Critical Power Infrastructure: Generator and UPS

Introduction

Many of us have experienced the sudden panic of a power outage and the potential hours or days of inconvenience that ensue. Those of us fortunate enough to have a back-up generator have experienced the less inconvenient displeasure of sitting in the dark momentarily before the generator kicks on, and waiting another 5 minutes before our WiFi routers reboot. Unfortunately for the critical power sector, outages are not a matter of convenience and tolerances are ZERO; an outage greater than a few milliseconds is an eternity and has massive performance and economic impacts.

For Critical Power Infrastructure, if onsite generation alone doesn't do the trick - then what does? An Uninterruptible Power Supply (UPS). And oftentimes not only a single generator and UPS, but multiple layers of redundant infrastructure.

What is a UPS?

A UPS is a device that detects a disturbance in the normal power source and automatically supplements the loss of power with the energy stored in the system. What separates a UPS from other supplemental/standby systems is the speed at which the transition is made, which is generally less than 12 milliseconds. Within the UPS systems, there are two general types of Uninterruptible Power Supplies: Static and Rotary.

A Static UPS is a power electronic-based system that typically leverages batteries as a means to store energy. A Static UPS converts typical AC distribution voltages first from AC to DC (rectifying), and then from DC back to AC (inverting). The DC bus that is established between the rectifier and inverter creates an injection/charge point for the batteries and the use of power electronics drive the transition times to milliseconds.

A Rotary UPS, or a RUPS, typically leverages the mechanical advantage of inertia as a means to store energy in the form of a fly-wheel. The normal power source drives the fly-wheel and a motor-generator, and during disturbances or outages the inertia of the fly -wheel continues to drive the motor-generator until an alternate power source is supplied or normal power is restored. A RUPS can also be coupled with a diesel engine, which is termed a DRUPS, and offers the UPS and diesel generator (standby source) in a single unit.

How do we use a UPS and a Generator to holistically support critical infrastructure?

A UPS alone cannot sufficiently support a critical electrical load, as the means of stored energy is limited in capacity. A typical static UPS offers a runtime of minutes, which can be scalable up through runtimes of hours but is often cost prohibitive. A rotary UPS offers a runtime up to about 1 minute.

To provide the instantaneous pick up of load as well as the continuous support of load, RavenVolt designs microgrids that include diesel or natural gas generation, layered on top of a UPS. For power continuity, this pairing offers instantaneous protection as well as runtime. RavenVolt designs natural gas generating systems to run continuously as a stand-by source and we offer diesel storage options up to 72 hours via a sub base tank, with the option to design storage and transfer systems in excess of 72 hours.

Conclusion

As our country's reliance on electrical infrastructure grows, in fields that utilize robotics, electric vehicles, or otherwise, the importance of reliable, uninterrupted power is paramount. The combination of UPS systems and reciprocating generation has long been the bedrock of critical power infrastructure and RavenVolt's design and implementation of such systems is industry-leading.

As power electronics, power distribution equipment, and controls mature, alongside the strengthening of the supply chain, the door is opening for the use of Battery Energy Storage Systems (BESS) to serve as both the instantaneous and continuous power sources. With these developments, the future of critical power infrastructure is likely to evolve and the application of BESS within it to become a considerable option.