Method for voltage stability analysis of power systems

• US 5,745,368 A
• Filed: 03/29/1996
• Issued: 04/28/1998
• Est. Priority Date: 03/29/1996
• Status: Expired due to Term

• Current Assignee: Siemens Industry Incorporated (Siemens AG)
• Original Assignee: Siemens Energy & Automation Incorporated (Siemens AG)
• Inventors: Tong, Jianzhong, Ejebe, Gabriel C.
• Primary Examiner(s): Ramirez, Ellis B.
• Assistant Examiner(s): PEESO, THOMAS R
• Application Number:
  US08/625,053
• Time in Patent Office: 760 Days
• Field of Search: 364/492, 364/483, 307/102, 307/132 EA, 361/59, 361/111, 324/602, 324/609, 324/618
• US Class Current: 702/164
• CPC Class Codes: H02J 3/00 Circuit arrangements for ac mains or ac distribution networks

Abstract

A method for Voltage Stability Analysis of a bulk power supply system is taught. Briefly stated, a computationally efficient method is disclosed which is appropriate for low and high voltage applications as well as differing types of loads and load changes, i.e. reactive or otherwise, and which is usable with a multitude of different bulk power supply system systems. More particularly, a nose point of a curve for which MVAr, MW or MVA distances to voltage are calculated, using a generalized curve fit in order to compute an equivalent or surrogate nose point. This is done by approximating a stable branch and creating a voltage versus power curve, determining a plurality of stable equilibrium points on the curve, using the plurality of determined stable equilibrium points to create and fit an approximate stable branch, calculating an approximate voltage collapse point and thereafter a voltage collapse index.

Claims

1. A method for Voltage Stability Analysis of a bulk power supply system, comprising the following steps:

A. selecting at least two contingencies of a plurality of contingencies of the bulk power supply system;

B. screening and ranking the contingencies based on a predetermined ranking algorithm and generating a voltage collapse index;

C. approximating a stable branch of the bulk power supply system based on the screened and ranked contingencies of step B;

D. creating a voltage versus power curve by determining a plurality of stable equilibrium points on the curve;

E. using the plurality of determined stable equilibrium points to create and fit the approximate stable branch of step C;

F. calculating an approximate voltage collapse point for use in conjunction with the voltage collapse index.

2. A method according to claim 1 comprising the additional steps of:

E. Using a generalized curve fit to compute a nose point for which MVAr, MW or MVA distances to voltage may be calculated; and

F. calculating the MVAr, MW or MVA distances to voltage based on the generalized curve fit.

3. A method according to claim 1 comprising the additional steps of:

E. using a generalized curve fit to compute a nose point for which MVAr and MVA distances to voltage may be calculated; and

F. calculating the MVAr and MVA distances to voltage based on the generalized curve fit.

4. A method according to claim 1, wherein said plurality of stable equilibrium points is three stable equilibrium points.

5. A method for Voltage Stability Analysis of a bulk power supply system comprising the following steps, according to the following defined relationship:

A. selecting at least two contingencies of a plurality of contingencies of the bulk power supply system;

B. screening and ranking the contingencies based on a predetermined ranking algorithm;

C. calculating a stable branch of the bulk power supply system based on the screened and ranked contingencies of step B according to;

space="preserve" listing-type="equation">λ

=a.sub.n x.sup.n + . . . +a.sub.1 x+

D. creating a voltage versus power curve for active power and reactive power by determining a plurality of stable equilibrium points on the curve according to;

space="preserve" listing-type="equation">f(x,λ

)=F(x)+λ

b=0

D. using the plurality of determined stable equilibrium points to create and fit an approximate stable branch according to;

space="preserve" listing-type="equation">λ

.sub.I =a.sub.1i x.sub.i.sup.2 +a.sub.2i x.sub.i +a.sub.3.

E. calculating an approximate voltage collapse point according to;

##EQU9## F. creating a voltage collapse index λ

* according to;

where ##EQU10## and n_c is a number of buses where load is changed, the number of busses being greater than one.

6. A method according to claim 5, wherein said plurality of stable equilibrium points is three stable equilibrium points.