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SMART SWITCH

IP.com Disclosure Number: IPCOM000212779D
Publication Date: 2011-Nov-28
Document File: 6 page(s) / 76K

Publishing Venue

The IP.com Prior Art Database

Abstract

A design for a self-regulating device in rotary generator engines which has the inherent capability to enable a "ride-through" without the use of any switches or power electronics is proposed. The design utilizes only fixed capacitors and reactors and a resistive element to absorb kinetic energy out of an engine and therefore reduce generator acceleration. No controls are required for the present design, as the functionality of the design is inherently adjusted based on the grid conditions y.

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This is the abbreviated version, containing approximately 51% of the total text.

Page 01 of 6

RP13658

BRIEF ABSTRACT

    A design for a self-regulating device in rotary generator engines which has the inherent capability to enable a "ride-through" without the use of any switches or power electronics is proposed. The design utilizes only fixed capacitors and reactors and a resistive element to absorb kinetic energy out of an engine and therefore reduce generator acceleration. No controls are required for the present design, as the functionality of the design is inherently adjusted based on the grid conditions y.

KEYWORDS

    Smart switch, self-regulating device, ride-through, rotary-type generators, grid, mechanical brake, power electronics, small generator, LC resonance circuit, pre fault, post fault

DETAILED DESCRIPTION

    There exists some difficulty for small rotary-type generators which utilize, for example, gas engines to meet the recent grid code requirements of certain countries. Typically, the requirement is to demonstrate ability of a rotary device to "ride-through" an entire duration of time of a predefined grid event. Such events are usually produced by short circuit at the point of interconnection with the grid. Small generators typically have low inertia and therefore they accelerate very fast during the grid code faults. A consequence of this behaviour of the generator is that these units may go out of synchronism and fail to pass the grid code "ride- through" test.

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SMART SWITCH



Page 02 of 6

RP13658

    Conventional mechanical solutions to this problem are usage of a brake in a machine during such conditions. Another more efficient conventional solution utilizes an electrical brake. However, most electrical brake devices are based on relatively expensive power electronics. Further, power electronic based switches are very fast but are expensive, as they have to carry entire load during normal conditions.

    Hence there is a need for a mechanism in small generators which enables a "ride-through" without the use of any switches, power electronics or use of any mechanical brakes.

    According to the proposed design, two parallel three-phase branches are used to connect the generator to the grid. Figure 1 illustrates the circuit diagram of the proposed smart switch. A first branch includes a resistive element needed to absorb kinetic energy during the fault. The first branch carries almost zero current during normal operation and almost full current during fault. A second branch acts like a switch and carries almost full current during normal operation and diverts the current to the first branch during faults.

    The proposed design for the second branch is an LC (inductor-capacitor) resonance circuit at each of the three-phases with a resonant frequency matching the system frequency during fault conditions. The resonant circuit however does not represent a resonance circuit during normal conditions because the inductor and the capacitor of each LC circuit are subjected to voltages with similar amplitudes but different phase angles....