Detecting electromechanical oscillations in power systems

• US 20050187726A1
• Filed: 06/18/2004
• Published: 08/25/2005
• Est. Priority Date: 06/21/2003
• Status: Active Grant

• Current Assignee: Hitachi Energy Limited
• Original Assignee: ABB Research Ltd. (ABB Ltd.)
• Inventors: Larsson, Mats, Korba, Petr, Rehtanz, Christian
• Granted Patent: US 7,149,637 B2
• Time in Patent Office: Days
• 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 parameters (frequency ƒ and damping ξ) is based on a linear time-varying model. The parameters of the linear model are on-line adapted by means of Kalman filtering techniques to approximate the measured signal y (representing the behaviour of the power system) optimally in the sense of 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. As opposed to the collection of data over a time window and then performing the parameter identification at once, any change in the system can thus be detected much faster.

Claims

1. Method of detecting electromechanical oscillations in power systems, wherein

a) a system quantity of the power system is repeatedly measured and a series of measured values of the system quantity is generated,

b) parameters of a parametric model are estimated from said series,

c) information about an electromechanical oscillation mode of the power system are deduced from the parameters, wherein

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

2. The method according to claim 1, wherein the parametric model 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 parameters of the linear autoregressive model.

4. The method according to claim 3, wherein a covariance matrix K(k) 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 discrete-time linear autoregressive model to a continuous-time model.

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

7. The method according to claim 6, wherein the critical information is used in order to optimize the rate of utilization of the power transmission capacity.

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

9. An electric power transmission system comprising means for carrying out the method for detecting electromechanical oscillations according to claim 1.

10. A computer program for detecting electromechanical oscillations in electric power transmission systems which is loadable into an internal memory of a digital computer, comprising computer program code means to make, when said program is loaded in said internal memory, the computer execute the method for detecting electromechanical oscillations according to claim 1.