Supporting the UK distribution networks with power electronic end user voltage regulation

  • Gordon Watson

Student thesis: Doctoral Thesis

Abstract

As time passes new technologies demanding and generating power will be increasingly connected to distribution networks. Studies found that the capacity of the network cannot support the predicted increase in demand due to current limits on the network. To increase the capacity of the network, raising the voltage level of the system was explored. Studies indicated that raising the voltage level of the UK low voltage (LV) distribution system will significantly increase the capacity of urban distribution networks. The difficulty with this approach is that the end-user receives an unusable voltage supply. Point of use voltage regulation (PUVR) was suggested as a possible way of resolving this difficulty. This also has the additional benefit of maintaining voltage regulation as the LV conductors can essentially be deregulated. Results found that for PUVR to be considered viable the efficiency of the converter units in each home must be a minimum of 93.3% and the cost per unit £460-£2,100. These limits would provide on-par results with traditional network reinforcement. An evaluation of AC-AC converter architectures was undertaken with the cost and efficiency as important selection criteria. Two system architectures were considered: the Back-to-back Inverter and the AC Chopper. After initial evaluation against the selection criteria, the AC Chopper architecture was found to be the cheaper and more efficient architecture and was investigated further. The efficiency results from the practical experiments with the AC Chopper were found to be in line with predicted values from simulation. Efficiency values were found to be as high as 97% validating the simulation results, the voltage distortion was found to be as low as 2.5% with an input voltage distortion of 1.77% and the cost was found to be comparable to network reinforcement. The AC Chopper with auto-transformer hybrid architecture was introduced to increase power quality however the impedance introduced by the autotransformer caused an increase of voltage distortion to 9.5% when a non-linear load was energised. A method of controlled harmonic elimination was found to be more effective, reducing the voltage distortion from 8% to 3% at the cost of increasing current distortion. Therefore PUVR has been demonstrated as a viable alternative to standard network reinforcement because it has the advantages of increasing capacity available without having to re-lay distribution cables. Additionally the losses, power quality and costs are within acceptable margins to be comparable, or better, than standard network reinforcement.
Date of Award18 Sep 2015
Original languageEnglish
Awarding Institution
  • University Of Strathclyde
SponsorsEPSRC (Engineering and Physical Sciences Research Council)
SupervisorStephen Finney (Supervisor) & Derrick Holliday (Supervisor)

Cite this

'