Measurement-based dynamic modeling of an electrical network
A system and a method for locally controlling delivery of electrical power along the distribution feeder by measuring certain electricity parameters of a distribution feeder line using a substation phasor measurement unit (PMU) electrically coupled to a substation distribution bus at a first node on the feeder line, and at least one customer site PMU electrically coupled to a low voltage end of a transformer at a customer site, wherein the transformer is coupled by a drop line to a second node on the distribution feeder line and the customer site is coupled by another drop line to the transformer, and by controlling at least one controllable reactive power resource and optionally a real power resource connected to the second node or at the customer site. Related apparatus, systems, articles, and techniques are also described.
1. For managing an electrical grid distribution feeder line responsively to characterized electrical parameters thereat, the line having a first line node being a substation with an associated voltage controller that is adapted to control the voltage thereat, and, downstream thereof, a second line node that is electrically coupled to a customer's energy resource, a method of characterizing the voltage phasor at the second line node for a period of time, comprising:
(i) coupling a first μPMU at said first line node that is adapted to timestamp measure the electrical voltage and current waveforms thereat;
(ii) (a) coupling a voltage transformer between said second line node and said customer's energy resource with drop lines, and (b) coupling a second μPMU on the drop between the transformer and said customer's energy resource, that is adapted to timestamp measure the electrical voltage and current waveforms thereat;
(iii) making said first μPMU timestamped measurements and making said second μPMU timestamped measurements and time-synchronizing one of said first μPMU timestamped measurements with one of said second μPMU timestamped measurements;
(iv) determining, for the period, the impedances of said drop lines and said transformer between said second line node and said customer's energy resource;
(v) determining, for the period, the voltage at the second line node based on said drop line impedances and said transformer impedance and said second μPMU measurements; and
(vi) informing said determined second line node voltage, to said voltage controller.
2. The method of claim 1 wherein the customer's energy resource includes a resource controller that is adapted to control the energy resource to change its real or reactive power consumption or generation to cause a change in the voltage waveforms at the second line node, and the voltage controller is adapted to determine voltage control targets for the substation and the customer's energy resource, and wherein the method further comprises:
(vii) determining a voltage target for the customer's energy resource coupled to the second line node;
(vii) determining a voltage target for the substation; and
(viii) informing said determined voltage target at the second line node to customer's energy resource controller to adjust the voltage thereat.
3. The method of claim 2 wherein the voltage target for the substation control and the voltage target for the customer's energy resource control are determined to reduce the amount of substation control needed.
4. The method of claim 2 , wherein the voltage target for the substation control and the voltage target for the customer's energy resource control are determined to reduce the amount of energy lost in the feeder line.
5. The method of claim 2 , wherein the voltage target for the substation control and the voltage target for the customer's energy resource control are determined to trade off between the amount of substation control and the amount of energy loss in the feeder line.
6. The method of claim 2 , wherein the trade off between substation control and energy loss is based on the cost of wear-and-tear on the substation equipment and the value of the energy lost in the feeder line.
7. The method of claim 2 , wherein the voltage target for the substation control and the voltage target for the customer's energy resource control are determined to optimally minimize reactive power flow in the feeder line subject to the constraints of the substation control and the customer's energy resource and the costs of the wear-and-tear on the substation control and the impact to the customer of controlling its energy resource.
8. A non-transitory computer-readable medium having computer-executable instructions stored thereon which, when executed by a computer, will cause the computer to perform the following steps, in the management of an electrical grid distribution feeder line responsively to characterized electrical parameters thereat, the line having a first line node being a substation associated with a voltage controller adapted to control the voltage thereat, and, downstream thereof, a second line node that is electrically coupled to a customer's energy resource (that generates or consumes electrical power), to characterizing the voltage phasor at the second line node for a period of time, the steps comprising:
(i) coupling a first μPMU at said first line node that is adapted to timestamp measure the electrical voltage and current waveforms thereat;
(ii) (a) coupling a voltage transformer between said second line node and said customer's energy resource with drop lines, and (b) coupling a second μPMU on the drop between the transformer and said customer's energy resource, that is adapted to timestamp measure the electrical voltage and current waveforms thereat;
(iii) making said first μPMU timestamped measurements and making said second μPMU timestamped measurements and time-synchronizing one of said first μPMU timestamped measurements with one of said second μPMU timestamped measurements;
(iv) determining, for the period, the impedances of said drop lines and said transformer between said second line node and said customer's energy resource;
(v) determining, for the period, the voltage at the second line node based on said drop line impedances and said transformer impedance and said second μPMU measurements; and
(vi) informing said determined second line node voltage, to said voltage controller.
9. The medium of claim 8 wherein the customer's energy resource has a resource controller that is adapted to control the energy resource to change its real or reactive power consumption or generation to predictably cause a change in the voltage waveforms at the second line node, and the voltage controller is adapted to determine voltage control targets for the substation and the customer's energy resource, and additionally comprises the steps:
(vii) determining a voltage target for the customer's energy resource coupled to the second line node; and
(vii) determining a voltage target for the substation; and
(viii) informing said determined voltage target at the second line node to customer's energy resource controller to adjust the voltage thereat.
10. The medium of claim 8 wherein the voltage target for the substation control and the voltage target for the customer's energy resource control are determined to reduce the amount of substation control needed.
11. The medium of claim 8 , wherein the voltage target for the substation control and the voltage target for the customer's energy resource control are determined to reduce the amount of energy lost in the feeder line.
12. The medium of claim 8 , wherein the voltage target for the substation control and the voltage target for the customer's energy resource control are determined to trade off between the amount of substation control and the amount of energy loss in the feeder line.
13. The medium of claim 8 , wherein the trade off between substation control and energy loss is based on the cost of wear-and-tear on the substation equipment and the value of the energy lost in the feeder line.
14. The medium of claim 8 , wherein the voltage target for the substation control and the voltage target for the customer's energy resource control are determined to optimally minimize reactive power flow in the feeder line subject to the constraints of the substation control and the customer's energy resource and the costs of the wear-and-tear on the substation control and the impact to the customer of controlling its energy resource.
15. For the management of an electrical grid distribution feeder line responsively to characterized electrical parameters thereat, the line having a first line node being a substation with an associated voltage controller adapted to control the voltage thereat, and, downstream thereof, a second line node that is electrically coupled to a customer's energy resource (that generates or consumes electrical power), a system for characterizing the voltage phasor at the second line node for a period of time, the system comprising:
(i) a first μPMU at said first line node that takes timestamped measurements of the electrical voltage and current waveforms thereat;
(ii) (a) a voltage transformer coupled between said second line node and said customer's energy resource with drop lines, and (b) a second μPMU coupled on the drop between the transformer and said customer's energy resource, that is adapted to timestamp measure the electrical voltage and current waveforms thereat;
(iii) a common time source that is communicatively shared by said first μPMU and said second μPMU to act as a common reference to said timestamps;
(iv) to determine, for the period, the impedances of said drop lines between said transformer and said customer's energy resource;
(v) to determine, for the period, the voltage at the second line node based on said drop line impedances and said transformer impedance and said second μPMU measurements; and
(vi) to inform said determined second line node voltage, to substation voltage controller.
16. The system of claim 15 , wherein the customer's energy resource has a resource controller that is adapted to control the energy resource to change its real or reactive power consumption or generation to predictably cause a change in the voltage waveforms at the second line node, and the voltage controller is adapted to determine voltage control targets for the substation and the customer's energy resource, and additionally comprises the steps:
(vii) determining a voltage target for the customer's energy resource coupled to the second line node; and
(vii) determining a voltage target for the substation; and
(viii) informing said determined voltage target at the second line node to customer's energy resource controller to adjust the voltage thereat.
17. The system of claim 16 , wherein the voltage target for the substation control and the voltage target for the customer's energy resource control are determined to reduce the amount of substation control needed.
18. The system of claim 16 , wherein the voltage target for the substation control and the voltage target for the customer's energy resource control are determined to reduce the amount of energy lost in the feeder line.
19. The system of claim 16 , wherein the voltage target for the substation control and the voltage target for the customer's energy resource control are determined to trade off between the amount of substation control and the amount of energy loss in the feeder line.
20. The system of claim 16 , wherein the trade off between substation control and energy loss is based on the cost of wear-and-tear on the substation equipment and the value of the energy lost in the feeder line.
21. The system of claim 16 , wherein the voltage target for the substation control and the voltage target for the customer's energy resource control are determined to optimally minimize reactive power flow in the feeder line subject to the constraints of the substation control and the customer's energy resource and the costs of the wear-and-tear on the substation control and the impact to the customer of controlling its energy resource.