Parallel operation of power generators. Greater energy security.

What is the parallel operation of power generators?

Parallel operation of several generators is a good and common way to use these units to combine their power. However, many users may consider this mode of operation unsafe, due to the potential interruption of communication between units and the associated consequences of even losing a power source. The response to these concerns is CAT^® patented innovative Failsafe Adaptive Load Sharing (FALS) technology.

What is so revolutionary about FALS from CAT^®?

It is worth presenting its potential with a specific example. At Company X, five generators (equipped with this technology) with a capacity of 2 MW each operate in parallel. Their total capacity is therefore 10 MW, while the average operating load is 8 MW. The synchronised operation of this set means that after the start signal, all units are launched. The first one to reach the nominal voltage and frequency closes the circuit to power the bus. Then all other units will use their local sensors to synchronise to the powered bus and close the circuit. When the load in the system increases, the units actively balance the load. Since all units continuously transmit the status of their safety switches (i.e., connected/disconnected) and load factor to the network, all online units are able to maintain load balance using their own fuel and excitation control. With 8 MW on the bus, each unit will take on a load equal to 1.6 MW.

Parallel operation of generators makes it possible to distribute the load among several units working in an integrated manner. But what happens when some of them lose communication with the rest?

However, during the operation of these units, a malfunction occurred and the connection to the two units was lost. The company must continue working, so the load continues to be 8 MW. What then happens to the devices?

In this case, the FALS system is activated. The three units with which contact is maintained automatically enter safe isochronous mode. In turn, those generators with which the connection has been lost enter a safe static mode. All units will keep the load factor unchanged, as long as the system load does not change. Therefore, there is no loss of power.

What if the plant’s demand for power increases, and there is still no contact with the two units?

If this is the case, units in isochronous mode will take on most of the additional load. They will maintain nominal voltage and frequency until the load factor exceeds about 80%. When the load factor of the units in isochronous mode exceeds 80%, they will intentionally produce frequency or voltage droop on the passive side. This adjustment will cause units in static mode (i.e., those operating safely) to accept the load according to their calculated adjustment curve.
Such a mechanism is an important innovation introduced by CAT^®. In other systems, isochronous units lower the frequency only when overloaded. In the safe mode used by CAT^®, the isochronous units intentionally induce a decrease before they are overloaded.

And what happens when the load drops?

An analogous process occurs if the load decreases. A greater drop in power will occur on units operating in isochronous mode. They are then supposed to maintain their nominal voltage and frequency until they reach a value of about 20% of the load factor. When the load drops below 20%, the isochronous units will perform upward adjustment. This action will cause units operating in static mode to reduce their load according to their calculated control curve.
Also in this case, it is an advantage over simple static-isochronous systems, in which units in isochronous mode must start drawing current from the bus (go into reverse power mode) to compensate for the power of units in static mode.

What is the uniqueness of CAT^® technology?

Importantly, technology created by CAT^® allows power to be maintained even if contact with the generators is lost before the entire system is up and running. If the units lose communication before they receive a request to start, they will perform a so-called dead-bus safe arbitration protocol. Units working as intended will perform arbitration completely normally. This approach minimises the risk of simultaneous circuit closure with an unpowered bus.
In summary, the FALS technology from CAT^® is a guarantee of safe parallel operation of generators. This solution will please all those who care about ensuring maximum energy security for their company. Such solutions work successfully in Data Centres, and manufacturing plants, where uninterrupted power supply is crucial for the proper functioning of the entire enterprise.