Dynamic method for preventing voltage collapse in electrical power systems

• US 5,796,628 A
• Filed: 04/20/1995
• Issued: 08/18/1998
• Est. Priority Date: 04/20/1995
• Status: Expired due to Term

• Current Assignee: Cornell Research Foundation Incorporated (Cornell University)
• Original Assignee: Cornell Research Foundation Incorporated (Cornell University)
• Inventors: Chiang, Hsiao-Dong, Wang, Cheng-Shan
• Primary Examiner(s): Voeltz, Emanuel Todd
• Assistant Examiner(s): COLE, TONY MITCHELL
• Application Number:
  US08/425,555
• Time in Patent Office: 1,216 Days
• Field of Search: 364/492, 364/493, 364/494, 364/495, 307/31, 307/33, 307/35, 307/38, 307/39, 307/85, 307/29, 395/907, 395/915, 323/241, 323/234
• US Class Current: 700/295
• 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 3/144 Demand-response operation of the power transmission or distribution network
• CPC Class Codes: Y02B 70/3225 Demand response systems, e.g. load shedding, peak shaving
• CPC Class Codes: Y04S 20/222 Demand response systems, e.g. load shedding, peak shaving
• CPC Class Codes: Y10S 706/915 Power plant

Abstract

Given the current operating condition of a power-generating system (obtained from real-time data), the near-term (e.g., after 25 min.) load demand at each bus (obtained from short-term load forecast) and the generation dispatch (based on economic dispatch), a load margin measure (MW and/or MVAR) is determined in order to assess the system'"'"'s ability to withstand the forecasted load and generation variations. The invention has a method to predict near-term (e.g., after 25 min.) system voltage profiles. The proposed look-ahead measure and/or the system voltage profiles are then applied to contingency selections for the near-term power system, in terms of load margins to collapse and bus voltage magnitudes. The proposed load margin measure and the voltage profiles are based on the power flow technique and the saddle-node bifurcation theory.

Claims

1. A dynamic method of preventing voltage collapse in a power-generating system, comprising the steps of:

a) measuring the load demands with respect to time in a power-generating system having a power-generating grid in order to provide look-ahead load demands;

b) calculating a performance index directly correlated to the look-ahead load demands obtained in step (a);

c) utilizing the performance index to identify weak areas in the power-generating system;

d) generating voltage profiles, which are dynamic and revisable over time, for said power-generating system in order to properly maintain said power-generating system; and

e) shedding load in those portions of the power-generating grid of said power-generating system that are identified as weak areas, in order to prevent voltage collapse in the power-generating system in accordance with said dynamic voltage profiles.

2. The dynamic method of preventing voltage collapse in a power-generating system in accordance with claim 1, wherein reactive power is simultaneously varied on at least two of a plurality of buses in a grid of said power-generating system.

3. A dynamic method of preventing voltage collapse in a power-generating system, comprising the steps of:

a) measuring the load demands with respect to time in a power-generating system having a power-generating grid in order to provide look-ahead load demands;

b) calculating a performance index directly correlated to the look-ahead load demands obtained in step (a);

c) utilizing the performance index to identify weak areas in the power-generating system;

d) generating voltage profiles, which are dynamic and revisable over time, for said power-generating system in order to properly maintain said power-generating system; and

e) adding additional power-generating capacity in those portions of the power-generating grid of said power-generating system that are identified as weak areas, in order to prevent voltage collapse in the power-generating system in accordance with said dynamic voltage profiles.

4. The dynamic method of preventing voltage collapse in a power-generating system in accordance with claim 3, wherein reactive power is simultaneously varied on at least two of a plurality of buses in a grid of said power-generating system.

5. A dynamic method of preventing voltage collapse in a power-generating system, comprising the steps of:

a) generating a look-ahead load margin ranking;

b) generating a look-ahead voltage ranking;

c) combining said look-ahead load margin ranking with said look-ahead voltage ranking to provide an energy management scheme for a power-generating system in which voltage collapse will be prevented in said power-generating system.

6. A dynamic method of preventing voltage collapse in a power-generating system, comprising the steps of:

a) forecasting near-term power flows utilizing a saddle-node theory for a power-generating system having a power-generating grid;

b) determining from forecasts in step (a) load margin value indices that provide an assessment of load demand that said generating system can withstand before saddle-node voltage collapse; and

c) maintaining power-generating capacity of said power-generating system, by preventing voltage collapse of said power-generating system based on said load demand assessment in step (b).

7. The dynamic method of preventing voltage collapse in a power-generating system in accordance with claim 6 further comprising the step of:

d) applying the load margin indices obtained in step (b) to obtain system voltage profiles for said power-generating system, said voltage profiles can be utilized for maintaining power-generating capacity of said power-generating system.

8. The dynamic method of preventing voltage collapse in a power-generating system in accordance with claim 6, wherein step (c) further comprises the step of:

d) adding power-generating capacity to a grid of said power-generating system.

9. The dynamic method of preventing voltage collapse in a power-generating system in accordance with claim 6, wherein step (c) further comprises the step of:

d) shedding load to certain portions of a grid of said power-generating system.