DeepSea DSE.Different models correspond to three major usage scenarios:single machine,ATS automatic switching,and multi-machine parallel operation.For the selection of mainstream and commonly used models,please directly refer to the table below:

Fast matching technical regulations(project selection must see)

A power of 200 kw or more,a single unit match ATS switch cabinet:priority HGM6120N/DSE7320;With two or more units parallel running(such as 400kw weaver of two power supply）,must choose HGM9510,DSE8610 specialized parallel type controller.Ordinary single machine controllers don’t support synchronization and reverse power protection functions.

The four core controller electric function

Controller all operations,monitoring,protection action,all rely on built in electrical acquisition and logic operation circuit implementation,whole life cycle of the four functions cover unit controls;

1、monitoring:engine oil pressure,water temperature,rotational speed,battery voltage,fuel level,frequency,voltage,current;

2、control:manual/automatic start/stop,ATS linkage,fault shutdown(high temperature,low oil pressure,over speed,under voltage);

3、Protection:over current,under frequency,over voltage,phase loss protection,fault code alarm;

4、communication:RS485/J1939 communication(9510/dse8610 supports remote monitoring),etc;

Eight built-in electric protection principle,understand the underlying logic of unit faults

The core value of the controller lies in triggering hierarchical protection based on real-time collected voltage,current,frequency and power signals.Each type of protection corresponds to a clear electrical fault cause and damage risk.

①The overload protection

Electric principle:controller real-time acquisition controller real-time acquisition phase line current,automatic calculation unit output active KW,apparent kVA,compared to the rated current of the generator stator.

Mild overload(110％ rated current):shut down after a delay of 5 to 30 minutes,and short-term impact load is allowed.

Heavy overload(150％ rated current):instantaneous rapid tripping to prevent long-term overheating of the winding and insulation aging.

②Short circuit instantaneous protection

Electrical principle:built-in current interruption algorithm for real-time comparison of three-phase instantaneous currents.If the

Current of any phase exceeds 300％ of the rated value,a short circuit in the circuit is determined.The power generation output circuit is cut off in milliseconds,and in combination with the external air switch,it forms dual protection.Short circuits can generate huge electromagnetic forces that pull on the core and windings of the generator.Instantaneous protection can significantly reduce the risk of winding deformation and burnout.

③The two levels of over voltage protection

controller to collect three-phase voltage true RMS,early warning,outage two level threshold

warning;108％ or higher rated voltage,output voltage controller acousto-optic alarm.distributed to the AVR excitation regulating unit adjust signal at the same time,reduce the excitation current,low output voltage;

shutdown protection:110％ or higher rated voltage,and there is no voltage drop after a delay of2 to 5 seconds,and quickly separating brake to shut down

Common fault causes:AVR excitation regulator failure,over speed of the unit under no-load conditions;High voltage can break down the insulation of the generator winding,burning out the UPS,industrial control precision equipment and lighting fixtures at the back end.

④Under voltage protection

When the voltage continuously drops below 85％ of the rated voltage,the protection logic is triggered:a mild under-voltage alarm is triggered first to limit the input of high-power loads.Shut down directly if there is long-term under-voltage.Electrical hazards:excessive voltage drop during heavy-load starting,insufficient excitation,and load starting,insufficient excitation,and low rotational speed can all lead to under-voltage.Under low-voltage conditions,motor-type loads are prone to clogging,stator current surges,and coils overheat and burn out.

⑤Over frequency/under frequency protection(standard for 50HZ power frequency units)

The engine speed is collected through the MPU speed sensor and converted into the power generation output frequency.The standard safe range is 47 to 53HZ.

If the frequency exceeds 53HZ,the engine is over speeding.Unload and shut down immediately to avoid the risk of mechanical runaway.

If the frequency less than 47 HZ,insufficient engine power,low-frequency electrical energy can damage the frequency converter and precision electronic equipment.At the same time,the speed of the cooling fan of the unit is insufficient,resulting in heat dissipation failure. 

⑥Three-phase voltage imbalance protection 

Continue to contrast A/B/C three-phase voltage difference,when＞10％ rated voltage and pressure difference alarm,time out not repair down time directly.Root cause of the fault:excessive single-phase load,phase failure in one phase line.Three-phase voltage imbalance can generate a negative sequence magnetic field,causing abnormal heating of the generator rotor and severe vibration of the entire machine.

⑦Reverse power protection(available only for parallel controller)

A dedicated electrical algorithm for parallel power of multiple units,real-time monitoring of power flow direction:once the power flows back in the opposite direction(bus bar power flowing into the units),it determines the reverse power and automatically disconnects and opens the circuit breaker after 3 to 100 seconds.Protection purpose:to prevent the unit from being dragged by other gird-connected units and entering the”motor reverse rotation condition”,and to avoid the engine being damaged by reverse dragging and the gearbox being subjected to reverse impact.

⑧Over current and zero-sequence leakage protection expansion

Phase over current:as a fallback secondary protection against overload and short circuit.

Zero sequence leakage:after connecting an external zero-sequence current transformer,the controller collects the leakage current to ground.If the leakage exceeds the standard,the output is immediately,cut off to prevent electric shock accidents.It is commonly used in power supply scenarios with high safety requirements such as construction sites and hospitals.

The generator set controller is not merely a simple display panel;it is a complete electrical acquisition,logical operation,relay output,and multi-level protection system.From single machine backup power supply to multi-unit parallel grid connection,different models correspond to differentiated electrical control schemes.Mastering the eight major electrical protection principles proficiently can significantly reduce the difficultly of troubleshooting units.Whether it is pre-sale selection or on-site operation and maintenance,the root cause of the problem can be quickly located.If you want to know more diesel generator knowledge,please contact DINGBO POWER.