Integrated closed loop control method and apparatus for combined uninterruptible power supply and generator system

Abstract

The present invention provides a method, computer program product, and apparatus and control system and method for providing substantially uninterrupted power to a load. The apparatus includes a control system coupled with an electrical power storage subsystem and a electrical power generator. The control system is configured to provide a plurality of modes of operation including at least a static compensator (STATCOM) mode, an uninterruptible power supply (UPS) mode and a generator mode (gen set), and to control transitions between each of the plurality of modes. In one embodiment, the control system is an integrated closed loop control system that includes a current control system and a voltage control system. The apparatus is capable of operating at least two of the plurality of modes simultaneously, including ramping the gen set mode up and simultaneously ramping the UPS mode down as the gen set mode is ramped down.

Description

FIELD OF THE INVENTION This invention pertains generally to control systems, and more particularly to control systems allowing plug-and-play integration of modules in a power conditioning system. BACKGROUND There are different devices known in the art for improving power quality and reliability of grid or utility line power supplied to sensitive loads. Three of these include, a static compensator (STATCOM), an on-line uninterruptible power supply (UPS), and an off-line UPS. A UPS may also be operated in cooperation with a power generator or gen set, for long term interruptions. FIG. 1A illustrates a typical STATCOM 100 in which a Voltage Source Converter (VSC) 102 is connected to an AC system 104 supplying a load 106 through a shunt-connected transformer 107. A capacitor 109 is connected to the DC terminals 108 of the VSC 102 and is usually an integral part of the VSC 102. The VSC 102 controls the line voltage by injecting or absorbing reactive power. A STATCOM aids in controlling...

AI Technical Summary

Benefits of technology

Thus, the inventive method and apparatus result in superior performance over conventional systems and methods, by operating the UPS as a static compensator (STATCOM) throughout the entire event duration, whether short or long term, to respond to the load's reactive power requirements. Embodiments of the novel method and apparatus, further, perform dynamic load leveling by providing or absorbing active power, improving and usually optimizing dynamic behavior under island conditions (where the load is isolated from

Problems solved by technology

While a STATCOM has relatively low operation costs, a STATCOM does not provide active power and therefore fails to operate under short circuit conditions or other conditions where active power provision is required or desired.

Further, a STATCOM has a limited ability to correct voltage fluctuations due to grid faults or switching events.

The on-line UPS 110 requires double conversion resulting in relatively low efficiency and high operation costs.

Typically, the gen set has a long response time to dynamic voltage (or current) variations and a large overload capability.

The drawback of this operation principle is that the good dynamic behavior of the UPS (that is, rapid response to reactive or active power variations in the load and stabilization of frequency), especially during generator operation, cannot be used or achieved because there

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