Decentralized optimal dispatch of photovoltaic inverters in power distribution systems

Patent metadata

Field	Value
Publication number	US-10139800-B2
Application number	US-201615061515-A
Country	US
Kind code	B2
Filing date	Mar 4, 2016
Priority date	Mar 5, 2015
Publication date	Nov 27, 2018
Grant date	Nov 27, 2018

Abstract

Decentralized methods for computing optimal real and reactive power setpoints for residential photovoltaic (PV) inverters are described. Optimal power flow techniques are described that select which inverters will provide ancillary services and compute their optimal real and reactive power setpoints according to specified performance criteria and economic objectives.

First claim

The invention claimed is:

1. A method, the method comprising:
storing, with a control device of a power distribution network, an optimal inverter dispatch (OID) model for controlling the real and reactive power produced by photovoltaic inverters installed at respective customer sites and connected to a utility by the power distribution network, wherein the model includes data representing estimated voltages at nodes within the power distribution network and an amount of active and reactive power currently being produced by each of the photovoltaic inverters, and wherein the OID model specifies a set of one or more cost constraints for the utility;
receiving, with the control device, messages from customer controllers at each of the customer sites, wherein each of the messages specify current measurements for the amount of active and reactive power currently being produced by the photovoltaic inverter installed at the respective customer site;
determining, by the control device and based on the OID model and the current measurements, set points for the active and reactive power to be produced by each of the photovoltaic inverters of the customer sites by performing a minimization operation over the cost constraints for the utility; and
communicating, by the control device, to the customer controllers at each of the customer sites, the updated set points for the active and reactive power to photovoltaic inverters.

2. The method of claim 1 ,
wherein the OID model comprises a semidefinite relaxation programming model that expresses the active power and reactive power for the photovoltaic inverters and the cost constraints as linear functions; and
wherein processing the OID model comprises computing the set points as a convex minimization for the estimates of the active and reactive power to be produced at each of the PV inverters.

3. The method of claim 1 , wherein determining the set points comprises determining, for each of the photovoltaic inverters, updated set points based on a difference between previous set points for the active and reactive power of the photovoltaic inverter and the active and reactive power currently being produced by the photovoltaic inverter.

4. The method of claim 3 , wherein determining the set points comprises:
responsive to receiving the messages from the customer controllers at each of the customer sites, updating, by the control device, one or more coefficients in the OID model based on the difference between the current set points for the active and reactive power and the active and reactive power currently being produced by the photovoltaic inverters;
computing, by the control device, the updated set points based on the updated coefficients; and
repeatedly, by the control device:
sending the updated set points to the customer controllers at each of the customer sites,
receiving the messages from the customer controllers at each of the customer sites,
updating the coefficients, and
computing additional updates to the set points until the set points for the active and reactive power and the current measurements for the active and reactive power converge within a threshold difference.

5. The method of claim 1 , further comprising:
measuring, at each of the customer sites with the customer controllers at each of the customer sites, active and reactive power currently being produced by the respective photovoltaic inverters;
receiving, with each of the customer controllers, the messages from the control device specifying the updated set points current for the active and reactive power to be produced by the photovoltaic inverter installed at the respective customer site;
computing, with each of the customer controllers, local set points based on a difference between the set points for the active and reactive power as received from the control device and the measured active and reactive power currently being produced by the photovoltaic inverters; and
controlling, with each of the customer controllers, the respective photovoltaic inverter in accordance with the local set points for the active and the reactive power.

6. The method of claim 5 , wherein computing, with each of the customer controllers, local set points comprises performing a minimization operation over cost incurred by the respective customer sites when the photovoltaic inverter for the customer site is required to curtail power generation.

7. The method of claim 1 , wherein the control device comprises multiple control devices, the method further comprising:
partitioning the power distribution network in to a plurality of clusters, each of the clusters comprising at least one of the multiple control devices and a respective subset of the customer sites; and
performing, with each of the at least one of the multiple control devices, the method of claim 1 to control the amount of active and reactive power currently being produced by each of the photovoltaic inverters of the respective subset.

8. The method of claim 1 , further comprising selecting, in real-time, a subset of the photovoltaic inverters to participate in the provisioning.

9. The method of claim 1 , wherein processing the OID model comprises applying alternating direction method of multipliers (ADMM).

10. A method comprising:
measuring, with a customer controller at a customer site, an amount of active and reactive power currently being produced by a photovoltaic inverter installed at the customer site;
receiving, with the customer controller, messages from a control device of a power distribution network of a utility coupled to the customer site by the power distribution network, wherein the messages specify set points for the amount of active and reactive power to be produced by the photovoltaic inverter installed at the respective customer site;
computing, with the customer controller, local set points based on a difference between the set points for the active and reactive power as received from the control device and the measured active and reactive power currently being produced by the photovoltaic inverters; and
controlling, with the customer controller, the respective photovoltaic inverter in accordance with the local set points for the active and the reactive power.

11. The method of claim 10 , wherein computing the local set points comprises performing a minimization operation over cost incurred by the customer controller at the customer site when the photovoltaic inverter for the customer site is required to curtail power generation.

12. A system comprising:
a control device for a power distribution network of a power utility;
a plurality of customer sites having customer controllers and respective photovoltaic inverters coupled to the power utility by the power distribution network,
wherein the control device stores an optimal inverter dispatch (OID) model for controlling real and reactive power produced by photovoltaic inverters installed at the customer sites, the OID model specifying a set of one or more cost constraints for the utility, and
wherein the control device is configured to:
receive messages from the customer controller at each of the customer sites, wherein each of the messages specify current measurements for the amount of active and reactive power currently being produced by the photovoltaic inverter installed at the respective customer site,
determine, based on the OID model and the current measurements, set points for the active and reactive power to be produced by each of the photovoltaic inverters of the customer sites by performing a minimization operation over the cost constraints for the utility, and
communicate, to the customer controllers, the updated set poi

Assignees

• Univ Minnesota

Inventors

• Dhople Sairaj
• Giannakis Georgios B
• Dall'Anese Emiliano

Classifications

• H02J2103/30

  Simulating, planning, modelling, reliability check or computer assisted design [CAD] of electric power networks · CPC title

• H02J2101/24

  Photovoltaics · CPC title

• H02J13/1335

  involving a local wireless network, e.g. Wi-Fi®, ZigBee® or Bluetooth® · CPC title

• H02J13/1333

  by means of mobile telephony · CPC title

• H02J13/333

  the equipment forming part of substations · CPC title