ZERO DROOP VOLTAGE CONTROL FOR SMART INVERTERS

• US 20170040799A1
• Filed: 10/21/2016
• Published: 02/09/2017
• Est. Priority Date: 09/16/2011
• Status: Active Grant

• Current Assignee: Sentient Energy Technology LLC (KOCH Industries Incorporated)
• Original Assignee: Varentec Incorporated (KOCH Industries Incorporated)
• Inventors: Divan, DEEPAKRAJ, MOGHE, ROHIT
• Granted Patent: US 9,948,100 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G05F 1/66 Regulating electric power
• CPC Class Codes: H02J 3/12 for adjusting voltage in ac networks by changing a characteristic of the network load
• CPC Class Codes: H02J 3/1828 with stepwise control, the possibility of switching in or out the entire compensating arrangement not being considered as stepwise control
• CPC Class Codes: Y02E 40/30 Reactive power compensation

Abstract

Systems and methods for controlling grid voltage include a distribution power network and one or more smart inverters at or near the edge of the distribution power network, each smart inverter configured to absorb or insert VARs to control the voltage based on a reference Q value, wherein the reference Q value is calculated by a reference Q calculator. A reference Q calculator includes a processor and a non-transitory computer readable memory with software embedded thereon, the software configured to cause the processor to receive a voltage measurement taken at or near the edge of a power distribution grid, a voltage band value, and a voltage set point value, determine a difference, e_v, between the voltage measurement and the voltage set point, generate a new reference Q value if an absolute value of e_v is greater than the voltage band value, and cause the smart inverter to either absorb or insert VARs depending on the sign of e_v.

Claims

1. A system for controlling grid voltage with a smart inverter, the system comprising:

a distribution power network;

a smart inverter at or near an edge of the distribution power network, the smart inverter configured to, based on a reference Q value, either insert VARs or absorb VARs at or near the edge of the power grid; and

a reference Q calculator communicatively coupled to or embedded on a controller disposed within the smart inverter, the reference Q calculator comprising a processor and a non-transitory computer readable memory with software embedded thereon, the software configured to cause the processor to;

receive a voltage measurement taken at or near the edge of a power distribution network, a voltage band value, and a voltage set point value;

determine a difference, e_v, between the voltage measurement and the voltage set point; and

generate a new reference Q value if an absolute value of e_v is greater than the voltage band value.

2. The system of claim 1, wherein the new reference Q value is set to trigger the smart inverter to absorb VARs if e_v is negative in value.

3. The system of claim 1, wherein the new reference Q value is set to cause the smart inverter to inject VARs if e_v is positive in value.

4. The system of claim 1, wherein the software is further configured to cause the processor to generate the new reference Q value as a function of e_v².

5. The system of claim 4, wherein the software is further configured to cause the processor to generate the new reference Q value as a function of a randomized gain value, K_q.

6. The system of claim 1, wherein the reference Q calculator is disposed within the smart inverter.

7. The system of claim 1, wherein the reference Q calculator is external to the smart inverter.

8. The system of claim 7, wherein the software is further configured to cause the processor to receive a maximum Q reference value and to limit the new reference Q value to the maximum Q reference value.

9. The system of claim 8, wherein the software is further configured to cause the processor to set a delay timer if the voltage measurement is oscillating and to maintain a current reference Q value until the delay timer expires.

10. The system of claim 9, wherein the software is further configured to cause the processor to receive a rating S, and the maximum Q reference value is set as function of S.

11. The system of claim 1, wherein the voltage band value is set by a user.

12. A method of controlling voltage by inserting or absorbing VARs at or near an edge of a power distribution grid implemented by a smart inverter, the method comprising:

receiving a voltage measurement from an edge of a power distribution network, a voltage band value, and a voltage set point value;

determining a difference, e_v, between the voltage measurement and the voltage set point; and

generating a new reference Q value if an absolute value of e_v is greater than the voltage band value.

13. The method of claim 12, further comprising causing the smart inverter to absorb VARs, based on the new reference Q value, if e_v is negative in value.

14. The method of claim 12, further comprising causing the smart inverter to inject VARs, based on the new reference Q value, if e_v is positive in value.

15. The method of claim 12, wherein the new reference Q value is generated as a function of e_v².

16. The method of claim 15, further comprising generating a randomized gain value, K_q, wherein the new reference Q value is generated as a function of K_q.

17. The method of claim 16, further comprising generating a maximum Q reference value and to limiting the new reference Q value to the maximum Q reference value.

18. The method of claim 17, further comprising receiving a rating S and generating the maximum Q reference value as a function of S.

19. The method of claim 12, further comprising setting a delay if the voltage measurement is oscillating and maintaining a current reference Q value until the delay expires.

20. The method of claim 19, further comprising generating a randomized value, K_T, wherein the delay is set as a function of K_T and e_v is generated as a function of K_q.