Document Type

Theses, Ph.D


Available under a Creative Commons Attribution Non-Commercial Share Alike 4.0 International Licence


Electrical and electronic engineering

Publication Details

Submitted to School of Electrical and Electronic Engineering, DIT in Partial Fulfilment of the Requirements of Doctor of Philosophy, June 2015.


Electrical power generation is currently moving towards greater penetration of distribution generation (DG), using multiple small generators instead of fewer and larger units. This can potentially create improvements in efficiency, by allowing use of waste heat (cogeneration). However, it also generates new problems related to control and co-ordination of large numbers of DGs, usually connected across the urban distributed network (UDN). In particular, concerns about security of supply and reliability together with the integration of new energy resources, are presenting a number of new challenges to system operators. One of the major changes that are being observed is the connection of significant levels of generation to the UDN. To accommodate this new type of generation the existing UDN should be utilised and developed in an optimal manner. It is well known that present arrangements for planning, dispatching and protection of central power generators are not directly applicable to the new technology.

This thesis presents a mathematical method that facilitates the large scale integration of CHP generation, as the most common type of DG, connected onto the UDN. A new methodology is developed to determine the optimal allocation and, size of CHP generation capacity with respect to the technical, environmental and economic constraints of the UDN. The method estimates the adverse impact of any particular constraints with respect to the size and location of DG/CHP plants connected into the UDN. Also, the method provides the basis for quantifying the contribution that DG/CHP units makes to the security of energy supply i.e to what extent the particular DG/CHP can reduce the operational performance demand for the UDN facilities and substitute for the network assets. The method is implemented and tested on a 34 busbars network that represents a section of an UDN. The impact of CHP generation on losses in the UDN is also analysed and incorporated into the optimal capacity allocation methodology. The installation of CHP generation is leading to a major change in the way UDNs are designed and operated. UDNs are now used as a media to connect geographically distributed energy generation to the electrical power system, thereby converting what were originally energy supply networks to be used both for distribution and harvesting of energy.

A mathematical model in the form of a Multiple Regression Analysis is presented in order to determine the maximum capacity of CHP generation that may be connected in a given area, while taking account of connection costs as well as technical, environmental, economic and operational setting constraints. Results obtained from various analyses related to the network performance and management are used as data for multiple regression analysis. These analyses include: load flow, fault analysis, environmental and economic analysis. The increased applications of CHP generation presents a substantial challenge to the existing connection policies used to connect CHP plant into UDNs. The section of a typical Irish UDN is used as a case study, and with reference to the available network parameters, the cost and benefits of CHP generations are determined under a number of planning and operational strategies. It is shown that a substantial increase in the net benefits of CHP generation is gained if the appropriate connection method is applied from the start and equally that significant CHP generation connection costs are sustained if ad hoc methods are employed. Connection of CHP generation can profoundly alter the operation of a UDN. Where CHP generation capacity is comparable to or larger than local demand there are likely to be observable impacts on network power flows and voltage regulation. In fact, two major problems to be considered are the voltage levels and operation of protection during faults and disturbances. New connection of CHP generation must be evaluated to identify and quantify any adverse impact on the security and quality of local electricity supplies. There are a number of well-established methods to deal with adverse impacts caused by CHP generation connection into a UDN. While a range of options exist to mitigate adverse impacts, under current commercial arrangements the developer will largely bear the financial responsibility for their implementation. The economic implication can make potential schemes less attractive and in some instances have been an impediment to the development of CHP generation in urban areas. Development of a CHP generation system connection algorithm corresponding to the Least Cost Technically Acceptable (LCTA) method is absolutely vital in order to maximise the penetration of CHP generation into existing UDN with respect to different UDN/CHP system operational settings/constraints and minimal economic implication. In this thesis, results from a number of mitigation methods analysis are compared and used to create the connection process algorithm. This algorithm equally can be applied in the connection process of other distribution generation technologies into existing UDNs.