With recent developments in power systems the demand on alternators to operate in the leading var region at light loads is increasing. With these developments in view, the effect of automatic direct and quadrature axis excitation regulators on the stability of an alternator connected to an infinite bus through a series reactance is investigated. The study is limited to small oscillations, and the stability analysis is done using conventional techniques, such as, the root-locus, the Nyquist, the Routh, and some consideration is also given to state variable methods. A proportionate voltage regulator in conjunction with the field current feedback for the direct-axis excitation regulation is investigated. The limitations and the usefulness of the scheme are discussed. It is mathematically shown that at zero power no direct-axis excitation regulation scheme can extend the steady state reactive absorption beyond a limit de-pending on the quadrature-axis synchronous reactance. On the other hand the quadrature-axis excitation regulation can extend the steady state reactive absorption limit. Out of the various signals theoretically considered for the quadrature-axis excitation regulation the rotor angle signal proves to be the most effective. A proportionate angle regulator on the quadrature-axis acts like a position control servo-system and ideally can extend the steady state reactive absorption limit depending on the transient reactance at all power levels, but the gain range of such a regulator is poor. A proportionate regulator with first and second derivative terms can however increase the reactive absorption limit and the gain range many times compared with a proportionate regulator. Experiments were performed on a model machine in conjunction with simulated regulators to determine the steady state stability limit curves as a function of regulator gain. For some regulators the open-loop frequency response loci were determined from the closed-loop frequency response test for small oscillations. All the experimental and theoretical results show reasonable agreement.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:623064 |
| Date | January 1968 |
| Creators | Kapoor, Satish Chandra |
| Publisher | Imperial College London |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/10044/1/15912 |
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