Control of small distributed energy resources
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Abstract
A method of controlling the output inverter of a microsource in a distributed energy resource system is disclosed. Embodiments of the invention include using unit or zone power controllers that reduce the operating frequency of the inverter to increase its unit output power. Preferred embodiments includes methods wherein the inverter reaches maximum output power and minimum operating frequency at the same time, and further comprising using a voltage controller implementing a voltage vs. reactive current droop. Other aspects of this embodiment relate to an inverter that implements such methods, and a microsource containing such an inverter. These methods can be extended to control inverters in a plurality of microsources, organized in a single zone or in a plurality of zones.
53 Citations
33 Claims
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1. (canceled)
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2. A method of controlling distributed energy resources connectable to a utility grid having a connection point, the utility supplying AC power at an operating frequency ω
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0, the method comprising;
(a) providing a microgrid having a power bus and a load, the microgrid having a grid mode wherein the power bus is electrically connected with the connection point for a grid power flow and an island mode wherein the grid power flow is substantially zero, the grid power flow being positive when the microgrid imports power from the utility grid and the grid power flow being negative when the microgrid exports power to the utility grid;
(b) providing a first microsource delivering AC power to the power bus at a selectable frequency ω
1 and a selectable power level P1, and having a grid mode power set point P10;
(c) providing a second microsource delivering AC power to the power bus at a selectable frequency ω
2 and a selectable power level P2, and having a grid mode power set point P20; and
(d) operating the microgrid in grid mode, wherein ω
1≈
ω
o and P1≈
P10, and wherein ω
2≈
ω
0 and P2≈
P20;
(e) transferring the microgrid from grid mode to island mode; and
(f) operating the microgrid in island mode, wherein ω
1≈
ω
island and P1≈
P1island, and wherein ω
2≈
ω
island and P2≈
P2island,wherein ω
island>
ω
0, P1island<
P10, and P2island<
P20 if the microgrid was exporting power prior to entering island mode, andwherein ω
island<
ω
0, P1island>
P10, and P2island>
P20 if the microgrid was importing power prior to entering island mode. - View Dependent Claims (3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
-
0, the method comprising;
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21. An apparatus connectable to a utility grid having a connection point, the utility supplying AC power at an operating frequency ω
- , the apparatus comprising;
(a) a microgrid having a power bus and a load, the microgrid having a grid mode wherein the power bus is electrically connected with the connection point for a grid power flow and an island mode wherein the grid power flow is substantially zero, the grid power flow being positive when the microgrid imports power from the utility grid and the grid power flow being negative when the microgrid exports power to the utility grid;
(b) a first microsource delivering AC power to the power bus at a selectable frequency ω
1 and a selectable power level P1, and having a grid mode power set point P10;
(c) a second microsource delivering AC power to the power bus at a selectable frequency ω
2 and a selectable power level P2, and having a grid mode power set point P20;
wherein when the microgrid operates in the grid mode ω
1≈
ω
0, P1≈
P10, ω
2≈
ω
0, and P2≈
P20;
wherein when the microgrid operates in the island mode ω
1≈
ω
island, P1≈
P1island, ω
2≈
ω
island, and P2≈
P2island,wherein ω
island>
P1island<
P10, and P2island<
P20 if the microgrid was exporting power prior to entering island mode, andwherein ω
island<
ω
0, P1island>
P10, and P2island>
P20 if the microgrid was importing power prior to entering island mode. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33)
- , the apparatus comprising;
Specification