The world is becoming more reliant on electrical power. Electrical power is required for a primary source of energy, back-up systems, military deployment and disaster relief. As technology increases the power demand grows, and systems can-not afford to go offline.
This drives the requirement to have larger and more reliable generators. Larger generators become unpractical and a single point of failure is evident. RFL have developed Interior Permanent Magnet Generators (IPMG) that are designed to allows a series of generators to run in parallel.
Advantages of Paralleling
Parallel standby power systems have significant advantages over single larger
Reliability: Parallel operations of multiple generators provides greater reliability than by a single generator when operating critical loads. If a unit falls over the load can be covered by other units in the system.
If the reliability of a single generator is N=98%, an N+1 system is 99.96% reliable, N+2 is 99.999% and so on.
Reducing light loading of the prime mover: Loads in most cases will never run at a constant level, and generators run most efficiently at 75-80% of full load. A parallel system allows for the system to start-up and close down parallel generators as required.
Scalability: If a generator is bought for a specific power consumption, the system is limited to the size of that generator. If the system is increased in size a second generator would need to be acquired, and care needs to be taken to balance the system. In turn the reliability of the system will decrease. Opting for a larger generator has the disadvantage of a costlier purchase, and having the generator running at a lower load which decreases efficiency. Using RFL generators allows for generators to be continually ran in parallel to increase the scalability as the system grows
Ease of maintenance: When a generator requires maintenance or refuelling the whole system does not need to be powered down, this means the system can run indefinitely off a parallel generator system.
Shipping: Having a net of smaller generators eliminates a series of problems that can occur from shipping a single larger generator. This would be especially evident in cases like military use and disaster relief where they system may only be deployed for a short period at a time.
Cost of $ per kW: Smaller generators are generally cheaper than larger generators exceeding 600Kw due to the number the of smaller generators produced compared to the larger size generators. Making a parallel configuration is more cost effective then a larger generator.
Why RFL Alternators
RFL has completed extensive testing on paralleling generators, to the extent where RFL alternators have been successfully paralleled using different prime movers on a different fuel system.
Paralleling generators has historically been done using wound-field synchronous generators. Replacing the wound-field generator with Permanent Magnet (PM) generators vastly improves the system efficiency, size and reliability.
RFL uses droop control for parallel connection of the alternators and a paralleling switch set up with a three-phase contactor and a simple circuit that detects the point when phases waveforms are synchronised.