No Cover Image

Patent 859 views 76 downloads

A new method for integrating and controlling synchronous generators in power systems (GB2012267.7)

Meghdad Fazeli Orcid Logo

Swansea University Author: Meghdad Fazeli Orcid Logo

Abstract

Synchronous generators (SGs) are the most popular type of generators that are used worldwide to generate electricity. There are two main types of SG: round-rotor (also known as turbo-generator) and salient-rotor. The principle of the operation of both types are the same: the rotor is connected to a...

Full description

Published: 2020
URI: https://cronfa.swan.ac.uk/Record/cronfa55112
Tags: Add Tag
No Tags, Be the first to tag this record!
Abstract: Synchronous generators (SGs) are the most popular type of generators that are used worldwide to generate electricity. There are two main types of SG: round-rotor (also known as turbo-generator) and salient-rotor. The principle of the operation of both types are the same: the rotor is connected to a mechanical source of energy, known as the prime mover, and rotates with it. Therefore, the rotating magnetic field (using either electro- or permanent magnet) of the rotor induce a voltage in the stator windings, which is connected to the load/grid. The prime movers for fossil/bio/nuclear fuelled power stations are either steam or gas turbines. SGs also are used as distributed generation units e.g. in CHP plants, where they are called microgenerators. The SGs are even used for renewable systems (e.g. wind), which are not the concern of this patent. The ever-increasing penetration of Power Electronic Converter (PEC)-based generation units (e.g. renewable energy), has been causing numerous challenges for the network operators and has put the power networks on the verge of instability. Some of these challenges, which are due to the intermittent nature of renewable energy, do not depend on the power system structure. For example, as the penetration of renewable energy increases, more energy storage (ES) facilities will be needed to balance the generation with the demand (regardless of the system structure). However, there are some challenges (such as reduction in the short circuit level, phase angle movement, and rate-of-change-of-frequency) that do depend on the system structure. To alleviate these issues the popular approach (in both industry and academia) is to make the PECs behave like SGs. However, this approach is not optimized. For example, a SG can inject between 5-7 pu (per unit) fault current, known as short circuit level (SCL), while that of PEC-based unit is about 1.1-1.2 pu. Therefore, in order to be able to supply similar SCLs by the PEC-based units we must either “de-load” during normal operation or use over-sized power electronics switches. Neither de-loading nor using over-rated switches is an optimized solution and increase the energy price. This patent proposes a “steer into the skid” strategy involving the decoupling of SGs from the network using AC/DC/AC PECs and controlling them such that the PECs impose the power on the SGs according to the local voltage and frequency (virtual AVR and virtual Governor).
College: Faculty of Science and Engineering