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System and method for responding to abrupt load changes on a power system

  • US 7,474,016 B2
  • Filed: 05/23/2006
  • Issued: 01/06/2009
  • Est. Priority Date: 05/23/2006
  • Status: Active Grant
First Claim
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1. A micro grid system electrically transferring power from at least one external power source to an alternating current (AC) power system, comprising:

  • a direct current (DC) bus operable at a nominal DC voltage;

    a primary converter module electrically coupled between the DC bus and a first external power source, and operable to transfer an initial amount of power received from the first external power source to the DC bus;

    a secondary converter module electrically coupled between the DC bus and the AC power system, and operable to transfer power received from the DC bus to the AC power system;

    an auxiliary DC power storage device electrically coupled to the DC bus, and operable to source or sink auxiliary DC power to the DC bus, where, in response to an abrupt load change, the auxiliary DC power storage device sources or sinks an amount of auxiliary DC power that is equal to at least a portion of the abrupt load change, the primary converter module maintains transfer of the initial amount of power received from the first external power source, and the secondary converter module changes power transferred to the AC power system to approximately match a sum of the initial amount of power received from the first external power source and the amount of auxiliary DC power; and

    a second primary converter module electrically coupled between the DC bus and a second external power source, and operable to transfer a second initial amount of power received from the second external power source to the DC bus, where in response to the abrupt load change, the secondary converter module changes lower transferred to the AC power system to at least approximately match the sum of the initial amount of power received from the first external power source, the second initial amount of power received from the second external power source, and the amount of auxiliary DC power, wherein responsive to the abrupt load change, the second primary converter module maintains transfer of the second initial amount of power received from the second external power source and after responding to the abrupt load change, the auxiliary DC power storage devce changes the amount of auxiliary DC power from the portion of the abrupt load change to approximately a zero amount of power in accordance with a power change function during a power transfer period, the primary converter module changes power recieved from the first external power source by a first portion of the abrupt load change in accordance with an inverse of the power change function during the power transfer period;

    an the second primary converter module changes power received from the second external power source by a second portion of the abrupt load change in accordance with the inverse of the power change function during the power transfer period.

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