Patent ID: 7687937

Claim:
A method of controlling distributed energy resources, the method comprising: providing a microsource, wherein the microsource is located in a microgrid, and further wherein the micro source is configured to deliver a power P 1 at a frequency ω1; operating the microsource in a grid mode in which the microsource is connected to a utility grid, wherein during operation in the grid mode the frequency ω1 is approximately equal to a frequency ω o and the power P 1 is equal to a power P 1 o , wherein the frequency ω o is an operating frequency of the utility grid; and transferring the microsource from the grid mode to an island mode such that the microsource is disconnected from the utility grid, wherein ω1 is equal to ω island and P 1 is equal to P 1 island during the island mode; wherein ω island >ω 0 , and P 1 island <P 1 0 if the microgrid was exporting power prior to the transfer from the grid mode to the island mode; wherein ω island <ω 0 , and P 1 island >P 1 0 if the microgrid was importing power prior to the transfer from the grid mode to the island mode; and wherein the microsource delivers a maximum power output level P 1 max at a frequency ω min , wherein the microsource has a slope switch frequency ω switch , and ω island ≈ ω 0 ⁡ ( ω 0 - ω min P ⁢ ⁢ 1 0 - P ⁢ ⁢ 1 max ) ⁢ ( P ⁢ ⁢ 1 0 - P ⁢ ⁢ 1 island ) . ⁢ if ⁢ [ ω 0 - ( ω 0 - ω min P ⁢ ⁢ 1 0 - P ⁢ ⁢ 1 max ) ⁢ ( P ⁢ ⁢ 1 0 - P ⁢ ⁢ 1 island ) ] < ω max .