Some Control Applications in Electric Power Systems

Research output: ThesisDoctoral Thesis (compilation)


This thesis presents some control applications in electric power systems. The work consists of the four parts: interaction between DC cables and ship steering autopilots; frequency estimation; computer relaying; field tests using load switching to damp power oscillations.

The first three parts are based on four papers that are given in Appendix A-D. The thesis presents supplementary text to these papers. The last chapter is more self contained and presents field tests from a small hydro power station. These tests show that load switching is an excellent method to damp power oscillations. A proof used in stochastic analysis of fault locators is presented in Appendix E.

The first paper presents novel results on interaction of DC cables and ship steering autopilots. Simulations with a non-linear model show that a ship using steering autopilot with a magnetic compass can be captured by a DC cable, i.e, the ship tracks the cable. A full scale experimental study has been performed at the Kontiskan HVDC link. Good agreement was obtained between measurements and computer sinulations.

The second paper presents a method for frequency estimation in power systems by demodulation of two complex signals.

The third and fourth paper presents some improvements of the differential equation algorithm (DEA) that can be used for transmission line protection. The third paper uses the determinant to explain why isolated estimates from the DEA can be very poor. A median filter is proposed to reject these poor estimates. The fourth paper suggests the followinmg improvements to the DEA: fault classification; intermediate filtering and a new algorithm for three phase faults. Simulation results indicate a nominal operation time of 5-7 ms for three phase faults and slightly longer for other fault types


  • Magnus Akke
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Other Electrical Engineering, Electronic Engineering, Information Engineering


  • load switching., power oscillations, differential equation algorithm, transmission line protection, computer relaying, frequency estimation, DC cable, magnetic compass, Automation, robotics, control engineering, Automatiska system, robotteknik, reglerteknik
Original languageEnglish
Awarding Institution
Supervisors/Assistant supervisor
  • [unknown], [unknown], Supervisor, External person
Award date1997 Apr 11
  • IEA, LTH, Box 118, SE-221 00 Lund, Sweden,
Print ISBNs91-88934-04-7
Publication statusPublished - 1997
Publication categoryResearch

Bibliographic note

Defence details Date: 1997-04-11 Time: 10:15 Place: Room M:B, M-building, Lund Institute of Technology, Sweden External reviewer(s) Name: Phadke, Arun Title: Professor Affiliation: USA ---