Voltage collapse diagnostic and ATC system

• US 8,024,076 B2
• Filed: 10/11/2005
• Issued: 09/20/2011
• Est. Priority Date: 06/27/2003
• Status: Expired due to Fees

• Current Assignee: Intelilcon Incorporated
• Original Assignee: Intelilcon Incorporated
• Inventors: Hunt, Ryan Joseph, Minshall, Benjamin Ashton, Schlueter, Robert
• Primary Examiner(s): Decady; Albert
• Assistant Examiner(s): Lee; Douglas S
• Application Number:
  US11/247,388
• Publication Number:
  US 20060030972A1
• Time in Patent Office: 2,170 Days
• Field of Search: 700/286, 700/292, 700/293, 700/295, 702/182, 703/18
• 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 3/00 Circuit arrangements for ac mains or ac distribution networks
• CPC Class Codes: H02J 3/0012 Contingency detection
• CPC Class Codes: Y02E 60/00 Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
• CPC Class Codes: Y04S 40/20 Information technology specific aspects, e.g. CAD, simulation, modelling, system security

Abstract

A plurality of buses of an electrical power system 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 applied and the reactive reserves are monitored to determine an exhaustion factor for one or more family lines in one or more families. A boundary case solution exists for each outage that has no solution when the outage is removed in small steps and an additional step has no solution and is used to assess where, why, and how the contingency causes voltage instability, voltage collapse and local blackout. Based on this information, the voltage rescheduling, active rescheduling, unit commitment and load shedding is determined that can be used as preventive, corrective or emergency controls in system design and planning, operation planning, reactive and voltage management, real time control, and Special Protection System Control.

Claims

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

A) defining a network of a plurality of interconnected busses and sources of reactive reserves;

B) defining groups of busses within said network such that when a reactive load is applied to any bus within a first group of said groups of busses, a same at least one source generally completely exhausts its reactive reserves;

C) establishing each group of busses defined in step B) as a respective voltage instability region, each of which is represented by a respective agent;

D) performing simulation of a plurality of single contingencies using equations that define the network;

E) selecting a count N of a number of agents to be considered;

F) determining a variable threshold value for a reactive remaining exhaustion Factor;

G) identifying each single contingency that results in the reactive remaining exhaustion factor for N number of agents being less than the threshold value, wherein the reactive remaining exhaustion factor is a value representing an amount of reactive power available in the respective agent in response to a contingency;

H) performing a multiple contingency analysis by combining single contingencies identified in step G); and

I) using results of the single contingencies and multiple contingency analysis to analyze a voltage response of at least a portion of the network.

2. The voltage collapse diagnostic method of claim 1, further comprising:

applying load incrementally to the network.

3. The voltage collapse diagnostic method of claim 1, further comprising:

J) for each at least one source exhausted in step B), associating that at least one source with every group within said groups of busses that cause exhaustion of the at least one source.

4. The voltage collapse diagnostic method according to claim 3, further comprising:

establishing each at least one source associated in step J) as a reactive reserve zone, wherein the network includes a plurality of reactive reserve zones.

5. The voltage collapse diagnostic method according to claim 1 wherein the network is a mathematical model of an existing electrical power system and the load is a simulated electrical load.

6. The voltage collapse diagnostic method according to claim 4, further comprising:

organizing the agents into a hierarchy based on the plurality of reactive reserve zones.

7. The voltage collapse diagnostic method according to claim 6 wherein agents at a higher level in the hierarchy include more sources of reactive reserves than agents at a lower level in the hierarchy.

8. The voltage collapse diagnostic method according to claim 6 wherein agents at a higher level in the hierarchy are at a higher voltage level than agents at a lower level in the hierarchy.

9. The voltage collapse diagnostic method according to claim 6, further comprising:

defining a control region including at least one load pocket based on the hierarchy; and

determining an available transfer capability for the control region for each single contingency that has no loadflow solution.

10. The voltage collapse diagnostic method according to claim 9 wherein the step of determining an available transfer capability comprises:

identifying each single contingency that results in no loadflow solution;

performing preventative load shedding in the control region until a loadflow solution exists for each single contingency;

determining a maximum amount of load that is shed over all single contingencies that utilize the control region for load shedding; and

defining of a minimum remaining amount of reactive reserves after each contingency and the load shedding for the control region as a possible incremental transfer capability for the control region.

11. The voltage collapse diagnostic of claim 10 where the maximum amount of load that is shed is another possible incremental transfer capability for the control region.

12. The voltage collapse diagnostic method according to claim 7, wherein agents at a higher level in the hierarchy are electrically proximate to a source of electrical power generation, and wherein agents at a lower level in the hierarchy are electrically distal to the source of electrical power generation.

13. The voltage collapse diagnostic method according to claim 7 wherein at least some of the agents at lower levels in the hierarchy have reactive reserve zones that are subsets of the sources of reactive reserves contained in reactive reserve zones for agents at higher levels in the hierarchy;

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

14. A voltage collapse diagnostic method of claim 13 wherein exhaustion of reactive reserves at a lower hierarchical level begins an accelerated exhaustion of the reactive reserves at a higher level in each family;

wherein applying a reactive load at a bus in the voltage instability region of a patriarchal agent sequentially exhausts reactive reserves of every agent in every family line in the family from a lowest hierarchical level to a highest hierarchical level, which is the patriarchal agent;

wherein applying an active power load at all buses in a vulnerability region of the family of the patriarchal agent exhausts the reactive reserves of every agent in every family line in the family from the lowest hierarchical level to the highest hierarchical level;

wherein applying a contingency incrementally sequentially exhausts reactive reserves from a lower hierarchical level to a higher hierarchical level in more than one family line in one or more families;

wherein exhaustion of reactive reserves in an agent can cause instability in that agent;

the method further comprising;

reducing active and reactive load and reducing reactive losses in a vulnerability region of an agent lower than the patriarchical agent in the family line to reduce the occurrence of voltage instability, voltage collapse and local blackout using knowledge that cascading exhaustion of reactive reserves for agents can cause progressive cascading instability in family lines including those agents;

wherein a family of agents is defined as all agents in all family lines emanating from the patriarchal agent to which the family belongs;

wherein the vulnerability region of the family of the patriarchal agent is defined as those busses belonging to a collection of voltage instability regions of all agents in the family.

15. The voltage collapse diagnostic method according to claim 13, wherein performing a plurality of single contingencies includes applying to the network a single contingency that has a solution, the method further comprising:

monitoring a change in power output of the sources of reactive reserves of at least one family line of agents.

16. The voltage collapse diagnostic method according to claim 15, further comprising:

calculating the reactive remaining exhaustion factor for each agent for the single contingency; and

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

17. The voltage collapse diagnostic method according to claim 16 wherein the reactive remaining exhaustion factor for each agent is calculated based on either:

18. The voltage collapse diagnostic method according to claim 15, wherein performing the multiple contingency analysis comprises:

applying a combination of two single contingencies identified in step G) that each had a solution in step D), the method further including;

monitoring a change in power output of the sources of reactive reserves of at least one family line of agents.

19. The voltage collapse diagnostic method according to claim 18, further comprising:

determining the reactive remaining exhaustion factor for each agent in the at least one family line of agents for a multiple contingency that has a loadflow solution or where a maximum percentage of the multiple contingency remaining in service is zero; and

ranking each agent according to the reactive remaining exhaustion factor.

20. The voltage collapse diagnostic method according to claim 19, wherein the reactive remaining exhaustion factor for each agent is calculated based on:

21. The voltage collapse diagnostic method according to claim 17, further comprising:

grouping the agents into control regions based on the ranking;

determining an available transfer capability for a control region based on those single contingencies that lack a loadflow solution in step D) or that are components of a respective multiple contingency that lacks a loadflow solution in step H) such that preventative load shedding control in that control region is required.

22. The voltage collapse diagnostic method according to claim 21 wherein determining the available transfer capability for the control region comprises:

identifying each combination of single contingencies that results in no loadflow solution in step H) and has the preventative load shedding control that sheds load in the control region;

determining a remaining amount of reserves for the control region available after simulating a combination that has no loadflow solution in step H) but has a solution when the preventative load shedding control sheds load in the control region; and

defining the remaining amount of reserves for the control region or a maximum amount of load shed in the control region over all single contingencies that lack the loadflow solution in step D) as the incremental transfer capability for the control region.

23. The voltage collapse diagnostic method according to claim 22 wherein determining the remaining amount of reserves for the control region comprises:

applying only one contingency of each combination where the preventative load shedding control is required to obtain the loadflow solution;

determining an additional load that can be applied to the control region after applying the only one contingency before no loadflow solution exists as the remaining amount of reserves; and

taking the minimum of the additional load that can be applied over all single contingencies that are components of each combination as the incremental transfer capability for the control region.

24. The voltage collapse diagnostic method according to claim 23 where an incremental transfer capability for a load pocket belonging to several control regions is the minimum of the additional load that can be applied over all control regions that contain that load pocket.

25. The voltage collapse diagnostic method according to claim 22 where the incremental transfer capability for a load pocket belonging to several control regions is the maximum amount of load shed over all control regions that contain that load pocket.

26. The voltage collapse diagnostic method according to claim 1 wherein the plurality of busses in said network define a region of interest and a buffer zone.

27. The voltage collapse diagnostic method according to claim 26 wherein at least one of the busses in the region of interest is associated with a load.

28. The voltage collapse diagnostic method according to claim 26 wherein at least one bus in the region of interest or in the buffer zone is located within a sub-transmission level or a distribution level of the network.

29. The voltage collapse diagnostic method according to claim 28 wherein the at least one bus is at a voltage level of 34 KV or less.

30. The voltage collapse diagnostic method according to claim 29, further comprising:

identifying the reactive remaining exhaustion factor of each of the agents by monitoring a change in power output of reactive reserves for each of the agents while separately performing each of the plurality of single contingencies in step D).

31. The voltage collapse diagnostic method according to claim 1, further comprising:

ranking the plurality of single contingencies in order of most critical contingencies.

32. The voltage collapse diagnostic method according to claim 31 wherein ranking the plurality of single contingencies is calculated according to:

33. The voltage collapse diagnostic method according to claim 32, further comprising:

ranking each of the agents for at least one of contingencies that have no solution using a boundary case solution with a nonzero percentage outage remaining or contingencies that solve or contingencies that solve with a zero percentage outage remaining according to;

34. The voltage collapse diagnostic method according to claim 30, further comprising:

ranking the agents in order of most critical agents based on the plurality of single contingencies.

35. The voltage collapse diagnostic method according to claim 1 wherein step B) comprises:

i) establishing the equations that define said network;

ii) incrementally applying said load to a first bus within said network;

iii) calculating a power output from each source within said sources of reactive reserves in response to the incrementally applied load;

iv) computing a load curve at said first bus for each incremental load; and

v) identifying a first reactive power minimum at said first bus, or identifying a maximum load terminal point if a first reactive power minimum cannot be identified due to lack of a solution to the equations.

36. The voltage collapse diagnostic method according to claim 35 wherein step B) further comprises:

vi) determining those sources that fully exhaust reserves at the first reactive power minimum or at the maximum load terminal point if the first reactive power minimum cannot be identified due to the lack of a solution to the equations;

performing steps i) through vi) for busses within said network;

wherein step C) further comprises;

clustering the groups of busses as the respective agent such that each agent contains those busses that exhaust the same sources in step vi).

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

establishing the equations that define said network; and

applying said load in an incremental manner whenever the equations fail to solve.

38. The voltage collapse diagnostic method of claim 1 wherein step D) comprises:

simulating each of the plurality of single contingencies as a series of snapshots approximating a dynamic simulation or as a governor or automatic generation control (AGC) loadflow.

39. The voltage collapse diagnostic method of claim 1, wherein at least certain single contingencies in said plurality of single contingencies are applied incrementally.

40. The voltage collapse diagnostic method according to claim 1, further comprising:

iteratively selecting the number of agents N, a maximum percentage X % of reactive reserves of an agent unexhausted after a contingency, and a maximum number of double contingencies that will be simulated based on values for N and X to find a largest number of outages with no loadflow solution;

computing a matrix for discrete equally spaced values of a variable Y %, which is equal to 100-X % and is a minimum percentage of the reactive reserves of the agent exhausted by the contingency on one axis and a number of agents exhausted for the contingency on the other axis, wherein each cell of the matrix contains a number M of single contingencies that satisfy the criteria of having at least the number of agents exhausted for the contingency experience at least Y % of their reactive reserves exhausted, wherein an increase in the number M of single contingencies occurs as the variable Y % is reduced and the number of agents exhausted for the contingency is held fixed;

wherein a number of double contingencies that the number M of single contingencies would produce is M(M−

1)/2

wherein an exponentially declining curve formed by cells of the matrix requires simulating approximately a same number of double contingencies; and

wherein the exponentially declining curve defines options for values of maximum percentage X % and N number of agents.

41. The voltage collapse diagnostic according to claim 40, wherein if all double contingencies formed by the number M of single contingencies for any specific cell are simulated by at least one simulation method, a number of the double contingencies that have no solution for all simulation methods for the cell of the matrix is given as part of the information contained for the cell.

42. The voltage collapse diagnostic according to claim 40, further comprising:

iteratively updating the matrix to provide a number of double contingencies that do not solve for simulation of all double contingencies formed by the number M of single contingencies for cells located along the exponential declining curve that is specified given a maximum number of double contingencies to be simulated.

43. The voltage collapse diagnostic according to claim 40, further comprising:

selecting the values of N number of agents and the variable Y % on a particular exponential declining curve that will change a set of double contingencies to be performed in the multiple contingency analysis of step H) but will keep a total number of double contingencies simulated approximately the same and will not significantly change a percentage of double contingencies simulated that have no loadflow solution.

44. The voltage collapse diagnostic method of claim 1 wherein step H) comprises:

subjecting the network to at least one double contingency, which is defined as applying generally simultaneously, two single contingencies; and

for all double contingencies applied in the subjecting step that have no solution, reapplying each double contingency incrementally.

45. The voltage collapse diagnostic method of claim 44, further comprising:

interpreting all double contingencies that have a solution when reapplied incrementally and a percentage of the equipment of the double contingencies remaining in service is zero as those outages that drive the network to, or close to, at least one of voltage instability, voltage collapse or local blackout.

46. The voltage collapse diagnostic method of claim 38, further comprising:

determining at least one of preventive, corrective, or emergency measures to support power flow on the network based on each single contingency and combinations of two single contingencies performed in the multiple contingency analysis of step H) at a boundary case solution, wherein a boundary case solution defines a percentage of a respective single contingency or combination of two single contingencies remaining in the network that is not equal to zero but is a threshold value such that a very slight increase in the percentage of the respective single contingency or combination of two single contingencies results in no solution for the equations.

47. The voltage collapse diagnostic method of claim 38, further comprising:

determining at least one of preventive, corrective or emergency measures to support power flow on the network based on each single contingency and each double contingency defined by combinations of those single contingencies that have a solution to the equations that define the network when a percentage of a contingency i remaining in the system is zero or at a boundary case solution when the percentage of the contingency i remaining is not equal to zero, in order to reduce severity and proximity to voltage collapse as measured by a contingency measure;

48. The voltage collapse diagnostic method of claim 47, wherein agents j with a factor

49. The voltage collapse diagnostic method of claim 13 wherein a base case blackout region is defined by agents in family lines of an entire family where their reactive reserves zones are completely exhausted in a base solution in the absence of any contingencies and cause a region to be vulnerable to at least one of voltage instability, voltage collapse or local blackout;

wherein a family is defined as all agents in all family lines emanating from a same highest agent.

50. The voltage collapse diagnostic method of claim 46, further comprising:

ranking load bearing agents according to an exhaustion factor that is based on an amount of reactive reserves available to each of the load bearing agents after the respective one of the contingencies;

wherein a predicted control region includes all load bearing agents where the exhaustion factor at the boundary case solution for the respective one of the contingencies is less than a predetermined threshold;

selecting at least some of the load bearing agents for load shedding control and placing them in a control set in an order based on the ranking; and

shedding active and reactive load at all buses bearing load in the control set in the same increasing percentages until consecutive solutions are obtained, active generation response would cause generation decrease on generators via governor loadflow or automatic generation control (AGC) loadflow or would cause generation decrease from a swing bus;

wherein, if the consecutive solutions are obtained, control is chosen near a center of the consecutive solutions or when reactive reserves on generators or control devices in the control set exceed a given percentage of their reactive supply capability;

wherein, if the consecutive solutions are not obtained, then another load bearing agent is added to the control set based on the ranking and the load shedding is repeated in an attempt to obtain the consecutive solutions;

wherein, if the consecutive solutions are not obtained after repeating the load shedding and all agents from the predicted control region are added to the control set, there is no preventive, corrective or emergency load shedding control for the respective one of the contingencies.

51. The voltage collapse diagnostic method of claim 46, further comprising:

ranking load bearing agents according to an exhaustion factor that is based on an amount of reactive reserves available to each of the load bearing agents after the respective one of the contingencies;

wherein a predicted control region includes all load bearing agents where the exhaustion factor at the boundary case solution for the respective one of the contingencies is less than a threshold;

selecting at least some of the load bearing agents for load shedding control based on the ranking and placing them in a control set;

shedding reactive load from buses bearing load in the control set in the same increasing percentages until consecutive solutions are obtained or until reactive reserves on generators or control devices in the control set exceed a given percentage of their reactive supply capability;

if the consecutive solutions are obtained, choosing control near a center of the consecutive solutions; and

if the consecutive solutions are not obtained as the percentage of reactive load shed is increased above a predetermined percentage, adding another load bearing agent to the control set based on the ranking and repeating the load shedding in an attempt to obtain the consecutive solutions;

wherein, if the consecutive solutions are not obtained after repeating the load shedding and all agents from the predicted control region are added to the control set, there is no emergency reactive load shedding control for the respective one of the contingencies.

52. The voltage collapse diagnostic method of claim 46, further comprising:

ranking load bearing agents according to an exhaustion factor that is based on an amount of reactive reserves available to each of the load bearing agents after the respective one of the contingencies, wherein a predicted control region is all load bearing agents where the exhaustion factor at the boundary case solution for the respective one of the contingencies is less than a threshold;

selecting at least some of the load bearing agents for load shedding control based on the ranking and placing them in a control set;

shedding active load from buses bearing load in the control set in the same increasing percentages until consecutive solutions are obtained or until reactive reserves on generators or control devices exceed a given percentage of their reactive supply capability;

if the consecutive solutions are obtained, choosing control near a center of the consecutive solutions; and

if the consecutive solutions are not obtained as the percentage of active load shed is increased above a predetermined percentage, adding another load bearing agent to the control set based on the ranking and repeating the load shedding in an attempt to obtain the consecutive solutions;

wherein, if the consecutive solutions are not obtained after repeating the load shedding and all agents from the predicted control region are added to the control set, there is no preventive or corrective distributed generation control for the respective one of the contingencies.

53. The voltage collapse diagnostic method according to claim 39, further comprising:

determining a presence of a boundary operating region for all single contingencies that have a solution when a percentage of equipment forming a contingency remaining in the system is zero and for all single contingencies that do not have a solution when the percentage of the equipment forming the contingency remaining in the system is non-zero.

54. The voltage collapse diagnostic method of claim 39, further including employing a divide and conquer technique, comprising:

grouping agents into families, wherein a family comprises a plurality of family lines of agents having a common patriarchal agent and wherein a family line includes a child agent supported by a subset of the sources of reactive reserves supporting a parent agent;

wherein the single contingencies are selected based on small effects that exhaust reactive reserves on agents in the same family or based on small effects that exhaust reactive reserves on agents in one or more of the same families.

55. The voltage collapse diagnostic method of claim 54, further comprising:

determining a class of double contingencies that have no loadflow solution when the double contingency is applied in a single step using different loadflow solutions, but that have a loadflow solution when the double contingency is applied incrementally and all equipment associated with the double contingency is removed;

wherein the class of double contingencies place the network in, or close to, a state of at least one of voltage instability, voltage collapse or blackout.

56. A voltage collapse diagnostic and preventive or corrective voltage rescheduling control system, comprising:

A) defining a network of interconnected busses and sources of reactive reserves;

B) defining groups of busses within said network such that when a load is placed on any bus within a first group of said groups of busses, a same at least one source generally completely exhausts its reactive reserves;

C) establishing each group of busses defined in step B) as a respective agent, each agent having a respective set of reactive sources formed by the same at least one source exhausted in step B);

D) performing a plurality of single and double contingencies using equations that define the network;

E) simulating a contingency of the plurality of single and double contingencies by a process that (i) uses different loadflow simulation processes in an effort to obtain a loadflow solution; and

(ii) lacking the loadflow solution in step (i), incrementally removes equipment associated with the contingency and performs a loadflow analysis after each incremental removal until the loadflow analysis shows that no loadflow solution exists, which is a boundary case solution;

F) ranking the agents according to an exhaustion factor for the contingency at the loadflow solution or at a solution based on the boundary case solution, wherein the exhaustion factor is a value representing an amount of reactive power required from the set of reactive sources of the respective agent in response to the contingency;

G) grouping the agents into one or more predicted control regions wherein the exhaustion factor at the loadflow solution or the solution based on the boundary case solution for the contingency is less than a predetermined threshold; and

H) predicting a response of the predicted control region to at least one of preventative voltage rescheduling control, preventative active power rescheduling control or preventative load shedding control for the contingency using the ranking of the agents within the predicted control region.

57. The voltage collapse diagnostic and preventive or corrective voltage rescheduling control system of claim 56, wherein step G) further comprises:

placing the agents and the sources of reactive reserves in the predicted control region based on the ranking established in step F).

58. The voltage collapse diagnostic and preventive or corrective voltage rescheduling control system of claim 56, further comprising:

adding the set of reactive sources associated with each agent of the predicted control region to a control set of sources in an order based on one of active or reactive capacity, loading factor, or reactive reserve losses incurred due to a small change of voltage set point or active generation set point.

59. The voltage collapse diagnostic and preventive or corrective voltage rescheduling control system of claim 58, wherein predicting the response of the predicted control region comprises:

i) increasing the voltage set point on a source within the control set in small percentage increasing steps while concurrently seeking consecutive loadflow solutions to the equations that define the network during the contingency;

ii) if the consecutive loadflow solutions are found in step i), selecting control to be at a point where a reactive reserve level on the sources in the control set exceed a certain percentage of their reactive capability or at an approximate center of the consecutive solutions, which is termed a robust solution;

iii) if the consecutive loadflow solutions are not found in step i), increasing the voltage set point on the source until a total reactive reserve in the control set no longer increases or until source reaches its control limits;

iv) while performing step i), holding at its control limit any one of the sources in the control set that has reached its control limit;

v) continuing steps i) through iv) for each source of the control set until the consecutive loadflow solutions are found or until all the sources in the control set have been used in steps i) through iv); and

vi) in response to step v), if the consecutive loadflow solutions are not found and all the sources in the control set have been used, performing additional control.

60. The voltage collapse diagnostic and preventive or corrective voltage rescheduling control system of claim 59, further comprising:

if the consecutive loadflow solutions are not found using all sources of all agents in the predicted control region, placing an additional agent into the predicted control region and repeating steps i) through vi) using the using the sources of the additional agent in the control set.

61. The voltage collapse diagnostic and preventive or corrective voltage rescheduling control system of claim 59 wherein the sources of reactive reserves include generators and further comprising:

implementing preventative control by modifying the voltage set point on at least one of the sources of the control set or by adding a shunt capacitor close to a generator of the control set that experiences an increase in its reactive reserves for the robust solution if at least one of a voltage decreases sufficiently in the control region, if the contingency is a single contingency and it occurs or the system is known to be vulnerable to voltage collapse for the single contingency, or if the contingency is a double contingency and a first contingency component of the double contingency occurs.

62. The voltage collapse diagnostic and preventive or corrective voltage rescheduling control system of claim 58 wherein the sources in the control set comprise generators and wherein predicting the response of the predicted control region includes:

increasing a voltage set point on all of the generators in the control set simultaneously in small percentage steps while concurrently seeking consecutive loadflow solutions to the equations that define the network during the contingency until any given generator reaches it voltage rating limit, thereafter, holding any given generator that has reached its voltage rating limit at its voltage rating limit while simultaneously increasing the voltage set point on any remaining generators in the control set and concurrently seeking the consecutive loadflow solutions to the equations that define the network during the contingency; and

if the consecutive loadflow solutions are found, ending the step of increasing the voltage set point and selecting control to be at a point where a reactive reserve level on the generators in the control set exceed a certain percentage of their reactive capability or at an approximate center of the consecutive loadflow solutions.

63. The voltage collapse diagnostic and preventive or corrective voltage rescheduling control system of claim 56 wherein the sources of reactive reserves for the predicted control region comprise a plurality of generators belonging to the set of reactive sources for each agent of the predicted control region and wherein predicting the response of the predictive control region comprises:

progressively decreasing a voltage set point on generators of the predicted control region that have high loading factors and progressively increasing the voltage set point on generators of the predicted control region with small loading factors wherein the voltage set point of a respective generator is increased no higher than a voltage rating of the respective generator and wherein progressively decreasing the voltage set point on respective generator is stopped when a total reactive generation of the plurality of generators or on those of the plurality of generators with the largest reactive generation levels or loading factors no longer reduced;

concurrently seeking consecutive loadflow solutions to the equations that define the network during the contingency while progressively decreasing and progressively increasing the voltage set points; and

wherein there is no preventive and corrective voltage rescheduling control using a combination of voltage increase and voltage decrease if no consecutive loadflow solutions are found after all generators of all agents in the predicted control region have been processed through either progressively increasing or progressively decreasing its voltage set point.

64. The voltage collapse diagnostic and preventive or corrective voltage rescheduling control system of claim 56 wherein the sources of reactive reserves for the predicted control region comprise a plurality of generators belonging to the set of reactive sources for each agent of the predicted control region and wherein predicting the response of the predictive control region comprises:

i) progressively decreasing an active power generation on generators of the predicted control region that have high loading factors and progressively increasing the active power generation on generators of the predicted control region with small loading factors while voltage and active power generation limits on each generator is maintained and while a total of reactive reserves on the plurality of generators in the control set is increased;

ii) concurrently seeking consecutive loadflow solutions to the equations that define the network during the contingency while progressively decreasing and progressively increasing the active power generation;

iii) adding additional generators of an additional agent to the predicted control region based on the exhaustion factor of the additional agent if no consecutive of loadflow solutions are found or the total of reactive reserves does not increase and repeating steps i) and ii); and

iv) performing steps i) through iii) until at least one of (a) consecutive loadflow solutions are found or (b) no consecutive loadflow solutions are found and reactive reserve levels on generators in the predicted control region exceed a percentage of their reactive supply capability or iii) no consecutive loadflow solutions are found and all the agents have been added to the predicted control region; and

wherein

if in step iv), no consecutive loadflow solutions are found and reactive reserve levels on generators in the predicted control region exceed the percentage of their reactive supply capability or no consecutive loadflow solutions are found and all the agents have been added to the predicted control region, there is no preventive and corrective voltage and active rescheduling control for the contingency.

65. The voltage collapse diagnostic and preventive or corrective voltage rescheduling control system of claim 64 further comprising:

applying preventive load shedding if there is no preventive voltage and active rescheduling control for the contingency.

66. The voltage collapse diagnostic and preventive or corrective voltage rescheduling control system of claim 56 wherein the sources of reactive reserves for the predicted control region comprises a plurality of generators belonging to the set of reactive sources for each agent of the predicted control region and wherein predicting the response of the predictive control region comprises:

decreasing voltage and power generation on a first set of generators of the plurality of generators and increasing voltage and power generation on a second set of generators of the plurality of generators while concurrently seeking consecutive loadflow solutions to the equations that define the network during the contingency, wherein if consecutive loadflow solutions are not obtained, then other measures are taken.

67. The voltage collapse diagnostic and preventive or corrective voltage rescheduling control system according to claim 56, further comprising:

determining at least one of preventive, corrective or emergency measures to support power flow on the network by performing steps E) through H) for a plurality of contingencies lacking a loadflow solution.

68. The voltage collapse diagnostic and preventive or corrective voltage rescheduling control system according to claim 67, further comprising:

executing the at least one of preventive, corrective or emergency measures.

69. The voltage collapse diagnostic and preventive or corrective voltage rescheduling control system according to claim 68 wherein the preventive measures include at least one of shedding load, adding new generation within unit commitment, constructing new generation, rescheduling active power on at least certain of the sources of reactive reserves or rescheduling voltage set points on at least certain of the sources of reactive reserves.

70. The voltage collapse diagnostic and preventive and corrective control of active rescheduling comprising the steps of:

A) ranking agents according to an exhaustion factor for a boundary case solution for that outage;

B) defining a predicted control region which includes all agents that experience an exhaustion factor less than a predetermined threshold;

C) selecting associated generators defined in step B) belonging to the predicted control region and placing said generators in the control set for active rescheduling control based on a generator or control device ranking of an exhaustion factor;

D) adding the generators associated with any agent selected to be added to the control region to the generators or control devices in the control set simultaneously;

wherein the generators with the largest exhaustion factor in the control set will generate less power by a participation factor proportional to the variable such as reactive and active loading factor or reactive losses incurred for a slight increase in active generation or voltage setpoint and the generators with the smallest variables will increase power using a participation factor that is inversely proportional to this variable such that the sum of the amount of power increased and decreased on generators in the control set is always zero or equal to the change in active losses incurred by the control change, wherein transfer of power is produced within the control set of generators that is progressively increased;

wherein the active power setpoint on any generator is changed as part of the transfer level increase until reactive reserves on the generators in the control set no longer increase or until they reach the maximum or minimum active power capability limit on the generator and then they are held at that maximum or minimum active power capability limit;

wherein the transfer of power within the set generators in the control set using the participation factors is progressively increased until reactive generation levels on generators in the control set or control region exceed a certain percentage of their reactive supply capability by increase in transfer or until a consecutive set of solutions is obtained, wherein no solution is found then another generator or control device is added to the control set based on the ranking of generators and control devices in the predicted control region are added to the control set, wherein process of increasing transfer within the control set of generators in an attempt to find consecutive loadflow solutions and increasing reactive reserves on generators or control devices in the control set or control region by increasing transfer levels on generators in the control set and if unsuccessful then adding an additional generator or control device to the control set is continued until there are no more generators or control devices in the predicted control region, wherein consecutive solutions are found, the control is selected to be nearer the centered of the consecutive set of solutions or where the reactive reserves on the generators and control devices exceed a certain percentage of their reactive supply capability, wherein no control is found after all agents in the predicted control region are placed in the control region, there is no preventive and corrective active rescheduling control for this contingency, wherein the Preventive Control could be implemented by modifying the active power generation setpoints if the first of a double contingency occurs with no solution, or if the system is known to be vulnerable to voltage collapse for this single contingency before it actually occurs on the system.

71. A method of posturing control for a system including a base case blackout region, comprising:

defining a control region of agents and a control set of reactive sources by;

A) defining a network of interconnected busses and sources of reactive reserves;

B) defining groups of busses within said network such that when a load is placed on any bus within a first group of said groups of busses, a same at least one source generally completely exhausts its reactive reserves;

C) establishing each group of busses defined in step B) as a respective agent, each agent having a respective set of reactive sources formed by the same at least one source exhausted in step B);

D) simulating a plurality of single and double contingencies using equations that define the network by a process that (i) uses different loadflow simulation processes in an effort to obtain a loadflow solution; and

(ii) lacking the loadflow solution in step (i), attempts to obtain a solution by incrementally removing equipment associated with the contingency until the loadflow analysis shows that no loadflow solution exists, which is a boundary case solution;

E) determining a blackout region for each contingency of the plurality of single and double contingencies where agents have reactive resources that are completely exhausted by the contingency; and

wherein the control region of agents is formed by combining agents in the blackout region for each contingency with agents in the base case blackout region where the base case blackout region comprises those agents having no reactive reserves in a base case loadflow solution; and

wherein the control set of reactive sources are those sets of reactive sources of each agent in the control region of agents;

performing at least one of the following steps for the control region of agents;

adding generators to the control set in order to add reactive reserves to the control region;

adding switchable shunt capacitors to the control set in the control region to a location where there is an existing generator;

performing preventative voltage and reactive rescheduling by increasing a respective voltage set point of certain reactive sources of the control set and by decreasing a respective voltage set point of other reactive sources of the control set to add reactive reserves to the control region;

performing preventative active rescheduling by increasing a respective active power generation level of certain reactive sources of the control set and by decreasing a respective active power generation level of other reactive sources of the control set to add reactive reserves to the control region;

or

if the network experiences a contingency that makes blackout imminent, performing preventative or emergency load shedding to add reactive reserves to the control region.

72. A method of posturing control for a set of equipment outages that have no solution, comprising:

defining a network of interconnected busses and sources of reactive reserves;

defining groups of busses within said network such that when a load is placed on any bus within a first group of said groups of busses, a same at least one source generally completely exhausts its reactive reserves, each of the groups of busses established as a respective agent;

performing a plurality of single and double contingencies using equations that define the network;

defining the set of equipment outages as those contingencies of the plurality of single and double contingencies for which no loadflow solution results when performing the contingency;

finding at least one of a preventative voltage rescheduling control or preventative active rescheduling control for each contingency for which no loadflow solution results that obtains a robust solution by;

for each contingency for which no loadflow solution results, performing at least one of i) increasing voltage set points of certain sources of at least one agent and decreasing or holding constant voltage set points of other sources of the at least one agent or ii) increasing active power generation of certain sources of at least one agent and decreasing active power generation of other sources of the at least one agent until a loadflow solution results for the contingency wherein the increasing and the decreasing occurs in an order based on the effect of the contingency on the at least one agent; and

defining a control region for the contingency as the at least one agent whose sources are increased or decreased;

finding those of the contingencies with identical control regions so as to form a single control region; and

utilizing a coordinated voltage control for finding a posturing control for all contingencies for the single control region by utilizing different control sets of sources and different levels of voltage control to obtain solutions for all contingencies for the single control region.

73. The method of claim 72, further comprising:

utilizing a coordinated active power control for finding a posturing control for all contingencies for the single control region by utilizing different control sets of sources and different levels of active power control to obtain solutions for all contingencies for the single control region.

74. The method of claim 72 wherein each agent is defined to include a set of reactive sources including the same at least one source, the method further comprising:

arranging the agents in a hierarchical structure based on the respective set of reactive sources for each agent such that an agent lower in the hierarchical structure includes a subset of the reactive sources of the set of reactive sources for an agent higher in the hierarchical structure, such a relationship defining a family line wherein a family includes at least two family lines of agents with a same patriarchal parent; and

adding an agent in families and family lines belonging to the an agent in the single control region that is not currently in the single control region but exhausts a significant percentage of its reactive reserves and retrying coordinated voltage control if an effective postured control could not be obtained without the additional agent.

75. The method of claim 72, further comprising:

locating groups of control regions that have postured control once postured control has been found for each single control region.

76. The method of claim 72, further comprising:

selecting a prototype postured control for a largest control region in a group of control regions.

77. The method of claim 72, further comprising:

utilizing a coordinated voltage and active power control that attempts to find a posturing control for all contingencies for all control regions in a group of control regions by utilizing different control sets of sources and different levels of voltage and active power control change to obtain solutions for all contingencies for all control regions.

78. The method of claim 72, further comprising:

implementing and coordinating postured controls for different groups of single control regions.

79. The method of claim 73 wherein, if no posturing control is found for all contingencies for the single control region, applying preventive control individually to those contingencies for which the posturing control is not effective in obtaining robust solutions.

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

applying a voltage collapse diagnostic 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 by;

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

applying a voltage collapse diagnostic 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 by;

82. A method for determining an available transfer capability, comprising:

determining an amount of power that is available for transfer into or out of a load pocket where the set of importing and the set of exporting generators and their participation factors are design parameters;

wherein the determining step is a function of firm and non-firm transfer into the load pocket and a Transmission Reliability Margin (TRM) and a Capacity Benefit Margin (CBM) for the load pocket wherein;

TTC =ITC +net power flow into the load pocket;

NATC =TTC −

TRM −

NRES;

RATC =TTC −

a TRM −

NRES −

RRES; and

a<

1;

wherein

TTC is a Total Transfer Capability for the load pocket;

ITC is an Incremental Transfer Capability for the load pocket;

NRES is the non-recallable or firm transmission reservation for the load Pocket;

RRES is the recallable or non firm reservation for the load pocket;

NATC is the Non Recallable Available Transfer Capability; and

RATC is the Recallable Available Transfer Capability.