Voltage collapse diagnostic and ATC system

• US 20050033480A1
• Filed: 06/28/2004
• Published: 02/10/2005
• Est. Priority Date: 06/27/2003
• Status: Active Grant

• Current Assignee: Intelilcon Incorporated
• Original Assignee: Benjamin Ashton Minshall, Robert Schlueter, Ryan Joseph Hunt
• Inventors: Hunt, Ryan Joseph, Minshall, Benjamin Ashton, Schlueter, Robert
• Granted Patent: US 7,194,338 B2
• Time in Patent Office: Days
• US Class Current: 700/286
• CPC Class Codes: H02J 2203/20 Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]
• CPC Class Codes: H02J 2310/60 Limiting power consumption in the network or in one section of the network, e.g. load shedding or peak shaving
• CPC Class Codes: H02J 3/00 Circuit arrangements for ac mains or ac distribution networks
• CPC Class Codes: H02J 3/0012 Contingency detection
• CPC Class Codes: H02J 3/003 Load forecast, e.g. methods or systems for forecasting future load demand
• CPC Class Codes: H02J 3/144 Demand-response operation of the power transmission or distribution network
• CPC Class Codes: H02J 3/16 by adjustment of reactive power
• CPC Class Codes: H02J 3/24 Arrangements for preventing or reducing oscillations of power in networks by control effected upon a single generator H02P9/00
• CPC Class Codes: Y02B 70/3225 Demand response systems, e.g. load shedding, peak shaving
• CPC Class Codes: Y02E 40/30 Reactive power compensation
• CPC Class Codes: Y02E 60/00 Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
• CPC Class Codes: Y04S 20/222 Demand response systems, e.g. load shedding, peak shaving
• CPC Class Codes: Y04S 40/20 Information technology specific aspects, e.g. CAD, simulation, modelling, system security

Abstract

The present invention provides an analysis method for an electrical power system whereby the plurality of buses are grouped into agents, family lines of agents and families of agents based on the reactive reserves depleted when the buses are loaded. Contingencies are then applied to the electrical power system and the reactive reserves are monitored and an exhaustion factor is determined for one or more family lines in one ore more families. A method for selecting double outage that have no solution for each outage that has no solution when the outage is removed in small steps and an additional step has no solution. The boundary case solution is used to assess where, why, and how the contingency causes voltage instability, voltage collapse, and local blackout. Based on this information, the design of voltage rescheduling, active rescheduling, unit commitment, load shedding is determined that can be used as preventive, corrective, or emergency controls in applications such as system design and planning, operation planning, reactive and voltage management, real time control, and Special Protection System Control. Based on this information, solutions can then be applied to the political power system.

Claims

1. A voltage collapse diagnosis method for an electrical power system, comprising:

defining a plurality of buses and a plurality of reactive reserves in the electrical power system as a plurality of a agents; and

identifying an exhaustion for each of the agents in response to applying at least one contingency applied to the electrical power system;

wherein the agents are defined such that each agent is supported by similar reactive reserves.

2. The voltage collapse diagnosis method according to claim 1, further comprising:

selecting the plurality of buses in the electrical power system to be defined as the plurality of agents;

wherein the plurality of buses selected in the selecting step are defined by a buffer zone.

3. The voltage collapse diagnosis method according to claim 2, wherein at least one of the plurality of buses in the buffer zone has a real load.

4. The voltage collapse diagnosis method according to claim 2, wherein the buffer zone includes at least one bus located in a sub transmission or distribution level in the electrical power system.

5. The voltage collapse diagnosis method according to claim 4, wherein the at least one bus is at a voltage level of at or less than about 34 KV.

6. The voltage collapse diagnosis method according to claim 1, wherein the electrical power system is a model of an existing electrical power system and the contingency is a simulated contingency.

7. The voltage collapse diagnosis method according to claim 1, wherein the identifying step comprises:

applying a load to each of the plurality of buses;

monitoring a power output from each of the plurality of reactive reserves in response to the load applied to each of the plurality of buses;

identifying any of the plurality of reactive reserves that become about completely exhausted when no solution exists for a load flow equation calculated in conjunction with the applying step for each of the plurality of buses; and

defining the plurality of agents according to the plurality of buses and reactive reserves such that each agent contains buses that exhaust a same set of reactive reserves when no solution exists for the load flow equation for the buses of the respective agent;

wherein the same set of reactive reserves that exhaust for each agent are defined as a reactive reserves basin for each agent; and

wherein a plurality of reactive reserve zones exists for the plurality of agents.

8. The voltage collapse diagnosis method according to claim 7, wherein:

the load applied in the applying step is a simulated load;

the reactive reserves are simulated reactive reserves; and

the electrical power system is a model of an existing electrical power system.

9. The voltage collapse diagnosis method according to claim 7, further comprising organizing the plurality of agents into a hierarchy based on the plurality of reactive reserve zones.

10. The voltage collapse diagnosis method according to claim 9, wherein agents at a higher level in the hierarchy include more reactive reserves than agents at a lower level in the hierarchy.

11. The voltage collapse diagnosis method according to claim 10, wherein agents at a higher level in the hierarchy are at a higher voltage level than agents at a lower level in the hierarchy.

12. The voltage collapse diagnosis method according to claim 11, wherein:

at least some of the agents at lower levels in the hierarchy have reactive reserves basins with subsets of reactive reserves contained in reactive reserve zones for agents at higher levels in the hierarchy; and

family lines of agents are defined based on agents at lower levels in the hierarchy having subsets of reactive reserves contained in agents at higher levels in the hierarchy.

13. The voltage collapse diagnosis method according to claim 7, wherein the step of identifying an exhaustion of the each of the agents further comprises:

applying a single contingency of to the electrical power system; and

monitoring a change in power output of the reactive reserves.

14. The voltage collapse diagnosis method according to claim 13, wherein the step of identifying an exhaustion of each of the agents further comprises:

calculating an exhaustion factor for each agent for each single contingency; and

ranking each of the agents according to a respective exhaustion factor calculated in the calculating step.

15. The voltage collapse diagnosis method according to claim 14, wherein the exhaustion factor for each agent is calculated based on:

$\mathrm{exhaustion}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{factor}=\left(\frac{Q<br><br>\text{\hspace{1em}<br><br>}<br><br>\max -\mathrm{QgenOutage}}{Q<br><br>\text{\hspace{1em}<br><br>}<br><br>\max -\mathrm{QgenBase}}\right)·<br><br>100$

wherein Qmax is a maximum power generated the reactive reserve zone for each agent, QgenOutage is power generated by the reactive reserve zone for each agent in response to the contingency, and QgenBase is a base power output generated by the reactive reserve zone for each agent.

16. The voltage collapse diagnosis method according to claim 14, further comprising:

selecting a number of agents;

determining a threshold value by multiplying exhaustion factors for each of number of agents times the number of agents for each single contingency;

identifying each single contingency is that results in the threshold value being above a predetermined amount; and

performing a multiple contingency analysis with each single contingency identified in the identifying each single contingency step.

17. The voltage collapse diagnosis method according to claim 16, wherein the multiple contingency analysis comprises:

applying combinations of each single contingency identified in the identifying each single contingency step to the electrical power system; and

monitoring a change in power output of the reactive reserve zones for each of the agents.

18. The voltage collapse diagnosis method according to claim 17, wherein the step of determining an exhaustion of each agent further comprises:

calculating an exhaustion factor for each agent for each of the combinations of each single contingency; and

ranking each of the agents according to the exhaustion factor calculated for each of the agents for each single contingency and each of the combinations of each single contingency.

19. The voltage collapse diagnosis method according to claim 18, wherein the exhaustion factor for each agent is calculated based on:

$\mathrm{exhaustion}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{factor}=\left(\frac{Q<br><br>\text{\hspace{1em}<br><br>}<br><br>\max -\mathrm{QgenOutage}}{Q<br><br>\text{\hspace{1em}<br><br>}<br><br>\max -\mathrm{QgenBase}}\right)·<br><br>100$

wherein Qmax is a maximum power generated the reactive reserve zone for each agent, QgenOutage is power generated by the reactive reserve zone for each agent in response to the contingency, and QgenBase is a base power output generated by the reactive reserve zone for each agent.

20. The voltage collapse diagnosis method according to claim 19, further comprising:

determining preventive measures to support power flow on the electrical power system based on the ranking of each single contingency and each of the combinations of each single contingency.

21. The voltage collapse diagnosis method according to claim 20, further comprising a means for determining and executing the preventive measures.

22. The voltage collapse diagnosis method according to claim 20, wherein the preventive measures include shifting load, adding new generation, rescheduling active power on-existing reactive reserves or rescheduling voltage for strengthening the electrical power system in critical locations.

23. The voltage collapse diagnosis method according to claim 7, wherein the step of identifying an exhaustion of the each of the agents further comprises:

applying a plurality of contingencies to the electrical power system; and

monitoring a change in power output of the reactive reserve zones for each of the agents.

24. The voltage collapse diagnosis method according to claim 23, further comprising the step of ranking the plurality of contingencies in order of most critical contingencies.

25. The voltage collapse diagnosis method according to claim 24, wherein the step of ranking the plurality of contingencies is calculated according to:

$\mathrm{Cj}=\sum <br><br>j<br><br>\text{\hspace{1em}<br><br>}<br><br>\frac{P_j<br><br>\left(-1+\%<br><br>{\mathrm{reactivereservesremaining}}_{\mathrm{ij}}\right)}{1-\%<br><br>{\mathrm{outageremaining}}_{\mathrm{ij}}}$

26. The voltage collapse diagnosis method according to claim 23, further comprising the step of ranking the agents in order of most critical agents based on the plurality of contingencies.

27. The voltage collapse diagnosis method according to claim 25, wherein the step of ranking each of the agents is calculated according to:

$A_j=\sum <br><br>i<br><br>\text{\hspace{1em}<br><br>}<br><br>\frac{P_j<br><br>\left(-1+\%<br><br>{\mathrm{reactivereservesremaining}}_{\mathrm{ij}}\right)}{1-\%<br><br>{\mathrm{outageremaining}}_{\mathrm{ij}}}$

28. The voltage collapse diagnosis method according to claim 17, further comprising the step of determining an available transfer capability for each of the combinations of each single contingency and a control region or load pocket.

29. The voltage collapse diagnosis method according to claim 28, wherein the step of determining an available transfer capability for the comprises:

identifying each of the combinations of each single contingency that results in no load flow solution;

performing load shedding until a load flow solution exists;

determining a remaining amount of reserves available in the combinations of each single contingency before no load flow solution exists; and

defining of a remaining amount of reserves as a incremental transfer capability.

30. The voltage collapse diagnosis method according to-claim 29, wherein the step of determining a remaining amount of reserves for the comprises:

applying only one contingency in each one of the combinations of each single contingency;

placing a load on the control region or load pocket to compensate for the application of only one contingency in the applying step; and

determining an additional load that can be applied to the control region or load pocket before no load flow solution exists as the remaining amount of reserves available.

31. The voltage collapse diagnosis method according to claim 13, further comprising the step of determining an available transfer capability for each single contingency and a control region or load pocket.

32. The voltage collapse diagnosis method according to claim 31, wherein the step of determining an available transfer capability for the comprises:

identifying each single contingency that results in no load flow solution;

performing load shedding until a load flow solution exists;

determining a remaining amount of reserves available in the combinations of each single contingency before no load flow solution exists; and

defining of a remaining amount of reserves as a incremental transfer capability.

33. A method for determining criticality of a plurality of contingencies, comprising:

applying a voltage collapse diagnosis to an electrical power system, wherein a plurality of contingencies are applied to the electrical power system and responses from a plurality of agents are monitored; and

ranking the plurality of contingencies according to criticality.

34. The method according to claim 33, wherein the step of ranking is performed according to:

$\mathrm{Cj}=\sum <br><br>j<br><br>\text{\hspace{1em}<br><br>}<br><br>\frac{P_j<br><br>\left(-1+\%<br><br>{\mathrm{reactivereservesremaining}}_{\mathrm{ij}}\right)}{1-\%<br><br>{\mathrm{outageremaining}}_{\mathrm{ij}}}$

36. The method according to claim 33, wherein the step of ranking is performed according to:

$A_j=\sum <br><br>i<br><br>\text{\hspace{1em}<br><br>}<br><br>\frac{P_j<br><br>\left(-1+\%<br><br>{\mathrm{reactivereservesremaining}}_{\mathrm{ij}}\right)}{1-\%<br><br>{\mathrm{outageremaining}}_{\mathrm{ij}}}$

35. A method for determining criticality of a plurality of agents, comprising:

applying a voltage collapse diagnosis to an electrical power system, wherein a plurality of contingencies are applied to the electrical power system and responses from a plurality of agents are monitored; and

ranking the plurality of agents according to criticality.

37. A method for determining an available transfer capability, comprising determining an amount of power that is available for transfer into a load pocket or control area.

38. The method according to claim 37, wherein the determining step is a function of firm and non-firm transfer into the load pocket, a Transmission Reliability Margin and a Capacity Benefit Margin for a load pocket.

39. The method according to claim 37, wherein the determining step further comprises:

performing a voltage collapse diagnosis;

identifying contingencies having no load flow solution;

load shedding at the load pocket or control area until the contingencies have a load flow solution; and

determining a remaining amount of reserves available.

40. The method according to claim 37, wherein the determining step further comprises:

identifying combinations of single contingencies that have no load flow solution;

performing load shedding at the load pocket or control area until a load flow solution exists;

determining a remaining amount of reserves available in the combinations of each single contingency before no load flow solution exists.

41. The voltage collapse diagnosis method according to claim 40, wherein the step of determining a remaining amount of reserves for the comprises:

applying only one contingency in each one of the combinations;

placing a load on the control region or load pocket to compensate for the application of only one contingency in the applying step; and

determining an additional load that can be applied to the control region or load pocket before no load flow solution exists.

42. The voltage collapse diagnosis method according to claim 37, further comprising:

assigning a value to the control region or load pocket based on the amount of power representative of the criticality of the control region or load pocket.

43. The voltage collapse diagnosis method according to claim 42, further comprising:

determining a value of power based on the value determined in the assigning a value step.