Damping electromechanical oscillations in power systems

• US 20080177425A1
• Filed: 12/07/2007
• Published: 07/24/2008
• Est. Priority Date: 06/24/2005
• Status: Active Grant

• Current Assignee: ABB Power Grids Switzerland AG (ABB Limited)
• Original Assignee: ABB Research Ltd. (ABB Ltd.)
• Inventors: Larsson, Mats, Korba, Petr, Oudalov, Alexandre, Lindberg, Johan A., Thorburn, Stefan G.
• Granted Patent: US 8,019,484 B2
• Time in Patent Office: Days
• US Class Current: 700/297
• CPC Class Codes: H02J 3/06 Controlling transfer of power between connected networks; Controlling sharing of load between connected networks
• CPC Class Codes: H02J 3/1814 wherein al least one reactive element is actively controlled by a bridge converter, e.g. unified power flow controllers [UPFC]
• CPC Class Codes: H02J 3/242 using phasor measuring units [PMU]
• CPC Class Codes: Y02E 40/10 Flexible AC transmission systems [FACTS]
• 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 combined voltage or power flow control and damping of electromechanical oscillations in an electric power system by Flexible AC Transmission System (FACTS) devices or High Voltage DC (HVDC) transmission devices. To this end, information about a state or operating point of the power system is generated from suitable second system signals (y₂) and a control parameter (cp) of a FACTS controller is derived therefrom. The control parameter and a first system signal (y₁) are used in the calculation of a control command (u) defining the settings of the FACTS device. Following a change in the state of the power system such as a change in the topology of a transmission network, poorly damped or even unstable oscillations are avoided by appropriate re-tuning of the control parameter of the damping or stabilizing equipment.

Claims

1. A method of controlling power flow in a power system, comprising

measuring a first system signal (y₁),

calculating a control command (u) based on the first system signal (y₁) and a power flow control parameter (r₁),

applying the control command (u) to a power electronic semiconductor based Power Flow Control Device (PFD) for controlling power flow in the power system,

repeatedly measuring a second system signal y₂),

adaptively determining a power oscillation control parameter (cp) based on the second system signal (y₂),

calculating the control command (u) based on the power oscillation control parameter (cp), and

applying the control command (u) to the PFD (20) for damping electromechanical oscillations in the power system.

2. The method according to claim 1, wherein the calculation of the control command (u) is based on a difference between the first system signal (y₁) and a set-point (r₁) of the PFD as the power flow control parameter, wherein the method comprises

adaptively determining the power oscillation control parameter (cp) at least at a frequency characteristic of changes of an operating point of the power system.

3. The method according to claim 1, comprising:

repeatedly measuring, by a phasor measurement unit, a time stamped phasor signal as the second system signal (y₂), and

adaptively determining the power oscillation control parameter (cp) whenever a phasor measurement is made.

4. The method according to claim 1, wherein the determination of the power oscillation control parameter (cp) involves determining a model parameter (mp) of a model of the power system from the second system signal (y₂).

5. The method according to claim 4, wherein the determination of the power oscillation control parameter (cp) involves determining oscillation parameters (ξ

, ν

) of a dominant power oscillation mode from the model parameter (mp).

6. The method according to claim 4, wherein the determination of the model parameter (mp) from the second system signal (y₂) comprises generating a series of measured values (y₂, y₂′

, . . . ) of the second system signal (y₂), estimating model parameters (mp) of a parametric model from said series, and updating said parameters (mp) every time a new value of the second system signal (y₂) is measured.

12. The method according to claim 2, comprising

repeatedly measuring, by a phasor measurement unit, a time stamped phasor signal as the second system signal (y2), and

adaptively determining the power oscillation control parameter (cp) whenever a phasor measurement is made.

13. The method according to claim 3, wherein the determination of the power oscillation control parameter (cp) involves determining a model parameter (mp) of a model of the power system (2) from the second system signal (y2).

7. A control arrangement comprising:

a controller for controlling power flow and damping electromechanical oscillations in a power system by applying a control command (u) to a power electronic semiconductor based Power Flow Control Device (PFD), wherein the control command (u) is calculated based on a first system signal (y₁) and a power flow control parameter (r₁); and

a parameter adapter for adapting a power oscillation control parameter (cp) based on a second system signal (y₂), wherein the controller comprises a power oscillation damper for calculating the control command (u) based on the control parameter (cp).

8. The control arrangement according to claim 7, wherein the PFD is a Flexible AC Transmission System (FACTS) device or a High Voltage DC (HVDC) device.

9. The control arrangement according to claim 8, comprising a Phasor Measurement Unit (PMU) for measuring the second system signal (y₂) at a location of the power system that is remote from the location of the PFD.

10. The control arrangement according to claim 8, wherein the parameter adapter comprises a model estimator for determining a model parameter (mp) of a model of the power system based on the second system signal (y₂), and means for determining the control parameter (cp) from the model parameter (mp).

11. A computer program for controlling power flow and damping electromechanical oscillations in a power system, which computer program is loadable into an internal memory of a digital computer and comprises computer program code means to make, when said program is loaded in said internal memory, the computer execute the functions of the controller according to claim 7.