Detecting electromechanical oscillations in power systems

• US 7,149,637 B2
• Filed: 06/18/2004
• Issued: 12/12/2006
• Est. Priority Date: 06/21/2003
• Status: Active Grant

• Current Assignee: Hitachi Energy Limited
• Original Assignee: ABB Research Ltd. (ABB Ltd.)
• Inventors: Korba, Petr, Rehtanz, Christian, Larsson, Mats
• Primary Examiner(s): WACHSMAN, HAL D
• Application Number:
  US10/871,685
• Publication Number:
  US 20050187726A1
• Time in Patent Office: 907 Days
• Field of Search: 702 57- 60, 702/64, 702/65, 702/66, 702/69, 702/67, 702/75, 702/76, 702/115, 702/124, 702/182, 702/183, 702/185, 702/187, 702/189, 702/190, 702/196, 324/500, 324/522, 324/76.39, 324/142, 324/771, 703/18, 703/13, 700/293, 700/294
• US Class Current: 702/60
• 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 detection of electromechanical oscillations in power systems and the estimation of their frequency and damping parameters are based on a linear time-varying model. The parameters of the linear model are on-line adapted by means of Kalman filtering techniques to optimally approximate the measured signal representing the behavior of the power system based on a quadratic criterion. The estimated model parameters are then the basis for the calculation of parameters of the oscillations. Adaptive algorithms are based on a recursive calculation of the estimated parameter vector for each time-step based on the new value of the measured signal and the old values of the estimated parameters.

Claims

1. Method of detecting electromechanical oscillations in a power system, comprising

a) measuring repeatedly a system quantity of the power system and generating a series of measured values of the system quantity,

b) estimating model parameters of a discrete-time model of the power system from said series,

c) deducing frequency and damping of an electromechanical oscillation mode of the power system from the model parameters, wherein the method comprises

d) updating said model parameters every time a new value of the system quantity is measured.

2. The method according to claim 1, wherein the discrete-time model of the power system is a linear autoregressive model of finite order.

3. The method according to claim 2, wherein an adaptive Kalman Filter is used to estimate the model parameters of the linear autoregressive model.

4. The method according to claim 3, wherein a covariance matrix of the adaptive Kalman Filter is symmetrical.

5. The method according to claim 2, wherein a bilinear or Tustin transformation is used to convert the linear autoregressive model of finite order to a continuous-time model.

6. The method according to claim 1, wherein frequency and damping of the oscillation mode with lowest damping is updated regularly and displayed to an operator.

7. The method according to claim 1, wherein the frequency and damping of the oscillations are deduced from the model parameters less frequently than the model parameters updates.

8. The method according to claim 1, wherein the system quantity is a time stamped phasor signal provided by one phasor measurement unit.

9. An electric power transmission system including means for detecting electromechanical oscillations of the power system, comprising:

a) means for repeatedly measuring a system quantity of the power system and generating a series of measured values of the system quantity,

b) means for estimating, from said series, model parameters of a discrete-time model of the power system,

c) means for deducing, from said model parameters, frequency and damping of an electromechanical oscillation mode of the power system, the means for detecting electromechanical oscillations of the power system comprising

d) means for updating said model parameters every time a new value of the system quantity is measured.

10. A computer-readable medium for detecting electromechanical oscillations in electric power transmission systems, the computer-readable medium containing programming instructions which are loadable into an internal memory of a digital computer, the programming instructions comprising computer program code means to make the computer execute the steps of:

a) measuring repeatedly a system quantity of the power system and generating a series of measured values of the system quantity;

b) estimating model parameters of a discrete-time model of the power system from said series;

c) deducing frequency and damping of an electromechanical oscillation mode of the power system from the model parameters; and

d) updating said model Parameters every time a new value of the system quantity is measured.