VERIFYING AN ACCURACY OF A STATE ESTIMATION

• US 20080262758A1
• Filed: 05/06/2008
• Published: 10/23/2008
• Est. Priority Date: 11/08/2005
• Status: Active Grant

• Current Assignee: Hitachi Energy Limited (Hitachi, Ltd.)
• Original Assignee: ABB Technology AG (ABB Limited)
• Inventors: Zima, Marek, Bertsch, Joachim, REHTANZ, Christian, Suranyi, Andreas
• Granted Patent: US 8,190,379 B2
• Time in Patent Office: Days
• US Class Current: 702/57
• CPC Class Codes: H02J 3/242 using phasor measuring units [PMU]
• CPC Class Codes: Y02E 40/70 Smart grids as climate change mitigation technology in the energy generation sector
• CPC Class Codes: Y02E 60/00 Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
• CPC Class Codes: Y04S 10/00 Systems supporting electrical power generation, transmission or distribution
• CPC Class Codes: Y04S 10/22 Flexible AC transmission systems [FACTS] or power factor or reactive power compensating or correcting units

Abstract

The present disclosure is concerned with the reduction of an operational security margin of a power system without jeopardizing the safety of the power system or incurring heavy investments. According to the disclosure, a check for basic accuracy or correctness of a conventional State Estimation (SE) procedure allows to increase a level of confidence in the results of the procedure. To this end, an accuracy of the estimated states is verified by comparing the latter with the results (y, y′) of independent phasor measurements performed at selected locations of the power system. Unless a discrepancy is reported by this comparison, the results of the SE can be assumed to be sufficiently accurate, and any conservative or additional security margin intended to compensate for SE uncertainty can be relaxed. Hence, established trustworthiness in the estimated states allows increasing the transmitted power where the estimated states do indicate such a possibility, i.e. in particular in fringe areas and/or transmission corridors between countries, and especially under stressed network conditions.

Claims

1. A method of verifying an accuracy of a State Estimation (SE) procedure estimating a number of states (x) of an electric power system based on a redundant set of measurements (z) and corresponding errors (v), wherein the states (x) correspond to system quantities at a number of locations of the system, the method comprising:

measuring a phasor value (y, y′

) of a system quantity at a location of the system; and

comparing the measured phasor value (y, y′

) with the estimated state (x) corresponding to the respective system quantity at the location of the phasor measurement.

2. The method according to claim 1, comprising:

measuring two phasor values (y, y′

) at two locations of the system and calculating a value of a dependent system quantity (Δ

φ

) from the two phasor values; and

comparing said value of the dependent system quantity (Δ

φ

) with the respective value of the dependent system quantity (Δ

φ

) calculated from the estimated states corresponding to the respective system quantities at the two locations.

3. The method according to claim 1, comprising:

defining a discrepancy threshold between the measured phasor value or phasor value difference and the estimated state or state difference; and

generating an alarm if the discrepancy threshold is exceeded.

4. The method according to claim 3, comprising:

reducing a security margin for operating a transmission line of the power system if the discrepancy measure is not exceeded.

6. The method according to claim 2, comprising:

defining a discrepancy threshold between the measured phasor value or phasor value difference and the estimated state or state difference; and

generating an alarm if the discrepancy threshold is exceeded.

5. An arrangement for verifying an accuracy of a State Estimation (SE) procedure estimating a number of states (x) of an electric power system based on a redundant set of measurements (z) and corresponding errors (v), wherein the states (x) correspond to system quantities at a number of locations of the system, the arrangement comprising:

a Phasor Measurement Unit (PMU) for measuring a phasor value (y, y′

) of a system quantity at a location of the system; and

a control centre for comparing the measured phasor value (y, y′

) with the estimated state (x) corresponding to the respective system quantity at the location of the Phasor Measurement Unit (PMU).

7. An electric power system configured to verify an accuracy of a state estimation procedure estimating a number of states (x) of the electric power system based on a redundant set of measurements (z) and corresponding errors (v), wherein the states (x) correspond to system quantities at a number of locations of the system, the electric power system comprising:

means to measure a phasor value (y, y′

) of a system quantity at a location of the system; and

means to compare the measured phasor value (y, y′

) with the estimated state (x) corresponding to the respective system quantity at the location of the phasor measurement.

8. The system according to claim 7, wherein:

two phasor values (y, y′

) are measured at two locations of the system and calculating a value of a dependent system quantity (Δ

φ

) from the two phasor values; and

said value of the dependent system quantity (Δ

φ

) is compared with the respective value of the dependent system quantity (Δ

φ

) calculated from the estimated states corresponding to the respective system quantities at the two locations.

9. The system according to claim 7, wherein:

a discrepancy threshold between the measured phasor value or phasor value difference and the estimated state or state difference is defined; and

an alarm is generated if the discrepancy threshold is exceeded.

10. The system according to claim 9, wherein:

a security margin for operating a transmission line of the power system is reduced if the discrepancy measure is not exceeded.