WOODWARD EGCP-3 Engine Generator Control Package LS (Load Sharing)

Synchronizer

The EGCP-3 control uses digital signal processing techniques to derive both true RMS voltages and relative phase of the fundamental frequencies of the bus and generator voltage wave forms. Digital signal processing techniques offer significantly improved measurement accuracy in the presence of waveform distortions, particularly since the phase measurement does not depend on zero crossings of the waveforms.

Either phase matching or slip frequency synchronizing may be selected. Phase matching method controls the engine speed to give zero speed error and minimal phase error between the generator and bus; this provides rapid synchronizing for critical standby power applications. Slip frequency synchronizing guarantees a fixed speed difference between generator and bus. This insures the generator to be faster than the bus and initial power flow is out of the machine for larger generators. For both synchronizing methods, the EGCP-3 control uses actual slip frequency and breaker delay values to anticipate a minimum phase difference between bus and generator at actual breaker closure.

The synchronizer can sense a dead local bus and close the generator circuit breaker automatically when safe to do so. The network communication between EGCP-3 control assures that multiple generators cannot close simultaneously onto a dead bus.

There are four synchronizer modes of operation: Run, Check, Permissive, Off. The mode can be selected through Watch Window, the front panel display, or Modbus. The last mode selected by any of these interface methods will be the mode of operation.

Additional synchronizer features include: voltage matching, time delayed automatic multi-shot reclosing, and a synchronizer timeout alarm. Raise and lower inputs can be used to manually adjust speed for manual synchronizing. Voltage raise and lower inputs can be used to manually adjust voltage for manual voltage matching. Each of these features may be enabled or disabled during setup.

Load Control

When the generator circuit breaker is closed, the LS model is in Isochronous and will Load Share with other units also connected to the bus. The speed bias output will control the load of each engine by slight changes to the speed control’s speed reference. When the breaker is open, the EGCP-3 will be in droop operation. Another mode of Load control is BaseLoad; it begins at breaker closure when the load control function takes control of the EGCP-3 speed bias output directly from the synchronizer. The matching of synchronizer slip frequency to initial load (unload trip level) can result in a bumpless transfer to load control. On command, the adjustable ramp allows smooth, time-controlled loading into Load Sharing, BaseLoad, or process control. A ramp pause switch input allows holding of the load ramp for warm-up or other purposes. Process Control is a derivative of BaseLoad operation. In this control mode, one genset may be assigned as a master, to control the loading of other gensets on the bus.

The EGCP-3 control provides switch inputs to allow raising or lowering the internal BaseLoad reference. The control also provides a 4–20 mA (or 1–5 Vdc) analog input for remote load setpoint, if desired. The load reference can also be set through a Modbus or ServLink DDE communication interface.

When unloading, an adjustable unload ramp provides time controlled unloading to the unload trip level. When load reaches the unload trip level, the control will hold the load at the unload value, the breaker can then be opened manually to remove the genset from service. The ramp pause switch can be used to stop the load ramp at its present value for cool-down or other purposes.

The load and unload ramps also provide smooth transition between BaseLoad and process control any time the operating mode is changed.

The EGCP-3 control includes several additional load control features:

 Simple load droop operation provides safe operation in parallel bus applications in the event of a circuit breaker aux contact failure. 

 Isochronous operation when the bus is isolated. 

 Adjustable load switch output with independent pick-up and drop-out points provides a signal when the specified load is exceeded.

Process Control

A cascade process controller is provided for cogeneration, import/export control, pond level maintenance, pressure maintenance, or other application. An adjustable bandwidth input filter, flexible controller adjustments, an adjustable deadband, and direct or indirect control action, allow the process control to be used in a wide variety of applications.

A 4–20 mA (or 1–5 Vdc) process transmitter provides the process signal to the EGCP-3 control. The control includes an internal digital process reference which may be controlled by raise and lower switch contact inputs or by an external 4 20 mA (or 1–5 Vdc) process reference, or by a Modbus or ServLink communication interface. The output of the process control provides the cascade load reference to the BaseLoad control.

Adjustable ramps allow smooth entry to or exit from the process control mode. When the process control mode is selected, an adjustable ramp moves the load reference in a direction to reduce the process control error. When the error is minimized, or the reference first reaches either the specified high or low load pick-up limits, the process controller is activated. When unloading from the process control, an adjustable unload ramp provides time controlled unloading to the unload trip level. When load reaches the unload trip level, the EGCP-3 control automatically issues a breaker open command to remove the generator set from the system. The ramp pause switch input allows holding of the load ramp for cool-down or warm-up purposes.